Li-O2 batteries have been capturing worldwide attention recently due to their high gravimetric energy density. However, the reaction intermediates, superoxide species generated during oxygen reduction reactions (ORR) were found to be reactive with carbon electrodes and organic electrolytes. Nanoporous gold (NPG) prepared via chemical dealloying has been shown to dramatically improve the reversibility and kinetics of Li-O2 batteries, but high cost prevented it from being used as a practical electrode material. Recently developed electrochemical routines could potentially provide an economic alternative due to their ability to generate very thin NPG layers (<100 nm) and on various low-cost substrates. In this study, we showed that electrochemically synthesized NPG on gold and glassy carbon substrates improved reversibility compared with carbon surfaces. However, since significant amount of ORR products were found on the separator after full discharge, these thin nanoporous structures may need further modification for Li2O2 storage. The feasibility of NPG coated carbon electrode will be discussed.

Advances in energy storage technologies are critical for meeting the ever-increasing demands in power sources for hybrid or electrical vehicles, and in energy storage from fluctuating sources such as wind and solar energy for peak-time use. Among the various high energy density batteries, the non-aqueous Li-O₂ battery has attracted much attention, attributed to its much larger theoretical energy density than the present or future generation Li-ion batteries. However, the performance of Li-O₂ battery is hindered, in part, by the poor understanding of the electrochemical oxidation kinetics of Li₂O₂. In this work, we constructed the solid-state microbattery inside a Transmission Electron Microscope (TEM), consisting of a Multi-walled carbon nanotube (MWCNT)/ Li₂O₂ positive electrode and a Si nanowire negative electrode coated with LiAlSiO_x solid electrolyte. For the first time, we directly observed the process of electrochemical oxidation of Li₂O₂. The oxidation of Li₂O₂ was found to occur preferentially at the MWCNT/Li₂O₂ interface, which suggests that electron transport, not the transport of Li-ions, in Li₂O₂ ultimately limits the oxidation kinetics at high rate or overpotentials. After part of the Li₂O₂ was dissolved and the remaining Li₂O₂ was not in contact with the MWCNTs, the oxidation process slowed down and eventually stopped, due to the loss of electrical contact with the MWCNTs. Our results provide important insights into approaches to design electrodes with enhanced reversibility of the oxygen electrode for rechargeable Li-O₂ batteries.
Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Hybrid Li-air batteries in which the Li anode in a nonaqueous electrolyte is separated by an Li+-ion conducting solid electrolyte from the aqueous air cathode offer several advantages such as stable cell configuration in ambient environment and soluble discharge products in the aqueous catholyte compared to the conventional aprotic Li-air batteries. However, the slow reaction kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) requires efficient bifunctional catalysts with the air electrode. The conventional way to make the bifunctional air electrode is to mix the bifunctional catalyst, conductive carbon, and binder in a solvent to form a uniform slurry or ink, and apply the slurry or ink onto a gas diffusion layer to form a single bifunctional catalyst layer. In order to maximize the three-phase boundary for ORR, hydrophobic catalyzed sites must exist to avoid the flooding of the catalyst. However, three-phase boundary is not needed for OER, and it needs only hydrophilic catalyzed sites to maximize the contact area of the OER catalyst and the catholyte. In addition, high surface area carbon is always present in the catalyst layer as a conductive support, which can undergo corrosion at the high charge voltages with the reactive intermediate species formed during OER, resulting in increased resistance of the catalyst layer, catalyst detachment, and failure of the bifunctional air electrode. Thus, a short cycle life is often encountered in the literature with the hybrid Li-air batteries.
We present here a novel cell configuration in which the ORR and OER electrodes are separated to realize optimized catalytic activity and stability with each electrode in a hybrid Li-air battery. A three-dimensional OER electrode made of mesoporous NiCo2O4 nanoflakes grown on a nickel foam is used as the additional OER electrode, independent of the ORR air electrode made of commercial Pt/C. As each NiCo2O4 nanoflake is grown on the nickel foam current collector, binders and conductive addictives are eliminated on the OER electrode. In addition, the ORR catalyst layer could remain free of corrosion by the highly reactive species produced during OER, thereby enabling a long cycle life of the ORR electrode. Altogether, this novel cell configuration could substantially improve the efficiency and cycle performance of the hybrid Li-air batteries.

Li-air batteries have received a great deal of attention as a potential solution for application in electric vehicles thanks to its high theoretical energy density when compared with existing systems (such as Li-ion batteries). A number of obstacles, however, must be overcome for this to become a reality. In order to achieve this, the design of new catalysts for the oxygen cathode will optimize system performance. In this work we report the high capacities that can be obtained through use of an R-MnO2 nanourchin catalyst.
The R-MnO2 nanourchin catalyst was synthesized by using mild hydrothermal conditions under autogeneous pressure. X-ray powder diffraction (XRD) was used to confirm the formation of single R-MnO2. The microstructure of the obtained nanostructures was investigated by scanning electron microscopy (SEM). This showed the formation of acicular manganese oxide aggregates (5-10 nm wide) which tended to form spherical clusters, taking on an urchin-shaped form of roughly 6 microns diameter.
Electrochemical cycling was carried out in Swagelok TM cells composed of a Li metal anode, electrolyte (0.1M LiClO4 in dimethoxyethane) impregnated into a glass fiber separator and a porous cathode formed by casting a mixture of Super C-65 carbon, the R-MnO2 catalyst, and polytetrafluoroethylene (PTFE) on a stainless steel grid. The cells were sealed after being exposed to an oxygen flux of 1 bar for 30 minutes, storing O2 for the discharge reaction. The electrochemical measurements were carried out with a Biologic cycler.
The reactions taking place at the battery were monitored by means of XRD, SEM and X-ray photoelectron spectroscopy (XPS). The XRD pattern of the post-mortem cathode revealed the formation and accumulation of Li2O2 and Li2CO3. SEM of the pristine electrode showed good R-MnO2 urchin-shaped dispersion across the carbon surface, while discharge products could be found on both surfaces of the post-mortem cathode, as confirmed by XPS. The presence of Li2CO3 on the surface exposed to the mesh is probably caused by the isolation of the formed discharge products after the evaporation of the solvent of the electrolyte, which avoids their re-oxidation and promotes their accumulation.
The high performance of the R-MnO2 “nanourchin” catalyst in an oxygen-electrode have been shown by electrochemical measurements, delivering capacities as high as 4822 mAhgcarbon-1, which significantly exceeds those of conventional cathodes for rechargeable lithium batteries.

Rechargeable non-aqueous Li-Oxygen (or Li-air) batteries have attracted considerable attention in recent years because they can achieve a specific energy much greater than the Li-ion batteries. However, they are also facing problems of large polarization as well as poor cyclability. This is closely related to the cathode passivation during cycles. Many efforts have been made to improve the cyclability including reduction of the depth of discharge (DOD) and introduction of oxygen reaction catalysts. [1-2] However, the key factors limiting the cyclability and the underlying mechanism still need more investigations.
In our work, pristine vertically aligned carbon nanotubes (VACNT) with or without catalysts were used to study their effects on the cyclability of Li-O2 battery.[3,4] Three kinds of electrolytes in different stability were chosen. It was found that the catalysts in the ether-based electrolyte can improve the cyclability obviously. However, in the stabler ionic liquid electrolyte,[5] such effect was not significant. According to results of the linear sweep voltammetry, the catalysts serve as mass transfer promoter instead of conventional electrocatalyts in ether-based electrolytes. In addition, we found that besides DOD the charge cut-off voltage played an important role in the cyclability of Li-O2 battery.[6] Detailed discussions on the relevant mechanisms will be given in the presentation.
References
[1]B. D. McCloskey, R. Scheffler, A. Speidel, D. S. Bethune, R. M. Shelby, A. C. Luntz, J. Am. Chem. Soc. 2011, 133, 18038-18041.
[2]R. Black, J. H. Lee, B. Adams, C. A. Mims, L. F. Nazar, Angew. Chem. Int. Ed. 2012, 52, 392-396.
[3] W. G. Fan, Z. H. Cui, X. X. Guo, J. Phys. Chem. C 2013, 117, 2623-2628.
[4] Z. H. Cui, W. G. Fan, X. X. Guo, J. Power. Sources. 2013, 235, 251-255.
[5] K. Takechi, S. Higashi, F. Mizuno, H. Nishikoori, H. Iba, T. Shiga, ECS Electrochem. Lett. 2012, 1, A27-A29.
[6] X. X. Guo, N. Zhao, Adv. Energy Mater. 2013, DOI: 10.1002/aenm.201300432.

Li Air batteries have some of the highest theoretical specific energies in the energy-storage technology field. There are, however, several factors that decrease this specific energy in practice. An anode protective barrier film described here aims at eliminating such factors as Li dendrite growth and oxygen/water based degradation of the lithium metal. We utilize layer-by-layer (LbL) film deposition technology to prepare composite films consisting of poly(ethylene oxide) (PEO) and graphene oxide (GO). The PEO component is incorporated to provide a lithium ion conduction path. The GO component is incorporated to impart barrier properties, which arise from the tortuous path created by the overlapping GO sheets. A third and essential component is a PEO-functionalized silane. These silanes cross-link the LbL structure through siloxane-bond formation. The resulting network imparts mechanical and chemical stability, as wells as improved resistance to moisture and gas permeability and lithium dendrite growth. The cross-link density is varied to achieve optimal barrier properties, while maintaining low sheet resistance.

Non-aqueous lithium-air batteries have been estimated to deliver gravimetric energy three to four times that of conventional lithium-ion batteries at comparable gravimetric power (1,2). Fundamentally understanding reaction mechanisms and associated intermediates during lithium-O2 cell operation is critical for implementing practical lithium-air batteries with high reversibility and long cycle life. In particular, the superoxide reaction intermediate generated during the oxygen reduction reaction (ORR) is known to be potentially chemically unstable against the electrolyte solvent (3), reaction surface (4) and cell components (5), leading to high overpotentials during charge, and short cycle life. We used the rotating ring disk electrode (RRDE) technique to probe the influence of different electrolyte solvents on the detection of the superoxide intermediate generated on planar glassy carbon and Au electrodes in several organic electrolytes. The fraction of ORR charge on the disk detected from superoxide oxidation on the ring was found to exhibit a solvent-invariant potential dependence on carbon but not on Au, where this fraction was highly dependent on the solvent chosen. These results yield insights into potential criteria for highly reversible lithium-oxygen cell configurations, and have implications for the growth mechanisms and surface chemistries of the Li2O2 discharge product.
References
1. Bruce, Peter G et al. Nature Materials 11.1 (2012)
2. Lu, Yi-Chun et al. Energy & Environmental Science 6.3 (2013)
3. Freunberger, Stefan A et al. Journal of the American Chemical Society 133.20 (2011)
4. McCloskey, B. D. et al. The Journal of Physical Chemistry Letters (2012)
5. Younesi, Reza et al. The Journal of Physical Chemistry C (2012)

Here we report a thin and mechanically strong energy storage device using cellulose as the base substrate extracted from Cladophora C. aegagropila algae, coated with electrically conductive polymer (ECP) polypyrrole (PPy) and atomically thin graphene. The cyclic voltammetry (CV) data exhibits a supercapacitive behavior of the device. Based on the active mass of the electrode for CV analysis, we observed that the cellulose/PPy/graphene electrode exhibits a specific capacitance of 560 fg-1. The device demonstrates a hybrid characteristic in which graphene behaves as an electrochemical double layer capacitor (EDLC) and PPy as a pseudo-capacitor. The initial potential of the device when connected with the multimeter was observed to be 250 mV. The device shows better energy density, higher charge discharge cycles, and lower self discharge rate. TEM and SEM images reveal an interesting “necklace” beaded structure with individual bead diameter of approximately 1 mu;m. The bead formation is from the polysorbate surfactant which is used for better graphene dispersion. We observe that the bead formation starts to break up upon increasing the graphene concentration.

Vertically-oriented graphene (VG) is a class of networks consisted of stacked two-dimensional graphene nanosheets that are typically oriented vertically on a substrate. Compared with the graphene prepared by chemical method, i.e., reduction of graphene oxide (GO) produced by the modified Hummer&’s method, VG nanosheets normally synthesized by plasma-enhanced chemical vapor deposition (PECVD) techniques own the unique features of non-agglomerated morphology, high surface area, and sharp exposed graphene edges. [1] Until now, we have successfully demonstrated the energy applications of VG in the fields of supercapacitors (as active materials) and direct methanol fuel cells (as catalyst support for methanol oxidation reaction ). [2, 3] For VG based supercapacitors, the vertical direction and exposed edge planes of graphene sheets could favor the ion accessibility, and meanwhile, benefit the electron transfer rate due to the significantly higher in-plane electrical conductivity of graphene compared with its out-of-plane electrical conductivity. On the other hand, VG nanosheets with predominantly edge plane structure exhibiting dense open graphitic edge planes can desirably provide a considerable number of nuclei sites for the fast nucleation and well dispersion of catalyst nanoparticles for enhanced catalytic performance.
[1] Zheng Bo, et al., 2013, Plasma-enhance chemical vapor deposition synthesis of vertically oriented graphene. Nanoscale. 5, 5180-5204. Review article
[2] Zheng Bo, et al., 2012, One-step fabrication and capacitive behavior of supercapacitor electrodes using vertically-oriented graphene directly grown on metal,Carbon, 50, 4379-4387.
[3] Zheng Bo, et al., 2013, Highly-branched vertically-oriented graphene with dense open graphitic edge planes as Pt support for methanol oxidation, Journal of Power Sources, submitted.

The intense interest in graphene for electrochemical energy storage is encouraging the community to re-examine two-dimensional (2D) layered materials for both fundamental studies and potential applications. A large family of layered materials in which atoms within each layer are held together by covalent bonds, while the layers are weakly bonded together by van der Waals interactions, has been known for many years. The ability of these 2D layered materials to support fast ion transport of lithium and sodium ions is well established as the electrochemical properties of several transition metal oxides and transition metal dichalcogenides in bulk form were determined in the 1970&’s and 80&’s. However, there are very few instances where single or few-layered nanosheets, which can now be prepared through various exfoliation methods, have been reported.
In our research, we have been synthesizing layered materials by either direct synthesis in solution or bulk-exfoliation. The materials with well-established van der Waals gaps (TiS₂, MoS₂ and WS₂) are prepared by direct synthesis in solution while oxides with distinct 2D character (non-stoichiometric forms of TiO₂, Nb₆O₁₇, and TiNbO₅) are synthesized into single or few-layer materials by exfoliation. Moreover, there is considerable versatility in the synthesis as we are able to prepare 2D nanosheets directly on graphene and to assemble sheet structures into 3D stacks. We have observed instances where the electrochemical properties of 2D materials differ from those of the corresponding bulk material. Nanosheets of Nb₆O₁₇ readily intercalate lithium while the bulk materials exhibit little activity. The 2D materials also exhibit faster redox kinetics. While the re-examination of 2D layered materials is just starting, it is likely that single layer 2D materials will exhibit interesting electrochemical properties. The combination of having high surface area, accessible redox-active constituents and, for some systems, high electrical conductivity, suggests that these materials have considerable promise for energy storage.

Organic radical batteries (ORBs) comprise a relatively new technology that use cathodes based on stable organic radical-based polymers. Polymeric organic nitroxide radical materials, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), have received great interest for various energy storage applications. These materials are readily synthesized from environmentally benign precursors, and TEMPO in particular has been shown to have very fast charge transfer kinetics. These materials show great promise as cathode materials because the neutral, radical species are remarkably stable, and the one-electron oxidation is fully reversible.
In order to guide the development of new organic radical electrode materials and to aid in the design of improved electrode structures, a detailed understanding of the fundamental mechanisms involved in electronic charge transfer and anion interfacial mobility in the polymer matrix is required. This work has focused on ab initio electronic structure calculations and large-scale molecular dynamics (MD) simulations. These theoretical predictions are compared to AC impedance experimental measurements to establish a detailed understanding of the fundamental mechanisms involved in electronic charge transfer and ionic motion within the TEMPO matrix. Electronic structure calculations were conducted on subunits of interest to relate oxidation states to in situ spectroscopic monitoring of oxidation and ion pairing.
Polymeric TEMPO morphologies have been generated using atomistic MD simulations with force fields adapted to radicals for neutral and ionic systems generated during charge/discharge of the test cells. Morphological features dictated by polymer structural properties, including nitroxide radical density and molecular anion type, have been correlated with experimental results, and multiple iterative modifications of the theory-experiment results have been completed. We will describe the implications of these simulations to understanding barriers to charge migration and transport.

Electrical components used in automobiles are driven by battery, which itself is charged by the engine. This puts extra load on the engine, as a result of which the efficiency of the engine is compromised. Piezoelectric materials convert all kinds of mechanical as well as vibrational form of energies into electrical energy. We propose the use of PZT (Lead Zirconium Titanate) based nanogenerators to harness the vibrational energy of the vehicle and use it for its electrical components. Since PZT is known to have the maximum piezoelectric coefficient; the deciding factor of conversion of energy from mechanical to the electrical, it is best suited for high energy conversion efficiency. Here we present fabrication and characterization of two different morphologies of PZT, thin film and aligned nanowires, which possess special properties of piezoelectricity. Extensive characterizations such as SEM, uv-vis spectroscopy to tune the size and shape of synthesized thin films and nanowires will be presented.

Different Lithium-Air cathode structures have been investigated in order to determine whether nano-structuring of graphene nanoplatelets could be useful in Lithium-Air batteries. Conventional Lithium-Air cathode structures are fabricated by coating slurry of carbon or graphitic material on a stainless steel mesh or nickel foam. Slurry coating on metal mesh is difficult as the material often passes through the grid openings instead of forming a uniform film, especially if the particle size is too small. Slurry coating on metal foam is performed by immersion into a slurry, sonication and subsequent thermal processing. Control of the amount of slurry that penetrates the metal foam structure and its relation to sonication and immersion time is difficult. Also, Nickel foam is reactive. Paper-like electrodes offer the potential to tailor electrode parameters such as thickness, internal and external surface area, porosity and the amount of material that goes into an electrode. One potential drawback of the porous materials is associated with the clogging of the pore orifice by the reaction products. Graphene Nanoplatelets (GnPs) with a large external surface area, no internal porosity and chemical inertness have the potential to offer an alternative to porous materials. GnP paper could be prepared with relatively low surface area, large particle size material but not with the high surface area, small particle size material. It was found through microscopy that the high surface area GnP has almost spherical aggregate morphology. The lack of aspect ratio in the particles limits the ability to hold together in the form of a paper compared to the low surface area platelet shaped material. An innovative bilayer hybrid paper structure has been developed which allows relatively high surface area material to be incorporated into a paper structure fabricated with relatively low surface area material. The bilayer hybrid paper exhibits much improved performance compared to the un-hybridized low surface area paper structure with equivalent parameters. The improvement is most likely caused by a net surface area gain in the paper electrode by the incorporation of higher surface area material. The normalized discharge performance with respect to electrode loading is low compared to conventional porous, high surface area carbon black based materials. However, most carbon black based materials have surface areas in the range of several thousand square meters per gram that consists of both micro and macro porosity. Through hybridization of GnPs of different surface areas and morphologies, Lithium-Air cathodes with enhanced performance are possible.

We present a novel technique using microwave irradiation method to synthesize a graphene-nanotube-iron three-dimensional (G-CNT-Fe 3D) nanostructure as an anode material in lithium-ion batteries. To obtain the G-CNT-Fe 3D nanostructure, a novel and convenient two-step process was developed by exposing the mixture of ferrocene, azodicarbonamide (ADC) and expandable graphite oxide to the multiple microwave irradiation cycles. The initial anchoring of iron nanoparticles occurs on graphene sheets. Next, 1st big CNTs are grown through the first microwave irradiation. The formation of carbon nanotubes is initiated from the decomposition of ferrocene vapor under microwave irradiation, resulting in the generation of catalyst particles and release of hydrocarbon fragments. The iron particles formed by collision processes are anchored on graphene surfaces and induce the growth of CNTs. When the microwave radiation is turned off, the cooled ferrocene vapor attaches to the 3D nanostructure, and much smaller 2nd CNTs are grown on the 3D nanostructure under the second microwave irradiation forming G-CNT-Fe 3D nanostructure. Finally, the nanostructure composes vertically aligned 1st big CNTs grown directly on graphene sheets along with shorter 2nd CNTs stemming out from both the graphene sheets and the vertically aligned 1st big CNTs.
We have combined CNT, Fe2O3 and graphene into a single structure, which prevents restacking of the graphene planes due to the CNT spacers and strongly anchors the iron nanoparticles to the graphene and CNT planes, and improves the utilization of the iron particles during the charge/discharge process. The resulting high surface area electrode structure enables greater number of Li-ions to be inserted and stored. Specific capacities of 1024 mAh/g after 45cycles along with a Coulombic efficiency in excess of 99% which makes it a promising material for Li-ion battery applications.
In summary, we have developed a fast and convenient microwave method to synthesize a novel G-CNT-Fe 3D functional nanostructure composed of 1st big CNTs grown on graphene sheets and much smaller 2nd CNTs grown again on both the 1st big CNTs and on the graphene sheets. This microwave irradiation method is very attractive for large-scale synthesis of such unique 3D nanostructure. In addition, functional 0D iron nanoparticles are embedded in the network creating a unique 3D ensemble of 0D iron nanoparticles distributed on 1D carbon nanotubes and 2D graphene nanosheets. The obtained G-CNT-Fe 3D nanostructure showed very high lithium storage capacity significantly above that of its individual components indicating a strong synergy between the graphene, CNT, and iron oxide phases in the structure.

Iron oxyfluoride (FeOxF2-x/C) nanocomposites undergo a conversion reaction upon lithiation/delithiation processes and provide high energy density as more than one electron transfer is occurring during conversion. At the present time, the phase changes occurring during charge and discharge processes of these positive electrodes are not fully understood. In this study, the structural changes of FeOxF2-x/C during the first charge-discharge cycle at 60°C were studied by combined high resolution transmission electron microscopy (HRTEM) imaging and selected area electron diffraction (SAED), electron energy loss spectroscopy (EELS) techniques and also in-situ x-ray absorption spectroscopy (XAS). EELS (using the Fe-L edges) and XAS (using the Fe-K edge) were utilized to determined nanometer changes of Fe valance state during lithiation/delithiation.
The results of this investigation show that conversion reaction path during 1st lithiation is very different than the re-conversion path during 1st delithiation. During lithiation, intercalation is first observed followed by conversion into a lithiated rocksalt (Li-Fe-O-F) structure, metallic Fe and LiF phases. During delithiation, the rocksalt phase does not disappeared, but co-exists with the amorphous (rutile type) phase formed by the reaction of LiF and Fe up to the end of delithiation. However, a de-intercalation stage is still observed at the end of reconversion similar to a single phase process despite the coexistence of these two (rocksalt and amorphous) phases.

Transition metal sulfides have drawn much attention because of their promising properties for a wide range of applications. They are also regarded as potentially feasible electrode materials for lithium batteries. Nowadays the battery technology is often criticized for its slow development. The achievement of higher energy density has become one of the most important issues in the development of new Li-ion battery technologies. As a result, the increasing demands for lighter and thinner Li-ion batteries with higher capacity continue to boost ongoing researches on electrode materials with superior properties to that of the-state-of-the-art. Nanosized transition metal sulfides with layered structure can provide high specific capacity, good cycling stability and superior rate capability, which may meet the increasing desires for new lithium battery technologies.
Herein, we have prepared graphene-attached VS₄ nanorods and graphene-attached WS₂ nanosheets by simple hydrothermal reactions, respectively. Both of VS₄-graphene and WS₂-graphene nanocomposite electrodes exhibited good cycling stability and impressive high-rate capability of lithium storage. VS₄-graphene delivered a reversible capacity of 727 mAh/g after 50 cycles in the voltage range of 0-3 V at a high current rate of 4 A/g. Besides, comparable capacity of 630 and 314 mAh/g can still be maintained when cycling at even higher rates of 10 and 20 A/g. In addition, the mechanism of Li storage of VS₄ was also systematically studied for the first time, and a conversion reaction mechanism with irreversible phase change during the initial discharge-charge process was proposed. Graphene-attached WS₂ nanosheets also showed good electrochemical performance when tested in half-cell. A reversible capacity of 647 mAh/g can be maintained after 80 cycles at a current density of 0.35 A/g, and high capacity of 531 and 287 mAh/g can still be maintained when cycling at even higher rates of 7 and 14 A/g, respectively. Such outstanding electrochemical performance could mainly be attributed to the existence of graphene, which improved both the conductivity and stability of the electrodes.
In summary, VS₄-graphene and WS₂-graphene nanocomposites were prepared by simple hydrothermal methods, and showed good cycling stability and impressive high-rate capability of lithium storage.

Li-ion batteries have conquered the market for energy storage and applications, but still new advances should be made so that this technology can continue to play a key role in the future. The most praised cathode materials for Li-ion batteries are either layered ones (NMC compounds), or LiFePO4 (or derivatives).
Polyanionic electrode materials offer a compelling combination of safety benefits and tunable redox potentials. Thus far, phosphate-based phases have drawn the most interest with a subsequent surge of activity focused on the newly discovered family of fluorosulfate phases: tavorite and triplite which present Fe3+/Fe2+ redox potentials of 3.6 and 3.9V vs Li+/Li, respectively.
We will present here our strategy and results on fluorine-free sulfates: 1) a new family of 3d-metal hydroxysulfates of general formula LiMSO4OH (M=Fe, Co, and Mn) among which LiFeSO4OH reversibly releases 0.7 Li+ at an average potential of 3.6 V vs. Li+/Li0. LiCoSO4OH shows some redox activity at 4.7 V vs. Li+/Li0. Besides, these compounds can be easily made at temperatures near 200°C via a synthesis process that enlists a new intermediate phase of composition M3(SO4)2(OH)2 (M= Fe, Co, Mn, and Ni); related to the mineral caminite. Structurally, LiFeSO4OH appears to be a layered phase unlike the previously reported 3.2 V tavorite LiFeSO4OH. This work should provide an impetus to experimentalists for designing better electrolytes to fully tap the capacity of high voltage Co-based hydroxysulfates, and to theorists for providing a means to predict the electrochemical redox activity of two polymorphs.

Conversion materials such as FeOF have higher capacity than conventional intercalation cathode materials because at full conversion, all the valence states of Fe are used corresponding to a maximum of three electrons transfer. However, conversion reactions involve as series of complex structural and chemical phase changes which at present are not fully understood. In this study we studied the phase transformation of FeOxFy thin films induced by atomic Li deposition, In order to produce FeOF, FeF2 thin films were first deposited on holy carbon support films followed by oxidation to form FeOxFy thin films. These FeOxFy thin films were subsequently lithiated with atomic Li and studied by combined annular dark field (ADF) STEM, electron energy loss spectroscopy (EELS), for chemical and valence analysis, and selected area electron diffraction (SAED) techniques. Simulations of SAED patterns for nanoparticles in the 2-4 nm range were obtained ab-initio using JEMS program. It was found that varying degrees of lithiation had occurred and the extent of phase transformation was determined based on observed structure, Li content and Fe valence state. During lithiation, transformations from rutile to monoclinic to rocksalt structures have been observed as a function of Li content. These phase changes are compared to those observed during electrochemical lithiation.

Next-generation electrochemical devices would require high-energy, high-power density to bridge the gap between battery and capacitors. Traditional electrode design processes such as doctor-blading allow limited control over the electrode composition and structure at the nanoscale, and insulating binder materials limit device performance. To overcome these challenges, we have engineered a route for the synthesis of highly stable, sub-8nm TiO2 nanoparticles that can be incorporated directly into composite films with acid-functionalized multi-walled carbon nanotubes (MWNTs). Using electrostatic layer-by-layer nanofabrication, we assembled binder-free hybrid electrodes of TiO2/MWNT to obtain a synergistic effect from the high electronic conductivity and excellent charge storage capacity. These thin film electrodes with highly controllable thicknesses show well developed mesopores with finely dispersed, non-agglomerated TiO2 nanoparticles on MWNTs. Electrochemical measurements show high charge storage capacity (>150 mAh/g electrode at 0.1 A/g) with excellent cycling stability during charging and discharging up to 200 cycles. Our study shows that rational design of electrodes with novel materials and architectures can achieve promising performance levels for thin-film electrodes in energy storage applications.

We present extensive calculations on the lithiation of amorphous Silicon. Structures at different lithiation levels are created using first-principles methods. We investigate the short-range and medium-range properties using ring statistics and Voronoi-Delaunay type methods. We also explore the reaction front formed during the lithiation of amorphous Silicon, and calculate the reaction barriers for the intercalation of Lithium into amorphous Silicon, and its diffusion in the bulk. These results give us important information about the formation and propagation of the reaction front.

Titania nanoparticles (TNPs) have been one of the most useful material in various fields especially in energy applications such as photo-catalyst, solar cells and Li ion battery (LIB). Among these, TNPs as the anode material for LIB have been attracting much interest due to their characteristics of safety, stability, and rapid charge/discharge property. Although the size of nanoparticles was expected to be very important factor to the whole cell property because of the different surface area, contact with electrolyte, ion diffusion length, etc., the size effect of TNPs in the LIB has been rarely reported owing to the synthetic difficulty of preparing various sized TNPs from the same synthetic method, especially for TNPs with the size smaller than 200 nm.
Here we report the simple synthetic method of spherical TNPs with various diameters from about 60 nm to 300 nm. Size of TNPs was controlled mainly by the amount of water or titanium source. Smaller TNPs seem to have the larger Li ion capacity than bigger TNPs because of larger surface area and presence of mesopore in each particle. In case of TNPs bigger than 150 nm, low initial capacity of Li ion was increased over the repeated cycles probably due to the increment of the actual active sites, which was supported by cyclovoltammetry measurement. Using the 60 nm TNPs, high rate of Li ion storage (130 mAh/g at 10 C) was obtained with ultra-stability. Details on the synthesis and measurements of electric property of TNPs will be discussed.

Up to now, commercialized lithium-ion batteries (LIBs) have used LiCoO2 cathode and graphite (carbonaceous materials anode. However, they do not meet high-power and high-energy density applications, like hybrid-electric vehicles (HEVs), EVs, and energy storage systems. In Particular, carbon-based anodes must replace new materials including transition metal oxide (MxOy, M=Fe, Co, Ni, Mn, Cu, etc.) and group IV elements (Si, Ge, Sn, Sb, etc.) because of its low theoretical capacity (LiC6, theoretical capacity: 372 mAh g-1).
Among the metal oxides, CuO is an attractive material because of its abundance, low cost, chemical stability, high theoretical capacity (672 mAh g-1) and friendliness. However, micron-sized CuO is hard to be used as anode materials due to its low conductivity, high irreversible capacity and large volume expansion during charge/discharge cycles. Several strategies to overcome its drawbacks have been developed, such as combination of conductive materials and control of morphology, and direct attachment of CuO on current collector.
Herein, we provide a simple and massive synthetic route for producing various CuO nanostructures. Firstly, we synthesized mesoporous CuO particles which are networked with MWCNTs. The method can not only make massive production, but also increase electrical conductivity of CuO by chemically bonding on the surfaces of MWCNTs. As results, we achieved excellent electrical performance of CuO/MWCNTs in cycle retention (close to theoretical capacity at 100 cycles) and rate capability (without capacity decrease until 5 C rate) in LIBs. Secondly, we prepared CuO nanotubes by combining hydrothermal reaction (for Cu nanowires) and the Kirkendall effect (for CuO nanotubes). Cu nanowires were synthesized by a simple hydrothermal reaction using CuCl2 and amine based surfactants, and subsequently, they were spin-coated on current collector. During thermal annealing process, the Cu nanowires were converted to CuO nanotubes that were strongly attached to the current collector. Binder-free and conductive material-free CuO nanotube anodes showed a high reversible capacity (>550 mAh g-1) and a remarkable rate capability. These two methods open up a way to extend other metal oxide anodes in practical LIB applications.

Double core-shell particles of Fe_0.82Si₂@Si@graphene are synthesized by the self-assembly between negatively-charged Fe₃O₄@SiO₂ core-shell nanoparticles and positively-charged graphene oxide modified with polycations, which is followed by the magnesiothermic reduction at elevated temperature. The formation of nanosized double core-shell material of Fe_0.82Si₂@Si@graphene is confirmed by powder X-ray diffraction and high resolution transmission electron microscopy. The obtained double core-shell material of Fe_0.82Si₂@Si@graphene shows promising anode performance for lithium ion batteries with large capacity, excellent cyclability, and rate capability, which are much superior to those of pure Si particle and Fe_0.82Si₂@Si core-shell particle. In the present double core-shell particle, the Fe_0.82Si₂ core acts as a robust skeleton to alleviate the severe volume expansion/contraction of silicon during lithiation/delithiation process. Additionally, the external shell of graphene plays a role not only as an expandable matrix to prevent the pulverization of silicon electrode during cycling but also as an electron pathway connecting to current collector. This work highlights that the self-assembly between Si-containing core-shell particles and graphene nanosheets can provide powerful way to design and explore highly efficient electrode materials for lithium ion batteries through the stabilization of silicon particles during repeated electrochemical cycling.

Graphene, a single layer of carbon atoms patterned in a hexagonal lattice, has unusual characteristics, including outstanding electronic properties, thermal conductivity, optical properties, high mechanical strength, and large surface areas. Due to these unique properties, has attracted great attention all over the world for its potential applications in sensors, catalysis, energy-storage devices, and environmental fields due to the excellent mechanical, electronic, and thermal properties. Most previous research has focused on two-dimensional (2-D) constructs. However, to take full advantage of graphene&’s superior physical and electronic properties, large surface area, and chemical functionality, 2-D graphene sheets must be integrated into macroscopic three-dimensional (3-D) structures.
Herein, we report a self-assembled 3-D architecture of metal oxide-reduced graphene oxide (RGO) interfacially anchored metal oxide concept consisting of an electrochemically active material (SnO2) sandwiched between highly conductive RGO structures. We used simple and mild method to synthesize SnO2 nanoparticles sandwiched between RGO sheets was by one-pot synthesis. Further, the synthesized 3-D SnO2/graphene architecture was used as a binder-free anode electrode for Li-ion battery to conduct an electrochemical assessment.
More details on the synthetic procedure and structural properties will be presented at the meeting.

Three dimensional (3D) square pyramidal-type nanosized RuO2 were successfully deposited directly on 304L stainless steel (SS304L) by chemical vapor deposition (CVD) at 400 °C without applying any catalysts. This growth method provides efficient charge transport and no need for polymer binder and conductive carbon. A simple hot-walled horizontal CVD setup was utilized and ruthenocene, Ru(C5H5)2 was the starting precursor. The as-prepared materials were characterized by powder X-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM). Galvanostatic charge-discharge experiments were carried out versus Li-metal and an unusually large first discharge capacity, 3260 mAh g-1, which is 9 times higher the capacity of graphite (372 mAh g-1), was obtained upon deep discharging to 0.1 V. The second discharge capacity yields 3100 mAh g-1. However, the reaction mechanism of the first cycle and subsequent cycles is different. Ex-situ FESEM after 20 cycles revealed that the in-situ formation of RuO2 yield particle size < 5 nm and powder XRD showed the RuO2 is amorphous.
Directly growing RuO2 on the current collector allows us to obtain 20 cycles even after cracking due to volume expansion. 3D square pyramidal-type RuO2 provides large surface areas, finite lateral sizes, and enhanced open-edge morphologies suitable for enormous Li-storage. Overall, direct deposition of RuO2 on SS304L by CVD plays a dominant role in allowing the materials to store excess lithium. A completely different mechanism is observed when cycling RuO2 with similar morphology from 4 to 1 V and both mechanisms will be discussed.

As energy storage devices, demand for rechargeable lithium ion batteries (LIBs) have rapidly increased due to their high energy capability. Recently, Metal oxides have been suggested as alternative anode materials due to their higher specific capacity comparing with graphite. However, some of metal oxide based anodes show the high operating voltage and poor cycle life.
Recent studies have shown that ZnMn2O4 exhibits high specific capacity, low operating voltage (1.3-1.5 V for lithium extraction) and good cyclability. In the case of ZnMn2O4 can reversibly store Li ions through conversion reaction of metal oxide (ZnO and MnO) and alloy/dealloy reaction of Zn with Li. In particular, there have been sturdies on fabrication of nano-sized ZnMn2O4 to increase the surface area and decrease the length of Li ion diffusion path. However, maintaining the electrical conductivity of ZnMn2O4 electrode is a very important due to their intrinsically low conductivity and aggregation during the cycling process, as well as synthesis of nano-sized particle.
In this study, we report on the fabrication and electrochemical characterization of the ZnMn2O4/RGO nanocomposites using the MnO2/RGO nanocomposites. It is believed that composite with high electrically conductive RGO can provide an electron path to ZnMn2O4 and prevent the aggregation of nano-ZnMn2O4 during the cycling process. More details on the synthesis and electrochemical properties of ZnMn2O4/RGO nanocomposites will be presented at the meeting.

In lithium ion batteries, Si-based anodes possess the highest specific capacity from four to 10 times greater than graphite [1,2]. However, up to 400% volume expansion of Si during lithiation results in anode pulverization due to mechanical stresses. The goal is to develop a silicon-based anode that can withstand lithiation-delithiation cycles without mechanical degradation. The major steps including silica synthesis, polymer templating, and magnesium vapor reduction will be discussed.
To avoid mechanical degradation of silicon, the critical value of the silicon particle size/wall thickness should be below the required threshold of <50nm [3,4]. Thus, it is crucial to maintain the silicon particle size in this range. The second major requirement for silicon anode in lithium ion batteries is to have the second conductive phase, e.g. graphite or graphene, in the form of a flexible coating that can withstand lithiation-delithiation without deterioration of the carbon phase.
Two types of silicon oxide precursor materials that meet these requirements have been evaluated, among them hollow silica microspheres from 3M and silica aerogel from Aspen Aerogels. Preparation of Si precursor materials has been performed by (1) Mixing with resorcinol-formaldehyde (RF) monomer solution; (2) Performing magnesium reduction; and (3) Removal of unnecessary impurities such as magnesium oxide by washing the material in 0.1M HCl.
The SEM, TEM, EDS, cyclic voltammetry performance, cycleability, charge-discharge profiles, and XRD patterns after different number of lithiation-delithiation cycles will be discussed.
[1] A. Kraytsberg, Y. Ein-Eli, J. of Power Sources, 196, 886 (2011).
[2] W. J. Zhang, J. of Power Sources, 196, 13 (2011).
[3] X. H. Liu, L. Zhong , S. Huang, S. X. Mao, T. Zhu, J. Y. Huang, ACS Nano, 6, 1522 (2012).
[4] U. Kasavajjula, C. S. Wang, A. J. Appleby, J. of Power Sources, 163, 1003 (2007).

CuAg₃S₂ (Jalpaite) is a naturally occurring mineral that has been well structurally characterized. Its crystallizes with the tetragonal space group I41/amd (No. 141) at room temperature. The lithium analogs CuLi₃S₂ which may exhibit interesting properties as potential candidate for Li-ion battery cathode can be obtained through solid state synthesis. Cubic CuQ₂ (Q = S, Se) is an interesting precursor from a structural standpoint due to the amount of potential sites for lithium insertion. However, this phase is difficult to capture using conventional high temperature solid state synthesis. We present a facile annealing of mechanical alloying process which results in single phase product of Cu_(4-x)Li_(x) S₂. The synthesized CuLi₃S₂ compound is structurally characterized using powder X-ray diffraction (PXRD) and Rietveld refinement. Its electrochemical performance was evaluated through cyclic voltammetry and cycling measurements. Structural change at various potentials was assessed using ex-situ PXRD scans.

