The use of metal fluorides and most particularly, iron fluorides, as an intercalation host electrode for Li-metal rechargeable batteries has been considered only in the late 1990&’s. [4] High band gaps of fluorides inducing low electronic conductivity as well as large voltage hysteresis have impeded their utilization in commercial cells. To overcome these limitations, Badway et al proposed the use of a carbon-metal fluoride nanocomposite prepared by high energy ball milling showing their potential use as cathode materials. [5] Furthermore, the incorporation of oxygen within the framework has been shown to lower the polarization and improved the energy efficiency and cycle life of the cell. [6]
Iron fluoride compounds can adopted several crystallographic structures including the ReO3 (rhombohedra, R-3c), the Pyrochlore (cubic, Fd-3m) or the Hexagonal-Tungsten-Bronze (denoted as HTB, orthorhombic, Cmcm) type frameworks. [7-9] The latter consists of corner-shared FeF6 octahedra forming hexagonal section along the c-axis. Structural waters are located within the tunnels and can be thermally removed without any structural collapse. [9] Surprisingly, despite the presence of such water molecules, a reversible electrochemical intercalation of lithium within FeF3.0.33H2O has been demonstrated paving the way for new researches. [10]
Depending on the synthesis method used, it has been shown that during the formation of transition metal-fluorides, a competition between M-F and M-OH bond formation might occur. [12-13] This deviation from the ideal composition is likely to impact on the physic-chemical properties of the solid. Dealing with metal fluorides and especially nano-sized metal fluorides prepared by Chimie Douce required fine structural characterizations as slight changes within the composition might strongly affect the material&’s properties.
Therein, we report a detailed investigation of the structural features of an iron-based fluoride compound having the HTB type structure where fluoride anions have been partially substituted with OH groups. The impact of the later on the structural features, thermal behavior as well as electrochemistry has been thoroughly investigated. This has allowed correlating the lithium intercalation properties with the thermal behavior of this compound emphasizing an optimal oxy-hydroxyl-fluoride composition.
[1] Arai H, Okada S, Sakurai Y, Yamaki J, J. Power Sources (1997), 68(2), 716.
[2] F. Badway, F. Cosandey, N. Pereira and G. G. Amatucci, J. Ele trochem. Soc, 150, A1318, 2003.
[3] N. Pereira, F. Badway, M. Wartelsky, S. Gunn, G. G. Amatucci. J. Electrochem. Soc., 156, A407, 2009.
[4] Leblanc, M.; Pannetier, J.; Ferey, G.; de Pape, R. Revue de Chimie Minerale (1985) 22, p107.
[5] De Pape, R.; Ferey, G. Materials Research Bulletin (1986) 21, p971.
[6] Le Blanc, M.; Ferey, G.; Chevalier, P.; Calage, Y.; de Pape, R. Journal of Solid State Chemistry (1983) 47, p53.
[7] C. Li, L. Gu, S. Tsukimoto, P. A. van Aken and J. Maier, Adv. Mater., 2010, 22, 3650.
[8] A. Demourgues, L. Francke, E. Durand, A. Tressaud, J. Fluorine Chem. 114 (2002) 229.
[9] L. Francke, E. Durand, A. Demourgues, A. Vimont, M. Daturi, A. Tressaud, J. Mater. Chem. 13 (2003) 2330.

Li₂MnSiO₄ is a promising candidate for cathode material in lithium ion batteries due to its large theoretical capacity of 330 mAhg^-1 and high thermal stability. However, its practical use has been hindered by poor rate capability and large irreversible capacity due to inherently low electronic conductivity and structural instability associated with lithiation/delithiation during cycling, respectively. In this study, we have synthesized a carbon coated Li₂MnSiO₄-graphene composite electrode to overcome these problems. Uniformly distributed graphene sheets within the electrode allow fast electron transport, which results in inproved reversible capacity and rate capability. The carbon coated Li₂MnSiO₄-graphene composite electrode exhibits discharge capacity of ~300 mAhg^-1, with a high initial coulombic efficiency of 66 %. The carbon coated Li₂MnSiO₄-graphene composite electrode delivers about two times higher capacity than that of carbon coated Li₂MnSiO₄-carbon black composite electrode.

Scanning near-field optical microscopy (SNOM) [1], nano-FTIR spectroscopy [2], and tomography [3,4] imaging using both fixed-frequency Quantum Cascade Lasers (QCL) and broadband IR laser light sources will be presented as a new diagnostic tool for studying Li-ion battery materials. By overcoming the diffraction limit normally encountered in vibrational spectroscopy and imaging (FTIR and Raman), SNOM is capable of high-resolution (~20 nm) chemical composition and structure imaging in individual particles of active materials.
Applied for the first time to energy storage material LiFePO4 [5], the SNOM technique reveals new insights in the lithiation and delithiation mechanism of micron-sized partially delithiated LixFePO4 single crystals. By resolving frequency and intensity variations of PO43- symmetric and asymmetric stretch modes associated with local changes of Fe2+/3+ oxidation state [6] during chemical (de)lithiation, this technique proves capable of providing strong imaging contrast between materials that, while structurally similar, exhibit subtle electronic differences difficult to resolve at the nano-scale using conventional analytical techniques. Infrared nano-imaging, nano-FTIR spectroscopy and tomographic analysis obtained from LixFePO4 crystals revealed a phase transformation pattern involving coexistence of distinct phases within a single particle.
These results open a new way toward the fundamental understanding of the mechanism of charge transfer, mass transport, phase transformation and propagation. We envision the SNOM technique to become established as a valuable diagnostic tool for studying new energy storage materials at the micro- and nano-scales, possibly in situ, which may be instrumental for rational design of materials and composite electrodes in electrical energy storage systems.
Acknowledgment
This work was supported by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award number DESC0001294.
[1] Keilmann, R. Hillenbrand, Phil. Trans.s R. Soc. Lond. A 362, 787 (2004)
[2] T. Taubner, R. Hillenbrand, F. Keilmann, Appl. Phys. Lett. 85, 5064 (2004)
[3] Taubner, T., Keilmann, F. & Hillenbrand, R., Opt. Express 13, 8893-8899 (2005).
[4] Zhang, L. M. et al., Physical Review B 85, 075419 (2012).
[5] Padhi, A. K., Nanjundaswamy, K. S. & Goodenough, J. B., Journal of the Electrochemical Society 144, 1188-1194 (1997)
[6] Burba, C. M. & Frech, R., Journal of the Electrochemical Society 151, A1032-A1038 (2004)

Most lithium-ion battery electrodes phase transform upon the insertion or removal of lithium. Understanding the phase transformation pathways for individual battery particles—as well as the collective behavior of many particles—is essential to improving power density and cycle life. However, experimentally measuring the phase distribution of thousands of particles at nanometer resolution is challenging with conventional microscopy and diffraction.
To investigate phase transformation across multiple length scales, we use scanning transmission X-ray microscopy (STXM) at the Advanced Light Source. We electrochemically cycle lithium iron phosphate batteries to various states-of-charge, rapidly remove the electrolyte, and cross-section the electrode. Using X-ray spectro-microscopy of the iron L absorption edge, we have successfully imaged the distribution of oxidation states at 25 nm resolution. By visualizing this distribution for thousands of particles, we observe that most particles are either fully lithiated or delithiated, and only a small fraction undergo phase transformation at any given time. In this talk, we present nanoscale microscopy results for thousands of lithium iron phosphate particles cycled at various rates. We also introduce a model describing the dynamics of many-particle phase transformation.

Recently, LiFePO₄ has received much attention as a potential of high rate cathode material for electric vehicle and hybrid electric vehicle application. However, size effects in LiFePO₄ need to be clarified in order to arrive at deeper conceptual understanding of its electrochemical behaviour.
In this work, we investigated metastable LiFePO₄ (nanocrystalline and amorphous phase) using thermodynamic considerations of the obtained experimental results (open circuit voltage measurements and potentiostatic intermittent titration tests). Apparent shrinkage of the miscibility gap and decrease of OCV values by reducing the particle size were confirmed. The effect of size as well as the impact of amorphization are strongly dependent on the storage mechanism (single phase vs. two phase model), size distribution and surface energy.
The thermodynamic effects in the LiFePO₄ are very complex and even staging phenomena are observed, which challenges the traditional two phase models. Various staging phenomena were observed for LiFePO₄ of different sizes. It appears that the staging structure is interfacial between the LiFePO₄ and FePO₄ for large particles, while large area staging exists throughout the whole sample for small sized particles. The corresponding thermodynamics and kinetics for phase transition process are discussed.

Lithium manganese orthosilicates, Li2MSiO4 have high theoretical capacity of 330mAh/g through two electron reactions of M2+/M3+/M4+. It has known that Li2FeSiO4 provides the reversible delithiation/lithiation in the range up to 1.0 Li/formula-unit but Li2MnSiO4 does not show it and has serious capacity loss upon cycling.
In our work, however, Li2MnSiO4 material with a hybrid structure of Li2MnSiO4 nanoparticles with carbon showed a stable high discharge capacity of 200mAh/g upon cycling even up to the delithiation of 1.25 Li/formula-unit. The stable cycling performance is thought to result from the fine particles of Li2MnSiO4 surrounded by carbon, which was investigated by HRTEM. The particle size is only 10-20nm, which means a short diffusion path of Li+ ions and the easy relaxation of structural distortion through the delithiation/lithiation. The presence of carbon around all the fine particles means that all the particles can make an electrical path to the cathode current collector, leading to the homogeneous delithiation.

The specific energy (Wh/kg) of the state-of-the-art lithium-ion cells today are in the range of 235-265 Wh/kg. For successful penetration of lithium-ion batteries in electric vehicles, a significant increase in cell specific energy is desired. One approach to achieve a high cell specific energy is to use advanced materials which includes (i) use of high voltage chemistries, enabled by positive electrodes which have higher equilibrium potentials, e.g. LiNi1/2Mn3/2O4 (>4.8V), xLi2Mn2O3.(1-x)LiNi1/3Mn1/3Co1/3O2 (>4.5V) etc. (ii) use of high specific capacity (mAh/g) positive or negative electrode chemistries, e.g. Silicon (>2000 mAh/g), Sulphur (>800 mAh/g). Another approach is to use existing state of the art materials, and engineer design properties at the electrode level to enhance cell specific energy. In this regard, the use of a thick and/or dense electrode will decrease the mass ratio of the inactive components relative to the active material components, thereby yielding a higher cell specific energy. However such electrodes do not achieve high energy efficiencies at normal operational conditions (charge/discharge), due to Li transport limitations in the electrodes. This talk will present the different over-potential losses leading to lower utilization (and overall energy efficiency) in such electrodes and also discuss novel electrode architectures to achieve higher energy efficiencies, thus enabling the design of high specific energy cells.

Li-ion batteries are poised to power the new generation of electric vehicles and thereby enable sustainable energy transportation. Among the most promising cathode materials, the lithium manganese spinel, LiNi_0.5Mn_1.5O₄, has received attention due to its cheap price, non-toxicity, and good rate capability compared to existing cathode materials. The Ni-Mn spinel belongs to either of two space groups, the P4₃32 (ordered) and the Fd-3m(disordered), which is determined by Ni/Mn cation arrangement. In most studies, the disordered spinel exhibits superior rate capability compared to the ordered spinel.
Recently, we developed a cluster expansion model of cationic orderings in the Ni-Mn spinel which revealed that the Li-vacancy ordering strongly prefers the Ni/Mn arrangement in the disordered configuration with resulting a voltage step at x=0.5, while the Li-vacancy ordering is not compatible with the Ni/Mn arrangement in the ordered configuration and results in no voltage steps. In this study, we performed Monte Carlo simulations based on the developed cluster expansion model and constructed a phase diagram of the Ni-Mn spinel as a function of temperature and composition. The phase diagram exhibits that the stability of solid solution region is highly improved with disorder of Ni/Mn,. We also present the ionic conductivity and electronic band structure calculations which support that both the ordered as well as the disordered Ni-Mn spinel have inherently excellent bulk ionic transport.

Li10GeP2S12 (LGPS) is a recently discovered lithium super ionic conductor. This new material has the highest conductivity ever achieved among solid lithium electrolytes of 12 mS/cm at room temperature. Our previous study have shown that LGPS is a metastable phase in the calculated phase diagram and that LGPS is not stable against reduction by lithium at low voltage or extraction of Li with decomposition at high voltage. We also identified that LGPS is a three-dimensional ion conductor rather than a one dimensional ion conductor, and our calculated overall activation barrier and conductivity are in remarkable agreement with the experimental results.[1]
In this talk, we present a first-principles analysis of the phase stability, electrochemical stability, and Li+ ionic conductivity of the Li10MP2X12 (M = Ge, Si, Sn, Al or P, and X = O, S or Se) family of superionic conductors.[2] Our results show that isovalent cation substitutions of Ge4+ have a small effect on the relevant intrinsic properties, with the hypothetical compounds Li10SiP2S12 and Li10SnP2S12 having similar phase stability, electrochemical stability and Li+ conductivity as LGPS. Aliovalent cation substitutions (M=Al or P) with compensating changes in the Li+ concentration also have a small effect on the Li+ conductivity in this structure.
Anion substitutions, however, have a much larger effect on these properties. The oxygen-substituted Li10GeP2O12 compounds are predicted not to be stable (with equilibrium decomposition energies >90 meV per atom) and have much lower Li+ conductivities than their sulfide counterparts. The selenium-substituted Li10GeP2Se12 compounds, on the other hand, show a marginal improvement in conductivity, but at the expense of reduced electrochemical stability.
We also studied the effect of lattice parameter changes on the Li+ conductivity and found the same asymmetry in behavior between increases and decreases in the lattice parameters, i.e., decreases in the lattice parameters lower the Li+ conductivity significantly, while increases in the lattice parameters increase the Li+ conductivity only marginally. Based on these results, we conclude that the size of the S2- is near optimal for Li+ conduction in this structural framework.
References:
[1] Mo, Y.; Ong, S.P.; Ceder, G. “First principles study of the Li10GeP2S12 lithium super ionic conductor material” Chemistry of Materials, 24, 15-17 (2012)
[2] Ong, SP., Mo, Y., Richards, WD., Miara, L., Lee, HS., Ceder, G., “Phase stability, electrochemical stability and ionic conductivity in the Li10±1MP2X12 family of superionic conductors” Energy and Environmental Science (in press)

Lithium ion batteries have become a widely known commodity for satisfying the world&’s mobile energy storage needs. But these needs are becoming increasingly important, especially in the transportation industry, as concern for rising oil prices and environmental impact from fossil fuels are pushing for deployment of more electric vehicles (EV) or plug in hybrid-electric vehicles (PHEV) and renewable energy sources. The objective of this research is to obtain a fundamental understanding of degradation mechanisms and rate-capacity loss in lithium-ion batteries through fracture mechanics and fatigue analysis approaches. In this study we follow empirical observations that mechanical stresses accumulate on electrode materials during the cycling process. Crack induced fracturing will then follow in the material which electrical contact surface area is degraded and over capacitance of the battery reduces. A fatigue analysis simulation is applied using ANSYS finite element software coupled with analytical models to alleviate these parameters that play the most pivotal roles in affecting the rate-capacity and cycle life of the lithium-ion battery. Our results have potential to provide new models and simulation tools for clarifying the interplay of structure mechanics and electrochemistry while offering an increased understanding of fatigue degradation mechanisms in rechargeable battery materials. These models can aid manufacturers in the optimization of battery materials to ensure longer electrochemical cycling life with high-rate capacity for improved consumer electronics, electric vehicles, and many other military or space applications.

An isothermal, physics-based model [1, 2] was used to simulate the galvanostatic discharge performance of Li_xC₆/Liquid Electrolyte/Li_y(Ni_aCo_bMn_c)O₂ dual lithium-ion insertion cell at 298 K using COMSOL multiphysics software (version 4.3). In this work, several simulation runs and associated analyses were carried out to fit the model to experimental data at different constant-current discharge rates. In these analyses, the shape of the cell voltage vs. the capacity curve was observed to vary with several parameters including the initial and the relative maximum solid lithium concentrations in the positive and negative electrodes, the initial electrolyte concentration, the solid phase lithium diffusion coefficient in the electrodes, the liquid phase lithium-ion diffusion coefficient, transference number of lithium ions, porous and tortuous nature of the electrodes and the separator, etc. Variations in kinetic rate constants were also observed to influence the cell voltage vs. capacity curve in the initial stages of discharge but do not affect the voltage knee towards the end of discharge. The importance of establishing the variable transport properties accurately [3] is shown in this work. The simulated cell performance is also significantly affected by uncertainty in the model parameters. This work demonstrates which parameters are most influential for the system and design under consideration. Systematic analyses of performance improvements with changes in each of these parameters [4] as well as the design parameters (thickness, porosity, particle size) can provide insight into methods to optimize the cell design and improve performance of these lithium-ion cells to meet advanced electric vehicle goals [5].
Acknowledgements: R. Chandrasekaran acknowledges Chul Bae, Andy Drews, Ted Miller, Dawn Bernardi, Xiao Guang Yang and Kent Snyder for their support.
References:
[1] Marc Doyle, Thomas F. Fuller, John Newman, J. Electrochem. Soc., 140, 1993, 1526-1533.
[2] Thomas F. Fuller, Marc Doyle and John Newman, J. Electrochem. Soc., 141(1), 1994, 1-10.
[3] R. Chandrasekaran, “Parameters for Electrochemical Models of Lithium-Ion Cells for Electric Vehicles”, Oral Talk, Mat. Res. Soc. Spring Meeting, San Francisco, 2012.
[4] R. Chandrasekaran, Ford Technical Report, SRR-2012-0069, June 2012.
[5]http://www.uscar.org/guest/teams/12/U-S-Advanced-Battery-Consortium

Significant advances in energy density, rate capability and safety will be required for the implementation of Li-ion batteries in plug-in electric vehicles. We have demonstrated atomic layer deposition (ALD) as a promising method to enable superior cycling performance for a vast variety of battery electrodes. The electrodes range from already demonstrated commercial technologies (cycled under extreme conditions) to new materials that could eventually lead to batteries with higher energy densities. For example, an Al2O3 ALD coating with a thickness of ~ 8 Å was able to stabilize the cycling of unexplored MoO3 nanoparticle anodes with a high volume expansion1. Recently, we coated a separator and enabled stable cycling in a high dielectric electrolyte that could better enable exploratory electrode materials2. Also, reduced thermal shrinkage was observed that could lead to improved safety for large vehicular battery packs. These results will be presented in detail.
(1) Riley, L. A.; Cavanagh, A. S.; George, S. M.; Jung, Y. S.; Yan, Y. F.; Lee, S. H.; Dillon, A. C. ChemPhysChem 2010, 11, 2124; Riley, L. A.; Lee, S. H.; Gedvilias, L.; Dillon, A. C. Journal of Power Sources 2010, 195, 588. (2) Jung Y, Cavanagh A, Gedvilas L, Widjonarko N, Scott I, Lee S, Kim G, George S, and Dillon A, Adv. Energy. Mater 2012, 2, 1022.

In this study, different weight percent&’s of 750 molecular weight purified Poly(ethylene-oxide) (PEO) were tested to determine which percent would yield a stable cycling capacity. PEO was cross-linked and uniformly coated via the free radical initiator AIBN onto the graphite surface via a two-phase synthesis. Different amounts of PEO were added to determine an optimum PEO amount to yield stable cycling. The goal of this project was to determine the amount of PEO needed to minimize the irreversible capacity related to both the molecular weight and the surface area of graphite (carbonaceous material). Slurry consisting of the PEO coated graphite mixture and other materials were applied as a laminate onto a copper foil to form the electrode. 0.3% PEO coated graphite showed the best adhesion to the copper foil and highest cycling capacity for PEO containing sample. Microscopy analysis concluded that there was no evidence of segregation or aggregation of the PEO thus indicative of uniform PEO coating on the graphite surface. We conclude that a two-phase synthesis is an effective process to modify the electrode.

The storage of hydrogen is the major technical barrier to hydrogen&’s future in the transportation market. Flexible use of hydrogen as a carrier of energy requires the means to store excess product for later use, and to transport stored hydrogen to the point of use, and to charge and discharge hydrogen conveniently from the storage container. Developing effective hydrogen storage for transportation is a central challenge for basic research and a key factor in enabling the success of the hydrogen economy. In this regard, metallic foams of amorphous alloys with open-cell structure are supposed to be a viable candidate material for hydrogen storage due to their special structural characteristics. First, the ligaments/struts in the open-cell structure experiences compressive stresses when the foams are subjected to hydrostatic pressure. Compressive stresses are always preferable since the strength of foam becomes higher than the state when tensile stresses are generated. Therefore, the foams have excellent mechanical integrity under high hydrostatic pressure. Second, the open-cell metallic structures can reduce undesired motion of stored fluids, thus increasing stability and safety of the pressure vessels.
Here, we report on the development of open cell foams of specific foaming materials by salt replication method. The process involves (i) crushing of salt particles; (ii) sintering of salt pattern; (iii) infiltration of liquid metal into the pattern; and (iv) leaching of salt pattern.

Recently, great interest has been spurred in research and development of redox flow batteries (RFBs) that are considered as one of the most promising large-scale stationary energy storage technologies [1]. RFBs&’ major advantage of separation of energy and power offers great versatility for different grid applications depending on their power rating or energy management requirements. RFBs are a suitable option to tackle the intermittency of the renewables to enable reliable integration motivated by developing clean and affordable energy for a more sustainable future. However, despite these valuable merits, broad market penetration of RFBs is hindered and the membrane component is a major limiting factor. Many RFB systems use perfluorinated membranes such as Nafion due to their high conductivity and excellent chemical stability. However, Nafion membranes suffer from low ionic selectivity and/or high cost. Therefore, searching for low-cost alternative membranes has become an active research area driven by cost reduction to RFB systems.
Our team at Pacific Northwest National Laboratory (PNNL) greatly advances this technology by inventing two new RFB systems: the all-vanadium mixed-acid system [2] and the iron-vanadium system [3]. This work reports employment of commercial or self-prepared microporous separators to the two RFB systems [4]. These separators have no ion exchange capacity but are featured with unique porous structures that function as the transport channels during RFB operations. Excellent electrochemical performance has been achieved with these separators that deliver energy efficiency comparable to Nafion and exhibit great rate capability and temperature tolerance. These separators are estimated to be at least an order of magnitude lower cost than Nafion by virtue of inexpensive raw materials and simple preparation protocol. In addition, the separators are able to offer additional operational latitude of convenient mitigation of capacity decay. Due to the good combination of critical membrane requirements, these separators have demonstrated to be suitable membrane substitutes to Nafion and show great potential to promote market penetration of the two RFB systems by enabling significant reduction of their capital and cycle costs.
Reference:
[1] W. Wang, Q. Luo, B. Li, X. Wei, L. Li, Z. Yang, Adv Funct Mater, (2012).
[2] L.Y. Li, S. Kim, W. Wang, M. Vijayakumar, Z.M. Nie, B.W. Chen, J.L. Zhang, G.G. Xia, J.Z. Hu, G. Graff, J. Liu, Z.G. Yang, Adv Energy Mater, 1 (2011) 394-400.
[3] W. Wang, Z.M. Nie, B.W. Chen, F. Chen, Q.T. Luo, X.L. Wei, G.G. Xia, M. Skyllas-Kazacos, L.Y. Li, Z.G. Yang, Adv Energy Mater, 2 (2012) 487-493.
[4] X. Wei, L. Li, Q. Luo, Z. Nie, B. Li, G.-G. Xia, E. Miller, J. Chambers, W. Wang, Z. Yang, J Power Sources, 218 (2012) 39-45.

Layered composite cathode materials are getting worldwide attention because of their ability to provide high discharge capacity and good cyclability. Recently, we performed theoretical and experimental studies on a series of layered cathode materials and demonstrated LiNi_0.66Co_0.17Mn_0.17O₂ as a promising cathode material for Li-ion batteries. A discharge capacity of ca. 200 mAh/g was achieved at a current density of 5 mA/g in the potential region of 2.0-4.6 V. To increase the discharge capacity and rate capability further, we prepared a composite of LiNi_0.66Co_0.17Mn_0.17O₂ with Li₂MnO₃ using wet chemical routes and investigated cell performance. The prepared composite material was characterized using powder X-ray diffraction, Raman spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The powder X-ray diffraction patterns confirm good crystallinity of the as-prepared samples and also showed clear splitting of the peaks corresponding to (006)/(102) and (108)/(110) planes. The peaks observed in the 2theta; (deg.) range of ca. 21-30 revealed the presence of short range ordering corresponding to monoclinic Li₂MnO₃ with C2/m space group. Raman spectroscopy measurements indicate two different types of ionic arrangements corresponding to space groups of R3m and C2/m for LiNi_0.66Co_0.17Mn_0.17O₂ and Li₂MnO₃ respectively. SEM images depict the spherical agglomerated particles of ca. 5 µm with sharp and elongated edges. EDX analysis confirms the presence of respective elements with exact composition. Finally, working electrodes are fabricated by mixing active material, carbon black, and PVDF using NMP as a solvent and then spread it on the Al foil. CR 2032 coin cells were assembled inside the Ar-filled glove box using Li-metal foil as counter electrode and 1 M LiPF₆ in EC-DMC as electrolyte. Electrochemical studies were carried out using cyclic voltammetry and galvanostatic charge-discharge systems. Cyclic voltammograms show the well-defined redox peaks corresponding to Ni²⁺/Ni⁴⁺. Charge-discharge tests performed at different C-rates indicate better electrochemical performance of the composite in terms of high discharge capacity, good rate capability, and good cyclability.

Although uranium oxides have played essential roles in many nuclear reactions, it is imperative to pursue alternative solutions to reuse the spent fuels due to paramount safety and economic concern. Spent nuclear oxide fuels include uranium dioxide (UO2), triuranium octoxide (U3O8) and uranium trioxide (UO3). In this work, first principles calculations based on density functional theory (DFT) are carried on for MUO2, MU3O8 and MUO3 (M= Li, Na, K, Mg, Ca and Al) to explore their possibilities to serve as grid-storage-based cathode materials. In particular, the result of the optimal structures, average open circuit voltages (OCV) and mechanic stabilities during charge and discharge processes will be presented. These results will be compared to available experimental data.

