CC7: Metal Oxide Anodes
Chair: Terry Aselage
- Wednesday AM, December 4, 2013
- Hynes, Level 3, Ballroom C
8:00 AM - *CC7.01
Low Cost, Long Cycle Life, High Power, and Safe Battery
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.
 C.D. Wessells, R.A. Huggins, and Y. Cui, Nature Communications 2 (2011) 550
 C.D. Wessells, S.V. Peddada, R.A. Huggins,
and Y. Cui, Nano Letters 11 (2011) 5421
 C.D. Wessells, S.V. Peddada, M.T. McDowell, R.A. Huggins, and Y. Cui, J. Electrochem. Soc. 159 (2012) A98
 C.D. Wessells, M.T. McDowell, S.V. Peddada, M. Pasta, R.A. Huggins, and Y. Cui, ACS Nano 6 (2012) 1688
 M. Pasta, C.D. Wessells, R.A. Huggins and Y. Cui, Nature Communications 3 ( 2012) 2139
8:30 AM - CC7.02
Hierarchical Nanowires for Advanced Energy Storage
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.
8:45 AM - CC7.03
Carbon-Encapsulation of F-Doped Li4Ti5O12 as an Extreme High-Rate Anode Material for Reversible Li+ Storage
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.
9:00 AM - CC7.04
Graphene-Based Nanomaterials as Next Generation Lithium-ion Battery Anodes
von Hagen, Riccardo
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.
9:15 AM - CC7.05
Reduction of Titanium Dioxide Nanotube Arrays and Their Performance on Lithium Ion Battery
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 . 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 . 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.
 JR Gonzalez, R Alcantara, F Nacimiento, GF Ortiz, JL Tirado, E Zhecheva, R Stoyanova. J. Phys. Chem. C, 2012, 116: 20182-20190.
 QL Wu, JC Li, RD Deshpande, N Subramanian, SE Rankin, FQ Yang, YT Cheng. J. Phys. Chem. C, 2012, 116: 18669-18677.
9:30 AM -
10:00 AM - CC7.06
In Situ TEM Observation of the Pulverization of SnO2 Nanowires during Cycling in Na-Batteries
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.
10:15 AM - CC7.07
Two-Dimensional Early Transition Metal Carbides (MXenes) as Electrode Materials in Lithium Ion Batteries
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 Mn+1AXn; 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.
10:30 AM - CC7.08
3D in situ Imaging of Crack Formation and Volume Change in Advanced Anode Materials
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.
10:45 AM - CC7.09
Stress-Modulated Driving Force for Lithiation Reaction in Hollow Nano-Anodes
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.
11:00 AM - CC7.10
Sub-20 nm Diameter Tin Oxide Nanoparticles for High-Rate Lithium Ion Batteries
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 or additives like graphene which are not yet suitable for large-scale application.
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. 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 Li4.4Sn leads to a theoretical capacity of 781 mAh/g (based on SnO2) which is more than two times the specific capacity of graphite.
 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.
 Lian, P.; Zhu, X.; Liang, S.; Li, Z.; Yang, W.; Wang, H. Electrochim. Acta 2011, 56, 4532.
 Ba, J.; Polleux, J.; Antonietti, M.; Niederberger, M. Adv. Mater. 2005, 17, 2509.
 Courtney, I.; Dahn, J. R. J. Electrochem. Soc. 1997, 144, 2045.
11:15 AM - CC7.11
Novel Graphene Oxide/Manganese Oxide Nanocomposites and Their Potential for Lithium Ion Batteries
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.
Chair: Bridget Deveney
- Wednesday PM, December 4, 2013
- Hynes, Level 3, Ballroom C
1:30 PM - *CC8.01
Structure Evolution of Layered Composite Cathode and New Approaches to Improve Their Cycling Stability
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.
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.
2:00 PM - CC8.02
Diverse Surface Modifications of Over-Lithiated Layered Oxide Cathode Material for Lithium Ion Batteries
Choi, Yoon Sok
Kim, Seok Gwang
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)).
2:15 PM - CC8.03
Novel Family of Li-Ion Battery Cathodes with Three-Dimensional Diffusion Pathways
Van der Ven, Xiao-Qing
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.
2:30 PM - CC8.04
Investigation of Li-Rich High Energy Density Cathodes for Li-Ion Batteries
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.