Lithium nickel manganese oxides (LNMO, {Lix}[LiyNinMnm]O2, (x le;1, y le; 1/3, (y + n + m) le; 1)) are considered as attractive cathode materials for 5 V lithium ion batteries. There have been a lot of studies on synthesis and characterization of LNMO materials. The common synthetic approaches are the hydrothermal methods. So far, however, it is still challenging to achieve LNMO nanostructures with controlled morphology, structure and composition, which eventually determine their electrochemical performance.. Laser irradiation in liquids (LIL), featured by laser irradiating liquid precursors, from which nanostructures can be produced through photochemical and/or photothermal effects generated by the strong interaction between the laser beam and solution. Due to the non- equilibrium growth conditions, complex nanostructures are expected. We synthesize LNMO nanostructures by using LIL method, where a high power nanosecond pulsed laser was employed to irradiate an aqueous solution of lithium nitrate, nickel nitrate and manganese nitrate. Nanorods and nanoflakes have been achieved. The composition of LNMO can be controlled by simply changing the ion concentration and ratio in the growth solution. In addition, other nanostructures, such as carbon/LNMO nanocomposites, have also been synthesized. The as-synthesized LNMO nanostructures and carbon/LNMO have been tested as the cathode materials of lithium ion batteries. Our approach can be used to fabricate many other complex nanostructures by controlling the chemical environments and laser parameters.

We performed TEM experiments at Materials Science Division and National Center for Electron Microscopy (NCEM) of the Lawrence Berkeley National Laboratory, which is supported by the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231. We thank the funding support from U.S. DOE Office of Science Early Career Research Program.

Although Li ion battery is widely used in these days at various portable devices, it needs enhanced performance in energy density for using in electric vehicle or Energy Storage System. Development of cathode materials to enhance energy density is one of the most interests in research of Li ion battery. In this aspect, metal fluorides as cathode materials have several advantage over other materials because they can achieve large capacity from conversion reaction which uses all available oxidation site of metal during lithiation/delithiation and have reasonably high potential leading to high energy density. [1] However, full utilization of this high energy density is limited because massive structural changes related to conversion reaction make kinetics sluggish leading to large polarization during charging/discharging. To enhance reaction kinetics in conversion reaction materials, nanosized particles are much preferred because they have high reactivity and much easily accommodate structural change. Metal fluorides nanocomposites with carbonaceous materials have been developed by using mechanical high-energy ball milling or by using the precipitation of nanosized particles in strong acidic condition such as HF solution. [2,3]However, these synthetic processes have their own limitations such as extendability or safety issues. To further utilize metal fluoride materials simple process to synthesize nanosized metal fluorides should be developed.
In this talk, we will discuss about how to develop fast single-step solid state reaction to obtain nanosized metal fluorides. Especially, FeF3 as a model material has been focused due to its high theoretical capacity above 700mAh/g. The developed process easily leads to nanosized FeF3 particles with good crystallinity. Also, we will present the electrochemical properties of the nanosized FeF3 particles synthesized by the developed process.
Reference
[1] G.G. Amatucci, N. Pereira, Journal of Fluorine Chemistry 128 (2007) 243 .
[2] M. Bervas, G. G. Amatucci, Journal of electrochemical society, 153 (2006) A799 - A808.
[3] A. Basa, F. Garcia-Alvarado, Journal of Power Sources, 197 (2012) 260-266.

In the recent year, lithium manganese oxide, LiMn₂O₄ has been in the spotlight as promising alternative to LiCoO₂ in the view point of performances as well as cost. Nevertheless, LiMn₂O₄ still has a problem to be solved; severe capacity fading upon extended electrochemical cycling, especially at elevated temperature, which induced by Mn²⁺ dissolution and Jahn-Teller distortion. Poor cycling behavior can be enhanced by partial cationic substitution (increase average oxidation state of Mn ion above 3.5+) and surface coating method. However, these methods bring out the reduction in capacity with increasing doping and coating level, also thicker coating layer acts as insulator which increases the cell resistance.
In this work, a novel concept is presented for developing new high capacity and high stability LiMn₂O₄ spinel by controlling atomic structures and oxidation states of Mn-ion through the partial cationic substitution at the surface.
Based on STEM analysis, we confirmed coating layers grew epitaxially from the stoichiometric LiMn₂O₄ sharing the cubic closed packed oxygen crystal axis. But the product exhibited hierarchical atomic structure (A and B site disordering at AB₂X₄ spinel structure) in CCP oxygen array at the particle surfaces while core structures were maintained as Fd3/m spinel. This cathode having a hierarchical atomic structure exhibited the initial discharge capacity over ~120mAh/g with the coulombic efficiency of >99% and 85% retention after 100th cycles at 60°C. More detailed results will be discussed at the meeting.

Recent research has focused on the Li-rich solid-solution layered cathode materials Li2MnO3-LiMO2 (M=Co, Ni etc), which exhibit a discharge capacity of more than 200mAhg-1 when operated above 4.6V. However, the mechanism of the charge-discharge reaction, which is the origin of the discharge capacity, has not been clarified. In order to reveal the change in valence state of transition metals (TM), TM K-edge XANES was measured, but it appears to be somewhat complicated to discuss the reaction mechanism from only the experimental results. [1] In this study, we performed first-principles calculations of TM K-edge XANES spectra for Li-rich layered cathode materials using our computational code [2] based on the projector augmented-wave (PAW) method to investigate the atomic and electronic structure of TM. We calculated Ni and Co K-edge spectra for substitutions in [Li1/3Mn2/3] layers of Li2MnO3, and found that the valence states and the substitution sites are different between Ni and Co. Furthermore, we calculated Mn K-edge spectra for Mn atoms in the bulk region and near the surface, and found large differences between them. [1] A. Ito et al., J. Power Sources, 196, 4785 (2011). [2] T.Tamura et al., Phys. Rev. B 85, 205210 (2012).

The increasing demands from large-scale energy applications call for the development of lithium-ion battery (LIB) electrode materials with high energy density. Earth-abundant iron-based conversion cathode materials, such as iron pyrite (FeS2) and iron trifluoride (FeF3), are promising candidates to enable inexpensive and high energy-density LIBs because of their capability to store multiple lithium ions per structural unit at relatively positive potentials. However, significant phase transformation and structural changes involved in the electrochemical conversion reactions pose great challenge for these materials to achieve reasonable power capability and reversibility. Even though some modest performance improvements have been obtained by nanostructuring conversion electrodes and/or making nanocomposite electrodes with conductive carbon materials, microscopic mechanisms of electrochemical conversion reactions remain underexplored and this hinders the further development of better conversion cathodes. Solving this critical challenge requires integrated research efforts from both rational nanomaterial synthesis and employment of advanced in situ characterization techniques. We have recently developed scalable conversion syntheses of FeS2 and FeF3 nanowires (NWs). These NWs were made in bulk-like quantity, easy to process, and exhibited improved electrochemical performance as battery cathodes compared with those reported previously so that they can be great model systems to understand the conversion mechanism. We will present in details the syntheses, electrochemical characterization, and fundamental investigation of the conversion mechanism of these NW conversion electrode materials and discuss strategies to improve their performance.

LiNi0.5Mn1.5O4 spinel has been identified as one of the most promising candidates for the next generation lithium ion battery (LIB) cathodes because of its high energy density, good cycling stability, and good rate performance. The high discharge potential of LiNi0.5Mn1.5O4, about 4.75 V vs. Li, provides high energy density, and enables the possibility of coupling LiNi0.5Mn1.5O4 with high-voltage anodes for improved safety. However, the operating voltage of LiNi0.5Mn1.5O4 is beyond the upper voltage limit of the state-of-art electrolyte consisting LiPF6 solute and carbonate solvent, about 4.3 V. At such a high voltage unwanted electrolyte oxidation occurs, leaving decomposition products including inorganic lithium salts and organic carbonates. As a result, large irreversible capacity and low coulombic efficiency are usually observed for LiNi0.5Mn1.5O4 with conventional electrolytes.
We fabricate an artificial solid electrolyte interphase (SEI) on LiNi0.5Mn1.5O4 using a solid electrolyte material, lithium phosphorus oxynitride (Lipon). Lipon provides paths for lithium ions conduction, and maintains mechanical integrity during cycling. Our results indicate that the electrolyte decomposition can be largely suppressed by this artificial SEI film with a thickness of nanometer scale. Thicker Lipon further increases the coulombic efficiency, but at the expense of increased resistance to the cell; the optimum thickness is between 1 and 50 nm. Our strategy of using model systems comprised of thin film cathodes coated with well controlled artificial SEI films presents a sensitive way to reveal reactions with the liquid electrolyte and provide insight into the thickness requirements and mechanisms by which an artificial SEI stabilizes the interface of high voltage cathodes in conventional electrolyte solutions.

Along with the enormous advances of rechargeable lithium ion batteries as a power source of mobile electronics, solving safety issues related with the current liquid electrolyte based batteries is highly desirable. Recently, there has been a great interest in developing solid electrolyte due to improved safety including non-flammability, reliability and leakage-free property. Among solid electrolyte materials, compounds with a composition of Li-La-M-O(M=Ta, Nb, Zr) have been widely studied as a fast lithium ion conductors over the last few years. Recently, Murugan and coworkers have successfully synthesized garnet-type Li7La3Zr2O12 providing high lithium ion conductivity, chemical stability against lithium metal and wide electrochemical window. However, solid state method requires several steps of thermal treatment and grinding as well as too high synthesis temperature and long time in their work. In our work, we demonstrate a solution-based synthetic route to prepare Li7La3Zr2O12 with cubic garnet-like structure. The starting materials have been mixed to the molecular level in solution state, leading to the homogeneous Li7La3Zr2O12 compounds. The size and morphology of Li7La3Zr2O12 could be controlled by chemical reaction under high temperature and high pressure reducing sintering temperature and time. Moreover, the optimized doping level of Al or Ge might lead the enhanced ionic conductivity of Li7La3Zr2O12.

In the pursuit of high energy density lithium-ion batteries (LIBs), significant effort has been expended to explore high performance cathode and anode materials. Silicon (Si) has the greatest lithium storage capacity per unit mass, and is therefore the most promising potential candidate to replace graphite as the anode material in future generations of batteries. The main challenge in utilizing silicon comes from the structural failure induced by its huge volume change (>300%) during electrochemical cycling, leading to capacity loss. Carbon nanotubes (CNTs) have a high surface area, low density and high electrical conductivity and provide an ideal scaffold for loading silicon when the structure is tailored to accommodate the silicon expansion.
In this work, we present a flexible and free-standing film with a nanocomposite architecture where the CNTs are super-aligned and self-supporting while being individually coated with silicon. The nanocomposites were produced by winding aligned sheets of CNTs from super-aligned CNT arrays. The CNT sheets were then conformally coated with silicon using chemical vapor deposition. The aligned CNT structure provided significant inter-tube space for a controlled expansion of the silicon volume change. The morphology allowed the composite nanostructures to exhibit high specific capacity, up to 1600 mAh/g for samples also exhibiting excellent cyclic stability. The structures were found to exhibit wave-like deformation along the CNT longitudinal direction during electrochemical cycling. This phenomenon helped to explain the cyclic stability of the CNT-Si sheet structure. This design can be extended to other cathode and anode materials for binder-free and flexible LIBs.

As increasing the attention of nanotechnology, the nano-functional materials have drawn tremendous research atten-tion for different industrial applications. There have been a great number of efforts to introduce the unique methods for preparation of nano-materials and its characterization in order to prove nanotechnology&’s superiority, which can break through the current limitations of bulk materials.
Reduced graphene oxide (RGO) could be thought of an ideal substrate for preparation of nano-functional materials due to its high electric conductivity and large accommodation ability of nano-particles from high specific surface area. In particular, the oxygen functional groups such as hydroxyl (-OH), epoxy (-O-), carboxyl (-COOH) groups on RGO sheets greatly act as the pinning points for nucleation of nano-materials. The solution-based wet chemical methods such as sol-gel method, solvo-thermal method, and co-precipitation method have been generally used to prepare the nano-functional materials. Such nano-materials anchored on RGO sheets are expected to have an enhanced electron transport rate, superior electrolyte contact area for high performance electro-catalytic or electrochemical devices. However, solid-state method for preparation of nano-functional materials has nearly reported and the size of nano-materials is quite large as few hundreds nano-meter scale.
Herein, we report a simple strategy for preparation of sulfur nano-particles (<30 nm) anchored on RGO sheets as a functional materials by melting and solidification of commercial sulfur, which is few hundred micro-sized powders. It has unique structure of sulfur nano particle decorated on microwave-assisted reduced graphene oxide and exhibits the enhanced electrochemical properties More details on the synthetic procedure and structural and electrochemical properties will be discussed at the meeting.

The Mg70-xTi12+xNi12Mn6(x=8, 16, 24, 32) alloys were prepared by mechanical alloying, the structure and property were investigated by XRD, PCT and DTA measurements.
In the early milling, the mixture was composed of elements with HCP and FCC structure. After 100h milling, the diffraction peaks of Mn element disappeared and the peak intensities of Mg and Ni element were weaken and the degree of amorphous increased, which indicates that the Mn element and some of Mg and Ni element had been dissolved into the bulk of Ti. When milled 200h, the peak intensities of Mg and Ni element were further weaken and the peak intensities of Ti at 2theta;=35.3°, 38.4°, 40.2°and 43.1° increased. The BCC structure appeared at 2theta;=43.1°, 63.1° and 70.7° for Mg46Ti36Ni12Mn6 and Mg38Ti44Ni12Mn6 alloy. With milled 400h, for Mg46Ti36Ni12Mn6 and Mg38Ti44Ni12Mn6 alloy, the diffraction peaks of Mg disappeared completely and only two structures, the BCC and FCC structure, consisted in the alloys. The FCC structure was correspondent to some Ni elements not dissolved. At usual temperature, the space structure of Ti element is α phase with HCP structure. When heated to 1082°C, the metal phase transforms from α with HCP structure to β with BCC structure. High energy ball milling may result in metal phase structure from HCP structure transforming to BCC structure.
In order to improve the hydrogen storage property of the alloy, TiF3 and Nb2O5 were chosen as additive. For example, after the Mg46Ti36Ni12Mn6 as-mixed (without milling) powder +5wt.%M( M= TiF3, Nb2O5) were milled 200h, the hydrogen storage capacity of Mg46Ti36Ni12Mn6+5wt.%M( M= TiF3, Nb2O5) alloy reached 2.31 and 2.36wt.% , respectively. TiF3 and Nb2O5 as additive can improve the hydrogen storage capacity of Mg-Ti alloy.

β&’&’-alumina is the most common solid electrolyte used in Na-beta alumina batteries (NBB). For NBBs the β&’&’-alumina electrolyte is the most important component for the battery performance, and contributes approximately 50% to the total cell resistance at full charge. To reduce the electrolyte resistance, and realize improved electrochemical performance, the thickness of the electrolyte could be reduced from its current thickness of 1-2 mm to a supported 10-50 mu;m, involving the use of a porous support tube.
Fabrication of a green β-alumina closed end porous support tube was undertaken using a ram extruder. The optimized powder was mixed with the lubricant and other organics (cellosol, DG and YB), as well as a pore former (typically graphite), in a sigma blade mixer to knead form the dough. The dough was then extruded into tubes using a ram extruder, and dried on a roller for keeping the good shape of the tubes, and then finally pre-sintered. Insight into the processing mechanisms was determined from data relating shrinkage to the sintering temperature. A particular factor is the porosity shape, size and volume fraction, following heat treatment of the tubes. The porosity was altered by the addition of a pore former agent, changing both the shape and size of the pore. This has to be optimized for optimal sodium metal transport. The through-pore diameter is important for gas diffusion in the battery, and thus, selection of heat treatment parameters is also important to allow for optimum porosity for sodium diffusion.
The β&’&’-alumina slurry used for coating the dense layer was also synthesized through the solid state reaction method. The solid state reactions have fallen into: (i) batch sintering and (ii) pass-through sintering. As to relatively easy batch sintering, the loss of sodium at a high sintering temperature at a long holding time is inevitable. Doping with MgO is an effective way to improve the sintering properties of β&’&’-alumina. Initially, the stoichiometric powder (NaCO3, MgO, and Al2O3) was mixed homogeneously through a spray drying process. Then a series of calcination regimes of the mixed powder was carried out. It was observed that the fraction of the β&’&’ phase increased effectively as the temperature increased to 1600 °C.
In order to obtain a high purity and thin dense β&’&’-alumina layer, the particle size of the powder was decreased sufficiently by a nano-milling process. The dense layer was further enhanced by dip coating the pre-fired porous substrate tube in to this β&’&’-alumina slurry while applying a vacuum. In the case of applying a colloidal micro-particulate amorphous slurry, it was envisaged that strong penetration into the near-surface layer of the tube ensured particularly effective bonding. In addition, superplastic deformation of the amorphous particles during heat treatment accompanied by crystallization produced a thin (max. 100 micron) homogeneous micro-grain layer.

Reaching beyond the horizon of Li-ion batteries is a formidable challenge; it requires the exploration of new chemistry, especially electrochemistry, and new materials. There are two options, based on lithium, that are receiving intense interest at the present time: rechargeable Li-air and Li-S batteries.
Li-air batteries, although appearing very attractive as they can reach the highest specific capacity and possibly meet competitive costs, are just in the state of infancy. Their development and commercialization will not be achieved in the next 20-25 years while the Li-S batteries are in a far more advanced stage. Carbon-sulfur or graphene-sulfur nanocomposites were studied as cathode materials for Li-S cells. In this context, substantial advances have been made in the fabrication of nanostructured carbonaceous materials which have been applied to improve the performance of Li-S batteries [1].
On the other hand, organic disulfides have attracted much attention as cathode materials since it was discovered that disulfide bridge could go through reversible redox reaction for energy storage[2]. Thus, two novel sulfide polymers, poly(2-phenyl-1,3-dithiolane) and poly[1,4-di(1,3-dithiolan-2-yl)benzene] were tested as cathode materials in rechargeable lithium battery [3] and the charge-discharge tests showed that the specific capacity retained at 300 mAhgminus;1 and 100 mAhgminus;1 after 20 cycles.
Herein we have explored the possible use of Potassium tetra thionate and Lithium tetra thionate (K2S4O6 and Li2S4O6)as electrode materials for Li-sulphur batteries. Possible advantages of these materials include their cost effectiveness and their simple preparation techniques in the case of Li2S2O3 precursors. K2S4O6 (Aldrich) was used and Li2S4O6 was prepared electrochemically from the oxidation of Li2S2O3 precursors. Electrochemical characterisation of these materials in order to understand the mechanism involved and the possible techniques of effective carbon coating, which could enhance the capacity of these interesting materials will be presented.
References:
1. Ji, X.; Lee, K.T.; Nazar, L.F. Nature Materials 8, 500 (2009).
2. Visco, S.J., Mailhe, C.C., Jonghe, L.C.D. & Armand, M.B. J. Electrochem. Soc. 136, 661-664 (1989).
3. Kiya, Y.; Henderson, J.C.; Hutchinson, G.R.; Abruña, H.D. J. Mat. Chem. 17, 4366 (2007).

New battery materials may allow one to achieve energy densities higher than that of the commercial Li-ion batteries. Sulfur (S) is an attractive cathode material due to its high theoretical gravimetric capacity (1672 mAh g-1), low cost, and environment friendliness. However, S cathodes have several key challenges to be overcome to become commercialy viable technology.
When the S is confined within the nanospace of C, these limitations can be alleviated [1]. In spite of significant efforts, surprisingly limited understanding exists on the effects of physical structural parameters of carbon in Li/S battery. Therefore, in this study, we aimed to reveal the impacts of the pore size distribution, pore volume and specific surface area of porous carbons on the temperature-dependent electrochemical performance of S-infiltrated carbon cathodes in electrolytes having different salt concentration. In order to make this study most relevant to industrial needs, we used low-cost commercial AC samples for S-C composite fabrication and evaluation, The selected ACs have been produced from natural precursors and exhibit markedly different porosity characteristics.
At atmospheric temperature operation of the cells, the accessible capacities of S-infiltrated ACs containing larger pores were found to be significantly higher than that of the S infiltrated into microporous ACs having smaller pore size and stronger interactions with sulfur and sulfides. In contrast, however, the microporous ACs provided higher capacity at the elevated temperature due to improved ion transport rate. The dissolution of polysulfide was also reduced in ACs containing smaller pores. The effect of electrolyte molarity on the performance of Li/S cells was found to depend on the AC pore size and particle size. Increasing electrolyte salt concentration from 1 to 3M was found to improve the cell performance and reduce polysulfide dissolution in all the studied S-C samples. However, further increasing electrolyte molarity and, as a result, increasing electrolyte viscosity was found to lead to high polarization and reduce the cell performance in ACs having large particle size or smaller pores.
Acknowledgements
This work was supported by Army Research Office and the KETEP.
References
[1] N. Jayaprakash, J. Shen, S. S. Moganty, A. Corona, L. A. Archer, Angewandte Chemie-International Edition 2011, 50, 5904; X. Ji, K. T. Lee, L. F. Nazar, Nature Materials 2009, 8, 500; R. Elazari, G. Salitra, A. Garsuch, A. Panchenko, D. Aurbach, Advanced Materials 2011, 23, 5641; Y. S. Su, A. Manthiram, Nature Communications 2012, 3, 1166; J. Schuster, G. He, B. Mandlmeier, T. Yim, K. T. Lee, T. Bein, L. F. Nazar, Angewandte Chemie International Edition 2012, 51, 3591; N. S. Choi, Z. H. Chen, S. A. Freunberger, X. L. Ji, Y. K. Sun, K. Amine, G. Yushin, L. F. Nazar, J. Cho, P. G. Bruce, Angewandte Chemie-International Edition 2012, 51, 9994.

With the emerging demand for large-scale, energy-storing batteries, concerns have been raised regarding the consumption of a large volume of material resources in the fabrication of batteries mostly based on transition metals. As such, requests for greener and naturally abundant materials in energy storage have been escalating recently in society. In this respect, organic chemicals available in natural resources are promising alternatives. The minimal environmental footprint as well as distinctive material properties such as light weight, flexibility, and chemical tunability makes them beneficial as an electrode material in large-scale batteries. In particular, the use of bio-inspired organic electrodes that imitate energy metabolisms, such as respiration and photosynthesis, will enable a design of more sustainable batteries. For example, the electro-active carbonyl compounds mimicking biological quinone cofactors that can be obtained from biomass through eco-friendly processes are intriguing candidates for such electrode materials. Also, flavin-based electrodes that function through the imitation of the cellular energy transduction mechanism are promising candidates we recently introduced. However, the practical use of organic-based electrodes suffers from sluggish kinetics and poor capacity retention, which originate from low electronic conductivity and dissolution of electroactive chemicals into electrolytes.
Here, we report a novel and facile design strategy for organic electrodes to achieve high energy and power densities combined with excellent cyclic stability. Non-covalent nanohybridization of electroactive aromatic molecules with single-walled carbon nanotubes (SWNTs) leads to reassembly of electroactive molecules from bulk crystalline particles into molecular layers on conductive scaffolds. The simple fabrication of this nanohybrid electrode in the form of a flexible, free-standing paper (free of binder/additive and current collector) results in ultrafast kinetics delivering 510 Wh/kg within 30 minutes (204 mAh/g asymp; 98% of theoretical capacity) and 272 Wh/kg of energy even within 46 seconds. Moreover, the stable anchorage of electroactive organic molecules on the sidewall of SWNTs enables above 99% capacity retention upon 100 cycles, which was hardly achieved for organic electrodes. Our approach can be extended to other aromatic organic electrode systems, bringing bio-inspired organic materials a step closer to practical cathodes in rechargeable batteries.
Our Recent Publications Related to This Presentation:
M. Lee, J. Hong, D.-H. Seo, D. H. Nam, K. T. Nam, K. Kang, C. B. Park. Angewandte Chemie Int. Ed. in press.

Novel mesoporous carbon/iron oxide composites were prepared through simple carbonization of blends of block copolymer containing the source of carbon, i.e., polyacrylonitrile-block-poly(t-butyl acrylate) (PtBA-b-PAN) and iron oxide nanoparticles. The addition of functionalized nanoparticles that selectively hydrogen bond with PAN segments was shown to induce order in otherwise disordered system. The ordered mesostructure of the composites was confirmed by both small x-ray scattering and transmission electron microscopy. The preparation of porous nanocomposites with high fidelity preservation of a well ordered nanostructure and well defined mesopores was achieved upon carbonization at 600oC. The electrochemical performance of the composite films was compared to that of the neat carbon and mesoporous carbon without iron oxide nanoparticles. The well defined mesoporous carbon structure together with high loadings of iron oxide nanoparticles are promising for use in electrode applications.

We study the electronic properties of graphene nanoribbons (GNRs) doped with boron and nitrogen atoms for both zigzag and armchair morphologies using density functional theory. The doping atom is located on different substitutional regions, which are varied from the basal plane toward the edge sites. The doped zigzag and armchair GNRs present a half-metallic behavior. Boron and nitrogen show an energetic preference to be located at the edge of the nanoribbons. The strongest binding energies occur when the Li atom is close to the boron sites of GNRs, especially with armchair nanoribbons, while Li adsorption is less favorable when the atom is near the nitrogen sites. Boron and nitrogen doped GNRs can be used as anode materials for Li-ion batteries, and so we will report their Li intake capacity and rationalize it in terms of their peculiar properties and morphology.

The current cost and performance of clean and efficient electrochemical energy storage devices restricts their use in numerous transportation and stationary applications [1,2]. Many organic molecules are abundant, economical, environmentally-friendly, and electrochemically active, and if selected correctly are a promising solution to extend the applications of these devices [3]. In this study polycyclic aromatic hydrocarbons (PAHs), produced in significant quantities as an industrial waste product, are introduced within carbon nanotube substrates to form high-performance positive electrodes for applications in rechargeable batteries and pseudocapacitors [4,5]. The redox potential and capacity of various PAHs are examined, and when combined with a lithium negative electrode, these materials exhibit comparable energy densities (~450 Wh/kg_electrode) and higher power densities (~100 kW/kg_electrode) than lithium-ion batteries for over 10,000 cycles.
References
1.P. Kurzweil, K. Brandt. Encyclopedia of Electrochemical Power Sources (2009) 1-26.
2.R. Wagner, N. Preschitschek, S. Passerini, J. Leker, M. Winter, J. Applied Eletrochemistry 43 (2011) 481-496.
3.T. Janoschka, M. Hager, U. Schubert. Advanced Material 24 (2012) 6397-6409.
4.T. Figueira-Duarte, K. Mullen. Chemical Reviews 111 (2011) 7260-7314.
5. S.W. Lee, B. Gallant, H.R. Byon, P. Hammond, Y. Shao-Horn. Energy and Environmental Science 4 (2011) 1972-1985.

As technologies and electronics develop, lithium ion batteries become popular power source for portable electronics and require higher energy density with superior safety. Corresponding to this requirement, polyanion compounds such as phosphates, fluorophosphates, and fluorosulfates for cathode materials have attracted a lot of attention because of their intrinsic excellent safety. Among these compounds, recently LiFeSO4F compound has been paid a lot of attention to as promising candidate for cathode material because of its high energy density. Especially, tripilite phase, one of polymorph of LiFeSO4F, shows much promising property because it has much higher potential, 3.9V than that of tavorite phase which is another polymorph, 3.6V and has reasonable theoretical capacity, 152mAh/g. Therefore, the energy density of the triplite phase is comparable to that of LiFePO4 because of its higher voltage. However, a complicated synthetic process for the triplite phase makes this compound less attractive. The complication is mainly from different thermodynamic stability of the two polymorphs, triplite and tavorite phase. In other words, the tavorite phase is thermodynamically a little more stable and easily forms at first.[2] To circumvent this different stability, two-step process has been developed to synthesize the triplite phase.[1][2][3] In the two-step process, the tavorite phase is firstly synthesized by using solvothermal or ionothermal process and then the synthesized tavorite phase is transformed to the triplite phase with prolonged annealing time at low temperature. Furthermore, the transformation of tavorite to the triplite phase really depends on experimental parameters such as ramping speed, hold time, and post-treatment process such as carbon coating. This complicated and prolonged synthetic process limits full utilization of the triplite phase. To fully utilize superior electrochemical properties of the triplite phase, LiFeSO4F, simple and fast single step synthetic process should be developed by understanding key experimental parameters.
In this talk, we will discuss key experimental parameters to obtain the triplite phase without going through the transformation of the tavorite phase and will present the developed synthetic process which is fast and single step process. Also, we will talk about the electrochemical properties of the triplite phase obtained by the developed process.
[1] P. Barpanda &Tarascon, Nature Material 10 (2011) 772-779
[2] Rajesh Tripathi & Nazar, Energy & Environmental Science 5 (2012) 6239-6246
[3] M.Ati & Tarascon, Electrochemistry Communications 13 (2011) 1280-1283

Overcoming low electronic and ionic conductivity of the electrode active materials are remaining challenges limiting the performance of lithium-ion batteries (LIB). To achieve the full capacity of the active material during the electrochemical reactions, electrons and ions need to reach the core of the inorganic material (1). In this study we optimized the surface contact area of the active material with metallic single-wall carbon nanotubes (M-CNT) by using biological molecules to act as a mediator to maximize the electron conductivity of the electrode and consequently improved the LIB performance. M13 bacteriophage is a filamentous virus that can be genetically engineered to bind CNT on different positions of the phage protein coat and grow inorganic materials including battery electrode materials (2).
Here, multifunctional M13 bacteriophage have been used to produce a conducting network template for growing FePO4 as the LIB cathode material. Employing the multifunctional phage enables locating the CNT precisely on the desired positions to enhance the surface contact of the active material with the conductive additive. To understand the effect of the contact area on the battery performance, two different hybrid structures of FePO4/CNT were synthesized; i) FePO4 with M-CNTs on the pVIII, major coat protein (main body) of the phage, and ii) FePO4 with M- CNTs on the pIII, minor protein coat located at the end of the filamentous phage. In both cases, M-CNTs are only <1 weight percent (wt%) of the total FePO4 material. The electrochemical tests were performed on the bio-templated cathode materials using standard Li-ion cells. The discharge capacity measured at the rate of C/10 indicates 30% and 44% improvement in specific capacity of the battery when M-CNTs are bound to PIII and PVIII protein coat, respectively, compared to FePO4 with no M-CNTs. This demonstrates that increasing the contact area of the FePO4 with M-CNTs improves the conductivity of the cathode by shortening the electron travelling path through the insulating active material. The discharge capacity measured at C/10 rate for the FePO4/CNT on PVIII was 175 mAh/g achieving 98% of the theoretical value. Preliminary charge/discharge results at higher rates and cycleability data of the fabricated batteries confirm higher electronic conductivity of the FePO4/CNT hybrid cathode structures.
(1)J. M. Tarascon et al., Dalton Trans. 2988 (2004).
(2)Y. Huang et al., Nano Lett. 5, 1429 (2005).

Designing hierarchical porous architectures appears today as a strong and competitive field of research. In fact, getting together the structural advantages of macropores (providing interconnected framework, hence improving the diffusion low kinetics) and micro-mesopores (generating high surface area) has led to original synthetic routes to new materials bearing enhanced properties. Particularly, mainly due to high surface area, chemical inertness and thermal stability, porous carbon materials are attractive candidates as adsorbents,1 catalyst supports,2 electrodes for batteries,3 double-layer capacitors,4or host sites for hydrogen storage.5
Herein, we report the synthesis of hierarchical porous carbonaceous foams from a dual template approach using Si(HIPE) monoliths as hard templates and triblock copolymers as soft templating agents modified with metallic nanoparticles. As porous carbons play an imperative role in advanced energy storage devices, the electrochemical performances of the carbonaceous foams bearing metallic nanoparticles were investigated as Li-S battery negative electrodes taking advantages of the sulfur affinity toward metallic surfaces. In battery configuration, the hybrid foams delivered an irreversible capacity of 1000-1200 mAh g-1 during the first discharge. Upon cycling, partial extraction of Li gave reversible capacities of 600-500 mAh g-1 after 50 cycles keeping around 50% of initial capacity.
1 Foley, H.C. Microporous Mater. 1995, 4, 407.
2 Kyotani, T. Carbon 2000, 38, 269.
3 (a) Ryoo, R.; Joo, S.H.; Jun, S. J. Phys. Chem. B, 1999, 103, 7743. (b) Lee, J.; Yoon, S.; Hyeon, T.; Oh, S.M.; Kim, K.B. Chem. Commun. 1999, 2177. (c) Jun, S.; Joo, H.S.; Ryoo, R.; Kruk, M.; Jaroniec, M.; Liu, Z.; Ohsuna, T.; Terasaki, O. J. Am. Chem. Soc. 2000, 122, 10712. 7 (a) Joo, S.H.; Choi, S.J.; Oh, I.; Kwak, J.; Liu, Z.; Terasaki, O; Ryoo, R. Nature, 2001, 412, 169.
4 (a) Brun, N.; Prabaharan, S.R.S.; Morcrette, M.; Sanchez, C.; Pécastaing, G.; Derré, A.; Soum, A.; Deleuze, H.; Birot, M.; Backov, R. Adv. Funct. Mater, 2009, 19, 3136. (b) Brun, N.; Prabaharan, S.R.S.; Morcrette, M.; Deleuze, H.; Birot, M.; Babot, O.; Achard, M.-F.; Surcin, C.; Backov, R. J. Chem. Phys. C, 2012, 116, 1408.
5 Brun, N.; Janot, R.; Gervais, C.; Morcrette, M.; Deleuze, H.; Sanchez, C.; Backov R. Ener. & Environ. Sci., 2010, 3, 824.

Two high surface area carbon powders, Kurray YP 17 and NK 261 (Kurray Chemical) were modified by thermal treatments with the goal of obtaining materials with different surface properties. X ray diffraction (XRD) was used to characterize the carbon&’s crystal structure, size, and orientation. A Micromeritics Accelerated Surface Area and Porosimetry Analyzer (ASAP) instrument was used to measure the surface area, pore volume and pore size distribution of the samples. Energy dispersion spectroscopy (EDS) was performed and correlated with diffuse reflectance infrared fourier transform spectroscopy to calculate the percentage and type of surface oxygen groups.
It is shown that the total surface area decreased linearly with the heat treatment temperature and the average pore width decreases exponentially with temperatures above 1500 C. The distance between graphene sheet layers and percentage of single layers was shown to decrease linearly with increasing temperature. Heat treatment temperatures above 1100 C showed little effect on surface oxygen groups. Manipulating the pore structure of activated carbon has applications in lithium ion electrochemical devices.

Rechargeable Li-ion secondary batteries are being developed for use in high power applications such as fully electric vehicles and hybrid electric vehicles because of their high energy density and high power density compared to other battery technologies. Lithium manganese oxide (LiMn2O4) is a promising cathode material for such batteries because of its low cost, abundance of Mn, higher safety and environmental compatibility than the conventional layered cathode. Its crystal structure is of the spinel type (space group Fd3m), and lithium ions can be reversibly intercalated into the structure in all three crystallographic directions. For future application in all-solid-state batteries, multilayer thin films need to be fabricated, and an understanding of the microstructure of the film and interfaces between film and substrate, including the crystal orientation, is needed to obtain optimal and stable battery performance. In this study we report the fabrication of LiMn2O4 thin films on different single-crystal substrates using a chemical solution deposition method (CSD). Interface structures were investigated using electron microscopy techniques as a prelude to understanding their effects on lithium interecalation-deintercalation behavior. Epitaxial LiMn2O4 thin films formed on Au/Al2O3 substrates using an [Li-Mn-O] metallo-organic precursor solution were studied in detail by XRD and HREM. STEM observations were also performed using an aberration-corrected STEM with a high-angle annular dark-field and annular bright detector and annular bright-field detector with atomic-scale resolution. Similar characterizations were also performed for films deposited on MgO and SrTiO3 substrates. In all cases, Li columns could clearly be observed in the interior of the films, confirming the successful fabrication of epitaxial grains. In contrast, the structure of the heterointerface between LiMn2O4 and the substrates could not be observed clearly because of lattice strain resulting from mismatch between the crystal lattices of the film and substrate materials.

Capacity differences between negative and positive carbon electrode materials reflect the degree of resistance met under both Li-ion insertion and intercalation processes. Faradaic and electrostatic charge storage mechanisms for a given carbon surface can be advanced to their most efficient, cell-compatible working potentials by manipulating electrochemical accessibility. The working potential during charging and discharging of hybrid, battery-type supercapacitors is limited by the specific capacitance of the amorphous carbon positive electrode, and the kinetic reversibility of the pre-lithiated negative electrode. The work presented shows how carbon surface modifications can drastically increase the electrochemically available surface area of carbon substrates for use in Li-ion hybrid supercapacitors employing nonaqueous electrolytes. The implementation of specific oxygen functionality is shown to increase the overall graphitic order and total surface area of the substrate. Surface oxidation is also responsible for increasing the uptake of a perfluorinated surfactant at outer, carbon edge sites. When cycled below 0.8V (vs. Li), a fully homogenous surface layer is shown to form on the treated electrodes by an exclusive, two-electron decomposition of LiPF₆ EC/PC/DEC electrolyte. Reversible loading capacities are shown to increase by over 400% compared with non-treated electrodes. Higher charge storage facilitating solid-electrolyte layer forms—with a mechanistic key being the elimination of trace surface water, resulting in homogenous composition of the SEI layer and increased availability of electrochemically labile surface area. Such tandem oxidation and surfactant passivation methodology is also potentially applicable to positive electrode materials employing their own form of pre-cycling surface treatment. Electrochemical impedance spectroscopy and specific capacitance of treated electrodes further illustrate the effects of increased pore accessibility.

Lithium ion batteries (LIBs) are widely considered critical energy storage devices for moving toward an energy sustainable future. The realization of this potential calls for next generation LIBs of higher performances than the current generation LIBs that use graphite anodes and lithium metal oxides cathodes. Among the scrutinized anode materials, silicon is one of the most promising ones, because of its high charge capacity, earth abundance, low cost, and long history of well-developed industry. However, silicon suffers from a poor cyclability due to the volume fluctuation induced electrode damage with the lithiation/delithiation cycles. To date, many strategies have been developed to tackle this problem. Despite great improvements by using silicon nanoparticles, practical applications mandate higher performance. Furthermore, little attention has been paid to another critical problem: although either the anode or the cathode has to be pre-lithiated to pair these electrodes for a practical LIB, such pre-lithiated electrodes are barely studied.
In this presentation, we will report our effort of developing pre-lithiated silicon (lithium silicide) anodes, which also hold the promise for solving the poor-cyclability problem caused by the volume fluctuation. The work includes synthesis, characterization, and performance assessment of lithium silicide nanoparticles. Compared with the un-lithiated electrode using silicon nanoparticles, the pre-lithiated electrode showed much better charge capacity, cyclability, and rate compability.

There is a dire need to provide a sustainable solution to the growing global demand for energy. It is this incessant demand that is the driving force fueling various current and emerging technologies including lithium ion batteries, supercapacitors and fuel cells. Conventional double layer supercapacitors hold a unique place among these energy storage devices on account of their high power density and excellent cycling stability. However, they have limited energy densities necessitating research into novel pseudocapacitor materials to render them competitive against high energy density Li-ion systems. Transition metal oxides bear promise as pseudocapacitor materials on account of their ability to undergo reversible oxidation state changes as a result of a partially filled d-band. Nanoscale oxide materials however are hamstrung on account of their electrical conductivity limiting their performance at high rates. Coating oxide materials on conducting structures such as carbon nanotubes (CNTs) is a promising approach to increase energy and power densities. In addition, doping and vacancy creation in the parent oxide also results in improved electronic conductivity and thus capacitor performance. We report herein the electrochemical capacitor performance of such CNT-doped vanadium oxide nanoscale heterostructures in aqueous electrolytes. The nanostructures are generated using a simple, cost-effective chemical vapor deposition technique demonstrating excellent gravimetric and areal (~300 mF/cm2) supercapacitance. Results of these studies will be presented and discussed.