We present the results from two different neutron scattering techniques on superionic materials that are good candidates for use as solid state electrolytes in next generation Li+ ion batteries. Lithium ion conducting glasses of the compositions xLi2SO4-(100-x) [0.5Li2O-0.5P2O5] ; x = 1-10 were synthesized by conventional melt-quenching. The mixture of the suitable composition, containing high-purity Li2CO3, NH4H2PO4, and Li2SO4 materials, was initially kept at 450 0C for 2 hours (to remove NH3, CO2 and H2O), followed by melting at 900-950C for ~ 30 min and rapid quenching between the copper plates. Transparent homogeneous glassy flakes were thus obtained and used for the characterization.
The materials are glassy in nature and composed of a complex network of the following sub-units: Li2O, Li2SO4, and 2NH4H2PO2. This disordered structure is integral to its function in that it promotes Li+ ion conduction while suppressing electron conduction, the necessary qualities of a good Li+ electrolyte. We used neutron diffraction to study the formation of crystallites upon heating of the material above 400C. The crystallite formation is understood to be detrimental to the Li+ ion mobility and, hence, is identified with a diminished performance in devices that require heating in their fabrication process. We have also used a triple-axis spectrometer to begin to separate out the diffuse scattering that results from the disordered structure of the material from the diffuse scattering that results from dynamic processes that occur in it. This is done by a comparative study of the energy resolved versus energy integrated scattering over the full available q-range.

Li-stuffed garnet oxides have attractive ionic conductivities[1] for lithium ion battery applications. Most of previous structural studies[2, 3] only focused on average structure and provided little insight in the local disorder of lithium ions. In our study, powder neutron diffractions were performed on four different compositions in the series Li7-xLa3Zr2-xO12 (x=0, 0.3, 1, 2). The average structures were obtained with the Rietveld refinement. 5000 random structures based on average structures were generated for each composition for the 1x1x1 supercell. These structures were optimized by the atomistic simulation code (General Utility Lattice Program, GULP)[4] and distribution of energies was obtained for each composition.
For Li7La3Zr2O12 with the tetragonal symmetry, the most probable structure is almost the same as the average ordered structure from neutron diffraction of this work and Awaka&’s work[5], proving the validity of this method. For other compositions with the cubic symmetry, a Gussian distribution was obtained with distribution width decreasing with the increasing size of supercells. By analyzing the local features of these cubic structures, we gain new insights in the local disorder of lithium ions. The tetrahedral lithium sites are displaced from the ideal center contrary to what was previously proposed. Simultaneous occupation of adjacent tetrahedral-octahedral-tetrahedral sites was observed in contrast with O&’Callaghan&’s assumption[6]. The occupancies of tetrahedral lithium sites decreased while the occupancies of octahedral lithium sites increased with the increasing lithium content in the composition series largely following the trend as determined from neutron diffraction. A simple mean-field transport mechanism involving both tetrahedral and octahedral lithium sites was proposed to explain the dependence of conductivity on Li content.
[1] Y.X. Wang, W. Lai, Electrochem Solid St, 15 (2012) A68-A71.
[2] E.J. Cussen, Chem Commun, (2006) 412-413.
[3] J.B. Goodenough, H. Xie, J.A. Alonso, Y.T. Li, M.T. Fernandez-Diaz, Chem Mater, 23 (2011) 3587-3589.
[4] J.D. Gale, A.L. Rohl, Mol Simulat, 29 (2003) 291-341.
[5] J. Awaka, N. Kijima, H. Hayakawa, J. Akimoto, J Solid State Chem, 182 (2009) 2046-2052.
[6] M.P. O'Callaghan, E.J. Cussen, Chem Commun, (2007) 2048-2050.

Mechanically and thermally robust polymer dielectrics are needed to increase the operating temperature range up to 300 °C, and mitigate thermal management issues in compact pulsed power applications. Arguably an important class of high temperature polymers with versatility in properties and processing, polyimides (PIs) would be one of the most promising candidates for such applications. They have found utility in high performance films, coatings, microelectronics, optoelectronics, adhesives, aerospace structures, and liquid crystal displays. Polyimides containing benzonitrile units have been studied for the piezoelectric and other dielectric applications due to the high polarity of nitrile groups. In our previous research, one unsymmetric and two symmetric diamines as well as the respective polyimides containing one benzonitriles in each repeat unit were synthesized. We found that the presence of unsymmetrical structure in the repeat units improved the processing of poly(amic acids) (PAAs) into PI films with increased dielectric constants and little or no adverse effect on the dielectric loss. As a continuing effort to probe the structural factors to balance the need for high dielectric constant, low dielectric loss, and thermal stability in high temperature capacitors, polyimides containing three benzonitrile groups in each repeat unit were synthesized. Thus, diamines containing three benzonitriles were synthesized via a 3-step route. They were polymerized with four commercial dianhydrides in DMAc to afford poly(amic acid), which were thermally cured up to 300 °C to form tough, creasable films. Most of these polyimides are soluble in common solvents. Their glass transition temperatures range from 216 to 305 °C. The polyimides are stable up to 400 °C. The dielectric constants of these polyimides increased from 2.9 (CP2) to 4.3 (6FDA-based polyimide) at 10 Hz.

The development of high-capacity batteries is in great demand for technological applications, such as portable electronic devices and electric vehicles. Current lithium-ion (Li-ion) batteries use graphite as the anode material with a maximum capacity of 372 mAh/g. Novel anode materials with higher gravimetric capacities and enhanced charge/discharge capabilities are required for the next generation of batteries. Layered pnictide compounds are promising new anode materials. We report the synthesis, structural and electrochemical characterization of Sn₄As₃ and Li_0.7Sn_2.3As₂. The crystal structure of Sn₄As₃ consists of alternating layers of tin and arsenic atoms that are combined into seven-layer blocks that build up along the c-axis. Within each block, there is one layer of atoms of each type such that the layer of tin atoms separates the layers of arsenic atoms. The crystal structure of Li_0.7Sn_2.3As₂ can be described as a derivative of a hypothetical binary tin arsenide, Sn₃As₂. The latter compound has a crystal structure similar to Sn₄As₃ with a reduced thickness in the Sn-As blocks, which are 7 atoms thick in the case of Sn₄As₃ and 5 atoms thick in the case of Sn₃As₂. In the crystal structure of Li_0.7Sn_2.3As₂, lithium atoms substitute 70% of the tin atoms in the middle of the Sn₃As₂ block. Thus, lithium is able to partially cut the Sn-As layers apart. We hypothesize that formation of Li_0.7Sn_2.3As₂ is the first stage of Li intercalation into Sn₄As₃. Electrochemical properties and homogeneity range of Li_0.7Sn_2.3As₂ and Sn₄As₃ will be discussed.

Low alkali boroaluminosilicate glass dielectrics explored in this study have high dielectric breakdown strength (12 MV/cm), high energy densities (38 J/cm3, have the potential to operate above 200C and the volume is much smaller than that of commercial high temperature capacitors which makes them the material of choice for high temperature capacitor applications for hybrid electric vehicles. Due to the low alkali content (100-400 ppm) it was possible to study transport properties of alkaline earth ions in these boroaluminosilicate glasses. Activation energy (Ea) for transport of alkaline earth (Ba, Ca) and alkali ion (Na) causing ionic conduction in these glasses has been estimated using high field (14 MV/m) thermally stimulated depolarization current (TSDC) and low frequency (106-10-2 Hz) AC impedance spectroscopy techniques. Temperature dependent AC conductivity plot also showed distinct slopes supporting conduction due to ionic species with different Ea. Bucci Fieschi model was used to obtain Ea of 1.83 eV for Ba and 0.9 eV for Na from TSDC measurements. Arrhenius shift in the temperature dependent AC conductivity plot also provided Ea values for Ba and Na similar to those obtained from TSDC measurements. Increase in activation energy of alkaline earth ion was also observed in presence of other alkaline earth ions suggesting evidence of mixed alkaline earth ion effects. High field (109 V/m ) IV and TSDC measurements confirmed electron injection due to Pool Frenkel emission in the cation depleted layer in the glass beneath the anode. Non-linear optical measurement was used to measure the depletion layer thickness, which was found to depend on poling field, time and temperature. It is concluded that electron injection in the depletion layer initiates the dielectric breakdown in this glass. It is also proposed that a polymeric coating on these glasses can improve its performance as high energy dielectrics.

Lithium orthosilicate have become appealing as a cathode material of lithium ion batteries due to their overwhelming advantages, such as high theoretical capacity, high thermal stability through strong Si-O bonding, safety, cost effectiveness, as well as being eco-friendly and easy to synthesize. Among the silicate groups, Li2MnSiO4 is more attractive than other counterparts because of its dominant characteristics. Lithium manganese silicate could theoretically insert/extract two lithium per formula unit with a theoretical capacity of 330 mAh/g which is almost twice of the theoretical capacity of LiFePO4 (170mAh/g). Furthermore, Li2MnSiO4 provides a higher cell voltage (5V) than the LiFePO4 (3.4V) due to the possible oxidation of the Mn3+/Mn4+ couple rather than Fe2+/Fe3+. The main challenge for Li2MnSiO4 as a cathode material is its poor conductivity which needs to been overcome by adopting some strategies including doping, decreasing the particle size through various synthesis methods, and coating with electronically conducting agents. This paper reports our efforts in the modification of the material through supercritical fluid synthesizing routes and surface treatment. The rapid expansion of a supercritical ethanol fluid routes are used to synthesize the desired size and morphology pure Li2MnSiO4 nanocrystals under different conditions of high pressure and low temperature. Moreover, the pure Li2MnSiO4 nanoparticles were coated by the conductive material of PEDOT to increase the electrical conductivity. This cathode material was investigated by spectroscopy, microscopy and electrochemical techniques to characterize their composition and performance. The electrochemical cycling stability and high discharge capacity are presented in the paper.

Sulfur is an attractive cathode material with a high specific capacity of 1,673 mAh/g, but its rapid capacity decay due to polysulfide dissolution presents a significant technical challenge. Although much effort has been devoted to encapsulating sulfur particles with conducting materials to limit polysulfide dissolution, relatively little emphasis has been placed on dealing with the large volumetric expansion of the sulfur core during lithiation (~80%), which will lead to cracking and fracture of the protective shell. Here, we demonstrate the design of a sulfur@TiO2 yolk-shell nanoarchitecture with internal void space for stable and prolonged cycling over 1,000 charge/discharge cycles in lithium-sulfur batteries. Compared to bare sulfur and sulfur@TiO2 core-shell nanoparticles, the yolk-shell nanostructures were found to exhibit the highest capacity retention due to the presence of sufficient empty space to accommodate the volume expansion of sulfur, resulting in a structurally-intact TiO2 shell to minimize polysulfide dissolution. Using the yolk-shell nanoarchitecture, an initial specific capacity of 1,030 mAh/g at 0.5C and Coulombic efficiency of 98.4% over 1,000 cycles was achieved. Most importantly, the capacity decay after 1,000 cycles was found to be as small as 0.033% per cycle, which represents the best performance for long-cycle lithium-sulfur batteries so far.

Olivine structured LiMPO4 (M = Fe, Mn) cathodes of Li-ion batteries are considered as the most promising candidates for applications in future electric vehicles and large scale energy storage, due to the moderate theoretical capacity (~170 mAhg-1), structural reversibility, thermal stability, environmental friendliness, and an increased level of safety. In order to increase the conductivity and improve the electrochemical performance of LiMPO4, tremendous efforts have been made, such as reducing the particle size, improving the crystallinity of the nanoparticles, the doping, coating the nanoparticles and/or forming composites with the inorganic and organic conductive materials.
In this work, various morphologies of LiMnPO4 and LiFePO4 nanoparticles with high crystallinity, such as nano-rods, nano-plates, and nano-sheets, are prepared by a hydrothermal method. Among various synthetic routes for LiMPO4, the hydrothermal approach is advantageous to prepare nanoparticles with high crystallinity under relatively low temperature because of the high pressure developed during the synthetic process. Desired morphology with high surface area of olivine LiMnPO4 and LiFePO4 nanoparticles were prepared by a hydrothermal method with adding various surfactants to the starting materials of LiOH, Mn(CH3COO)2.4H2O, FeSO4.7H2O, and H3PO4. In addition, conductive materials were coated on the surfaces of the pristine LiMnPO4 and LiFePO4 nanoparticles, to improve the cathode performance. Complete and homogeneous conductive coating with carbon or conductive polymers resulted from pyrolyzing the organic compound under an inert atmosphere. The structure, morphology, carbon coating amount and electrochemical properties were analyzed using a X-ray powder diffractometer (Rigaku, DMAX-2200PC), electron microscopes (JEOL, JSEM-6700F, JSEM-6380), a thermal gravimetric analyzer (Netzsch STA 409 PC/PG), an electrochemical impedance analyzer (Schlumberger SI1260), and a battery cycler (Maccor S4000). We report that the nanocryatalline olivine cathode materials with desired morphology and size are synthesized and that LiMPO4 nanoparticles well-coated with conductive materials can achieve the theoretical limits of high capacity.

Among anode materials, Germanium (Ge) is one of the most promising alternatives to conventional carbonaceous active materials, since it is capable of alloying with more lithium, thus leading to an extremely high theoretical capacity. However, the utilization of Ge is a non-trivial issue. It has been reported that lithiation and delithiation of such electrode materials in LIBs result in large strains in the host material, leading to capacity fade and poor cycle life. In addition, lithiation is also often accompanied by structural transformations, such as electrochemically driven solid-state amorphization (ESA). Moreover, mechanical stresses induced by the volume changes (over 300%) during cycling result in pulverization and delamination of the electrode structure, leading to capacity fading and poor cycling life.
Recent work [1-3] has demonstrated that 3D metal foams, based on copper, nickel, stainless steel Au leading to bicontinuous as current collectors not only allow forfast transport of lithium ions through electrolyte and electrode, but also for rapid electrochemical reactions. In this work, we describe a 3D bicontinuous Au/a-Ge thin film electrode fabricated by thermal evaporation. The nanoporous Au acts as a volume buffer cushion. It also provides good electronic/ionic conductivities enhancing the rate capability of the Au-Ge anode for LIBs.
To compare the thickness effect on the electrochemical performance, two samples with thickness of 20 nm and 50 nm were prepared, respectively. The Au-Ge- 20 nm electrode displays a better electrochemical performance. It delivers a very high reversible capacity of 1066 mAh/g even after 100 cycles at 0.2 C. At a rate of 60 C, it still delivers a capacity of 360 mAh/g.
Reference:
[1] H. C. Shin, J. Dong, M. Liu, Adv. Funct. Mater. 2005, 15, 582.
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[3] H. Zhang, X. Yu, P. V. Braun, Nat. Nanotechnol. 2011,6 ,277.

Oxides nanoparticules present high surface charges that can be amplified by their high specific area to yield a large electrochemical capacity upon adsorption of ions in their double layer. Unlike carbon-based electrochemical capacitors, transition metal oxides with mixed valence properties exhibit redox (faradic) reactions that largely amplify the capacitive effect which is called pseudocapacity [1]. This effect can be further increased in the case of open-structure materials which present a good ionic conductivity and fast ionic intercalation and exchange properties. However, formulation of electrodes reaching the lowest electrical and ionic resistivity has to be found prior to performance measurements. Thus a step by step study of both electronic and ionic transport has been set up.
First of all, a low temperature synthesis of cobalt bronzes was developed. Indeed, the NaxCoO2 phase can be electronically conductive [2,3], and therefore is a good candidate for supercapacitor applications. Nanoparticles of NaxCoO2 with size ranging between 30 and 80 nm and high specific area (above 100 m2/g) can be synthesized by rapid precipitation in an aqueous alkaline oxidizing medium at room temperature [4].
Then, the intrinsic conductivity of the material has been investigated by Broadband Dielectric Spectroscopy showing that NaxCoO2 has a metallic behavior at high frequency. Furthermore both electronic and ionic conductivity of mixtures of nanometric NaxCoO2 and carbon have been studied as a function of the powder packing and carbon addition by Electrochemical Impedance Spectroscopy.
Taking into account the conclusions of these first studies about the intrinsic properties of both NaxCoO2 and mixtures of the material and carbon, different formulations of thick electrodes have been investigated. Moreover the addition of a binder and a porogen has also been studied. It appears that the best capacities are reached with direct casting of a slurry (active material, carbon, binder and porogen) onto an aluminum foil which is further pressed and heated.
The optimized electrode formulation has been transferred to conductive vanadium bronzes xerogels [5]. The LixV2O5 bronze shows a high charge of 500 C/g at low sweep rate in organic electrolyte. And even at very high sweep rates, the charge remains above 125 C/g showing the good electronic and ionic conductivities of these systems. This formulation may be extended to other transition metal bronzes.
[1] B.E. Conway, Journal of Electroanalytical Chemistry 524-525 (2002) 4-19
[2] F. Tronel, L. Guerlou-Demourgues, M. Basterreix, C. Delmas, Journal of Power Sources 158 (2006) 722
[3] M. Pollet, M. Blangero, J.-P. Dourmec, R. Decourt, D. Carlier, C. Denage, C. Delmas, Inorganic Chemistry 48, (2009) 9671
[4] X. Pétrissans, A. Bétard, D. Giaume, P. Barboux, B. Dunn, L. Sicard, J.-Y. Piquemal, Electrochimica Acta 66 (2012) 306-312
[5] I.D. Raistrick, R.A. Huggins, Solid State Ionics 9-10 (1983) 425-430

It is known that finite fossil-fuel supplies, global warming and environmental pollution conspire to make the use of renewable energies a worldwide imperative. Due to the intermittence of the renewable energies (such as wind, wave and solar) outputs, better energy storage and assistance systems must be developed to ensure a continuity of supply. Among various storage technologies, Li-ion batteries not only have been demonstrated as the prime candidate to power the next generation of electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), but also offer promising opportunities for grid-scale energy storage applications. In 1997, olivine structured LiFePO4 was first demonstrated as a viable cathode material. Since then, the exceptional safety and rate capabilities of LiFePO4 have promoted a strong research interest focusing upon polyanionic phosphate systems.
Among them, vanadyl phosphate compounds (VOPO4) are especially attractive because of their higher free energy of reaction than the correspondent iron compounds, as well as the greater possibility to tune the redox potential. Up to now, a total of seven types of crystal structures that differ in the connection and arrangement of VO6 octahedral and PO4 tetrahedral units have been reported: alpha I-, alpha II-, beta-, gamma-, delta-, epsilon- and omega-VOPO4. In Li-ion battery research, delta- and especially epsilon-VOPO4, the most recently discovered polymorph, show promising electrochemical properties. For example, epsilon-VOPO4 adopts a stable 3D tunneling structure with the theoretical specific capacity of ~168mAh/g, as high as LiFePO4. Compared with LiFePO4, epsilon-VOPO4, has a higher conductivity and charge/discharge plateau (around 4.0 V), and more importantly, would accommodate two lithium ions per redox center, which will greatly benefit its utilization as high energy density batteries.
To uncover structure-property relationships within VOPO4-based battery materials, we carried out a comprehensive structure analysis for VOPO4 family compounds, and developed a structure evolution-based interpretation of intercalation mechanism for the respective VOPO4 phases. This interpretation is further verified by a variety of experiments as well as theoretical calculations. The results obtained can be used to distinguish the key factors that determine the electrochemical performance, define the appropriate working voltage window, and to maximize the energy and power density of VOPO4 based battery materials. This study will benefit the battery community to address both fundamental and practical issues of polyanionic phosphate materials, which would be promisingly utilized as next generation of advanced Li-ion batteries. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Basic Energy Sciences under Award Number DE-SC0001294.

High-performance Lithium-ion batteries are crucial in the storage of clean energy from solar and wind, as well as in the development of electric/hybrid vehicles and portable electrical devices. However, graphite, as the commercial anode material, is suffering from low Li storage capacity (~ 372 mAh/g in theory) and slow charge/discharge rate. In comparison, metal oxides can store ~ 3 times more Li through conversion reactions than graphite through intercalation process, thus, are promising anode candidates for the next generation of Lithium-ion batteries. Among various metal oxides, Fe2O3 is outstanding due to its high theoretical spectificcapacity (1005 mAh/g), richness in earth (5.63%), lowness in cost, and no harm to the environment. As a common problem of metal oxides, Fe2O3 suffers from poor electrical conductivity and pulverization during lithiation. Strategies such as reducing particle size to nanoscale, forming porous structure and mixing with conductive additives have been proposed. Here we report a unique 3D hydrid structure of Fe2O3/graphene-assembly as high-performance anode material synthesized through sol-gel method, during which the load of Fe2O3 is readily adjustable. The composites have achieved an impressive specific capacity of up to ~1200 mAh/g after 30 charge/discharge cycles. The possible mechanisms of such excellent electrochemical performance will be discussed.

Research on rechargeable lithium ion batteries has its 40th anniversary this year. The first batteries used LiAl anodes and TiS2 cathodes (and are still operational 40 years later), and the first highly commercially successful cells used LiC6 and LiCoO2 electrodes. These latter cells are now 20 years old, and their energy storage capability has significantly improved over the years. However, they still attain only around 20% of the theoretical energy density, either on a weight or volume basis [IEEE Proceedings, 100, 1518, 2012]. This is in part a result of the very low volumetric capacity of the carbon anode, but also the inability to use much more than 60% of the lithium capacity in the layered oxides at practical rates. A fundamental understanding of the electrode reactions is essential, and will lead to higher rates and capacities; higher rates will allow the use of thicker electrodes and therefore less current collectors and separators. The olivine materials and layered oxides will be used as examples where our understanding is improving. The former represent a class of material, which despite being electronic insulators, can sustain high rates and high capacity retention. This can be related to a pseudo-single phase reaction mechanism, which is enhanced by substitution on the iron site. The latter are challenged by the high mobility of the transition metal ions at room temperature, which allows the metal distribution to change on cycling often in an irreversible manner. This work is supported by the US Department of Energy, Office of Science, through the EFRC program, NECCES at Stony Brook.

High energy density cathode materials are key in the development of advanced lithium ion batteries that can be employed for transportation electrification. Batteries operating in high voltage conditions, however, involve complicated parasitic reactions in addition to the desired electrochemical processes. In this work, various factors which affect the stability of high voltage spinel LiNi0.5Mn1.5O4 will be reported. A facile synthesis approach for high voltage spinel has been developed. Synthesis conditions including calcination temperature, post-synthesis heating, cooling rate and elemental substitution were systematically investigated to prepare high performance LiNi0.5Mn1.5O4. The content of the disordered phase (which can be tuned through oxygen deficiency and/or element substitution) was found to be one of the most critical parameters affecting the performance of LiNi0.5Mn1.5O4. The cooling rate of spinel after high temperature calcination, often ignored during synthesis, in fact significantly changes the amount of oxygen deficiency, which then modulates the residual Mn3+ and amount of disordered phase. This observation was consistent with our earlier finding on the effect of post-synthesis heating and Cr-doping, both of which also modified the relative proportion of disordered and ordered phases.
In high voltage conditions, all the “inactive” cell components, such as cell electrolytes, cans, separator, and even carbon additives used in the electrode (which are normally stable at < 4.4V in conventional Li-ion batteries) need to be reinvestigated. For lab tests using button cells, aluminium (Al)-clad SS-316 positive cans had a much better resistance to oxidation than traditional stainless steel (SS-316) cathode pans at high voltages. It was also found that a polyethylene (PE) based separator, such as Celgard K1640, is very stable at high voltage while a polypropylene (PP)-based separator (Celgard 2500) is not stable. Furthermore, it is found that carbon additives in the cathode also may induce side reactions at high voltages. Therefore, careful selection of carbon additives for high voltage operation is required.
Acknowledgement
This work was sponsored by PNNL Laboratory Directed Research and Development (LDRD) Project and the Office of Vehicle Technologies of the U.S. Department of Energy.

The high voltage LiNi0.5Mn1.5O4 spinel is being considered as a promising positive electrode material in lithium-ion batteries due to its combination of high performance, potential low cost, and environmental friendliness. Its wide-spread use is partly hindered by an issue of manganese dissolution into the electrolyte that leads to a significant capacity fade in cells using graphite as the negative electrode. In this talk, the manganese dissolution behavior of the LiNi0.5Mn1.5O4 positive electrode material and several strategies to overcome its detrimental effect on the full-cell performance will be presented.
Firstly, the manganese dissolution behavior of the LiNi0.5Mn1.5O4 spinel under various conditions such as temperature, storage time, and state of charge, will be discussed. The amount of the manganese dissolution determined by using X-ray fluorescence (XRF) spectrometer or inductively coupled plasma (ICP) spectroscopy, will be presented. Secondly, the effects of several strategies to modify the SEI to improve full-cell performance, which involves either surface coatings of the electrodes or the use of electrolyte additives, will be highlighted. The impact of altered interphase will be correlated with the amount of manganese dissolution and with the cycle- and calendar-lives of the full-cells. Finally, systematic analytical data will be presented to elucidate how such SEI modification improves electrochemical performance. High resolution transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectrometry (TOF-SIMS) will reveal the properties of the SEI layer on either positive or negative electrodes after 100 cycles. These analytical data will be combined with extensive electrochemical analysis to identify the most efficient approaches to overcome the manganese dissolution problems in the LiNi0.5Mn1.5O4 systems.

