Layered oxides with NaxMO2 formula (M: transition metal), were studied in the 80's for their intercalation properties, then for 20 years all the researches were focused on lithium batteries, that exhibit the high energy density required for portable devices. In the perspective of the development at very large scale of renewable energy systems that require stationary batteries, the prevailing parameters are the lifetime, the price and the material availability. From these points of view, sodium based batteries have to be investigated. We studied the NaxMO2 (M = Co, V) and Nax(Co,Mn)O2 systems with a special focus on the electrochemical behavior in relation with the oxygen packing of the starting material. The structures of all starting materials were determined by Rietveld refinement of their X-Ray diffraction patterns. The electrochemical study was carried out in sodium batteries with a solution of NaClO4 or NaPF6 in PC as electrolyte. For all materials a very good reversibility of the electrochemical process was observed. In all systems 0.5 Na can be cycled that corresponds to a capacity close 150 mAh/g of active material Depending on the structure of the layered starting phases O3 for NaVO2 or P2 for the Na0.70CoO2, Na0.72VO2, Na0.67Co2/3Mn1/3O2 very different electrochemical behavior were observed. Nevertheless, in all systems a significant potential drop was observed for x = 1/2 and 2/3 that emphasize the existence of Na+ ordering in the cobalt and vanadium phases, while a change in the redox process is expected at x = 2/3 for the (Co, Mn) phase. All peculiar deintercalated compositions were characterized either for structural and physical point of view. In the case of the NaxVO2 systems two different phases were obtained for the Na1/2VO2 composition depending of the packing of the starting material. These two phases exhibit very similar sodium ordering in the interslab space but very different vanadium ordering in the VO2 slabs. Due to the presence of V3+ (d2) and V4+ (d1) very interesting structural and physical properties were obtained. A general overview of the properties of these materials will be presented.

In recent years, there has been a resurgence of interest in Na-ion batteries due to sodium&’s relative abundance and potentially lower cost when compared to lithium. Nonetheless, Na-ion battery chemistry remains relatively unexplored compared to Li-ion, and there is great potential in the combined application of experimental and first principles techniques to significantly accelerate Na-ion battery chemistry design and understanding. In this work, we present an investigation of transformation mechanisms in layered sodium transition metal oxide electrode materials, and compare these mechanisms to the mechanisms in the lithium counterparts. It has been well established that NaMO2 layered compounds in general undergo a greater variety of structural transformations upon desodiation than the LiMO2 layered compounds. We will present an analysis of the coordination preference of Na+ versus Li+ in the layered structural frameworks, and discuss how these site preferences result in differences in the electrochemical performance between Na-ion and Li-ion layered materials.

The renewed interest in Na-ion technologies is stimulating the search of suitable intercalation compounds that possess the capability to accommodate large Na⁺ ions while keeping an acceptable mobility. A recent work by Moreau et al. has proved reversible electrochemical insertion/extraction of Na into the olivine structure to give NaFePO₄, with promising electrochemical properties despite the large cell mismatch associated to the transformation. However, fundamental differences are observed in the voltage-composition curve when compared to its lithium counterpart. Indeed, two different plateaux are observed upon Na⁺ extraction that would be related to two successive first order transitions concomitant with the formation of an intermediate Na_1-xFePO₄ (xasymp;0.3) phase. In this work we will show a thorough study of the mechanism of Na insertion and extraction in the FePO₄/NaFePO₄ system. The different processes occurring upon battery cycling are studied by in situ and ex situ techniques, revealing the occurrence of significant modifications that might have a strong impact in the cyclability of the material. In parallel, the different phases occurring upon battery cycling have been prepared chemically in order to reproduce the electrochemical reaction occurring in a Na-ion cell. We have succeeded in isolating the intermediate phase, whose characterisation by XRD and electron diffraction has revealed unexpected findings. The obtained results will be discussed in terms of the mechano-chemical aspects of the charge and discharge reactions and will be contrasted with the mechanism of the FePO₄/LiFePO₄ system.

The key issue to the success of electric vehicles (HEV, PHEV, and EV) and large-scale energy storage systems for renewable energy lies in the advancement of electrode materials for rechargeable battery. However, cost per energy and safety hazard of conventional electrode have so far prohibited its wide usage in large-scale applications. In this respect, the search for cathode materials composed of polyanion using naturally abundant iron as a redox center is a timely significance. While, the olivine structured material, LiFePO4,[1],[2] is a current popular cathode materials for lithium batteries, recent studies in polyanion materials with a Fe2+/Fe3+ redox couple have identified new compounds such as fluorinated iron phosphate, Li2FePO4F,[3] fluorinated iron sulfate, LiFeSO4F,[4] iron silicate, Li2FeSiO4,[5] and iron borate, LiFeBO3 [6] as alternative candidates. However, the synthesis of fluorinated compounds requires complex and costly procedures and their theoretical capacities are hardly obtainable, lithium iron silicates and iron borates are unable to provide sufficient voltage, and the specific capacity of Li2FeP2O7 is only below 110 mAh g-1. To solve these problems, we successfully synthesized new iron based compound, LixNa4-xFe3(PO4)2(P2O7). This series of materials have been neither synthesized nor documented before. First principles calculations presented the three-dimensional (3D) sodium/lithium paths with their activation barriers and revealed them as fast ionic conductor. The reversible electrode operation was found both in Li and Na cells with the theoretical capacities of 140 mAh g-1 and 129 mAh g-1, respectively. The redox potential of each phase was found to be ~3.4V (vs. Li) for Li-ion cell and ~3.2V (vs. Na) for Na-ion cell. The properties of high power, small volume change and high thermal stability were also recognized presenting this new compound as a potential competitor to other iron-based electrodes such as LiFePO4, Li2FeP2O7 and Li2FePO4F. References [1] Chung, S.-Y.; Bloking, J. T.;Chiang, Y.-M. Nat. Mater. 2002, 1, 123-128. [2] Delacourt, C.; Poizot, P.; Tarascon, J.-M.; Masquelier, C. Nat. Mater. 2005, 4, 254-260. [3] Ellis, B. L; Makahnouk, W. R; Makimura, Y.; Toghill, K.; Nazar, L. F. Nat. Mater. 2007, 6 (10), 749-753. [4] Recham, N.; Chotard, J.-N.; Dupont, L.; Delacourt, C.; Walker, W.; Armand, M.; Tarascon, J.-M. Nat. Mater. 2009, 9 (1), 68-74. [5] Nyten, A.; Abouimrane, A.; Armand, M.; Gustafsson, T.; Thomas, J. O. Electrochem Comm. 2005, 7 (2), 156-160. [6] Yamada, A.; Iwane, N.; Harada, Y.; Nishimura, S.; Koyama, Y.; Tanaka, I. Adv. Mater. 2010, 22 (32), 3583-3587.

Since Lithium-ion batteries are being considered as large-scale energy-storage systems[1], the search for electrode materials to replace LiCoO2 is becoming important. In particular, olivine structured LiFePO4[2] are of interest because they are considered safe. In addition to olivine materials, other new materials have been investigated as alternatives to oxide-based cathode materials. Recently, we reported a newly synthesized LixNa4-xFe3(PO4)2(P2O7)[3] which contains 3D sodium/lithium paths, has good electrochemical properties (140mAh/g with 3.4V for Li cell and 129mAh/g with 3.2V (vs Na) for Na cell). Moreover, the properties of high power, small volume change, and high termal stability were also recognized. In this work, we report on a series of A4M3(PO4)2(P2O7)(with A = Na, Li; M = Fe, Mn, Co etc.) identified by high-throughput First principles calculation. The computed voltage, diffusion barrier, structural analysis, and the stability were analyzed. There are four symmetrically distinguishable Na sites in the NaM3(PO4)2(P2O7) crystal, and these are connected to each other throughout the 3D framework. For the case of Na4Fe3(PO4)2(P2O7), all the Na sites are connected 3-dimensionally with activation barriers lower than 800 meV, from which we can identify the fast diffusion pathways of Na. While all Na sites are connected with reasonably low activation barriers, the Na diffusion in the large tunnel along the b-axis (Na1-Na1) shows the lowest activation barrier. The average voltage of the A4M3(PO4)2(P2O7) are also examined with First-principles calculation. Li3NaFe3(PO4)2(P2O7) is only slightly higher than that of Na4Fe3(PO4)2(P2O7). It is attributed to the relative instability of Li ions in the crystal framework which is derived from a parent Na-phase.

Monoclinic NaNiO2 is re-investigated as a positive electrode material for sodium ion batteries. Galvanostatic cycling of NaNiO2 between 2.0 - 4.5 V gives 190 mAh/g charge capacity (Δx = 0.81) and 141 mAh/g discharge capacity (Δx = 0.60) for the first cycle at C/10 rate, but leads to rapid capacity fade. Cycling between lower voltage limits (1.25 - 3.75 V) results in 147 mAh/g charge capacity (Δx = 0.63) and 123 mAh/g discharge capacity (Δx = 0.52) for the first cycle at C/10 rate. During potentiostatical intermittent discharge about 0.62 and 0.46 Na can be intercalated from NaNiO2 from 2.2 - 4.5 and 2.0 - 3.85 V respectively. Charge and discharge curves are similar indicating similar reaction paths with identical intermediate phases forming upon charge and discharge.

In this study we investigate one of the most promising candidates as a cathode material in lithium batteries: LiMn1.5Ni0.5O4. This compound, which belongs to the spinels family LiMn2-xMxO4 (with x = 0.5; M = Mg, Cr, Mn, Fe, Co, Ni, Zn), has the advantage to produce a less significant oxidation of the electrolyte. It presents a high charge/discharge potential at about 5 V [1] caused by Ni2+ to Ni4+oxidation, which completely replaces the oxidation process of the Mn4+ /Mn3+ pair observed at ca. 4.0 V [2]. The structure and the performances of LiMn1.5Ni0.5O4 depend on the preparation method. In particular, it has been reported that compounds synthesized above 650 °C loose oxygen and separate in a spinel phase with a smaller Ni content and a LiyNi1-yO phase. This leads to the introduction of some Mn3+ and causes the development of a 4-V plateau and a decrease in 5-V capacity [2]. Therefore the investigation of the role of the Mn3+ ions in the physical properties of these compounds results of fundamental importance. In the present work LiMn1.5Ni0.5O4 [3] is studied by means of Anelastic Spectroscopy (AS) and Thermogravimetric Analysis coupled with Mass Spectrometry (TGA-MS) measurements. Anelastic Spectroscopy provides the values of the Young&’s modulus, E, and of the elastic energy loss Qminus;1 . It is a very sensitive tool to investigate phase transformations and to provide information on the motion parameters of mobile species [4]. We show that there are no contributions to elastic energy dissipation from mobile species in the stoichiometric compound, whereas after thermal treatments (TT) a thermally activated relaxation process is clearly detectable, whose features strongly depend on the experimental conditions of the TT&’s. The oxygen loss observed by TGA during the TT&’s in vacuum confirm the presence of O deficiency in the stoichiometry which induces the presence of Mn3+ ions. Possible models for the physical origin of the peak are discussed and we suggest that the relaxation process may be due to the dynamics of the polarons constituted by the Mn3+/Mn4+ charges and the associated lattice distortion. [1] T. Ohzuku, S. Takeda, and M. Iwanaga, J. Power Sources, 81, (1999) 90. [2] Q. Zhong, A. Bonakdarpour, M. Zhang, Y. Gao, J.R. Dahn, J. Electrochem. Soc. 144, 205 (1997). [3] L.H.Chia, N. N. Dinha, S. Brutti, B. Scrosati, Electrochimica Acta 55, 5110 (2010). [4] A.S. Nowick, B.S. Berry, Anelastic Relaxation in Crystalline Solids. (Academic Press, New York, 1972). Acknowledgments: The results of this work have been obtained by the financial support of the European Community within the Seventh Framework Programme APPLES (Advanced, High Performance, Polymer Lithium Batteries for Electrochemical Storage) Project (contract number 265644).