Developing flexible and deformable supercapacitor electrodes based on porous materials is of high interest in energy related fields. Here, we show that carbon nanotube sponges, consisting of highly porous conductive networks, can serve as compressible and deformation-tolerant supercapacitor electrodes in aqueous or organic electrolytes. In aqueous electrolyte, the sponges maintain a similar specific capacitance (>90% of original value) under a predefined compressive strain of 50% (corresponding to a volume reduction of 50%), and retain more than 70% of original capacitance under 80% strain while the volume normalized capacitance increases by 3-fold. The sponge electrode maintains a stable performance after 1000 large strain compression cycles. A coin-shaped cell assembled with these sponges shows excellent stability for 15000 charging cycles with negligible degradation after 500 cycles. Our results indicate that carbon nanotube sponges have the potential to fabricate deformable supercapacitor electrodes with stable performance.The fabrication process is simple and low-cost, only involving direct compression on freestanding bulk sponges consisting of self-assembled CNTs synthesized by CVD method. It might be possible to graft pseudocapacitive layers into the sponges and make hybrid nanocomposites to build high performance and deformable supercapacitor electrodes.

Recently, we have studied in detail the symmetric supercapacitor based on graphene (G)-polypyrrole (PPY), G-polyaniline (PANI), G-polyethylenedioxythiophene (PEDOT) and G-polythiophene (PTH) conducting nanocomposite electrode materials [1-4]. Our graphene-conducting polymer has shown high power density and stability in an ionic liquid electrolyte. We have also obtained the specific capacitances of 500 F/g (G-PANI), 374 F/g (G-PEDOT), 150 F/g (G-PTh) and 160 F/g (G-PPY) in symmetric configuration of mentioned electrode materials [1-6]. The performance of the supercapacitor could be enhanced by increasing the surface area and conductivity of the electrode materials as well as fabricating the asymmetric based supercapacitor. In the present work, we present the findings of the electrochemical properties of asymmetric electrodes based on supercapacitors in aqueous and organic electrolytes. The asymmetric electrodes are promising for obtaining an improved specific capacitance and operating voltage range of a supercapacitor.
References:
[1] H. Goacute;mez, M. K. Ram, F. Alvi, P. Villalba, E. Stefanakos, A. Kumar, J. Power Sources, 196 (2011), 4102.
[2] F. Alvi, M. K. Ram, P. A. Basnayaka, E. Stefanakos, Y. Goswami, A. Kumar, Electrochimica Acta, 56 (2011) 9406.
[3] F Alvi, P. Basnayaka,, M. K. Ram, H. Gomez, E. Stefanakos, Y. Goswami , A. Kumar, J. New Mater. Electrochem. Systems (2012) 089.
[4] F. Alvi, M. K. Ram, P. Basnayaka, E. Stefanakos, and Y. Goswami 219th ECS Meeting, Montreal, QC, Canada - Electrochem. Soc. 1101, (2011) 596.
[5] P.A. Basnayaka, M. K. Ram, E. K. Stefanakos, A. Kumar, Supercapacitors based on graphene-polyaniline derivative nanocomposite, electrode materials, Electrochimica Acta 92 (2013) 376.
[6] P.A. Basnayaka, M. K. Ram, E. K. Stefanakos, A. Kumar, High performance graphene-poly (o-anisidine) nanocomposite for supercapacitor applications, Materials Chemistry and Physics (2013) (in press)

The development of nanotechnology in the past two decades has generated great capability of controlling materials at the nanometer scale and has enabled exciting opportunities to design materials with desirable photonic, electronic, ionic and mechanical properties, which are important for advanced energy conversion and storage. In this talk, I will show how we design rationally nanostructured materials for advanced rechargeable batteries, including: high capacity Si anodes and S cathodes and grid scale storage.

Energy generation and storage are two most important technologies in today&’s green and renewable energy science. In general, they are two distinct processes that are usually accomplished using two separated units designed based on different physical principles, such as piezoelectric nanogenerator [1] and Li-ion battery [2, 3]; the former converts mechanical energy into electricity in the first place, and the latter stores electrical energy as chemical energy. There had been no physical processes which can generate and store the energy in a single step, with simplified systems and elevated energy efficiency.
Here, we introduce a fundamental mechanism that directly hybridizes the two processes into one, using which the mechanical energy is directly converted and simultaneously stored as chemical energy without going through the intermediate step of first converting into electricity. By replacing the polyethylene separator as for conventional Li battery with a piezoelectric poly(vinylidene fluoride) (PVDF) film, the piezoelectric potential from the PVDF film as created by mechanical straining acts as a charge pump to drive Li ions to migrate from cathode to the anode, which changes the concentration of Li ions around the two electrodes, thus induces the charging reactions. Based on this new mechanical-to-electrochemical process, the nanogenerator and the battery are hybridized for the first time as a single unit—a self-charging power cell (SCPC), which can be charged up by mechanical deformation and vibration from the environment. The overall energy conversion and storage efficiency of this mechanical-to-electrochemical process is much higher than that of the traditional charging methodology with the external rectification of the electric signals from piezoelectric generator. With the comprehensive tests of such self-charging behavior, it has been clearly confirmed that it should be viable to fully charge the SCPC through this as-proposed mechanism. Thus, through the improvement of the device structure and the fabrication techniques in the future, it will definitely be a powerful energy technology. Such an integrated self-charging power cell provides an innovative approach for developing new mobile power source for both self-powered systems and portable/personal electronics. [4]
This invention of the self-charging power cell which generates and stores energy in one step has been named as one of the Top 10 physical science breakthroughs in 2012. [5]
[1] Wang, Z. L.; Song, J. H. Science 2006, 312, 242minus;246.
[2] Tarascon, J. M.; Armand, M. Nature 2001, 414, 359minus;367.
[3] Chan, C. K.; Cui, Y. et al. Nat. Nanotechnol. 2008, 3, 31minus;35.
[4] Nano Lett. 2012, 12, 2520-2523
[5] http://physicsworld.com/cws/article/news/2012/dec/14/physics-world-reveals-its-top-10-breakthroughs-for-2012

Battery and ultracapacitor electrodes are traditionally made with at least one polymeric binder material that mechanically holds the various powder like raw materials together. In addition to increasing the electrode resistance, the binder is assumed to be at least partially responsible for the performance degradation over time for rechargeable Lithium batteries.
We present here for the first time, by example of a lithium iron phosphate (LFP) based cathode, a novel lithium battery electrode design manufactured with CVD Equipment Corporation&’s proprietary NanoToMacrotrade; platform technology that facilitates a binder-free approach. Preliminary tests, done by Graphene Batteries AS, show that between 0.2 and 5C rates this binder-free cathode has a similar specific capacity versus charge/discharge rate performance as the standard cathodes. Results of still ongoing more detailed studies will show if such a novel battery electrode manufacturing design can actually be used to delay the degradation of lithium batteries charging performance over increased numbers of charge/discharge cycles. In addition, we will present test results for 2-4 times thicker than normal (60 µm) cathode electrodes, which we expect will allow to significantly increase the volume and/or weight based energy density of lithium battery design.

Rechargeable all solid state lithium or Li-ion batteries are attractive power sources for small scale applications (smart cards, medical implants), but in the near future may also become relevant as bulk systems for a wider range of applications, as they improve safety and stability over conventional batteries with flammable liquid electrolytes. This requires electrochemically stable Li+ fast ion conducting (FIC) solids as the electrolyte. In the search for such stable fast ion conductors, numerous materials have been explored recently such as lithium rich sulfide glasses and ceramics. However, limitations in current density remain a major obstacle.
Among the most promising fast ion conductors are the thiophosphate-based solid electrolytes. Our in situ X-ray and neutron diffraction studies showed that disorder in the immobile sublattice is a crucial factor for maximizing their conductivity. This is shown by combining experimental characterisation and molecular dynamics simulations for both the argyrodite-type halide-doped thiophosphates Li₆PS₅X (where anion-ordered Li₆PS₅I exhibits the lowest ionic conductivity despite the lattice expansion by the large soft I-, while the S2-/X- disorder for X = Cl, Br opens up local paths for Li+ motion) as well as for Li₁₀GeP₂S₁₂, where the local P/Ge disorder limits the packing density and leaves free volume for fast ion transport channels Li(1)-Li(3)-Li(3)-Li(1) along c and their interconnection to an anisotropic 3D pathway network via interstitial Li(4) sites. As revealed by our simulations cation transport is facilitated by local PS₄^- reorientations.
The nearly ideal hopping distance of 1.7 - 2.3 Å among partially occupied sites and the moderate energy required for interconnections between the 1D channels render this structure type particularly suited to combine fast ion transport with structural stability. The fully occupied site Li(2) does not participate in ion transport at room temperature. Strategies for further optimization of this relatively new class of solid electrolytes by isomorphous replacement are discussed.
To reduce the synthesis costs of these two classes of thiophosphate solid electrolytes, our recent experimental work focused on the development of moderate temperature (or no heating) routes for the preparation of Argyrodites, Li₁₀GeP₂S₁₂ and classical Thio-LISICONs. Room temperature ionic conductivity of low-temperature processed Li₆PS₅Cl reaches >1 mS/cm. All solid state battery using Li₄Ti₅O₁₂/Li₆PS₅Cl/Li show a first discharge capacity, ~ 75 mAh/g, good capacity retention and 99% columbic efficiency over > 100 cycles. In contrast, rechargeable high capacity solid state batteries with conversion electrodes reach their theoretical capacity of 560 mAh/g, but show prominent capacity fading. Impedance studies and battery performance of the thiophosphate solid electrolytes with other insertion and conversion-type cathode materials will be discussed.

The advancement of battery systems with high energy and power densities remains a lynch pin for new generations of energy storage. This challenge is being actively investigated where two broad conceptual approaches are being adopted by our research group for development of materials for high power. The first is the design and synthesis of compositionally unique materials that provide crystallographic structures facilitating ion insertion and deinsertion at high voltage and energy density. The second approach under exploration is the systematic control of materials properties such as crystallite size, particle size and surface area and their relationship to the material electrochemistry.
Synthetic control of silver hollandite, AgxMn8O16, with the systematic control of silver content is demonstrated. This level of compositional control was enabled by development of a low temperature based synthetic approach. Notably, ability to control the silver to manganese ratio enabled corresponding control of crystallite size as well as control of surface area and particle size indicating the ability to tune material properties in a systematic manner. The impact of the modified materials on electrochemical performance was examined under a variety of electrochemical tests. In all cases, the synthetic modification of the AgxMn8O16 material by reducing crystallite size showed a profound benefit on the resultant electrochemistry.

Ordered mesoporous carbons (OMC) are of great interest as electrodes in novel energy applications due to their high electric and thermal conductivity, chemical inertness and low density. Due to the electrically insulating property of sulfur and the solubility of polysulfides in the electrolyte, much attention in academic and industrial research has been focused on composites of OMCs with sulfur as the cathode material in lithium-sulfur batteries in recent years. However, no conclusive, systematic study of the performance of these electrodes correlated to the structural characteristics of the carbon host has been reported. In this work, we show the synthesis and characterization of soft-templated mesoporous carbon materials with uniform and tunable pore sizes through the organic-organic self-assembly of a block copolymer and a carbon precursor. Synthesized morphologies include hexagonally packed cylinders and co-continuous cubic with one-dimensional and three-dimensional porosity, respectively. Pore size dependence on block copolymer molar mass and the temperature stability of the resulting materials were tested. Temperature and post-activation of the carbon material could be used to control the degree of microporosity, tuning the surface area and the porosity fraction of micropores. This set of identically synthesized highly ordered carbon materials was subsequently used for a systematic investigation on the influence of structural parameters such as mesopore size, dimensionality, surface area and microporosity, on the cycling performance of carbon-sulfur cathodes. Due to the use of identically synthesized OMCs with a broad variety of structural parameters, this study provides conclusive results on the dependence of the lithium-sulfur battery performance on the porosity characteristics of the carbon host.

Sulfur (S) is considered to be one of the candidates for the next generation cathodes due to its high theoretical gravimetric capacity, low cost and its abundance in nature [1]. While this capacity is an order of magnitude higher than that of existing commercial electrode materials, S cathodes still have several challenges to overcome for successful commercialization. The use of carbide derived carbon (CDC) for sulfur(S) nano-confinement can be greatly advantageous because of the precise tuning of the pore size distribution possible by both selecting different carbide precursors and changing the process parameters during the synthesis of such carbon materials [2].
Novel nanostructured S-CDC composites having ordered mesopores and high S content have been successfully prepared for lithium sulfur batteries. Higher CDC synthesis temperature and the resulting lower concentration of defects and higher purity was found to allow for higher S content, higher capacity utilization and better rate capability of S-CDC cathodes. The opportunity to independently tune the size of both the CDC micropores and straight, aligned mesopores suggest a great promise of CDC technology for both the fundamental studies and practical applications. In contrast to commercial activated carbon power, the dual pore size distribution in CDC allow for the high rate performance and provides sufficient freedom to study the impact of electrolyte composition. In our study, higher electrolyte molarity was found to greatly enhance capacity utilization and reduce S dissolution in S-CDC composite cathodes, thereby overcoming the key challenges of S/Li chemistry. Due to the presence of straight mesopore channels combined with high micropore content in CDC, the produced S-CDC cathodes not only demonstrated nearly theoretical capacity in 5M electrolyte solution, but also showed outstanding resistance to dissolution. [3]
Acknowledgements
Different aspects of this work were supported by the Energy Efficiency & Resources program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) funded by the Korea government Ministry of Knowledge Economy (grant 20118510010030) and by the US Army Research Office (grant W911NF-12-1-0259). The authors from Dresden University of Technology gratefully acknowledge financial support by the project “Nanomaterials for future generation Lithium Sulphur batteries” (“MaLiSu”).
References
[1] P. G. Bruce, S. A. Freunberger, L. J. Hardwick, J.-M. Tarascon, Nat Mater 2012, 11, 19; X. Ji, K. T. Lee, L. F. Nazar, Nature Materials 2009, 8, 500.
[2] G. Yushin, R. K. Dash, Y. Gogotsi, J. Jagiello, J. E. Fischer, Adv. Funct. Mater. 2006, 16, 2288.
[3] Y. Z. Jung Tae Lee, Sören Thieme, Hyea Kim, Matin Oschatz, Lars Borchardt, A. Magasinski, Wonil Cho, Stefan Kaskel and Gleb Yushin, Advanced Materials 2013, In press.

Lithium-sulfur (Li-S) is an attractive next generation battery because of the high theoretical specific capacity of sulfur at 1672 mAh/g and a specific energy of approximately 2600 Wh/Kg. The current capacity of Li-S batteries typically ranges from 800-1000mAh/g, 4-5 times that of current Li-ion technology. However, Li-S batteries have not achieved widespread commercialization due to limited lifetimes from either capacity fading or outright failure. This poor long-term performance has been associated with “shuttling” of polysulfides dissolved in the electrolyte medium across the separator to the Li metal anode. A second causality of the limited cycle stability arises from precipitation of Li2S discharge products. As discharge proceeds into the low voltage plateau, the soluble high-order polysulfides are reduced to Li2S, which is insoluble in ethereal solvents and deposit as a hard, intractable solid on the cathode surface. Furthermore S undergoes a volume expansion of roughly 80 % when forming Li2S which creates mechanical stress on the cathode framework. Repeated cycling creates cracks in the cathode which, over time, leads to performance degradation as Li2S encrusted carbon detaches from the electrode. Minimizing the cathode damage caused by Li2S deposition is essential for extending the long term performance of lithium sulfur batteries.
We present a method to improve the cathode materials in high-energy density Li-S batteries by copolymerizing molten sulfur with 1,3-diisopropenylbenzene (DIB). This approach termed, inverse vulcanization, transforms S into a processable copolymer that is stable at room temperature; the molten sulfur in the presence of the DIB does not depolymerize into elemental S8 rings and remains a high molecular mass copolymer. When used as a cathode material in Li-poly(sulfur) batteries, these copolymer offers dramatically improved cycling performance and capacity loss compared to elemental S. It is believe that the DIB prohibits the formation of the polysulfides that poison Li-Su battery performance. We present high-resolution electron microscopy and scattering measurements to characterize the multi-scale 3D-architectures created within the pristine and cycled composite cathodes with various contents of the electroactive copolymers. The morphology, structures, bonding and local compositional distributions of the S, copolymers, and conductive carbon nanoparticles, as well as their extended pore structures and transformations under cycling, are examined to provide insights into mechanisms of the enhanced capacity retention. These measurements suggest that the incorporation of the DIB into the sulfur copoloymers increases the molecular level compatibility of the active S cathode materials with the current collecting carbon black particles, thereby increasing the homogeneity of the composite cathode material and decreasing the likelihood of plating out polysulfides that kill battery performance.

Lithium/Sulfur batteries, due to their high theoretical values of gravimetric (2500 Wh kg^-1) and volumetric (2800 Wh L^-1) energy densities, became one of the most popular candidates for next-generation energy storage system [1]. However, it is necessary to better understand the working mechanism of this system, in order to help improve electrochemical performances. It is well known that structural and morphological changes occur inside the cell upon cycling, since the red-ox reaction is accompanied by phase transformation of active material (solid/liquid phases). Many research teams applied X-ray diffraction technique to analyze Li/S batteries, mostly via ex situ methodology [2-4]. According to our best knowledge, only few reports were devoted to in situ XRD studies [5,6]. However, there are several discrepancies between the literature data. In order to get clearer insight into structural changes occurring inside the battery during real time operation, we carried out in situ and operando X-Ray diffraction analysis.
In situ XRD measurements were performed in two synchrotron facilities (SOLEIL and ESRF in France). Few independent cells were monitored during several complete cycles and at two different current rates (C/20 and C/8). Special pouch cell design allowed us to monitor the evolution of complete cell as well as each electrode separately. Our results show that all elemental sulfur present at the beginning in the electrode is getting reduced into soluble lithium polysulfides during initial discharge, by the end of first plateau. After that active material is in soluble form in the electrolyte. Well defined peaks of crystalline Li₂S start to appear just at the beginning of lower discharge plateau and reach the maximum intensity at the very end of discharge (1.5V). We also found out that during following charge crystalline Li₂S is getting oxidized back into soluble lithium polysulfides, which are further oxidized into elemental sulfur (end of charge, 3V). Nevertheless, the crystal structure of sulfur formed after recrystallization was found to be different from the orthorombic α-sulfur used in electrode preparation. Here, for the first time, we report appearance of another sulfur allotrope in Li/S system: monoclinic β-S. Very similar phase evolution was found during few next cycles [7].
This work emphasizes the importance of performing in situ and operando analysis as the most accurate way to analyze precisely the real time system evolutions.
[1] N.S. Choi et al., Angew. Chem. Int. Ed. 2012, 51, 9994
[2] H.S. Ryu et al., J. Power Sources 2009, 189, 1179
[3] S.E. Cheon et al., J. Electrochem. Soc. 2003, 150, A796
[4] Y. Wang et al., Electrochim. Acta 2009, 54, 4062
[5] N.A. Cañas et al., J. Power Sources 2013, 226, 313
[6] J. Nelson et al., J. Am. Chem. Soc. 2012, 134, 6337
[7] S.Walus et al., submitted

The development of Li-S battery technology has been plagued by problems arising from the highly insulating nature of sulfur (5×10-30 S cm-1 at 25 °C), the high solubility of lithium polysulphides in the electrolyte and volumetric expansion of sulfur during lithiation. We demonstrate the design and preparation of a series of unique carbon materials, including hierarchical porous carbon, carbon nanotubes and graphene, for sulfur loading to fabricate cathode structures for lithium-sulfur batteries.
Sulfur/ hierarchical pores carbon composites
In this work, unique carbon materials with various hierarchical pores were synthesized from zinc containing metal-organic frameworks (MOFs). This presents a novel method and rationale for utilizing carbonized MOFs for sulfur loading to fabricate cathode structures for lithium-sulfur batteries. High temperature pyrolysis of MOFs is shown to produce carbon with tunable hierarchical porous morphology. Starting with different MOFs, it is possible to produce variations in the pore volume, surface area and size distribution in the resulting carbon structures which can then serve as hosts for sulfur loading to make Li-S batteries.
Sulfur/ carbon nanotube composites
In this work, we have designed and prepared a composite cathode made of sulfur and high density carbon nanotubes (HD-CNT). This cathode demonstrates very high electrochemical stability and high discharge capacity up to 200 full discharge/charge cycles. This is achieved by limiting the diffusion of polysulphides and accommodating the volume expansion of sulfur in the CNT scaffold while promoting the extent of reaction sites. These encouraging results combined with the knowledge of the interface between polysulfide species and carbon nanotube surface could lead to novel approaches in the design and fabrication long cycle life lithium battery electrodes.
Sulfur/ graphene composites
In this work, we demonstrate the design and preparation of a lightweight sulfur cathode, which is made by loading sulfur on to a network of graphene. In an important breakthrough we have shown that sulfur cathode system can be incorporated within a Li-S battery without using the following conventional auxiliary battery components of binding agents, conductive additives (such as C-black) and a metallic current collector at the cathode. Eliminating these components can greatly help in reducing the net battery weight and increase the flexibility. The resulting sulfur/ graphene foam cathode presents good electrochemical stability and high rate discharge capacity retention for 400 full discharge/charge cycles at a high current density of 3200 mA g-1. The knowledge acquired in this work is important for the design of efficient lightweight and high-performance batteries that can be incorporated directly in flexible electronics.

Many attractive solid electrolytes for lithium conduction have been reported, yet few are being used in batteries with direct contact to a lithium metal anode. Extended cycling of lithium metal anodes requires an electrolyte that is thin and conductive, electrochemically stable, and also mechanically robust in order to resist lithium roughening and dendrite formation. Because no single material has this combination of properties and a cost-effective manufacturing route, we are investigating composites of two or more electrolyte materials where in principle the structure can be engineered to optimize ion transport, interface impedance, and mechanical integrity.
Laminate, dispersed and sintered composites of a variety of polymer and ceramic components are being investigated experimentally. These are compared to, and guided by our estimates using effective medium models. [1] Both experiment and modeling have been focused largely on the garnet lithium lanthanum zirconate ceramic electrolyte [2] and on typical polyethylene oxide polymer electrolytes with dissolved lithium salts. Knowledge and control of the ionic conductance attributed to the polymer/ceramic interfaces [3] and also the grain boundaries for ceramic electrolytes [4] are important factors for many composite structures. Impedance and conductivity of selected interfaces and composites with blocking and lithium metal contacts will be presented.
Acknowledgement: This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy and by the U. S. Army Research Office.
References:
[1] Sergiy Kalnaus, Wyatt E. Tenhaeff, Jeffrey Sakamoto, Adrian S. Sabau, Claus Daniel, Nancy J. Dudney Analysis of composite electrolytes with sintered reinforcement structure for energy storage applications, Journal of Power Sources, (2013) 241, 178.
[2] E. Rangasamy, J. Wolfenstine, and J. Sakamoto, The role of Al and Li concentration on the formation of cubic garnet solid electrolyte of nominal composition Li7La3Zr2O12, Solid State Ionics (2012) 206, 28.
[3] W. E. Tenhaeff, K. A. Perry and N. J. Dudney, Impedance Characterization of Li Ion Transport at the Interface between Laminated Ceramic and Polymeric Electrolytes, J. Electrochem. Soc. (2012) 159, A2118.
[4] Wyatt E. Tenhaeff, Ezhiyl Rangasamy, Jeffrey Sakamoto, Yangyang Wang, Alexei P. Sokolov, Jeff Wolfenstine, Nancy J. Dudney, Resolving the grain boundary and lattice impedance of hot pressed Li7La3Zr2O12 garnet electrolytes, in press, ChemElectroChem.

Improvement of the Li-ion battery (LIB) requires both theoretical and experimental understanding of the current materials, and therewith synthesizing novel electrodes and electrolytes. Performance of the currently LIB is dependent on the unique physical properties of the solid-electrolytes interphase (SEI) formed on the anode surface. It is known that the desolvation and solvation processes of the Li-ion at the interface between the SEI and liquid electrolyte are crucial to determine the throughput rate or power of the Li-ion battery. Large-scale, first-principles molecular dynamics (FPMD) simulation of the desolvation/solvation processes is therefore highly desired. The electronic density-functional theory (DFT) is suited well for the FPMD simulation of such dynamics due to its balance between physical accuracy and computation speed. The real-space grid based implementation of the DFT (RGDFT) that uses the finite difference method for derivatives of variables, has attractive features of parallelizability and applicability to various boundary conditions in addition to universality in target materials. Taking the divide-and-conquer strategy we have recently proposed the linear-scaling, divide-and-conquer-type real-space grid DFT code (DC-RGDFT) [1] to further speedup the FPMD simulation.
In this paper, we apply the DC-RGDFT to investigate the microscopic mechanisms of the Li-ion transfer through the boundary between the SEI and liquid electrolyte in the LIB by the FDMD simulation. A relatively large simulation system (about 2400 atoms) for the boundary is modeled using di-lithium ethylene di-carbonate (Li2EDC), ethylene carbonate (EC), and LiPF6 for the SEI, solvent, and salt, respectively. After inserting Li-ions in the Li2EDC region, we perform the FPMD simulation for several ps using the DC-RGDFT. In the cases without salt, we find enhanced stability of the Li-ion at the EDC-EC boundary where both EDC and EC molecules bind to the Li-ion, which acts to impede the Li-ion transfer through the boundary. In regard to impedence for the Li-ions, such EDC-EC boundary, which is in reality only about 4 Ang in depth, can be regarded as effectively 12-20 Ang depth of bulk EDC. In the case with 1.0 M LiPF6 salt included in liquid EC, we find that the Li-ion transfer rate through the EDC-EC boundary becomes about twice as high as that in the case without salt. Separate DFT calculations about the reaction energy profiles of small model systems clarify that the energy required to detach a Li-ion from the boundary decreases to 0.9 eV from 1.7 eV if PF6 exists. The lowering in the detaching energy of the Li-ion results from weakening of the interaction between the Li-ion and EDC due to binding of PF6 to the Li-ion at the boundary. The temperature dependence of the Li-ion transfer rate is analyzed also.
[1] N. Ohba S. Ogata, T. Kouno, et al., Comp. Phys. Commu. 183 (2012) 1664-1673.

Lithiation and delithiation processes in Li ion battery electrodes lead to significant volume changes. In addition to creating internal stresses in the active electrode materials, these dimensional changes can substantially alter the stability of the solid electrolyte interphase (SEI). It is difficult to probe the mechanical response of the SEI directly in complex electrode microstructures that consist of powdered active components and other constituents. However, thin films provide an opportunity to investigate fundamental processes more directly. To accomplish this, we employed in situ stress measurements, conventional in situ electrochemistry, and ex situ surface characterization with TEM, XPS, and SIMS. This work focuses on graphitic carbon anodes, where we have recently shown that substantial near-surface stresses occur during the formation of the SEI layer. The experimental results were also used to develop models of mechanical failure in the SEI. The results from these experiments and models provides guidance for engineering stresses during SEI formation, to enhance the stability of these critical passivation layers.

Solid electrolytes for Li-ion batteries (LIBs) are receiving considerable interest owing to rising concerns with liquid electrolytes, e.g. solvent leakage, flammability and safety hazards. The development of a Li-ion solid electrolyte with high ionic conductivity at low temperature and a wide electrochemical window of stability is of utmost importance for next-gen applications. Recently, sulfide based glasses have shown good Li-ion conductivity of about 0.012 S/cm at room temperature; however, the synthesis of these materials requires stringent and lengthy synthesis procedures, and high temperature processing at a high energy cost. Crystalline ceramics and glassy thin films have been explored as electrolytes, but they are generally too brittle, which makes it difficult to form large-area membranes. Further, they typically possess high interfacial contact resistance with solid electrodes. On the other hand, use of a polymer-based electrolyte system such as polyethylene oxide (PEO) suffers from hindered the Li-ion transport dynamics of the polymer chains resulting in overall ionic conductivity. In this presentation we will describe the synthesis of PP13PF6 (N-Propyl-N-methylpiperidinium cation (PP13+) and hexafluorophosphate anion (PF6-)) new ionic crystal, which is stable to water and air and possesses a wide electrochemical window of 7.2V vs. Ag. We demonstrate that these ionic crystals can be used as electrolyte membranes in solid state Li-ion batteries as they display enhanced Li-ion conductivity of 0.24 mS/cm at 45 °C, which is higher than the literature reported values for other solid state ionic crystals. The reason for high Li-ion conductivity is revealed by theoretical calculations showing the energy barrier for the Li-ion transport of only 0.4 eV which matches well with the experimentally determined activation energy. Further, molecular motions in the ionic crystal facilitates facile Li-ion transport.

Lithium containing garnets LixM2M&’3O12 have recently gained a significant amount of attention as a family of promising solid-state electrolytes due to their exceptionally high ionic conductivity at room temperature and electrically insulating character.
The partial occupancy of the interpenetrating tetrahedral and octahedral Li-sites permits the diffusion of Li ions through the lattice, resulting in low activation barriers for the diffusion of Li ions. Common approaches in the search for high Li-ion conductivities are the aliovalent substitution to increase the Li content in garnets, due to charge neutrality constraints.
Our recent investigations focus on the isoelectronic substitution and the influence of the ionic radii on the crystal structure and the ionic transport in the solid solutions Li6CaLa2Ta2O12, Li6Ca0.5Sr0.5La2Ta2O12, Li6SrLa2Ta2O12, Li6Sr0.5Ba0.5La2Ta2O12 and Li6BaLa2Ta2O12 . While substitution of La with A2+ introduces more Li in the structure of Li5La3Ta2O12, differences in ionic radii of the A2+ cation lead to different activation energies and ionic conductivities.
Here we report on the influence of the ionic size of the constituents on the Li ionic transport in the garnet solid solution Li6ALa2Ta2O12. We have employed a combination of temperature dependent AC Impedance Spectroscopy, DC conductivity measurements and X-ray scattering techniques to understand the ionic conductivity in these materials. For instance, following Vegard&’s law, the bigger Ba cation leads to a lower ionic conductivity at room temperature (4*10^-5 Scm-1) than in the Sr analogue (7*10^-6 Scm-1).
An attempt will be made to relate the transport properties of the materials with each other in respect to the difference in their structure and bonding interactions.

We prepared Li7-xLa3Zr2-xTaxO12 (LLZTO, varying Ta-content) [1] and Li6BaLa2Ta2O12 (LBLTO) [2] garnet-type thin films by pulsed laser deposition (PLD). These thin films were prepared by ablation of the respective target materials on various substrates, including Ohara glass and porous anodized aluminum oxide (AAO). All prepared thin films were characterized in terms of their crystal structure, morphology and electrochemical properties. Additionally, protective coating of Ohara glass and implementation of thin film solid electrolyte membranes in hybrid cell systems were tested.
Garnet-type crystal structures of the thin films were verified by X-ray diffraction (XRD). The deposited garnet-type thin films crystallize in the bulk crystal structure with a slightly preferred orientation. In addition, scanning electron microscopy (SEM) of garnet-type thin films revealed a columnar growth of the deposited material. The Li-ion conductivity was determined by electrochemical impedance spectroscopy (EIS) and additionally verified by dc measurements with lithium electrodes. The thin films show conductivities of up to σ=3x10^minus;5 S/cm at 25 °C, which is about one order of magnitude lower than the conductivity of the respective bulk garnet-type sample. The relatively low conductivity, compared to the bulk material, may originate from the microstructure of the thin film.
Nevertheless, one advantage of garnet-type solid electrolytes is their stability against metallic lithium. Thereby, Li-ion conducting garnet type thin films can be used as solid electrolytes for all solid state batteries. So far, mainly LiPON with lower ionic conductivity (σ=2x10^minus;6 S/cm) [3] is used as Li-ion conducting thin film. In addition to all solid state batteries, solid electrolytes can be also used as protective coatings. We were able to show that decomposition of Ohara glass in contact with metallic lithium can be effectively prevented by depositing a thin LBLTO protective layer on the surface of an Ohara glass substrate. Furthermore, garnet-type thin films on porous AAO substrates can be used in so called hybrid cells as Li-ion selective solid electrolyte membrane. These hybrid cells contain liquid electrolyte on both sides of this membrane, hereby, separating efficiently the anode and the cathode compartment from each other. Thus, only Li-ion exchange is possible over the solid electrolyte membrane and any kind of additional shuttle mechanism can be suppressed.
ACKNOWLEDGMENT: The research was supported by the BASF scientific network of electrochemistry and batteries.
[1] Buschmann, H., Berendts, S., Mogwitz, B. Janek, J., J. Power Sources 2012, 236-244.

[2] Thangadurai, V., Weppner, W., Adv. Funct. Mater. 2005, 15, 107-112.
[3] X. Yu, J.B. Bates, G.E. Jellison, F.X. Hart, J. Electrochem. Soc. 1997, 144, 524-532.

High-power energy storage devices, such as metal-ion batteries, are critical for the development of zero-emission electrical vehicles, large scale smart grid, and energy efficient cargo ships and locomotives. The energy storage characteristics of metal-ion batteries are mostly determined by the physical and chemical properties of their electrodes. This talk will review the recent developments of various types of nanocomposite electrodes by our research group and our collaborators, where we demonstrate significant improvements of the electrodes&’ energy and power storage characteristics over the state of the art materials. Some of the recent results have already been published [1-6], while others are in review or in preparation.
We demonstrate the ability of the rationally designed nanocomposites to overcome several key technological challenges, which includes stabilization of the positive and negative electrodes for metal-ion (mostly Li-ion) against various degradation mechanisms and the formation of truly multifunctional electrodes with high strength, high toughness, high electrical conductivity, high flexibility and high specific and volumetric capacities. In many examples stable performance for over 1000 cycles have been demonstrated. In order to overcome the limitations of traditional composites precise control over the materials&’ microstructure and porosity was required.
Acknowledgement
Different aspects of this work have been supported by NSF, ARO, NASA, AFOSR and EE&R of KETEP.
References
1. Lee, J.T., Y. Zhao, S. Thieme, H. Kim, M. Oschatz, L. Borchardt, A. Magasinski, W. Cho, S. Kaskel and G. Yushin, Sulfur-Infiltrated Micro- and Mesoporous Silicon Carbide-Derived Carbon Cathode for High Performance Lithium Sulfur Battery. Advanced Materials 2013(in press).
2. Kim, H., J.T. Lee and G. Yushin, High temperature stabilization of lithium-sulfur cells with carbon nanotube current collector. Journal of Power Sources, 2013. 226(0): p. 256-265.
3. Evanoff, K., J. Khan, A.A. Balandin, A. Magasinski, W.J. Ready, T.F. Fuller and G. Yushin, Towards Ultrathick Battery Electrodes: Aligned Carbon Nanotube - Enabled Architecture. Advanced Materials, 2012. 24(4): p. 533.
4. Evanoff, K., J. Benson, M. Schauer, I. Kovalenko, D. Lashmore, W.J. Ready and G. Yushin, Ultra Strong Silicon-Coated Carbon Nanotube Nonwoven Fabric as a Multifunctional Lithium-Ion Battery Anode. ACS Nano, 2012. 6(11): p. 9837-9845.
5. Choi, N.S., Z.H. Chen, S.A. Freunberger, X.L. Ji, Y.K. Sun, K. Amine, G. Yushin, L.F. Nazar, J. Cho and P.G. Bruce, Challenges Facing Lithium Batteries and Electrical Double-Layer Capacitors. Angewandte Chemie-International Edition, 2012. 51(40): p. 9994-10024.
6. Boukhalfa, S., K. Evanoff and G. Yushin, Atomic layer deposition of vanadium oxide on carbon nanotubes for high-power supercapacitor electrodes. Energy & Environmental Science, 2012. 5(5): p. 6872-6879.

A novel process has been developed to achieve three-dimensional iron electrodes with targeted porous morphologies for use in alkaline nickel/iron battery cells. It was expected that the increased surface area of the porous electrodes would increase the capacity and amp hours per gram values compared to non-porous nickel-iron battery electrodes. The performance capability was measured in terms of the initial and evolved morphology of the porous electrode. The effects of the features, including potential nanostructures, were correlated to the capacity and amp hours per gram for each electrode tested.

Stable nitroxide radical bearing polymers are attracting much attention for their application as electrode materials in organic radical batteries. This is due in large to the rapid charging capability and excellent cycling stability of the nitroxide radical functionality. A greater understanding of the inherent charge transfer limitations in such systems, particularly with respect to the relationship between performance and structure of the radical bearing polymer, will be paramount to further advancements in the field. To this extent, we have synthesized a series of model nitroxide radical polymers containing perylene-based fluorescent markers. Since the nitroxide radical has an established quenching effect on photoluminescence (PL), and since tuning the oxidation state of the nitroxide radical in an electrochemical half-cell can effectively modulate that quenching, we present a methodology to evaluate fundamental charge transport phenomena in the model nitroxide radical polymers. The perylene moieties in this study were covalently attached to methacrylic monomers and incorporated into the nitroxide radical polymers via living polymerization techniques. Furthermore, we employ immobilized nitroxide radical-containing polymer brushes, tethered to transparent conducting oxide substrates, as a model system for charge and ion transport. We demonstrate how to introduce the fluorescent markers at systematic intervals and well-defined positions along the backbone of the tethered brush. In the presentation, preliminary PL data is presented together with our overview of the above results.

Oxidized graphene nanoribbons were obtained through longitudinally unzipping multi-walled carbon nanotubes (MWCNTs). Using different amounts of the oxidizing agent (KMnO4), various degrees of oxidation and unzipping of the MWCNTs were achieved. Upon thermal reduction at different temperatures, various morphologies of graphene nanoribbons (GNRs) were created. The morphologies of the GNRs were characterized using transmission electron microscopy (TEM), x-ray diffraction (XRD), and Raman spectroscopy. The degrees of reduction were observed using Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA). The resulting GNRs were further tested electrochemically as anode active materials in Li-ion half-cells.

A new type of Re-Mg-Ni series compounds with PuNi3-type superstructure has been paid more attention and considered as the new candidates of the negative electrode materials of Ni/MH rechargeable batteries owing to their low production cost and higher electrochemical capacity compared to AB5-type alloys.
In this paper, Re3-xMgx(Ni0.7Co0.2Mn0.1)9(x=0.5, 0.75, 1.0, 1.25) alloys were prepared by induction levitation melting under argon atmosphere. The crystal structures of the hydrogen storage alloys were characterized by a Rigaku D/max 2500V diffractometer. The pressure-composition isotherms (P-C-T) curves for hydrogen absorption/desorption were measured with an automatic Sieverts-type apparatus. Discharge capacity, cycle stability, high rate dischargeability (HRD), cyclic voltammetry and Tafel polarization curves of the alloy electrodes were measured by Arbin instrument.
In the alloys, LaNi5 phase, La2Ni7 phase and Mg2Ni phase were the main phases, the cell volumes of the LaNi5 phase and La2Ni7 increased with the Mg content increasing.
The Re3-xMgx(Ni0.7Co0.2Mn0.1)9(x=0.5, 0.75, 1.0, 1.25) alloys exhibited a hydrogen-storage capacity of 0.92, 1.00, 1.36 and 1.08 wt.%, respectively. The Re2Mg(Ni0.7Co0.2Mn0.1)9(x=1.0) alloy showed lower hydrogen absorption plateau and better kinetics property
Electrochemical studies showed that the maximum discharge capacity of the alloy electrodes initially increased from 285 mAh/g (x = 0.5) to 385 mAh/g (x = 1.0) and then decreased to 370 mAh/g (x = 1.25). The Re2Mg(Ni0.7Co0.2Mn0.1)9(x=1.0) alloy electrode had better cyclic stability and wider discharge potential plateau (shown in Fig.2). As the Mg content increasing, the high rate dischargeability and the limiting current density increased.