Spinel structured oxides, such as LiNi1/2Mn3/2O4 have attracted significant interst as the positive electrode materials for rechargeable lithium ion batteries because the potential where lithium is removed from the host structure is very high (~4.7V vs Li+/Li0).1-3 One of the barriers to commercialization of LiNi1/2Mn3/2O4 is precisely due to the high voltage of operation, which is outside the window of stability of the electrolyte solutions used in current Li-ion batteries. As a result, spurious reactions occur during cycling that lead to the electrolyte decomposition on the surface of the electrode that compromise the life of the whole device. This undesirable process is aggravated at small particle sizes because of the increase in surface area.4,5
To mitigate unfavorable side reactions with the electrolyte solutions, surface coating of the electrodes proved an effective ways to improving the performance of Li-ion batteries. 6,7 Among various techniques, atomic layer deposition (ALD) has been used to significantly enhance both the durability and safety of positive/negative electrodes (e.g. LiCoO2 and graphite) of Li-ion batteries by ultrathin coating of Al2O3.8 Although coating of electrochemically inactive metal oxide materials such as Al2O3 showed high energy and rate performances, the performances of the coated electrodes degrades as the thickness of inactive layers increases. In addition, the detailed mechanisms of lithium ion conduction paths were not clearly explained yet.
To this ends, we prepared LiNi1/2Mn3/2O4 electrodes with both electrochemically inactive and active coatings by employing ALD. Ultrathin lithium ion conductor, LiAlOx layers were coated on composite electrode (Active material: PVDF: Carbon = 80:10:10) with three different thicknesses (2cycles, 5cycles and 10cycles). For comparison, Al2O3 layers were coated on the same electrodes. In order to systematically explore the effect of coating materials and the thickness on the electrochemical properties, the resulting samples were tested in Li half cells using constant current and rate capability experiments.
References
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[2] Zhong, Q. M.; Bonakdarpour, A.; Zhang, M. J.;Gao, Y.; Dahn, J. R. J. Electrochem. Soc.1997, 144, 205- 213
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[4] Talyosef, Y.; Markovsky, B.; Lavi, R.; Salitra, G.; Aurbach, D.; Kovacheva, D.; Gorova, M.; Zhecheva, E.; Stoyanova, R. J. Electrochem. Soc. 2007, 154, A682- A691
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[8] Jung, Y. S.; Cavanagh, A. S.; Riley, L. A.; Kang, S. minus;H.; Dillon, A. C.; Groner, M. D.; George,S. M.; Lee, S. H. Adv. Mater. 2010, 22, 2172

High-voltage spinel cathodes LiMn1.5Ni0.5O4 are promising candidates for large-scale applications such as electric vehicles. However, the adoption of these cathodes has been hampered by capacity fade, particularly at elevated temperatures, due to factors such as Mn dissolution, aggressive formation of a thick solid-electrolyte interphase (SEI) layer, cationic ordering between Mn4+ and Ni2+ ions in the crystal lattice, and formation of a rocksalt LixNi1-xO impurity phase. Additionally, this material has been found to vary widely in physical and electrochemical properties depending on the synthesis method, but it has remained unclear whether the wet-chemistry preparation and crystal planes exposed to the electrolyte affect the electrochemical performance. We present here an investigation of how the synthesis conditions of the co-precipitation method influence the microstructure and morphology, and examine the impact of these factors on the electrochemical performance. The samples were prepared by two similar wet-chemical routes and were characterized by microscopy and electrochemical cycling. To ensure a thorough comparison with competing explanations in the literature, other factors including the degree of cation ordering, Mn3+ content, the changes in lattice parameter with state of charge, and Ni/Mn ratio were considered, but these parameters did not influence the electrochemical performance as strongly. It was found that the surface crystal planes, the arrangement of lithium ions near the surface, and the lithium diffusion mechanisms have a considerable effect on the capacity retention and rate capability. For example, octahedral crystals with {111} family of surface planes exhibit superior cyclability and rate capability compared to truncated octahedral crystals with {100} surface planes. Design and development of synthesis approaches that stabilize the optimum surface planes is the key to achieve consistent properties and high performance with the high-voltage spinel cathodes.

There is an ongoing fundamental debate related to the structure of certain Li- and Mn-rich oxides used in lithium batteries, which is reflected in the literature as two different notations. One group of scientists believes that these materials are solid solutions be-tween LiNi0.5Mn0.5O2 and Li2MnO3. Other researchers proposed that these materials are composites with Li2MnO3-like nano do-mains embedded in the LiNi0.5Mn0.5O2 matrix. Most of these interpretations were based on the characterizations of the post-synthesized cathode materials; however, less attention has been paid to the cathode synthesis parameters, which can have a great effect on the material structure. The variation in starting materials and synthesis routines might lead to products with different structures. In this research, we investigated the reaction between Ni0.25Mn0.75CO3 and Li2CO3 with a molar ratios which can lead to these materials. A two-step phase formation is proposed based on the experimental results. In the first step, R-3m-like phase is formed due to the stoichiometric reaction between transition metal oxide and lithia. In the second step, C2/m- like phase is formed when the residual lithium carbonate decomposes at 700 °C, providing extra lithium necessary to form the Li2MnO3-like structure. The R-3m phase and C2/m- like phases are unevenly distributed among the cathode particles.. This observation is consistent with the reports that the Li- and Mn- rich cathode material usually exhibit a composite form.

Recently, layered-layered composite materials of Li[Li1/3Mn2/3]O2 (i.e. Li2MnO3) and LiMO2 (M = Mn, Co, and Ni) have been attracting a lot of attention due to their high reversible capacities of ~ 250 mAh/g when used as cathode materials in lithium ion batteries [1,2]. This type of cathode materials typically show a high voltage plateau at ~ 4.5 V vs. Li+/Li during the first charge, which is attributed to the simultaneous removal of lithium and oxygen from the structure, thereby providing an abnormal capacity [2, 3]. However, during repeated cycling, the continuous voltage depression (i.e., voltage fading) was also observed in the charge/discharge profiles. This implies that the material still undergoes gradual structural changes (e.g., atomic rearrangement) after the first charge. The voltage fading of this class material is a quite important issue from the practical point of view and should be resolved for its successful application to powering Plug-in hybrid electric vehicle (PHEV) and electric vehicle (EV). Therefore, systematic studies on the structural evolutions are needed to better understand the origin of the voltage fading behavior of this type of materials. Here we report the results of our studies on the structural evolution in the lithium rich Li1.2Ni0.15Co0.1Mn0.55O2 (i.e., 0.5Li2MnO3-0.5LiNi0.375Co0.25Mn0.375O2) material during prolonged cycling using in situ and ex situ synchrotron based X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS), and the relationship between these changes and the voltage fading during cycling. While in situ XRD was used to track the average bulk crystal structural changes, in situ XAS was applied to monitor the electronic structure and local structure changes around each transition metal element (Ni, Mn and Co) during prolonged cycling.
This work was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies under Contract Number DEAC02-98CH10886 for BNL and Contract No. DE-AC02-06CH11357 for ANL. The work at Institute of Physics, Chinese Academy of Sciences was supported by CAS Innovation project (KJCX2-YW-W26) and “973” project (2010CB833102 and 2012CB932900) are acknowledged.
References
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[3] A. R. Armstrong, M. Holzapfel, P. Novák, C. S. Johnson, S.-H. Kang, M. M. Thackeray, P. G. Bruce, J. Am. Chem. Soc., 128 (2006) 8694.

In the search for high capacity cathode materials for Li-ion batteries, layered oxides with the general formula Li(LiXMnYMZ)O2 (with M=Ni, Mn, Mg, Al, etc..) either described as xLi2MnO3-yLiMO2 are receiving much attention (1). These oxides are characterised by the presence of lithium in the transition metal layers, and high Mn content, leading to high capacities up to 250mAh.g-1. However, upon cycling, they present complex structural changes that are still misunderstood (2).
In this context, the evolutions of the structure occurring into the lithium rich layered cathode material which formula is Li1.2Mn0.61Ni0.18Mg0.01O2 have been studied. After evidencing the peculiar microstructure of the pristine material, we will detail the changes both upon the first electrochemical cycle and after 50 charge/discharge cycles, using state of the art advanced electron microscopy tools (Cs probe corrected High Resolution STEM, nanodiffraction, High Resolution STEM EELS spectrum imaging). In the pristine material, the analysis of electron diffraction patterns confirmed the ordering between the cations (Li or Ni with Mn) and the existence of disoriented domains stacked along the c axis. However, the partial solid solution of Ni into Li2MnO3 leading to a composite material is pointed out by the mean of HAADF-STEM imaging. Upon the first charge, a loss of material is shown to have occurred and the presence of a second phase identified as a defect spinel structure due to the transfer of transition metal cations to the interslab is clearly established at the edges of the particles. An interpretation of the Electron Energy Loss Spectroscopy (EELS) spectra collected during the first electrochemical cycle has been proposed, confirming this extra phase apparition from a chemical point of view and its irreversibility on discharge. The evolutions after long cycling test (50 cycles) have also been investigated. The phenomenon responsible for the ageing of the material and the decreasing of the electrochemical performances was investigated and the stability of the spinel defect structure is pointed out. STEM-EELS spectrum imaging experiments with layer resolution have been successfully recorded, revealing the chemical evolutions induced after these 50th cycles and the influence of the charge/discharge rate.
Finally, based on these experiments we will discuss the model according to which the material evolves on cycling.
(1) Thackeray, M. M.; Kang, S.-H.; Johnson, C. S.; Vaughey, J. T.; Benedek, R.; Hackney, S. A., J. Mater. Chem. 2007, 17, 3112.
(2) Lu, Z. H.; Dahn, J. R., J. Electrochem. Soc. 2002, 149, A815.

Focused ion beam-scanning electron microscopy (FIB-SEM) and transmission X-ray microscopy (TXM) were applied to two different types of commercial lithium-ion battery cathodes, LiCoO2 (LCO) and LiCoO2/Li(Ni1/3Mn1/3Co1/3)O2 (LCO/NMC) composite, to investigate the correlation between microstructural evolution and cell performance during cycling. Both fresh and cycled cells were examined by collecting images of multiple sample volumes from each cell. Microstructural parameters of the active materials including volume fraction, surface area and particle size distribution were statistically analyzed to assess data accuracy and to quantify microstructural changes during cycling. The comparison of fresh and cycled cells showed statistically insignificant changes in microstructure. Large spatial and cell-to-cell variations were found in the structures, especially in the LCO/NMC cathode, which limited the ability to resolve the cycling damage on the electrode microstructure. The appearance of transition-metal cations on the cycled anode surface, found by energy dispersive X-ray spectroscopy (EDS), may partially explain the observed ~30% capacity loss during charge/discharge cycles. Finally, the capability of observing conductive carbon and polymer binder domains within the electrode was also demonstrated with both FIB-SEM and TXM.

Spinel Li-Mn rich oxides form one of the most promising classes of high voltage cathode materials for next generation Li-ion batteries for electric vehicle applications. The main bottleneck in practical applications of these materials in Li-ion batteries is voltage fade, which is thought to be associated with the loss of oxygen during electrochemical cycling. However, the origin of this phenomenon still remains elusive. In this study we focus on investigating the role of oxygen vacancies on the ground state configuration and cation ordering, on the electronic structure and electrochemical properties of spinel LiNi0.5Mn1.5O4-δ. Using simulations based on the density functional theory, we show that the presence of neutral oxygen vacancies changes the oxidation states of Mn and Ni ions, which significantly reduces the Li+ and electron extraction energies. This effect is manifested as the low voltage tail on the voltage-capacity curves. Larger concentrations of vacancies lead to wider low voltage regions, which explains the experimental observation of voltage fade during electrochemical cycling. Understanding the origin of voltage degradation paves the way to improving the performance of LNMO cathode materials through either controlling the stability of the crystal through nanostructuring and/or coating or by introducing dopants, that increase the barriers for electron extraction near oxygen vacancies.

Development of new innovative experimental approaches and enabling methodologies to understand the function and mechanism of operation of materials and electrodes for Li-ion batteries is critical for electrification of transportation. A better understanding of the underlying principles that govern these phenomena is inextricably linked with successful implementation of high energy density materials.
Several analytical techniques have been implemented for the physico-chemical characterization of the materials, interfaces and interphases. In many cases limitations in studying the real system are imposed by ex situ methods that require excitation or detection of electrons or ions in vacuum environment and/or they suffer from inadequate sensitivity, selectivity and specificity in the in situ environemeent.
The advent of femtosecond (fs) lasers and near-field optical methods during the past decades has led to the development of new advanced techniques for chemical analysis This presentation provides an overview of novel in and ex situ experimental approaches aimed at probing battery materials and electrodes in electrical storage systems at an atom, molecular or nanoparticulate level.
The presented methodologies exploit the micro and nano-manipulation techniques and single particle model electrodes to provide sufficient sample definition suitable for advanced far- and near-field Raman, FTIR , fluorescence spectral microscopy, pumped laser probes and micro- and nano-electrochemical characterization techniques. Examples of detailed in situ molecular characterization of electrode surface and bulk processes at the nano-level scale exceeding the diffraction limit will be discussed.
Acknowledgement
Part of this work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy, under contract no. DE-AC02-05CH11231. It has also been supported in part by the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under award number DESC0001294. This work was also supported in part by the Chemical Science Division, Office of Basic Energy Sciences, Office of Nuclear Nonproliferation, and the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.

One of the challenges in correlating Li-ion battery performance with structure is the fact that working batteries and test cells consist of ensembles of millions of individual particles. Thus, most measurements of performance provide average properties that are difficult to correlate with structure. We have approached this issue by carrying out electrochemical measurements on single particles using an in situ approach that also allows for corresponding microstructural characterization. Measurements of a single particle can provide insight beyond that gained from bulk measurements, especially when well correlated knowledge of the microstructural changes that take place during electrochemical cycling. For example, in electrochemical cycling of single Li(Ni,Co,Al)O2 particles, we can identify the effect of intraparticle cracking and subsequent electrolyte penetration on capacity as a function of cycle. This information can provide new insight into the processes that take place during activation and formation cycling of full cells. Likewise, electrochemical cycling of single Li(Ni,Co,Mn)O2 particles shows signatures consistent with those observed in measurement of full cells. These correlations provide an opportunity to improve our understanding of changes in cell performance as a function of cycle. This presentation will highlight the insights offered by these approaches with a particular emphasis on the correlation of electrochemical cycling data between single particles and coin cell samples.
** Research sponsored by the U.S. DOE, Office of Science - Basic Energy Sciences and by U.S. DOE, EERE - Vehicle Technologies Program, under contract DE-AC02-06CH11357. The Electron Microscopy Center at Argonne is supported by the Office of Science - Basic Energy Sciences.

Olivine-structured LiFePO4 has been undergone intensive studies since the pioneering work by Padhi et al. [1] Considerable efforts have been devoted to the understanding of the phase transition mechanism. Various models, including core-shell model, mosaic model, shrinking core model, and domino-cascade model were proposed. It is generally accepted that in charging process, Li ions are extracted along [010] direction accompanied by the LiFePO4/FePO4 phase-boundary moving along a axis. Two-phase reaction mechanism has been confirmed in bulk level detected by in situ XRD [2] and quick EXAFS. [3] Recent investigations indicate that (1) the staging-II structures do exist for a half-delithiated LiFePO4 single crystal nanowire (d=65 nm, delithiated after two weeks), [4] (2) a LiFePO4/lithium-staging-II/FePO4 three-phase boundary was observed in a partially delithiated Nb-doped LiFePO4 sample (200nm, delithiated after 3 days), [5] (3) two phase fitting from the experimental soft-XAS spectra of the electrochemically delithiated LiFePO4 shows clear deviation (d=65nm, delithiated after 3 months). [6] Thermodynamically, two-phase separation was calculated to be the energetically more favorable configuration than single phase at room temperature. [7] Malik et al obtained a kinetic single phase transformation path through Monte Carlo simulations. [8] More recently, our DFT simulation reproduces the lithium-staging configuration at the interface, which is a kinetic-controlled metastable state due to the Fe center mediated inter-layer Li-Li interactions. [7] In this report, the phase transition mechanism of LiFePO4 at atomic level, which is related to anisotropic ionic and electronic transport properties, are discussed based on ABF-STEM, Quick-EXAFS, soft-XAS, in situ XRD investigations and DFT simulation.
Financial supports from CAS Innovation project (KJCX2-YW-W26) and “973” project (2010CB833102 and 2012CB932900) are acknowledged. The work at Brookhaven National Lab. was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-98CH10886. The work at the Lawrence Berkeley National Laboratory is supported by the LDRD program.
References
[1]. Padhi, A. K. et al, J. Electrochem. Soc., 1997, 144, 1188
[2]. Wang, X. J. et al , Chem. Commun.,2011, 47, 7170
[3]. Yu, X. Q. et al, Chem. Commun., 2012, in press
[4]. Gu, L. et al, J. Am. Chem. Soc. 2011, 133, 4661.
[5]. Suo, L.et al, Phys. Chem. Chem. Phys. 2012, 14, 5363.
[6]. Liu, X.S. et al, J. Am. Chem. Soc.2012, dx.doi.org/10.1021/ja303225e
[7]. Sun, Y. et al. Chem. Mater., 2012, under review
[8]. Malik, R.; Zhou, F.; Ceder, G. Nat. Mater. 2011, 10, 587.

Lithium titanate (Li4Ti5O12 or LTO) is an attractive negative electrode material for lithium-ion batteries for its superior rate capability and cycling stability to graphite. Due to its high cut-off voltage, however, the capacity of LTO is less than one half of that of graphite anode. We demonstrated that Al2O3 coated LTO by the atomic layer deposition (ALD) can be cycled with extended potential window down to 1mV vs. Li/Li+ with excellent cycling stability. Meanwhile, the specific capacity can be improved about 50% of its original capacity under the normal working potential window. We also demonstrated how a few atomic layers of Al2O3 coating can improve the C-rate performance compared with the uncoated LTO. We envision the Al2O3 coated LTO can be used as the negative electrode for start-stop battery with improved power/energy density.

Li-Ion batteries have gained wide spread use in numerous portable power applications including HEV and PHEV systems. Different applications have different requirements on key operating parameters such as cycle life and power needs. Of continuing concern with Li-Ion batteries is safety. Special materials are being developed to provide the unique operating conditions to meet the use scenario. Thermal analysis is one of the key methods to use in order to characterize the performance, safety and reliability of battery components and cells.

Capacitive energy storage offers a number of attractive features for grid applications including high power capability, fast response times, reliability and long-term cycling. As a result, carbon-based electrochemical capacitors, widely known as supercapacitors, show great promise in the areas of load-leveling, peak-shaving and various grid stabilization functions. The principal limitation with current supercapacitor technology is their low energy density. Increasing the level of energy storage would expand the opportunities for capacitive energy storage in grid applications and in energy storage systems for intermittent energy sources.
The interest in using pseudocapacitor-based materials for electrochemical capacitors is that the energy density associated with faradaic reactions is much greater, by an order of magnitude, than the electrical double layer capacitance of carbon electrodes. One key criterion is that fast faradaic reactions are required for electrochemical capacitors. Diffusion-controlled faradaic reactions of the type which commonly occur with battery electrode materials do not lead to the fast response times needed for grid applications. Our studies with Nb₂O₅ show that this material undergoes fast faradaic reactions that lead to high specific capacitance in short charging times, with values comparable to that of hydrous RuO₂. An important difference to note is that charge storage with Nb₂O₅ arises from lithium ion insertion in the bulk of the material while the pseudocapacitance occurring with hydrous RuO₂ is associated with surface or near-surface redox reactions. In recent studies we have quantified the kinetics of charge storage in Nb₂O₅ and identified the characteristics associated with the intercalation pseudocapacitance mechanism. Thick Nb₂O₅ electrodes offer the promise of exploiting this energy storage mechanism for high rate charge storage devices provided proper electronic conducting pathways are maintained.

In this talk, I will present our recent progress on rational synthesis and integration of nanoscale building blocks including both inorganic and organic components into desired architectures to optimize the fundamental energy transformation processes for high-performance energy storage devices including supercapacitors and lithium-ion batteries. First, I will present a unique class of polymeric materials, our newly developed conducting polymer hydrogels which exhibit 3D hierarchical nanostructures with multi-scale porosity. These hydrogels have demonstrated potential as high-performance supercapacitor electrodes with high specific capacitance (sim;480 F/g), excellent rate capability and cycling stability [1-3]. Second, I will introduce hybrid inorganic-organic nanostructure electrode systems for next-generation lithium-ion batteries which can offer significantly higher energy storage capacity (>5 times) than current technology [4,5]. I will discuss how the unique functions of conducting polymers can be utilized to overcome several fundamental challenges faced by those high capacity but insulating electrode materials such as sulfur (cathode material) and silicon (anode material).

Grid energy storage has emerged as one of the key technological challenges impeding the full integration of intermittent renewable energy technologies. A novel technology that can address this issue is the electrochemical flow capacitor (EFC). The primary difference between traditional flow cells and the EFC is that the EFC utilizes a flowable carbon-electrolyte slurry for capacitive energy storage. The EFC concept benefits from the advantages of both supercapacitors and flow batteries in that it is capable of rapid charging/discharging, has a long cycle lifetime, and enables energy storage and power to be decoupled and optimized for the desired application.
The performance of an EFC (capacitance at the required charge/discharge rates and flowability) is fundamentally dependent on the physical make-up of the electrode-electrolyte slurry. Low interparticle connectivity will negatively affect the rate-performance and electron transfer efficiency in the carbon slurry. Thus, the effects of carbon particle concentration, shape and size on the electrochemical and rheological performance of the slurry electrodes was investigated. Spherical porous carbon bead-like particles derived from phenolic resin (Mast Carbon, UK) and activated carbon (YP-50F, Kuraray, Japan) were compared as the carbon components of the slurry. Three different size distributions of carbon beads were used, ranging from approximately 9 to 385 µm. For the slurry electrodes examined, the specific surface area of carbon beads was found to be the most important factor in determining the specific capacitance of the slurries, while carbon particle size and size distribution effects the slurry viscosity.
Each material was studied at weight percentages of 16%, 20%, 23% and 27% in a sodium sulfate (Na2SO4) electrolyte. The slurries were electrochemically characterized using cyclic voltammetry and galvanostatic cycling in a static cell configuration. It was found that spherical carbon slurries with 23 wt% solid have specific capacitances of ~80 F g-1 over a thousand cycles at 200 mA g-1 and lower viscosities than anisometric activated carbon slurries.

Electrochemical capacitors store charges in an electric double layer set up by ions at the interface between a high-surface area material and a liquid electrolyte [1]. Many works have focused on the high surface exposed to the electrolyte in relation with the capacity. However, the best figure of merit requires the lowest electrical resistance to be combined with the largest capacity. And this is a real issue for devices based on oxides where the conductivity remains low because it is limited by intergranular transport.
For instance, cyclic voltammetry curves of supercapacitors should have a rectangular shape. However, for real systems, this rectangular shape is hardly observed, and a delay to the steady-state regime appears. By analogy with an equivalent electrical RC circuit, this delay can be attributed to a characteristic time tau;. This is the consequence of the presence of the macroscopic resistance in the circuit which depends on ion diffusion into the material and on electronic percolation in the system.
This work focuses on the analysis of the source of such resistances by electrochemical measurements. Samples were prepared under different applied pressures. Focus was given to the nanometric lamellar ionic conductor NaxCoO2, as for specific x values, this material should also be electronically conductive [2,3,4], and mixtures with carbon were also investigated.
Broadband Dielectric Spectroscopy measurements allowed determining the intrinsic electronic conductivity inside the grains constituting the powder assembly. NaxCoO2 has a metallic behavior at high frequencies. An electronic conductivity as high as 100 S/m was measured at 1.5 GHz.
Then, the electronic and ionic conductivity were investigated by electrochemical impedance spectroscopy as a function of the powder packing and carbon additive. The total resistance of mixtures of nanometric NaxCoO2 and carbon at low frequencies drastically decreases with application of a moderate pressure.
Based on this study, different electrodes formulations have been investigated. The best results have been obtained with direct casting of a slurry (active material, carbon and binder) onto an aluminum foil which is further pressed and heated.
As a conclusion, optimizing both electronic and ionic conductivity of an oxide system are the key elements to maximize the total measured capacity of thick electrodes. Moreover special attention on the electrode formulation drastically increases the measured capacity.
[1] P. Simon, Y. Gogotsi, Nature Materials 7 (2008) 845
[2] F. Tronel, L. Guerlou-Demourgues, M. Basterreix, C. Delmas, Journal of Power Sources 158 (2006) 722
[3] M. Pollet, M. Blangero, J.-P. Dourmec, R. Decourt, D. Carlier, C. Denage, C. Delmas, Inorganic Chemistry 48 (2009) 9671
[4] X. Pétrissans, A. Bétard, D. Giaume, P. Barboux, B. Dunn, L. Sicard, J.-Y. Piquemal, Electrochimica Acta 66 (2012) 306

This talk will briefly introduce the aqueous-based supercapacitor of the asymmetric type. Due to the usage of pseudocapacitive materials, some key factors determining the performances of such electrode materials with pseudocapacitance supercapacitors will be addressed. A typical example, mesoporous Mn3O4 with tunable microstructures, is employed to demonstrate the above concepts.
Porous Mn3O4 nanoparticles with tunable microstructures were synthesized from Mn(AcO)2 with Pluronic F127 as a dispersant. The amount of copolymer served as the surfactant in the precursor solution was varied to change/tune the specific surface area/porosity of Mn3O4. The textural and electrochemical properties of porous Mn3O4 nanoparticle were systematically characterized by the N2 adsorption/desorption isotherms, SEM, TEM, XRD, and i-E analyses. The interactions between manganese precursor and triblock copolymer during the self-assembly period can be used to control the microstructures of resultant oxides. Mn3O4 nanoparticles with tunable porosity and high surface area achieve the excellent capacitive performances for next generation supercapacitors. The specific surface area indicating the electrochemically active sites for charge storage/delivery as well as the pore structure indexed by the BJH pore volume, which affects the ion transportation and electrolyte permeation, have been demonstrated to be the key factors determining the capacitive performances of Mn3O4 in the low-rate and high-rate processes, respectively.
Mn3O4 is synthesized through thermal decomposition of a GO/Mn(AcO)2 mixture. GO served as a nucleation template in the thermal decomposition process. XRD, SEM, TEM, and TGA as well as specific surface area, pore size distribution, and CV are employed to characterize the porous Mn3O4. Due to introducing GO as the template in thermal decomposition, the resultant Mn3O4 shows a narrower pore size distribution, a larger specific surface area, and a larger pore volume in comparison with that without GO. The specific capacitance of Mn3O4 achieves 213.6 F/g at 25 mV/s in 0.1 M Na2SO4 and 70 F/g at 1000 mV/s. The high specific capacitance of such Mn3O4 is attributed to its high specific surface area and large pore volume, resulting in the effective exposure of electrochemically active sites and the facilitation of ion transportation. The excellent reversibility and good capacitive retention reveal the high-power characteristics of Mn3O4. The assembly of an asymmetric supercapacitor consisting of a Mn3O4 positive electrode and a graphene negative electrode shows a cell voltage of 2.4 V and its specific energy and power reach 13.8 Wh/kg and 9.2 kW/kg, respectively.