Lithium-ion batteries have been widely used in portable electronic devices due to its high energy density, lightweight design than other comparable battery technologies. LiMn₂O₄ spinel is expected as cathodic materials in lithium secondary batteries, and has an unique structure in which lithium ions are reversibly intercalated in the structures. For the application of all-solid-state batteries, multilayer thin films are requested to fabricate and it is important to control the microstructure of grains, interface structure, crystal orientation to provide the stable rechargeable properties. The crystal orientation and quality are influenced by the processing methods and the kind of substrate. In this study, LiMn₂O₄ thin films were deposited on the substrates by the chemical solution deposition method, and the interface structures were observed by HRTEM and Cs-corrected STEM. LiMn₂O₄ thin films were fabricated using [Li-Mn-O] metalorganic precursor solution. Ligand exchange reactions of the LiOCH(CH₃) ₂ and Mn(OC₂ H₄OC₂ H₄ ))_x with 2-ethoxyethanol was proceeded and the prepared [Li-Mn-O] metalorganic precursor solution was coated on the Al₂O₃ (0001) substrate and the Au film on the Al₂O₃ (0001) substrate. Epitaxial LiMn₂O₄ thin film was synthesized by heating the film at elevating temperature. The prepared samples were analyzed using a Cs-corrected STEM (JEM-2100F, JEOL Ltd) operated at 200 kV with a high-angle annular dark-field (HAADF) detector.Cross-sectional HRTEM image of the interface between LiMn₂O₄ and Al₂O₃ , LiMn₂O₄ and Au film on Al₂O₃ substrate showed that the interface orientation relationship are as follows; (111)LiMn₂O₄ is parallel to (0001)Al₂O₃ , (111)LiMn₂O₄ is parallel to (111)Au which resulted in the (111)LiMn₂O₄ planes growing parallel to the surface plane of Al₂O₃ or Au (111) on Al₂O₃ substrates. In addition, HAADF-STEM observations revealed the connectivity of the respective cations across the interface.

Energy storage is one of the main challenges of our time. Visions of future mobility and renewable energy all include new storage concepts. Among these Lithium-Ion-Batteries are one of the most promising candidates. Lithium-Ion-Systems are a prime example of host-guest chemistry. The lattices of graphite, oxides and phosphates provide a stable host structure from which Lithium ions and electrons can be reversibly exchanged. Different redox-systems can be combined, determining voltage and performance of the cell. Beneath the principal functionality of the electrochemical crystal system further factors as crystallite size and order-disorder phenomena may have a strong impact on the degree to which the theoretical values can be utilised. Morphological features as particle shape and size can influence process ability and thus the properties of the material in the electrode composite as a functional unit. On the way to higher energy densities the high-volt systems like nickel-substituted lithium manganese spinel or manganese and cobalt phospho-olivines are in the focus of science. Synthesis route and synthesis parameter have a strong influence on the physical, structural, chemical and electrochemical properties of the functional materials. In our contribution we will report on our current results on high-voltage cathode materials development with a special focus on morphological and structural aspects.

LiMn1.5Ni0.5O4-x (x = 0-0.05) is a high voltage cathode material for lithium ion batteries which has attracted great attention within the battery community due to its potential for high energy and power density. This compound can be ordered or disordered depending on the arrangement of Mn and Ni in the spinel structure. Its electrochemical properties are being widely studied in pursuit of optimal characteristics for high performance batteries. Many of the unanswered questions require understanding of the transport properties of the compound in order to be resolved. However, the transport properties are not well known, with only the electronic conductivity having been measured. Here we report the ionic and electronic conductivities and ionic diffusivity of ordered and disordered phases measured separately by using ion and electron blocking cell configurations. The measurements have been performed by direct current polarization technique and impedance spectroscopy on additive-free sintered samples. In order to elucidate the mechanistic understanding we measured the transport properties as a function of lithium content. We found that the electronic conductivity of the ordered phase increases with certain amount of lithium removal (electrochemically) after which the conductivity remains almost constant with lithium removal. Conversely, the disordered phase exhibits the opposite conductivity behavior, i.e. the conductivity decreases with lithium removal. The lithiated ordered and disordered phases exhibit the same order of magnitude of ionic conductivity and diffusivity. Measurements of partially delithiated phases are also in progress.

Energy storage is one of the key technologies for sustainable and clean energy future. Lithium-ion battery as an important energy storage technology has dominated mobile applications. New market for high power applications, e.g. hybrid electric vehicles and power tools, requires that electrodes can be operated at high current density, while current generation of lithium-ion batteries usually exhibit a poor rate performance due to slow diffusion of lithium ions in micron-sized particles of electrode. One approach to improve rate capability of intercalation electrode materials is to reduce the particle size of the electrode. By employing nanoparticulate electrodes, lithium ion diffusion length could be significantly reduced and thus the rate performance is improved. However, nano-sized electrode material tends to lose electronic contact during the lithium intercalation/de-intercalation, which is associated with volume expansion/contraction. Mesoporous electrode materials provide an ideal solution because they have ultra-high internal surface area, nano-sized walls, and micron sized particles. If a liquid electrolyte is used, the electrolyte could flood into the pores to offer a good contact between electrolyte and electrode, and thus fast lithium ion diffusion could be achieved. Nano-sized walls will ensure fast lithium ion intercalation/de-intercalation into/from the walls, while the overall particle size is still within a few microns, which will provide an excellent interparticulate contact within the electrode composite. Therefore, it is urgent to explore new opportunities in mesoporous solids as potential electrode materials. Here, we will demonstrate that the energy density of mesoporous Li-Mn-O spinel could be significantly improved by doping with nickel in the structure. It has been well documented that Ni-doped manganese oxides exhibit high redox potential as electrode materials for lithium-ion batteries. In our work, we fabricated two major types of nickel doped manganese oxides, NixMnO2 and LiNixMn2-xO4, with ordered mesoporous structure for the first time and investigate their electrochemical properties. This presentation will show the feasibility to nanomanufacture mesoporous cathode materials with 5V redox potential and ultrahigh power density. When it is coupled with a high-power and high-energy anode, a battery system with superior energy density and power density simultaneously could be achieved. Such a battery system will have great potential for a wide range of applications, such as electric vehicles. References: 1. Ren, Y., Armstrong, A. R., Jiao, F. & Bruce, P. G. Influence of Size on the Rate of Mesoporous Electrodes for Lithium Batteries. Journal of the American Chemical Society 132, 996-1004 (2010).

The study of the Li ion battery is attracted by many researchers because the electric vehicle and the plug-in hybrid vehicle need batteries with large energy density. Especially, the development of cathode materials with large energy density is important problem. The solid-solution type materials such as xLi2MnO3-1-xLiNi1/3Co1/3Mn1/3O2 are hot materials in these days. Those materials include the generation of oxygen gas at the first charge and indicate the change of crystal structure during cycling. These phenomenon will cause the deterioration of cycle performances due to the large volume change of the materials. On the other hand, the LiNi0.5Mn1.5O4 called as 5 V spinel is one the large energy density materials because the both redox reactions based on Ni2+/4+ at 5 V region and Mn3+/Mn4+ at 3V region indicate large energy density. However, the redox reaction at 3V region includes the change of crystal structure between cubic and tetragonal. Thus, the volume change causes the deterioration of the cycle performance. The using of nanostructured materials for Li ion batteries have been studied for the high power battery based on the short diffusion length of Li ion in the active material and large interface reaction places by the large surface area. In addition, the nanostructured materials have the effect of relaxation of volume change. It is considered that the nanomaterials are useful for the not only the high power battery but also large energy density battery. In this presentation, to fabricate LiNi0.5Mn1.5O4 and 0.5Li2MnO3-0.5LiNi1/3Co1/3Mn1/3O2 wire, the electrospinning method is used for the fabrication of nanomaterials because the method can easily obtain the wire structured cathode materials [1]. The precursor wires are obtained by spinning of polymer solution including metal salts due to applying the high voltage. And then, the precursor wires are converted into the metal oxides by the pyrolysis reaction. The resultant morphology of the LiNi0.5Mn1.5O4 and 0.5Li2MnO3-0.5LiNi1/3Co1/3Mn1/3O2 are hollow-wire structure with thin wall constructed by nanoparticles. The XRD, SEM and TEM images of those materials and charge-discharge curves and cycle performances of the Li ion batteries using the materials are shown in the presentation.

Research on rechargeable lithium ion batteries is approaching its 40th anniversary this year. The first batteries used LiAl anodes and TiS2 cathodes, 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 a result of the very low volumetric capacity of the carbon anode, and the inability to use much more than 60% of the lithium capacity in the layered oxides at practical rates. In 2005 SONY announced the first commercial cell using a tin-based anode with substantially enhanced volumetric energy density. However, this amorphous nano-sized material contains equimolar amounts of tin and cobalt making it too costly to be of practical use in large cells. The search is on for a similar material that is cobalt free. We have found that the cobalt can be replaced by iron, with the composition Sn2Fe. This material is also nanosized with the active material embedded in carbon. It shows comparable behavior to the SONY material. This promising behavior of this anode material will be discussed. On the cathode side, variations of the layered oxides still dominate in commercial cells, but the capacity has not exceeded around 170 Ah/kg at the C rate. There is a critical need to significantly increase the capacity. One way to accomplish this is by choosing a cathode that can react with up to two electrons, for example with two lithium ions or 1 magnesium ion. For insertion reactions this requires a transition metal ion that can undergo a two oxidation state reaction. Vanadium is one such metal, and vanadium oxides have been extensively studied. However, vanadium oxide lattices are not generally stable on cycling with the vanadium and lithium becoming randomized, as in Li3V2O5. The phase VOPO4 can form the compound Li2VOPO4, and we are presently building an understanding of its reversibility. Another compound of interest is the pyrophosphate, Li2FeP2O7, which we first reported on at the Montreal IMLB meeting. On paper, this material should allow the cycling of two lithium ions, but we found that only one lithium ion can be removed within the stability window of the electrolyte. The discharge capacity is around one lithium ion and is very stable over hundreds of cycles although there are some structural changes. The excess capacity observed on charging is related to electrolyte decomposition and to reactions with the carbon in the cathode. The future trends going beyond lithium ion will also be discussed, including metal-air. This work was supported by the US Department of Energy, the tin-iron and pyrophosphate work through the BATT program, and the tin-cobalt and vanadyl phosphate work through the NECCES-EFRC program.