Recent works about utilizing porous silicon (PS) as anodes of Li-ion batteries have presented studies of macroporous layers which structure demonstrates relative strength to the recharging. From the other hand it is very attractive to fabricate proper anodes based on meso-PS. The surface area of meso-PS is significantly greater (100-300 m2/cm3) than that of macro-PS (10-100 m2/cm3) and is prospective to provide an increase of discharge capacity. That is why we studied the possibility to use meso-PS as negative electrodes of Li-ion batteries.
Meso-PS was formed by anodization of n+-Si wafers in mixture of HF:H2O:C3H7OH=1:3:1 at 50-80 mA/cm2 current density for different periods of time. The final PS layers had pore diameters about 20-70 nm, thickness - 1-15 microns and porosity - 50%. In order to form free porous electrode the following method was applied. After anodization PS was covered with thick copper film by successive electroless and electrodeposition up to the moment of complete separation of PS/Cu layer from the Si wafer. Injection and extraction of Li were performed from 1M LiCl DMSO-based solution at 1 mA/cm2.
The maximal discharge capacity was 2300 mA h/g which is even higher than known values for macro-PS. After 25 cycles of charge/discharge we observed significant destruction of PS. SEM analysis revealed presence of cracks in PS and thinning of pore walls.
Despite the destruction of meso-PS we suggest that optimization of its structural parameters and recharging regimes improve anode's characteristics.

The energy and power density of lithium ion battery largely depends on cathode materials. In LiFePO4, the most commercially successful phosphate cathode material, Li ion is transferred between two phases, LiαFePO4 and Li1-βFePO4, which implies a significant energy barrier for the new phase nucleation and interface growth, contrary to the fast reaction kinetics experimentally observed. Theoretical work in our Center has suggested that during the reaction, a single-phase transformation path may exist at very low overpotential ~30 mV, which can explain the remarkable rate capability of LiFePO4. The interparticle Li-ion transport is predicted to be an important factor for the reaction mechanism. For instance, the two-phase equilibrium state observed in ex situ studies is achieved that way. In this work we investigate interparticle transport in two LiFePO4 samples with different particle size, over 150 nm and below 30 nm. We use synchrotron XRD to investigate the single-phase range (α, β) for both samples, the solid solution formation upon temperature increase and particle size evolution of the two phases (LiαFePO4 and Li1-βFePO4) during cycling. We also apply intermittent titration techniques (PITT and GITT) to various cell configurations, i.e. using LiαFePO4 and Li1-βFePO4 as electrodes, to study the driving force for the transport of lithium ions. The kinetics of Li-ion transport in such cells and the role of particle size in the reaction mechanism will be discussed. This work is supported by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC001294.

The effect of geometry on the power density and chemical stresses is assessed for a half cell three-dimensional LiCoO2 cathode structure. Simulations demonstrate that as the aspect ratio of the 3D structure increases, the charge capacity of the structure decreases by 50%, but its structural integrity improves by approximately 40% as compared to its thin film counterpart. This effect occurs because the back of the electrode is electrochemically shielded by the electrochemically active 3D tip. Mechanically, during galvanostatic discharge, chemical stresses become tensile at the electrolyte | electrode tip interface and more compressive at the electrode | back contact interface, as a result of the electric field focusing at the tip of the 3D structure. When the aspect ratio of the 3D structure increases, the conical structure mechanically relaxes the substrate of the structure, thus reducing the possibility of mechanical failure-induced capacity loss. A critical aspect ratio that maximizes the discharge stresses, xi;prime;=0.32 was identified.

A unique and straightforward synthesis of graphene-wrapped Li₄Ti₅O₁₂ particles was rendered by solid-state reaction between graphene-oxide-wrapped inexpensive P25 (TiO₂) and Li₂CO₃. Even though graphene/Li₄Ti₅O₁₂ composites were previously reported, uniform wrapping of graphene on individual Li₄Ti₅O₁₂ grains has not been reported yet. The graphene-wrapped Li₄Ti₅O₁₂ exhibited remarkable specific capacity of 147 mAh g^-1 at a rate of 10 C (1 C = 175 mA g^-1) after 100 cycles. This rate capability is the highest ever reported in Li₄Ti₅O₁₂ with 150 ± 50 nm grains. The improved rate capability is attributed to the enhanced electronic conductivity of each Li₄Ti₅O₁₂ grain via uniform graphene wrapping, with the single-grain growth during annealing from the initial ~25-nm TiO₂ nanoparticles confined by outer graphene sheets. Graphene-eliminated Li₄Ti₅O₁₂ by thermal decomposition was also directly compared with the graphene-coated sample, to clarify the role of graphene with nearly-equivalent particle size/morphology distributions. [1] Y. Oh, D. Ahn, S. Nam, and B. Park, J. Solid State Electrochem.14, 1235 (2010). [2] S. Yang, X. Feng, S. Ivanovici, and K. Müllen, Angew. Chem. Int. Ed.49, 8408 (2010). Corresponding Authors: Chunjoong Kim: [email protected] and Byungwoo Park: [email protected]

Judicious design and controlled structural manipulation of advanced carbon materials drives the development of a wide range of high-performance electrochemical devices such as biosensors, lithium-ion batteries, and supercapacitor devices. We report a facile and highly effective strategy to adjust systematically the microstructures, surface chemistry, and electronic structure of electrospun carbon nanofibers (ECNFs) using a microwave-assisted oxidation process. The microwave-treated ECNFs with controlled structures are characterized by transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and ultraviolet photoelectron spectroscopy. Various electrochemical techniques are employed to evaluate the energy storage performance of the microwave-treated ECNFs. We found that through optimization of the microwave treatment conditions significant improvement of the electrochemical energy storage capabilities of the ECNFs can be achieved.

Carbon-coated hematite (α-Fe2O3) nanostructures are deposited directly on the stainless steel substrates by a facile pyrolysis of ferrocene for lithium battery anodes. The as-prepared nanostructures have been investigated with scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electrochemical characterisation. The carbon coated hematite nanostructures show high reversible capacity of 1145 mA h /g after 200 cycles at the rate of 0.5C and high columbic efficiency of 76% in the first cycle. The electrochemical performance improvements can be attributed to the uniform and thinner carbon coating layers, which could lead to formation of uniform, stable and thin solid electrolyte interphase (SEI) films. The facile synthesis of carbon coated hematite nanostructures opens a way to large-scale production in practical application of Li-ion battery anode.

An effective strategy is implemented to mitigate capacity fading of high energy density Co3O4 by use of hollow and mesoporous Co3O4 spheres and graphene sheets in a core-shell geometry. The core-shell structure exhibits a high reversible capacity of 1076 mAh g-1 at a current density of 0.1 A g-1, and excellent rate performance from 0.1 to 5.0 A g-1. The graphene/Co3O4 nanosphere composite electrode also displays an exceptional cyclic stability with an extraordinarily high reversible capacity over 600 mAh g-1 after 500 cycles at a high current density of 1.0 A g-1 without signs of further degradation. The highly conductive graphene nanosheets wrapping up on surfaces and interfaces of metal oxide nanospheres provide conductive pathways for effective charge transfer. The mesoporous features of graphene and hollow metal oxide nanosphere also enable fast diffusion of lithium ions for charge/discharge process. The highly flexible and mechanically-robust graphene nanosheets prevent particle agglomeration and buffer volume expansion of Co3O4 upon cycling. The unique nanostructure of Co3O4 wrapped up with highly flexible and conductive graphene nanosheets represents an effective strategy that may be applied for various metal oxide and high energy density electrodes to mitigate the mechanical degradation and capacity fading, critical for developing advanced electrochemical energy storage systems with long cycle life and high rate performance.

One-dimensional nanostructures such as nanowires, nanorods, and nanotubes (NTs) are actively being investigated as efficient charge collectors for energy storage and conversion applications.Anatase TiO₂ is one of the promising anode materials for lithium ion batteries due to its intrinsic higher chemical stability during the discharging/charging. However its poor rate capability and capacity fading limited to commercialize it. Various approaches have been reported to overcome this problems related to poor electronic conductivity and kinetics in anatase TiO₂. Nanotube structures of TiO₂ allow for better accommodation of the large volume changes without the initiation of fracture that can occur often in bulk or micrometer-sized TiO₂. Each of TiO₂ NTs is electrically connected to the metallic current collector directly so that all the NTs contribute to the capacity as direct 1-D electronic pathways allowing for efficient charge transport.Electrochemical characteristics of TiO₂ NTs as anodes for lithium ion batteries that have large surface area, high aspect ratio as well as high areal density are investigated in this study. The wall thickness of TiO₂NTs is directly related to irreversible capacity and also the specific capacity. Reversible phase transformation of TiO₂ (anatase) NTs&’ anode for lithium ion batteries has been observed by ex-situ transmission electron microscopy (TEM). Phase transformation from tetragonal (TiO₂anatase) to orthorhombic (fully discharged - Li_0.5TiO₂) and back to tetragonal (fully charged -TiO₂anatase) in completely cycled TiO₂ NTs are observed. For the nanometer-sized NTs, anatase TiO₂ is converted into Li₁TiO₂ (reversible capacity of ~ 440mAh/g)having the same space group (I4₁/amd) as anatase, but they have different lattice parameters. The Galvanostatic discharge-charge curves of anatase TiO₂ tube cycled between voltage of 0.7V and 3V. At 1.75V versus Li/Li⁺, the main plateau is observed for phase transition of Anatase TiO₂. After the first transition, the electrochemical measurements at 1.5V present pseudoplateau region that structure changes again second phase from Li_0.5TiO₂-orthorthombic to Li₁TiO₂-tetragonal. Even after 50^th cycle, the TiO₂NT anodes have structural stability and maintain their high crystal quality.

New battery technologies beyond current lithium-ion cell chemistries are under intense global research and development. Among the new proposed chemistries, the Silicon-based chemistry is one of the promising technology that meets the requirements of low cost, high energy density, and higher safety margin. We present the materials and chemistry aspects of a silicon-based battery chemistry. The role of nano-scale electrode materials on performance optimization of Silicon-based battery will be addressed. The dominant issue of lithium battery during the last two decades, beyond the safety problem, has been the low cathode capacity (<200 mAh/g) while maintaining a reasonable voltage (>3.5 V vs. Li), and silicate cathode is a logical choice as they have potential for exceeding >200 mAh/g at above 3.5 V with very high thermal stability (>400 C). However, extraction and utilization of second electron from transition metals in silicates (2e/TM) has proven to be difficult. We report a novel structural - and electrode formulation optimization that allows to extract >200 mAh/g from silicate based cathode. Optimization of capacity retention of silicon composite anode also has been a major challenge, due to its large volume change during charge-discharge cycle. We will report a novel engineering of Si-C composite at a level of 25- 30 wt% silicon loading that provides over 1000 mAh/g capacity with good cycle life. The fundamental nature of silicon lithiation/delithiation at nanoscale, and electrode formulation optimization also will be discussed

Silicon nanopowder has been directly laminated on roughened Cu current collector and cycled versus lithium without any binder or carbon additive to emphasize all the side reactions on a very thin layer. The simplicity of the set-up allows relating the cyclic voltammetry to the active material and capacity fading to the side reactions with the electrolyte, to provide a standard for any new silicon nanomaterial, even on a very small scale. We demonstrate that reversible cycling can be achieved, reaching a capacity of 1500 mAh/gSi after 300 cycles (C rate) with coulombic efficiency above 98.5%.
Furthermore, we modified the Si surface by direct alkylation of the silicon (Si-C bond) to provide an effective passivation layer. In parallel, we grafted metallic nanoparticles on the Si surface to improve the formation of the SEI.

A number of literatures have appeared on the enhancements of carbon-based SnO₂ composites for Li-ion batteries. These previous studies implicitly send messages that the focus should be placed on dealing with the inevitable particle damage. In this respect, graphene has been considered as a good candidate both to buffer the volume expansion of active particles and to attain electronic percolation. It is no wonder that some optimized contents of graphene exist since the coating layer could lead to sluggish Li-ion diffusion. Nonetheless, severe wrapping is advantageous to accommodate volume expansion of Sn nanoparticles, and therefore a smart manipulation of the coating layer is necessary to fully utilize the wrapping effect. In this report, graphene is modified to have a large porosity (BET surface area: 160 m²/g) by a simple heating-rate-controlled thermal reduction, and the effect of wrapping by porous graphene on the electrochemical performance is examined as a case study. The porosity-induced graphene layers will provide a new strategy for the encapsulation of active materials which undergo pulverization during cycling.
[1] S. Nam, S. Kim, S. Wi, H. Choi, S. Byun, S.-M. Choi, S.-I. Yoo, K. T. Lee, and B. Park, J. Power Sources211, 154 (2012).
[2] S. J. Yang, S. Nam, T. Kim, J. H. Im, H. Jung, J. H. Kang, S. Wi, B. Park, and C. R. Park, J. Am. Chem. Soc.135, 7394 (2013).
Corresponding Author: Byungwoo Park: [email protected]

Although a silicon (Si) electrode is one of best candidates to replace graphite for high-performance Li-ion battery owing to its high theoretical capacity, it still suffers from poor cycle life.[1] The researchers working on Si electrodes have revealed that the bad cycle life of silicon should be caused from severe volume expansion (pulverization) and formation of unstable solid-electrolyte interface.[1] The coating of carbon and silver or making oxidation layer are known as good ways to solve such issues about the Si electrode.[2-4] We had already developed one-dimensional Si-rich carbon nanofibers to achieve high battery capacity as well as good cycle life in previous study.[5] However, because much higher trans-membrane flux of Li-ions are requested to achieve its theoretical capacity for each charge or discharge process, we need to develop more efficient and durable separators for Si-based electrodes.
Herein, we fabricated a novel separator based on polymer-nanoclay composite nanofibers for our Li-ion anode of Si-rich carbon nanofibers. Since nanoclay was used to reinforce polymer nanofibers and provide higher porosity and wettability, the hybrid nanofiber separator can be durable and practical for charge/discharge processes. After the nanofiber separator composed of PAN+Nanoclay synthesized by electrospinning was characterized for microstructural properties, the coin-typed cells were fabricated to examine electrochemical properties from cyclic voltammetry or electrochemical impedance spectroscopy and the battery performance from galvanostatic charge/discharge measurements. The battery cell using our nanofiber separator exhibits a much decreased charge transport resistance in Nyquist plots and an increased activity in cyclic voltammograms, compared with those using a commercial polyethylene (PE) separator. Furthermore, the nanofiber separator displays a much more stable cycle life than the commercial PE. Interestingly, the hybrid nanofiber separator obtained a high capacity of around 800 mAh/g at high C rates. Such improvements were attributed to one-dimensional nanofiber separator reinforced by nanoclay able to offer much higher trans-membrane flux of Li ions. The current study demonstrates that the development of high performance separators becomes critical in improving the overall performance of Li-ion batteries based on high capacity electrode materials.
References
[1] H. Wu, Y. Cui, Nano Today 2012, 7, 414.
[2] Y. -S. Hu, R. D. -C, M. -M. Titirici, J. -O, Muller, R. Schlogl, M. Antonietti, J. Maier, Angew. Chem. Int. Ed. 2008, 47, 1645.
[3] Y. Yu, L.Gu, C. Zhu, S. Tsukimoto, P. A. V. Aken, J. Maier, Adv. Mater. 2010, 22, 2247.
[4] H. Wu, G. Chan, J. W. Choi, I. Ryu, Y. Yao, M. T. McDowell, S. W. Lee, A. Jackson, Y. Yang, L. Hu, Y. Cui, Nature Nanotech. 2012, 7, 310.
[5] Y. S. Kim, K. W. Kim, D. Cho, N. S. Hansen, J. Lee, Y. L. Joo, Submitted 2013.

Transition metal based conversion compounds have attracted extensive attention due to the possibility of multiple redox states enabling storage of more than one lithium per transition metal atom, resulting in much higher specific capacity than conventional intercalation compounds. However, conversion compound electrodes often suffer from poor power density and poor cyclability at least in part because of the intrinsically poor ionic and electronic conductivity of the materials. Addition of a conductive agent, usually carbon, improves cyclability significantly, but with a reduction of the overall capacity. Here, using a colloidal templating strategy, we three-dimensionally architecture and nanostructure conversion compound electrodes to overcome the sluggish kinetics. We focus on FexOy, but will also discuss the use of oxyfluorides. Bicontinuous Ni inverse opals formed via colloidal templating with pore size of about 500nm were used as the current collectors, and FexOy nanoparticles (30-50nm) were electroplated onto this scaffold. By using a pulsed voltage deposition method, a uniform coating of nanoparticles on the Ni scaffold was realized. After optimizing the phase of the materials, cycling tests showed a good specific capacity (~1000mAh/g). The high-rate performance of the three-dimensional electrodes was impressive. At a rate of 10C, 88% of the 0.1C capacity was delivered. When cycled at about 10C, more than 50% of the initial capacity was retained after 100 cycles. The good capacity and cyclability of the three-dimensional electrodes was due to the combination of the porous electrode support structure and the nanostructured active phase which provided short pathways for both ions and electrons.

We propose a facile method for synthesizing an intriguing Si membrane structure with good mechanical strength and three-dimensional (3D) configuration that is capable of accommodating the large volume changes associated with lithiation in lithium ion battery applications. The membrane electrodes demonstrated a reversible charge capacity as high as 2,414 mAh/g after 100 cycles at current density of 0.1 C, maintaining 82.3 % of the initial charge capacity. Moreover, the membrane electrodes showed superiority in function at high current density, indicating a charge capacity > 1,220 mAh/g even at 8 C. The high performance of the Si membrane anode is assigned to their characteristic 3D features, which is further supported by mechanical simulation that revealed the evolution of strain distribution in the membrane during lithiation reaction. This study could provide a model system for rational and precise design of the structure and dimensions of Si membrane structures for use in high performance lithium ion batteries.

We demonstrate a facile, two-step coating/calcination approach to grow a uniform MnO nanoparticle@mesoporous carbon (MnO@C) composite on conducting substrates, by direct coating of the Mn-oleate precursor solution without any conducting/binding reagent, and subsequent thermal calcination. The monodispersed, sub-10 nm MnO nanoparticles offer high theoretical energy storage capacities and catalytic properties, and the mesoporous carbon coating allows for enhanced electrolyte transport and charge transfer towards/from MnO surface. In addition, the direct growth and attachment of the MnO@C nanocomposite in the supporting conductive substrates provide much reduced contact resistances and efficient charge transfer. These excellent features allow the use of MnO@C nanocomposites as lithium-ion battery, supercapacitor electrodes, and sensitive biosensors. As proofs-of-concept, lithium-ion battery anodes made of this monodispersed MnO@C nanocomposite display excellent reversible capacities of over 800 and 520 mAh/g at current densities of 0.1 and 2 A/g, respectively. Supercapacitors made of this MnO@C nanocomposite exhibit stable capacitances of 140 and 40 F/g, at current densities of 1 and 40 A/g, respectively, which also show excellent mechanical stability over repeated folding and stretching. Finally, this MnO@C nanocomposite demonstrates sensitive electrical response to H2O2 in buffers, and has been applied to interrogate the H2O2 concentration in cellular assays for tumor cell analysis.

Thin-film battery has a large potential in many applications including RFIDs, smart cards and sensor networks. Also, thin-film batteries can be the breakthrough in embedded systems that work to minimize the size of an electronic device. To utilize thin film battery, it is essential to develop high energy density materials. Si is one of the most attractive anode materials that can be used as an alternative to graphite, owing to its high theoretical capacity of 4,200 mAh/g. However, one of the serious drawbacks of this material is its poor cyclic stability, which arises from a large volume change (nearly 400%) during insertion and extraction of lithium.
This study examined the effects of Si-alloy structure on the microstructure evolution and electrochemical performance of sputtered Si-alloy thin film. Si-alloy thin film anode electrodes were grown on plasma-treated Cu foil by sputtering deposition with Ta adhesion layers. The electrochemical measurements were conducted with a typical coin-type half cell system. Si-alloy film as working electrode and lithium foil as a counter electrode are used in the electrolyte of 1M LiPF6 in a 1:1 mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). A careful characterization of the structure changes after cycling has been analyzed using various characterization tools such as X-ray diffraction (XRD), Scanning electron microscope (SEM) and High resolution transmittance electron microscope (TEM). The results show that the morphology and microstructure of the electrode critically determine the electrochemical properties of the electrode. A remarkable improvement in cyclic stability with high capacity over 150 cycles was achieved.

Spinel Li4Ti5O12 has attracted much attention as an anode material for lithium-ion batteries, because of its good Li-ion intercalation and de-intercalation reversibility and near-zero strain during charge/discharge processes. Despite these advantages, Li4Ti5O12 still lacks commercial implementation due to its low conductivity (10-13 Scm-1), which in turn leads to initial capacity loss and poor rate capability. Thus far, several effective ways, including reduction of particle size to nanoscale, doping with small amounts of metallic or non-metallic ions (V+5, Cr3+, Mn3+, Zr4+, F-, and Br-) in Li, Ti or O sites, surface modification and carbon coating, and formation of composite with carbonaceous materials, have been proposed for improving the rate capability of Li4Ti5O12.
In particular, reduction of Li4Ti5O12 particle size to nanoscale is expected to enhance the rate capability owing to the following reasons: (1) increase in the effective interfacial area between nanosized Li4Ti5O12 and the electrolyte, (2) high electrical conductivity of electrode, and (3) shorter diffusion length during the charge/discharge cycle. However, these nanosized metal oxides have the inherent disadvantage of agglomeration, limiting their uniform dispersion in electrodes. In addition, use of large amount of binder to prevent agglomeration, in turn complicates the electrode preparation process.
To overcome these issues, it has been recently been proposed that the formation of nanocomposites of these metal oxides with carbonaceous materials will improve their electrochemical properties. Such metal oxide/carbon matrix nanocomposites are expected to facilitate the diffusion of Li ions, owing to the enhancement in their electronic conductivity and morphological stability. Additionally, dispersing the metal oxide on the carbon matrix will hinder the agglomeration of the metal oxide, providing efficient and stable framework during charge/discharge cycling. Recently, it has been reported that the rate capability of Li4Ti5O12 has been significantly improved by forming nanocomposite of Li4Ti5O12 nanoparticles with nanocarbon materials using solution-based methods. Nanocarbon materials, such as carbon nanotubes (CNTs) and reduced graphene oxide, used in the preparation of such nanocomposites effectively improved the electronic conductivity of the electrode, thereby enhancing the rate capability.
Herein, we report a facile process based on microwave-solvothermal synthesis, in which nanocarbons were used to selectively heat the substrate for facilitating the preferential precipitation of Li4Ti5O12 nanoparticles (10-15 nm). The Li4Ti5O12/nanocarbon prepared in this study exhibited excellent rate performance as an anode material for lithium-ion batteries.
More details on the synthetic procedure and structural properties will be presented at the meeting.

Transition metal oxides have been widely studied as anode materials for lithium ion batteries due to their high reversible capacities, chemical stability, and low cost. Iron is one of the more abundant metals among the various transition metals and its oxide, Fe2O3, possesses fairly high capacity (960 mAh g-1) through the conversion reaction. We synthesize Fe2O3 nanoplates directly on stainless steel by chemical vapor deposition method using Fe(acac)3 (acac=acetylacetonate). X-ray diffraction shows the hematite (alpha-phase) to be the predominant phase (>99%) with trace amount of maghemite (gamma-phase). FESEM shows the nanoplates are between 20 to 60 nm thick and a stack of nanoplates can be as thick as 0.7 micrometer. Galvanostatic charge-discharge experiments were carried out versus Li/Li+ between 4 - 0.1 V. Approximately 1500 mAh/g has been observed, which more than the expected capacity observed through conversion reaction. We believe that the microstructure plays an important role in the storage mechanism and its effect will be discussed.

Transition metal oxides have been studied as both cathode and anode materials for lithium ion batteries. In general, 3d metal oxides anode materials possess higher theoretical capacities (> 1000 mA h/g) than that of graphite (372 mA h/g). It has been shown that metal oxides can store charges through conversion reaction with Li metal. The electrochemical reduction of the metal (M) leads to the formation of lithium oxide (Li2O) and that reaction has been shown to be reversible. Carbon coating or other additives are required for transition metal oxides in battery application. However, utilization of low cost and abundant metals such as Mn provides a variety of scalable electrode alternatives. We have deposited pure cubic phase MnO nanoplates metallic oxide directly on stainless steel by chemical vapor deposition method using Mn(acac)2 (acac=acetylacetonate). FESEM shows that the nanoplates are 10 - 30 nm thick and a stack of these nanoplates are approximately 80 nm. Electrochemical charge-discharge cycles conducted from 4 to 0.1 V shows a curve typically observes for nanomaterials. High capacity of approximately 975 mAh/g was achieved during the 1st cycle. After 25 cycles, the capacity loss was 50%, but extremely high coulombic efficiency was achieved. The relationship between microstructure and capacity will be presented.

Exfoliated graphene oxide (GO) and polysiloxane were blended and pyrolyzed to synthesize freestanding SiOC-graphene composite papers (~10 µm thick). The structural and chemical characterization of the composite prepared with varying polymer concentrations were carried out using electron microscopy, XRD, and FT-infrared spectroscopy. High resolution microscopy images shows layer by layer stacking of GO sheets and an increase in interlayer spacing was observed by X-ray analysis. FTIR peaks at 3400 cm-1 (O-H), 1720 cm-1 (C=O), 1600 cm-1 (graphene), 3056 cm-1 (Si-CH=CH2) and 1034 cm-1 (Si-O-Si) confirmed the successful functionalization of SiOC with GO. Thermo-gravimetric analysis showed enhanced thermodynamic stability of the composite paper up to at least 700 °C in flowing air. The SiOC/Graphene composite paper anodes showed stable electrochemical capacity of approx. 500 mAh/g (at the anode level), which was twice that of free standing graphene anodes. The average columbic efficiency (second cycle onwards) was observed to be approx. 97%.

Vanadium-based crystals such as V₂O₅ and Li_xV₂O₅ have been studied a lot for lithium-ion cathode because of their high capacity [1-2]. However, these materials are not good reversibility. This study examined the amorphous-crystal composite cathode prepared by glass crystallized methods to improve their reversibility.
V₂O₅-P₂O₅-Fe₂O₃-Li₂O glasses were prepared by using the melt quenching method. The glass-ceramics were produced by heat treatment at 375 degree C for 2 hours in air. From X-ray diffraction, Li_xV₂O₅ crystal was confirmed as precipitated phase and the degree of crystallinity was approximately 90%.
The charge-discharge performance of their glass-ceramics cathode showed the total capacity of 330-340Ah/kg at 1/20C rate for 1.5-4.2V cutoff ranges. It is 10% higher than the capacity of the glass cathode in the same composition. Moreover, the cycleability of the glass-ceramics cathode was almost same as the glass cathode. These results show that glass-ceramics is potential candidate for lithium ion cathode materials.
[1]D. B. Le et al, Chem. Mater. 10, 682 (1998). [2]C. Delmas et al, Solid State Ionics 69, 257 (1994). [3]Y. Sakurai et al, 132, 512 (1985).

LiNi0.5Mn1.5O4 (LNMO) is an electrode material for future high voltage lithium ion batteries as it shows a high potential of 4.7 V vs. Li/Li+. However, the high potential is not only beneficial as electrolyte decomposition of common carbonate based electrolytes is promoted in this potential range, going along with degradation of the whole cell. To get deeper insight into this mechanism, LNMO thin film electrodes are prepared by pulsed laser deposition (PLD) to prepare a model system which enables study of the degradation product layer between cathode surface and electrolyte, being the so-called cathode electrolyte interface (CEI). Aim of this study is to investigate this surface film with regard to stability, composition, thickness and formation conditions. Ways to prevent the electrolyte degradation as e.g. by deposition of a surface coating on the LNMO thin film to prevent direct electrolyte contact are also investigated.
Main characterization tool is time-of-flight secondary ion mass spectrometry (ToF-SIMS). As depth and mass resolution in ToF-SIMS analysis are the better the flatter is the sample under investigation, main optimization purpose of the LNMO thin films is the reduction of surface roughness. Therefore LNMO was deposited on yttria-stabilized zirconia single crystals (YSZ) covered with platinum, also deposited by PLD, as current collector. This substrate shows a strongly reduced roughness in comparison to common used metal foils. A roughness of the LNMO films of only about 10 nm was reached.
ToF-SIMS depth profiling reveals a stacked structure of the CEI, consisting fluorine containing species due to conducting salt decomposition on the electrolyte side of the layer, followed by an organic, partially polymeric region and thereafter a lithium containing region with e.g. LiCO3 species, after which inorganic species are found. On the LNMO side of the layer inorganic transition metal containing species, resulting from partial dissolution of these ions out of the LNMO are located.
Application of an about 100 nm thick LiPON coating on LNMO electrodes as protection layer indeed reduces transition metal dissolution into the electrolyte.

To significantly increase the energy density of lithium-ion batteries, it is necessary for the reaction to exceed more than one electron per transition metal, e.g. Mg2+ or 2Li+. One of our focus materials is epsilon-VOPO4. This material adopts a stable 3D tunnel structure with a theoretical specific capacity of ~158 mAh/g (for LiVOPO4) and over 300 mAh/g when Li2VOPO4 is formed. This material possesses both a higher free energy of reaction and a higher electronic conductivity than LiFePO4 (1*10-6 S/cm vs. 1*10-10 S/cm of LiFePO4), and a greater possibility of oxidation state variation. Our earlier studies suggested that epsilon-VOPO4 might allow more than one lithium ion to participate in the electrochemistry, but little was known about its reversibility. We used in-situ and ex-situ synchrotron X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and magnetic properties to understand the electrochemical behavior of epsilon-VOPO4. Our results suggest that it is possible to cycle reversibly over hundreds of cycles more than one Li ion per redox center, but that the reaction pathways are not simple but differ on discharge and charge. VOPO4 and its related materials appear to be promising candidates for the next generation of Li batteries. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Basic Energy Sciences under Award Number DE-SC0001294.

A solid-state method has been utilized to synthesize LiV₃O₈ cathode material for application in the lithium ion batteries. In the reaction, LiOH and NH₄VO₃ were used as starting materials to yield a precursor LiVO₃ followed by calcining to obtain the product LiV₃O₈ at 500^oC and 600^oC for 6h. The LiV₃O₈ prepared was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The crystallinity, size, and morphology of LiV₃O₈ are dependent on the calcined temperature. The product has nanorod crystallite structure composed of uniform particles with diameters ranging from 30 to 120 nm. The electrochemical properties of LiV₃O₈ were examined by cyclic voltammetry, impedance spectroscopy, and galvanostatic cycling. We evaluated the effect of alternative current collectors on the electrochemical properties of LiV₃O₈. In our study, the results reveal that LiV₃O₈ is a promising cathode material for lithium ion batteries.

We have investigated the effect of Al dopant on the electrochemical, structural and thermal characteristics of LiNi1-xCo0.10AlxO2 (0 le; x le; 0.13) cathode materials that were synthesized by the surface coating with aluminum acetate on the Ni0.89Co0.11(OH)2 precursor and followed calcination with LiOH H2O. From XRD data, obtained samples were indexed based on the α-NaFeO2 layered structure with space group R-3m. No impurity peaks are observed except for x=0.13, in which LiAlO2 and impurity phases are observed. Rate capability tests were performed up to 10C rate, and LiNi0.81Co0.10Al0.09O2 sample with a primary particle size of ~250 nm showed the best rate capability with a discharge capacity of 155 mAh g-1 at 10 C with a cut-off voltage range between 3 and 4.5V. At elevated temperature (60°C), the cycling performance of LiNi0.81Co0.10Al0.09O2 sample showed a discharge capacity of 122 mAh g-1 with capacity retention of 59%.

Three-dimensional (3-D) composite electrodes are prepared by one-step sintering of the laminated LiCoO2 and 0.44 LiBO2- 0.56 LiF pellets, in which the amorphous 0.44 LiBO2- 0.56 LiF solid electrolyte melts during the sintering process and fills the interspace in the underlying highly conductive 3-D frame formed by LiCoO2. The specific capacity of the 3-D composite electrode is dependent on the thickness of the composite electrodes. The 100-mu;m-thick 3-D composite electrode delivers a specific discharge capacity of 131 mAh/g, which is 96% of the theoretical capacity of LiCoO2 (137 mAh/g). The 200-mu;m-thick 3-D composite electrode delivers 88% of the theoretical capacity, i.e., 120 mAh/g, and a significantly enhanced surface capacity of ~9 mAh/cm2, which is much higher than the surface capacity of the electrode used in the previous all-solid-state lithium battery. Given the low sintering temperature and the amorphous nature of 0.44 LiBO2- 0.56 LiF solid electrolyte, this one-step sintering approach may be readily applied to other cathode systems.

Due to their high energy density and long cycle life, lithium-ion batteries have rapidly become the dominant power sources for portable electronic devices, electric vehicles and energy storage systems. However, safety issues still prevent full utilization of these batteries. The high flammability of the organic solvents used in common liquid electrolytes can lead to fires and explosions when short circuits or local overheating accidentally occurs. In this respect, a lot of studies have focused on the preparation and characterization of gel polymer electrolytes. However, the host polymers lose mechanical strength when plasticized by organic solvents. In order to obtain the gel polymer electrolytes with improved electrical and mechanical properties, ceramic fillers such as SiO2, Al2O3 and BaTiO3 have been incorporated into host polymers. In our previous studies, the core-shell structured SiO2 particles containing lithium ions in their shell were synthesized and used as functional fillers in Li+-conducting composite polymer electrolytes [1,2]. These fillers have a very uniform spherical shape, and the SiO2 core is covalently bonded to poly(lithium 4-styrenesulfonte) in the shell layer. In this work, we report the synthesis and electrochemical characteristics of composite polymer electrolytes based on core-shell structured SiO2 nanoparticles with controlled morphology. The composite polymer electrolytes exhibit high ionic conductivity, good mechanical strength for thin film preparation and favorable interfacial characteristics. We demonstrate that the composite polymer electrolytes containing core-shell SiO2 nanoparticles are very promising electrolyte materials for high performance lithium-ion polymer batteries.
References
[1] Y.S.Lee, S.H.Ju, J.H.Kim, S.S.Hwang, J.M.Choi, Y.K.Sun, H.Kim, B.Scrosati, D.W.Kim, Electrochem. Commun., 17, 18 (2012).
[2] Y.S.Lee, J.H.Lee, J.A.Choi, W.Y.Yoon, D.W.Kim, Adv. Funct. Mater., 23, 1019 (2013).

All solid-state lithium ion battery is recognized as next-generation technology for rechargeable power source, because of improved safety, high energy density, and long cycle life. It is essential to develop stable inorganic solid electrolytes with high lithium ion conductivity for fabricating all solid-state lithium ion batteries. Many solid electrolyte materials have been proposed and investigated. Lithium lanthanum titanium oxide (LLTO) with a high ionic conductivity is a promising candidate. A number of research efforts have been focused on crystalline LLTO, which is not stable with Li. However, amorphous LLTO which is stable in contact with Li metal is still lacking. In this study, LLTO thin film for all solid-state lithium ion batteries was successfully prepared by sol-gel process. A lithium alkoxide, a lanthanum alkoxide, and a titanium alkoxide were employed to prepare LLTO precursor. The LLTO precursor was coated on an Al2O3 single crystal substrate to form a precursor layer which was then heat-treated. The thin film electrolytes were characterized by SEM and XRD. SEM images showed that the thin film is smooth and without cracks. XRD results indicated that the thin film is amorphous. The impedance spectroscopy measurement of the amorphous LLTO thin film was performed at temperatures from 30C to 90C with 20C increments over the frequency range from 0.01Hz to 200 KHz using a 500 mV ac signal using Bio-Logic VMP3. The d.c. ionic conductivities were determined from complex plane plots of the impedance of the amorphous LLTO thin film.

During a couple of years, Liminus;air or Li-Oxygen (Li-O2) battery has been intensively shed light on as a potential energy storage thing for high power applications such as transportation and stationary energy storage systems because of its high specific energy density, however, unfortunately its practical application is limited by a low current density, a low energy efficiency, and a poor cycle ability. Of course all of these problems are complicatedly related with each battery component- electrolytes, electrolyte salts, and electrocatalysts, binders, and carbon materials in the air electrode.
Among them, many researchers have specifically focused on electrolytes and materials about air electrodes such as electrocatalysts and carbon materials. However, despite such struggling efforts, we still have many ambiguous points to have to be elucidated and be overcome for making a ‘real&’ rechargeable Li-O2 battery. To make such a ‘real&’ rechargeable Li-O2 battery, we need to understand and study relationship between each component. To achieve it, first of all we have to fix the air electrode which is stable during cycling for understanding the other components such as electrolytes, salts or binders, and by extension to modify a lithium anode. For this reason, in this paper we suggest a carbon and a binder free cathode made by simple electroless deposition method which is not changeable during long cycling for Li-O2 battery and hope that it will provide a new possibility of air electrode and give any little help for improving Li-O2 battery field.

Abstract
The need for higher energy density and longer cycle life for rechargeable lithium (Li) batteries creates intensive interest for alternative electrode materials with higher gravimetric capacity and stability. Sulfur (S) as a cathode material is considered as one of the most promising candidates based on its much higher theoretical gravimetric capacity, 1672 mAh/g, compared to the traditional transition metal oxide cathodes, ~200 mAh/g1 [1]. The formation of electrically isolative Li2S/Li2S2 may suppress the dendrite formations [2]. One of the most challenging problems in the development of Li-S batteries is the dissolution of polysulfides, the intermediate products of the discharge reaction, in the organic solvent-based electrolytes. It leads to irreversible losses of the electrochemically active S, high overcharge and poor coulombic efficiency (CE).
In this project we formed a thin conformal Li-ion permeable oxide layer on the sulfur-carbon composite electrode surface by rapid plasma enhanced atomic layer deposition (PEALD) in order to prevent this dissolution, while preserving electrical connectivity within the individual electrode particles. The advantage of ALD methods is the very high degree of coating conformity on three dimensional (3D) porous substrates due to the surface-controlled nature of chemical reactions [3]. The oxide thickness is precisely controlled by the number of second-long precursor deposition / oxidation cycles. In contrast to thermal ALD, commonly employing H2O vapors for oxidation, oxygen plasma is utilized as the oxidant in PEALD. Advantages of PEALD include lower (down to 20 °C) deposition temperature, more uniform coatings and faster deposition rates. If an electrode contains water-soluble binder, PEALD on the electrode surface avoids undesirable binder swelling. After PEALD of a thin layer of aluminum oxide on the surface of electrode composed of large (~10 µm in diameter) S-infiltrated activated carbon fibers (S-ACF), we observed significantly enhanced cycle life with a capacity in excess of 600 mAh g-1 after 300 charge-discharge cycles [4].
Acknowledgements
Different aspects of this work were supported by the EE&R program of the KETEP (grant 20118510010030) and by the US ARO (grant W911NF-12-1-0259).
References
[1] aD. Aurbach, Y. Gofer, J. Langzam, Journal of the Electrochemical Society 1989, 136, 3198-3205; bL. Gireaud, S. Grugeon, S. Laruelle, B. Yrieix, J. M. Tarascon, Electrochemistry communications 2006, 8, 1639-1649.
[2] aV. Kolosnitsyn, E. Karaseva, Russian Journal of Electrochemistry 2008, 44, 506-509; bH. Kim, J. T. Lee, G. Yushin, Journal of Power Sources 2012.
[3] aS. Boukhalfa, K. Evanoff, G. Yushin, Energy & Environmental Science 2012, 5, 6872-6879; bJ. Benson, S. Boukhalfa, A. Magasinski, A. Kvit, G. Yushin, Acs Nano 2012, 6, 118-125.
[4] H. Kim, J. T. Lee, D. C. Lee, A. Magasinski, W. i. Cho, G. Yushin, Advanced Energy Materials 2013.