Multiple layer structure models of solid electrolyte interphase (SEI) on anode surface of Li-ion batteries[1-4] have been purposed over 30 years but never been visualized experimentally. Si is known as the most promising high capacity anode for next generation high energy density Li-ion batteries. However, the practical application is limited by its large volume variation combined with the continuous formation of unstable and electronic insulating SEI layer on fresh surface of Si electrode.[5] It is desirable to know the SEI structure clearly for further rational design.
In this work, the structure and mechanical properties of the SEI layer on Si thin film anode at different charge/discharge states have been detected by a force curve method of scanning probe microscopy, which has been used in detecting SEI film on MnO anode. [6] It is confirmed that single layer, double layer, multiple-layer structures with varied Young&’s Modulus and thickness coexist on the surface of silicon. The SEI layer grows continuously during electrochemical lithiation. The SEI layers with higher Young&’s modulus have higher probability to appear at the bottom layer. The total coverage of the SEI layer is less than 60% even when the electrode was discharged to 0.005 V vs Li+/Li and kept potentiostatic for 48 hours and then stayed at 55 oC. The formed SEI layers with lower Young&’s modulus tend to decompose even when the charging voltage is as low as 0.6 V vs Li+/Li. Above information points out that the standard electrolyte is not effective to form dense passivating films on lithiated Si anode. This may explain the fact that the columbic efficiencies of Si anode after the first cycle are always much lower than graphite anode. Based on force curves tested in each scanning point, 2D projection plots and 3D plots for the SEI on Si anodes at different discharged and charged state have been drawn. Obviously, this method could be also used to identify the influences of the type of the electrode material, coating layer, temperature, rate, additives in electrolyte on the formation and structure of the SEI.
Financial supports from CAS Innovation project (KJCX2-YW-W26) and “973” project (2010CB833102 and 2012CB932900) are acknowledged.
References
[1] D. Aurbach, et al, J. Electrochem. Soc. 1995, 142, 2873.
[2] E. Peled, et al, J. Electrochem. Soc. 1997, 144, L208.
[3] K. Xu, Chem. Rev. 2004, 104, 4303-4417
[4] S. P. Kim, et al, J. Power Sources 2011, 196, 8590- 8597
[5] H. Li et al, Adv. Mater. 2009, 21, 4593-4607
[6] J. Zhang et al, Nano Lett. 2012, 12, 2153minus;2157

Carbon-Li4Ti5O12 (LTO@C) and carbon nanotube (CNT)-Li4Ti5O12 (CNT@LTO) nanocomposites have been successfully synthesized by high-temperature calcinations and carbonization using a mixture of precursors of micro-sized Li4Ti5O12 and conducting black and carbon nanotubes, respectively.
Two different type coating layer have been characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (TEM, HR-TEM), selected area electron diffraction (SAED), and x-ray photoelectron spectroscopy (XPS) analysis. The LTO@C exhibited a spinel cubic spherical nanocrystal with average sizes around 50-70 nm. The CNT@LTO showed uniform square nanocrystal with edge length around 40 nm. HR-TEM images and SAED patterns at nano-scale confirmed that two types of carbon layer nature and coating thickness on the surface of the nanocrystal. The graphitic phase coated spherical LTO@C nanocrystal was further confirmed with Raman spectroscopy and XPS analysis. The CNT interconnection networks within CNT@LTO nanocrystals were apparently revealed.
Electrochemical studies of galvanostatic discharge/charge testing and cycling performance indicated that the CNT@LTO particles show much improved rate capability and specific capacity than that of LTO@C particles when used as anode materials for lithium ion batteries. There is also clear evidence of the CNT interconnection networks give rise to improve the kinetics of Li4Ti5O12 toward fast lithium insertion/extraction, which demonstrated that CNT interconnection networks is highly effective in improving the electrochemical properties of those Li4Ti5O12 nanocomposites applied as the anode candidate in advanced Li-ion cell.

The purpose of this work is to better understand the sintering behavior of a novel ceramic electrolyte based on the garnet-structure with the nominal formula: Li7La3Zr2O12 (LLZO). LLZO is a promising ceramic electrolyte that has the unique combination of: i) electrochemical stability between 0-6 V vs Li/Li+, ii) ~ 1mS/cm conductivity at 298K and iii) stability in air The ultimate goal is to develop ceramic processing technology to enable the cost effective fabrication of relatively thin (< 100 micron) membranes for use in advanced, large format batteries for vehicle and grid energy storage. To this end, we studied densification based on the LLZO powder particle size and temperature under fixed uniaxial pressure (40 MPa). Relatively large (~ 1 micron) and relatively small (~ 100nm) LLZO particles were synthesized using conventional solid state and sol-gel techniques, respectively. Additionally, both aluminum and tantalum are commonly added to stabilize the preferred cubic LLZO phase, thus the effect of sintering based on the dopant type was also investigated. The specific goal of this work is to maximize the density to improve ionic conductivity and mechanical integrity of LLZO electrolyte membrane technology.

Lithium-sulfur (Li-S) batteries, based on the conversion reaction of 16Li+S8harr;8Li2S , supply a theoretical specific energy 5 times greater than that of lithium-ion batteries (2,500 vs. 500 Wh kg-1).1, 2 A typical Li-S cell is consisted of a sulfur-carbon composite as the cathode, a metallic lithium as the anode, and a liquid electrolyte that has a high solubility of lithium polysulfides as a pre-requisition for the electrochemical cycling of the sulfur-containing cathode. Although much effort has been dedicated to improving the performance of the sulfur cathode,3, 4 the dissolution of sulfur in the liquid electrolyte and the use of elemental lithium as the anode are still key limitations for practical use of Li-S batteries: The dissolved lithium polysulfide leads to an intrinsic short cycle-life of Li-S batteries; In addition, safety concerns stem from the use of highly reactive metallic lithium anode and the dendritic growth of lithium metal that penetrates the separator and causes fire hazards.
To promote the high performance and alleviate the safety concerns of Li-S batteries, this research brings forward the all-solid configuration of Li-S batteries with lithium sulfide (Li2S) as a prelithiated cathode, which avoids the direct use of metallic lithium as the anode. A solid electrolyte has been utilized to eliminate highly flammable liquid electrolytes. More importantly, the solid electrolyte excludes the migration of sulfur species and thus promises a long cycle-life of Li-S batteries. Significant challenges of cycling all-solid Li-S batteries lie in the poor electronic and ionic conductivities of Li2S. In this talk, we will show the improved cycling performance of all-solid Li-S batteries that have demonstrated high capacity, good capacity retention, and excellent coulombic efficiency. The nanostructure of Li2S cathode is crucial to the high performance of all-solid Li-S batteries. Desirable physical properties such as high ionic and electronic conductivities originating from the nanostructure of Li2S will be discussed in details.
References:
1 C.D. Liang, N.J. Dudney, J.Y. Howe, Chem Mater, 2009, 21, 4724.
2 Z. Lin, Z. Liu, W. Fu, N.J. Dudney, C. Liang, Adv Funct Mater, 2012, 10.1002/adfm.201200696.
3 Z. Liu, W. Fu, C. Liang, Lithium-Sulfur Batteries, in: Handbook of Battery Materials, Wiley-VCH Verlag & Co. KGaA, Weinheim, Germany, 2011, pp. 811.
4 X.L. Ji, K.T. Lee, L.F. Nazar, Nat Mater, 2009, 8, 500.
Acknowledgment:
This work was sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy through the Batteries for Vehicle Transportation Program. The synthesis of materials was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.

We demonstrated the formation of hierarchically porous carbons by templating process. Specifically, self-assembled polymeric colloidal crystals were applied as a hard template for macropores. The macroporous structure could be conveniently controlled with adjusting pore sizes of hard template. The surface of 3D macroporous carbons was modified with aminophenyl groups using diazonium chemistry to investigate the effect of surface functional groups. Also, block-copolymers were used to introduce mesopore structure to investigate the effect of increasing surface area and mesoporosity. They were applied to anode materials for lithium-ion half-cells. The structural and morphologic properties of different carbon materials were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmet-Teller (BET) analyses and the chemical bonding was analyzed by X-ray photoelectron spectroscopy (XPS). Electrochemical property was analyzed by galvanostatic charge/discharge cycling of the cells. These carbon materials have large surface area, accessible porous structure and good electron conductivity. The specific capacity of lithium-ion half cells with these carbon-coated anodes reached 432 mAh/g reversible capacity at current density 100 mA/g. The specific capacity of mIOC was approximately twice that measured using only the macroporous IOC electrode that previously reported (223 mAh/g).

In this work we have focused on morphological modification of graphene nanosheets for enhanced charge storage. Towards this end, we report a very simple room temperature pre-reduction treatment for graphite oxide (GO) which introduces hierarchical nano-perforations in GO sheets. This involves simple chemical synthesis such as room temperature stirring of aqueous GO dispersion with colloidal ludox (12 nm SiO2 nanoparticles) solution followed by acid etching of silica nanoparticles. The corresponding material, termed as hierarchically perforated graphite oxide (HPGO), on subsequent reduction produces hierarchically perforated graphene nanosheets (HPGN). The perforations introduced in HPGO are seen to be maintained after reduction in HPGN, albeit with some modifications. It is well-known that symmetric ultracapacitor (UC) made up of chemically synthesized graphene usually shows specific capacitance (Cs) in the range of 100 - 300 F g-1 for aqueous electrolyte systems but at low current rates. These Cs values are not stable at high current density and considerable decay in the Cs values is observed. We tested UC properties in 1M H2SO4 of our perforated graphene (HPGN) as an electrode material. A remarkably high Cs of 450 F g-1 is observed at an applied current density of 0.25 A g-1, with an energy density of 62.5 Wh kg-1. At high current rate 20 A g-1 HPGN showed Cs of 204 F g-1. For comparison purpose we also synthesized graphene nanosheets (GNs) (without perforations) which gave a specific capacitance of only 130 F g-1 at 0.1 A g-1 which is significantly lower than that by HPGN based cell. HPGN based UC showed good cycle study with small fading (7%) of Cs after 1000 cycles at a high current rate of 2 A g-1.

Development of energy storage systems, in particular, high performance batteries have become imperative owing to demanding applications such as electric vehicles (EVs) and smart grids. Since the battery performance is a major reflection of its constituent electrode materials, tailoring electrode properties would be highly relevant. In this context, we demonstrate a rational design platform for active material and electrodes with the following aspects: (i) an optimal particle size to reduce the lithium diffusion length, (ii) a conducting matrix to facilitate electron transport (iii) adequately large active material surface area to promote electrolyte wettability and (iv) strong electrode material-current collector adhesion to preserve the electrical connections between the active material and current collector. Such rationally designed electrodes are expected to abet electrochemical performance.
To verify this supposition, the design aspects were incorporated on selected electrode materials namely α-Fe2O3 and Fe3O4 that store lithium by conversion reaction. Rationally designed α-Fe2O3 exhibits a record high first cycle coulombic efficiency of 90%. While, the tailored Fe3O4 electrode exhibits excellent storage performance with a capacity of 950 mAh g-1 at 1C. Even at very high current density of 10 C (9.26 A g-1), Fe3O4 electrode delivers 65% of their theoretical capacity (610 mAh g-1) and cyclability over 1100 cycles without capacity degradation. Both these tailored anodes also show feasibility in a real full cell containing olivine cathodes. Finally, we discuss the possibility of analogous sodium storage in metal oxides incorporating above design considerations.

We report the synthesis of α -Fe2O3 nanospindles derived from Fe-based metal organic framework (MOF) by controlled thermal pyrolysis in air. Presence of phase pure structure and nanospindle morphology are investigated through XRD and SEM/TEM analysis. α -Fe2O3 is known to exhibit good battery characteristics with very high theoretical capacity of ~1007 mAh g-1. Herein we show that MOF-derived nanospindles of α -Fe2O3 working as anode material in a Li/α-Fe2O3 half-cell deliver a capacity of ~1487 and ~1024 mAh g-1 for the first discharge and charge, respectively at current density of 100 mA g-1. The irreversible capacity of ~463 mAh g-1 noted for α-Fe2O3 nanospindles is normal for the case of conversion type anode materials. Reversible capacity is a bit higher than the theoretical capacity which can be attributed to the extra Li ion storage via a reversible non-faradaic mechanism called pseudo-capacitance which is an interfacial reaction due to the charge separation at the metal/Li2O phase boundary. The cells are shown to deliver a very stable cycling profile of measured 40 cycles without any drastic capacity fade and retain over 90% of initial reversible capacity. The coloumbic efficiency is found almost close to 97% except for the few initial cycles, which indicates good reversibility. We also checked the electrochemical performance of α-Fe2O3 nanospindles under high current cycling. For example, at a high current rate of 1 A g-1 MOF derived α-Fe2O3 nanospindles delivered the reversible capacity of 430 mAh g-1, which is almost the same capacity as that of graphite. After scanning up to high current rate from 0.1 to 4 A g-1 and finally bringing down the current rate to 0.5 A g-1 it is observed that α-Fe2O3 nanospindles showed almost the same reversible capacity of ~690 mAh g-1 which implies a good rate capability and retention of the material. The results discussed clearly reveal that MOF-derived functional materials represent a unique synthesis approach to yield high performance iron oxide anodes. This approach can be easily extended to other transition metal oxides to develop high performance electrode materials.

Sulfur is one of the most promising cathode materials, with its theoretical specific capacity of 1675 mAh/g (the highest value for all known solid cathode materials), for the next generation of rechargeable batteries. However, the poor rechargeability and the fast capacity degradation owing to the insulating nature of sulfur and the dissolution of various soluble polysulfide intermediates formed during discharge process into the electrolyte are the major hurdles inherent in Li/S batteries that hindered their mass commercialization. The development of new battery architectures is essential to overcome these problems for Li/S batteries to succeed. In this study, the three-dimensional electrodes based on carbon nanotubes are utilized as electrode substrates to load sulfur inside their matrix. Two types of CNT based materials are examined in comparison to each other: MW-CNT buckypapers and vertically aligned carbon nanotubes (VACNT) are investigated as the 3D cathode materials. (The VACNTs are directly synthesized on stainless steel substrate by employing alumina catalyst support layer and a CVD process.) Carbon nanotubes, as a highly conducting form of carbon, can facilitate essential intimate contact of insulating sulfur to enable a reversible electrochemical reaction at high current rates. MW-CNT paper with large specific surface area and abundant micro- and meso-pores and VACNTs with its interconnected highly ordered structure, both exhibit a unique conductive matrix to confine sulfur in between their porous structures and deliver the ions and electrons efficiently to the sulfur. Moreover, they provide good structural stability of the cathode. The CNT/Sulfur composites are prepared by a melt-infiltration and sublimation/condensation strategy with post heat treatments. The sulfur loaded CNT electrodes are further coated with conducting polymers. This external layer hinders the out-diffusion of the soluble polysulfides formed during discharge process into the electrolyte by encapsulating and adsorbing these intermediates in its unique highly torturous pore structure. These materials are tested as novel cathodes for Li/S batteries and the results demonstrate improved cyclability of the cells and the utilization of sulfur.

Lithium polymer batteries offer a number of advantages to standard lithium ion batteries, including an all-solid state structure, increased safety, and the potential to be combined with lithium metal anodes for increased energy density over lithium intercalation anodes. However, the low-temperature (< 80 °C) ionic conductivity of polymer electrolytes has remained a major limitation over the past 40 years of academic investigation into polymer electrolytes. Progress in understanding strategies for systematic improvement in ionic conductivity has been dominated a single polymer for elucidating structure-property relationships in ionic conducting polymeric solids, i.e., poly(ethylene oxide). By increasing the domain of polymer materials to include a family of structurally related polymers with systematic variation in physical properties, fundamental insight into the relationship between polymer properties and ionic conductivity can be gained. We have synthesized a library of poly(glycidyl ether)s that exhibit systematic differences in glass transition temperature (Tg), viscosity, oxygen-content, dielectric constant, and ionic conductivity. In this presentation, we will discuss the synthesis, characterization, and performance of poly(glycidyl ether) based electrolytes and the insights they provide into future polymer electrolyte design.

Rechargeable lithium-ion batteries are the forerunning electrical energy storage system of today; however, the evolving applications of grid energy storage and all-electric vehicles desire greater energy and power densities and faster charge-discharge cycling than present-day material combinations can provide; while also reducing weight and size. Here, we report on the characterization of a novel hybrid architecture consisting of a forest-like nanostructure of vertically aligned carbon nanofibers (VACNF) coated coaxially with a thin layer of a highly lithium-active material to form a core-shell nanowire structure for use as an electrode in the next generation of lithium ion batteries. The VACNFs template offers a unique freestanding brush-like structure where each carbon nanofiber (CNF) is strongly anchored to the substrate and fully separated from others, leaving sufficient space for uniformly coating additional materials. The coated material can be easily deposited onto the CNFs by several methods to have increased surface area, while the fiber provides a highly conductive electron pathway between the shell material and the current collector.
In our initial study, pure silicon was employed as an anodic material, known to have a theoretical capacity nearing 4200 mAh/g, which greatly exceeds the 370 mAh/g of commercial graphite anodes. However, silicon is prone to pulverization due to greater than 300% volume expansion upon lithiation, which leads to capacity fading and reduced electrode life. Our core-shell nanowire architecture enables the silicon shell to expand radially, releasing the stress facile upon lithium insertion while maintaining reliable and efficient electrical connection to the current collector through the VACNFs. Results have shown that a silicon coating with the nominal thickness of 500 nm and 1500 nm presents a lithium storage capacity of ~3,200 to 3,600 mAh/g at C/1 and C/2 power rates, with greater than 99% columbic efficiency. Besides the loss at initial cycling owing to the formation of solid electrolyte interphase, the capacity remains relatively stable in the following charging/discharging processes, upwards of 100 cycles. Scanning and transmission electron micrographs show that the silicon-coated VACNF nanowires are very robust and able to retain their shape and nano-architecture after significant cycling. This concept is being expanded to cathode materials, such as titanium oxides, manganese oxides and other lithium active materials, which will be coated onto VACNFs.

Germanium holds great potential as an anode material for lithium ion batteries due to its large theoretical capacity. Furthermore, its superior intrinsic properties related to the kinetics, such as electronic conductivity and lithium diffusivity, result in excellent power density. However, the problem related to tremendous volume change of Ge during cycling is the dominant obstacles for its practical use. Therefore, the previous researches have been focused on developing the electrode configuration for the improvement in mechanics associated with lithium without consideration to the kinetics. In this study, we demonstrate that the structural engineering of the electrode configuration enables the improvement in kinetics as well as favorable mechanics. Two types of Ge inverse opal structures with porous wall and dense wall were prepared by using confined convective assembly method and adjusting Ge deposition parameters in chemical vapor deposition system. Ge inverse opal electrode with porous wall shows much improved electrochemical performances, especially cycle performance and rate capability, than those of the other one. These improvements are attributed to large free surface, which offer facile strain relaxation way and large lithium flux from the electrolyte to active material.

Silicon is the most encouraging material as next generation anode materials for lithium ion batteries because of its high specific capacity. However, silicon has been suffered from extreme volume change over 400% during lithiation /delithiation. To mitigate such a change, in this study, amorphous SiO2 layer was introduced on the urchin-like Si particles via thermal oxidation. Further, its coating thickness was optimized by electrochemical cycling testing. Urchin-like Si particles with different thickness of SiO2 coating layer (~2 nm (native oxide layer), ~6 nm, ~38 nm, ~58 nm, ~121 nm) were synthesized and were characterized by TEM, XPS, and EDS analysis. Among the samples, Si particles with the coating thickness of ~38 nm SiO2 showed the best electrochemical performance. This sample showed an initial discharge capacity of 2279 mAh/g with a columbic efficiency of 92% and retained 83% capacity retention after 50 cycles at 0.2 C-rate in a coin-type half-cell. On the other hand, when the coating thickness increased to ~121nm its initial capacity and columbic efficiency significantly decreased to 774 mAh/g and 83%, respectively. In addition, an electrode thickness change after cycles showed that the SiO2 coating layer effectively reduced the volume expansion degree of the urchin-like Si. For instance, the electrode thickness of the Si particles with the ~38 nm coating layer was expanded to 116%, while that with ~ 2nm was expanded to >300% after 50 cycles.

MnO2 is a valuable electrode material in lithium ion batteries due to its high storage capacity but it suffers from poor electrochemical performance caused by low electrical conductivity and large volume expansion. Recently, electrodes based on coaxial arrays of MnO2/carbon nanotubes were shown to offer some potential to overcome the limitations of MnO2-based electrodes, but the electrochemical cycling performance was still poor. Here, we demonstrate a core-shell nanostructure of vertically aligned multi-walled carbon nanotube (MWNT)-MnO2 which is directly connected with a current collector. Such structures were prepared via a facile reduction of KMnO4 by surface carbons, which promote adhesion between core and shell materials. This electrode delivers a high specific capacity of ~910 mAhg-1 at a current density of 100 mAg-1 even after 50 charge/discharge cycles. In addition, results reported here provide a first systematic explanation of the influence of different surface coverage of MWNT with MnO2 shell layer on the electrochemical performance of the core-shell electrode, which yields valuable insights into the development of lithium ion batteries that are free from capacity fading caused by electrode pulverization.

Because of its high theoretical capacity, silicon has been extensively investigated as one of the promising high capacity anode materials for lithium-ion batteries. However, their practical applications have been hindered by several barriers, including large volume expansions and phase transformations during lithiation and de-lithiation, which lead to rapid capacity fading during charge/discharge cycles. Various nanostructured silicon-based materials have been developed to mitigate this problem. Here, we designed simple methods to synthesize hollow core-shell structured porous Si-C nanocomposites with void space up to tens of nanometers to accommodate the volume expansion during lithiation for high-performance lithium-ion battery anodes. An initial capacity of ~760 mAh/g after formation cycles (based on the entire electrode weight) with ~86% capacity retention over 100 cycles is achieved at a current density of 1 A/g. This rationally designed nanocomposite has three major advantages that ensure the good electrochemical performance: 1) the porous structure has sufficient empty void space between the Si core and the carbon shell, as well as among the hollow core-shell structured particles, to tolerate the volume changes occurring during charge-discharge cycles; 2) the spaces between the Si cores and the carbon shells can alleviate deterioration of the carbon shell; therefore, good electrical contact of nano-Si particles is maintained during cycling; 3) the carbon shell, in addition to improving the electrical conductivity, also acts as a shielding layer that helps keep the solid electrolyte interface (SEI) layer intact during cycling, which can reduce electrolyte decomposition and improve the cycling stability of silicon based anodes.

Due to the excellent capacity around 4000 mA h g-1, silicon has been recognized as one of the most promising lithium-ion battery anodes, especially for future large-scale applications including electrical vehicles and utility power grids. Nevertheless, Si suffers from its short cycle life as well as the limitation for scalable electrode fabrication. Herein, we report a novel design for highly robust and scalable Si anodes: Si nanoparticles embedded in porous nitrogen-doped carbon spheres (NCSs). The porous nature of NCSs buffers the volume changes of Si nanoparticles and thus resolves critical issues of Si anode operations, such as pulverization, vulnerable contacts between Si and carbon conductors, and unstable sold-electrolyte interphase. The unique electrode structure exhibits outstanding performance with a gravimetric capacity as high as 1,579 mAh g-1at a C/10 rate based on the mass of both Si and C, a cycle life of 300 cycles with 94 % capacity retention, as well as rate capability of 6 min discharging while retaining a capacity of 702 mAh g-1. Significantly, the coulombic efficiencies of this structure reach 99.99 %. The assembled structure suggests a design principle for high capacity alloying electrodes that suffer from volume changes during battery operations.