Polyanion compounds represent an important type of alkaline metal intercalation compounds. Many chemical classes of polyanion compounds, such as phosphates, sulfates, borates and recently fluorosulfates and fluorophosphates, have been studied for their Li or Na ion intercalation chemistries. Recently, through our ab initio based high-throughput computing and screening¹, we identified that a new chemical class of compounds, carbonophosphates, are promising alkaline intercalation compounds². The carbonophosphate family consists of compounds containing phosphate and carbonate groups, with a formula A_xMPO₄CO₃. (A = Li or Na, M = transition metal). It is an extremely rarely studied chemical class, largely due to the absence of synthesis routes in literature. Before our work, only a few sodium carbonophosphates are reported as natural minerals. Here we report the synthesis and crystal structure characterization of multiple Na and Li carbonophosphates with various transition metals at M site. The sodium carbonophosphates are synthesized by hydrothermal method and the lithium compounds are obtained by performing Li-Na ion exchange with their sodium analogs. The influence of reaction temperature and concentration of starting materials on the formation of sodium carbonophosphates in hydrothermal reactions was systematically studied. The experimental results agree well with ab initio computed thermodynamical stability, and both results indicate that some transition metals prefer to form carbonophosphates while others do not. The application of the carbonophosphates as intercalation cathode materials in Li³ and Na-ion batteries are also studied and discussed. References: (1) Jain, A.; Hautier, G.; Moore, C. J.; Ong, S. P.; Fischer, C. C.; Mueller, T.; Persson, K. A.; Ceder, G. Computational Materials Science 2011, 50, 2295-2310. (2) Hautier, G.; Jain, A.; Chen, H.; Moore, C.; Ong, S. P.; Ceder, G. Journal of Materials Chemistry 2011, 21, 17147-17153. (3) Chen, H. L.; Hautier, G.; Jain, A.; Moore, C.; Doe, R. E.; Kang, B. W.; Wu, L. J.; Zhu, Y. M.; Tang, Y. Z.; Ceder, G. Chemistry of Materials 2012, 24, 2009-2016.

Batscap society, a Bolloré Technology&’s subsidiary, has recently marketed its lithium metal polymer (LMP) battery within the framework of the Autolib® project in Paris, the first electric-car-renting framework. This type of batteries proved its performances in matter of cyclability and security. This group is the only one who sells all-solid LMP batteries, with poly(ethylene oxide) (PEO) or its derivatives being part of the electrolyte and the cathode. As the automobile industry needs batteries offering always higher ranges, Batscap is very active in the research about new electrode materials. In the work which is here reported, the expertise of this group was made good use of in order to integrate a new promising electro-active material in the positive electrode of the battery: sulphur. We report here the specificities and the limitations that were encountered while optimizing the sulphur cathode composition, with respect to the PEO composition. Indeed, sulphur is known for reducing into polysulfides that are soluble in liquid and polymer electrolytes. This leads to a migration of the active material from the cathode to the electrolyte. Consequently, sulphur batteries suffer from poor reversibility. To understand the origin of these cyclability issues, we have carried out thorough microscopic studies on Li/S LMP batteries at various depths of discharge and charge, in order to study the microstructure evolutions of all the battery components. This revealed that sulphur dissolution leads to the creation of large voids in the electrode, compensated by a substantial volume increase of the PEO electrolyte. These processes cause the segregation of the polymer and eventually a collapse of the electrode. Our study also highlighted that the major issue that damages cyclability lies in the electrode collapse, much more than in the dissolution and the migration of the polysulfides. Consequently, it&’s urgent to prevent the degradation of the electrode morphology by enhancing its mechanical behaviour. Preventing from polysulfides dissolution is another way to maintain the electrode integrity. To conclude, the optimization of Li/S electrode can not be reached without dealing with the micro-structural evolution of the whole cell. To improve the cyclability performance of the Li/S LMP battery, we are therefore working on the optimization of the positive electrode composition. In order to outperform Li-ion system, we are targeting loadings of more than 50wt% of sulphur within the composite electrode, so that we are working on alternative solutions to the carbon matrix strategy. Different approaches will be presented, notably the utilization of some polymers but also other original attempts.

There is currently a great deal of interest in novel approaches to electrical energy storage including batteries and supercapacitors for transportation and grid applications. We present a new breed of materials, based on redox-active substituted (RAS) conducting polymers (CPs) that could potentially provide: high energy and power density, high conductivity, long-term durability, and low cost. The development of these CP materials is guided by a systematic approach to design and screen promising materials using computational methods, followed by the synthesis of “hits”, electrochemical and device level characterization of the most promising materials. In the present work we have modified CPs (e.g. 3,4-polyethylenedioxythiophene (PEDOT)) by covalently binding small RAS like N1,N1,N4,N4-tetramethylbenzene-1,4-diamine (TMPD). The addition of this pendant gives rise to a dramatic increment in the energy density of the material, by increasing the number of electrons transferred per monomer unit. Monomers were then electropolymerized onto both analytical electrodes (for in-situ characterization) and current collectors (for device level characterization) to be studied in detail. In-situ spectroelectrochemistry, both ultra-violet visible and Raman spectroscopy, has yielded important mechanistic information about the electrochemical reactions undertaken by the RAS-CP materials, which directly affect device performance. Electrochemical quartz crystal microbalance (EQCM) studies have helped elucidate the ion transport and swelling in the RAS-CP films upon electrochemical cycling. Moreover, device level characterization has been done, and at high charge/discharge rates of 1C the capacity of our materials is 100 mAh/g. To the best of our understanding, this represents the highest capacity achieved, to date, by purely organic CP materials. Combining the attractive capacity of 100 mAh/g with an average operating voltage of 3.9 V vs Li/Li+, yields a material that has an energy density of 390 kWh/g. Furthermore, the electropolymerized RAS-CP electrodes only contain active material electrodeposited on the current collectors, precluding the need for both binder and conducting additives (i.e. carbon), making these materials extremely attractive for next generation devices.

Open framework solids are attracting increasing attention due to their wide applications including battery electrode, proton conductor, hydrogen-storage container, wide bandgap semiconductor and catalyst. In order to improve the overall performance of Li-storage materials, structural expansion is a desirable strategy to construct facilitated Li-ion migration channels. In the past decades, numerous efforts have been focused on the structural expansion of metal oxides, e.g. manganese (from spinel LiMn2O4 to hollandite MnO2) and titanium (from anatase to TiO2(B)) based compounds. Most recently, the discovery of tavorite-based polyanion frameworks is also a striking progress with moderate expansion of Li-ion channels compared with olivine LiFePO4, where the narrow channels are easy to be blocked. Indeed, either larger reversible capacity or better rate performance can be achieved in view of the potential modification of Li reaction mechanism. Moreover, open structure materials provide new opportunity for future research on Na and Mg batteries. Fluoride is a potential cathode alternative for Li batteries due to its higher ionicity of metal-fluorine bonds compared with their oxide counterparts (e.g. from 1.5 V in Fe2O3 to 3 V in FeF3). Owing to the much smaller weight of F (19) than of the polyanion (e.g. 95 for (PO4)3-), fluorides are expected to have a larger theoretical capacity even if referring to 1e- transfer, e.g. 237 mAh/g for FeF3. Another advantage is the possible utilization of conversion reaction at high voltage, and much larger capacity is achievable in view of multi-electron reaction. Recently, we successfully expanded the cell volume of iron fluoride to a value that is 2-4 times as large as that of the commercially available ReO3-type FeF3.[1-3] These hydrated fluorides exist as hexagonal-tungsten-bronze-type (HTB) or pyrochlore phases, characterized by 1D or 3D cation-insertable open channels and extended solid-solution reaction region. References: [1] C. L. Li, L. Gu, S. Tsukimoto, P. A. van Aken, J. Maier, Adv. Mater. 22 (2010) 3650-3654. [2] C. L. Li, L. Gu, J. W. Tong, S. Tsukimoto, J. Maier, Adv. Funct. Mater. 21 (2011) 1391-1397. [3] C. L. Li, L. Gu, J. W. Tong, J. Maier, ACS Nano 5 (2011) 2930-2938.

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 expansion. The ALD coating enabled stable cycling at C/2 (charge / discharge in 2 hours) with a capacity of ~ 900 mAh/g. Furthermore, rate capability studies showed the ALD-coated electrode maintained a capacity of 600 mAh/g at 5C (charge / discharge in 12 minutes¹. For uncoated electrodes it was only possible to observe stable cycling at C/10 (charge / discharge in 10 hours). Also, we have recently explored the fabrication of a binder-free LiNi_0.4Mn_0.4Co_0.2O₂ cathode containing 5 wt.% carbon single-walled nanotubes (SWNTs) as the conductive additive and demonstrated stable high rate capability, at 10C (charge / discharge in 6 minutes)². By then coating the LiNi_0.4Mn_0.4Co_0.2O₂/SWNT cathode with Al₂O₃, we were able to cycle the cathode up to 4.7 V vs. Li/Li+with much less degradation. Finally, we coated a separator and enabled stable cycling in a high dielectric electrolyte that could better enable exploratory electrode materials³. 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) Ban, C. M.; Li, Z.; Wu, Z. C.; Kirkham, M. J.; Chen, L.; Jung, Y. S.; Payzant, E. A.; Yan, Y. F.; Whittingham, M. S.; Dillon, A. C. Adv. Energy Mater 2011, 1, 58 (3) Jung Y, Cavanagh A, Gedvilas L, Widjonarko N, Scott I, Lee S, Kim G, George S, and Dillon A, Adv. Energ. Mater, doi: 10.1002/aenm.201100750

A rapid, pulsed sonochemical process has been developed for depositing Al2O3 and AlF3 coatings on the surface of0.5Li2MnO30.5LiNi0.44Mn0.31Co0.25O2 cathodes for lithium-ion battery applications. By tuning the ultrasonic intensity, the morphology of pristine secondary micron sized particles was preserved, as confirmed by scanning electron microscopy. Energy dispersive X-ray mapping analysis revealed that the overall surface of the cathode particles was coated by Al2O3 and AlF3. It has been reported that such coatings may serve as buffer zones between the acidic species in standard electrolyte solutions containing LiPF6 and the active cathode mass, yet allowing easy transport of Li+ ions in and out of the cathode structure.1 In this presentation, the electrochemical, structural, compositional and morphological properties of the above-mentioned products will be described. For example, at room temperature, a pristine, uncoated cathode delivered an initial discharge capacity of 200 mAh/g, while coated Al2O3 and AlF3 electrodes delivered 220 and 240 mAh/g, respectively, when charged and discharged between 4.6 and 2.0 V at a current density of 15mA/g current density. By comparison, at 55 C, using the same current rate and voltage window, the pristine and Al2O3- and AlF3 coated cathodes delivered initial discharge capacities of 270, 320 and 275 mAh/g, respectively. A comparison of the cycling stabilities of the various electrodes will be made. Reference (1) H. Sclar, O. Haik, T. Menachem, J. Grinblat, N. Leifer, A. Meitav, S. Luski, and D. Aurbach J. Electrochem. Soc. 2012, 159, A228 Acknowledgements: This research was supported by the Center for Electrical Energy Storage - Tailored Interfaces, an Energy Frontier Research Center funded by the Office of Basic Energy Sciences, Office of Science of the U.S. Department of Energy.