The rareness and uneven distribution of lithium minerals make Li-ion batteries uneconomical as a large-scale off-peak power. Recently, efforts start to shift to ambient sodium-ion batteries (SIBs) owing to the abundance of sodium. Significant progress has been made on cathodes of SIBs. However, highly reversible anodes in SIBs remain a significant challenge. Carbonaceous anodes in SIBs are promising due to low operating potential, relatively high capacity, and abundance. A few carbons, including PAN-based carbon fibers, carbon black, and carbon microspheres, have been investigated. They often deliver capacities of 100-300 mAh/g at low discharge/charge current rates with limited cycle lives. Most recently, nanostructured carbons have also been explored as anodes for SIBs, and showed promising performance in rate capability. Dahn et al. first demonstrated that hard carbons exhibit good Na-ion storage capacity as anodes for SIBs. Hard carbons can be formed by pyrolysis of different precursors, such as sucrose, polymer and cellulose. Cellulosic substances are most promising candidates due to their low cost, wide availability and renewability.
Herein, we demonstrate a novel hard carbon nanofibers (CNFs) derived from cellulose nanofibers with superior reversible capacity (above 250 mAh/g at 40 mA/g), good rate capability (85 mAh/g at 2000 mA/g), and excellent reversibility (176 mAh/g over 600 cycles at 200 mA/g). Importantly, the de-insertion capacity below 1.0 V, the practically useful part in a full cell, contributes 90% of the whole de-insertion capacity. The excellent performance of the CNFs can be attributed to its hard carbon nature and one dimensional (1D) nanostructure. The unique morphology facilitates rapid ion migration and plenty of contact area between the electrode and the electrolyte in SIBs applications. Considering the low cost, simple synthesis and great performance, CNFs can be a promising anode for large-scale applications of SIBs.

The development of rechargeable lithium-air batteries represents an important pathway towards green energy storage. Some of the main problems concerning rechargeable lithium-air batteries include the lack of effective catalysts that reduce the overpotentials for the oxygen reduction reaction and oxygen evolution reaction and the associated electrolyte decomposition in the air cathode. This presentation will discuss recent findings in a study of some binary and ternary alloy nanoparticles catalysts prepared by nanoengineered synthesis and processing methods. These nanoalloys were examined as the cathode catalysts in a single-cell lithium-oxygen battery. In addition to determining the discharge-charge characteristics and discharge capacities, electrochemical measurements were also performed to assess the mechanistic details for the formation of lithium peroxide or superoxide on the cathode materials and issues related to electrolyte decomposition reaction. The synergy of the transition metals in the nanoalloy in affecting the discharge/charge overpotentials and the discharge capacity will also be discussed. The finding has important implications to the rational design of catalysts for rechargeable lithium-air batteries.

The all-vanadium redox flow battery (VRFB) has attracted considerable attention due to its advantages, such as long cycle life, high efficiency, flexible design and environmental benignity, considered as promising candidate for energy storage application combined with intermittent power sources. Unlike conventional secondary batteries, energy bearing species are not stored within an electrode structure but in separate liquid reservoir and pumped into flow cell when energy is transferred. In contrast solid active materials, charge and discharge reactions in VRFB are based on entirely the redox reactions between soluble ionic species. The redox reaction of V2+/V3+ and VO2+/VO2+ occurs on the surface of commonly used graphite felt electrode. However, the graphite felt electrodes were proved to show poor kinetic reversibility. Therefore, much attention has been paid to the modification of the electrode materials.
In this regards, we investigated the synergistic effect of the carbon nanotubes (CNTs)/carbon nanofibers (CNFs) hybrid catalysts used as VRFB electrodes. CNT/CNFs grown electrodes with enhanced electron transfer and well-developed edge plane active sites for vanadium redox couple were synthesized on the carbon felt via simple acetylene (C2H2) vapor deposition method at different growth temperatures utilizing nickel (Ni) nanoparticles as catalysts. Surprisingly, the as-prepared CNT/CNF electrode demonstrated better capacity retention and excellent rate capability up to 100mA cm-2 with significantly improved electron transfer and lower polarization. Furthermore, at a current rate of 100 mA cm-2, the high voltage efficiency of 67.5% on CNT/CNF-700 sample compared with that on 42.1% at pristine one was achieved. The energy efficiency was highest on CNT/CNF-700 electrode, which is in the order 85, 79, 73 and 66% at a rate of 40, 60, 80 and 100mAcm-2, respectively, compared to that on pristine one in the order 73, 61, 46 and 41% at the same current rate. Such results were due to the formation of large edge plane defect of CNF walls and fast electron transfer at basal plane of CNT walls. By using CNT/CNFs hybrid electrode, the battery efficiency and rate capability can be expected to be enhanced in VRFB system

Citrate is a biological chelanting agent that is released by the roots of all vascular plants. Also, is a component of many foods and pharmaceuticals and is used in technological applications requiring an environmentally benign chelating agent or dissolution agent, for instance, for cleaning circuit boards.
Citrate behavior in heterogeneous systems where adsorption ligand-assisted dissolution reactions are predominant have received the most attention.
Manganese dioxide with its low cost, friendly environmental and richness in nature has been investigated to be a promising candidate as supercapacitor material. It has been prepared by many different methods such as hydrothermal synthesis, sol-gel, thermal decomposition, coprecipitation, eletrochemical deposition and son on. To the best of our knowledge, it has not been reported that using citric acid as biological chelanting and as a dispensant agent to synthesis manganese dioxide. Futhermore, MnCl2*4H2O is the only one starting manganese precursor in our approach. The organic chelanting used here has the merits of simple steps, less sample consumption and high yield, which are advantages when considered for commercial purposes.
Manganese dioxide sol has been prepared using citric acid as chelanting agent. After the complexation reaction, the product was left under bubbling process by 3hs using O2. Then, the suspension was splitted using a centrifugation membrane at 4000 rpm. The solution part was analyzed in Inductively Coupled Plasma (ICP) in order to determinate the concentration. Moreover, the sol was dialyzed and stabilized. Finally, the concentration in terms of particle and in terms of total manganese was determinated.

Transparent and flexible electronics are the promising devices for the near future. These include multifunctional portable electronics, cell phones, electric books and wearable PCs. Elements of the novel electronic devices that are transparent and flexible have been fabricated including transistors, optical circuits, displays, touch screens, and solar cells, for various applications. However, such devices have not been realized, because the practically reliable energy storage system with transparency and flexibility have not yet been developed.
Supercapacitors, as one of the energy storage devices, can be an alternate system to solve these stability and safety issues. Compared to batteries, this system has considerable potential for power density and device reliability. Also, many studies concerning the production of thin-film supercapacitors have already been reported, which could enable highly flexible systems to be fabricated. Therefore, in combination with a high electrochemical performance, supercapacitors appear to be an ideal energy storage system for use in fully integrated, transparent and flexible electronic devices.
Here, new concepts are reported for the realization of transparent (transparency ~ 50 %) and flexible (bending radious ~ 1.5 mm) energy storage systems that are unavailable upto now. The technological basis for the transparent and ultra-bendable supercapacitors is proposed and proves the excellent performances showing even at compressive and tensile deformation states. This prototype system, built on interdigitated grid type electrodes, constitutes significant advances over existing methodology for transparent electrodes for supercapacitors in terms of capacitance (~405 F g-1) and the flexibility because the system is possible to circumvent percolation problem.

We have done extensive work on ruthenium oxide ‘RuO2&’-graphene composite materials for supercapacitor applications. However, the cost of RuO2 has been an issue for use in large scale production of supercapacitors. This research project focuses on novel and cost effective graphene MnO2-(G) novel composite materials. The MnO2 and MnO2-(G) and the corresponding nanomaterials were synthesized by the sol-gel technique, and characterized by using Scanning Electron Microscopy (SEM), Raman spectroscopy, X-ray-diffraction, and Transmission Electron Microscopy (TEM) and other electrochemical techniques. The charging-discharging, cyclic voltammogram stability and the life cycle of the various MnO2 and MnO2 materials were studied in various supercapacitor configurations. The higher specific capacitance and stable number of charging-discharging cycles in MnO2-(G) are analyzed to better understand the electrochemical properties of the graphene-metal oxide based supercapacitors. On the basis of our findings, the MnO2-(G) material is very promising for use in supercapacitor applications.

Silicon (Si) as anode material for Li-ion batteries (LIBs) has the highest theoretical capacity of about 4200 mAhg^-1, which is ten times higher than that of commercial graphite anode. However, Si anode exhibits intrinsic drawback of large volume expansion (>300%) and pulverizing of the electrode during the Li alloying/dealloying processes, leading to the poor conductivity and a rapid capacity fading during repeated cycling. To overcome these problems, graphene, a 2D carbon material with superior electrical conductivity and instinct mechanical strength, has been reported to improve electron transport in Si anode and to effectively alleviate the volume change and aggregation of Si atoms upon charge-discharge cycling. But, since graphene is prone to restack to form graphite, it is difficult to achieve a balanced morphology. Therefore, graphene cannot form a structure of interconnected networks that maintain good structural stability during repeated cycling. Keeping these problems in mind, in this work we introduce the novel electrode system of ternary nanocomposites consist of Si-Mn alloy in graphene. Si-Mn alloy acts as an active-inactive matrix and was prepared by mechanical mixing of the components. In this composite, Mn serves as inactive component which functions as a buffer to reduce the mechanical stress caused by the volume change of Si during cycling. Moreover, the optimized composition reduces agglomeration of Si-graphene composite during repeated cycling. As a result, the novel Si-Mn-graphene ternary nanocomposites as an anode in LIBs achieve the significantly improved reversible capacity and steady cycleability. We expect that this study could be extended to other ternary nanocomposites as anode materials of LIBs anodes with highly enhanced electrochemical performance.

As technology advances energy storage is becoming a very big issue. One of the main areas of research has been in Lithium Ion batteries, since they are lighter, more powerful and have better long-term stability than the previous battery chemistries. The addition of graphene in the anode of Lithium Ion batteries has proven to be an effective means of increasing energy storage capacity as well as long-term cyclical stability. Currently research is being conducted to develop anode materials using nanocomposites with much higher theoretical capacities than the 372 mAh/g of the standard graphite anode. One of the most promising anode materials being researched is molybdenum in the forms of MoO2 and MoS2, which in their bulk forms have theoretical capacities of 838 and 670 mAh/g, respectively.
We have synthesized a novel anode for use in a rechargeable Lithium Ion battery containing Mo and graphene based nanocomposites material. The anode materials have been characterized by using Scanning Electron Microscope, Tunneling Electron Microscope, X-ray diffraction and FTIR measurements techniques. The charging discharging, cyclic voltammetry and impedance measurement on the Mo-graphene nanocomposite based anode material has been studied. The anode based on Mo-graphene shows a higher energy storage capacity retaining a higher energy storage capacity for more cycles than either the Mo or graphene alone.

The electrochemically exfoliated few-layer graphene sheets have been applied to wrap the commercially available cathode material cLFP. The incorporation of low weight percent (2 wt%) of graphene in cLFP is able to deliver a capacity of 208 mAh g-1 which is beyond the theoretical 170mAh g-1 without causing obvious voltage polarization. The extra capacity is mainly attributed to the reversible redox reaction between the lithium ions of the electrolyte and the graphene flakes. The facial and scalable process of electrochemically exfoliated few-layer graphene makes the new cathode feasible for large scale manufacture.
Reference:
[1] C. Y. Su et al. High-quality thin graphene films fast electrochemical exfoliation. ACS Nano, 5, 2332 (2011)
[2] L.-H. Hu et al. Graphene-modified LiFePO4 cathode for lithium ion battery beyond theoretical capacity, Nature Communications, 4:1687 (2013)

Reciprocal salt flux methods have been used to prepare olivine single crystals which are either stoichiometric or Fe-rich based on their position within the Li-Fe-PO₄-Cl phase space. Single crystal X-ray diffraction and single crystal neutron diffraction studies carried out on a large selection of single crystal growth products indicate that the as-grown crystals typically have very low defect concentrations (stoichiometric within detection limit of ~0.2%). However, crystals prepared from Fe-rich fluxes are found to contain excess Fe which is conclusively demonstrated to be present in the form of sarcopside type defects rather than as anti-site defects, leading to a general formula of (Li_1-2xFe_x)FePO₄ which forms along the line connecting olivine LiFePO₄ and sarcopside Fe₃(PO₄)₂ in the Li-Fe-PO₄ phase diagram. These sarcopside-type defects represent an actual thermodynamically stable solid solution associated with olivine LiFePO₄, and are therefore expected to be present in every preparation of olivine which is Fe-rich relative to the ideal olivine stoichiometry. Although the presence of sarcopside defects leads to a continuous increase in unit cell lattice parameters, transmission electron microscopy studies show that these defects are distributed very inhomogenously throughout the single crystal samples.

There is great interest in developing novel anode materials for high-performance Li-ion batteries, which are the key parts of electric vehicles and grid energy storage. Many researchers have focused in recent years on resolving the crucial problem of capacity fading in Li-ion batteries when carbon anodes are replaced by other IV-elements (Si, Ge, or Sn) with much higher capacities. Some progress was achieved by using different nanostructures. However, obtaining longer stability via a simple process remains challenging. Here we report our recent progress in development of novel high-performance anode materials, including a nanostructure of amorphous hierarchical porous GeOx, new phases of FeSn5 and CoSn5.
Acknowledgements: This work is supported by the Project of the Ningbo 3315 International Team of Advanced Energy Storage Materials and the Project of Li Ion Batteries of the Nano Pilot Program of Chinese Academy of Sciences.

The great need of effective energy storage devices in portable consumer electronics, electric vehicles and grid storage has directed the research and application interest in high power device development. Silicon is one of the most abundant components on earth and the most promising alloy-type anode materials for Li-ion batteries due to its high specific capacity. We prepared free-standing, flexible and conductive nanofibrillated cellulose (NFC) paper which constitutes silicon nanoparticles (SiNPs) and conductive carbon by a simple filtration of aqueous dispersions of NFC and SiNPs. We demonstrated that such lightweight and flexible Si-conductive nanopaper structure performs well as Li-ion battery anodes due to an excellent ion accessibility in the electrode triggered by the porous nature of NFC paper. Moreover, the volume expansion of silicon could be compensated in the 3D NFC network. The stable capacities ranging between 900-1200 mAh/g for longer cycles in half-cells was achieved. Such flexible and self-standing anodes based on earth abundant materials such as silicone and cellulose could show a new potential for low-cost energy storage devices.

In the context of enhancing lithium-ion batteries (LIB) performances in both terms of lifetime and energy density, silicon appears as a promising anode material due to its high theoretical specific capacity (up to 3580 mAh.g-1) and its low discharge potential relative to Li+/Li. However, huge volume change of LixSiy alloys induces poor cycling stability and rapid capacity fading due to cracking effects. This effect can be partially counteracted by decreasing the silicon to the nanosize where mechanical effects appear less severe and/or by limiting the expansion using a protecting shell.
In a two reaction steps configuration, core-shell silicon carbon nanoparticles (Si@C NPs) can be synthesized using the laser pyrolysis technique. The reactor is composed of two successive reaction zones: silicon cores are synthetized at the first stage and the carbon coating is realized at the second. Therefore the Si core was not exposed to air before shell deposition. Moreover the formation of silicon carbide, which is very detrimental to electrochemical properties, was avoided. Silane was used as silicon precursor of the core and ethylene as carbon precursor of the shell. In this configuration, we can control the core diameter in the range 20 to 100 nm, the core organization (amorphous or crystalline), the shell thickness and the size distribution of NPs.
Electrodes were prepared with these Nps and tested in coin cell configuration versus lithium foil. Using pure 100 nm diameter silicon, we confirm that reducing the size (by comparison with a commercial grade of Si, 200 nm diameter) leads to a better stability of the electrode. Furthermore, 100 nm diameter Si@C Nps with different carbon shell thicknesses exhibit a great improvement in stability, up to 500 cycles at a limited alloying capacity of 1000 mAh.g-1 (more than three times higher than commercial graphite material). Finally, 20 nm diameter Si@C Nps were synthesized with the same experimental conditions. Reference pure Si Nps were also synthetized without using the second reaction zone. From these NPs, batteries were elaborated and tested. Within this NPs size range, the beneficial effect of the carbon shell is also observed compared to pure Si. Without the carbon shell, half of the capacity is lost after 40 cycles while a good stability and high capacity (higher than 3400 mAh.g-1) is observed in the batteries elaborated from Si@C material. The origin of this beneficial effect will be discussed by comparison with literature.

Bulk crystalline silicon is known to undergo colossal volumetric changes during electrochemical alloying (charging) and de-alloying (discharging) processes in a rechargeable lithium-ion battery. This leads to pulverization of the active material resulting in loss of electrical contact with the current collector causing rapid decrease in capacity and consequent failure of the battery. Silicon nanotubes have attracted great attention as a stable anode system for lithium-ion battery due to their ability to provide strain relaxation upon the huge volumetric changes leading to enhanced cyclability and capacity retention. However, synthesis of these nanotubes on a large scale has been a challenge. In this work, we propose a low cost approach wherein, large quantities of a sacrificial nano-wire template (SNTs) were synthesized using inexpensive precursors in a hydrothermal reactor. Amorphous silicon (a-Si) was then deposited on these nanowires in a chemical vapor deposition (CVD) reactor by thermal cracking of silane (SiH4). The obtained a-Si/SNTs core-shell structure was then dissolved to obtain large quantities of hollow silicon nanotubes. These hollow silicon nanostructures exhibit a high first discharge capacity of ~2420 mAh/g at a current density of 300 mA/g when cycled in the voltage range 0.01-1 V vs. Li+/Li. The active material loadings utilized in our studies is ~50 fold higher than currently reported literature values indicating the promising nature of the approach and the hollow nanoscale architectures. A first cycle irreversible loss of ~24% was observed due to the expected SEI formation owing to the large surface area of the silicon nanotubes. At high current rates (2A/g), the silicon nanotubes exhibit capacities in the range 1300-1700 mAh/g with capacity retention of 88% at the end of 50 cycles corresponding to a capacity fade of 0.23% loss per cycle. These nanostructures exhibiting high specific capacity and cyclability are developed using a cost effective and scalable approach enabling them to be a promising silicon based anode system for the next generation of lithium-ion batteries. Promising synthesis, structure, microstructure and electrochemical results of these novel hollow a-Si nanotubes will be presented and discussed.

Recent experimental results suggest that silicon suboxides (SiOx, x < 2) can be a promising anode material for high performance lithium-ion batteries (LIBs), especially when the oxygen content is relatively low. Very recently, Mullins and coworkers reported that nanostructured Si thin films with homogeneous O incorporation (< 18 at. % O) were able to deliver an excellent capacity (asymp;2200 mAh/g) and maintain 80 % of the initial reversible capacity even after 300 cycles. Despite the encouraging improvements, the atomistic mechanisms underlying the lithiation of Si-rich oxides remain a puzzling question. In this talk we will present the lithiation behavior in partially oxidized Si at the atomistic level based on density functional theory calculations of the structure, mechanical property, bonding mechanism and energetics of lithiated a-SiO1/3. Our results show that Li atoms can be favorably accommodated by both Si and O atoms. Interestingly, with lithiation, the Si-Li coordination number (CN) is found to monotonically increase up to CNSi-Li asymp; 10 in a-Li4SiO1/3, whereas CNO-Li tends to saturate at 6 far before full lithiation, resulting in the formation of Li6O complexes with a unique Oh symmetry. The formation of intriguing Li6O complexes is a new and interesting finding, unlike commonly observed Li2O or other Li-silicates in lithiated SiO or SiO2. The interplay between Li-Si and Li-O interactions facilitates favorable Li incorporation with competitive capacity relative to pure Si. The lithiation voltage for a-SiO1/3 is predicted to be around 0.2minus;0.8 V, which is within the desirable range for LIB anode application but slightly higher than that of pure Si, the up-shift in voltage profile reflects the more energetically favorable incorporation of Li in a-SiO1/3. Our study highlights the importance of tuning O concentration and spatial distribution in order to maximize the performance of Si suboxide-based anodes.

The study of interfacial properties, and especially of their change upon lithiation, is a fundamentally challenging and significant topic in designing heterogeneous nano-structured electrodes for lithium ion batteries. This issue becomes more intriguing for Si electrodes, whose ultrahigh capacity is accompanied by large volume expansion and mechanical stress, threatening with delamination of silicon from the metal current collector and failure of the electrode. Instead of inferring interfacial properties from experiments, in this work, we have combined density functional theory (DFT) and ab-initio molecular dynamics (AIMD) calculations with Time-of-Flight secondary ion mass spectrometry (TOF-SIMS) measurements of the lithium depth profile, to study the effect of lithiation on the a-Si/Cu interface. Our results clearly demonstrate Li segregation at the lithiated a-Si/Cu interface (more than 20 % compared to the bulk concentration). The segregation of Li is responsible for a small decrease (up to 16 %) of the adhesion strength, and a dramatic reduction (by one order of magnitude) of the sliding resistance of the fully lithiated a-Si/Cu interface. Our results suggest that this almost frictionless sliding stems from the change of the bonding nature at the interface with increasing lithium content, from directional covalent to uniform metallic. These findings are an essential first step toward an in-depth understanding of the role of lithiation on the a-Si/Cu interface, that may contribute in the development of quantitative electrochemical mechanical models and the design of non-fracture-and-always-connected heterogeneous nano-structured Si electrodes.

The surface reactions of electrolytes with a silicon anode in lithium ion cells have been investigated. The investigation utilizes two novel techniques which are enabled by the use of binder free silicon (BF-Si) nano-particle anodes. The first method, Transmission Electron Microscopy (TEM) with Energy Dispersive X-ray Spectroscopy (EDX), allows straightforward analysis of the BF-Si solid electrolyte interphase (SEI). The second method, utilizes Multi-Nuclear Magnetic Resonance (NMR) spectroscopy of D2O extracts from the cycled anodes. The TEM and NMR data are complemented by XPS and FTIR data, which are routinely used for SEI studies. Coin cells (BF-Si/Li) were cycled in electrolytes containing LiPF6 salt and ethylene carbonate (EC) or fluoroethylene carbonate (FEC) solvent. Capacity retention was significantly better for cells cycled with LiPF6/FEC electrolyte than for cells cycled with LiPF6/EC electrolyte. Our unique combination of techniques establishes that for LiPF6/EC electrolyte, the BF-Si SEI continuously grows during the first 20 cycles and the SEI becomes integrated with the BF-Si nano-particles. The SEI predominantly contains lithium ethylene dicarbonate (LEDC), LiF, and LixSiOy. BF-Si electrodes cycled with LiPF6/FEC electrolyte have a different behavior; the BF-Si nano-particles remain relatively distinct from the SEI. The SEI predominantly contains LiF, LixSiOy and an insoluble polymeric species.

Diffusion induced stress is believed to be one of the major driving forces responsible for the mechanical degradation especially for Si based electrode materials with high capacity in lithium ion batteries. On the other hand, due to the coupling effect, stress can also affect the diffusion and therefore change the cycling efficiency, which is not fully understood. In this talk, we will first introduce how to in situ characterize diffusion induced stress, combining the in-situ optical observation of crack generation and propagation in a Si thin film electrode. Based on the understanding from the model system, we will then discuss different approaches to tailor the nanostructure accordingly to mitigate the mechanical degradation of the Si electrode to improve its capacity retention and cyclic life, including designing Si nanostructure to accommodate stress relaxation and applying surface coatings to modify the stress gradient and provide an energy barrier for crack nucleation.

Silicon is a promising anode material in lithium batteries due to its high specific capacity and low operation voltage. The major concern in using Si-based anodes is the huge volume expansion and continuous solid-electrolyte interphase formation during the lithiation that leads to a fast degradation of the electrode material and a reduced life cycle of the battery with limited use in real life Li-ion applications. In this talk we report an approach to roll out Li-ion battery components from silicon chips by a continuous and repeatable etch-infiltrate-peel cycle. Vertically aligned silicon nanowires etched from silicon chips are captured in a polymer matrix that operates as Li-ion gel-electrolyte and electrode separator and peeled off to make multiple battery devices out of a single chip. Porous, electrically interconnected copper nanoshells are conformally deposited around the silicon nanowires to stabilize the electrodes over extended cycles and provide efficient current collection. Using this process we demonstrate an operational full cell 3.4 V lithium-polymer silicon nanowire battery which is mechanically flexible and scalable to large dimensions [1]. The influence of the metal shell morphology and thickness on swelling and fracture modes of the crystalline silicon nanowire core are also investigated. Above a critical metal shell thickness, anisotropic swelling and fracturing during lithiation of crystalline silicon are suppressed. In order to get better insight into the observed deformation patterns, we implemented a continuum model that couples lithium transport and large, inelastic deformations. Simulated morphological changes of the silicon nanowires are in good agreement with experimental observations [2]. Optimized core-shell structures show enhanced rate performance and capacity retention (less than 5% capacity loss after 150 cycles).
[1] A. Vlad et al., Proc. Natl. Acad. Sci. USA 109, 15168 (2012).
[2] A. Vlad et al., in preparation.

Silicon is emerging as a very attractive anode material for lithium ion batteries due to its low discharge potential, natural abundance, and high theoretical capacity of 4200 mAh/g, more than ten times that of graphite (372 mAh/g). This high charge capacity is the result of silicon&’s ability to incorporate 4.4 lithium atoms per silicon atom; however, the incorporation of lithium also leads to a 300-400% volume expansion during charging, which can cause pulverization of the silicon material and loss of electrical contact between the silicon and current collecting substrate. The architecture of the anode must therefore be able to adapt to this volume increase. Here we present a low cost, high-rate, and scalable process for constructing silicon anodes using directed assembly techniques to create a layered carbon nanotube and silicon nanoparticle structure. This layered architecture increases the surface area available for electrochemical reactions, and also provides a conductive path to the current collecting substrate.

The Li-rich, Mn-rich (LMR) layered structure materials exhibit very high discharge capacities exceeding 250 mAh g-1 and are very promising cathodes to be used in lithium ion batteries. However, significant barriers, such as voltage fade and low rate capability, still need to be overcome before the practical applications of these materials. A detailed study of the voltage/capacity fading mechanism will be beneficial for further tailoring the electrode structure and thus improving the electrochemical performances of these layered cathodes. Here, we report detailed studies of structural changes of LMR layered cathode Li[Li0.2Ni0.2Mn0.6]O2 after long-term cycling by aberration-corrected scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS). The fundamental findings provide new insights into capacity/voltage fading mechanism of Li[Li0.2Ni0.2Mn0.6]O2. Sponge-like structure and fragmented pieces were found on the surface of cathode after extended cycling. Formation of Mn2+ species and reduced Li content in the fragments leads to the significant capacity loss during cycling. These results also imply the functional mechanism of surface coatings, e.g. AlF3, which can protect the electrode from etching by acidic species in the electrolyte, suppress cathode corrosion/fragmentation and thus improve long-term cycling stability. At last, the effect of the precursors and electrolyte additives on the cycling stability of LMR cathode materials will also be reported.
Acknowledgement
This work is supported by the Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U. S. Department of Energy, under the Batteries for Advanced Transportation Technologies program. The microscopic study described in this paper is part of the Chemical Imaging Initiative at Pacific Northwest National Laboratory (PNNL) conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE&’s Office of Biological and Environmental Research and located at PNNL.

Over-lithiated layered oxide (OLO) has attracted a lot of interests as a cathode material in high energy density lithium ion batteries due to its prominent energy density over 250 mAh g-1. However, the problem of kinetic hindrance, which is originated from their structural deformations, electrolyte decomposition and oxygen evolutions owing to participation of Li2MnO3 to de-lithiation process beyond 4.4 V vs. Li/Li+, restricts wide applications of OLO. Therefore, we have investigated surface coatings on OLO to improve the cycleability and rate capabilities of OLO. Several kinds of OLOs which are surface-modified with various functional materials such as electrochemically robust materials (AlO2 and AlF3), high electronic conductive materials (carbon nanotubes and carbon nano powders) and lithium ion conductive materials (Li2TiF6 , Li4SiO4 and Li7La3Zr2O12) have been synthesized and conducted a detailed study to develop high energy density lithium ion battery for electric vehicle and smart grid energy storage systems. Despite the great improvement in performances of the coated OLO, the failure mechanism of the OLO is still controversial. Several failure mechanisms, including poor electronic conductivity, surface structural deformation and poor ionic conductivities were studied by approaching with several kinds of surface modifications. Investigations of the surface failure of the OLO are the key factor to commercialize the OLO cathode materials. Furthermore, in this work we discuss various coating methods to cover the surface of cathode. Different samples are characterized by surface analyses (X-ray photoelectron spectroscopy, Raman spectrscopy, FT-IR and Scanning Transimission Electron Microscopy) and electrochemical methods (galvanostatic charge and discharge, AC impedance and GITT (galvanostatic intermittent titration technique)).

A new family of oxoanion battery materials which can reversibly cycle Li-ions has been found. This structure type can deliver high specific capacities (> 150 mAh/g) at discharge potentials starting above 4 V. This family of compounds has a number of desirable features including high ionic conductivities, small volume changes, and good thermal stability (to ~500 °C). Structural and electrochemical features of this class of compounds will be discussed in the context of ex situ and in situ diffraction and XAFS experiments and DFT calculations.

High power and high energy density are essential to batteries for applications in electric vehicles, military and stationary energy storage applications. Continuous improvements in lithium-ion battery (LIB) technology are needed to fulfill more stringent requirements such as longer cycle life, increased capacity, and greater stability at high operating temperatures. The capacity of current cathode materials used for LIBs is limited. Improvements in rate capability and capacity can insure a longer cycle life and enhance LIBs. Lithium manganese nickel oxide, LiMn1.5Ni0.5O4 (LMNO) is a promising candidate because of high voltage operation. However, dissolution of manganese due to reaction with electrolytes and lower cycle life/capacity is still a concern. Recently, several groups have reported an integrated layered-spinel composite cathodes using LMNO and Li2Mn0.6Ni0.2O3 to form LixMn1.5Ni0.5Oy (x=1.0~3.0). These composite cathodes have shown better performances than the layered or spinel cathodes with respect to specific capacity and cyclability. Our strategy is to investigate the effect of Li content in LMNO and investigate its structural characteristics and cycling performances. In addition, we will investigate the effect of surface modification of cathode materials using atomic layer deposition (ALD) and/or post-annealing. Li1.35Mn0.75Ni0.25Oy sample showed the best cycle stability during cycling between 2-5 V and a high capacity of over 200 mAh/g. Detailed studies that elucidate the effect of the spinel-to-layered phase ratio on the electrochemical performances and stability of lithium ion batteries will be presented.

Flexible batteries that can tolerate large mechanical stress are of considerable interest in portable electronics. However, most designs employ thin film batteries, which are not practical because of their low energy capacity and structural limitations of the sheet-like architecture. Here we report a cable-type structure for lithium-ion batteries with exceptional mechanical flexibility. The batteries comprise several anode strands coiled into a hollow-spiral core, which is surrounded by a heat-resistive separator wetted with liquid electrolyte and a tubular outer cathode, and finally enclosed in a heat-shrinkable packaging tube. The multi-helical anode structure is critical to the robustness under mechanical stress and facilitates electrolyte wetting of battery components. A prototype showed stable discharge characteristics regardless of bending strain and successfully powered an LED screen and MP3 player under severe twisting and bending. The proposed battery design will free product designers from conventional constraints and might facilitate breakthroughs in flexible and wearable electronics.

It has been well established that substitution enhances the electrochemical performance of LiFePO₄ as cathode material in Li-ion batteries, especially at high current densities. However, the reaction mechanism, two-phase vs. single-phase, enabling fast kinetics of LiFePO₄ is still a subject of debate. For example, under equilibrium conditions Li_xFePO₄ relaxes to form FePO₄ and LiFePO₄ phases upon delithiation. On the contrary, LiFe_0.6Mn_0.4PO₄ demonstrates a single-phase reaction for the Fe³⁺/Fe²⁺ redox couple, while the extraction of Li during Mn²⁺ to Mn³⁺ oxidation proceeds in a two-phase manner. The departure from the equilibrium two-phase to a single phase for the olivine structure upon substitution is still not well understood. Here we have investigated the structural changes accompanying the chemical and electrochemical lithiation and delithiation processes of Li_xMg_y(Fe_0.6Mn_0.4)_1-yPO₄ (0 le; y le;0.5, 0le; xle;1) using in-situ and ex-situ XRD and XAS, as well as magnetic susceptibility measurements, to probe both the kinetic and equilibrium conditions. XRD and XAS results show that under equilibrium conditions LixMg_0.5Fe_0.3Mn_0.2PO₄ exhibit a single-phase reaction mechanism pathway upon delithiation for the entire extractable Li range 0le; xle;0.5. Possible reasons favoring the single-phase in the presence of Mg, including smaller lattice mismatch, lattice strain, and structural defects will be discussed. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, and Office of Basic Energy Sciences under Award Number DE-SC0001294.

Finding new polyanionic Li-ion battery cathodes with higher capacities is one of the major targets of battery research. One obvious approach is to develop materials capable of exchanging more than one electron per transition metal. However, constraints on operating voltage due to organic electrolyte stability as well as cathode structural stability have made this goal difficult to achieve. For instance, chemistries such as Li2MP2O7 (M=Mn, Fe) have been difficult to use as multi-electron cathode due to the very high voltage of the 3+/4+ couple for Fe and Mn in phosphates.
In this talk, we will report on a voltage design strategy based on mixing different transition metals in targeted crystal structures. By mixing a metal active on the +2/+3 couple (e.g., Fe) with an element active on the +3/+5 or +3/+6 couple such as V or Mo, we show that multi-electron high capacity cathodes (active in a reasonable voltage window) can be designed.
We present different mixed compounds proposed by this strategy and show their computed capacity, voltage profile, and stability (in the discharged and charged state). We identify and discuss several promising novel high energy density, high safety cathode materials.

Phase transformation dynamics is believed to play a critical role during ultrafast charge/discharge of nano-LiFePO4 [1,2], and has recently attracted intensive investigations. However, in most of the studies, responses of a porous electrode are directly interpreted as the microscopic dynamics of a single composing particle without considering the influence of the statistical effects.
In the voltage-step experiments, the non-monotonic transient currents of the electrode are commonly interpreted as the nucleation and growth mechanism by the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory [3,4]. However, our model demonstrates that this characteristic is simply a result of the statistical effects caused by a simple Markov process among countless composing nanoparticles. We differentiate the roles of nucleation and surface reaction, which allows for decoupling the activation rate and the filling speed from the classic “effective” rate constant of the KJMA equation. And instead of the Avrami exponent, the averaged filling speed extracted from responses of porous electrodes is more appropriate for identifying the phase transformation dynamics in single composing particles by comparing with the material-specific dynamic regimes.
Because of the persistence of active (non-equilibrium) particles in a working electrode, our analysis under constant current situations suggests that the phase transformation delay observed by in situ powder diffraction is also a result of statistical effects, which until now has been attributed to surface amorphization [5] and solid solution [6] in single composing particles.
References
[1] Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. J. Electrochem. Soc. 1997, 144, 1188-1194.
[2] Kang, B.; Ceder, G. Nature 2009, 458, 190-193.
[3] Oyama, G.; Yamada, Y.; Natsui, R.; Nishimura, S.; Yamada, A. J. Phys. Chem. C 2012, 116, 7306-7311.
[4] Allen, J. L.; Jow, T. R.; Wolfenstine, J. Chem. Mater. 2007, 19, 2108-2111.
[5] Kao, Y. H.; Tang, M.; Meethong, N.; Bai, J. M.; Carter, W. C.; Chiang, Y. M. Chem. Mater. 2010, 22, 5845-5855.
[6] Sharma, N.; Guo, X.; Du, G.; Guo, Z.; Wang, J.; Wang, Z.; Peterson, V. K. J. Am. Chem. Soc. 2012, 134, 7867-7873.

A systematic investigation of the possibility of Fe based cathodes with 2 Li per 1 Fe atom electrochemical cycling was undertaken. In such cathodes, both the Fe²⁺/Fe³⁺ as well as the Fe³⁺/Fe⁴⁺ redox couples are to be utilized. Our study was focused on a model structure with Fe exclusively in tetrahedral, LiFeO₂ - tunnel, environments. The target compound was prepared via ion exchange from appropriate intermediate phases with larger alkali cations. Structural motif was preserved during the ion exchanges as confirmed by powder X-ray diffraction measurements.
Density functional theory GGA + U calculations show a high density of O-2p states near the Fermi energy in LiFeO₂ - tunnel. Therefore Li deintercalation can lead to (O₂)^2- peroxide unit formation and compound decomposition and/or reaction with the electrolyte. On the contrary, for a theoretical fully Li deintercalated “FeO₂-tunnel” compound, Fe-3d states dominate near the Fermi energy. Thus, Fe⁴⁺ can theoretically be formed in the compound if reaction with electrolyte can be avoided.
Chemical Li intercalation into the LiFeO₂-tunnel structure resulted in Li_1.57Fe_1.00O₂ stoichiometry without destroying the structure. Chemical Li deintercalation resulted in Li_0.42Fe_1.00O₂ stoichiometry. Mossbauer spectroscopy was utilized to determine the Fe oxidation state in the Li intercalated and deintercalated compounds. Presence of Fe²⁺ and Fe³⁺ in Li_1.57Fe_1.00O₂, as well as existence of Fe³⁺ and Fe⁴⁺ in Li_0.42Fe_1.00O₂ was confirmed by Mossbauer spectroscopy. Thus Fe²⁺/Fe³⁺ as well as Fe³⁺/Fe⁴⁺ redox couple might be accessible for electrochemical cycling in LiFeO₂-tunnel.
The theoretical specific capacity of LiFeO₂ for the case of 2 Li cycling is 526.6 mAh/g, much greater than conventional Li-ion cathode materials. Doped LiFe_1-xM_xO₂ (M = Co, Mn, and Ni) samples were prepared to improve electronic conductivity. Cyclic voltammetry measurements revealed multiple electrochemical processes during the charge/discharge cycle of these doped materials. Li intercalation occurs at ~2.2 V, as was determined electrochemically. The Fe^3+/4+ redox couple is utilized at 4.5 V. Reaction with the EC:DMC electrolyte begins at 4.6 V which prevent reversible cycling. Experiments with carbon coated LiFeO₂-tunnel in electrolytes stable at higher voltages are in the progress. The tunnel LiFeO₂ polymorph is the very first compound demonstrating accessibility of both redox couples, Fe²⁺/Fe³⁺ as well as Fe³⁺/Fe⁴⁺, in one compound for electrochemical cycling.