2:45 PM -
3:15 PM - *CC8.05
Cable-Type Flexible Lithium Ion Battery Based on Hollow Multi-Helical Electrodes
Kim, Yo Han
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.
3:45 PM - CC8.06
Role of Mg in the Reaction Mechanism of Multi-Component Olivine Compound, LiMgy(Fe0.6Mn0.4)1-yPO4: Two-Phase vs. Single-Phase Reaction
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 LixFePO4 relaxes to form FePO4 and LiFePO4 phases upon delithiation. On the contrary, LiFe0.6Mn0.4PO4 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 LixMgy(Fe0.6Mn0.4)1-yPO4 (0 ≤ y ≤0.5, 0≤ x≤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 LixMg0.5Fe0.3Mn0.2PO4 exhibit a single-phase reaction mechanism pathway upon delithiation for the entire extractable Li range 0≤ x≤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.
4:00 PM - CC8.07
Designing Multi-Electron Phosphate Cathodes by Mixing Transition Metals
Moore, Shyue Ping
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.
4:15 PM - CC8.08
Stochastic Phase Transformation in LiFePO4 Porous Electrodes
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  and solid solution  in single composing particles.
 Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. J. Electrochem. Soc. 1997, 144, 1188-1194.
 Kang, B.; Ceder, G. Nature 2009, 458, 190-193.
 Oyama, G.; Yamada, Y.; Natsui, R.; Nishimura, S.; Yamada, A. J. Phys. Chem. C 2012, 116, 7306-7311.
 Allen, J. L.; Jow, T. R.; Wolfenstine, J. Chem. Mater. 2007, 19, 2108-2111.
 Kao, Y. H.; Tang, M.; Meethong, N.; Bai, J. M.; Carter, W. C.; Chiang, Y. M. Chem. Mater. 2010, 22, 5845-5855.
 Sharma, N.; Guo, X.; Du, G.; Guo, Z.; Wang, J.; Wang, Z.; Peterson, V. K. J. Am. Chem. Soc. 2012, 134, 7867-7873.
4:30 PM - CC8.09
Experimental and Theoretical Investigation of LiFeO2 - Tunnel as a Model System for Fe2+/Fe4+ Cathode for Li-Ion Batteries
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 Li1.57Fe1.00O2 stoichiometry without destroying the structure. Chemical Li deintercalation resulted in Li0.42Fe1.00O2 stoichiometry. Mossbauer spectroscopy was utilized to determine the Fe oxidation state in the Li intercalated and deintercalated compounds. Presence of Fe2+ and Fe3+ in Li1.57Fe1.00O2, as well as existence of Fe3+ and Fe4+ in Li0.42Fe1.00O2 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 LiFe1-xMxO2 (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 Fe3+/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.
4:45 PM - CC8.10
Electronic Structure of Cathode Material ε-VOPO4 Using Soft and Hard X-Ray Spectroscopic Techniques and Density Functional Theory Calculations
Chernova, M. Stanley
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. 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 (hν = 1486.7 eV) and hard (hν = 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.
 N. A. Chernova, M. Roppolo, A. C. Dillon and M. S. Whittingham, J. Mater. Chem., 2009, 19, 2526
 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
CC9: Poster Session III
- Wednesday PM, December 4, 2013
- Hynes, Level 1, Hall B
8:00 PM - CC9.01
The Requirements for Battery Energy Storage Applied in the Power System
Lai Xiaokang.Show Abstract
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.
8:00 PM - CC9.03
Effect of Annealing on Hydrogen Storage Properties of La1.8Ti0.2MgNi9 Alloy
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.
8:00 PM - CC9.04
Electrochemical Characterization of Noble Metal Containing Nanoalloys in Rechargeable Lithium-Air Batteries
Luo, Mei Shan
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.
8:00 PM - CC9.05
A Layered Carbon Nanotube Architecture for High Power Lithium Ion 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 0.7LiMn0.333Ni0.333Co0.333O2. When the architecture is applied to the 0.3Li2MnO3 0.7LiMn0.333Ni0.333Co0.333O2 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.
8:00 PM - CC9.06
Flexible Lithium Ion Battery Using Electrospinning Technology
Cai, Ashley SY
Choi, Kevin Ka Kan
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.