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 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 the electrodes volume reconstruction using Focus Ion Beam all these modifications will be discussed making the link between changes occurring at the atomic level and those taking place at the scale of the whole electrode. (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.

Possessing high efficiency, high energy density, and design flexibility, lithium ion batteries have wide applications including portable electronics, electric vehicles, and grid energy storage. For future applications of lithium ion batteries, doping of multi-valence transition metal ions into the cathodes have been identified as a potential approach to achieve the increased voltage and energy density needed for heavy duty applications. However, it unclear how the dopants distribute in the complex materials and what role they play in controlling the lithium transport properties within the cell. We have used atomic scale Z-contrast imaging, electron energy loss spectroscopy, and 3-D X-ray energy dispersive spectroscopy tomography to characterize the structure, cation segregation, and phase of this material. In-situ and ex-situ TEM study of the structure changes and phase transformation during charge/discharge cycles have been performed using a half-cell design in an aberration corrected TEM. The layered structure has been found to transform to LiMn2O4-type spinel structure after cycling in the Li-ion batteries. The detailed transformation process has been examined using in-situ and ex-situ TEM techniques. The layered structure to spinel transformation reveals the fading mechanism of the layered cathode. We have concluded that many of the limitations in the properties of Li-ion batteries using this cathode material come from the materials synthesis issues as well as from phase transformation within the battery. Incorporating synthesis routes and dopants that will overcome the cation segregation and phase transformation can go a long way to satisfying the requirements for the next generation batteries that can potentially accelerate use of electric vehicles.

Local structural changes in Li-rich “layered-layered” xLi₂MnO₃ * (1-x)LiMO₂ (x=0.6, M=Mn_0.4Ni_0.4Co_0.2) cathode system were investigated by X-ray Absorption Spectroscopy (XAS). Our data revealed that there is no solid solubility between Li₂MnO₃ (C2/m) and LiMO₂ (R-3m) components of cathode. In addition, both components respond independently to the electrochemical extraction and re-insertion of lithium. Lithium removal from Li₂MnO₃ component occurs with simultaneous loss of oxygen giving rise to formation of disordered R-3m type structure. Li⁺ thus extracted is replaced by H⁺ formed due to electrolyte decomposition. Subsequent lithium re-insertion proceeds by Li⁺ - H⁺ exchange reaction giving rise to formation of structure that is similar to Li₂MnO₃ but lithium and oxygen deficient. The average valence state of Mn in Li₂MnO₃ remains unchanged from 4+. On the contrary, LiMO₂ component exhibits conventional redox processes attributed to Transition Metal (TM) ions, Mn, Ni and Co. Lithium removal from LiMO₂ component converts original O3 phase (R-3m) to O1 phase (P-3m1) which is poorly reversible upon lithium re-insertion. Systematic variation in TM-O bond lengths confirms the charge compensation by TM ions during lithium extraction and re-insertion processes.

The key to the success of electric vehicles (HEV, PHEV, and EV) and large-scale power backups for renewable energy lies in the advancement of rechargeable batteries. While the performance of batteries is critically dependent on the electrode material, recent studies [1-4] have shown that layered Li-excess metal oxide is one of the most promising cathode materials with the highest energy density for next-generation Li rechargeable batteries. This is due to its exceptionally high lithium storage capacity that exceeds the theoretical capacity of conventional cathode materials. However, despite its high energy density, its usage in practical batteries has been limited because of the low power capability and stability. To address these issues, we focused on the chemical and morphological changes that occurred at the surface of the layered Li-excess metal oxide cathode (x Li2MnO3#9679;(1-x) LiMO2, (M = Ni, Mn), LLNMO) during electrochemical cycling. It was recently reported that the abnormally high capacity of LLNMO originated from simultaneous extraction of lithium and oxygen from the crystal followed by a structural change of the LLNMO. [1, 3, 4] While the overcapacity of LLNMO indispensably accompanies the significant amount of oxygen extraction from the structure, the effects of evolved oxygen on the electrochemical system are not well understood. Recent studies on Li-air batteries revealed that oxygen can react with the conventional carbonate-based electrolyte during battery operation.[5] Here, the detailed reaction scheme following oxygen evolution was established using real-time gas analysis and ex situ chemical analyses on the surface of the electrodes. A series of electrochemical/chemical reactions involving oxygen radicals constantly produced and decomposed lithium carbonate on the electrode surface during cell operation. Moreover, byproducts, including water, affected the cycle life and rate capability: hydrolysis of the electrolyte salt formed hydrofluoric acid that attacked the electrode surface and resulted in severe manganese dissolution. This finding implies that protection of the electrode surface from damage, e.g., by a coating or removal of oxygen radicals by scavengers, will be critical to widespread usage of Li-excess metal oxide in rechargeable lithium batteries. References [1] Xu, B.; Fell, C. R.; Chi, M.; Meng, Y. S., Energy & Environmental Science 2011, 4, 2223. [2] Armstrong, A. R.; Holzapfel, M.; Novak, P.; Johnson, C. S.; Kang, S.-H.; Thackeray, M. M.; Bruce, P. G., Journal of the American Chemical Society 2006, 128, 8694. [3] Hong, J.; Seo, D.-H.; Kim, S.-W.; Gwon, H.; Oh, S.-T.; Kang, K., Journal of Materials Chemistry 2010, 20, 10179. [4] Yabuuchi, N.; Yoshii, K.; Myung, S.-T.; Nakai, I.; Komaba, S., Journal of the American Chemical Society 2011, 133, 4404. [5] Freunberger, S. A.; Chen, Y.; Peng, Z.; Griffin, J. M.; Hardwick, L. J.; Barde, F.; Novak, P.; Bruce, P. G., Journal of the American Chemical Society 2011, 133, 8040.

Lithium-rich layered oxide materials having chemical formula Li_1+yM_1-yO₂(M=Co, Mn, and Ni) are among the most promising high capacity and high voltage cathode materials and considered to be the potential candidates for lithium-ion batteries in electric vehicles (EVs). However, after repeated charge/discharge cycles, voltage drop is observed. Additionally, rise in impedance is observed during high voltage hold. These issues still remain elusive, which prohibits these cathodes to be utilized in EVs. These unusual properties are related to the cluster formed and/or alternation of atomic arrangement in the host structures during electrochemical delithiation/lithiation, which introduces new phases in the material. The present work focuses on tracking down those new and undesired phases in layered Li_1.2Co_0.1Mn_0.55Ni_0.15O₂ (0.5Li₂MnO₃-0.5LiNi_0.375Co_0.25Mn_0.375O₂ in two component systems) by diffraction and magnetic studies. The electron (X-ray) diffraction are correlated with the magnetic responses to monitor the phase transformation pathways during repeated cycling and prolonged hold period at high voltage ( ge; 4.5 V ). Briefly, the results from diffraction studies reveals the parent compound consists of both layered rhombohedral and monoclinic phase. The magnetic susceptibility data conforms paramagnetic nature of starting material above T > 100 °K, obeying Curie-Weiss law with T_c =75 °K. The magnetic ordering bellow T_c confirms the presence of monoclinic Li₂MnO₃ phase. Comparison of theoretical effective magnetic moments with the experimental effective magnetic moment calculated at paramagnetic region from inverse magnetic susceptibility data suggests the presence of Ni⁺² (HS/LS), Mn⁺⁴ (HS/LS), and Co⁺³(LS) in the host structure. At high voltage (4.5V) charged state, the magnetic ordering disappears which suggest the subsidization of monoclinic phase in the structure. The experimental effective magnetic moment decreases confirming the oxidation of oxidation of Ni⁺² (S=1) to Ni⁺³ (LS, S=1/2)/ Ni⁺⁴ (LS,S=0). However, after prolonged holding period, increase in effective magnetic moment is observed, which indicates the change in oxidation sates of transition metal ions during high voltage hold. Slope of M(H) curve at T =5K shows the increase in ferromagnetic character during holding duration which is in agreement with the susceptibility data. This indicates the metal ion (Ni⁺²) migration to the lithium site which may create 180° Ni⁺²-O-Mn⁺⁴ ferromagnetic interaction. The detailed analysis correlating with the electrochemical performances will be presented. Acknowledgements: This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725, was sponsored by Vehicle Technologies Program for the Office of Energy Efficiency and Renewable Energy.

We introduce the phase evolution mechanism regarding to the formation of xLi2MnO3(1-x)LiNixCoyMnzO2 to obtain the ultra-high capacity cathode materials by increasing the Li content. The structural phase change using the computer simulation and experiment was analyzed. The first principles calculation shows that both layered Li2MnO3 and LiMeO2 components formed as a stable form, and the formation of LiMeO2 is favorable prior to Li2MnO3 that gives ultra-high capacity as increasing Li content. This is because the metal component in LiMeO2 maintains the chemical valence of +3. The remained Mn-rich part forms Li2MnO3 via LiMn2O4 spinel-like as the Li content increases. Moreover, in the presence of excess Li, surface coating using AlF3 shows more stable spinel structure at the surface during charge/discharge procedure and improved the electrochemical properties. This research shows reliable approach to examine uncertain mechanism that can impact on the electrochemical performance of new ultra-high capacity cathode material development.