Layered vanadium oxides are considered promising candidates for use as cathode materials in intercalation-type batteries due to their open structures facilitating high energy storage capacities.[1] They have been shown to incorporate exceedingly high levels of lithium, i.e. more than one lithium per redox center. However, the deep lithiation causes changes of the crystal structure upon cycling, which results in poor long-term stability of such rechargeable devices. Vanadyl phosphate in the epsilon polymorph (ε-VOPO₄) is a material adopting stable 3D tunneling structure which consists of corner sharing VO₆ octahedra and PO₄ tetrahedra. Due to its reversible structure evolution upon electrochemical reaction, ε-VOPO₄ has been regarded as one of the most promising cathode materials, although the exact mechanism of the intercalation is currently not well understood at the highest limits.
In this work we present a combination of soft (hnu; = 1486.7 eV) and hard (hnu; = 4 KeV) x-ray photoelectron spectroscopy (XPS/HAXPES), in-situ x-ray absorption spectroscopy (XAS), and hybrid density functional theory (DFT) calculations to investigate the effect of lithium intercalation on the electronic structure. Using a similar methodology to that previously used to study LiMnPO₄, we directly compare our experimental results with first principles-calculations to investigate the underlying mechanism associated with lithium intercalation up to the highest lithium content.[2]
[1] N. A. Chernova, M. Roppolo, A. C. Dillon and M. S. Whittingham, J. Mater. Chem., 2009, 19, 2526
[2] L. F. J. Piper, N. F. Quackenbush, S. Sallis, D. O. Scanlon, G. W. Watson, K.-W. Nam, X.-Q. Yang, K. E. Smith, F. Omenya, N. A. Chernova, and M. S. Whittingham, J. Phys. Chem. C, 2013, 117, 10383

Introduction
One challenge for the integration of renewable energy sources with the electrical grid is the high frequency of extremely costly short-term transients due to factors such as cloud cover. Conventional battery technology cannot offer the long cycle life, high power, and high energy efficiency needed to mitigate the effects of these transients.
We have recently shown that open-framework materials with the Prussian Blue structure can be used as battery electrodes in a variety of aqueous alkali ion electrolytes. These electrode materials can operate at extremely high rates for tens of thousands of deep-discharge cycles. They are easily synthesized in bulk from earth-abundant precursors near room temperature, and operate in safe, inexpensive aque-ous electrolytes. Such Prussian Blue analogue mate-rials are attractive for use in large-scale stationary batteries integrated with the energy grid.
Experiments and Results
Recent observations of the physical properties and electrochemical performance of a number of electrodes containing Prussian Blue analogues which operate by insertion reactions in a variety of aque-ous electrolytes will be reported.
These Prussian Blue cathodes are most advanta-geously paired with anodes that have comparable cycle life and kinetics. One alternative is to use the activated charcoal that is employed in commercial ultracapacitors, and we have recently demonstrated the attractive prop-erties of this combination. However, the low capacity of such carbon materials, as well as the inherent variation of the potential with the state of charge of such capaci-tive electrodes, severely limits the specific energy of such cells.
We are now able to construct cells in which materi-als with the Prussian Blue crystal structure are active in both electrodes. The result is a new type of safe, fast, inexpensive, long-cycle life aqueous electrolyte battery, in which the output voltage does not vary appreciably with the state of charge.
These high rate cells have demonstrated a 96.7% round trip energy efficiency when cycled at a 5C rate, and a 84.2% energy efficiency at 50C. In addition, they have shown zero capacity loss after 1000 deep-discharge cycles.
References
[1] C.D. Wessells, R.A. Huggins, and Y. Cui, Nature Communications 2 (2011) 550
[2] C.D. Wessells, S.V. Peddada, R.A. Huggins,
and Y. Cui, Nano Letters 11 (2011) 5421
[3] C.D. Wessells, S.V. Peddada, M.T. McDowell, R.A. Huggins, and Y. Cui, J. Electrochem. Soc. 159 (2012) A98
[4] C.D. Wessells, M.T. McDowell, S.V. Peddada, M. Pasta, R.A. Huggins, and Y. Cui, ACS Nano 6 (2012) 1688
[5] M. Pasta, C.D. Wessells, R.A. Huggins and Y. Cui, Nature Communications 3 ( 2012) 2139

Energy storage has been considered as an important part in the power system operation. At present, most energy storage technologies are in the research or demonstration stage, except pump-hydro technology which has been widely deployed. Battery energy storage (BES) has developed rapidly in recent years and becomes one of main prospective technologies for power system application. Sodium-sulfur batteries, redox flow batteries, lithium ion batteries, and advanced lead-acid batteries have been considered as battery types with application potential.
State Grid Corporation of China (SGCC) has carried out several demonstration projects focused on BES in the recent years. For example, the demonstration project in Zhangbei County is a combination of wind power, PV, energy storage and smart transmission. The first phase project contains 14MW/63MWh lithium-ion batteries and 2MW/8MWh all vanadium redox flow batteries (VRB). The large-scale BES is controlled to improve the output characteristics of renewable energy generation. Tests were carried out separately to verify the performance of the BES under the four modes below:
1) smoothing the fluctuations of the renewable energy generation
2) peak-valley balance (reducing power curtailment)
3) tracking the scheduled output curve
4) frequency regulation
The test results showed that the BES operated under certain charge and discharge conditions depending on the mode it worked at. According to the recorded data, the average state of charge (SOC) was around 47%~56% under the fluctuation smoothing mode. And the charge-discharge cycles reached 120-150 times per day. Under the schedule tracking mode, it was found out that the charge and discharge current rates of batteries was not high. And the charge-discharge cycles reached 10 times per day, among which the conditions that the depth of discharge (DOD) exceeded 10% appeared 2-3 times. Under the peak-valley balance mode, the current rate was still not high, and the charge and discharge cycles were usually 1 time per day. And the SOC was most around 20%~80%.
The indices to evaluate a type of BES technology can be summarized as the following 4 categories: the system scale, the technical performance, the economy and the industrialization. The capacity of energy storage system for grid application may need to achieve MW and MWh level with high safety. The cycle life is expected to exceed 5000 times, and the efficiency is expected to be above 80%. The related devices can realize standardized mass production for manufactures. And the total system must be easy to install and maintenance for users. The income getting from grid services must balance the costs in which devices depreciation, energy losses during conversion, operation costs, and other expenses should be considered.

Owing to high hydrogen storage capacity and good electrochemical properties, La-Mg-Ni system hydrogen storage alloys have been considered as one of the most promising candidates for metal hydride electrode materials. However, rather poor cyclic stability resists their practical application. In order to improve the hydrogen storage properties, considerable investigations have been carried out. Annealing treatment is reported to be an effective method in improving the performances of the hydrogen storage alloys. The research presented here examined the influence of annealing treatment on the hydrogen storage properties of La1.8Ti0.2MgNi9 alloys.
La1.8Ti0.2MgNi9 alloy was prepared by magnetic levitation melting under Ar atmosphere, and as-cast La1.8Ti0.2MgNi9 alloy was annealed at 1073K, 1173K for 10h under vacuum. All alloys were mechanically crushed and ground into the powders of 200 mesh size for X-ray diffraction (XRD), pressure-composition isotherms (P-C-T) and electrochemical measurements analysis.
All alloys hold a multiphase structure, composing of LaNi5, LaNi3 and LaMg2Ni9 phase, and LaNi5 phase with hexagonal CaCu5-type structure is main phase, Ti2Ni phase appears at 1173K. Most of diffraction peaks become sharper and the peak intensity increases with the increase of annealing temperature. The cell volumes of LaNi5 and LaNi3 phase remain almost unchanged, but that of LaMg2Ni9 phase becomes smaller with annealing temperature.
Annealed alloys show higher hydrogen storage capacities and lower hydrogen absorption/desorption plateau pressures compared to as-cast alloy. The hydrogen storage capacity and discharge capacity increases from 1.363 wt.% and 333mAh/g (as-cast) to 1.455wt.% and 366mAh/g (annealed at 1173K), respectively, and the cyclic stability is improved markedly. In addition, annealed alloy electrodes have better high rate discharge ability.

The understanding of how the formation of peroxide/superoxide species and the electrolyte decomposition at the air cathode influence the discharge-charge characteristics is important for the design of advanced catalyst materials for rechargeable high-performance lithium-air batteries. In this presentation, selected noble metal (e.g., Pt, Pd, and Au) containing nanoparticles with different transition metals are investigated as catalysts in a rechargeable lithium-oxygen battery. The investigation focused on two related aspects of this type of electrocatalysts. One involves the nanoscale alloying or the phase segregation effect of the nanoalloys on the discharge-charge characteristics, which provides information for assessing the synergy of the metal components in the oxygen reduction reaction and oxygen evolution reaction. The other aspect involves the electrode and charge transfer characteristics based on electrochemical impedance measurement of the lithium-oxygen cell, which provide information for assessing how the formation of peroxide/superoxide species and the electrolyte decomposition at the air cathode influence the discharge-charge processes. The fundamental understanding shed light on the factors responsible for the performance decay, and has implications to the design of advanced nanoalloys for air cathode catalysts in rechargeable lithium-air batteries.

Nanomaterials have led to significant improvements in the rate capability of lithium ion cells. Yet many nanomaterial-based technologies do not solve other critical requirements of high energy density batteries such as high volumetric energy density, solid electrolyte interface (SEI) stability, and low cost and scalable synthesis. To address these limitations, we have developed a new multi-layered electrode architecture for high-power Li-ion batteries. The electrode architecture consists of alternating layers of carbon nanotubes and lithium ion active materials stacked on a current collector. The intermittent layers of carbon nanotubes form a highly conductive and porous matrix. This facilitates electron transport and lithium ion diffusion throughout the electrode, and enhances bulk conductivity of the electrode. The architecture employs commercially available micron-sized spinel lithium manganese oxide (LiMn₂O₄) and commercially available multi-walled carbon nanotubes (MWNT). Using this multi-layer structure, we demonstrate a significant increase in power density of a lithium ion cathode with high active material loading in the range of 8-10mg/cm² and low carbon contents of 10% and 20%. At a discharge rate of 10C, a multi-layered electrode containing a high active material loading of 9 mg/cm² demonstrates greater than 65% capacity retention and highly stable cycling for over 100 cycles. The conventionally prepared electrode exhibits less than 10% capacity retention at a loading of 2 mg/cm². These values translate to an enhancement in power density by 20 times over a conventionally prepared cathode of identical composition.
Furthermore, the use of nanomaterials does not have a detrimental impact on the packing density of the electrode. We demonstrate improvement in volumetric density by a factor of 3 over a conventionally prepared electrode. Utilizing a well-characterized fabrication method, we demonstrate the high-rate fabrication of the multi-layer structure using a room temperature and atmospheric pressure process. We also demonstrate the versatility of the multi-layer structure when used in conjunction with a low-rate lithium ion cathode material, such as the high capacity lithium-rich lithium nickel manganese cobalt oxide, 0.3Li₂MnO₃ 0.7LiMn_0.333Ni_0.333Co_0.333O₂. When the architecture is applied to the 0.3Li₂MnO₃ 0.7LiMn_0.333Ni_0.333Co_0.333O₂ electrode, we observe a cycle life of greater than 500 full-depth cycles at a discharge rate of 1C. We have identified improved porosity and conductivity of the intermittent carbon nanotube layer as the mechanism of performance enhancement from data obtained from galvanostatic cycling, electrochemical impedance spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), and 4-point probe DC conductivity measurements.

There is growing interest in thin, lightweight, and flexible energy storage devices to meet the special needs for next-generation, high-performance, flexible electronics. Electrospinning has been recognized as a simple and efficient technique for the fabrication of ultrathin fibers from a variety of materials including polymers, composite and ceramics.
Here we report a thin,lightweight, and flexible lithium ion battery made from electrospun nanowires. Either/Both the electrode materials or/and the separator materials are fabricated by electrospinning technique. The thress dimentional and interconnected network will provide excellent flexibility, conductivity and mechanical strength of the final battery devices.
In this research, highly flexible and large area LIBs can be realized. The porous structure can be controlled and realized by electrospinning technique, and the ionic conductivity of the electode/separators can be well optimized.
3D interconnected nanowire structures will provide better stability under the bending force, and the stability as well as the cycle ability will be improved. This fabrication method is easy to be scale-up and we can get the rechargeable LIBs with low weight, high surface area, and a high energy density of 110Wh/kg of the whole device.

Non-linear Optical (KTiOPO4) and Li Battery materials have been studied with Raman Spectroscopy on-line with Piezo Force and Contact Resonance Microscopies. This is allowed by a unique design of the scanned probe microscopy platform used in these studies and the electrical probes that have been developed that keep the optical axis completely free from above so that such combinations are feasible. The integration allows the investigation of alterations in the strain induced in the chemical structure of the materials as a result of the induction of piezo force. The combination of chemical characterization with both piezo force and contact resonance [1] microscopy allows for the monitoring of structural and ionic changes using Raman scattering correlated with these modalities. In KTP it has been seen that the largest changes are seen in TiO6 octahedral structure symmetric and antisymmetric stretch in the interfaces between the regions of the poling of the structure. In the Li battery material defined chemical changes are seen that are related to the contact resonance frequency. The combination adds considerable insight into both the techniques of Piezo Force Microscopy and Contact Resonance Microscopy.
1 Balke et al, Nature Nanotechnology DOI: 10.1038/NNANO.2010.174 92010)

TiO2 nanoparticles synthesized by a facile sol-gel method were encapsulated in graphene nanosheets(GNS) to enhance its performance as anode active materials in Li-ion batteries. The encapsulation was facilitated by electrostatic interaction between positively charged surface of TiO2 with silane decoration and the negatively charged graphene oxide. Followed by reduction of the graphene oxide wrapped TiO2 composite, graphene encapsulated TiO2 composite was successfully fabricated. SEM and TEM revealed the uniform and individual wrapping of TiO2 by graphene. XRD results further validated uniform distribution of graphene within anatase TiO2. FTIR and Zeta potential results confirmed that the electrostatic interaction was effective in facilitate uniform wrapping of graphene oxide around TiO2 nanoparticles. Electrochemical performance of the nano-composite was tested by cyclic voltammetry and coin cell tests. The graphene encapsulated TiO2 materials demonstrated a very high initial capacity of 409mAh/g at 1C and retained a capacity of 142 mAh/g at 20C. The nanocomposite electrode also showed a Coulombic efficiency as high as 98%~100% and good long term cycling performance(as high as 353.6mAh/g after 100 cycles) at a rate of 1C. Possible mechanisms of improved performance are also discussed in this presentation.

ABSTRACT BODY:
Alkaline batteries are one of the most common modern forms of primary battery. These cells depend on a reaction between zinc (Zn) and manganese dioxide (MnO2) to generate energy. This reaction gives alkaline batteries a relatively high energy density and a low cost per kilowatt-hour, but phase transformations occurring during deep discharge prevent recharge. In a typical alkaline battery, useful rechargeability with minimal capacity losses can only be achieved if no more than 10% of the cells capacity is used. We have developed a novel electrode material which consists of an aragonite-type crystal structure with extensive substitution of manganese atoms. This material has superior rate capability and cyclability compared to gamma MnO2, with comparable cost and specific capacity, and has never before been described in the literature. In this presentation, we describe the crystal structure and novel charge storage mechanism of this material, as well as the structural changes occuring during its use as an electrode material.
Our material is produced by a simple one-step hydrothermal process, which transforms the surface of a carbon precursor material into an aragonite-type carbonate. Permanganate salts in the synthesis process result in extensive substitution of manganese atoms into the crystal structure without significantly changes in long-range order. We have studied this material via in-situ and ex-situ X-ray diffraction and electron microscopy techniques. The results will be further discussed in the presentation.

The Li₄Ti₅O₁₂ (LTO) spinel is one of the most promising anode materials for lithium ion batteries (LIBs) because of its merits of negligible volume changes (~1%) and stable operating voltage during charging/discharging. Although the volume changes of LTO are more than ten times less than conventional graphite materials (10%) and much less than various Si (400%) and alloy materials, the insulating property of LTO results in poor rate capability, which limits its range of applications. In the study, various transition metals (M = Sc, Y, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Ru, Co, Ni, Cu, Zn) are investigated in order to improve the electrical conductivity of LTO. With the aid of the ab initio calculations, the general trend of the doping effects of the transition metals upon the important physical properties, including structural parameters, phase stabilities, average intercalation voltages, and electrical properties, is revealed. Since the 16d sites of the full supercell of (Li₂₄)_8a[Li₈Ti₄₀]_16d(O₉₆)_32e for LTO are randomly occupied by 8 Li and 40 Ti ions, the total number of arrangements for the pristine LTO can be as many as 48!/8!40!, i.e. 377,348,994 arrangements. It is not a realistic practice to perform such numerous calculations. We made a systematical analysis to dramatically reduce all arrangements to 6 distinguishable ones and constructed the full supercell of Li₃₂Ti₄₀O₉₆ based on the most energetically favorable arrangement of Ti and Li ions at the 16d sites. With the full supercell model of LTO, the preferred Li- or Ti-substituted LTO with various dopants M, i.e. Li₃₁M₁Ti₄₀O₉₆ (Li_3.875M_0.125Ti₅O₁₂) or Li₃₂M₁Ti₃₉O₉₆ (Li₄M_0.125Ti_4.875O₁₂), were identified based on the local environments between the dopant M and the neighboring Li and Ti ions at the 16d sites. The Li-substituted LTO showed large band gap reduction and provided free electrons and hence had greater improvement in electrical conductivity than the Ti-substituted ones. Finally, the desired transition metal dopants were suggested for the doped LTO as anode materials in LIBs.

Silicon is a very promising anode material for lithium ion batteries. It has a 4200mAh/g theoretical capacity, which is ten times higher than that of commercial graphite anodes. However, when the lithium ions diffuse to Si anode, the volume of Si will expands to almost 400% its initial size and results the crack of Si. Such a huge volume changes and crack cause significant capacity loss. Meanwhile, with the crack of Si particles, the contact resistance between the electrode and current collector increases. Moreover, the solid electrolyte interphase (SEI), which is generated during the cycling, reduces the discharge capacity. These issues must be addressed for widespread application of this material. In this work, Si particles are etched to form a porous structure. The pores in Si provide space for the volume expansion and liquid electrolyte diffusion. A layer of amorphous carbon is formed inside the pores, which gives an excellent isolation between the Si particle and electrolyte, so that the formation of SEI layer is stabilized. Meanwhile, this novel structure enhances the mechanical properties of the Si particles and the crack phenomenon caused by the volume change is significantly restrained. The contact between the Cu foil current collector and electrode is improved by a layer of conductive Au-Pd. The Au-Pd coating layer serves as conductivity channels to allow an effective electron transfer between the electrode and current collector. Therefore, an excellent cycle life under a high rate with the novel Si electrode is achieved.

Nanosized Sn-Fe alloy, which meets the demand for a safe, cost-effective, environmentally benign and high-capacity anode material, has attracted considerable research interest for its potential to replace presently dominating graphite anodes in lithium-ion batteries. Among all the Sn-Fe alloy compounds, Sn₂Fe has been regarded as the most promising candidate due to its high theoretical capacity of 804 mAh/g. Our research has thus been focused on Sn₂Fe-based anode materials prepared via two different methods: high energy ball milling and hydrothermal synthesis. The high energy ball milling enables the reduction of SnO to Sn and then the reaction with iron to form nanosized Sn₂Fe. Our results show that when the ball-milling reaction is incomplete, a mixture of Sn/Sn₂Fe/graphite can be obtained, which gives better capacity than the complete reaction producing Sn₂Fe/graphite. Hydrothermally prepared Sn₂Fe was obtained by reducing SnCl₂ and FeCl₃ with NaBH₄. The ratio of SnCl₂ and FeCl₃ determines the formation of pure Sn₂Fe or Sn/Sn₂Fe mixture. The reaction mechanism of Sn₂Fe materials synthesized by these two methods have been investigated using in-situ and ex-situ powder X-ray diffraction, X-ray absorption spectroscopy (XAS), pair distribution function (PDF) analysis, scanning electron microscope (SEM) and other techniques. The optimized synthetic procedure and crucial factors that affect the electrochemical performance (such as reaction time, carbon content, additives, etc.) will be reported. This research is supported by DOE-EERE-BATT, DE-AC02-05CH11231 under Award Number 6807148, and by NYSERDA.

Vanadium oxide electrodes can undergo a number of phase transformations during Li insertion and removal. Previous research has characterized the electrochemical response and phase transformations that occur when these materials are used as cathodes in Li ion batteries. However, there is still a lack of a clear understanding of the factors which affect these phase changes. This prior work provides important background knowledge for focused investigations on the impact of internal stresses and electrode surfaces on the relevant transformations. In addition to these stress effects, the impact of oxygen non-stoichiometry variations were also explored. These studies were conducted using materials formed under a variety of different conditions. The initial stress state in thin films was varied over a broad range by altering the processing conditions (while maintaining similar grain structures). These investigations focused on the use of in situ stress measurements, along with x-ray diffraction and detailed electron microscopy studies. Results with these materials were also compared with the behavior of mesoporous xerogel electrodes where stress evolution is substantially reduced.

Small molecules have recently received increasing attention as electrode materials for flow batteries in the battery community. In this talk, we will discuss a fast and robust theoretical method for finding small organic molecules for flow batteries. In particular, we will demonstrate the values of the high-throughput computational approaches. Here, our goals are two-fold: to systematically discover the effective electrodes of a flow battery from predicted redox behaviors and to guide the next experiments by identifying theory-driven structure-property relationships that serve as design rules of interesting molecules.
We will discuss our virtual organic chemical library of small molecules using the possible building blocks and bonding rules. With the huge search space for unknown molecules and theoretical calculations, we are able to track the multiple associations between redox behaviors and structures of molecules for the discovery of small molecules. We will address how to exploit the relationships of the new materials to effectively synthesize property-tunable molecules for flow batteries.

ABSTRACT BODY: The performance of current energy conversion and storage technologies remains a key challenge for the efficient use of electrical energy mainly in transportation and other commercial applications. Lithium ion batteries (LIB) have been widely employed in portable electronic devices. LIB exhibits higher energy density and longer cycle life than other battery technologies, such as lead-acid and nickel metal hydride. Hence, various researches have focused on exploring the potential of LIB for near-term solution for environmental friendly transportation and energy storage for sustainable power sources, such as solar, wind, water, etc.
Vanadium-based materials are one of the most promising candidates as alternative cathodes with high capacities due to their ability to exhibit mixed valences with redox potential values for LIB applications. Among the vanadium-based materials, vanadium oxide, V2O5 [1] and vanadate LiV3O8 [2] are most extensively studied and reported. However, the electrochemical performances of these materials are still unsatisfactory due to irreversible structural transformation and intrinsic limitation causing capacity fading. Lithium-rich rocksalt vanadate Li2-xVO3 has been demonstrated as a potential cathode material for LIB [3]. It is capable to exhibit a high specific capacity of 253 mAh g-1 with stable cycling behavior. It can be easily obtained by either chemical or electrochemical insertion of lithium from LiVO3. It is generally reported that the electrochemical performance of vanadates are strongly connected with the preparation conditions and morphological characteristics of final products [4]. Hence, we explore nanoscale synthesis and electrochemical properties of Li2-xVO3 to elucidate its lithium insertion characteristics and to increase the practical achievable capacity.
In this study, few synthesis methods were employed to synthesize Li2-xVO3, including solid state reaction, sol gel and electrospinning. The prepared samples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical analysis. By tuning the experimental conditions, smaller particle size was achieved. We had observed that the electrochemical performance is highly dependent on the differences in particle size and morphology. Detailed results based on the different discharge capacity and rate capability will be presented.
1. Mai, L., et al., Journal of Materials Research, 2011. 26(17): p. 2175-2185.
2. Sakunthala, A., et al., Journal of Physical Chemistry C, 2010. 114(17): p. 8099-8107.
3. Pralong, V., et al., Chemistry of Materials, 2012. 24(1): p. 12-14.
4. Kim, K., et al., Electrochimica Acta, 2013. 89: p. 708-716.

To increase the energy density of next-generation lithium-ion batteries, currently dominating anode material, graphitic carbon, has to be replaced because of its limited gravimetric and volumetric capacities. Silicon has drawn a great deal of attention because it would afford a much higher capacity than graphite (~4200 mAh/g vs. 372 mAh/g). However, the huge volume expansion/contraction occurring during the electrochemical reaction deteriorates the cycling performance. For the sake of alleviating this volume change impact and investigating the key factors that determine the electrochemical performance, we carried out a comparative study of our synthesized nanoporous Si (via etching a low-cost Al-Si alloy) and several other Si anode materials with different morphology, composition and particle size. Characterization techniques such as X-ray diffraction, Scanning Electronic Microscopy, ICP, and NMR have been utilized along with electrochemical testing to understand correlations between the electrochemical performance and materials characteristics. Our results show that the rational control of morphology and composition plays a very important role in enhancing the electrochemical performance of Si as anode in lithium-ion batteries. This research is based upon work supported DOE-EERE, as part of BATT, DE-AC02-05CH11231 under Award Number 6807148.

Lithium-ion secondary batteries are an energy storage technology suitable for portable applications and for electric grid systems. They outperform, by at least a factor of 2.5, other technologies such as nickel-metal hybrid and nickel-cadmium batteries in terms of delivered energy. Lithium batteries with silicon-based anodes have been considered because of the high theoretical specific charge capacity of silicon. However, the capacity loss caused by the mechanical failure and chemical degradation of the silicon structure during battery operation remains a limiting factor to the mass commercialization of silicon-based lithium-ion batteries.
We have used theoretical modeling and density functional theory calculations to study the structural properties and dynamics of bulk crystalline and amorphous silicon for lithium-ion electrodes [1]. We investigate the interaction between lithium and silicon at the atomic level by identifying binding sites for lithium and we calculate the energy barriers for lithium diffusion in the material.
[1] G. A. Tritsaris, K. Zhao, O. U. Okeke, E. Kaxiras. Diffusion of Lithium in Bulk Amorphous Silicon: A Theoretical Study. Journal of Physical Chemistry C 2012, 116 (42), 22212-22216

Anode material, silicon have been explored by many scientist. This material has large advantages play a role in anode site in lithium ion battery. For example, high theoretical capacity, low cost and so on. But there exist some limitation which large volume expansion, low kinetic of ion and electron and unstable SEI layer at surface. These problems play in sticking point to commercialize silicon in lithium ion battery.
Recently, many research group report various morphology to hammering with critical problem that volume expansion during in cycling. Yolk-shell, nanoparticle, hollow nanoparticle, nanowire, hollow nanowire and so on. Among them metal assisted catalytic etching adapted on bulk size silicon reported by our group is very effective for volume expansion. But continuous unstable SEI (Solid electrolyte interface) layer, low conductivity is still remaining problem in silicon anode site.
So, we demonstrate that a simple and effective strategy for high-performance Si electrodes exhibiting stable cycling even at elevated temperatures by combining carbon-coated bicontinuous Si nanostructures with a self-healing reducible solvent. The nanostructured Si particles are synthesized by silver-assisted wet chemical etching process of commercially available bulk Si particles in a hundred-gram scale. To properly design an electrolyte for the nanostructured Si anode with a high stability, we focus on fluoroethylene carbonate (FEC) to reduce damage to the Si anode by the electrolyte decomposition. The electrolyte with FEC as a co-solvent has the potential to continuously build a stable solid electrolyte interphase on the Si anode upon cycling, which has not been observed in electrolytes with small amount of a reducible additive. Furthermore, it was found that the electrochemical performance of porous Si anode at 30 oC and 60 oC is significantly improved when carbon coating layers are formulated with a FEC-based electrolyte.

Germanium nanowires (Ge NWs) are one of the potential anode materials for high rate lithium ion battery due to its high lithium diffusivity and specific capacity (theoretically, 1600 mAhg^-1). However, like other anode materials functioning through alloying with lithium, Ge-based anode materials suffer from poor cycle life due to large volume expansion and pulverization of the electrode accompanied during cycles. An ideal approach to overcome such problems is to coat Ge NWs with graphene that has superior mechanical properties and high electrical conductivity. In this presentation we will discuss about the direct growth of single to few layer graphene on Ge nanowire (Ge NW) by chemical vapor deposition (CVD) method without using metal catalysts and its application as an anode electrode of high rate lithium ion battery. Transmission electron spectroscopy (TEM) and Raman spectroscopy reveal that the graphene grown on the surface of Ge NW (Gr/Ge NW) shows high crystallinity comparable to the graphene grown by conventional CVD method (for example, CVD on Ni or Cu). When the Gr/Ge NW anode exhibits high specific capacity of 1059 mAhg^-1 and high capacity retention of 90 % at 4.0 C during 200 cycles. This high performance is attributed to unique structure of Gr/Ge NW. Tight encapsulation of each Ge NW with graphene alleviates volume expansion of Ge NW during cycles effectively, and also maintains high electrical conductivity during long cycles as confirmed by TEM images of Gr/Ge NW after 200 cycles showing robustness of Gr/Ge NWs. The growth mechanism of graphene on Ge NW and electrochemical performance of Gr/Ge NW will be discussed in detail.

Silicon is promising anode material for lithium ion batteries, due to their high theoretical specific capacity which is about ten times higher than conventinally using carbon materials. However, during lithiation and delithiation processes, silicon shows volume expansion up to 400%, which induces high mechanical stress. This mechanical stress creates cracks and pulverization of silicon. Consequently, silicon anode shows capacity fading even under low C-rate.
To overcome the mentioned problems, nanostructured silicon materials including nanowires and nanotubes are proposed because the strain can be relaxed easily by their small size and the void space. In addition, electrical connetion at the interface between the silicon and current collector is another significant factor to improve cycle life and rate capabiltiy.
To meet two requirements as above mentioned, in this study, a binder free a-Si anode was formed on nano-structured Cu current collector. The nano-structured Cu current collector was fabricated by hot-embossing and electroplating process. Then, a-Si was directly deposited on Cu current collector by low pressure chemical vapor deposition(LPCVD).
This a-Si anode showed high rate capability and cycling retention property during 500 cycles at 0.5 to 20 C rate. Identical charge and discharge rates were applied. The submicron void space of the nano-structured current collector prevent the cracks which can be caused by volume expansion of silicon during lithiation. In addition, due to excellent electrical connection between silicon and the Cu current collector, the a-Si anode retain about 90% of initial capacity after 70 cycles of gradually increasing C rate. The identical charge and discharge rates were also applied.

Silicon is regarded as one of the most promising anode materials for next generation lithium-ion batteries due to the highest theoretical capacity of 4200 mAh/g. However, poor capacity retention induced by pulverization of silicon and high irreversible capacity resulting from unstable solid electrolyte interface (SEI) formation during cycling hinder its practical applications. In this report, a carbon/silicon/alumina (C/Si/Al2O3) hollow spherical structure was fabricated to overcome the above issues. Carbon nanospheres (CNSs) thin film was fabricated by the template-directed carbon segregation method and deposited onto stainless steel by the electrophoretic deposition technique. Amorphous silicon was then deposited on the surface of CNSs through plasma enhanced chemical vapor deposition (PECVD). A thin layer of alumina was deposited by atomic layer deposition (ALD) at last. The C/Si/Al2O3 hollow structure not only accommodates large silicon volume expansion due to the existence of void space provided by CNSs, but also enables high rate capability resulting from the thin silicon layer. In addition, the outer shell of alumina maintains the integrity of silicon thus stable SEI is expected to be formed. The electrode exhibits excellent initial discharge capacity of 2262 mAh/g (based on the weight of the entire electrode) and 1870 mAh/g after 100 cycles at current density of 1 A/g. It displays the capacity retention of 83% over 100 cycles and an average fading rate of 0.18 % per cycle.

Graphene-based materials have attracted great interest for energy
storage. Due to the strong van der Waals attraction, graphene tend to aggregate, which
reduces their processability and compromises properties. This makes it
challenging to scale up the production and processing of graphene while
maintaining their outstanding properties. To address this problem, I
converted the sheets into paper-ball like structure using capillary compression in
evaporating aerosol droplets. The crumpled graphene are stabilized by
locally folded π-π stacked ridges, and do not unfold or collapse during common
processing. This form of graphene leads to scalable performance in energy
storage as the crumpled balls can resist aggregation and retain high
capacitance at high loading level. The crumpled graphene balls can be also
used as expandable shells for wrapping battery materials such as Si
nanoparticles, which can accommodate their expansion/contraction without facture, thus
suppresses the solid electrolyte interphase deposition and greatly improves
the coulombic efficiency.

Intercalation compounds are effective reversible Li+ storage hosts for the lithium-ion batteries because the insertion and extraction of Li+ do not involve structural reorganization of the host material; and hence high cycle stability can be a more assured outcome. Among the myriad of Li+ hosts for LIB applications, layered nanosheets such as graphene and transition metal dichalcogenides (TMDs) can leverage on the benefits of two-dimensionality to support very fast insertion and removal of Li+.1-3 Graphene is a close relative of the common graphite anode in LIBs and nitrogenation of graphene could further improve its electron transport property. Unlike the unary compound graphene, TMDs are layered binary compounds consisting of three stacked atomic layers, in which the insertion and extraction process of Li+ is relatively facile. Their geometric similarity to the graphene structure is conducive to the formation of stable composites with graphene. TMDs could then benefit from the excellent electrical conductivity of graphene to improve its Li+ storage properties.
WS2, which has a higher intrinsic electrical conductivity than MoS2 (the most studied TMD for reversible Li+ storage), was used to compound with graphene in this study. The integration of WS2 and NG into a composite was accomplished via a facile one-pot surfactant-assisted method which reduced the TMD precursor, nitrogenated the reduced graphene oxide (RGO), and assimilated the TMD with the nitrogenated RGO under hydrothermal conditions. The reduction of the WS2 precursor into single-layer or few-layer graphene-like nanosheets occurred in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). The effects of CTAB on the TMD nanostructure (layer number) and the electrochemical performance of the nanocomposites in reversible Li+ storage were investigated. The composite formed with a surfactant: tungsten precursor ratio of 1:1 delivered the best cyclability and rate performance, and may find uses in power-oriented applications.

We study synthesis of free-standing polymer derived SiCN/ MoS2 composite paper anode for Li-ion battery application. This was achieved following a two-step approach: First, polysilazane was interfaced with exfoliated MoS2 nanosheets which upon pyrolysis resulted in SiCN/MoSnot;2 composite. Second, dispersion of SiCN/MoS2 in isopropanol was vacuum filtered resulting in formation of a self-standing composite paper. Physical and chemical characterization of the composite was carried out by use of electron microscopy, Fourier transform infrared spectroscopy (FT-IR) and Thermo-gravimetric analysis (TGA). FT-IR data indicated complete conversion of polysilazane precursor to SiCN ceramic, while electron microscopy confirmed layered structure of the paper. Thermo-gravimetric analysis showed enhanced thermodynamic stability of the composite paper up to 800°C. Electrochemical analysis of SiCN/MoS2 composite paper anodes showed that Li-ion can reversible intercalate in the voltage range of 0-2.5 V with a first cycle discharge capacity of 770 mAh/g at a current density of 100 mA/g.

Transition metal phosphates (TMPs) are some of the most promising cathode materials for lithium-ion storage devices. Unlike the commercially established transition metal oxides, TMPs have the safety, low cost and high stability necessary for large scale application. Monoclinic α-Li3V2(PO4)3 has a complex metal phosphate framework that provides good transport for all three lithium ions, resulting in the highest gravimetric capacity of all the TMPs (197 mAh/g). The lithium-deinsertion process consists of a series of two-phase transitions driven by metal charge ordering and lithium site ordering. Upon reinsertion solid solution behavior is seen. During the second reinsertion process, the two-phase transitions are found to be reversible even at fast rates. However, after multiple charge-discharge cycles the two-phase transitions are no longer present in the voltage-composition curves associated with a gradual fade in capacity.
Several factors have been taken into consideration for the capacity loss of Li3V2(PO4)3 . The highly oxidative electrochemical window applied for Li3V2(PO4)3 (3.0-4.8 V) has led to investigation of a solid electrolyte interphase (SEI) and its effect on the insertion/deinsertion properties of the cathode. Elemental analysis has proven that partial vanadium dissolution occurs after the first charge (lithium deinsertion) showing the instability of the material in LiPF6 based electrolytes.1 Moreover, it has been hypothesized that the smooth voltage profile obtained after multi-cycling occurs from lithium ion disorder. Here we report investigations on the structural/electrochemical stability of Li3V2(PO4)3 using Raman microscopy as it provides a unique analytical tool for probing structural changes at the level of chemical bonds regardless of the phase of the material (crystalline or amorphous). Firstly, a fundamental and comprehensive Raman study of Li3V2(PO4)3 is discussed. The experimental and calculated Raman spectra are compared and symmetry assignments are provided for the modes from density functional theory as implemented in the Vienna ab initio simulation package (VASP).2 Additionally, the phase stability of microcrystalline α-Li3V2(PO4)3 was studied as a function of irradiation power density to ensure that the spectrum corresponded to the low temperature α phase ( as opposed to the high temperature β and γ phases). Ex situ Raman spectra of the cycled electrodes show evidence of different states of charge as well as amorphization of the material. In situ investigations will further elucidate on the insertion/deinsertion mechanism and its reversibility beyond the first cycle.
(1) Wu, J.; Membreno, N.; Yu, W.-Y.; Wiggins-Camacho, J. D.; Flaherty, D. W.; Mullins, C. B.; Stevenson, K. J. J. Phys. Chem. C 2012, 116, 21208-21215.
(2) Membreno, N.; Xiao, P.; Park, K.-S.; Goodenough, J. B.; Henkelman, G.; Stevenson, K. J. J. Phys. Chem. C 2013 DOI: 10.1021/jp403282a.

Last year 37% of the battery market was made up of lithium ion batteries with total sales valued at $11.8 billion dollars. Currently in the US almost all spent lithium ion batteries are land filled, compared to other types of batteries, such as lead acid batteries, in which 97% are recycled. This presents a large amount of environmental waste. Based on current trends in Li-ion battery use, if Li-ion batteries are not recycled, global lithium reserves are expected to be depleted by 2050. Additionally, recycling Li-ion batteries presents an economic opportunity in through the recovery of key valuable metals, such as cobalt, nickel and copper.
Currently, most Li-ion battery recyclers focus on recovering cobalt from LiCoO2 cathode material or through the recovery of Co and Ni from the cathode materials via a high temperature pyrometallurgical approach. We propose a new methodology that uses a low temperature hydrometallurgical approach that has the advantage of having high efficiency of recovery. This process works regardless of the Li-ion batteries cathode chemistry and recovers Co, Ni, and Mn in the form of their hydroxides, which when sintered with recovered Li2CO3 produces new LiNi0.33Mn0.33Co0.33O2 cathode materials. The regenerated cathode material, LiNi0.33Mn0.33Co0.33O2 , has been tested and exhibits good electrochemical performance.
The process starts by discharging spent Li-ion batteries so they can be shredded safely. The steel casing is removed from the shredded material with a magnet. Then the electrolyte is removed by solvent extraction, after which the aluminum is dissolved in a sodium hydroxide solution. The remaining material is sieved to separate the cathode material from the plastics and copper. The cathode material is leached into an acidic solution and copper, aluminum and iron impurities are removed at pH 6.5 by precipitating out their hydroxides. The ratio of Co:Ni:Mn is adjusted to 1:1:1 and the product is precipitated out at pH 11. Sodium bicarbonate is added to the remaining solution to precipitate out lithium bicarbonate. The lithium bicarbonate is then sintered with the recovered Co:Ni:Mn hydroxide to produce new LiNi0.33Mn0.33Co0.33O2.

Recently, nations in the world are faced with energy crisis such as depletion of fossil fuel and increasing oil price. Hence interest of people moves to electric vehicles (EV) which equip a motor operated by energy storage devices, especially lithium ion battery from vehicles which utilize a combustion engine consuming gasoline. EV in today&’s technologies, however, has many problems such as relatively short moving distance, low power density, service life of energy storage system and limited operating temperature. For these reasons almost coming from properties of battery, improving such drawbacks is one of undeniably great challenges.
LiMn2O4 in many cathode materials is most promising for large scale battery due to advantages of low cost, abundance, good thermal stability and environmental affinity. In spite of those advantages, unfortunately, the stoichiometric LiMn2O4 suffers from severe capacity fading at elevated temperature, especially above 60 degree celsius. This serious problem comes from the dissolution of manganese resulting from the disproportionate reaction of trivalent manganese (2Mn3+ → Mn2+ + Mn4+) in the presence of acidic species in electrolyte solution.
In this work, we synthesized a novel hetero-structure LiMn2O4 with surface of layered (R3-m) phase via spray drying process. Layered domain coexists at a primary particle without interphase. Our material exhibited a discharge capacity of 123mAh/g and retained about 85% capacity retention after 100th cycles at the elevated temperature (60 degree celsius). Additionally, coated electrode showed much improved rate capability and low temperature performance.