Lithium-Ion batteries (LIBs) are currently used for portable devices and enter the electric vehicles market. Silicon is the most promising material to replace graphite which is the classical used anode. Silicon has the much greater theoretical specific capacity of 3580 mAh/g, about ten times larger than graphite. Nevertheless Si undergoes a 280% volumetric expansion when alloying with lithium ions during the discharge of the Li/Si battery. This expansion leads to fractured micrometric particles or an unstable solid-electrolyte interphase (SEI) for the nanometric particles reducing for both cases the electrode cycle life-time. In this context, the lithiation mechanism (Li-Si alloying) is not completely understood [1-3]. We studied two kinds of powders: micrometric (1-10µm) and nanometric powder (50nm) at different lithiation states during the first discharge of the batteries until reaching the crystallized phase Li₁₅Si₄.
We have then investigated both micrometric and nanometric silicon powders by high angle annular dark field (HAADF/STEM) imaging, nanobeam electron diffraction (NBED) and electron energy loss spectroscopy (EELS) experiments. HAADF images show fractures of the micrometric silicon particles from 10% lithiation and an anisotropic lithiation leads to faceted nanoparticle silicon core during the electrochemical process. Moreover NBED revealed a slightly disorientation in between fractured micrometric silicon particles with respect to original big particle. For the nanoparticles powder, irreversible phases as Li₂O during the first lithiation was mainly observed on the surface due to the lithiation of native SiO₂. We used valence and core electron energy-loss spectroscopy to provide chemical information in order to propose a lithiation mechanism. References EELS spectra were acquired on synthesized or commercialized synthesis of Li₂O, Li₄SiO₄, Li₂SiO₃ and Li_xSi alloyings: Si (x=0), Li₁₂Si₇ (x = 1.7), Li₇Si₃ (x = 2.3), Li₁₃Si₄ (x = 3.3), Li₂₂Si₅ (x = 4.4) and Li metal. Prior to establish the lithiation model, and based on these references, we have clearly established the electron beam damage mechanism and defined suitable parameters to perform free of damage experiments. EELS analysis show a chemical shift of the plasmon peaks for Li_xSi alloyings moving from 7eV for pure Li metal to 16.8eV for silicon. We used the relationship between the Li content in the Li_xSi alloyings and the position of the plasmon peak [4] to identify the Li_xSi phases at different cycling states. In this way we determined the lithiation process in the silicon core.
The coupling of all these experiments will allow us to clearly demonstrate the complex core-shell model according to which the lithiation occurs.
References:
[1] M. N. Obrovac et al., J. Electroch. So., (2007)
[2] T. D. Hatchard et al., J. Electroch. So., (2004)
[3] B. Philippe et al., Chem. Mater., (2012)
[4] J. Danet et al., Phys. Chem. Chem. Phys., (2009)

There is extensive interest in the application of conversion electrode materials such as Ge and Si as anode materials for Li ion battery (LIB) anodes due to the very high specific capacities. However, Ge and Si experience large volumetric changes of ~400 % during lithiation (charging) and delithation (discharging). In solid film electrodes, this ultimately leads to loss of electrical contact due to intra-material fracture and/or delamination at the electrode/current collector interface. This talk will further explore the application of ion beam mixing at the electrode/current collector interface on the crack formation process during cycling.
Si electrodes were fabricated by depositing 350 nm of material onto Ni-Fe foil substrates using electron beam evaporation. The electrodes were then Si+-implanted at 250 KeV to doses of 1.0×1013 - 1.0×1016 cm-2. This implant energy was sufficient to place the projected range of the ions at the Si/Ni-Fe interface. Cells for electrochemical testing were prepared in sealed pouches in an Ar atmosphere (H2O concentration < 0.9 ppm) using single-ply 50 mu;m-thick polypropylene separators and 1.0 M LiPF6 in 1:1 (by volume) ethylene carbonate:dimethyl carbonate liquid electrolyte with the Ge film on Ni-Fe foil substrate as one electrode and Li metal foil as the other electrode (half-cell configuration). The electrochemical properties of the electrodes were evaluated with galvanostatic (constant current) cycling and cyclic voltammetry; a voltage range of 0.01 to 2.00 V was used. The morphological and structural evolution of the electrodes was evaluated with high-resolution cross-sectional transmission electron microscopy and scanning electron microscopy. The crack formation was followed as a function of implant conditions and electrochemical cycling conditions. There is a critical dose around 1.0×1015/cm2 at which the adhesion is dramatically improved at the interface and this correlates well with a significant decrease in crack spacing observed by SEM. The data suggests that as the thin film adhesion improves during ion beam mixing, the crack spacing continues to diminish in order to accommodate the high stresses associated with expansion.

Si-based anodes, as a host for Li in Li-ion cells, are of increasing interest because of their high specific capacities. During lithiation, Si forms a series of compounds of varying stoichiometry, eventually forming Li₂₂Si₅ at maximum lithiation. When Si is lithiated to Li₂₂Si₅, it provides a theoretical specific capacity of ~4200 mAh/g, which is the highest among metals. However, the volume change upon lithiation, which can be up to 400%, causes pulverization of the anode material and subsequent loss of storage capacity and cyclability. One approach to overcome this challenge is to use porous Si anodes which can better accommodate the large strains arising from the volume changes. This research is focused on fabricating Si anodes with nano-sized columnar structures. Electrochemical insertion and de-insertion of Li were carried out in Si electrodes with different columnar morphologies. The effect of columnar nanostructure of Si on the cyclability and the capacity is discussed.

In this work, we successfully demonstrated the fabrication of a hybrid carbon-silicon composite nanostructure via using a sputtering evaporation system. Three dimensional graphene-carbon nanotube hybrid nanostructure foam was grown on metal foam through a one-step chemical vapor deposition (CVD) by introducing a mixture precursor gases (H2, C2H4). The as-grown carbon nanostructure foams can be potentially used for the electrodes of energy storage devices such as supercapacitors and battery. We further explored sputtering evaporation system to uniformly deposited a layer of amorphous silicon on the as grown 3D carbon nanostructure foam. The surface morphologies were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM). The results demonstrated relatively homogeneous and densely packed 3D hybrid carbon-silicon nanostructure with a very high porosity. Cyclic voltammetry, charge-discharge, and electrochemical impedance spectroscopy (EIS) are conducted to determine the performance of the 3D hybrid carbon-silicon nanostructure for lithium ion battery anode. The lithium-ion battery based on this hybrid carbon-silicon nanostructure shows a high specific capacity of ~2500 mA h g-1. This hybrid carbon-slicon nanostructure offers a facile and binder-free technique to obtain high capacitive lithium ion battery anodes.

We demonstrate the reversible lithiation of SiO2 up to 2/3 Li per Si, and propose a mechanism for it based on molecular dynamics and density functional theory simulations. Our calculations show that neither interstitial Li (no reduction), nor the formation of Li2O clusters and Si-Si bonds (full reduction) are energetically favorable. Rather, two Li effectively break a Si-O bond and become stabilized by oxygen, thus partially reducing the SiO2 anode: this leads to increased anode capacity when the reduction occurs at the Si/SiO2 interface. The resulting LixSiO2 (x < 2/3) compounds have band-gaps in the range of 2.0-3.4 eV. (Published in Applied Physics Letters 100 (2012) 243905.)

A current problem with Li-ion battery technology in the electric vehicle and electric hybrid vehicle market is the slow recharge rate of the battery in comparison to liquid fuel. A gas car can simply drive into a gas station, refuel, and immediately have the ability to “recharge” the car&’s driving capacity. Current electric vehicles require hours of charging to get to full charge. To improve the existing commercial electric vehicle performance with the least infrastructure influence, a substitution experiment was proposed to replace, rather than introduce.
Spherical conductive carbon was substituted with vapor grown carbon fibers in a Li4Ti5O12 anode system. The incorporation of the carbon fiber caused percolation to occur at lower weight concentrations allowing for more active material to be incorporated per unit weight, effectively increasing the energy density of the material. This percolation was measured via four probe conductivity measurement of the anode material on glass slides. The mechanical rigidity of the carbon fiber increased physical stability of the system allowing for more aggressive intercalation of Li ions into the system. This meant that in comparison to an anode with conductive carbon, the vapor grown carbon fiber anode battery could be discharged at higher rates with less damage to the microstructure. This effect was characterized using cycle testing of coin cells in addition to characterizing the microstructure via scanning electron microscope.
The vapor grown carbon fibers were incorporated into the system via a physical mixing protocol that closely represents the incorporation of conductive carbon in commercial processes. The carbon fibers were added into the film making process along with PVdF binder to make viscous slurry. The slurry then was coated onto Cu foil and dried to make a uniform film. The coating was then punched and a half cell was assembled under Argon atmosphere using Li metal as the cathode. The battery was then tested at low current draw to show proof of improved or similar performance with carbon. In addition, the cell was subject to step rates of incrementally increasing rates to test the improved rate capabilities of the carbon fiber anode system. The carbon fiber incorporated anode noticeably performed better at higher rates than the conductive carbon. At 10C, the vapor grown carbon fiber|Li4Ti5O12 anode outperformed the conductive carbon|Li4Ti5O12 achieving over 20% improvement in capacity at 400 cycles.

With increasing demanding of energy, it becomes more and more important to find alternative energy sources beyond fossil fuel. Batteries, especially lithium ion batteries (LIB), provide unique advantages with their high energy densities (up to 150 Whkg-1). To meet the requirement for applications in electric vehicle (EV) and hybrid electric vehicle (HEV), it is desirable to develop high energy density and low cost materials. With current Li-ion technology, lithium in the cell is limited from cathode material, e.g., LiCoO2 etc., and electrolyte. Solid-Electrolyte Interphase (SEI) formation during initial cycles consumes lithium and results partial capacity loss irreversibly. The incorporation of stabilized lithium metal powder (SLMP), developed by FMC corporation, into anode has been suggested to overcome the irreversible capacity loss, and increase the capacity by 5~10%. Moreover, some non-lithiated materials with high specific capacities can be used as cathode materials if coupled with pre-lithiated anodes. With this strategy, the full cell energy density can be significantly improved.
In this report, we demonstrate the application of SLMP in anode materials. To apply SLMP into the anode electrodes, two strategies have been applied: SLMP was either added into electrode slurry for film casting, or sprayed directly on top of anode laminate. The prelithiated anodes were allowed to rest for different time periods before cycling. Without any low C-rate formation, the cycling results suggest that the anode prelithiation can help the development of SEI.
In this study, CGP-G8 graphite from Conoco Phillips was homogenized with styrene-butadiene rubber (SBR), acetylene black (AB) and SLMP in toluene to make slurry with the weight ratio of: 88% CGP-G8, 5% SBR, 5% AB, and 2% SLMP. With the incorporation of SLMP, the open circuit potential dropped quickly from 2.3V to 0.1 V, indicating the partial lithiation of graphite. Half cell performance for SLMP-lithiated graphite anodes with different resting time indicate that the cell without resting has significant capacity drop during the first 10 cycles. With increasing of the resting time, cell capacity of the first cycle increases by up to 10%, and becomes stable with resting time of 4 days or more. It is also found that the capacity fade is slower with longer resting time and this capacity fade tends to stabilize with resting time of 4 days or more. This very likely reveals the SEI formation process, indicating the full development of SEI on SLMP-lithiated graphite with long enough resting time. Development of such SEI (using SLMP method) is equivalent to the slow formation protocols used in regular lithium ion cells.

A new conductive polymer binder is developed for solving the long-standing volume change issue for high capacity materials Silicon in lithium battery electrodes. Through combination of synthesis modification, theoretical calculations, spectroscopy, advanced diagnostics and device testing techniques the electronic structure and polarity of the polymer was tailored favorably to enable maximum in situ lithium doping. The composite electrodes based on Si particles and this polymer, without any conductive additives, exhibit so far the best performance in several critical aspects for commercial applications, including high capacity, stable cycling, low over potential between charge and discharge, and good rate performance.

Rechargeable lithium ion battery (LIB) is one of the most technologically important forms of energy storage and is used widely in portable electronic devices. The emergence of hybrid plug-in electric vehicles and electrical vehicles as alternative to conventional vehicles powered by internal combustion engine is poised to take off as an important measure to counter the uncertainty in crude oil price. Hence, to meet the stringent battery requirements of electric vehicles, LIBs with higher capacity as well as fast charging capability need to be developed. Among the anode materials, alloying-typed materials offer the highest volumetric and gravimetric capacities, placing them among the most appealing and competitive candidate materials for vehicular applications. The trade off for enhanced charge storage lies in the unavoidable and extremely large volume variation that occurs when lithium atoms are being inserted/removed from the structure during the alloying/dealloying process. Consequently, this leads to rapid deterioration of the morphology of the active materials (particle isolation, pulverization), and limits the practical lifetime of these electrodes. Group IV elements (Si, Ge, Sn) are among the most widely studied alloying-typed anode materials, and the general approach is to form intermetallic compounds or composites to reduce the extent of volume variation. In this work, a novel class of high capacity Sn-Ge materials were fabricated via a rapid solidification and high throughput melt spinning (MS) process that was developed. These materials demonstrate enhanced lithium storage properties, attaining high and stable capacity of ~ 1000 mAhg-1 over 60 cycles, at a current density of 125 mAhg-1. Even at a very high current density of 5000 mAg-1, reversible capacity of 500 mAhg-1 is achieved, giving this novel material a fast charging time of 12 mins, surpassing the performance of conventional LIB anode materials. The capability to deliver high capacity at high C-rates makes Sn-Ge one of the most favorable candidates for fast charge/discharge applications. The various factors that contribute to the improved lithium storage properties will also be discussed.

Development of new anode materials for Li ion batteries has been a subject of many studies. Special attention was devoted to studies of Si-based anode materials (from bulk to nanostructured Si), as it has one of the best known capacities for Li storage.1 Despite this, the potential of Si materials for other types of batteries - such as Na or Mg ion batteries which are most promising for bulk storage2 - is largely unstudied. Here, we present a computational investigation of the behaviour of Li, Mg, and Na atoms in Si-based materials. At low concentrations, the impurities act as interstitial defects and locate at tetragonal (T) sites of bulk Si matrix. Analysis of the electron charge densities suggests that the chemical interactions between the matrix and different doping atoms vary. Because Li has the lowest electronegativity, Li-Si interaction has larger ionicity compared to interactions of Na/Mg with the Si.
To further understand and predict the charge/discharge performance of the Si electrode, we also studied the diffusion behaviour of different dopants in Si. Single dopant atoms migrate between two T sites via the hexagonal interstitial site. Migration barriers (MBs) are ~0.5 eV larger for Na and Mg than for Li. However, inter-dopant interactions can reduce the absolute values for migration barriers by up to 30%. We provide ab initio evidence that charge/discharge performance are improved at finite concentration. Compared to Li, Na and Mg dopants are still expected to have lower diffusivity but the beneficial effect of final concentration is also more important for these two dopants.
Finally, we discuss ongoing work on the insertion of the doping atoms in Si nanosheets to explain the role of surface orientation and nanosize effects on the charge/discharge rates.
References:
1 H. Li, Z. X. Wang, L. Q. Chen, and X. J. Huang, Adv. Mater. 21 (45), 4593 (2009).
2 Veronica Palomares, Paula Serras, Irune Villaluenga, Karina B. Hueso, Javier Carretero-Gonzalez, and Teofilo Rojo, Energy Environ. Sci. 5 (3), 5884 (2012).

A concept of direct rechargeable liquid fuel cell assumes the reversible, electrochemical, oxidative dehydrogenation of organic fuels in a PEM fuel cell.¹ Hydrogen is extracted from saturated organic compounds at the fuel cell anode as protons and electrons (‘virtual hydrogen storage&’), not as hydrogen gas as was proposed earlier.² In combination with a common air cathode, the fuel cell produces a hydrogen depleted organic compounds, water and power (Reaction 1). To recharge the proposed regenerative fuel cell, the reactions can be reversed and the hydrogen depleted organic liquid is rehydrogenated electrochemically, or the spent fuel can be rapidly replaced with the hydrogen rich form at a refueling station. The use of energy dense liquid instead of H₂ alleviates the hydrogen economy problems associated with hydrogen gas (safety, transportation, and infrastructure).
LH_n + n/2 O₂ harr; L + n/2 H₂O (1)
The theoretical cell potential is defined by the free energy of the oxidative dehydrogenation reaction (1) and has to be maximized. To make the direct organic fuel cell practical, it is also necessary to minimize the fuel oxidation and product reduction overpotentials and prevent the fuel crossover. Therefore, three components are critical for realization of the proposed concept: organic fuel, electrocatalyst and a compatible PEM. The study of these system components and major fundamental challenges in electrocatalysis and selective transport phenomena is the focus of a DOE Energy Frontier Research Center led by GE Global Research.
The choice of liquid organic fuel defines the selection of an electrocatalyst and a PEM. Main criteria for practical and model fuels will be discussed, e.g. theoretical cell potential and energy density, reversibility of dehydrogenation and hydrogenation reactions, compatibility with PEMs, and safety. Preliminary results based on thermodynamic data, electrochemical study and computation will be presented for several classes of fuels.
Acknowledgment: This work was supported as part of the Center for Electrocatalysis, Transport Phenomena, and Materials (CETM) for Innovative Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC00001055.
1. a) Soloveichik, G. L.; Lemmon, J. P.; Zhao, J.-C. Method and apparatus for electrochemical energy conversion. US Pat. App. 20080248339, 2008; b) Crabtree, R. H., Hydrogen Storage in Liquid Organic Heterocycles. Energy & Environ. Sci. 2008, (1), 134.
2. Pez, G. P.; Scott, A. R.; Cooper, A. C.; Cheng, H. Hydrogen storage by reversible hydrogenation of pi-conjugated substrates. US Patent 7429372, 2008.

This presentation describes current status of the advanced redox flow battery research being performed at Pacific Northwest National Laboratory for the U.S. Department of Energy&’s Energy Storage Systems Program.1 Recent progress in the research and development of both aqueous and nonaqueous redox flow battery will be reported. The evaluation and optimization of single cell components for the two advanced redox flow battery electrolyte chemistries recently invented, the all vanadium (V) mixed acid and V-Fe mixed acid solutions, will be reported. Recent development of low-cost chemically stable vanadium redox flow battery separator/membrane will be presented. Varied electrochemical, chemical and physical evaluations were carried out to assist the component screening and optimization. Capacity decay causes and remediation methods for both the all vanadium redox flow and the Fe/V battery will be discussed, which allow us to optimize the related cell operation parameters and continuously operate the system for long-term stability.2 In addition, the development of metal-organic hybrid nonaqueous redox flow battery system will be discussed.3
Reference
1. W. Wang, Q. Luo, B. Li, X. Wei, L. Li and Z. Yang, Advanced Functional Materials, 2012, DOI:10.1002/adfm.201200694.
2. Q. Luo, L. Li, W. Wang, Z. Nie, X. Wei, B. Li, B. Chen, Z. Yang and V. Sprenkle, Submited, 2012.
3. W. Wang, W. Xu, L. Cosimbescu, D. Choi, L. Li and Z. Yang, Chem Commun, 2012, 48, 6669-6671.

Flow batteries are a potentially important technology for grid-scale electrical energy storage in the face of rising electricity production from intermittent renewables like wind and solar. Many chemistries and configurations could be used in the operation of a flow battery, and this presentation will focus on some that we find particularly promising.
We have developed novel alloy oxide electrocatalysts that have permitted the development of a hydrogen-chlorine flow battery with power densities exceeding 1 W/cm2 with a precious metal loading of about 0.1 mg/cm2. The cell exhibits virtually no activation loss, allowing for very high efficiency operation. The effects of varying operating parameters and cell design will be discussed, along with substantive comparisons to a quantitative model of this device.
Alternate chemistries, including the use of small organic molecules in a flow battery setup, may be discussed, highlighting some promising preliminary results from our lab. The advantages of using such compounds will be shown.

Redox flow batteries (RFBs), as one of the most promising electrical energy storage systems, provide an alternative solution to the problems of balancing power generation and consumption. RFBs are designed to convert and store electrical energy into chemical energy and release it in a controlled fashion when required. Of them, all vanadium system (VRBs), utilizing vanadium-containing chemicals as positive V(IV)/V(V) and negative V(II)/V(III) electrolytes, is one of the most promising redox systems due to its high efficiency.[1] Especially, recently invented mix-acid based all vanadium system by Li and co-workers[2] at PNNL largely improved the energy density and temperature stability window of vanadium electrolytes.. In addition to the improvement of energy density, another way to effectively reduce the VRB cost is to increase the current density, which directly leads to a smaller stack size, therefore dramatically reduce the cost. Here we report a catalyst-modified graphite felt (GF) as VRB negative electrode with significantly improved energy efficiency (EE) especially at high current density. It is shown that the modified GF electrode greatly improved the electrochemical activity of V(II)/V(III) redox couple, leading to the large reduction of overpotential. Consequently, the EE value reached 78% for the electrolytes with the optimized amount of catalyst at the current density of 150 mA/cm2, which increased by 12 % as compared with that without an electrocatalyst. These results suggest catalyst modification of GF surface is a promising route to improve the energy efficiency of VRBs especially under high- current-density operation.
References
[1] Wang, W.; Luo, Q.; Li, B.; Wei, X.; Li, L.; Yang, Z. Advanced Functional Materials 2012, DOI:10.1002/adfm.201200694.
[2] Li, L.; Kim, S.; Wang, W.; Vijayakumar, M.; Nie, Z.; Chen, B.; Zhang, J.; Xia, G.; Hu, J.; Graff, G.; Liu, J.; Yang, Z. Advanced Energy Materials 2011, 1, 394.

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. Unlike many other types of primary batteries, alkaline cells can theoretically be recharged. The low cost per kilowatt-hour of alkaline cells makes them potentially ideal for applications such as wind or solar energy storage or reducing energy demands during peak consumption. However, one problem that reduces the effectiveness of rechargeable alkaline batteries is the phase transformation occurring in MnO2 after reduction by more than one electron that converts it into the electrochemically inactive Mn3O4 phase. 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. In this presentation, we demonstrate a method of producing a manganese oxide-carbon nanocomposite material via a one-step solution process that exhibits dramatically greater rechargeability than existing manganese dioxide materials produced via electrolytic methods.
Carbon black was added to a solution of barium permanganate, and then heated to 100 C in a reflux apparatus for several hours, until all of the permanganate had been consumed by the reaction. This formed a thin film of nanocrystalline and highly porous barium manganese oxide on the surface of the carbon black nanoparticles. The material was then mixed with a polystyrene binder and carbon black conductive additives and pasted into a nickel foam current collector. The material was tested against Ni metal and zinc counter electrodes in a potassium hydroxide electrolyte. These materials showed high cyclability for over 100 cycles, even with minimal or no capacity limits. The structure of the nanocomposite, as well as its reduction and oxidation behavior, have been studied, and will be further discussed in the presentation.

New types of energy storage are needed in conjunction with the deployment of solar, wind, and other volatile renewable energy sources and their integration with the electrical grid. No existing energy storage technology can provide the power, cycle life, and energy efficiency needed to respond to the costly short-term transients that arise from renewables and other aspects of grid operation.
Recently, we developed a family of open framework nanoparticle materials with the Prussian Blue crystal structure. This crystal structure is composed of a face-centered cubic framework of transition metal cations that are octahedrally coordinated to hexacyanometalate groups. Large interstitial “A Sites” within the structure can accommodate zeolitic water and hydrated alkali ions. This results in a general chemical formula of AxPR(CN)6*nH2O, where A is an alkali cation such as K+ or Na+, P is a transition metal cation such as Cu2+, Ni2+, Mn2+ or Fe3+, and R(CN)6 is a hexacyanometalate anion such as [Fe(CN)6] 3-, [Mn(CN)6] 3-, or [Cr(CN)6]3-. The Prussian Blue framework structure has wide channels between the A sites, allowing for rapid insertion and removal of Na+, K+, and other ions from aqueous solutions with little lattice strain. The result is an extremely stable electrode: over 40,000 deep discharge cycles were demonstrated in the case of the copper hexacyanoferrate (CuHCFe) [1]. In particular, the reaction potential of 0.95 V vs. SHE, room temperature synthesis, low cost and long cycle life make CuHCFe the perfect cathode candidate in an aqueous electrolyte battery for grid-scale storage applications.
The CuHCFe cathode must be paired with an anode that has comparable cycle life and kinetics to avoid a substantial loss in performance for the full battery. The activated charcoal used in commercial ultracapacitors has these properties, and we recently showed that it could be successfully combined with the CuHCFe cathode in an asymmetric cell (2). However, the low capacity of capacitive electrodes such as activated charcoal severely limited the specific energy of this cell. Prussian Blue analogues that use hexacyanometallates of Mn, Cr, Co, and Ru, among others, have long been studied for their magnetic and structural properties; however, their electrochemical properties have received very little attention.
In this work, we introduce a new symmetric battery that uses Prussian Blue analogues for both its cathode and anode. We demonstrate manganese hexacyanomanganate (MnHCMn) as anode material that have low reaction potentials around 0 V vs. SHE, and that when combined with cathodes such as CuHCFe, yield useful full cell voltages of around 1 V. The electrodes in this battery are synthesized in bulk, and when operated in an appropriate aqueous electrolyte, show extremely long cycle life, fast kinetics, and high efficiency.
References
[1] C. D. Wessells et.al., Nat Commun 2, 550 (2011)
[2] M. Pasta et.al., Nat Commun 3, 1149 (2012)

MnO2 is perhaps the most heavily studied electrode material in all kinds of batteries. Various polymorphs of MnO2 provide a plentiful library of interesting chemistries. In the study of Li-ion batteries (LIB) , the electrochemical performance of MnO2 as LIB cathode highly depends on its crystal structure. In this presentation, we combine the experimental and computational approach to explore the feasibility of using different MnO2 polymorphs as high capacity Mg ion battery (MIB) cathodes. The redox reaction caused by the insertion of Mg ions, the diffusion of Mg and the structural deformation are systematically studied for different MnO2 polymorphs. Two key properties are found to limit their electrochemical performances: the structural stability that accommodates the insertion and removal of divalent Mg ions, and Mg mobility that limits the rate capability. For example, spinel MnO2 suffers from the sluggish Mg mobility, especially at high Mg concentrations. On the other hand, alpha-MnO2 suffers from severe structural deformation during the operation. Based on these results, we propose a new candidate as Mg battery cathode. Theoretical calculations show that the mobility of Mg ions in this new material is comparable to that of Li in the spinel phase. The structural deformation of this material during the insertion and removal of Mg is also analyzed and compared to alpha-MnO2. These results not only help the study of MnO2 as Mg battery cathode, but also provide insights for the design of future cathode materials in Mg battery.

Grid-scale energy storage has become increasingly important because of the use of intermittent sources of renewable energy in the power grid. Copper and nickel hexacyanoferrate (CuHCF and NiHCF) have previously shown promising cycle life, high rate performance, and efficiency as cathode materials in aqueous batteries. These hexacyanoferrate materials possess a unique open framework structure that allows for the reversible intercalation of a wide variety of multivalent cations, including many alkaline earth, rare earth, and transition metal cations. The materials demonstrate unprecedented high rate capacity and cycle life for multivalent ion intercalation. CuHCF retains over 80% of theoretical capacity at a charge rate of 10C and over 80% of initial capacity after 2000 cycles with several divalent electrolytes. In addition, the flexibility in electrolyte species for these electrodes opens up new design strategies for the anode. Several transition metal anodes, including lead, copper, and zinc, have shown promising full cell performance when cycled with CuHCF.