The high theoretical specific energy of the Li-Air(O2) battery has encouraged intensive investigation of the underlying science in order to address the formidable challenges facing the practical realisation of such a device. Li-Air batteries based on aqueous and non-aqueous electrolytes are known. The non-aqueous O2 redox chemistry that takes place at the cathode in the non-aqueous Li-Air(O2) cell is, in many ways, the defining feature of the battery. A truly rechargeable non-aqueous Li-O2 cell depends on O2 being reduced at the cathode to form Li2O2 upon discharge, with the process being completely reversed on charge, and sustainable on cycling. The reactions that take place at the cathode in several electrolytes will be discussed, as will the implications of the results for the realisation of a rechargeable Li-Air(O2) cell.

Li-oxygen batteries are a potentially transformative alternative to traditional Li-ion batteries due to their extraordinarily high specific capacity. However, before this technology can move from the lab bench to the commercial arena, a number of challenges need to be overcome. One aspect of the Li-oxygen system that is poorly understood is the mechanism of charge transport in the insoluble discharge product, lithium peroxide (Li2O2). Because Li2O2 is a bulk insulator, it has been suggested that poor charge transport results in significant performance limitations in Li-oxygen cells. However, the discharge product is not a perfect crystal and will likely contain many imperfections. Here we use density functional theory (DFT) to investigate charge transport pathways associated with two types of imperfections: point defects and surfaces. We have performed a comprehensive study of intrinsic point defects in Li2O2, and find that small hole polarons are the dominant defect in terms of charge transport. Despite the low barrier for hole polaron migration, the associated conductivity may be limited by the concentration of polarons. We have also used DFT to identify the low energy surfaces of Li2O2. For the basal surface, the presence of polaron-like distortions suggests that the conductivity near this surface may be several orders of magnitude larger than that in the bulk. For the other low-energy surfaces, we find evidence for a significant reduction in the band gap relative to the bulk.

Metal-air batteries offer the opportunity for unprecedented energy densities relative to today&’s state of the art battery technologies. One of the most challenging issues preventing the implementation of metal-air systems is the slow oxygen reduction kinetics at the battery cathode. A novel three-component composite electrode consisting of a carbon (C) current collector with conductive polymer (cp) and silver (Ag) coatings has been developed. The composite electrode fabrication strategy will be described and the composite electrode will be evaluated as a cathode for non-aqueous oxygen reduction. Extension of this fabrication strategy to the preparation three-dimensionally structured C-cp-Ag composites, yielding composite electrodes with high oxygen reduction activity will be discussed. Improvement of cathode oxygen reduction activity will increase current capability and power output of metal air batteries, facilitating future development of small, lightweight, long-life power sources.

Conversion mechanism-based transition metal oxides are promising anode materials in Li-ion batteries due to its high capacity, compared with graphite. MnO2 has the largest theoretical capacity among all the alternative oxides, but the low experimentally achieved capacity and the rapid capacity fading hinder its commercial utilization. In our work, we achieved both high capacity and good cyclability by using three-dimensional electrodes. Carbon nanotubes were vertically grown on stainless steel meshes by a chemical vapor deposition method. MnO2 was deposited on the surface of nanotubes, which were additionally coated by carbon layers. This sandwich structure provides paths for rapid charge transfer without large losses and protects the MnO2 from side reactions by electrolytes.

Sulfur cathodes offer an order of magnitude higher capacity (theoretical capacity: 1,675 mAh/g) than the conventional cathodes based on lithium insertion compounds. However, the commercialization of rechargeable lithium-sulfur batteries is hampered by (i) poor cycle life due to the dissolution of the polysulfide intermediates (Li2S8, Li2S6, and Li2S4) formed during the charge-discharge process and (ii) low electrochemical utilization of sulfur cathodes due to the high insulating nature of sulfur and the discharge products Li2S2/Li2S. To overcome these difficulties, this presentation will provide an overview of a series of composite cathodes with unique nanostructures that improve the electrical conductivity and utilization of active materials as well as the fabrication of scalable, binder/current collector-free, nanostructured sulfur-carbon nanotube (S-CNT) composite cathodes without employing toxic solvents during electrode processing. For example, sulfur-carbon nanocomposites synthesized by a scalable in situ sulfur deposition route exhibit much better electrochemical performance than pristine sulfur. Similarly, sulfur-polypyrrole composites in which the sulfur particles are coated by a nanolayer of polypyrrole show improved capacity and cyclability. Binder/current collector-free, nanostructured S-CNT composite cathodes exhibit excellent capacity retention at high rates, e.g., >1,000 mAh/g capacity after 50 cycles at 1C rate. A novel lithium-sulfur battery structure with an interlayer between the separator and the cathode to capture the polysulfide ions exhibits significantly improved energy and power. These materials and strategies can enable packaged cells with an anticipated energy density two times higher than those of current lithium-ion batteries.

Reaction type systems such as the Li-S battery have the potential to increase both the discharge capacity and cyclability over ubiquitous intercalation Li-ion batteries. The biggest challenge of the Li-S battery system is developing a sulfur-containing, conductive cathode which exhibits high surface area for increased reactivity of insulating sulfur as well as lithium polysulfide retention for enhanced cyclability. We have synthesized modified, mesoporous conductive carbons which contain sulfide moieties in order to achieve both of these goals. The lithium polysulfide intermediates traditionally lost to electrolyte during cycling are better retained within the sulfur-modified carbons than in nearly identical carbon pores with no sulfur modification. In this work, the effectiveness of S-containing mesostructured carbon materials in a reaction type Li-S battery is shown versus unmodified porous carbons and high surface area carbon cathodes.

Rechargeable batteries with high energy density are desired to solve imminent energy and environmental issues. In state-of-the-art Li-ion batteries, the energy density is mainly limited by the specific capacity of electrodes. For example, current metal oxide and phosphate cathodes possess an intrinsic capacity limit of ~300 mAh/g. In contrast, Li2S cathode has a theoretical specific capacity of 1166 mAh/g, which is five times more than current cathode materials. Consequently, the specific energy of Li2S-based full cell is about three times that of current technology. Moreover, Li2S cathode can also avoid issues of low coulomb efficiency and safety of lithium anode in Li-S battery. However, Li2S is both electronically and ionically insulating, which makes it inactive towards electrochemical reactions. In this talk, we will present two strategies to activate Li2S cathode and specific capacity around 800-900 mAh/g is achieved. In the first approach, we synthesize Li2S/carbon nanocomposites to improve the kinetics of Li2S. Two kinds of composites are made, including mesoporous carbon-trapped Li2S and hollow carbon nanofiber-encapsulated Li2S. In these composites, the transport distances for Lithium ions and electrons are as small as 10-20 nm. Consequently dramatically improved performances are achieved. The first discharge capacities are as high as 900-950 mAh/g in both composites and the capacities are stabilized at 500-600 mAh/g after 20 cycles. The capacity retention is 65% per 100 cycles. In addition, the voltage hysteresis between charge/discharge is only 0.2 V at C/5. In the second approach, we develop a simple and scalable method to activate even 10 um-sized bare Li2S particles. It is discovered that a large potential barrier (~1 V) exists at the beginning of charging for Li2S. By applying a higher voltage cut-off only in the first charging, this barrier can be overcome and Li2S become active. No overcharging is needed in following cycles. The voltage profile is similar to sulfur cathode and the voltage hysteresis is as small as 0.2 V. The initial discharge capacity is greater than 800 mAh/g even for 10 um Li2S particles. Moreover, after ten cycles, the capacity is stabilized around 500 - 550 mAh/g with a capacity retention of 75% per 100 cycles. The origin of the initial barrier is found to be phase nucleation of polysulfide, but the voltage barrier amplitude is mainly due to charge transfer and lithium ion diffusion in Li2S. This approach is compatible with traditional battery fabrication and demonstrates a feasible approach to utilizing Li2S as the cathode material for rechargeable lithium ion batteries with high specific energy. References: 1. Yang, Y. et al., New Nanostructured Li2S/Silicon Rechargeable Battery with High Specific Energy. Nano Letters 10, 1486-1491 (2010) 2. Yang, Y. et al., High Capacity Micron-sized Li2S Particles as Cathode Materials for Advanced Rechargeable Lithium Ion Batteries, submitted to JACS

In view of limited resources for raw materials and energy, energy-storage systems have moved into the center of interest, batteries certainly being the most prominent ones. Among the most promising element combinations for the next generation of batteries is lithium/sulfur. Due to the insulating nature of sulfur, the cathode of Li/S batteries must contain an additional conducting additive, e.g., carbon black, in combination with a binder and a non-aqueous electrolyte, e.g., carbonates or ethers, to ensure for a complete contacting of sulfur. Starting from elemental sulfur, i.e. from S8, the electrochemical reduction cascade finally leads to poly(sulfide)s, Sx2-, which are soluble in the chosen electrolyte for at least xle;3. Consequently, diffusion of active cathode material, i.e. of poly(sulfide)s to the anode occurs, resulting in the formation of Li2S at the lithium surface and a sometimes dramatic loss in capacity. One concept for poly(sulfide) retention is to embed sulfur inside a cyclized poly(acrylonitile) (PAN) structure by heating PAN and elemental sulfur to >300°C.1 In course of this procedure, the sulfur dehydrogenates PAN, which forms cyclic structures with a conjugated π-system. Nevertheless, the main question how the sulfur is embedded into the cyclic PAN-derived network has not been answered satisfactorily. Two different PAN/sulfur composites, i.e. SPAN and ScPAN have been synthesized using a one and a two-step synthetic approach, respectively. In all composites, any remaining elemental sulfur was removed via extraction with toluene. TOF-SIMS, XPS and FT-IR experiments strongly suggest that in all composites the sulfur is exclusively covalently bound to carbon and not to nitrogen. Moreover, N-C-S- fragments, most probably resulting from 2-pyridylthiolates as well as Sx (xge;2) and thioamide fragments, have been identified by TOF-SIMS. A structure for the composite has been presented that explains for all analytical data as well as for the entire electrochemistry observed. A sulfur balance carefully established during discharge strongly suggests that the polymer backbone, which most probably consists of a conjugated π-system, significantly contributes to the initially measured capacity. In summary, our investigations allow for elucidating and correlating the structure of sulfur-poly(acrylonitrile)-based Li-sulfur batteries with the electrochemical performance of such devices. Apart from the poly(acrylonitrile)-derived backbone, thioamide as well as poly(sulfide) structures are proposed. This way, a comprehensive picture of the chemistry and electrochemistry of Li-sulfur batteries is presented. References 1. J. Wang; J. Yang; J. Xie; X. Naixin. Adv. Mater. 2002 (14) 963. 2. J. Fanous, M. Wegner, J. Grimminger, Auml;. Andresen, M.R. Buchmeiser Chem. Mater. 2011 (23) 5024.