8:00 PM - CC9.07
PiezoForce and Contact Resonance Microscopy Correlated with Raman Spectroscopy of Non-linear Optical Materials and Lithium Batteries
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  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)
8:00 PM - CC9.09
Fabrication of TiO2-Graphene Composite for Enhanced Performance of Lithium Batteries
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.
8:00 PM - CC9.10
Charge Storage Mechanism of Manganese-Doped Aragonite Materials
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.
8:00 PM - CC9.12
Designing the Doped Li4Ti5O12 Anode Materials with Long Cycle Life and High-Rate by ab initio Calculations
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 (Li3.875M0.125Ti5O12) or Li32M1Ti39O96 (Li4M0.125Ti4.875O12), 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.
8:00 PM - CC9.13
Caramel Popcorn Shaped Silicon Particle with Carbon Coating as High Performance Anode Material for Li- Ion Batteries
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.
8:00 PM - CC9.14
Synthesis and Characterization of Nanosized Sn2Fe as Anode Materials for Lithium-Ion Batteries
Chernova, M. Stanley
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.
8:00 PM - CC9.15
The Impact of Lithiation Induced Stresses on Phase Transformations in Vanadium Oxide Electrodes
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.
8:00 PM - CC9.16
Computational Discovery of Small Molecules for Flow Batteries
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.
8:00 PM - CC9.17
Electrochemical Studies on Vanadate, Li2-xVO3 with Lithium-Rich Rocksalt Structure for Lithium Ion 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  and vanadate LiV3O8  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 . 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 . 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.
8:00 PM - CC9.18
Morphology, Composition and Electrochemistry: A Comparative Study of Si Anodes for Lithium-Ion Batteries
Zhou, M. Stanley
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.
8:00 PM - CC9.19
Adsorption and Diffusion of Lithium in Crystalline and Amorphous Silicon
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 . 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.
 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
8:00 PM - CC9.20
Observe Effect of Stable Sei (Solid Electrolyte Interface) Layer at Porous Structured Silicon Anode for Improving Cycling Performance in Lithium Ion Battery
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.
8:00 PM - CC9.21
Direct Growth of Single to Few Layer Graphene on Germanium Nanowire and Its Application for Lithium Ion Battery
Kim, Hee Cheul
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.
8:00 PM - CC9.22
High-Rate Capabilities A-Si Based Cu Nano-Structured Anode for Lithium Ion Batteries
Cho, Yang Doo
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.
8:00 PM - CC9.23
Carbon/Silicon/Alumina Hollow Spheres as an Anode Material for Lithium-Ion Batteries
Li, Young Hee
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.
8:00 PM -
CC9.24 Transferred to CC4.12Show Abstract
8:00 PM - CC9.25
Crumpled Graphene Balls for Scalable Energy Storage
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.
8:00 PM - CC9.26
In-Situ Nitrogenated Graphene - Few Layer WS2 Composites for Fast and Reversible Li+ Storage
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.
8:00 PM - CC9.27
Few Layer Sicn/MoS2 Composite Paper Anode for Fast and Reversible Li+ Storage
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/MoS¬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.
8:00 PM - CC9.28
Electrochemical and Structural Stability of Li3V2(PO4)3 as a Cathode for Lithium-Ion Batteries
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.
8:00 PM -
CC9.29 Transferred to CC1.05Show Abstract
8:00 PM - CC9.30
A Novel Low Temperature Approach to Recycle Lithium Ion Batteries with Mixed Cathode Materials
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.
8:00 PM - CC9.31
A Novel Hetero-Structure LiMn2O4 with Surface of Layered Phase
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.
8:00 PM - CC9.32
Microstructural Study of LiNi0.5Mn0.5O2 Synthetized by Ion Exchange
Galceran Mestres, Montserrat
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 . It is known that when the compound is made directly in Li form, a considerable amount (~10 %) of Li/Ni antisite defects are found . 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 . 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 .
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.
[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
 K. Kang, Y. S. Meng, J. Breger, C. P. Grey and G. Ceder, Science (2006), 311, 977
8:00 PM - CC9.33
Vanadium Solubility of Metal Oxide and Metal Phosphate Cathodes: Impact on Battery Resistance
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.