An attractive path to increase energy storage capacities, lower the material costs, and improve operation safety involves the use of multi-valent elements, such as magnesium (Mg) and aluminum (Al), etc. In the case of magnesium, the low equivalent weight 12g/F (Faraday) compared to sodium (23g/F) and its low cost, 24x less expensive than metallic lithium, along with its safety characteristics is particularly attractive as a candidate for cost sensitive energy storage applications. No dendritic formation was reported on Mg metal anode, which is critical for applying metal anode instead of metal carbon composites. In this presentation, we will report rechargeable Mg ion battery with new electrolyte consists of magnesium salts and organic solvents, which can facilitate the electrochemical reversibility of magnesium and shows a superior electrochemical window and chemical stability for various cathode materials.

The introduction of electric vehicles (EVs) and plug-in hybrid vehicles (PHVs) which utilize alternative technologies (e.g. batteries) to traditional combustion engines is slowly revolutionizing the automobile industry. Although batteries are a cleaner alternative to fossil fuels, concerns over their long range performance in automobiles have hampered their widespread use.¹ Hence, high performance battery systems which meet automobile energy use, and especially space requirements, remain paramount in establishing the next generation of EVs and PHVs.^2-3
In this regard, multivalent battery systems like rechargeable magnesium (Mg) batteries are garnering more interest as candidate post-lithium (Li) battery systems.⁴ Mg, being divalent and denser, is theoretically capable of delivering a higher volumetric energy-density (3833 mAh cm^-3) than Li (2061 mAh cm^-3).^1-3 In order to be competitive with current Li-ion systems, high voltage and high capacity Mg systems must be developed. To date, various organohaloaluminates have been utilized as alternative electrolytes for Mg systems, due to the incompatibility of conventional battery electrolytes (TFSI^-, ClO₄^-, PF₆^-) with a Mg metal anode.^5-7 However, recent reports have shown that these organohaloaluminate electrolytes provide a limited operating voltage window when tested against typical battery current collectors.⁸
It is nonetheless possible to develop high voltage Mg systems via the use of conventional battery electrolytes if the anode system is changed from a Mg metal anode to a Mg-ion insertion-type anode, enabling Mg-ion transport through the anode/electrolyte interface. Here, we report the use of such insertion-type, high energy-density anodes (e.g. Bi, Sn) for rechargeable Mg-ion batteries, using conventional battery electrolytes. The fabrication, characterization and electrochemical analysis of these anodes, including full-cell testing, will be presented and discussed.
References:
1 J.-M. Tarascon and M. Armand, Nature, 2001, 414, 359.
2 P. Novak, R. Imhof and O. Haas, Electrochim. Acta, 1999, 45, 351.
3 T. S. Arthur, N. Singh and M. Matsui, Electrochem. Commun., 2012, 16, 103.
4 D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich and E. Levi, Nature, 2000, 407, 724.
5 D. Aurbach, J. Weissman, Y. Gofer and E. Levi, Chem. Rec., 2003, 3, 61.
6 Z. Lu, A. Schechter, M. Moshkovich and D. Aurbach, J. Electroanal. Chem., 1999, 466, 203.
7 T. D. Gregory, R. J. Hoffman and R. C. Winterton, J. Electrochem. Soc., 1990, 137, 775.
8 J. Muldoon, C. B. Bucur, A. G. Oliver, T. Sugimoto, M. Matsui, H. S. Kim, G. D. Allred, J. Zajicek and Y. Kotani, Energy Environ. Sci., 2012, 5, 5941.

We describe a Li anode/organic electrolyte/nanostructured carbon-sulfur composite cathode Li-S battery containing a micrometer scale thick V₂O₅ lithium ion-conducting layer that physically separates the anode and cathode electrolytes. Mechanical integrity of the Li⁺ conducting layer is achieved by coating the V₂O₅ onto a commercial polypropylene separator. Furthermore, the isolated cathode electrolyte is optimized by the intentional addition of Li₂S_n to suppress redistribution of sulfur within the carbon-sulfur composite. This divided cell architecture eliminates the interaction of soluble polysulfide with the Li anode, which is ubiquitous in liquid electrolyte Li-S batteries. A 2 cm x 2 cm laboratory pouch cell of this design has been cycled >230 times over ~1 year without noticeable degradation at capacities of 1025 mAh/g-sulfur.

Lithium ion batteries (LIBs) are getting to be the foremost representative power sources for clean vehicles such as hybrid vehicle (HV), plug-in hybrid vehicle (PHV) and electric vehicle (EV) due to their high energy density. However since a battery system with even higher energy density is required for the long-range PHV or EV applications, post lithium ion batteries (PLIB) such as Li-sulfur battery or Li-air battery have been getting more attention and studied in recent years. Rechargeable magnesium battery can also be a candidate for the PLIB due to the nature abundance of magnesium and no dendrite formation when using as anode1. In addition, magnesium-metal electrode is expected to have high energy density, due to its divalent electrons transformation. However, there is no much progress on cathode side since the innovation of Chevrel phase such as MgMo3S4 2. The difficulty lies in the strong polarization character of the small and divalent Mg2+ and consequently the intercalation and diffusion of Mg2+ ions is somewhat difficult and complicate3.
We recently reported α-MnO2 as a Mg battery cathode with an initial capacity of 282.7 mAh/g. The reversibility has been proved by X-ray photoelectron spectroscopy (XPS) and X-ray adsorption spectroscopy (XAS) 4. However, the reaction mechanism has not been clear. To shed light on this problem, it is critical to investigate how the physical factors, such as morphology, type of stabilized ions in the (2x2) channels, particle size, affect discharge and charge capacities corresponding to magnesiation and demagnesiation, respectively. In this presentation, various kinds of α-MnO2 cathode materials have been synthesized and their electrochemical behaviors have been systematically studied. The key factors which control the capacity and cycling performance of this cathode will be discussed.
References:
1. M. Matsui, J. Power Sources, 2011,196, 7048
2. D. Aurbach, et al, Nature, 2000,407, 724
3. E. Levi, et al J Electroceram., 2009, 22, 13
4. R. Zhang, et al Electrochem. Commun., 2012, 23,110

Electrochemical double layer capacitors (supercapacitors) store energy via selective electrosorption of ions on the surface of highly porous carbon electrodes and are widely used for applications that require high power densities and charge/discharge rates. While electrodes made from carbide-derived carbons (CDCs) demonstrate exceptional performance due to high surface areas, low impurity levels, and optimized porosity for specific electrolytes, they contain numerous surface functional groups and a disordered carbon structure, limiting the operating potential window and rate handling ability. In our study, various CDCs were subjected to vacuum annealing at 700-1400°C to remove functional groups from the surfaces and increase the graphitic nature of carbon. The resulting material, while showcasing more prominent sp² ordering and conductivity, increased its surface area and retained a tight pore size distribution customized for high-performance organic electrolytes and ionic liquids. Surface composition analysis revealed fewer functional groups and a more stable carbon surface after annealing, which translated into increased hydrophobicity. Electrochemical testing using 1.5 M tetraethylammonium tetrafluoroborate in acetonitrile demonstrated fewer faradic reactions and improved rate handling as a result of increased conductivity. Voltage-dependent capacitance was observed for annealed materials, indicating fewer resistance losses and possible improved charge storage at higher applied potentials. The materials produced using this technique are promising candidates for the next generation of supercapacitors.

Today DC bus capacitors are currently the largest and the least reliable component of fuel cell and hybrid electric vehicle (HEV) or electric vehicle (EV) inverters. Capacitors represent up to 23% of both inverter weight and inverter cost and up to 35-40% of the inverter volume. In addition, current thin polymer film capacitors have a ceiling operation temperature of 105 °C. Capacitors for use in future HEVs inverters will be required to operate at 140 °C and 450V with a volume target of 0.6 L. Recently we have identified an inexpensive dielectric material based on a copolymer of N-Phenyl-7-oxanorbornene (S-POW) for use as a high temperature dielectric. Thin film capacitors fabricated with S-POW have met the 2015 DOE OVT operating parameters for future HEVs. This inexpensive dielectric material has a relatively high energy density and high glass transition temperature, which ensures a high operating temperature. In order to improve the processability of the dielectric materials we have begun to evaluate the use of plasticizers including several terathane polymers and two trimellitates. Complete electrical and mechanical characterization of copolymers containing loading levels of 5%, 12%, and 20% (w/w) of each plasticizers will be discussed.
Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy&’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

The largest and least reliable component of hybrid electric vehicles (HEV) or electric vehicles (EV) today is the DC bus capacitor located in the vehicle&’s inverter. Capacitors represent up to 35-40% of the inverter volume and 23% of both inverter weight and inverter cost. In addition, current thin polymer film capacitors have a ceiling operation temperature of 105°C. Capacitors for use in future HEV and EV inverters will be required to operate at 140°C and 450V with a target volume of 0.6 L. Recently we have identified an inexpensive dielectric material based on a copolymer of N-phenyl-7-oxanorbornene (S-POW) for use as a high temperature dielectric. Thin film capacitors fabricated with S-POW have met many of the 2015 DOE OVT operating parameters for future HEVs. This inexpensive dielectric material has a relatively high glass transition temperature and high energy density, which enables a high operating temperature. In order to increase the energy density of the capacitors we have begun to evaluate the use of additives including 2- and 4-nitrodiphenylamine, 2-nitroaniline and 4-nitrophenol. Complete electrical and mechanical characterization of copolymers containing loading levels of 0.1%, 0.2%, 0.5%, 1% and 5% (w/w) of each additive will be discussed. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

The rapid development of portable electronics and electric vehicles has lead to a great demand for high-energy, high-power, and long-cycle-life lithium ion batteries. Three-dimensional (3D) network is considered as a superior structure for lithium ion battery electrodes to enhance both ion and electron transport kinetics to meet these requirements. In this work, we develop lithium ion battery anodes based on 3D nanoporous carbon network. The 3D carbon network is fabricated through chemical vapor deposition (CVD) of carbon on the 3D PAA template. The 3D carbon network consists of parallel nanotubes with diameter ~ 200nm connected to one another by branch tubes with diameter ~ 80 nm. This self-supported 3D nano-porous carbon network structure is used as a framework in the electrode by coating active materials, TiO2, on it through atomic layer deposition (ALD). In this 3D nanoporous composite structure, the parallel tubes and the gaps among them serve as channels of fast Li ion transport for high rate electrodes. Simultaneously, the electrons generated in the electrodes are effectively transported through the 3D carbon network to the current collector and thus electronically ensure the extremely high rate performance. In addition, the 3D carbon network, acting as a buffering matrix, accommodates the large volume change of the active material and ensures long cycle life of the anode.

Si based anode materials have attracted much interests for Li-ion battery applications because of its known advantages such as high energy density, high operating voltage, and low cost and toxicity. Despite of these attractive features, Si based anode materials often shows structure failure caused by rapid volume expansion during the battery charging process. It is therefore necessary to understand the kinetics of Li diffusion and the evolution of structures during de/lithiation process. To achieve this goal, we use first principle method to study the kinetics of Li diffusion in Si crystal, and find that the rate-limiting step is the initial lithiation of Si anode. We also use first principle method to calculate the binding energies of Li, Si, and Li-Si alloy crystals with various solid condensed phases. With these inputs from first principle data, we developed Li-Si Reaxff potential to run MD simulations for larger system at longer time scales, which is usually impossible to do with first principle methods. It is promising that this potential may provide more insights about structural evolution during the de/lithiation process in Si anode materials.

The phase behaviour of K₃H(SeO₄)₂ (TKHSe) above room temperature has been studied by differential scanning calorimetric (DSC), thermogravimetric analysis (TGA), simultaneous thermogravimetric and differential scanning calorimetric analysis (SDT), impedance spectroscopy (IS), and X-ray powder diffraction (PXRD). According to previous reports, around 388 K (114.85 ^#9675;C), TKHSe presents a superionic phase transition produced by a structural phase transition, with values of the dc-conductivity above the transition temperature greater than 10^-3 Omega;^-l cm^-l . Looking for new evidences about this process, additional and alternative measurements were performed on well characterized TKHSe samples, reporting new findings which to our knowledge have not been previously reported in literature. The results show a process that start at 388 K which is accompanied by a slow thermal dehydration, at about the superionic phase transition. We propose that the K₃H(SeO₄)₂ undergoes a phase transition and simultaneously a decomposition process. Moreover, the observed decrease of the magnitude of conductivity on successive thermal runs is a consequence of decomposition that starts at the surface of the TKHSe grains, but the jump in conductivity is only a consequence of the order-disorder transition in the TKHSe phase that remains inside the grains.

Electrically conductive metal-oxide aerogels are highly porous three-dimensional architectures that contain a network of solid nanoparticles suspended through void space. Such materials have high surface areas (typically 100-600 m2/g) and a large electrode/electrolyte interface beneficial for the kinetics of electron/cation insertion reactions and the magnitude of electrochemical charge stored thereby.1 Previously Long et al. demonstrated facile processing routes for downselecting nanocrystalline iron oxide (FeOx) phases from a parent FeOx aerogel.2 We are now extending this work to explore the ion-insertion properties of certain FeOx phases derived from a sol-gel approach (i.e., Fe3O4, γ-Fe2O3) and optimizing the performance of such materials through the deliberate incorporation of structural defects. Morphological and structural analysis of the defect ferrite products was carried out using scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Electrochemical properties or FeOx aerogels, as incorporated into conventional powder-composite electrodes and tested in Li+-containing nonaqueous electrolytes, were assessed using electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic cycling. We find that capacity and cycling stability for Li-ion insertion are optimized by blending ordered and disordered structures, achieved by controlled temperature/atmosphere-processing of the FeOx nanoarchitecture.

Li_1+xMn_2-xO₄ has been intensively researched as one of the most potential cathode materials for Li-ion batteries due to its inexpensiveness, environmental merit, and easy preparation [1,2]. However, this material suffers from cycle life issues due to the detrimental reaction between the surface of materials and the electrolyte. Particularly, the dissolution of manganese can be accelerated as the presence of acidic impurities in the electrolyte through the following reaction[3]:
2Mn³⁺_solid → Mn²⁺_solution + Mn⁴⁺_solid.
Besides the loss of material, dissolved manganese drifts from cathode to the anode side, where it can be deposited, thereby degrading cell performance. Recent research efforts have suggested surface passivation with inactive phases such as Al₂O₃ as a solution [4]. Previously, surface passivation has been done through a post-synthesis procedure on already highly agglomerated secondary particles. This prohibits further optimization of the passivation process, thus leading to inhomogeneity that still allows permeation of the electrolyte. In this study, core-shell structures are investigated at the primary particle level. The goal was to produce passivated particles with higher stability against the reaction with electrolyte while maintaining electrochemical activities. Their electrochemical properties have been studied using coin type half cells as different postsynthesis treatments.
[1] E. Hosono , T. Kudo , I. Honma , H. Matsuda, H. Zhou, NanoLett., 2009, 9(3), 1045.
[2] K. M. Shaju, P. G. Bruce, Chem. Mater., 2008, 20(17), 5557.
[3] J. C. Hunter, J. SolidStateChem., 1981, 39, 142.
[4] Y.-S. Lee, N. Kumada, M. Yoshio, J. PowerSource, 2001, 96, 376.

A significant progress in the development and deployment of Ultracapacitors (UCs) has been witnessed, since the first patent on double layer capacitor [1]-[2]-[3]. Nanostructured materials have attracted grate attention in recent years. An emerging material for UC electrodes, Carbon Nano-Onion (CNO), has been synthesized and characterized. CNO has shown promising high specific power, good energy density, and elevated cycling capability [4]-[5]-[6]. In [7], an equivalent circuit for CNOs-carbon nanotube UCs is presented; but an accurate equivalent circuit for CNO UCs has not yet been developed.
The object of this research is to study the behavior of CNOs material from an electrochemical point of view and develop the first accurate electric equivalent circuit model for a CNOs UC for grid energy storage. The impedance spectra were studied at different temperatures and bias voltages. It was suggested that the impedance spectra of the CNOs UC were accurately modeled by a modify Randles equivalents circuit with a dynamic assigning of the constant phase element coefficients.
Reference:
[1] Miller, J. Battery and Energy storage technology, Autumn 2007, 61-68.
[2] Simon, P.; Gogotsi, Y. Nature Materials 2008, 7, 845-854.
[3] Becker, H. L.; Ferry, V. U.S. Patent No. 2,800,616 (7/23/57), 1957.
[4] A.S. Rettenbacher, B. Elliott, J.S. Hudson, A. Amirkhanian, and L. Echegoyen, "Preparation and functionalization of multilayer fullerenes (Carbon Nano-Onions)," Chemistry-A European Journal, vol. 12, no. 2, pp. 376-387, Dec. 2005.
[5] D. Pech, M. Brunet, H. Durou, P. Huang, V. Mochalin, Y. Gogotsi, P. L. Taberna and P. Simon, "Ultrahigh-power micrometre-sized supercapacitors based on onion-like carbon," Nature Nanotechnology, vol. 5, pp. 651-654, Jul. 2010.
[6] Y. Gao, Y. S. Zhou, J. B. Park, H. Wang, X. N. He, H. F. Luo, L. Jiang and Y. F. Lu, "Resonant excitation of precursor molecules in improving the particle crystallinity, growth rate and optical limiting performance ofb carbon nano-onions," Nanotechnology, vol. 22, no. 16, Mar. 2011.
[7] C. Huang, C. Hsu, P. Kuo, C. Hsieh, and H. Teng, "Mesoporous carbon spheres grafted with carbon nanofibers for high-rate electric double layer capacitors," Carbon, vol. 49, no. 3, pp. 895-903, Mar. 2011.
Biography:
Fabio Parigi received a M.Sc. in Mechanical Engineering from Politecnico di Milano, Milan, Italy, in 2005. In 2008 he joined the Electrical Engineering department at the University of Nebraska-Lincoln, Lincoln, NE, USA, where he is currently a Ph.D. candidate. His research interests include advanced materials such as carbon nano-tube and nano-onion for energy storage devices, modeling and characterization of ultracapacitors, hybrid vehicles, wind energy and smart grid.
* Correspondence should be address to Prof. Jerry L. Hudgins. Email: [email protected].

Olivine LiFePO4 is one of the most promising alternatives as cathode material for Li ion battery as it possesses several advantageous compared to conventional LiCoO2. It combines highly available and affordable materials with improved safety and reduced toxicity. Conversely, its low intrinsic electric and ionic conductivity leads to inferior rate performance thus hampering its broad utilization in Li-ion batteries. Nevertheless, a few ways were identified in view of enhancing the rate performance and conductivity of LiFePO4 such as minimizing the particle size, doping with Mn, Al, Ti and coating with conductive carbon layer. Towards this idea, we used a combined gas-phase and solid-state reaction enabling high production rates to synthesize Mn-doped LiFePO4 with varying amount of conductive carbon. From the XPS and XRD measurement, we found that the Mn-doped LiFePO4/C composites were free from impurities and exhibited a crystallite size of about 80 nm. To optimize the impact of conductive carbon on the electrical conductivity, its amount was varied from 2 to 8 wt% and its impacts towards the electrochemical performance was studied with electrochemical impedance spectroscopy, cyclic voltammetry and electrochemical cycling. We found that excess as well as too low amounts of carbon leads to poor performances as the pathways were blocked or the electric conductivities were poor while about 5 wt% of carbon were found to yield good electrochemical properties of more than 140 mAh/g even at high charge rates.

There is tremendous interest in developing low-temperature solvothermal methods for synthesizing high-energy battery electrodes at reduced cost. One of the key hurdles in using solution-based reactions is the difficulty in understanding the reaction pathway and thereby optimizing the reaction for obtaining desired phases and material properties. The ability to probe synthesis reactions in real time would reveal which intermediate phase form and when, and provide a better understanding of how temperature, pressure, time and the initial concentrations affect the reaction pathways. Ultimately, a better understanding of the correlation between synthesis conditions, crystallization processes, defect structure and properties would lead to rational design of advanced electrode materials. To this end, we developed specialized in situ reactors for investigating solvothermal synthesis reactions in real-time using synchrotron x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS). Based on the capillary reactor that was recently used to study the synthesis of LiFePO4 [1] at low temperature, we have developed a new generation of in-situ reactor suited for a variety of solvothemal reactions at higher temperatures and pressures. In this presentation, we will show our recent results on solvothermal synthesis of nanostructured CuxV2O5 (x<1) cathodes, with a reversible capacity as high as 260mAh/g, and in-situ studies of their phase transformations. Structural characterizations performed on the as-synthesized and lithiated materials reveal new insights into the lithium reaction mechanisms and the fundamental limits of the electrochemical performance.
[1] J. Chen, J. Bai, H. Chen, J. Graetz, The Journal of Physical Chemistry Letters 2 (2011) 1874-1878.
This work was supported by DOE-EERE under the Batteries for Advanced Transportation Technologies (BATT) Program, under Contract No. DE-AC02-98CH10886.

It is no doubt that rechargeable Li-ion batteries (LIBs) have been key components in the use of portable electronic devices, clean energy storage, hybrid electric vehicles and aerospace etc., due to their large energy density, high output voltage and long life spans. Generally, graphite is used as the anode material, in which lithium ions can intercalate in and out reversibly. However, it can hardly meet the demand of high energy density and high capacities from electronic devices nowadays because of its theoretical maximum capacity of 372 mAhg-1 associated with its maximum LiC6 stage. In terms of meeting the requirements of new generation anode materials for LIBs, metal oxide/sulfide-based anodes have been suggested as the most potential substitute for the state-of-the-art graphite anode to increase the battery capacity. Taking SnO2 (SnS2) as an example, recently, tin-based oxide/sulfide SnO2/SnS2 as anode materials of LIBs have be en widely investigated due to their high capacity. The electrochemical process for SnO2/SnS2 is expected to evolve by a first activation step and subsequent reversible electrochemical process, which is irreversible:
SnO2 (SnS2) + 4Li → 2Li2O (2Li2S) + Sn (discharge) (1)
Sn + 4.4 Li+ + 4.4e- harr; Li4.4Sn (→ discharge, larr; charge) (2)
However, SnO2/SnS2 suffers from a large volume change during lithium alloying/dialoging mainly due do a volume change up to 300% from Sn to Li4.4Sn, which jeopardizes the mechanical integrity of SnO2/SnS2 based electrodes. As a result, the materials become pulverized and the batteries using such materials face very rapid capacity fading during charge/discharge cycling. Thus, reducing the volume change and improving the cyclability have been the challenge in current study of SnO2/SnS2 materials for LIBs. Herein, we focus on designing and synthesizing micro-nano-structured metal oxide/sulfide as anode materials for LIBs. This micro-nano-structured metal oxide/sulfide will give their great advantages such as shorter Li+ transport lengths, large specific surface area, and fast kinetics. Particularly, the nanopores can optimize mechanical stress induced by the huge volume expansion and shrinkage of SnO2/SnS2 during Li+ insertion/extraction processes, thus preventing deterioration and preserving the integrity of the anodes. The micro-nano-structured architectures consist with nanoparticles, which are strongly in favor of excellent electrochemical performance and potential practical application.
References
[1] Dunn, B., Kamath H., et al. (2011). Science 334(6058): 928-935.
[2] Yu, F., Ge, S.G., et al. (2012). Current Inorganic Chemistry 2(2): 194-212.
[3] Yu, F., Zhang, J.J., et al. (2009). Journal of Materials Chemistry 19(48): 9121-9125.
[4] Yu, F., Zhang, J.J., et al. (2010). Journal of Power Sources 195(19): 6873-6878.
[5] An, Z. G., Zhang, J.J, Pan, S.L., Yu F. (2009). Journal of Physical Chemistry C 113(19): 8092-8096.

Single-Walled carbon nanotube (SWCNT) aerogels, produced by critical-point-drying of wet-gel precursors composed of individually dispersed nanotubes, exhibit unique properties such as high surface-area-to-volume, strength-to-weight ratios, and large porosity. These aerogels become elastic and fatigue resistant when coated with graphene nanoplates without degradation of surface-area-to-volume and porosity. The resulting graphene-coated aerogels are free-standing, binder-free, and can be scaled to thicknesses of more than 1 mm. Here we examine the capacitive behavior of these materials in a common ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. Electrochemical performance is assessed through cyclic voltammetry, galvanostatic cycling, and impedance spectroscopy. Results indicate stable capacitive behavior over 2000 cycles, as well as an impressive performance at high operation rates, due to their accessible pore networks, enhanced electronic and ionic conductivities. These materials can find applications in mechanically compressible and flexible supercapacitor devices with high power requirements.

Silicon monoxide (SiO) attracts a particular attention because of its improved cycling ability compared to the Si anode material for rechargeable lithium batteries. Earlier reported results showed that commercial SiO material provided specific discharge capacity around 600 mAh/g, which was still higher than that of currently used graphite anode. The reaction of SiO with lithium has been reported to form Li2O and lithium silicates in the course of initial lithiation, which behave as buffers accommodating the volume change in LixSi. Recent reports revealed that non-stoichiometric SiOx (x = 0.85 - 1.3) showed similar cycling behavior to SiO but performance significantly improved for the composite with carbon material. In order to improve low electronic conductivity and further accommodate volume change, a homogeneous delivery of carbon to SiOx (e.g., carbon coating or carbon composite) via solution-based synthesis seems to be essential. We report here a new solution-based synthetic method for carbon-coated SiOx materials using SiCl4, and characterization of material properties and electrochemical activity as an battery anode material.
Acknowledgments
This work was supported by the MEST & National Research Foundation of Korea through the Human Resource Training Project for Regional Innovation (2012026203).

The highly specific surface areas of 1D nanostructures offer surface sensitivity and reactivity, while the high aspect ratios allow reliable electrical contact and efficient transport of charge carriers. Consequently, they are expected to be useful as high-performance sensors, electrochemical cells, and solid-state energy conversion devices. Here we report a new facile route to convert solid ZnO nanorods to ultrafine nanotubes by thermal annealing of solid nanorods in ambient NH3. The unique characteristic of this approach allows achievement of ultrafine nanotubes with well-organized hexagonal nanowalls and sealed layouts. Time-dependent investigation of the evolution from solid nanorods to nanotubes illustrated the pore generation at the inside of nanorod bottoms and propagation to the top of nanorods. Based on this result, we proposed a transformation mechanism by hypothesizing the formation of a passivation layer (a few-atoms-thick Zn3N2) at the outer nanorod surface, which was further confirmed by XPS analysis. The core-etching process involved the elimination of defects in the as-synthesized ZnO, which eventually improved the luminescent properties of the ZnO nanotubes. Based on key features of these tubular structures, we assessed the electrochemical performance of the nanotubes as anode materials in lithium ion batteries, demonstrating significant improvements in cycling performance over counterparts made of solid nanostructures.