Developments in the electricity industries, such as portable electronics, plug-in hybrid vehicles, and power tool technologies, have increased interest in energy storage over the past few years. Among the various energy-storage technologies, lithium-sulfur batteries have been intensively investigated as one of the most promising systems for the next generation high-energy rechargeable lithium batteries because of their high theoretical specific capacity (1680 mA h/g) and energy density (2500 Wh/kg). However, although this system has been gaining attention, it has not been commercialized because of remaining unsolved problems, such as the inherent poor electrical conductivity of sulfur, the shuttle effect of higher-order polysulfides during charging, and the rapid decrease in capacity during cycling. In this study, we prepared a sulfur-coated microporous (S-MIP) carbon composite using two impregnation methods (S-impregnation and S-pore filling method) and investigated the S structural changes through those mythologies. We found that the polycrystalline structure of elemental sulfur showed a structural change to amorphous phase in the S-MIP carbon composite prepared by S-impregnation process. From the porosity data, S-impregnated MIP carbon showed around 500 m2 /g of BET SSA and a pore volume of 0.2 cm3 /g, which could provide the room or reaction sites for polysulfide during battery operation due to homogeneous amorphous mixed phases of the MIP carbon and sulfur. The best discharge capacity was obtained with a S-MIP carbon by S-impregnation method, resulting in 680 mAh/g after 50 cycle at a 0.1C rate, which was ~47 % higher than that by S-pore filling method.

The lithium-sulfur (Li-S) battery has attracted increasing attention as a next-generation energy storage device for plug-in hybrid electric-vehicles and electric vehicles, owing to its extremely high theoretical specific capacity and energy density. However, one of the critical problems for lithium-sulfur batteries is the diffusion of polysulfide, resulting in fast capacity fading and low coulombic efficiency, which hinders its widespread application for this secondary rechargeable lithium battery system. In this talk, we present for the first time using new hierarchical three-dimensional mesoporous functionalized carbon as sulfur immobilizer for lithium-sulfur cathodes. The as-prepared new functionalized carbon material has strong interaction with sulfur and polysulfide through chemical bonding that can significantly inhibit the diffusion of lithium polysulfide in the electrolyte, leading to high capacity retention and high coulombic efficiency. The important role of this new carbon can be extended to various carbon materials for the development of other high performance carbon-sulfur composites as cathodes materials.

Batteries for use in small consumer devices have saturated society; however, if they are ever to make the transition into large-scale applications like automotive transportation or grid-storage, new materials with drastically improved performance must be developed. With this urgent need, all efforts must focus on using Earth-abundant and non-toxic compounds so that, whatever the developments made, they can be implemented in a sustainable way. Within such context, polyanionic compounds based on either SiO4^4-, PO4^3- or SO4^2- are being the subject of very intensive research as they markedly present benefits in terms of safety or cost. Herein, we describe a general strategy for the design and elaboration of sustainable insertion electrode materials. We have explored, based on the inductive effect concept, the feasibility of preparing F-based polyanionic materials; we have synthesized at low temperature a new family of Li-bearing fluorosulphate compounds of general formula A_xMSO₄F (A=alkali, M=3d metals) presenting a rich crystal chemistry [1-3]. Practically unknown two years ago, the fluorosulphate family presently counts no less than 18 members which display, depending upon the nature of M or A, a rich crystal chemistry; among them LiFeSO₄F which crystallizes depending upon the synthesis conditions in either a tavorite or triplite phase. Triplite LiFeSO₄F, which can now be made in less than 20 minutes at 300°C, shows the highest Fe³⁺/Fe²⁺ redox potential ever reported for Fe-based polyanionic compounds; it has a theoretical energy density of 588 Wh/kg, which is slightly greater than LiFePO₄ (578 Wh/kg), while also showing positive attributes in terms of synthesis with no need for carbon coating or nanosizing particles [4-6]. Similarly, members of the KMSO₄F (M=Co, Ni, and Fe) were found to display a rich redox electrochemistry that we will describe as well [7]. For reasons of environmental friendliness we also searched for F-free sulphate compounds and discovered [8] a new phase, Li₂Fe(SO₄)₂, which displays an open circuit voltage of 3.83V vs. Li⁺/Li⁰. The origin of such high voltages will be discussed in terms of secondary effect, and novel synthesis approaches of sulfates introduced. _{[1] Recham N, et al. “Nature Materials”, 9, 68-74, 2010. [2] Barpanda P, et al. “Journal of Materials Chemistry”, 20, 1659-1668, 2010. [3] Reynaud M, et al. “Solid State Sciences”, 14, 15-20, 2012. [4] Barpanda P, et al. “Nature Materials”, 10, 772-779, 2011. [5] Ati M. et al. “Angewandte Chemie International Edition”, 50, 10574-10577, 2011. [6] Ati M, et al. “Electrochemistry Communications”, 13, 1280-1283, 2011. [7] Recham N et al. “JACS” Submitted [8] Reynaud M, et al. “Electrochemistry Communications”, 2012}

Spurred by the enormous needs in electricity storage devices, the search of new materials for lithium-ion batteries has received much attention in the recent years [1]. Among the noticeable advances, the introduction of cathode materials based on polyoxoanionic species such as phosphates e.g. LiFePO4, pyrophosphates or more recently sulphates (LiFeSO4F) [2] seems to be one of the most promising. In this presentation, we will report on some very recent molecular dynamics work on LiMgSO4F (a structural analog of LiFeSO4F) aiming at evincing the conduction mechanism of this material. In this work both Density Functional Theory (performed with the CPMD code) and Molecular Dynamics (MD) calculations were used. The DFT calculations were used to parameterize interionic potentials used for the MD simulations. The interionic potential for LiMgSO4F was tested by reproducing the experimental data available for this material. Very good agreement was found for the structural properties, such as lattice parameters, bond distances and the regions of maximum occupancy of the Li+ ions. The ionic conductivity was calculated next and the results obtained at high temperature are consistent with the experimental data. Next, the conduction mechanism was studied in detail. One of our main findings is that the diffusion of the Li ions occurs via strongly correlated hops inside diffusion channels. This finding implies the non-validity of the Nernst-Einstein relationship for this system with correlated motion and has also important technical consequences, discussed in this presentation. [1] M. Armand, and J. M. Tarascon, Nature 451, 652 (2008). [2] N. Recham et al., Nat Mater 9, 68 (2010).

Aliovalent substitution of LiFePO₄ has been indicated as beneficial for its electrochemical performance. Nevertheless, the effect of such substitution on the reaction mechanism and thermal stability remains unexplored. We have previously shown that by controlled reaction process it is possible to incorporate up to 10 mol. % of vanadium into LiFePO₄ structure at either iron or Li site. Here we have investigated structural changes accompanying the chemical and electrochemical lithiation and delithiation, and the kinetics of these processes by in-situ and ex-situ x-ray diffraction (XRD) and absorption, and electrochemical methods. Thermal stability of the partially delithiated phases was studied by in-situ XRD upon heating up to 800 ° C. The GITT measurements show that vanadium substitution at the Fe site results in a faster kinetics compared to the unsubstituted LiFePO₄, while placing V at the Li site results in much slower kinetics. XRD shows vacancy formation at the Li site or at the Fe site, when V is substituted at each of these sites, respectively. Also, vanadium substitution reduces the lattice mismatch between the lithiated and the delithiated olivine phases. Both factors are beneficial for the faster lithiation/delithiation kinetics. The effect of vanadium substitution on the limits of Li_xFePO₄ solid solution upon electrochemical lithium cycling or temperature increase will also be discussed. This research is supported as part of the Northeastern Center for Chemical Energy Storage, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Basic Energy Sciences under Award Number DE-SC0001294.

LiFePO4 is one of the most promising cathode materials for lithium-ion batteries. Nevertheless, the phase transition mechanism in LixFePO4 has not yet been fully clarified. Padhi et al. hypothesized that lithium insertion proceeds from the surface of the particle moving inwards behind a two-phase interface, and propounded the so-called “shrinking-core” model. The “shrinking-core” model implies that the diffusion of lithium occurs isotropically, although lithium mobility and other properties of LiFePO4 are anisotropic. Chen et al. imaged chemically delithiated plate-like LiFePO4 particles by electron microscopy and observed cracks in the b-c plane between LiFePO4 and FePO4. They proposed that the deintercalation-intercalation of lithium proceeds along the b axis in the interface region with concomitant movement of the phase boundary along the a direction. A similar model was proposed by Laffont et al. who conducted an electron energy-loss spectroscopy study. Delmas et al. also confirmed the anisotropic “moving phase boundary” model. They reported that the growth reaction is considerably faster than its nucleation, and proposed the “domino-cascade” model. The previously reported ex situ methods, however, may not always track the dynamic phase transition because it presumes the mechanism using the information on the relaxed state after the reaction. In this work, we conducted in situ time-resolved XAFS and XRD measurements and studied the dynamic behavior of the LiFePO4/FePO4 phase transition. From Fe K-edge XAFS, the phase fraction change of Li-rich phase (LFP) and Li-poor phase (FP) can be estimated. The phase fraction from XAFS was well consistent with that estimated from the electrochemical charge current. This means in situ cell works well and can be used to investigate phase transition under battery operation conditions. The XRD data was collected during the 1C charge reaction of 60 nm LiFePO4. Before the in situ XRD measurement, the cell was charged slowly to 3.35 V, which is near the plateau potential of LiFePO4/FePO4. This treatment can exclude the influence of the single phase reaction for the LFP phase. At this composition, only a merged peak at 19.15 degree from LFP (211) and (020) was observed. During the charge reaction, new peaks appeared at 19.5 and 19.9 degrees which correspond to FP (211) and (020), respectively. This result indicates that the two-phase reaction proceeds in the 1C charge rate. Since we continuously observed the XRD patterns during 1C charge, the real process for the phase transformation can be detected. In the presence of two phases, it has been reported from ex situ XRD measurement that the lattice constants are constant. In our in situ time resolved study, however, the peaks appeared to be shifted during the two phase reaction. The peak shift in the two phase region indicates that the dynamic phase transition is governed by the instantly change of Gibbs energy diagram.