The layered structured material LiNi0.5Mn0.5O2 has been widely investigated over the past few years, and is known as a promising positive electrode material for lithium-ion batteries because of its high theoretical capacity (280 mAh/g), thermal stability and high temperature of decomposition in its fully oxidized state [1]. It is known that when the compound is made directly in Li form, a considerable amount (~10 %) of Li/Ni antisite defects are found [2]. The presence of Ni in the Li layers creates barriers for diffusion that result in a poorer rate capability of LiNi0.5Mn0.5O2 compared to LiCoO2 [3]. Synthesis of LiNi0.5Mn0.5O2 by ion exchange reaction from NaNi0.5Mn0.5O2 precursor leads to a material free of antisite defects due to the ionic radii mismatch between Na and Ni [4].
Our work is focused on the crystal-chemistry and microstructure of LiNi0.5Mn0.5O2 obtained by different ion exchange routes from NaNi0.5Mn0.5O2 as a precursor. We present a thorough structural and microstructural characterization, including anisotropic size broadening effects, antisites defects, composition and morphology of the, combining neutron and X-Ray diffraction data with high resolution transmission electron microscopy and EDAX measurements. Synthesis-microstructure-electrochemistry correlations will be shown.
Reference:
[1 ] T. Ohzuku and Y. Makimura, Chem. Lett., (2001), 642, 30
[2 ] Z. Lu, D. D. MacNeil, and J. R. Dahn, Electrochem. Solid State Lett., (2001) 4, A191
[3 ] W. S. Yoon, Y. Paik, X. Q. Yang, M. Balasubramanian, J. McBreen, C. P. Grey, Electrochem. Solid State Lett. (2002), 5, A263
[4] K. Kang, Y. S. Meng, J. Breger, C. P. Grey and G. Ceder, Science (2006), 311, 977

Cathode solubility is a potential life limiting mechanism in lithium batteries. In addition to reduction of capacity via loss of electrode material, cathode solubility also results in transition metal ions entering the electrolyte. These dissolved transition metal ions can passivate the surface of the anode, increasing resistance and limiting the current which may be drawn from the cell. The current study on cathode solubility focuses on vanadium dissolution from cathode materials relevant to batteries used for internal cardioverter defibrillators (ICD&’s). Specifically, the vanadium solubility of the oxide based material silver vanadium oxide (Ag2V4O11, SVO), and a phosphate based analogue, silver vanadium phosphorous oxide (Ag2VO2PO4, SVPO), are investigated. SVO has been successfully utilized as the cathode material for ICD batteries for over 30 years due to its safety, reliability, and high rate capability. However, it is reported that vanadium ions dissolve from SVO into the electrolyte solution and are subsequently deposited on the lithium anode, increasing the cell resistance. More recently, studies investigating the electrochemical properties of SVPO have indicated that it is a promising cathode material for high rate applications such as ICD&’s.
Vanadium dissolution profile data was recorded for the target materials and was analyzed with respect to physical characterization measurements. Kinetic analysis of the dissolution data was conducted. Further, test cells were prepared with vanadium treated anodes and used for electrochemical testing. Cells having vanadium treated anodes exhibited reduced performance. Results of the study provide evidence that cells utilizing silver vanadium phosphorous oxide will exhibit reduced cell resistance due to anode passivation resulting from cathode solubility compared to the oxide analog.

Thin film solid state Li-ion batteries (LIBs) employing inorganic, non-flammable electrolytes are inherently safe, have negligible self-discharge rates and have demonstrated extremely long cycle life. However, compared to batteries utilizing porous electrodes and liquid electrolytes, thin film LIBs have low energy and power densities, limited by the active electrode film thickness and low electrolyte conductivity. Increasing the electrode thickness to store more energy further reduces power and is ultimately limited by the fracture toughness of the active materials. Various 3D-Li ion battery (3D-LIB) designs based on trenches, inverse opals, vertical rods, and ‘sponges&’ have been proposed to improve power by arranging the anode and cathode sub-structures in close proximity, so that the Li-ion diffusion length during cycling remains short. The success of all of these designs depends on an ultra-thin, conformal electrolyte layer to electrically isolate the anode and cathode while allowing Li-ions to pass through. However, at sufficiently reduced thickness solid electrolytes can become electronically conductive and breakdown at potentials <5 V. In our presentation we will demonstrate fully operational, stable solid state LIBs with electrolyte thickness less than 100 nm. The batteries are fabricated in the form of thin film multilayers covering either flat substrates (2D-LIBs) or Si wafer with etched micro-pillar arrays (3D-LIBs) of 1.5µm spatial period. The distinctive and unique feature of our functional all-solid 3D batteries is that the cathode and anode electrodes inter-penetrate each other and are separated by ultra-thin (on the order of 200nm) electrolyte layer throughout the entire battery area (diameter 0.5mm). The 2D and 3D batteries are characterized using galvanostatic cycling, electrochemical impedance spectroscopy, SEM/FIB, and TEM. We will discuss the factors that affect electrolyte stability and how battery performance scales with electrolyte thickness.

Batteries based on polyanionic compounds as LiFePO4have much lower volumetric energy densities than those based on oxides. One strategy to increase the energy density is to consider more than one-electron transfer per redox center, and molybdenum (Mo3+/4+, Mo4+/5+, Mo5+/6+) and vanadium (V2+/3+,V3+/4+, V4+/5+) are probably the only multiple-valent elements, which can possibly enable two or more electron transfer within the acceptable voltage range (3 - 4.5 V) in phosphates. We investigate the layered structure of molybdenum (oxy)pyrophosphate (δ-(MoO2)2P2O7) as cathode, which was synthesized by heating MoO2HPO4H2O precursor at 560 °C. The synthesis temperature was selected using in-situ high-temperature X-ray diffraction depicting phase transformations of the precursor from room temperature up to 800 °C. Electrochemical evaluation reveals that up to four Li ions can be intercalated in δ-(MoO2)2P2O7 upon discharge to 2 V. Three voltage plateaus are observed at 3.2, 2.6 and 2.1 V, lower than the theoretical predictions. The first plateau corresponds to the intercalation of 1.2 Li forming δ-Li1.2(MoO2)2P2O7, the same structure is formed upon chemical lithiation with LiI. In-situ X-ray diffraction indicates two-phase reaction upon the first lithium insertion and expansion of the lithiated phase unit cell in a direction. Intercalation of the second lithium results in a different lithiated structure, which is also reversible, giving the capacity about 110 mAh/g between 2.3 and 4 V. More lithium-ion intercalation leads to loss of crystallinity and structural reversibility. The Mo reduction upon lithiation is consistent with the amount of Li intercalated as confirmed by the X-ray absorption fine structure. This research is supported as part of the Northeastern Center for Chemical Energy Storage, and Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award Number DE-SC0001294.

Conventional electrolytes in Li-ion batteries based on organic solvents or polymers with a dissolved Li-salt pose serious limitations such as flammability, difficulty of miniaturization, and serious impact to the environment if poorly disposed of or recycled. Thus, development of all-solid-state Li ion battery is highly desirable. To realize it, it is necessary to produce stable inorganic solid electrolytes with high Li ion conductivity. So far, Li ion conductors with garnet-type structure are considered as promising electrolytes because of their high conductivity and excellent stability. Li7La3Zr2O12 (LLZO) has garnet-type structure, so it has been paid much attention as a solid state Li-ion conductor because of good ionic conductivity (>10minus;4 S/cm) and stability against lithium. It is known that in LLZO two phases, i.e., cubic and tetragonal phases, exist. The cubic phase is suitable for a solid electrolyte, because the ion conductivity of cubic LLZO (~5×10-4 S/cm) is much higher than that of tetragonal one (~1.6×10minus;6 S/cm). Thus, it is very important to develop synthesis method of the cubic LLZO. In general, the cubic LLZO has been produce by conventional solid-state process at high temperature sintering, leading to volatile of Li element. To get stoichiometric cubic LLZO phase, it is essential to establish how to produce the cubic LLZO phase at low temperature. In this study, we aim to synthesis cubic LLZO at low temperature using a hydrothermal synthesis method. LiNO3, La(NO3)-6H2O, and ZrO(NO3)-2H2O were used as raw materials. Citric acid were also used as a chelating agent. These chemicals were dissolved in ultrapure water and were then mixed. The mixed aqueous solutions were introduced in a Teflon-lined autoclave with a 50 ml capacity. The autoclave was maintained at temperatures of 180 °C for 5 h and subsequently left to cool to room temperature, resulting in the production of precipitation. The obtained precipitation was thermally treated at temperatures of 300 to 1000 oC. The obtained powders were characterized by XRD, SEM, XPS, and TEM. XRD pattern revealed that the powder had some peaks assigned to the cubic LLZO phase. The ion conductivity was also investigated by electrochemical impedance spectroscopy (EIS).
Acknowledgement
This research was partially supported by Research and Development Program for Innovative Energy Efficiency Technology in 2011(23-0712004) from New Energy and Industrial Technology Development Organization (NEDO) of Japan.

Solid polymer electrolytes have been paid much attention in rechargeable lithium batteries, due to absence of electrolyte leakage, enhanced safety and design flexibility [1,2]. Development of a solid-state lithium polymer battery is dependent upon the successful identification of a suitable solid polymer electrolyte. Solid polymer electrolytes studied to date are mainly based on poly(ethylene oxide)(PEO) containing lithium salts. However, these materials have a major drawback that the ionic conductivity for practical application can only be reached at high temperature, due to the high degree of crystallinity inherent in these complexes at ambient temperature. Because of the inherent drawback of PEO-based solid polymer electrolytes, various attempts such as grafting, block copolymerization, interpenetration polymer network have been tried to incorporate PEO into a macromolecular sequence, which inhibits crystallization, while maintaining a low value of the glass transition temperature. Although these novel approaches are promising, the fact that their preparation requires nontrivial synthetic processes is a drawback for practical application. With the aim of developing highly conductive solid polymer electrolytes with high mechanical strength, we synthesized the solid polymer electrolytes supported by PEO-based electrospun nanoporous membrane. In this system, mechanically robust porous membrane can protect against electric short to assure safety reliability and to make a flexible thin film. By using these solid polymer electrolytes, the lithium polymer cells are assembled and their cycling performances are evaluated.
References
[1] F.M.Gray, Polymer Electrolytes, The Royal Society of Chemistry, Cambridge, 1997.
[2] W.A.Van Schalkwijk, B.Scrosati, Eds., Advances in Lithium-Ion Batteries, Kluwer Academic/Plenum Publishers, New York, 2003.

The use of lithium ion batteries in the portable electronic industry and now the transportation and grid sectors has caused a growing demand for high performance devices. Conventional lithium ion batteries are multi-component systems with the anode and cathode active materials determining the voltage and theoretical energy content. Current electrolyte systems of lithium ion batteries comprise a lithium salt and a mixture of carbonate solvents which to date, have allowed for the use of cathodes with 4V operating windows. These electrolyte systems are relatively conductive, and many of them form stable solid-electrolyte interphase layers to promote effective battery operation. However, carbonate-based electrolytes suffer from poor thermal stability and a limited voltage window of electrochemical stability.
The study of ionic liquids for use in energy storage applications is a relatively recent occurrence; however, they are prospective candidates because of their potential for increased electrochemical stability and lower flammability.
In this work the physical and electrochemical properties of ionic liquids based on four common cations, imidazolium, pyridinium, piperidinium, and pyrrolidinium with tetrafluoroborate and bis(trimethylsulfonyl) imide anions are systematically investigated. Cation type, anion type, and substituent chain length effects on conductivity and electrochemical stability were investigated. In addition, mixtures of ionic liquids with carbonate solvents were prepared and conductivity and electrochemical stability were determined. The effect of the addition of salt was also studied. Comparisons with conventional carbonate-based electrolyte systems are discussed to put the findings of this work into context.

Flexible electronics have been attracted a great attention to emerging applications such as roll/up displays, wearable devices, active radio frequency identification (RFID) tags, integrated circuit smart cards and implantable medical devices. To realize the commercially available flexible electronics, the development of novel energy storage devices such as flexible Li-ion batteries (LIB) and supercapacitors is essentially required. Our team demonstrated an advanced anode system of multiwall carbon nanotubes (MWCNTs) directly grown on 2D Cu by using a thermal chemical vapor deposition method and excellent LIB performance (767 mAhg^-1 at 3C and ~900 mAhg^-1 without capacity degradation up to 50 cycles) [1]. Furthermore, an ultrathin layer of alumina was coated on MWCNTs through an atomic layer deposition (ALD) method for the stability of solid electrolyte interface (SEI) layer and the enhanced LIB performance could be obtained [2]. In addition to the quality of nanomaterial based anodes, their 3D architecture design can play a significant role in achieving such high LIB performance. We previously showed MWCNTs directly grown on 3D Cu mesh anode architecture and the loading amount of MWCNTs has been demonstrated four times higher than that of MWCNTs grown on 2D Cu, resulting in 160% enhancement of specific capacity in the cycling performance [3].
In this study, we present the 3D hybrid anode structure of MWCNTs/graphene transferred over the transparent and flexible polyethylene terephthalate (PET) film. The novel structure was used as anode for LIB coin cell and exhibited reversible specific capacity of 153 mAhg^-1 at 0.17C and cycling performance of 130 mAhg^-1 up to 50 cycles of charge and discharge even at 1.7C. High electric conductivity (low sheet resistance ~95 #8486;/sq) was obtained from the structure after its bending test. During the bending test, the 3D MWCNTs/graphene was strongly bonded to the PET through high pressure sensitive adhesive coated on the PET film without visible structural damage. Moreover, any additional binder negatively affecting the LIB performance was not used for the improvement in bonding strength between 3D MWCNTs/graphene and PET. Also, it is anticipated that a commonly used roll-to-roll lamination method can be applied to high-throughput production of the novel anode structure.
References
1. I. Lahiri, S.W. Oh, J.Y. Hwang, S.J. Cho, Y.K. Sun, R. Banerjee, W.B. Choi, ACS Nano 4 (2010) 3440-3446.
2. I. Lahiri, S.M. Oh, J.Y. Hwang, C.W. Kang, M.S. Choi, H.T. Jeon, R. Banerjee, Y.K. Sun, W.B. Choi, J. Mater. Chem. 21 (2011) 13621-13626.
3. C. Kang, I. Lahiri, R. Baskaran, W.-G. Kim, Y.-K. Sun, W.B. Choi, J. of Power Sources. 219 (2012) 364-370.

Lithium/sulfur (Li-S) cells have recently attracted much attention as one of promising post lithium ion batteries which have been faced with serious performance limitations. Electrochemical reduction of sulfur has been known to be composed of a few electrode reactions and so many chemical reactions. Long-chain polysulfides (Sn2-, n > 2) generated from the reduction of sulfur generally dissolve in organic electrolytes. Chemical properties of polysulfide are strongly dependent on type of organic solvents, indicating that the performance of Li/S batteries can be directly affected by the electrolyte systems. To date, the influence of organic solvents on chemical and electrochemical properties of sulfur cathodes has not been reported. In this work, comprehensive study on the role of organic solvents in Li-S cells is carried out.

Abstract
Sulfur (S)-based materials are considered to be attractive candidates for the next generation cathodes due to the high theoretical capacity of 1672 mAh g-1, low cost and abundance of S in nature with enhanced safety [1, 2]. Yet there are several challenges preventing commercialization of S cathodes. The largest challenge is an extensive capacity degradation during cycling because of the high solubility of polysulfides in electrolytes [2]. Another challenge is highly insulating properties of S, which requires the uniform introduction of electrically conductive material into the electrode [2]. In conventional LiBs, Li anodes are never used because they form dendrites during repeated Li plating-dissolution cycles. With S cathodes, however, some of such issues can be mitigated. The formation of Li2S may self-limit the short circuit reaction processes, while some of the polysulfides deposited on Li may suppress the dendrite formations.
Many of the key Li-S processes governing the cell performance, including the polysulfide dissolution rate, the ionic transport and the solid electrolyte interphase (SEI) on the Li foil, shall be thermally activated. Therefore, in this work we were interested to reveal how this temperature may impact the performance of Li foil-S cells. In order to achieve high electrical connectivity within the S electrode, we have utilized vertically aligned carbon nanotubes (VACNTs), which have recently shown great promises for high capacity anodes [3] and cathodes [4] due to their excellent thermal and electrical properties. The cells were operated at 25, 50, 70 and 90 °C. Higher temperature operation resulted in higher specific capacity, better rate capability and more stable performance. Thicker SEI with higher content of inorganic phase formed at elevated temperatures greatly reduced both the dendrite formation and the capacity fading resulted from the irreversible losses of S. At 70 °C specific capacities up to ~700 mAh g-1 were achieved at an ultra-high current density of 3.3 A g-1[5].
Acknowledgement
The authors would like to acknowledge the support of Carl Hinners (US Navy, China Lake, CA, USA) and thank Dr. Won Il Cho for a helpful discussion. A part of the project was financially supported by Korea Institute of Science and Technology (KIST).
References
[1] Choi, N.S., Z.H. Chen, S.A. Freunberger, X.L. Ji, Y.K. Sun, K. Amine, G. Yushin, L.F. Nazar, J. Cho and P.G. Bruce, Angew. Chemie-Int. Ed., 2012. 51(40): p. 9994-10024.
[2] J.C. Guo, Y.H. Xu, C.S. Wang, Nano Letters, 11 (2011) 4288-4294.
[3] K. Evanoff, J. Khan, A.A. Balandin, A. Magasinski, W.J. Ready, T.F. Fuller, G. Yushin, Advanced Materials, 24 (2012) 533.
[4] S. Dorfler, M. Hagen, H. Althues, J. Tubke, S. Kaskel, M.J. Hoffmann, Chemical Communications, 48 (2012) 4097-4099.
[5] H. Kim, J.T. Lee and G. Yushin, JPS, 226 (2013) 256-265.

In recent years, FeS2 (natural pyrite) has been widely studied and considered to be potential electrode in the anode material for lithium-ion batteries, because some of the iron disulfide itself good properties and advantages, such as high theoretical capacity, no toxicity for low environmental impact and low cost. However, due to the lithium metal is very expensive material, secondary battery focuses on the development of low-cost battery. Sodium-ion battery is considered to be quite consistent with a choice, because of the low cost price of the sodium metal, high theoretical capacity, etc. It is possible to completely replace the similar properties of the lithium metal. But in fact, the low energy density, low output potential and capacity restriction are the problems encountered by the sodium-ion battery. In this study, we focused on the natural iron disulfide material used in the sodium-ion battery anode. We found that iron disulfide as anodic materials of sodium-ion battery (FeS2-NIB) demonstrated the first discharge and charge capacity of 730 mAh g-1 and 584 mAh g-1 at a current density of 50 mA g-1 .The irreversible capacity of first cycle is approximately 20%. Especially, the irreversible capacity of charge-discharge process after second cycle is much less. The capacity of FeS2-NIB still remained 400 mAh g-1 after 50th cycles. During rapid charge-discharge test, FeS2-NIB have high capacity of 280 mAh g-1 at a current density of 8920 mA g -1 . Overall results showed that the pure iron disulfide as anodic materials of sodium-ion battery demonstrated long cycle performance, high coulombic efficiency and good capacity retention at high charge-discharge rate. The results indicate that earth-abundant FeS2 is an extremely interesting candidate as anode materials of sodium-ion battery with a suitable electrolyte for fast intercalate/deintercalate Na ion reversibly.

Metal-oxygen batteries hold great promise as large-scale energy storage systems because of their exceptionally high energy densities. The Li/O2 battery, one of most extensively studied metal/oxygen systems, has the highest energy density of any battery system reported to date. However, its poor cycle life and unacceptable energy efficiency from a high charging overpotential are major limitations. A much lower overpotential even in the absence of catalyst was recently reported for the Na/O2 battery. This observation was unexpected because the general battery mechanism of the Na/O2 system is analogous to that of the Li/O2 cell. The origin of the low overpotential of the Na/O2 battery is still not understood. Here, we determined the origin of this unusual phenomenon by investigating the charging mechanism of the Na/O2 cell using first-principles calculations and compared it with that of the Li/O2 cell. From crystal surface calculations of NaO2, Na2O2, and Li2O2 during the oxygen evolution reaction, we found that the overpotential of the NaO2 decomposition was substantially lower than that of Li2O2 decomposition on major surfaces. We also determined the phase stability maps of the reaction products of Na/O2 and Li/O2 batteries based on the oxygen chemical potential, which explained why certain phases (i.e., NaO2, Na2O2, or Na2O for Na/O2 cells, Li2O2 or Li2O for Li/O2 cells) should be the main discharge products under normal operating conditions (~ 1 atm O2) of these batteries.

Lithium air batteries hold out great promise in the realization of long range all electric automobiles. However, poor lithium peroxide conductivity remains one of several grand challenges in the maturation of lithium air batteries. Hence routes for improving its conductivity are widely sought. It is generally accepted, that lithium peroxide&’s conductivity is rate limited by the self-trapping of charge carriers through the formation of polaron quasi-particles. In this work, we utilize first-principles methods to explore how phonons interact with delocalized electrons in Li₂O₂ to drive the formation of polarons. These fundamental insights provide a new perspective on how polaronic conduction might be engineered in lithium peroxide.

In recent years, the market for portable electronic devices, electric vehicles and hybrid electric vehicles with high-performance energy-storage systems such as supercapacitors are has been growing rapidly. And supercapacitors can play an important role in complementing the energy storage functions of batteries and fuel cells by providing back-up power supplies to protect against power disruptions. Activated carbons are the most widely used electrode materials for the supercapacitors because of their large surface area, low cost, nontoxicity and easy processability. However, their low energy storage capacity and restricted rate capability are demerits with regard to their use as an electrode material for supercapacitors.
In this presentation, we propose a method of overcoming the demerits of activated carbon such as the low energy storage capacity and restricted rate capability by using functionalized activated carbon nanoparticles (FACNs). FACNs have various functional groups on their surface. Due to the functional groups on the FACNs&’ surface, the FACNs&’ nanocomposite electrode based on the activated carbon and the crosslinkable polymer binder exhibits superior specific capacitance of 154 F/g. Furthermore, the cyclic voltammogram is still rectangular in shape even at exceedingly high scan rates of 5 V/s. These characteristics show that our proposed method is suitable for the fabrication of high-performance supercapacitors.
**This study was supported by a grant (B551179-10-01-00/ KM3000/ NK167D/ SC0860) from the cooperative R&D Program funded by the Korea Research Council Industrial Science and Technology, Republic of Korea.

High power energy storage systems are valuable for electrification of automobile. In recent years, hybridization of high energy battery (or fuel cell) and high power supercapacitors has been proposed for the next generation of hybrid electric vehicles. This type of hybridization allows a wider utilization of the battery state of charge, SOC that may lead in reducing battery size, battery (fuel cell) degradation, and cost. In this work, we describe the electrode engineering based on integration of transition metal oxide into low cost graphene to achieve over 350 F/g capacity. The multi-layer graphene is produced by thermal shock of acid intercalated graphite flakes. The metal oxide is impregnated into the optimized multi-layer graphene by solution chemistry to maintain high surface area. The metal oxide - multi-layer graphene composite is impregnated / deposited into metal foam / film, and tested in an optimized non-aqueous electrolyte in various voltage windows. The electrode and cell capacity, exceeding 350 F/g for active material have been achieved. The high rate capability of the electrode has been confirmed both in half cell and in full cell configurations. We will report the materials aspects and electrode engineering/formulation, and hybridization model of this type of high power supercapacitor with high energy batteries for future electrification of automobile.

The ever-increasing demand for energy storage to power mobile devices and to store energy from green conversion has spurred immense interest in creating nanostructured electrode materials that shows great promise to meet the demand. However, current state-of art nanostructured electrodes have not been able to reach the theoretical capacity and the cycle performance is far short from the lifetime of devices that they power. In addition, current electrode platform e.g. Li ion and lead-acid batteries, are either costly and unsafe or not environmental friendly.
Here we present a new electrode platform using materials that are abundant, inexpensive and can be fabricated using more environmentally friendly process. The porous electrode consists of high density and dispersed redox nanoparticles (Mn, Fe, Ni) supported by polymer templates. By using polymers as templates, well-dispersed, uniform and protected redox nanoparticles with controlled stoichiometry can be made in a one step process. In addition, these redox nanoparticles are directly connected to the current collector via interconnected conductive path ways created by graphene sheets and/or carbon nanotube, facilitating electron transport, while preventing agglomeration of redox centers.
We also compare storage capacity and cycle performance of the polymer template approach with other conventional methods and demonstrate its unique advantages. The potential of the use this new platform for generating alternative green rechargeable and recyclable batteries is also discussed.

The electrochemical properties of the spinel LiNi0.5Mn1.5O4 cathode material are influenced by the synthesis process, which determines the impurity phase and the distribution of Ni and Mn in the spinel structure. Taking advantage of the higher Ni/Mn contrast from using neutrons compared to X-rays, in situ neutron diffraction has been employed to quantify the phase formation/structural evolution process under continuous heating/cooling and isothermal annealing conditions. The results show that the subtle Ni and Mn ordering process occurs slowly at 700 oC and the degree of ordering can be controlled by the annealing time. At temperatures above 750 oC, the LiNi0.5Mn1.5O4 spinel phase starts to decompose into the rock- salt impurity phase accompanied by the release of O2. The rock-salt phase reverts back to the spinel phase upon cooling along with the oxygen uptake. The dynamic process of structural evolution of LiNi0.5Mn1.5O4 that was unraveled by in situ neutron diffraction is valuable for guiding the synthesis of cathode materials with desirable properties.

Developing materials with a high modulus and good lithium ion conductivity is a major challenge in the field of solid polymer electrolytes. To date, these properties have been considered to ‘trade-off&’ because a chain-relaxation mechanism conducts the lithium ions giving soft materials the advantage here; however they are also mechanically weak. Rigid materials can provide advantageous mechanical stability, yet often show insufficient ion conductivity. The modulus of soft, polymeric materials can be improved with chemical cross-linking or by adding a stiff non-ion conducting component. In the following work, these tactics are combined using a novel, co-network approach. Poly(ethylene glycol) (PEG), which is ion conductive and polystyrene (PS), which is rigid, precursor chains were end-functionalized with norbornene groups then cross-linked together using thiolene chemistry with a tetra-thiol. These telechelic precursors provided novel only end-linked, networks.
To understand the impact of polymer chain length, three networks were prepared, each with precursor molecular weights of approximately 5, 12, and 35 kg/mol. The co-networks were doped with a lithium salt during the cross-linking reaction. After solvent-removal, the monoliths show a collective average storage modulus of 90 MPa and an average ion conductivity of 10^-3.8 S/cm at 30 °C. The good ion conductivity and high modulus values are enabled via PEG-PS phase separation. The amorphous PEG phase is rubbery at room temperature which enables lithium ion transport. The PS phase is glassy and imparts mechanical stability up to approximately 100 °C, the PS glass transition temperature. Small angle x-ray scattering (SAXS) shows the phase separation in the co-networks is expectedly not well-ordered. Compared to well-ordered block copolymer systems, co-networks often show an enhanced ability to exhibit bicontinuous morphology which serves to minimize the effect of geometry on either the ion conductivity or the modulus as both phases percolate throughout the material. The relationship between M_c and the domain spacing (d, from SAXS) follows DeGennes&’s prediction of d ~ M_c^0.5. The high variation in d (22-55 nm) and the low variation in mechanical properties or ion conductivity (30 MPa and 0.19 mS/cm, respectively) with M_c shows that the overall morphology has a greater effect on the material properties than the cross-linking. This is important since it indicates the broad applicability of this novel approach. To show the adaptability of this platform, a PEG and polydimethylsiloxane co-network was synthesized using the same thiol-ene technique yielding a much softer material with a storage modulus of 0.23 MPa and an ion conductivity of 10^-4.3 S/cm at 30 °C. These results using PDMS suggest that the PS is directly responsible for the increased modulus. Overall, this chemical platform offers control over a wide range of mechanical properties, while maintaining high ion conductivity.

Lithium-sulfur batteries, often seen as the next generation of lithium-ion batteries, are very promising because of their high theoretical capacity (1672 mAh/g), low cost and easy accessibility of sulfur. However, major challenges exist that preclude these systems from reaching commercialization, including low electronic conductivity of sulfur and capacity loss upon cycling. A common technique to mitigate these issues has been to use a variety of conductive and porous carbon scaffolds for sulfur impregnation, all with varying porous architectures.
Here in our research group, we have synthesized a series of hierarchical porous carbons (HPCs) with highly tunable porosity along all three different length scales (macro-, meso- and micro-). In this work, we present the performance of these HPCs when used as electrically conductive hosts for sulfur and utilized as the cathode in a lithium-sulfur battery. The results revealed high initial capacities and good capacity retention after 300 cycles, even at high charge/discharge rates (1C). Moreover, the facile tunable meso- and microporosity of these HPCs, allows them to serve as excellent model systems to elucidate the fundamental role of the different porosities. Parameters such as mesoporosity (mesopore-size) and microporosity were systematically investigated. The effect of sulfur loading in carbons with different mesopore size and pore volumes on cyclic stability was also studied.

Metal-air batteries are extensively investigated for high density energy storage for xEVs and large scale ESSs. Specifically, lithium-air batteries have very high theoretical specific energy of 11,680 Wh/kg (based on Li + O2 → Li2O2) which is much larger than the theoretical capacity of Li ion batteries, 400 Wh/kg. However, practical applications of Li-air battery have serious material challenges including the performance of cathode catalyst which shows drastic cyclic degradation and low round trip efficiency arising from large potential difference between ORR (oxygen reduction reaction) and OER (oxygen evolution reaction). To overcome these challenges, diverse catalyst material candidates have been examined including metal alloy (e.g., PtAu) and oxide catalysts.
Bruce et al. have shown that α-MnO2 has a superior catalytic activity for lithium-air batteries.[1] Shao-Horn et al. have shown that the catalytic activity of perovskite oxide in metal-air batteries can be explained by eg orbital filling of surface transition metal atoms.[2] Recently, Cho et al. have shown that Mn-mullite (SmMn2O5) catalyst can give 45% higher performance than Pt for oxidation reactions.[3] All these recent findings suggests that Mn oxide is a promising catalyst for ORR and OER in Li-air battery cathode, and it is important to develop a fundamental understanding on their atomic, electronic structures and catalytic reaction kinetics. For this purpose, we have applied density functional theory (DFT) method to Mn oxides (α-MnO2 and Mn-mullite) and investigated their material properties.
Our DFT analysis is validated by experimental study of Li-air cell including α-MnO2 and Mn-mullite catalysts in the air cathode. Both DFT modeling and experimental study on MnO2 show that less stable MnO2 surface with higher number of Mn3+ surface metal atoms facilitate the ORR and OER catalytic reactions leading to unusually high capacity at very high current density. The performance of Mn-mullite (SmMn2O5) and Mn perovskite (SmMnO3) catalysts are also examined and compared with MnO2 catalalysts. The fundamental understanding gained from DFT modeling and experimental validation provides an important insight to further develop oxide catalyst which would minimize cyclic degradation and potential difference between ORR and OER. We will explore possible catalytic peroformance of mullite-family catalyst, RM2O5 (R = rare earth or 3+ ion; M = MnFe mixture) for Li-air battery applications.
This work was supported by the NRF of Korea through WCU program (Grant No. R-31-10083-0), and by the MKE of Korea (Grant No. 10041589).
1. Debart, A.; Paterson, A.; Bao, J.; Bruce, P. G. Angew. Chem. Int. Ed. 2008, 47, 4521.
2. Suntivich, J; Gasteiger, H.A.; Yabuuchi, N.; Nakanishi, H.; Goodenough, J.B; Shao-Horn, Y. Nature Chem. 2011, 1.
3. Wang, W.; McCool, G.; Kapur, N.; Yuan, G.; Shan, B.; Nguyen, M.; Graham, U. M.; Davis, B. H.; Jacobs, G.; Cho, K.; Hao, X. Science 2012, 337, 832-835.

The demand for green energy has significantly increased with the rapid development of economy and population. Rechargeable lithium batteries and supercapacitors have been widely used for consumer electronics and are desirable for applying efficient large scale electrical energy store, hybrid electric vehicles (HEV) and electric vehicles (EV), due to their high energy density and good environment compatibility. Remarkably, nanomaterials have attracted increasing interest because they can offer a range of unique advantages in energy storage fields. Although the electrochemical properties were improved, the performance of energy storage devices is still needed be further enhanced.
The enhanced electrochemical performance of electrodes depends on not only the material intrinsic characteristics, but also the designed morphologies. Owing to the high surface energy, nanomaterials are often self-aggregated, which reduces the effective contact areas of active materials. Ultralong hierarchical vanadium oxide nanowires constructed from attached short vanadium oxide nanorods with length up to several millimeters were synthesized by electrospinning. The self-aggregation of the unique “nanorod-in-nanowire” structures could be reduced because of the attachment of nanorods in the ultralong nanowires, which can keep the effective contact areas of active materials and fully realize the advantage of nanomaterial-based cathodes. Then, an initial capacity up 390 mAh g-1 was obtained.
The volume changes during cycles lead to the structure damage. Nanostructure with some buffered section in the interior of structure could promptly accommodate the volume changes during rapid ion insertion/deinsertion, and then enhance the structure stability. Nanoscroll buffered hybrid nanostructural vanadium oxides composed of nanobelts and nanowires were synthesized through hydrothermal-driven splitting and self-rolled method. The hybrid nanostructure with buffered section is able to offer facile strain relaxation and shorten the lithium ion diffusion distances. Excellent cycle life with capacity retention over 82% after 1000 cycles at ~9 C was achieved.
Heterogeneous materials with the synergistic contribution from different active materials have the advantages of further improving the electrochemical performance. Hierarchical MnMoO4/CoMoO4 heterostructures were successfully prepared on the backbone material MnMoO4 by a simple refluxing method under mild conditions. The asymmetric supercapacitors based on the hierarchical heterostructured nanowires showed a high specific capacitance and good reversibility with a cycling efficiency of 98% after 1,000 cycles. Further, the design of some desirable interfaces is able to build multifunctional nanostructures, which will be promising for a large spectrum of device applications.

While graphite anodes are common in lithium-ion batteries; there are alternatives which are more suitable for large-scale applications power-oriented with emphasis on safety and rate capability. Among them the lithium titanium oxide (Li4Ti5O12, LTO) spinel has drawn considerable interest because of several highly desirable features: safe lithiation potential (~1.5V), low cost, and negligible volume changes upon Li+ insertion and extraction. However, LTO is an insulator because of the empty 3d states of tetravalent titanium in LTO. In this project, carbon-encapsulated F-doped LTO composites (C-FLTO) were produced by lithiating a TiO2 precursor in a high temperature solid state reaction. Through the careful control of the amount of carbon precursor (D(+)-glucose monohydrate) used in the process, the final product was LTO encapsulated with a continuous layer of nanocarbon. The carbon encapsulation served a dual function: preserving the special ball-in-ball morphology of TiO2 during its transformation to LTO, and providing an expressway for electron conduction. Fluorine doping of the O sites in the LTO lattice not only improved the conductivity of insulating LTO through the creation of trivalent titanium (Ti3+) cations, but also contributed to the structural robustness of the electrode in repeated lithiation and de-lithiation. The best performing LTO-based anode material delivered a large discharge capacity of ~ 160 mA h g-1 at the 1C rate for over 200 cycles, as well as an extremely high rate performance up to 140 C.

Graphene-based nanomaterials occupy the center stage of current research with respect to the investigation of new and advanced anode materials for Lithium-ion batteries. Whether as phase pure material or as nanocomposites along with various metal oxides, graphene has already been proven of bearing the capabilities to play a key role in the development of next generation rechargeable batteries. In this work, we would like to present a facile microwave assisted reaction for the fabrication of functional graphene/metal oxide nanocomposites. The reduction of graphene oxide (GO) with M2+ ions (M = Sn, Fe, Co) in aqueous media is shown to offer distinct advantages such as effective separation of single and few layered graphene by in situ formed metal oxide nanoparticles as well as stabilization of the oxide phase during electrochemical cycling, leading to anode materials exhibiting high capacities and stable cycling performances. Additionally, the incorporation of different nitrogen-sites (i.e. graphitic, pyrrolic and pyridinic) was shown to further improve the performance of graphene-based nanomaterials. Due to defects in the pyridinic and pyrrolic environments an electron-accepting tendency arises, thus leading to higher binding energies as well as an increased amount of binding sites for Li atoms.

Due to their high cycling stability and small volume expansion during lithiation/delithiation, titanium dioxides (TiO2) exhibit great promising application in lithium ion battery (LIB). However the poor lithium ionic and electrical conductivities limit the charge/discharge rate in bulk TiO2 materials. It has been believed that making nanostructured TiO2 can dramatically enhance their conductivity and lithium ionic [1]. Very recently, it was found that aligned nanotube arrays could provide a promising morphology for LIB negative electrodes due to their high accessible surface area for lithium transportation between electrolyte and solid matrix, the short Li+ diffusion path length in the solid phase, and their tubular structure accommodating the expansion and contraction occurring during lithiation and delithiation [2]. However, the reported TiO2 nanotube arrays [1, 2] used as negative electrode were mainly amorphous, exhibiting lower conductivity compared with crystalline TiO2.
Herein, TiO2 nanotube arrays with different geometry structure have been synthesized by tuning outer voltage during anodization in ethylene glycol solution containing 0.3 wt. % NH4HF2 and 5 vol. % de-ionized water. To improve their conductivity, the anodized TNTs were annealed under Argon or air atmosphere. The effect of the outer voltage on TiO2 nanotube arrays&’ performance as negative electrode was investigated. The results reveal that the capacity of TiO2 nanotube arrays as negative electrode decreases with the outer voltage. The possible reason could be that the thickness of the tube increase with the outer voltage, resulting the higher resistance of lithium transferring from electrolyte to solid matrix electrode. What&’s more, the samples annealed at Argon atmosphere showed higher capability than those annealed at air atmosphere. This phenomena are found to be attributed to the following reasons: 1) the thickness between TiO2 nanotube and the metal matrix will increase during annealing at air atmosphere compared to the sample annealed at Argon atmosphere; 2) the conductivity of the sample annealed at air atmosphere might be lower than that of the sample annealed at Argon atmosphere, the reason may be that some TiO2 was in-situ reduced by the carbon generated from the decomposition of the EG adsorbed in the nanotubes during annealing in Argon atmosphere.
[1] JR Gonzalez, R Alcantara, F Nacimiento, GF Ortiz, JL Tirado, E Zhecheva, R Stoyanova. J. Phys. Chem. C, 2012, 116: 20182-20190.
[2] QL Wu, JC Li, RD Deshpande, N Subramanian, SE Rankin, FQ Yang, YT Cheng. J. Phys. Chem. C, 2012, 116: 18669-18677.

SnO2 has been widely used for Na batteries due to its abundant sources and low price. Here we have analyzed the failure mechanism of SnO2 nanowires used in Na-ion batteries based on novel in-situ TEM observations. The structural and chemical evolution of the SnO2 nanowires is visualized directly during electrochemical cycling. The SnO2 changes to a NaxSn-core and Na2O -shell structure after Na+ insertion; and the core finally crystallized into Na15Sn4 after complete Na insertion. Upon desodiation, the core shrank significantly, breaking the nanowire into pieces linked by the Na2O shell. Significant difference exists between the lithiation and sodiation processes as observed by in-situ TEM. Huge amount of dislocation clouds formed in the reaction front during lithitaion, while no such signature is seen for sodiation process. DFT calculations are used to explain the critical difference in those two processes. The present work provides key insight for advanced designs of SnO2 anode with enhanced cycling stability for Na-ion battery.

Recently we reported on synthesis of a new family of two-dimensional early transition metal carbides, so-called MXenes. They were produced by etching A atoms from MAX phases, which are a large family (+60 phases) of layered hexagonal ternary carbides with composition of M_n+1AX_n; where M is early transition metal, A is mainly group A element, X is carbon or nitrogen, and n=1, 2, or 3. Herein we report on use of four different MXenes (Ti₂C, V₂C, Nb₂C, and Ti₃C₂) as electrode materials in lithium-ion batteries. In all the cases MXenes showed an excellent capability to handle high cycling rates. Flexible additive-free electrodes of delaminated Ti₃C₂ showed a reversible capacity of 410 mAhg^-1 at 1 C rate and 110 mAhg^-1 at 36 C. We found that each MXene has its own active voltage window. Considering that MXenes could be produced as solid solutions, where different M atoms with different concentrations can occupy M sites, the intercalation potential and working voltage window could be controlled by tuning the MXene composition.