Using elemental sulfur and elemental lithium as cathode and anode, respectively, the lithium-sulfur (Li-S) battery represents the simplest battery chemistry for rechargeable batteries. In spite of the high theoretical energy density of 2600 Wh/kg, Li-S batteries suffer from poor cyclability. There are three key limitations for cycling Li-S batteries that must be overcome for practical Li-S batteries: (1) Sulfur is an electronic insulator. Its poor electronic conductivity leads to low utilization of active material in the electrode. This problem can be overcome by using high surface area carbon in the cathode. (2) The charge and discharge products of sulfur are poor ionic conductors. In order to make the sulfur cathode rechargeable, a liquid electrolyte that has a high solubility of polysulfides is required to overcome the poor ionic conductivities of solid sulfur species. As a result of the dissolution polysulfides in the liquid electrolyte, the diffusion of polysulfides from the cathode to the anode during the battery cycling leads to the corrosion of lithium anode and the loss of active sulfur materials. (3)The dendritic growth of lithium metal in liquid electrolytes and the ever growing of solid electrolyte interphase on the anode surface shorten the cycle-life of Li-S batteries and also cause safety concerns. Therefore, the poor cyclability of Li-S batteries is an intrinsic problem associated with the use of liquid electrolyte in the battery configuration.
In this presentation, we will show the recent development of all-solid Li-S batteries using Li-ion conducting sulfur-rich compounds. The all-solid battery configuration of Li-S batteries overcomes the intrinsic polysulfide shuttle phenomenon in conventional Li-S batteries. The use of a solid electrolyte also alleviates the concerns of cycling metallic lithium anode. A series of Li-ion conducting sulfur-rich compounds have been synthesized as the enabler of all-solid Li-S batteries. The relationship of molecular structure and ionic conductivity will be discussed in details. The charge/discharge mechanism of these sulfur-rich compounds has been identified as the reversible cleavage and formation of S-S bond of these sulfur-rich compounds. Highly reversible cycling of all-solid Li-S batteries was demonstrated at a cathode capacity over 1200 mAh/g (based on the mass of sulfur) after 300 cycles. Rate performance will be discussed in the presentation.
Acknowledgment:
This work was sponsored by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy through the Batteries for Vehicle Transportation Program. The synthesis of materials was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.

With a theoretical capacity of 1,166 mAhg-1, lithium sulfide (Li2S) has gaineded much attention as a promising cathode material for high energy lithium-sulfur batteries. However, the insulating nature of Li2S has prevented the achievement of high utilization (or high capacity) and good rate-capability. To address this issue, various efforts have been made to improve the contact between Li2S and electronic conductors such as carbon and metals. In literatures, however, relatively high capacity could only be achieved when the Li2S content is lower than 50 wt% while higher Li2S content often led to very low discharge capacity; therefore, the estimated cell specific energy values are often below 350 Whkg-1, which is insufficient to meet the ever-increasing requirements of newly emerging technologies such as electric vehicles.
We have developed a cost-effective way of preparing nanostructured Li2S/C composite cathodes by high-energy dry ball milling of commercially available micron-sized Li2S powders together with carbon additives. We also demonstrated a simple, but very effective electrochemical activation process allowing nearly full conversion of Li2S to sulfur. We have further improved the cycling stability of Li2S electrodes by adding multi-walled carbon nanotubes into the nanocomposites. With a very high specific capacity of 1,144 mAhg-1 (98% of the theoretical value) obtained at a high Li2S content (67.5 wt%), the estimated cell specific energy (including all components except cell-housing) was ~610 Whkg-1, which is much higher than those of current lithium-ion cells with oxide-based cathodes (120-200 Whkg-1). With further improvement in capacity retention, Li2S/C nanocomposite electrode may offer a significant opportunity toward the development of rechargeable batteries with much higher specific energy.

Although the lithium-sulfur (Li-S) battery offers the promise of a high energy density for electrical/hybrid electrical vehicles, it suffers from a fast capacity degradation that originated from the shuttle effect of polysulfide anions. We recently have demonstrated the use of polyaniline-sulfur (PANi-S) nanocomposites in mitigating the capacity fading. Here, we would like to present a novel but relatively simple one-pot in-situ chemical reaction strategy to synthesize conductive PANi-S composite nanowires. In the synthesis procedure, S was synthesized from the S-contained precursors while the aniline monomers polymerize in the same system. A more uniform dispersion of sulfur in the PANi hence is obtained. The detailed experimental tracking processes show that S forms before the polymerization of aniline. The SEM mapping shows that S nanoparticles mostly are encapsulated inside the polyaniline. The small amount of sulfur attached on the nanowire surfaces was removed through a low-temperature thermal treatment. These PANi-S based nanowires delivered a high initial reversible capacity of more than 1000 mAh-1 at 1C rate (after two cycles&’ activation process at a current rate of 0.02C) and a capacity retention of ~750 mAh g-1 (~75%) after 100 cycles. A good rate capability was also demonstrated at up to 10C rate. These results indicated that the as-synthesized PANi-S nanowires are promising cathode materials for recharge Li-S batteries.
Acknowledgement. This research was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, Division of Materials Sciences and Engineering, under Award KC020105-FWP12152 and the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory (PNNL). PNNL is a multiprogram national laboratory operated for DOE by Battelle under Contract DE—AC05-76RL01830.

Lithium sulfur batteries offer high theoretical specific energy of around 2600 Wh/kg, five times the existing LiCoO2/graphite system. Despite recent progress in addressing the various problems of sulfur cathodes, lithium sulfur batteries still exhibit significant capacity fading over cycling. Herein, we identify a new capacity fading mechanism of the sulfur cathodes, relating to LixS detachment from the carbon surface during the discharge process. This observation is confirmed by ex-situ transmission electron microscopy and ab initio calculations. We demonstrate that this capacity fading mechanism can be overcome by introducing amphiphilic polymers to modify the carbon surface, rendering strong interactions between the nonpolar carbon and the polar LixS clusters. The modified sulfur cathode show excellent cycling performance with specific capacity close to 1180 mAh/g at C/5 current rate. Capacity retention of 80% is achieved over 300 cycles at C/2.

In this presentation, we reported an intermediate-temperature (~150°C) sodium-sulfur (Na-S) battery. With a reduced operating temperature, this novel battery can potentially reduce the cost and safety issues associated with the conventional high-temperature (300~350°C) Na-S battery. A dense β"-Al2O3 solid membrane and tetraglyme were utilized as the electrolyte separator and catholyte solvent in this battery. Solubility tests indicated that cathode mixture of Na2S4 and S exhibited extremely high solubility in tetraglyme (e.g., > 4.1 M for Na2S4 + 4 S). CV scans of Na2S4 in tetraglyme revealed two pairs of redox couples with peaks at around 2.22 and 1.75 V, corresponding to the redox reactions of polysulfide species. The discharge/charge profiles of the Na-S battery showed a slope region and a plateau, indicating multiple steps and cell reactions. In-situ Raman measurements during battery operation suggested that polysulfide species were formed in the sequence of Na2S5 + S → Na2S5 + Na2S4 → Na2S4 + Na2S2 during discharge and in a reverse order during charge. This battery showed dramatic improvement in rate capacity and cycling stability over room-temperature Na-S batteries, which makes it attractive for renewable energy integration and other grid related applications.

Lithium-sulfur (Li-S) batteries have attracted increasing attention because of their high theoretical capacity, low cost and environmental friendliness. If Li2S is the final product, the maximum specific capacity and energy from Li-S batteries are 1675 mAh g-1 and 2650 Wh kg-1, respectively, which is three to five times higher than that of state-of-art lithium ion batteries. However, significant challenges have to be overcome prior to the practical application of Li-S batteries. The low electrical conductivity (5 x 10-30 S cm-1) of pure sulfur and the redox shuttle reaction of soluble polysulfides between sulfur electrode and lithium anode are the main reason for the low utilization rate of sulfur and poor electrochemical performance of Li-S battery, such as low Coulombic efficiency, high self-discharge rate and fast capacity fading. One of the most common approaches used to address the aforementioned hurdles in Li-S battery system is to impregnate sulfur into high surface area carbon to form S/C composites. However, during cycling, polysulfides still diffuse slowly to lithium anode where they are reduced to form lower order polysulfides and S-containing byproducts, which irreversibly precipitate on the lithium metal surface. The parasitic side reactions between polysulfides and lithium anode lead to serious lithium corrosion and rapid impedance increase, so continuous capacity fading is usually observed. ILs are well known to form a protecting layered surface, but so far there is no report on the interactions between ILs-derived SEI with polysulfide. Most of the works that adopted ILs in Li-S batteries are assigning the improved cycling performance to the reduced solubility of polysulfide in ILs, with a focus on the cathode side. In addition, because the passive film on Li anode formed from ILs has higher interfacial impedance than from those alkyl carbonates, the reported cycling performances of Li-S batteries in ILs are still unsatisfactory. The fundamental understanding on the roles that ILs plays in Li-S cells is required to further improve the performance of Li-S batteries.
In this work, ionic liquid N-methyl-N-butylpyrrolidinium bis(trifluoromethylsulfonyl)-imide (Py14TFSI) was used as a ‘co-solvent&’ of the electrolyte for Li-S batteries. The viscosity, ionic conductivity and cell performance were systemically investigated. The high impedance issues associated with pure ILs were minimized. More importantly, it was found that Py14TFSI favors the formation of high quality SEI layer that isolates Li metal from direct exposure to the soluble polysulfides in the electrolyte. The possible mechanism on the formation of SEI layer and their effect on the cycling behavior of Li-S batteries will be discussed.
Acknowledgement
This work was sponsored by PNNL Laboratory Directed Research and Development (LDRD) Project and the Office of Vehicle Technologies of the U.S. Department of Energy.

The principle of Li-S battery operation has been known for several decades; however, it has not been successfully commercialized yet, mainly due to fast capacity fading and very low efficiency. Although, the theoretical capacity of sulphur reduction into Li2S can exceed few times capacities of cathode materials in Li-ion batteries, the practical capacity of sulphur based composite cathode is much lower. Due to low intrinsic conductivity of sulphur, composite cathode is formed from high surface host matrix painted with thin layer of sulphur. Design of cathode composite play an important role. Recently, the introduction of a mesostructured cathode showed a positive impact on the Li-S cell electrochemical behaviour. However, this approach needs to be optimized. Optimisation of cathode architecture involves synthesis and tests of host matrix with different chemical properties. Chemical properties like change in the chemical composition, type of mesoporous material, influence of surface groups, doping elements and surface layers have an impact on the Li-S battery cycling properties (capacity and efficiency). Similarly, physicochemical properties (type of porosity, pore size, hydrophobicity, acidity) great influence Li-S battery behaviour which with a choice of optimized electrolyte and separator can lead to commercial application.
Some of above mentioned properties were detailed studied with a help of in-situ analytical tools developed in our laboratory. For instance in our recent work we showed that 4-electrode modified Swagelok cell can quantitatively determine small quantities of polysulphides in the separator and obtained results helped us to understand differences between different proposed architectures and chemical environments in the literature [1]. Further, this technique helped us to understand different behaviour of Li-S batteries if we used MOF or SiO2 as a substrate for sulphur impregnation [2]. Recently, we build up the in-situ cell for the polysulphides detection by using UV-Vis spectroscopy. Preliminary results pointed out differences in different chemical environments and polysulphides can be detected in the qualitative and the quantitative way. Finally, third approach used in our laboratory is study of S-k edge using synchrotron radiation.
Applicability of above mentioned techniques in the study of cathode composite will be discussed.
[1] R. Dominko, R. Demir-Cakan, M. Morcrette, J.-M. Tarascon, Electrochem. Comm., 13 (2011) 117-120.
[2] R. Demir-Cakan, hellip;, R. Dominko, M. Morcrette, J.-M. Tarascon, JACS, 113 (2011) 16154-16160.
This work has been supported by the EUROLIS project, grant agreement number 314515, funded by the EC Seventh Framework Programme theme FP7-2012-GC-MATERIALS.

Polymer material, as a rather new member in energy storage family, has attracted much attention and efforts because of its special property in many aspects comparing with other inorganic electrode material. In our recent study, different polymer material has been investigated and used for lithium secondary battery. Owned to the improved reaction mechanism and the optimized molecular structure, some of them can deliver an energy density comparable to the transient metal oxide and very stable cycling property. As the redox mechanism doesn&’t necessarily required the anticipation of Li+, in our latest research, the application of polymer material was extended to other energy storage system, such as Na or Mg battery. We used polymer material as the cathode for sodium secondary battery, it was found that they still show good capacity performance, cycling stability and rate capability. Besides, the suitable redox voltage of the polymer make it a very good candidate for the anode of aqueous Li-ion even Na-ion battery, thus-constructed battery shows a much higher capacity and energy density than the previous analogues, which imply its possible use in large-scale energy storage. On the other side, a new series of polymer with another reaction mechanism was proposed, it endows us to build Li-ion, Na-ion even whole organic battery with it. Generally, polymer electrode material, with diversified structure, has promising prospective in energy storage.

Li-O2 batteries are very promising energy storage systems with their two to three times higher theoretical specific energy (500 ~ 900 Wh/kgcell) than that of Li ion batteries. During the operation of Li-O2 batteries in non-aqueous electrolytes, the major discharge product, Li2O2, is deposited on the catalyst electrode upon discharge (noted as Oxygen reduction reaction, ORR) and decomposed back into Li+ and O2 on charge (noted as Oxygen evolution reaction, OER). Thus, the nanostructure of catalyst electrodes to provide sufficient area for storing discharge products, as well as highly efficient catalyst materials to facilitate ORR/OER, is a critical factor in designing high performance catalyst electrodes. Here, we exploited biomaterials, M13 viruses, as nanostructure templates to build high surface area catalyst nanowires by synthesizing various catalyst candidate materials, such as transition metal oxides (e.g. MnO2, Co3O4, NiO). The filamentous M13 virus has a high aspect ratio (~880 nm in length and ~6.5 nm in diameter), composed of 2,700 copies of p8 major coat protein encapsulating its single-stranded DNA. Through the interaction between the closely packed p8 coat proteins of M13 and metal ions in the solution, this biotemplate provides a simple and uniform method to synthesize various nanomaterials with the high aspect ratio. We investigated the Li-O2 battery performance dependence on different type of catalyst materials on the M13-confined structure. In addition, the M13 templated transition metal oxide nanowires have high surface areas and diverse pore structures, resulting in the improved discharge capacity as well as cyclability of Li-O2 batteries. We expect these biotemplated nanowires can be utilized to form multi-functional, cost effective nanocomposite structures to improve the practical limits of currently available Li-O2 batteries.

Today&’s lithium-ion batteries do not provide sufficient energy for an acceptable driving distance, which has limited public interest in electric vehicles, particularly for long distance travel. Lithium-air cells can be considered the ‘holy grail&’ of lithium batteries because they offer, in principle, a significantly superior theoretical gravimetric energy density approaching that of gasoline. It is generally accepted that the capacity of the non-aqueous Li-air battery is limited by its insoluble product, Li2O2, in oxygen reduction reaction (ORR). Instead of the homogenous thin film coverage, Mitchell et al. found that Li2O2 particles formed “toroid” structures on the carbon surface during discharge. However, the underlying mechanism of formation of such toroids is not well understood yet. In this work, we reported, for the first time, that the growth of Li2O2 toroids on oxygen cathode during discharge is through a self-assembly process, likely caused by the magnetic properties of the Li2O2 surface. In order to investigate the formation/decomposition and morphological evolution of Li2O2, non-aqueous Li-air cells were discharged and charged with different specific capacities (electrolyte: TEGDME/LiCF3SO3, current density: 100 mA/gcarbon, carbon loading per electrode: 0.8-1.2 mg). XRD results confirmed the formation and decomposition of Li2O2 upon discharge and charge, respectively. SEM observations showed clearly evidence that toroid Li2O2 particles (1~2 um) are formed at later discharge (higher capacity), which consists of numerous small Li2O2 nanoparticles (30-50 nm). Upon charging, most of these toroid particles disappeared, indicating that a reversible reaction (2Li+O2harr;Li2O2) occurs on the cathode. The cell impedance increases upon discharge and decreases upon charge, due to the poor electron conductivity of Li2O2. It should be also noted that the impedance cannot reach its origin value at the end of charge stage, and the difference became larger as the cell cycled at larger capacity. Our work could help to understand the morphological change of Li2O2 during the electrochemical cycle, and its effect on the impedance of the non-aqueous Li-air battery.

Li-O2 batteries have an ultra-high theoretical specific energy of about 5,2 kWh/kg when the weights of Li and oxygen are included and are expected to have a practical specific energy of around 800 Wh/kg. However, the development of rechargeable Li-air batteries faces significant challenges. The challenges for non-aqueous Li-air batteries include the selection of stable electrolyte, decrease of charge-discharge voltage hysteresis, design of cathode materials with high capacity and stability, protection of the Li anode, supply of moisture-free air, etc. It is well known that the discharge of a Li-O2 battery generates reactive oxygen species (O2-., LiO2, O22-, LiO2-, and Li2O2) on the surface of cathode. Reversibility of the rechargeable Li-O2 battery suffers from the side reactions between these reduced oxygen species. Therefore, the electrochemical stability of all the components in a Li-O2 battery, including electrolyte solvent, electrolyte salt, cathode material (typically carbon-based) and binder need to be re-evaluated in an oxygen-rich environment. During the last few years, significant efforts have been made in the development of stable electrolyte system while little attention has been paid to the stability of cathode material, especially binders. Binder is an essential component of air cathode, contributing 10-20 wt % of its total weight. Instability of binder may have significant effect on the cycling performance of the rechargeable Li-O2 battery. Fluorinated polymers such as PTFE and PVDF, which are commonly used for air electrodes, may not be stable to the reactive oxygen species generated during discharge.
In this work, we systematically investigated the effects of polymer binders with various chemical structures on the performance of Li-O2 batteries. The nature of the binder has significant effect on the surface area of carbon-based air electrode and its discharge capacity. The organic nature of a polymer binder determines its chemical and electrochemical stability against reduced oxygen species in oxygen atmosphere during the discharge and charge processes of a Li-O2 battery. The stability of such polymer binders against superoxide radical anion and Li2O2 will be discussed. Details of the investigation will be reported in the presentation.
Acknowledgement: This work was sponsored by PNNL Laboratory Directed Research and Development (LDRD) Project and the Office of Vehicle Technologies of the U.S. Department of Energy.

All-solid-state lithium secondary batteries with inorganic solid electrolyte attract much attention due to their high safety and reliability. Lithium Argyrodites Li6PS5X (X= Cl, Br) are one of the promising fast lithium ion conductors. Here we fabricated Li6PS5Br and Li6PS5Cl by high-energy mechanical milling and subsequent heat treatment. In-situ neutron diffraction monitoring of the phase formation process starting from the ball-milled precursor mixture revealed that an Argyrodite phase starts to form at low temperatures. Detailed Rietveld refinements of the in situ neutron and X-ray powder diffraction data show that the halide content, ordering and as a consequence the room temperature conductivity vary with the annealing temperature. Li6PS5Br samples were found to have ionic conductivities of 4 - 7 x 10-4 S/cm at room temperature and an activation energy of 0.12 eV. The high ionic conductivity and wide electrochemical window of 0- 5V make Li6PS5Br suitable as a solid electrolyte for all-solid-state batteries.
High capacity CuS composite cathode materials were prepared by mixing CuS, Li6PS5Br and carbon. All-solid-state lithium secondary batteries were assembled combining these CuS composite cathodes with Li6PS5Br as the solid electrolyte. Cyclic performance of all-solid state CuS/Li Argyrodite/Li and CuS/Li Argyrodite/In/Li batteries were tested at room temperature for up to 20 cycles, varying the content of carbon and Argyrodite phase in the composite cathode. An initial specific discharge capacity of 580 mAh/g was obtained in the cells with In/Li-anodes for composite cathodes with a weight ratio of CuS:Li6PS5Br:C = 40 : 56 : 4 at a current density of 11.2 mA/g. The intimate mixing of the components of the composite cathode by ball milling was found to be essential for ensuring high capacity and cycleability. Interfacial properties and phase transitions in the composite cathode were studied by electrochemical impedance spectroscopy and in-situ XRD. The variation of internal resistance during the presumed intercalation stage of the discharge process, i.e. the formation of LixCuS (x<1) reveals a two-stage process, implying an additional phase transition in the host structure before the conversion reaction starts.

Batteries based on lithium metal as a negative electrode could potentially bring about significant increases in energy density over current lithium-ion technologies. However, several concerns including stability, safety, and cycling efficiency have limited their development. The tendency of lithium metal to form mossy deposits or dendrites upon cell recharge leads to unsafe cells and short lifetimes. The use of solid state protective layers, which conduct ions but are electronically insulating, has been proposed as a potential solution to improve cycle life and enable its use with high energy air and sulfur cathodes.1 Several phases such as LISICON and La0.5Li0.5TiO3, among others, are being investigated for this purpose.2, 3 However, these compounds are not stable with respect to reduction by lithium and may form electronically conducting phases. To prevent this, an interlayer between the lithium electrode and solid ionic conductor is required. Phases that do not contain redox active transition metals are preferable to avoid the need for such an interlayer. We have recently studied the lithium ion-conducting phosphosilicate phase, Li3.4Si0.4P0.6O4, which meets this criterion. Li3.4Si0.4P0.6O4 forms a stable interface against lithium and has an ionic conductivity of 4.5×10-6 S/cm at room temperature.4 Similarly, garnet Li7La3Zr2O12 (LLZO) ceramic electrolyte appears to be stable against lithium metal electrodes, and has been reported to have high ionic conductivity (3×10-4 S/cm).5 Approaches for preparing thin, pinhole-free, dense layers are needed to ensure good current capability. The goal is to minimize the ceramic electrolyte impedance while preventing contact between the lithium metal anode and a liquid electrolyte, which wets the cathode.
To this end, we are investigating the fabrication of Li7La3Zr2O12 thin films using pulsed laser deposition (PLD). The films were characterization by employing X-ray diffraction, laser induced breakdown spectroscopy (LIBS), and electrochemical impedance spectroscopy. Here we will discuss the physical and electrochemical properties of Li7La3Zr2O12 films fabricated with different crystalline phase.
Acknowledgment
This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
References
[1] M-Y Chu, S. Visco, L.C. De Jonghe, U.S. Patent No. 6402795, 2004.
[2] H.S. Zhou, Y.G. Wang, Chem Commun 46 (2010) (34) 6305.
[3] Y. Inaguma, C. Liquan, M. Itoh, T. Nakamura, T. Uchida, H. Ikuta, M. Wakihara, Solid State Commun. 86 (1993) 689.
[4] “Effect of Lithium Borate Addition on the Physical and Electrochemical Properties of the Lithium Ion Conductor Li3.4Si0.4P0.6O4” L. Zhang, L. Cheng, J. Cabana, G. Chen, M. M. Doeff, and T. J. Richardson, Solid State Ionics 2012 (in press).
[5] R. Murugan, V. Thangadurai, and W. Weppner, Angew. Chem. Int. Ed., 46 (2007) 7778

There is a growing demand for high energy density storage systems which are essentially free of lithium. Fluoride ion batteries are capable of meeting this high energy density demands. The reaction of highly electronegative fluorine with metal leads to the formation of metal fluorides which are accompanied by large change in free energy and thus high voltage can be obtained. By choosing appropriate metal/metal fluorides, high voltage electrochemical cells can be built. Though few reports are known towards this end [1], such battery chemistry was largely overlooked in the last years. Recently we demonstrated reversible fluoride ion battery operates at 150 C [2]
The realization of successful fluoride ion battery largely dependent on the fluoride ion transport media. It is known that the tysonite MF3 (M= La and Ce) and fluorite MF2 (M= Ca, Sr and Ba) type compounds are super fluoride ion conductors at high temperatures. However, when they are doped with aliovalent fluorides they conduct at ambient temperatures. Here we synthesized fast fluoride ion conductors in the La1-xBaxF3-x (x le; 0.15) and Ba1-xLaxF2+x (x le; 0.55) system by mechanical milling. The fluoride ion conductivity was measured by electrochemical impedance spectroscopy. The compounds were characterized by powder XRD and 19F MAS NMR spectroscopy. Electrochemical cells were built with various metal fluorides as cathods, La0.9Ba0.1F2.9 as electrolyte and Ce metal as the anode. The effect of grain boundary on fluoride ion conductivity was studied in detail. The detailed results will be described and discussed.
References
1. J. H. Kennedy and J. C. Hunter, J. Electrochem. Soc., 1976, 123(1), 10.
2. M. Anji Reddy and M. Fichtner, J. Mater. Chem., (2011), 21, 17059 -17062.

The prototypical lithium ion battery electrolyte consists of LiPF6 dissolved in a mixture of cyclic and linear carbonates, ethylene carbonate (EC) and dimethyl carbonate (DMC) as examples of the former and latter, respectively. The solvation shell structure of the Li+ ions affects properties that directly impact the electrochemical performances of Li ion batteries, such as ionic conductivity, transference number, the chemical composition of the solid electrolyte interphase (SEI), as well as charge transfer kinetics across this interphase. Natural abundance 17O nuclear magnetic resonance (NMR) spectra have been obtained for a series of EC/DMC solutions ranging from 0 to 100% EC with fixed 1M LiPF6 concentration. As expected, the resonances of the carbonyl oxygen are most strongly affected by the salt, with only indirect inductive effects observed for the ether oxygens. Moreover and also in line with expectations and prior investigations, the salt effect on the EC shift is significantly larger than on the DMC shift, indicating a preferential solvation of Li+ by EC. The EC carbonyl salt shift also exhibits a much larger dependence on EC/DMC ratio than observed for DMC. Using a simple model of dynamic equilibrium between associated and non-associated solvent molecules it is possible to extract an average primary Li+ solvation structure as a function of EC/DMC concentration.