Among a lot of cathodes of Lithium Ion Batteries (LIB), LiFePO4 is one of the most promising materials with high theoretical electric capacity, high-temperature stability and good cyclic performance(1). Previous studies showed that lithium insertion / extraction in LiFePO4 is basically a two-phase process(2), that is, LiFePO4/FePO4 interfaces propagate through the bulk region with inserting/extracting lithium and electrons collectively. Obviously this two-phase mechanism should dominate entire battery properties, although detailed atomic structures of interfaces, and also related lithium & electrons collective diffusion, are still an open question. In this study, TEM & STEM observations were performed to characterize the two-phase interfaces, and analyze correlations between the atomic-scale disordered structures and lithium ion mobility in the boundary region. Pristine LiFePO4 powders were synthesized by solid state reaction. Powder XRD analysis showed there is only the LiFePO4 single phase. Next, a chemical delithiation was performed (NOBF4) in acetonitrile solvent. After this treatment, sharp FePO4 XRD peaks were also appeared, which indicate both LiFePO4 and FePO4 phases are coexist. For TEM and STEM analysis, these particles were embedded in epoxy resin, thinned by mechanical polishing followed by Ar ion thinning. TEM observation showed that the average particle size is of the order of µm, and most particles have core-shell structures. Outer shells were highly distorted and cracked, while inner cores were almost free of defects. Diffraction patterns taken from each region strongly suggested that the outer shell is FePO4, and the inner core is LiFePO4. Considering the particle size and lattice constant mismatches, we concluded that cracks are introduced to accommodate lattice strains around the phase boundaries. Atomic resolution analysis were also performed by Cs-corrected STEM. We applied HAADF / ABF STEM imaging and found that in ABF images, there is apparent image contrast at Li sites in LiFePO4 phase. In addition, there was no bright contrast at Li sites in simultaneous HAADF STEM images, suggesting that this contrast represents Li atomic columns, not such as Li-Fe antisite defects. In STEM EELS line scan, the O-K edge pre-peak only appeared in outer shell (FePO4), which originated from the differences in Fe-3d and O-2p mixing(3), and this pre-peak was disappeared near the end of the cracks. It is confirmed from this result that phase boundaries are located very near at the end of the cracks, and the phase distributions are not affected by the specimen preparations and/or electron beam irradiation. Based on such atomistic structural information, we discuss how lithium ions and electrons diffuse around the interface region. References: 1) L. X. Yuan et al, Energy Environ. Sci., 4, 269-284 (2010) 2) C. Delmas et al, Nature Materials, 7, 665-671 (2008) 3) L. Laffont et al, Chem. Mater., 18, 5520-5529 (2006)

Lithium iron phosphate has gained a lot of interests as a cathode material in lithium ion batteries due to its excellent lifetime, low cost and environment friendliness. However, strategies such as making nano-sized particles and applying conductive coatings must be applied improve the rate performances. Modified LiFePO4 shows promising features as a candidate for hybrid vehicles and stationary energy storage batteries. Despite the great success in practical applications, the mechanism of the two-phase (LiFePO4 - FePO4) process is still under debate. Several mechanism, including classical core-shell, shrinking core, domino cascade, and phase transformation wave, have been proposed. Visualization of the delithiation of single particles with atomic resolution is the key to elucidate the mechanism. Single crystal oriented at different zone axes will provide us better information and clearer visualization on the phase properties due to the one dimensional Li diffusion pathway in the olivine phosphates. In this work we demonstrate a method to electrochemically delithiate large micron-size single crystal slabs for the first time. Different percentage delihtiated samples were subsequently thinned down by Focused Ion Beam (FIB) and characterized with Aberration corrected Scanning Transmission Electron Microscope (a-STEM) with Electron Energy Loss Spectroscopy (EELS) capability.

Battery materials with light atoms have the highest gravimetric capacities, but are also the most difficult materials to study with X-ray scattering techniques. Recent progress in our study of the light atoms in the high capacity battery materials LiFePO₄ and LiFeBO₃ utilizing very high quality diffraction data will be presented. Some X-ray experiments have been facilitated by the use of single crystal samples, while the use of neutron diffraction data has enabled the study of powder samples as small as 50 mg in size and has also simplified the collection of data at different temperatures. The implications of our structural results for the understanding of Li-ion diffusion and intercalation processes will be discussed in the context of our broader studies on these cathode materials.

Recently, LiMBO3 (M = Fe, Co, Mn) compositions, especially LiFeBO3, have been spotted as potential interesting cathode materials for Li-ion battery [1-5] due to the light and small triangular oxyanion (BO3)3- (molecular weight 58.8) which would allow in theory for LiFeBO3 to reach a capacity of 220mAh/g for the extraction of Li+ at ~2.8 V vs. Li, i.e. 30% higher than LiFePO4. The crystallographic unit cells of LiMBO3 (M = Fe, Mn, Co) are usually described in monoclinic C2/c symmetry except for one polymorph of LiMnBO3 described in the hexagonal (P-6) space group. Up to now, two structural models have been proposed for the monoclinic form of LiFeBO3. (two partially occupied Fe sites and two partially occupied Li sites[1] vs. one crystallographic site for Fe as well as for Li[3]) However, these latest results are questionable as the thermal motion parameters and occupancy factors of Fe and Li sites appear as non-refined[3] and a close look at the resulting interatomic distances reveals a wide range of distances for the 4-fold coordinate Li site (1.66 Å to 2.52 Å). We succeeded in preparing LiFeBO3 through various synthesis strategies including ceramic processing, closed environment as well as self-combustion technique. Pure LiFeBO3 (exempt from FeIII-containing Fe3BO5) was analyzed by state of the art synchrotron X-Ray diffraction and PDF (pair distribution functions) data, confronted with 57Fe Mossbauer and 6Li-NMR. All the results[6] suggested a new model(1Fe & 2Li) for LiFeBO3: Li has two partially occupied sites and Fe atom either vibrates along the long axis of ellipsoid[001], or randomly distribute inside the anisotropic thermal motion ellipsoid of Fe atom. LiFeBO3 prepared by self-combustion showed good reversible specific capacity of 175mAh/g(~0.8Li per formula) cycling between 1.5V and 4.3V at 293K C/50 rate. [1] V. Legagneur, Y. An, A. Mosbah, R. Portal, A. Le Gal La Salle, A. Verbaere, D. Guyomard, Y. Piffard; Solid States Ionics, 2001, 139 (1-2), 37. [2] Y.Z. Dong, Y. M. Zhao, Z.D. Shi, X.N. An, P. Fu, L. Chen; Electrochimica Acta, 2008, 53 (5), 2339 [3] A. Yamada, N. Iwane, Y. Harada, S. Nishimura, Y. Koyama, I. Tanaka; Advanced Materials, 2010, 22 (32), 3583. [4] A.Yamada, N. Iwane, S. Nishimura, Y. Koyama, I. Tanaka; J. Mater. Chem., 2011, 21 (29), 10690 [5] J. C. Kim, C. J. Moore, B. Kang, G. Hautier, A. Jain, G. Ceder; J. Electrochem. Soc., 2011, 158 (3), A309 [6] L. Tao, B. C. Melot, G. Rousse, D. Hanzel, G. Mali, J. R. Neison, T. M. McQueen, R. Dominko, S. Levasseur, C. Masquelier; submitted, June 2012

For the next-generation of lithium batteries, the discovery, characterisation and development of new electrode materials are crucial. It is also clear that to fully understand the local structural features influencing the behaviour of lithium battery materials, fundamental knowledge of their underlying defect chemistry, Li transport paths and surface structures is needed on the atomic and nano-scale. In this context, computational methods combined with structural techniques are now powerful tools for investigating these fundamental properties. This presentation will highlight recent studies [1] on such structure-property aspects of Li(Fe,Mn)PO4 and Li2FeSiO4 cathode materials and LiVO2-based anode materials. Key properties examined include lithium-ion transport pathways, intercalation mechanisms and surface structures, which are correlated with related experimental results where available (e.g. diffraction, electrochemistry, NMR). [1] C.Eames et al., Chem. Mater., 24, 2155 (2012); A.R. Armstrong et al., Nature. Mater. 10, 223 (2011); A.R. Armstrong et al., J. Am. Chem. Soc. 133, 13031 (2011)

LiMPO4 (M = Fe, Co) are orthorhombic crystals, belonging to the olivine family, that possess interesting anisotropic transport and magnetic properties. These crystals have applications as electrodes in the rechargeable battery industry due to their appealing charge storage capacity, stability and cost. In these studies we used nuclear magnetic resonance (NMR) spectroscopy to gain insight into the magnetic structure of LiMPO4 olivine compounds. By measurement of the 7Li and 31P NMR frequencies with crystal orientation, i.e. nu; = B0*σ*Ι, where B0 is the applied field and Ι is the nuclear spin, the relative directions and magnitudes of the components of the interaction tensors giving rise to the lithium and phosphorus shifts can be determined (hyperfine, quadrupole, magnetic dipole and susceptibility). It is found in the case of 31P that crystals exhibit large (paramagnetic) shifts, however, less so for 7Li within the same crystal depending on orientation. Data will be presented that show unambiguously two magnetically inequivalent phosphorus sites. The discussion will address correlations between the structure and the interaction tensors.

As a promising cathode material o-LiFe1-yMnyPO4 needs to maintain stable structure during hundreds of charge and discharge cycles and ranges of application conditions. In our previous work we have reported the structure, defects and thermal stability of chemically delithiated olivine phosphates with above 100 nm particle size, and the results showed that iron-rich compounds, 0le;yle;0.4, are stable up to 600 °C. But for higher Mn contents (y ge; 0.8) the weight loss during TGA testing is very large in both O2 and N2; also the material suffers from structural disorder which occurs as low as 250 °C. Here we report a comparative study of the structural stability of o-Fe1-yMnyPO4 (y ge; 0.8) with two different particle sizes, over 100 nm and below 50 nm. For the 50 nm particles, both chemically and electrochemically delithiated samples have been investigated using in-situ x-ray diffraction (XRD), DSC, TGA and other techniques under both inert (N2 or He) and oxidizing (O2) atmospheres. The results indicate that structural disorder may onset at temperatures as low as 150 °C for 50 nm particles and intermediate sarcopside phase (Fe,Mn)3(PO4)2 forms between 250 and 450 °C, which converts to the pyrophosphate phase at higher temperature. The role of structural defects and heating atmosphere on the thermal stability will be discussed. 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 DESC001294.