The theoretical capacity (1600 mAhg^-1) of germanium anodes, although not as high as silicon, is more than five times higher than graphite anodes. Nevertheless, large volume changes during lithiation and delithiation are believed to cause crack formation leading to particle pulverization and capacity fading in both Ge and Si anodes. Furthermore, Coulombic inefficiencies of Ge and Si have been attributed to the fracturing of the SEI layer due to the dramatic volume changes, which leads to a continual growth of SEI and a significant depletion of Li-ions participating in the reversible electrochemistry.
We will present in situ transmission X-ray microscopy results, which directly track the crack formation in micron-sized particles during battery operation. Additionally, from 2D images collected as a battery is rotated, we have reconstructed 3D images of particles at different points along the electrochemical cycle. With this in situ information we can quantify the volume change in individual particles and measure the change in porosity or density as the anode delithiates.

In lithium-ion battery, lithiation of crystalline silicon proceeds by the movement of an atomically-sharp reaction front which separates the pristine crystalline silicon phase and the fully-lithiated amorphous Li_3.75 Si phase. The velocity of the reaction front is limited by the reaction rate at the front rather than by the diffusivity of lithium in the amorphous lithiated phase. Recent experimental evidence on nano-particle and nano-wire silicon anodes showed an initial rapid velocity of reaction front at the initial stage of lithiation, followed by an apparent slowing or even halting of the reaction front. This intriguing phenomenon is attributed to the lithiation-induced mechanical stresses across the reaction front which is believed to play an important role in the kinetics of reaction at the front. In previous studies, electro-chemo-mechanical driving force for the movement of lithiation front has been identified and effect of mechanical stress on reaction rate in solid spherical and cylindrical anodes has been investigated. Here, through theoretical formulation and finite element analysis, we presented a comprehensive study on lithiation-induced stress distribution and its contribution on driving force of lithiation in hollow nano-sphere or nano-wire anodes with different mechanical constraint at the inner surface. Our results reveal hollow nano-sphere (nano-wire) anodes can be more efficiently lithiated than their solid counterparts and thus shed light on the optimal design of high performance anodes of lithium-ion battery.

Tin-based anodes are promising for increasing both the volumetric and gravimetric energy density of lithium ion batteries. However, the comparatively high specific capacity of such materials is associated with a volume expansion of up to 250 %. This volume expansion has been shown to have a profound effect on the cycle life of the electrodes. Both nanostructured tin-based materials and nanocomposites can be used to minimize to a certain extent these negative side effects, but their fabrication typically involves intricate synthetic routes[1] or additives like graphene which are not yet suitable for large-scale application.[2]
In the present work, we focus on highly crystalline sub-20 nm diameter tin oxide (SnO₂) nanoparticles which can be readily produced by a non-aqueous sol-gel type route.[3] In addition, we show that the synthesis method employed here can be extended to a series of technologically important tin-based materials, including Sb:SnO₂ (ATO) and F:SnO₂ (FTO). All of these oxides exhibit promising electrochemical properties and lend themselves to the fabrication of high-quality electrodes with both enhanced cycle life and coulombic efficiency.
The electrochemical reaction on the first discharge cycle is characterized by the conversion of the particles to nanoscale lithium oxide and metallic tin according to:
SnO₂ + 4Li+ + 4e^- → 2Li₂O + Sn
The subsequent lithiation/delithiation of tin up to Li_4.4Sn leads to a theoretical capacity of 781 mAh/g (based on SnO₂) which is more than two times the specific capacity of graphite.[4]
[1] Zhang, W.-M.; Hu, J.-S.; Guo, Y.-G.; Zheng, S.-F.; Zhong, L.-S.; Song, W.-G.; Wan, L.-J. Adv. Mater. 2008, 20, 1160.
[2] Lian, P.; Zhu, X.; Liang, S.; Li, Z.; Yang, W.; Wang, H. Electrochim. Acta 2011, 56, 4532.
[3] Ba, J.; Polleux, J.; Antonietti, M.; Niederberger, M. Adv. Mater. 2005, 17, 2509.
[4] Courtney, I.; Dahn, J. R. J. Electrochem. Soc. 1997, 144, 2045.

Transition metals oxides (TMOs) with their high theoretical capacity, low cost, safety, environmental friendliness and natural abundance attract considerable attention for electrode applications in lithium-ion batteries. The problems with these materials are however: rapid capacity loss due to large volume changes during charging/discharging cycling and low electronic conductivity. Nevertheless, numerous recent studies have shown that combining TMOs with carbonaceous materials helps to accommodate the volume change-related stress as well as to improve overall conductivity of the electrode. In particular, highly enhanced electrochemical performance has been demonstrated for various nanocomposites of TMOs with graphene-like structures.
Some of the most interesting TMOs for electrode applications are manganese oxides including lithiated spinel phase LiMn2O4 with high cathode capacity of 148 mAh/g and MnO with theoretical anode capacity of 755 mAhg-1 and small overpotential. Here, in this work, we report a novel synthesis method for producing nanocomposites consisting of nanoparticles of these manganese oxides embedded in graphene oxide-like matrix. These nanocomposites are formed spontaneously, in the form of hollow spheres or foams, during thermal processing of xerogels obtained from lithium and manganese acetate salts and organic chelating agents dissolved in aqueous solution. By using the same xerogels, graphene oxide-based nanocomposites of MnO or LiMn2O4 can be formed, depending on the chosen thermal processing route. We will present a detailed characterization of such nanocomposites and propose their formation mechanism. Moreover, results of the electrochemical testing of these materials will also be presented and discussed.

Flow batteries have historically been based on electronically insulating redox-active solutions for which charge transfer occurs only at the interface with a stationary current collector. We explore for several electrochemical systems an alternative approach in which flow electrodes of either solution or suspension type are rendered electronically conductive through incorporation of a percolating network of nanoscale electronic conductor particles that permits distributed charge transfer throughout the flow electrode (i.e., an “infinite” current collector). Fluid electrodes exhibiting percolation at less than 3 vol% solids and reaching electronic transference number te up to 0.5 are demonstrated in aqueous and non-aqueous suspension electrodes and nonaqeuous solution electrodes. Electrochemical kinetics are found to be strongly dependent on specific materials and electrode microstructure. Contributions to cell impedance are characterized, and flow cell operating protocols that optimize coulombic and energy efficiency during concurrent flow and electrochemical utilization are illustrated.
Financial support by the U.S. Department of Energy, Joint Center for Energy Storage Research (JCESR), is gratefully acknowledged.

``Electrochemical shock" - the electrochemical cycling induced mechanical degradation of electrochemical active materials—contributes to impedance growth in ion-intercalation batteries. The root cause of electrochemical shock is the shape change during lithium (de)intercalation, which is often large and/or anisotropic.
In this talk, we present in-situ acoustic emission measurements and corroborating micromechanical models which demonstrate and explain C-rate-independent electrochemical shock in cubic spinel materials. Unlike layered and olivine materials, which have anisotropic shape changes, the cubic spinels undergo isotropic strains as composition is varied. However, these materials, such as LiMn₂O₄ and LiNi_0.5Mn_1.5O₄ undergo first-order phase-transformations between two cubic phases. The linear misfit strains between the coexisting cubic phases are ~1%, which is sufficient to drive fracture of particles on the micron scale. This is analogous to the coherency-stress fracture which occurs in LiFePO₄, but the misfit strain is isotropic in the spinels.
C-Rate-independent electrochemical shock in these spinel materials can be averted by controlling the particle size and/or by identifying chemical modifications which reduce the misfit strain between the coexisting cubic phases. We will demonstrate a high voltage spinel cathode composition designed to completely avert this mechanism of failure.
This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Award No. DE-SC0002633

Ex-situ powder neutron diffraction (ND) was employed to obtain deeper understanding on phase transformation mechanism leading to the voltage fade phenomena in a high energy density layered-layered Li-Mn rich compound (Li_1.2Co_0.1Mn_0.55Ni_0.15O₂ or TodaHE5050). Full pouch cells were assembled at battery manufacturing facility, Oak Ridge National Laboratory (ORNL). In the first step, all the pouch cells went thru a formation cycle and then cycled between 2.5V to 4.7V @20mA/g for 25 cycles. Cells were stopped at different state of charge after two and 25 cycles in order to monitor the structural transformation. The ND experiment was conducted at POWGEN beam line at spallation neutron sources, ORNL. The collected ND patterns from pristine and cycled TodaHE5050 powder were simulated by Rietveld method by using GSAS and EXPGUI software. For pristine material, the monoclinic Li₂MO₃ (M=Co, Mn, Ni) with {Li_1-xNi_x}^2c{Li_1-yNi_y}^4h [{Li_0.364Ni_0.266Mn_0.3694}^2b {Li_0.128Ni_0.0494Mn_0.6726Co_0.15)^4g] O⁴ⁱO^8j ; where x= 0.0043; y= 0.01 composition (model 1) or a composite model of monoclinic Li₂MnO₃ and trigonal LiMO₂ (M=Co, Mn, Ni) with as 0.50 {Li_1-xNi_x}^3b{Li_xCo_0.25Mn_0.375Ni_0.375-x}^3aO₂^6c.0.50 Li₂MnO₃ where x= 0.0354 composition (model 2) showed very good fits to the experimental pattern. After 2(25) cycles, the Percentage of monoclinic phase decreases in the model 2 and expansion of lattice occurred that can be evidenced from increase in c-lattice parameter. Based on the refinement parameters, after charging to 4.1V (during second cycle), the presence of Li in the tetrahedra was proposed. The ND pattern from the materials after 2(25) cycles (in discharged state, 3.2V) were simulated by adding a spinel type phase (Li₂Mn₂O₄or LiMn₂O₄). The structural information from the pristine and cycled TodaHE5050 samples explaining the voltage fade phenomena will be presented.
Acknowledgements: This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy for the Vehicle Technologies Office's Applied Battery Research Program. Research conducted at ORNL's Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy. Authors thank Dr. Daniel Abraham and Dr. Jason R. Croy from Argonne National Laboratory (ANL) for useful discussion on structural analysis and Bryant Polzin from ANL for supplying TodaHE5050 for neutron study.

Understanding Mn dissolution during lithium-ion battery operation and its effects on battery cycle life is a key step in the development of robust battery technology for electric vehicles. It has been speculated that Mn dissolution proceeds with a hydrofluoric acid (HF) - induced surface disproportionation reaction (2 Mn3+ -> Mn2+ + Mn4+) at the cathode electrode. The soluble Mn2+ ions migrate to and then precipitate at the anode electrode. In this work, we fabricated full cells (natural graphite / Li1.05Mn2O4) and performed accelerated Mn dissolution tests, i.e., calendar aging at 55 degC for 100 hrs followed by voltage cycling for 100 times at 55 degC with a voltage window of 3 - 4.8 V at a C/3 rate. Afterwards we studied the Mn distribution, microstructure, and chemistry at the graphite anode by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). To avoid direct contact of specimens with air, an air protection / vacuum transfer sample holder was used to transfer cross-sectional specimens (prepared by focused ion beam - FIB) from the FIB-SEM to the TEM. Similarly, XPS samples were transferred from the glovebox to the XPS chamber under vacuum. Cross-sectional postmortem analyses show three distinctly different layers present on the surface of the graphite anode: 1) metallic Mn particle band (with particle size up to 20 nm and band thickness up to 60 nm), 2) solid electrolyte interphase (SEI) containing LiF (thickness up to 200 nm), and 3) top surface layer containing MnF2 and LiF (thickness up to 40 nm). Finally, we will discuss the underlying mechanisms for the formation of the multiple layers with Mn presence in either metallic Mn or ionic MnF2, and the important implications to the battery cycle life.

Impedance spectroscopy represents a rich and inter-related area of science that has been applied to a large number of important areas of research, including those associated with energy systems. In laboratory settings, impedance is used to study the kinetics and mechanisms of electrochemical reactions. Impedance spectroscopy is also applied in industrial applications to quality control and constitutes the basis of a class of sensors.
Impedance spectroscopy is attractive for battery studies because it provides a non-destructive in-situ evaluation of electrochemical properties, and it is very sensitive to factors that influence the rates of electrochemical reactions. The current driving issue in impedance spectroscopy is the difficulty of interpreting impedance spectra in terms of physically meaningful information. The quantities measured, such as current and potential for electrochemical or electronic systems, are macroscopic values that represent the spatial average of individual events. These quantities are influenced by desired physical properties, such as diffusivity, rate constants, and viscosity, but impedance cannot provide a direct measure of physical properties or a direct visualization of individual events. Interpretation is generally based on use of a deterministic model that describes the physics of the system under study.
The objective of this presentation is to illustrate the use of impedance spectroscopy for the study of battery systems. The presentation will provide the results of impedance measurements on commercial LiCoO2 coin cells. The impedance response was shown to be very sensitive to state-of-charge, temperature, and abuse such as overcharging and over-discharging. A process model was developed to reveal the influence of these conditions on electrochemical parameters.

Besides conventional lithium storage mechanisms, a novel interfacial storage mode was predicted to occur in M/LiX nanocomposites (M stands for any electron conductor, e.g. metal, which does not alloy with Li). According to this mechanism, the individual charges (Li+, e-) are stored in the space charge layers, i.e., Li+ is accommodated at the Li2O side of the boundary, while the e- is restricted to the metal side. As neither of the composites could store Li by itself, this is called ‘job-sharing&’ mechanism [1]. Recently, a thermodynamic model for interfacial storage was developed, which describes both semi-infinite and mesoscopic boundary conditions [2]. In this contribution, we present that the predicted power law for the Li-activity dependence of the capacity for a semi-infinite model can be reproduced reversibly, in both Li2O-Ru and LiF-Ni composites systems. Further exploitation of the interfacial storage mechanism may provide interesting information as to better compromise power and energy density for Li-ion batteries. Moreover, the correlations allow for a generalized storage picture of nanocrystals.
Reference:
[1] J. Jamnik and J. Maier, Phys. Chem. Chem. Phys., 5, 5215-5220 (2003).
[2] J. Maier, Angew. Chem. Int. Ed., 52(19), 4998-5026 (2013).

In order to accomplish high power density in all-solid-state rechargeable batteries used oxide electrolyte, self-forming electrode composed of LTO and LLTO was produced by means of melting and solidification. The configuration and electrochemical properties of the self-forming electrode were investigated. In the electrode there were no products except for LTO and LLTO and they were entirely-contacted each other. All-solid-state batteries composed of (LTO and LLTO)/LIPON/Li configuration was operated successfully. These results reveal that self-forming electrode is available for all-solid-state rechargeable batteries.

High specific energy, high power density, long cycle life, low cost and safer batteries are required for the advancement of electric vehicles. Current Li-ion batteries (LIBs) have highest energy density but they suffer from low power density. Energy is stored in LIBs by virtue of reversible Coulombic reactions occurring at both electrodes involving slow charge transfer in the bulk electrode materials and limited diffusion of ions from one electrode to the other. On the other extreme, electric double-layer supercapacitors store energy through accumulation of ions on the electrode surface, have very low energy storage capacity but very high power density. By combining lithium iron phosphate (LiFePO4), a high-energy density LIB material, with poly(2,2,6,6-tetramethyl-1-piperinidyloxy-4-yl methacrylate) (PTMA), a high-power density redox capacitor, we construct a high performance hybridized lithium battery electrode. The voltammetry response of the hybrid battery electrode contains two pairs of reversible redox couples at low scan rates. At high scan rates, the two oxidation peaks converge suggestive of electrochemical hybridization. The polarization in oxidation is limited by PTMA, avoiding voltage abuse on LiFePO4 component. The hybrid electrode shows enhanced capacity retention, 17.4% capacity loss after 1,500 cycles at 5C charge/discharge rate, mimicking the PTMA electrode behavior rather than that of LiFePO4. Electrochemical impedance spectroscopy reveals improved charge transfer after cycling, consistent with an activation mechanism. The influence of the hybrid electrode configuration and composition on the battery performance is also detailed. Kinetically controlled fast hybrid electrode charging leads to an electrochemical paradox: generation and co-existence of higher redox potential species (PTMA) in the oxidized form with lower redox potential species (LiFePO4) in the reduced form. Being thermodynamically unstable, this configuration forces an internal charge transfer process that equilibrates the redox state of the hybridized species, leading primarily to charging of LiFePO4. This translates into a highly relevant technological fact: whenever the electrode needs to be recharged, the rapid response of PTMA ensures the fast recharge. As such, >90% state-of-charge in the hybrid battery is reached within a five minutes time window of current pulse and relaxation sequences [1].
[1] A. Vlad et al. in preparation.

Nanostructured lithium-ion battery electrodes have demonstrated high power density, due to the high electrode/electrolyte contact area, and short diffusion paths for ions and electrons. Application of nanomaterials for microbatteries can increase surface area without increasing electrode footprint resulting in improved performance. While many studies have focused on testing nanostructured electrodes with liquid electrolytes, use of solid electrolytes offers substantial advantages for the batteries safety and cycle life. The high surface area and porosity of nanostructured electrodes impose challenges to achieve conformal and pinhole-free electrolyte coatings, which are needed for electrical isolation of the anode and cathode while maintaining electrode/electrolyte contact. In this work, we demonstrate integration of hierarchical 3D nanostructured electrodes with solid polymer electrolyte and report the electrochemical performance of this novel system.
Electrodes were fabricated using self-assembly of Tobacco mosaic virus (TMV) nanotemplates. The TMV is a 300 nm long cylindrical plant virus with an outer diameter of 18 nm. It tends to self-align forming a 1-3 mu;m thick porous layer made of interconnecting viral rods. The hierarchical 3D electrodes consisted of an array of electroplated gold micropillars coated with the TMV nanotemplate followed by electroless nickel coating and atomic layer deposition of V2O5. In electrochemical experiments with a liquid electrolyte, we have shown that this architecture enables high energy and high power densities. The solid polymer electrolyte was prepared by mixing poly (ethylene oxide), PEO, homopolymer, LiBOB salt and triethyl sulfonium bis(oxalato) borate ionic liquid in DMF. Four layers were cast onto the hierarchical electrodes, and scanning electron microscopy revealed that a conformal coating can be achieved. The casting method permits the polymer electrolyte to penetrate the highly porous 3D TMV-structured electrode. Electrochemical experiments were carried out in coin cells with Li metal counter electrode. Coin cells were annealed at 75°C for 3 hours before electrochemical testing. Cycling studies were performed at 40°C at various current rates in the voltage range of 2.5 - 3.6 V. Discharge/charge curves indicate that at low current rates the hierarchical electrode/polymer electrolyte system exhibits two plateaus at 3.1 and 3.3 V, in agreement with Li intercalation into V2O5. At higher current rates the plateaus merge, indicating slow charge transfer kinetics. In this work, we will provide a systematic study of the system at different temperatures and current rates.
In summary, virus-structured hierarchical electrodes can be readily integrated with a polymer electrolyte to produce robust high-surface area solid-state electrode/electrolyte interfaces. This work demonstrates a novel approach towards fabrication of the all-solid-state 3D lithium-ion microbattery with hierarchically-structured electrodes.

Cellular metabolism comprises energy transduction machineries that operate by a series of redox-active components for storing energies from nutrients, which are transduced into high-energy intermediates for cellular works such as chemical synthesis, transport, and movement.
Biological energy transduction mechanism hints at the construction of a man-made energy storage system. Since the pioneering work by Tarascon et al.[1] towards a sustainable lithium rechargeable battery received significant resonance, organic materials such as carbonyl, carboxyl, or quinone-based compounds have been demonstrated to be bio-inspired organic electrodes.[2, 3] The imitation of redox-active plastoquinone and ubiquinone cofactors[4] through the utilization of redox active C=O functionalities in organic electrodes is a significant step-forward to biomimetic energy storage. However, the biological energy transduction is based on numerous redox centers of versatile functionalities available in nature, not limited to the simple redox active C=O functionalities. Consideration of how natural energy transduction systems function at organelle or cellular levels by elucidating the basic components and their operating principles selected by evolution will enrich the biomimetic strategy for efficient and green energy storage.
Herein, we propose new-type of redox active organic molecules containing C=N functionality, where most interest in organic electrodes has focused on the molecules with C=O functionalities, such as carbonyl, carboxylate, or quinone-based molecules [5]. Flavins, a key redox element in respiration and photosynthesis, facilitate either one- or two-electron-transfer redox processes accompanying proton transfer at nitrogen atoms of diazabutadiene motif during cellular metabolism. We have discovered that the protonation sites of a riboflavin molecule can capture two lithium ions reversibly exhibiting a high capacity of 174 mAh/g, which is comparable to that of LiFePO4. The combined ex situ characterizations and density-functional theory(DFT)-based calculation revealed that the redox reaction occurs via the two successive single-electron transfer steps at nitrogen atoms of diazabutadiene motif, which is analogous to the proton-coupled electron transfer of flavoenzymes in nature. We also demonstrated that the capacity and voltage can be tuned by the substitution of flavin cofactors, which opens up new principles in electrode design. This kind of bio-electrode is particularly unprecedented for lithium rechargeable batteries.
[1] H. Chen, M. Armand, G. Demailly, F. Dolhem, P. Poizot, J.M. Tarascon, ChemSusChem 2008, 1, 348.
[2] Z. Song, H. Zhan, Y. Zhou, Chem. Commun. 2009, 448.
[3] M. Armand, S. Grugeon, H. Vezin, S. Laruelle, P. Ribière, P. Poizot, J.M. Tarascon, Nat. Mater. 2009, 8, 120.
[4] P. Poizot, F. Dolhem, Energy Environ. Sci. 2011, 4, 2003.
[5] M. Lee, J. Hong, D.-H. Seo, D.H. Nam, K.T. Nam, K. Kang, C.B. Park, Angew. Chem. Int. Ed. 2013, in press

A series of transition metal oxides xA2MnO3 (1-x)Ay(NiMn)O2 (A=Li+, Na+ the mobile species) are capable of storing energy reversibly in lithium ion and sodium ion batteries. These oxides have intriguing and complex features including nanometer-scale phase separation upon cycling and dynamic cation redistribution at various state of charge, that significantly affect the mobility of the guest species. We investigate the high-energy cathode materials Li-excess layered oxide compounds by combining both computational and experimental methods. The bulk and surface structures of the compounds at different state of charge are characterized by synchrotron X-Ray diffraction, neutron diffraction together with aberration corrected Scanning Transmission Electron Microscopy (a-S/TEM). Electron Energy Loss Spectroscopy (EELS) is carried out to investigate the surface changes of the samples before/after electrochemical charging/cycling. Combining first principles computational investigation with our experimental observations, a detailed and complex lithium de-intercalation mechanism is proposed for this family of Li-excess layered oxides. We show clear evidence of a new spinel-like solid phase formed on the surface of the electrode materials after high-voltage cycling. We propose effective strategies to further improve this family of materials for future battery technologies, including sodium ion batteries.

Among the Li-ion battery cathodes, the high-voltage spinel is an attractive candidate for high-power applications such as all-electric vehicles and stationary storage due to its high operating voltage (~ 4.7 V Li/Li+), good electronic conductivity, 3-dimensional Li-ion diffusion, and high power density. However, the electrochemical performance of the high-voltage spinel depends strongly on a multitude of factors including particle morphology, dopant-ion concentration, Mn oxidation state (Mn3+ content), and the degree of atomic ordering of Mn and Ni ions in the 16d octahedral sites of the spinel lattice. Understanding the influence of these various factors on the electrochemical performance is critical to develop practically viable high-voltage spinel cathodes. This presentation will show how DC magnetic measurements can be used to determine Mn3+ content and estimate the relative degree of atomic ordering amongst a set of high-voltage spinel cathodes. The low-temperature saturation magnetization of the spinel material corresponds directly to the Mn3+ ion concentration based on the ferrimagnetic ordering of spins on the 16d sites of the spinel lattice. This relationship holds for undoped, doped, and Mn-rich specimens. Additionally, the degree of cation order can be qualitatively determined based on the Curie temperature of the sample; the more atomically ordered samples exhibit a higher TC due to a decrease in frustrated magnetic interactions. These magnetic measurement techniques provide a viable way to explore the crystal chemistry of different high-voltage spinels and correlate them to electrochemical performance.

Zinc-air batteries deliver high specific energy in safe, low-cost forms, but the broad implementation of Zn-air technology is constrained by its low specific power and limited rechargeability. To bring rechargeable Zn-air batteries to practical fruition, electrochemical functionality that mirrors processes inherent to fuel cells, electrolyzers, electrochemical capacitors, and batteries must be incorporated within the battery architecture. In a 3-dimensional (3D) redesign of the air-breathing cathode, we functionalize carbon nanofoam paper with nanoscale MnOx coatings that provide both effective O₂ reduction activity (fuel-cell function; ORR) and O₂-independent pulse-power capabilities via a capacitive-delivery mechanism (electrochemical-capacitor function; F cm^-2 over 10s of seconds).^1,2 The final step to our cathode-redesign is to incorporate recharge-enabling O₂ evolution catalysts (electrolyzer function; OER) such that the resulting “trifunctional” cathode architecture expresses all three functionalities: ORR, OER, and pulse power. On the anode side, we address the Zn “dendrite problem”, which limits battery cycle life, with a radically redesigned 3D Zn sponge architecture. The interconnected Zn sponge retains an inner core of conductive metal throughout cycling that facilitates long-range electronic conductivity and provides more uniform current distribution—two properties needed for high depth-of-discharge and long-term, dendrite-free cycling (battery function). Our efforts to develop these electrode architectures and to bring them together within a fully rechargeable Zn-air cell will be described.
1. J.W. Long, C.N. Chervin, N.W. Kucko, E.S. Nelson, and D.R. Rolison, Adv. Energy Mater. 2013, 3, in the press; U.S. Patent application filed 27 September 2011.
2. C.N. Chervin, J.W. Long, N.L. Brandell, J.M. Wallace, N.W. Kucko, and D.R. Rolison, J. Power Sources 2012, 207, 191-199.

To exceed the demands of current hybrid, plug-in hybrid and electric vehicles, new battery systems with high energy density are required. Magnesium (Mg) is an attractive alternative to current lithium-ion technologies because of the transfer of 2 electrons per magnesium-ion, higher volumetric capacity of magnesium metal compared to lithium metal (3833 mAh/cm³ Mg vs 2061 mAh/cm³ Li), and greater natural abundance. To solve the pivotal issues associated with advancing Mg as the next generation of battery technology, we require a complete understanding of the electrochemical interfaces for magnesium batteries.
To analyze the mechanism of Mg deposition and dissolution at the anode, we have combined electrochemical transport measurements with in situ electrochemical/Mg K-edge X-ray absorption spectroscopy. In situ measurements showed the presence of an additional Mg species besides the Mg dimer at potentials below Mg plating, although the [Mg₂( mu;-Cl)₃ #9679;6THF]⁺ dimer dominates the bulk transport properties of the electrolyte. From the analysis, we have devised a multi-step mechanism for magnesium deposition from this electrolyte.
Recently, we have discovered that α-MnO₂ as a viable candidate for Mg batteries because of a large initial discharge capacity of 280 mAh/g. However, a 50 % capacity fade on the second discharge requires a deep analysis to understand the mechanism during the initial reduction of the cathode. Using soft X-ray absorption spectroscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and electron energy-loss spectroscopy, we discover a vital interphase layer and propose initial discharge reactions at the cathode to explain the poor capacity retention.
Mg batteries have great potential as a post Li-ion technology. By understanding the complex electrode interfaces, we can design future electrolytes and cathodes for the next generation of Mg batteries.

Recently, rechargeable magnesium battery has been attracting attention as a candidate for a post Li-ion battery owing to a high volumetric capacity of 3832 mAh/ cm3, and the absence of dendrites formation which eliminates a major safety concern hampering the utilization of Li metal anodes. In addition, the abundance and low cost of Mg metal (10 times cheaper than Li) makes this battery very attractive for future commercialization. Nonetheless, current Mg battery technology suffer from several drawbacks which hamper its utilization. For example, in addition to the absence of robust and practical high voltage cathodes, the electrolytes typically used were found to cause severe corrosion to the current collectors. The corrosive nature of these electrolytes has been linked to the presence of halides as these electrolytes are Grignard/organohalomagnesium based. Interestingly, electrolytes based on conventional inorganic and ionic Mg salts were found to passivate the Mg anode surface therefore limiting the choice of electrolytes to the organohalo based salts and complexes. In this presentation, we will discuss our results related to a new class of electrolytes based on magnesium borohydride which represents the first example of an inorganic and relatively ionic salt reported to date that is compatible with Mg metal [1]. This electrolyte was used in the first rechargeable Mg battery utilizing an inorganic salt leading to opening a new dimension in the design space of magnesium battery electrolytes.
[1] R. Mohtadi, M. Matsui, T. S. Arthur, S.-J. Hwang, Angew. Chem. Int. Ed. 2012, 51, 9780 -9783.

Li-ion battery has played a dominant role in the rapid boost of portable electronic devices. Yet in large scale applications the requirement still remains in order to improve the energy density and power density, as well as to lower the price of the battery. For this purpose, batteries utilizing the transport of multivalent ions such as Mg2+ have gathered more and more interest recently. The theoretical capacity of metal Mg is 3833 mAhcm-3, almost as twice as that of metallic Li anode (2061 mAhcm-3). It suggests a good potential for Mg batteries to reach higher volumetric energy density. The research of recyclable Mg battery is, however, still struggling in the search of cathode material with high energy density, good rate capability and nice cyclability. To date, the only reported cathode with high cyclability is Chevrel phase. However, the low voltage and capacity of Chevrel phase limits its application as high energy density cathode.
In this talk, we discuss the challenges of the intercalation chemistry in the development of Mg battery cathode. We start with the comparison between Mg2+ and Li+ intercalation in olivine compounds. Although the thermodynamics of Mg intercalation highly mimics its Li analogue, it faces the difficulties like the strong structural deformation and the sluggish kinetic Mg transport. The latter issue has also limited the practical Mg insertion in many other compounds that show good success in Li-ion battery. On the basis of our results, instructive information is suggested for the future search of Mg battery cathode. Examples of compounds that could have fast Mg diffusion are also provided and discussed in details.

Lithium ion batteries (LIBs) are quickly becoming the mainstream power sources for environmentally friendly vehicles such as hybrid vehicles (HV), plug-in hybrid vehicles (PHV) and electric vehicles (EV) due to their high energy density. However, since a battery system with even higher energy density is required for the long-range PHV or EV applications, post lithium ion batteries (PLIB) such as Li-sulfur batteries or Li-air batteries have been getting more attention in recent years. Rechargeable magnesium batteries are also a candidate for the PLIB due to the natural abundance of magnesium and the absence of dendrite formation when magnesium metal is used as the anode. In addition, a magnesium-metal electrode is expected to have high energy density, due to its divalent nature. However, there is not much progress on the development of novel cathodes since the innovation of Chevrel phase materials such as MgMo3S4. The difficulty lies in the strong polarization character of the small and divalent Mg2+ and consequently the intercalation and diffusion of Mg2+ ions is somewhat difficult and complicated.
An alternative solution to avoid the challenges brought by the insertion of Mg2+ is to find another redox reaction on the cathode side that replaces the intercalation reaction and balances the electron transfer. Here we report a conceptual Mg battery, in which the charge transfer is achieved through the simultaneous transport of dual ions in the electrolyte during the electrochemical cycling. Reversibility on the electrodes was confirmed by multiple techniques, such as X-ray diffraction and FT-IR. Due to the avoidance of the sluggish diffusion of divalent Mg2+ which hinders the transport of Mg in the cathode materials, high rate capability has been achieved in our novel battery system (10 C over 50% capacity retention). In addition, we also showed the possibility that this conceptual Mg battery has comparable or even higher energy density than current Lithium ion batteries.

Multivalent battery systems like rechargeable magnesium (Mg) batteries are garnering more interest as candidate post-lithium (Li) battery systems, for eventual applications in electric vehicles (EVs) and plug-in hybrid vehicles (PHVs). This is primarily due to concerns over the long range performance of current Li battery systems, and the space requirements for future EVs and PHVs.^1-4 Mg, being divalent and denser, is theoretically capable of delivering a higher volumetric energy-density (3833 mAh cm^-3) than Li (2061 mAh cm^-3), making it a viable alternative battery system for addressing such concerns.^1-3 In order to be competitive with current Li-ion systems, high voltage and high capacity Mg systems must be developed. To date, various organohaloaluminates have been utilized as alternative electrolytes for Mg systems, due to the incompatibility of high voltage conventional battery electrolytes (TFSI^-, ClO₄^-, PF₆^-) with Mg metal anodes.^5-7 However, reports have shown that these organohaloaluminate electrolytes provide a limited operating voltage window when tested against typical battery current collectors.⁸
It has recently been reported that it is possible to use conventional battery electrolytes by changing the type of anode, from a Mg metal anode to a Mg-ion insertion-type anode (e.g. high energy-density Bi and Sn), enabling Mg-ion transport through the anode/electrolyte interface.^3,9 Here, we report recent advancements in the use of such insertion-type anodes for rechargeable Mg-ion batteries, using conventional battery electrolytes. Further, while the compatibility of such insertion-type anodes with conventional battery electrolytes is excellent, there remain a few issues at the various anode/electrolyte interfaces which need to be addressed. Results from recent fundamental analyses, focused on studying the various anode/electrolyte interfaces, will be discussed.
References:
1 J.-M. Tarascon and M. Armand, Nature, 2001, 414, 359.
2 P. Novak, R. Imhof and O. Haas, Electrochim. Acta, 1999, 45, 351.
3 T. S. Arthur, N. Singh and M. Matsui, Electrochem. Commun., 2012, 16, 103.
4 D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich and E. Levi, Nature, 2000, 407, 724.
5 D. Aurbach, J. Weissman, Y. Gofer and E. Levi, Chem. Rec., 2003, 3, 61.
6 Z. Lu, A. Schechter, M. Moshkovich and D. Aurbach, J. Electroanal. Chem., 1999, 466, 203.
7 T. D. Gregory, R. J. Hoffman and R. C. Winterton, J. Electrochem. Soc., 1990, 137, 775.
8 J. Muldoon, C. B. Bucur, A. G. Oliver, T. Sugimoto, M. Matsui, H. S. Kim, G. D. Allred, J. Zajicek and Y. Kotani, Energy Environ. Sci., 2012, 5, 5941.
9 N. Singh, T. S. Arthur, C. Ling, M. Matsui and F. Mizuno, Chem. Commun., 2013, 49, 149.

Sodium-ion batteries are particularly desirable for grid scale applications due to greater abundance and lower cost of sodium relative to lithium. However, promising Na-ion electrode systems are rare due to the larger ionic radius of Na and the associated difficulty of finding a suitable structural framework that can reversibly intercalate sodium ions without undergoing structural transitions. We have recently discovered a family of compounds which has large three-dimensional channels that permits facile Na-ion diffusion. High ionic conductivites of about 10-6 S / cm have been measured at room temperature on pressed pellets. These compounds have been demonstrated to reversible cycle Na ions with reasonable rates at potentials suitable for cathode applications. Intriguingly, very small volume changes (less than 1%) are observed during Na-ion removal during both in situ and ex situ studies. Both GITT data and DFT calculations indicate that Na-ion cycling occurs through a solid solution pathway without intermediate plateaus. Excellent thermal stability was observed during both thermogravimetric analyses and in situ XRD experiments, indicating that these cathodes may be useful for constructing batteries with good safety metrics. Detailed structure and electrochemical performance will be presented at the meeting.

Na-ion batteries that operate at room temperature have seen major advances in the last couple of years. In the development of materials for Na-ion batteries, the similarity between the intercalation chemistries of Na and Li is a great advantage since the knowledge and experience acquired during the development of lithium-ion batteries can be directly contrasted and compared for sodium. For example, numerous layered materials for Na-intercalation have been reported that have seen the replacement of Na for Li in their counterparts. A series of layered oxides, such as NaxCoO2, NaMnO2, NaCrO2, NaNi0.5Mn0.5O2, and NaNi1/3Mn1/3Fe1/3O2 have been extensively studied for cathodes in sodium cells. For a complete full cell, anodes such as carbon and alloying metals are used and properties of these in electrochemical reaction with Na have been described.
There also exist various transition metal sulfides that can be employed in Na batteries. The early first-row transition metal layered sulfides possess suitable electrochemical properties for Na-ion batteries since they provide soft bonding of Na to the sulfide atoms in the layers, and large gallery space between the transition metal sulfide slabs to fit Na+, which allows facile reversible electrochemical insertion/extraction.
Herein, we report the room-temperature insertion/extraction of Na from NaVS2 in order to evaluate the feasibility of the material as an electrode for Na-ion batteries. Reversible room temperature Na-(de)intercalation from NaxVS2 is achieved in the range of 0 < x < 1. The voltage curve and corresponding ex-situ X-ray diffraction analysis provided room temperature phase diagram of NaxVS2 showing phase transformation between O3-, P3-, and O1-type layered structures, as a function of sodium content x. This phase transformation accompanied by the Na-(de)intercalation was reversible with number of cycles. At low voltages, in an attempt to force a displacement-conversion reaction of NaxVS2 -> V + Na2S, we find no evidence for Na2S formation as a bulk crystalline form. Instead, the XRD shows a conversion to an amorphous phase that persists in the sample with cycling.

Na-ion intercalation chemistry for rechargeable batteries is experiencing a renewal of interest derived from controversial debates on lithium availability and cost. Within this context, the NaFePO4/FePO4 system has recently been identified as potential cathode material in Na-ion batteries. Since fundamental differences between the insertion of lithium versus insertion of sodium in the same host compound have been observed in several materials [1,2], understanding the reaction mechanisms of Na-ion electrode materials is key for the development of advanced electrode materials.
While Li insertion/extraction in FePO4 occurs through a symmetric 2-phase reaction at room temperature (with a certain Li solubility in the end members) that results in its characteristic flat voltage curve [3,4], the voltage-composition curve of NaFePO4 exhibits a clear asymmetry between charge and discharge, with a voltage drop at xasymp;0.7 visible only upon charge that has been shown to correspond to an intermediate phase [5]. In a previous work we have shown that the intermediate phase also appears upon discharge despite the voltage-composition curve is flat. Indeed, the insertion of Na into the host structure occurs via a multiphasic process involving simultaneously the two end members and the aforementioned intermediate phase (while upon extraction the three phases do not coexist) [6]. These differences have been ascribed to the balance between interface energy penalty and mismatch between the different phases involved in the reaction and highlight a very complex mechanism where strains and slow dynamics have an important role.
We will present here a more detailed analysis of the reaction mechanism of this system using a combined approach. On one side we have studied the mechanism of Na insertion/extraction by in-situ XRD, which has revealed additional unexpected phenomena. On the other side a detailed crystallographic study of the intermediate phases by coupling XRD and TEM will be shown. These results will be discussed as opposed to the variety of phenomena observed in LiFePO4 under particular conditions [7].
Referenes:
[1 ] X. H. Ma, H. L. Chen and G. Ceder, J. Electrochem. Soc., (2011), 158, A1307.
[2 ] R. Berthelot, D. Carlier and C. Delmas, Nat. Mater., (2011), 10, 74-80.
[3] A. K. Padhi, K. S. Nanjundaswamy and J. B. Goodenough, J. Electrochem. Soc. (1997), 144, 188
[4 ] A. Yamada, H. Koizumi, S. Nishimura, N. Sonoyama, R. Kanno, M. Yonemura, T. Nakamura and Y. Kobayashi, Nat. Mater. (2006), 5, 357.
[5 ] P. Moreau, D. Guyomard, J. Gaubicher and F. Boucher, Chem. Mater, (2010), 22, 4126
[6 ] M. Casas-Cabanas, V. V. Roddatis, D. Saurel, P. Kubiak, J. Carretero-Gonzalez, V. Palomares, Paula Serras and T. Rojo. J. Mat. Chem. (2012), 22, 17421
[7 ] R. Malik, A. Abdellahi and G. Ceder, J. Electrochem. Soc., (2013) 160, A3179