The novel concept of a lithium battery&’s solid-state electrode materials with ionic-liquid (IL) properties is presented and contributes to addressing the challenge of energy storage, which is one of the major challenges of the 21 st century. These composite materials are a mixture of electroactive matter, an electronic conductor, a solid-state ionic conductor and a polymeric binder. The approach of a solid-state ionic conductor combines the high safety of an IL with the nanoconfinement of such a liquid in a mesoporous silica framework, an ionogel, thus leading to a solid with liquid-like ionic properties. The same ionic conductor is also used as a solid-state separator to evaluate the properties of our solid-state electrode materials in all-solid-state batteries. The ionogel, along with its processability, allows a single-step preparation of the assembly of the solid-state electrode and solid-electrolyte separator and can be applied without specific adaptation to present, thick electrodes prepared by the widespread tape-casting technique.
Further developments are also presented: ink jet shaping for microdevices, enhanced flexibility or sustainability with specific polymers and biopolymers association. Advantageous thermal dependence of the ionic conductivity will be presented. The resulting batteries evaluation will also be presented, without specific adaptation to state-of-the-art positive electroactive materials developed for future-generation lithium-ion batteries, namely LiFePO4 and LiNi1/3Mn1/3Co1/3O2.

Poly(ethylene oxide) (PEO) has been used in both the electrolyte solvent and electrode binder of lithium polymer batteries since 1995 due to the ion conduction through the coordination of the lithium ions and the oxygen atoms in the polymer chain. Such comparability with the Li metal salts and the ion conductance suggests that PEO be used as a binder material for the composite electrodes of lithium ion batteries. However, the high solubility of PEO in electrolyte solvents increases the dissolution of PEO into the electrolyte during charging/discharging cycles and it would cause the instability of the battery performance. In addition, PEO suffers from the poor mechanical adhesion into the current collectors. In this study, PEO was cross-linked and coated on the surface of graphite via two-phase synthetic process in order to ensure the uniform coating of PEO onto graphite and prevent the PEO precursors from being homogeneously polymerized in the solution without being coated onto the surface. The as-modified graphite was used as an anode material and assembled into coin cells. The as-prepared composite anode shows the strong adhesion between the electrode materials and copper current collector and the good electrochemical cyclability.

The needs for high energy density energy storage device, especially in electric vehicle and hybrid vehicles, has triggered worldwide research on developing rechargeable lithium metal batteries, such as Li/S, Li/O2 and Li/Air. A mechanically strong ionic conductive dense separator is essential. Solid ionic conductors based on a LiM2(PO4)3, where M is a metal structure (analogous to a Nasicon type structure) are among the most promising group of oxide-based solid lithium ion conductors investigated in recent years as they possess certain advantages in terms of electrical conductivity, mechanical strength, and stability in air compared to other solid electrolytes. Lithium aluminum titanium phosphate (LATP) and lithium aluminum germanium phosphate (LAGP) glass-ceramic solid electrolytes have conductivities in the 10-3 to 10-4 S/cm range at room temperature.
Currently, the often used commercial available LTAP has a thickness of 150 micron. With such a thick separator, it is not possible to achieve 1250 Wh/kg because the separator is too heavy.[1] As analyzed by Albertus, the thick glass/ceramic electrolyte separator counts for about 25% of the weight of a cell. In this research, thin glass ceramic LAGP electrolyte membrane with thickness of ~<30 micron was developed. The thin inorganic membrane can be winded onto a cylindrical object with a diameter of 10 centimeter without broken. The mechanical toughness was further improved by lamination of ionic conductive polymer. With thin electrolyte membrane separator, the estimated cell weight deduction is about 20%. In addition, the equivalent series resistance (ESR) is also reduced significantly.
This research was supported by Army STTR Phase II contract with award # of W911NF-11-C-0071.
References:
1) Christensen, J.; Albertus, P.; Sanchez-Carrera, R.; Lohmann, T.; Kozinsky, B.; J. Electrochem. Soc., 2012, 159, R1-R30

High power performance and long cycle life are essential to the lithium ion batteries (LIBs) technology, which is one of the key issues for solving the energy crisis such as for powering automotive vehicles. Efficient electrodes are the hard core for the performance improvement of LIBs. Fundamentally, LIBs rely on shuttling lithium ions and electrons between the cathodes and anodes. To realize high power and energy densities, sufficient number of lithium ions and electrons need to be rapidly shuttled between the electrodes, which implies that high-performance architectures should possess effective ion- and electron- transport pathways and high active-material loading. In this work, we present an efficient fabrication strategy towards high-performance electrodes from conductive scaffolds of graphene and the nanocrystals (NCs) of active materials. To demonstrate this concept, the cubic spinel lithium titanate (Li4Ti5O12) NCs were used as a model material due to its proper voltage plateau (~1.5 V vs. Li/Li+) above the potential range where most electrolytes are reduced. Besides, Li4Ti5O12 undergoes extremely small expansion and contraction during charge-discharge cycling, showing a significant cycling stability. Despite its advantages, its intrinsic low electronic conductivity (<10-9 S cm-1) leads to poor high rate performance in the application as electrode material in LIBs. So far, much effort has been devoted to synthesizing various nanostructured Li4Ti5O12 or its composites. However, current synthesis is still not sufficient to prepare Li4Ti5O12 with excellent rate performance with sacrificing cyclability. In comparison, our strategy relies on building a graphene-based architecture achieved through an aerosol-assisted approach, which enables the efficient assembly of the NCs within conductive graphene scaffold. Such architecture exhibits an outstanding rate performance as well as the electrode stability. For example, the electrode shows a capacity of 147 mA h g-1 at 1C, and still possesses a capacity of 75 mA h g-1 at 100C. Therefore, such a graphene architecture holds great promise in practical application of high power LIBs.

Vertical-standing graphitic nanopetals with nanometer thickness were grown by microwave plasma-enhanced chemical vapor deposition on Ni foam templates. After chemically etching away the Ni template, highly conducting and free-standing graphitic-nanopetal foams were obtained for use as electrochemcial supercapacitor electrodes. The nano-petal foams provide both current collection capability and active electrochemical surfaces. The graphitic nature of the vertical nanosheets further increases surface area, and the hollow channels enable electrolyte access to the graphene layers under the graphitic petals. Scanning electron microscopy (SEM) determined that the nanopetals extend approximately 300 nm above the Ni foam surface, with a lateral width for a single unwrinkled 2-D petal ranging between 100 nm to 300 nm. The thickness of a graphitic petal was found to be typically less than 50 graphene layers as measured by transmission electron microscopy (TEM). TEM was also used to confirm the graphitic nature of the as-grown petals. The electrochemical performance was characterized by cyclic voltammetry and charge/discharge measurements in a standard three-electrode cell consisting of Ag/AgCl as the reference electrode, Pt mesh as the counter electrode and the synthesized nanopetal foam as the working electrode. After electrochemical oxidation of a petal foam electrode for 15 min in 1M H2SO4, the electrode exhibited an areal specific capacitance of approximately 0.2 F/cm2, more than two times higher than reported for graphitic petals on carbon cloth. XPS and Raman were used to further characterize the graphitic petals after oxidation. Our results indicate that free-standing graphitic-nanopetal foams have potential use as electrochemical active materials in supercapacitor applications.

Although graphene, a single layer of carbon atoms, has received attentions as an attractive material in electrochemical applications, some of its electrochemical behavior remains unexplained. For example, it has been suggested that the amount of Li absorption in a single layer graphene can exceed LiC₆ which would yield a larger capacity anode material beyond conventional bulk graphite.
We present first-principles calculations to investigate the Li absorption in a single layer and few layer graphene. For a single layer graphene, the cluster expansion method is used to systemically search the lowest energy ionic configuration as a function of absorbed Li content. The results predict that Li ions cannot reside on the surface of the graphene unless the graphene includes defects, which means that single layer defect-free graphene would exhibit inferior capacity compared to that of conventional bulk graphite. Furthermore, few layer graphenes are examined to compare their Li absorption capability to bulk graphite. We calibrate the empirical potential parameters to include the effect of van der Waals interactions, which is essential to account for the contribution of empty (no Li) layer to the total energy. The result shows a clear deviation of bi-layer graphene from the other few layer graphenes and predicts the number of graphene layers to show the electrochemical behaviors similar to bulk graphite in terms of the Li absorption mechanism. Finally, we identify the change in chemical bonding and Li reactivity as we increase the number of graphene layers, transforming from the nano regime to bulk graphite.

Highly robust, flexible, binder-free lithium-ion battery electrodes were constructed based on carbon nanotube (CNT) interweaved networks and electrochemical active materials. The composite electrodes possess hierarchically pore networks and long-range electron conductive pathway, which achieve rapid electron and ion transport for electrochemical energy conversion and storage. Typical architectures, including nanocrystal/CNT, nanowire/CNT, nanosheet/CNT and cluster-like microparticles/CNT, were fabricated to demonstrate the efficiency of the binder-free electrodes. As-fabricated battery electrodes show battery-like capacity and supercapacitor-like rate performance. Further, as a novel type of electrodes compared to traditional carbon black-polyvinylidene fluoride bound ones, the engineering design of binder-free electrodes have been discussed for maximum utilization of battery materials.

Ion-conductive polymer electrolytes are key materials in electrochemical energy conversion and storage devices. Perfluorosulfonic-acid (PFSA) membranes, the most commonly used electrolyte for polymer-electrolyte fuel cells (PEFCs), have good mechanical stability and high proton conductivity, and therefore serve as the model material for emerging energy technologies such as redox flow batteries and solar-fuel generators. Their perm-selective properties make them of interest; however, the degradation of the membranes in environments with changing temperature, humidity, and solvent types and concentrations impose a technical barrier that has to be overcome for improving the system performance and device durability. In PEFCs, chemical decomposition of the membrane due to the attack of radicals formed during operation along with the formation of pinholes, cracks, and delamination due to the mechanical stressors leads to increased crossover of reactant gases and reduced efficiency. Since the chemical and mechanical stressors are largely influenced by temperature and humidity, it is difficult to determine what mechanisms dominate the membrane lifetime during operation. To understand the underlying mechanisms of failure under chemical, mechanical, and chemical-mechanical degradation modes, and assess membrane lifetime in shorter time periods, accelerated stress tests (ASTs) are commonly employed. In this work, we investigate and compare the in-operando failure of membranes in three degradation modes based on AST data. Nanostructure of failed membranes studied using Small-Angle X-Ray Scattering (SAXS) technique and their water-uptake behavior are compared with those of fresh membranes to identify the effect of chemical and mechanical stressor on the membrane's structure-function relationship. In addition, a multi-parameter continuum-based mechanistic model is developed to determine the crossover as a function of relative-humidity cycles based on the stress-state around a hypothetical pinhole in the membrane where crossover is assumed to take place. Model predictions are obtained using the available water-uptake data and mechanical properties of degraded membranes, and a sensitivity analysis is performed to investigate the effect of properties and model parameters on the predicted lifetime. Using the modeling approach and based on preliminary degradation data, we will also elaborate how chemical and mechanical stressors could affect each other and control the failure mechanisms in the membrane and explain the observed difference in the nanostructure due to different degradation modes.

Sodium β"-alumina batteries (NBB&’s) have received increasing interests as an energy storage device for renewable energy applications due to high specific energy density and power density. Among them, sodium-metal halide battery has several advantages over sodium-sulfur (NaS) battery including safe cell failure mode and easiness of assembly in discharged state. The major barrier to commercialize sodium-metal halide battery is relatively high cost compared to NaS battery. Therefore, our research at PNNL has focused on lowering the cost of sodium-metal halide battery. Two approaches have been taken to develop low-cost sodium-metal halide battery: (i) intermediate-temperature Na-NiCl2 (IT-ZEBRA) battery and (ii) Zn-based battery. IT-ZEBRA battery operates at 200°C or less, at which economical compressive polymer seals can be used to enable a low-cost high throughput manufacturing process. For Zn-based battery, the use of zinc, of which the price is less than 1/8 compared to nickel, can significantly decrease material cost.
In this presentation, the results of our development efforts will be discussed in detail.

Low cost energy storage systems are the key technologies for the fluctuating supply of electricity based on solar and wind power. Aqueous, or water-based, sodium ion batteries offer multiple cost savings using less expensive electrode materials and much cheaper electrolyte solutions compared to the lithium ion cells. The first necessary step is identification of electrode materials, both the anode and cathode, which undergo redox processes approximately within the voltage stability region of water.
For this presentation, we will discuss the electrochemical behavior of selected electrode materials in sodium-ion cells. The effect of electrolyte conditions including salt type and concentration, basicity and additives on electrode and water stability will be presented. A comparison between organic and aqueous electrolytes will also be stressed to highlight the potentials and limitations in water-based sodium-ion batteries.

Ambient temperature, non-aqueous sodium-ion batteries are an attractive technology for grid storage applications, providing the high power of lithium-ion systems using potentially cheaper materials. As several high-capacity transition metal oxide cathode materials have been developed, the key to improving the rapidly developing sodium-ion technology is increasing anode material capacities and cycleability. We have studied several promising sodium-ion anode materials, including hard carbon, tin and antimony, using various synchrotron x-ray techniques to characterize the chemical and structural changes in these materials during sodiation/desodiation. Developing a mechanistic understanding of the processes underlying sodium insertion in these materials will allow design of optimized sodium-ion anodes.

Na-NiCl2 battery (Zebra) uses a secondary electrolyte (NaAlCl4) in the cathode side with NiCl2 as the active cathode materials. Due to some important advantages of Na-NiCl2 battery, such as lower operating temperatures, safe cell failure mode, higher voltage, assembly at the discharged state, Na-NiCl2 battery got more attentions as a candidate for stationary electric energy storage for renewable energy applications as well as smart grid applications. Although Zebra battery has been developed for decades, the detailed functions of additives has not been completely revealed. In this presentation, we will present studies, such as morphology of NaCl and Ni particles, to have better understanding for the effects of cathode additives on battery performance.

Sodium ion batteries have become one of the widely investigated and promising systems amongst rechargeable batteries due to their low cost and abundance of resources. Large scale energy storage applications like grid storage mandate reliable and cheap energy storage. In this regard sodium based chemistries have a considerable leverage compared to lithium ion batteries.
The key challenge is to identify new materials that can reversibly insert Na ions within their crystal structures without structural damage. A number of materials like NaCoO2, NaFePO4, NaxMnO2, NaxV2(PO4)3 have been identified and studied as potential candidates. But most of these materials are limited by the low cell voltage, poor cycling performance and low gravimetric energy density.
Insertion type host materials are crystal structures with open framework for ionic conduction and pathways for electronic conduction (mixed conductors). Layered structures are excellent mixed conductors because they have 2-D ionic pathways and interconnected transition metal octahedra for electronic conduction. We focused our efforts on exploring an appealing layered structure, Sodium Nickel Titanate (SNTL). SNTL has a stoichiometry of Na0.67Ni 0.33Ti0.67O2 with nickel and titanium atoms occupying the same layer and sodium layers alternating between the transition metal layers. SNTL has been reported as a good ionic conductor. However, currently there is no report on utilizing this material as an intercalation type sodium cathode. SNTL is a potentially good candidate due to its high theoretical capacity (~182 mAh/g) and high electrochemical potential (due to Ni2+/4+ redox couple). Since the operating voltage is >3.2 V (vs. Na/Na+), only nickel gets oxidized, while titanium does not electrochemically participate and maintains its oxidation state of 4+.
SNTL was synthesized by the solid state reaction and characterized by XRD and SEM. Preliminary electrochemical measurements revealed that sodium de-intercalation/intercalation is reversible in Na0.67-xNi 0.33Ti0.67O2 for ‘x&’ value of 33%. The discharge voltage curve almost followed the charging voltage curve without much hysteresis showing that the reaction is insertion type and reversible. The voltage profiles were sloping in the voltage range of 3.2-4.2 V indicative of solid solution type reaction. Experiments are being carried out to evaluate diffusion co-efficient values by GITT and to increase ‘x&’ value.

Battery community has renewed its interest towards the development of ambient temperature sodium-ion batteries. The reasons are twofold, sodium is inexpensive and abundant and hence it could be a feasible solution for grid storage. While exporting knowledge from Li-ion technology seems to be a useful tool to foster development of the analogous sodium technology, differences in crystal chemistry need to be taken into account when dealing with electrode materials. Indeed, layered A2Ti3O7 titanates operating on Ti4+/Ti3+ redox couple exhibit very different potentials for lithium and sodium intercalation, which are a priori unexpected [1]. In situ XRD coupled with DFT calculations provide deeper understanding of Li/Na insertion into these phases and help in elucidating the reason for such behavior and illustrate how assumptions over operating potential may be misleading [2]. Such an approach will be crucial to design alternative low potential anodes which could be coupled with high potential cathodes to build high energy density sodium ion batteries.

Sodium ion batteries have recently drawn increasing attention as an alternative to lithium ion batteries for large-scale energy storage devices. Sodium-ion cells benefit from more abundant sodium resources and lower materials cost. The well-established understanding of lithium based electrochemical system helps the fast development of Na based components. One challenge is identification of suitable negative electrode materials, because sodium does not intercalate into graphite.
In this presentation, we will introduce a new titanate anode material displaying high specific capacities of 200-300 mAh/g during electrochemical cycling. The structural and electrochemical characterization of the new electrode material will be presented and compared with other titanates. In addition, the impact of structural factors on intercalation of sodium will be discussed.

It is well known that a solid electrolyte interface (SEI) layer will be formed on graphite anode in the state-of-the-art lithium-ion batteries due to the reductive decompositions of solvent molecules and lithium salts. The continuous increase in the thickness of this SEI layer with cycling and at higher temperatures increases the internal resistance of the batteries, reduces the cycle life and calendar life of the batteries, lowers the battery performance at low temperatures, and leads to safety problems.
Spinel Li4Ti5O12 has been extensively studied in recent years as an alternative anode material to replace graphite and is believed to be one of the very promising anode materials for large-scale lithium-ion batteries because of its negligible volume change, high thermal stability, and flat potential around 1.55 V vs. Li/Li+ during charge and discharge preventing SEI formation, therefore excellent cycle life, high temperature performance and high safety could be achieved even at elevated temperatures. However, the low electronic conductivities of spinel Li4Ti5O12 results in poor rate capability and power performance, preventing it from being widely used. Several approaches have been pursued over the past few years to improve the power performance of Li4Ti5O12. One way is to develop nano-sized particles in order to reduce Li+ diffusion paths and to provide large contact area between the electrode and electrolyte. Another is to improve the electrical conductivity of the active materials by cation doping, surface modification with metals or oxides, and carbon coating. Although the poor electronic conductivity of Li4Ti5O12 has been greatly improved by modifying the materials as described above, the power performance has not been satisfactory.
In this talk we report a low-temperature process to co-dope Al3+ and F- ions into Li4Ti5O12 to form uniform composite anode materials thus significantly improve the high-rate performance of the Li4Ti5O12 anode material while maintain its excellent high temperature performance and long cycle life. The material preparation, characterization and detail of the improved performance will be presented.
Acknowledgement: This work was sponsored by the Office of Vehicle Technologies of the U.S. Department of Energy.

Lithium titanate (Li4Ti5O12) has attracted great interest as an anode material for lithium ion batteries due to its safety, low cost, and zero-strain effect during Li insertion/extraction. However, its intrinsically low electronic conductivity (< 10-13 S cm-1) limits its practical use in battery applications. One-dimensional (1D) nitridated Li4Ti5O12 nanofibers were successfully synthesized via simple electrospinning method and subsequent nitridation process. One dimensional geometry and highly conducting TiN/TiOxNy shell layers formed on the surface of Li4Ti5O12 nanofibers enables fast electron transport, which results in significant improvement in rate capability. Nitridated Li4Ti5O12 nanofiber electrode shows about 1.35 times larger discharge capacity than that of bare Li4Ti5O12 nanofiber electrode at a 10 C rate.

In recent years, TiO2 has been identified as one of the most promising materials for electronic devices including solar cells and Li-ion rechargeable batteries (LIBs), because of its relatively high abundance in nature, low toxicity, and safe to handle. However, its&’ intrinsic physicochemical properties of low electronic conductivity leads to relative poor rate capability owing to the poor electron transport when utilized as a host for Li-ion intercalation, which limits its practical application. Meanwhile, promising TiO2 based mesoporous sphere materials have been widely reported as electrode materials for LIBs. Micrometer sized sphere has also been considered as the optimal material morphology in conventional electrode fabrication technique, since this kind of architecture has the function of ensuring high contact area between electrolyte and electrode, short diffusion distances for Li+ transport, good accommodation of strain during cycling, as well as high packing density.2 However, one concern for mesoporous materials is the long transport distance of electrons in micron sized particles, especially for low conducting TiO2. Therefore, increasing the electronic conductivity of TiO2 becomes more important for mesoporous TiO2 materials. According to our previous study, it predicted that Cr-N is the preferred codopant pair using first-principles calculations. And also Cr-N codoped TiO2 nanoparticles indeed exhibited substantially narrow band gaps, as well as dramatically enhanced photoabsorption and photoactivity in the visible spectral region. Therefore, it is highly desirable to develop a Cr-N codoped TiO2 with the morphology of mesoporous microsphere that could combine the advantages of the mesoporous structure, spherical morphology, and higher electronic conductivity, this combination which has not been reported before. We will report in detail about a facile synthesis of Cr-N codoped mesoporous TiO2 microspheres with enhanced electrical conductivity as high power anode materials for LIBs, which exhibit high capacity, good cycling performance, and high rate capability.
Research at ORNL was sponsored by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (MSED). Research at CNMS and SHaRE facilities were sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, US Department of Energy.

Hybrid lithium ion energy storage devices are attractive for combining high energy density with high power capability and long cycle life. These advantages have been demonstrated in both asymmetric (activated carbon / Li4Ti5O12 (LTO) device) and hybrid lithium ion device (activated carbon- Li4Ti5O12 / Li cathode) where the emphasis was on the anode and improved charging rates. For rapid discharge, several researchers have focused on the formation of hybrid cathodes by combining conductive organic polymers (COP), or other organic charge transfer materials with inorganic materials. However these concepts have suffered other drawbacks such as high self-discharge rates and an insertion-deinsertion mechanism of anions that is rate limiting. To improve upon this concept, we present a hybrid device in which a composite cathode contains a high power organometallic component combined with a high energy capacity metal oxide cathode. Characterization of the polymer material and composite electrode along with cycle performance data will be presented.

Since Sony launched its first lithium ion battery (LIB) to the market, LIBs have been the energy storage device currently available that has deserved the most attention, especially for portable devices, due to their high energy density, long life span, and zero memory effect [1]. During the past decade much effort has been devoted to design high performance and high stability batteries. However, each main component of the LIB (cathode, anode, electrolyte, and separator) still requires further improvement of the current technology in terms of energy/power density, price, safety, and environmental friendliness to enable deeper and wider application of LIBs [2,3]. Titanium dioxide has attracted considerable interest as alternative anode material due to the relative small volume change upon lithium insertion/extraction and a working potential within the electrochemically stable window of carbonate based organic electrolytes [4]. Among the various polymorphs, anatase has been the most studied system so far, probably due to the higher thermodynamic stability of this phase at the nanoscale [5].
In this work, we investigated the electrochemical behaviors of anatase TiO₂ of different sizes and morphologies [6]. In order to study intrinsic properties, composite electrodes were prepared without carbon additives. TiO₂ nanorods revealed exceptionally high cyclability and capacity retention at very high rate cycling rates despite absence of conductive additives. In situ electrochemical impedance spectroscopy (EIS) was carried out for a better understanding of the electrochemical processes involved when cycling anatase nanocrystals.
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[2] J. Cabana, L. Monconduit, D. Larcher, M. R. Palacín, Adv. Mater., 2010, 22, E170-E192.
[3] C. Liu, F. Li, L. P. Ma, H. M. Cheng, Adv. Mater., 2010, 22, E28-62.
[4] J. B. Goodenough, Y. Kim, Chem. Mater., 2009, 22, 587-603.
[5] M. Wagemaker, W. J. H. Borghols, F. M. Mulder, J. Am. Chem. Soc., 2007, 129, 4323-4327.
[6] R. Buonsanti, T. E. Pick, N. Krins, T. J. Richardson, B. A. Helms, D. J. Milliron, NanoLett., 2012, 12, 3872-3877.

Herein we report on the use of a new family of two-dimensional, 2-D, transition metal carbides, so called MXenes, as anode materials in lithium ion batteries (LIBs). MXenes are synthesized by selective etching of Al from the MAX phases, such as Ti₂AlC, Ti₃AlC₂, Nb₂AlC etc. The latter are a large family (+ 60 members) of hexagonal layered ternary metal carbides and/or nitrides; where “M” stands for an early transition metal, “A” stands for a group 13 to 16 element, and “X” stands for carbon and/or nitrogen. Etching the “A” layer from the MAX phases using hydrofluoric acid at room temperature resulted in a weakly bonded MX layers that were readily separated by sonication forming 2-D layers. To emphasize their similarity to graphene, we labeled these new solids MXenes. MXene anodes showed excellent ability to handle high charge/discharge rates with good Li⁺ uptake. In situ XRD analysis shows reversible Li ion intercalation between MXene layers. Additive-free Ti₃C₂ anodes showed a capacity of 410 mAh.g^-1 at cycling rate of 1C and 110 mAh.g^-1 at 36C for at least 200 cycles. In addition to the good gravimetric capacity at very high cycling rates, MXenes showed excellent volumetric capacity. Both advantages suggest MXenes as good candidates for use as anode material in LIBs for vehicular and grid energy storage. The simplicity of the synthesis process may enable the large-scale production of MXenes.