8:00 PM - CC9.34
The Performance and Stability of Li-ion Batteries with Ultra-Thin Solid Electrolyte
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.
8:00 PM - CC9.35
Layered Structure of Molybdenum (Oxy)Pyrophosphate as Cathode for Lithium-Ion Batteries
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.
8:00 PM - CC9.36
Low Temperature Synthesis of the Solid Li7La3Zr2O12 Electrolyte for All-Solid-State Lithium Ion Secondary Batteries
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 (>10−4 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 (~1.6×10−6 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).
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.
8:00 PM - CC9.37
Electrochemical Characteristics of Solid Polymer Electrolytes for Rechargeable Lithium Polymer Batteries
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.
 F.M.Gray, Polymer Electrolytes, The Royal Society of Chemistry, Cambridge, 1997.
 W.A.Van Schalkwijk, B.Scrosati, Eds., Advances in Lithium-Ion Batteries, Kluwer Academic/Plenum Publishers, New York, 2003.
8:00 PM - CC9.38
Systematic Characterization of Ionic Liquid Electrolyte Systems for Lithium Ion Batteries
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.
8:00 PM - CC9.39
Large Area Patternable 3D Carbon Nanotube-Graphene Structure for Flexible Li-ion Battery Anode
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) . 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 . 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 .
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 Ω/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.
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.
8:00 PM - CC9.40
Effect of Organic Solvents on Chemical Stability of Polysulfides and Cycling Performance of Li-S Cells
Kim, Jeong Yoon
Koh, Seong Soon
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.
8:00 PM - CC9.41
High Temperature Stabilization of Lithium - Sulfur Cells with Carbon Nanotube Current Collector
Kim, Jung Tae
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 . Another challenge is highly insulating properties of S, which requires the uniform introduction of electrically conductive material into the electrode . 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  and cathodes  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.
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).
 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.
 J.C. Guo, Y.H. Xu, C.S. Wang, Nano Letters, 11 (2011) 4288-4294.
 K. Evanoff, J. Khan, A.A. Balandin, A. Magasinski, W.J. Ready, T.F. Fuller, G. Yushin, Advanced Materials, 24 (2012) 533.
 S. Dorfler, M. Hagen, H. Althues, J. Tubke, S. Kaskel, M.J. Hoffmann, Chemical Communications, 48 (2012) 4097-4099.
 H. Kim, J.T. Lee and G. Yushin, JPS, 226 (2013) 256-265.
8:00 PM - CC9.42
High Capacity of Earth-Abundant FeS2 Materials for Sodium-Ion Batteries Anodes under Ultrahigh Charge Rate
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.
8:00 PM - CC9.43
A First-Principles Study on the Origin of the Low Charging Overpotential of Sodium-Oxygen Batteries
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.
8:00 PM - CC9.44
Exploring the Origins of Low Cathode Conductivity in Lithium-Air Batteries: Electron-Phonon Coupling and Polaron Formation in Li2O2
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.
8:00 PM - CC9.46
Activated Carbon/Polymer Nanocomposite Electrodes for High Performance Supercapacitors
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.
8:00 PM - CC9.47
Advanced Graphene - Transition Metal Oxide Super-Capacitor Hybridization with High Energy Battery
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.
8:00 PM - CC9.48
Electrode Platform with Densely Packed Nanoredox Centers for Green Energy Storage
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.
8:00 PM -
CC9.49 transferred to CC3.52Show Abstract
8:00 PM - CC9.50
Unraveling Structural Evolution of LiNi0.5Mn1.5O4 by In Situ Neutron Diffraction
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.
8:00 PM - CC9.51
Lithium Ion Conductivity and Mechanical Properties of PEG-PS Co-Networks
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 Mc and the domain spacing (d, from SAXS) follows DeGennes’s prediction of d ~ Mc0.5. 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 Mc 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.
8:00 PM - CC9.52
Hierarchical Porous Carbon-Sulfur Composites as Lithium-Sulfur Battery Cathodes
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.
8:00 PM - CC9.53
First Principles Study on Mn Oxide Catalysts (α-MnO2 and Mn-mullite) for Li-Air Batteries
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. 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. Recently, Cho et al. have shown that Mn-mullite (SmMn2O5) catalyst can give 45% higher performance than Pt for oxidation reactions. 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.