Since 2010, fluorosulfates materials have gained a renewed interest for applications in Li/Na-ion batteries. This interest comes from the high energy density coupled with the good open circuit voltages of those materials[1, 2]. Aside from these promising electrochemical performances, magnetic structures and physical properties of the 3d transition-metal-based materials have not been thoroughly studied yet. As demonstrated in our previous work, NaCoSO4F [3]; NaFeSO4F [3]; NaCoXO4F-2H2O [4] (X=S, Se) and LiFeSO4F [5] are constituted of one-dimensional chains of corner sharing MO4F2 octahedra linked through F atoms. Their magnetic susceptibility and low-temperature neutron diffraction show that they establish a G-type antiferromagnetic ground state for TN<40K. In the present work, we extend the investigations to the recently reported fluorine free Li2Co(SO4)2 and Li2Fe(SO4)2 [6] as well as to new potassium-based (KFeSO4F; KCoSO4F; KNiSO4F) electrode materials. The latter is of major interest as, unlike the Na or Li counterparts, it does not crystallize in the tavorite, sillimanite or triplite structure but rather in the KTiOPO4 structure type, known for its ferroelectric properties. [1] N. Recham, J-N. Chotard, L. Dupont, C. Delacourt, W. Walker, M. Armand, and J-M. Tarascon, Nat Mater 9, 68 (2010). [2] P. Barpanda, M. Ati, B. C. Melot, G. Rousse, J-N. Chotard, M-L. Doublet, M. T. Sougrati, S. A. Corr, J-C. Jumas, and J-M. Tarascon, Nat Mater 10, 772 (2011). [3] B. C. Melot, G. Rousse, J-N. Chotard, M. C. Kemei, J. Rodriguez-Carvajal, and J-M. Tarascon, Physical Review B 85, 094415 (2012). [4] B. C. Melot, J-N. Chotard, G. Rousse, M. Ati, M. Reynaud, and J-M. Tarascon, Inorganic Chemistry 50, 7662 (2011). [5] B. C. Melot, G. Rousse, J-N. Chotard, M. Ati, J. Rodriguez-Carvajal, M. C. Kemei, and J-M. Tarascon, Chemistry of Materials 23, 2922 (2011). [6] M. Reynaud, M. Ati, B. C. Melot, M. T. Sougrati, G. Rousse, J-N. Chotard, and J-M. Tarascon, Electrochemistry Communications 21, 77 (2012).

One challenge of modern power sources today is to meet the energy demand of advanced applications including electric vehicles (EVs). Recently, silicates with the general formula of Li2MSiO4 (M = Mn, Fe) have attracted attention of many researchers, as they can accommodate insertion/extraction of two lithium ions per formula unit and provide a theoretical capacity of ~330 mAh/g. Furthermore, it would be interesting to find out if Li2MSiO4 with mixed M of Fe, Mn and Co will provide superior performance to the pure phases as observed in the case of the layered LiMO2 cathodes (e.g. Li(Co1/3Mn1/3Ni1/3)O2). However, one of the major drawbacks of the silicate materials is their low electric conductivities. On the other hand, graphene, as a novel allotrope in nano carbon family and a mono layer of carbon with sp2 carbon lattice, has 0 eV of bandgap between the graphene layers and a high conductivity. Thus, we examined the use of graphene to prepare graphene/silicate nano composites to enhance the conductivity and reversibility of the silicate cathode material. In our work, Li2MSiO4 with mixed M of Fe and Mn was prepared by sol-gel synthesis method to obtain nano-scale structures. The precursor was coated with graphene and calcinated for complete crystallization. The improved electrochemical performance of grapheme/silicate composites indicates that it is a viable approach to advance the use of lithium silicates in Li-ion batteries.

High performance Li-ion secondary batteries have been recently developed in vehicle applications as well as stationary uses, enabling us to reduce the environmental burdens and to produce the high values. The state-of-art Li-ion batteries will greatly contribute to long cruising range and high fuel (electrical) efficiency of the plug-in hybrid and electric vehicles. However, in order to dramatically improve the cruising range and fuel efficiency, a new challenge is significantly needed for the battery system which has not been established yet. All-solid-state lithium-ion battery is a promising candidate of advanced lithium batteries to realize a compact battery with high energy density and long cycle life. However, the power of the all-solid-state batteries was not yet sufficient for the following reasons. One is the low ionic conductivity of solid electrolyte compared with liquid electrolyte, while the other is high interfacial resistance between active material and solid electrolyte. Recently, high lithium ion conducting solid electrolytes such as Li7P3S11 have been successfully discovered. We have also confirmed that higher ionic conductivity of solid electrolyte brought about much better rate capability of the battery. On the other hand, we have found that the interfaces between active material and solid electrolyte played a considerably important role in improving the rate capability. In the no modified interface between LiCoO2 cathode active material and Li7P3S11 solid electrolyte, a nanometer-sized layer composed of cobalt sulfide was newly formed. The inner diffusion due to each component of active material and solid electrolyte occurred at the interface, resulting in the increase of high interfacial resistance. On the other hand, the newly formed phase was not observed in the LiCoO2/Li7P3S11 interface modified by LiNbO3, and therefore, the interfacial resistance was dramatically decreased. This meant that the modified layer (LiNbO3) suppressed the inter diffusion of component elements at the electrode-electrolyte interface and brought about the significant improvement of rate capability. Thus, it can be stated that the design of solid-solid interfaces is a key technology to construct the reliable all-solid-state lithium-ion batteries. Needless to say, many issues to be solved still remains in all the batteries. However, nano-structural adjustments of the electrode-electrolyte interfaces using the latest technology will become a clue and breakthrough to overcome these issues. In this paper, we will focus on the electrode and electrolyte interfaces of the advanced lithium batteries (all-solid-state lithium batteries) as well as next generation batteries (lithium-air batteries and magnesium batteries).

The investigation of surface reactions of electrolytes with the graphitic anode of Lithium Ion Batteries (LIB) for Electric Vehicle (EV) applications will be presented. In this presentation, we will focus on two novel techniques which have been enabled by the use of Binder Free graphite anodes. The first is a novel method which allows straightforward analysis of the anode SEI by Transmission Electron Microscopy with Energy Dispersive X-ray Spectroscopy. The second, utilizes Multi-Nuclear Magnetic Resonance spectroscopy of the D2O extracts of the cycled anodes. This unique combination of techniques has allow us to develop significant new insight into the anode SEI structure.

It has long been recognized that many of the battery chemistries that provide high theoretical energy densities employ lithium metal anodes. Unfortunately, batteries with lithium metal anodes may fail catastrophically upon repeated cycling, due to uneven, dendritic metallic lithium deposition during recharge. Lithium dendrites that cross the cell create a short-circuit that may result in fire or explosion. Though lithium dendrite formation and propagation has been observed experimentally by several groups by optical imaging, electron microscopy, and monitoring cell potential during polarization, the relationship of the parameters governing dendrite formation and growth is still unclear. Understanding what results in varying dendrite onsite times among cells employing varying electrolyte compositions could enable the development of safe, rechargeable lithium metal batteries. In this talk, we will report on the quantitative effects of varying electrolyte modulus and lithium transference number on dendritic lithium growth, studies enabled by the development of tunable electrolyte platforms. It has been qualitatively reported by many that an increase in electrolyte modulus leads to a delay in dendrite onset time and short-circuit time. Using a unique platform, organic functionalized nanoparticles dispersed in a polyethylene glycol dimethyl ether host doped with lithium salt, the electrolyte modulus can be tuned over several orders of magnitude while the ionic conductivity changes relatively little. Even higher moduli electrolytes, 10-500 MPa, of very similar chemistry can be obtained by crosslinking of the nanoparticle ligands. Using this tunable platform, we quantitatively measure the effects of change in the electrolyte modulus on dendritic lithium growth as determined via the galvanostatic polarization method. Secondly, it is believed that an electrolyte with a lithium transference number approaching unity may result in uniform metallic lithium deposition due to the elimination of local anionic depletion zones near the anode that form when the typical electrolyte with a mobile counter-anion is employed. The dendrite onset time has been theoretically predicted to vary with anion transference number, t_a, as t_a^-2. We will report on investigations of lithium deposition using electrolytes of varying transference numbers, obtained by using a typical mobile lithium salt in conjunction with a tethered-anion based salt.

We have synthesized various Li single-ion conducting ionomers with low glass transition temperatures to prepare ion conducting membranes for lithium battery electrolytes where the sole mobile ion is Li+. We use dielectric spectroscopy to determine the number density of conducting ions and their mobility from electrode polarization (using the 1953 Macdonald model [1]) and the number density of ion pairs from measured dielectric constant (using the 1936 Onsager model [2]). This experimental work concludes that the number density of conducting ions is tiny in such neat ionomers [3,4] and SAXS reveals that a large portion of the ions are aggregated [5,6]. We have synthesized oligomeric siloxanes with polar side chains using hydrosilylation [7]. This versatile chemistry allows a wide variety of polar side chains to be attached to the very flexible siloxane backbone to create liquids with glass transition far below room temperature. When these polar plasticizers are added to the ionomers, the conductivity is enhanced by having more ions participate in conduction. This presentation shall compare cyclic carbonates, nitriles, sulfolanes and sulfones as the polar side chains, with and without ethylene oxide side chains introduced by using vinyl ethylene oxides as comonomer to make a liquid or using divinyl ethylene oxides as comonomer to make a gel electrolyte. These novel siloxane plasticizers will also be compared with ethylene oxide oligomers with polar end groups and conventional electrolytes such as cyclic carbonates. [1] J. R. Macdonald, Phys. Rev. 92, 4 (1953). [2] L. Onsager, J. Amer. Chem. Soc. 58, 1486 (1936). [3] D. Fragiadakis, S. Dou, R. H. Colby and J. Runt, J. Chem. Phys. 130, 064907 (2009). [4] S. Liang, U H. Choi, W. Liu, J. Runt and R. H. Colby Chemistry of Materials to appear, DOI: 10.1021/cm3005387 (2012). [5] W. Wang, W. Liu, G. J. Tudryn, R. H. Colby and K. I. Winey, Macromolecules 43, 4223 (2010). [6] W. Wang, G. J. Tudryn, R. H. Colby and K. I. Winey, J. Amer. Chem. Soc. 133, 10826 (2011). [7] Y.-J. Wang, S. Liang, W. Liu, U. H. Choi and R. H. Colby, Polymer Preprints 50 (2), 866 (2009).

The Solid Electrolyte Interphase (SEI) forms in most Li-ion batteries, but a lot of its properties are a mystery, such as its formation mechanism. The goal of this project is try to understand SEI properties and growth. This is done by using a simple thin film system to allow easy data interpretation.The thin film configuration allows sample to have high surface area, with a controlled morphology, which is perfect for studying this phenomenon. During the experiments the samples are held at constant voltage, which is above the intercalation threshold and looking at stress change in the material, the measurement is done by Multi-beam Optical Stress Sensor (MOSS). Studies have been done on CVD carbon, Gold and Copper electrodes. The results have shown that there is a linear relationship between current and stress during voltage holds. As well as that potential does not affect the slope of the line, just the rate of lithiation. It was also noted that surface properties affect the slope of this relationship. And by modifying the surface the SEI layer can be altered in thickness. This is most dramatic when surface is coated by atomic layer deposition (ALD) of alumina. Plasma treating the surface can also be used to decrease the thickness of the SEI layer, or increase it depending on the treatment. Lastly more stress was observed on edge oriented graphite surface in comparison to planar orientation. All of these observations can be used to design a more stable SEI layer.

Previously, we discussed the thermodynamics of the ternary graphite-intercalation compounds, LiS4Cn (S is the co-solvent), for ethylene carbonate (EC) and propylene carbonate (PC) in relation to their cycling behaviors in lithium-ion battery cells, based on density functional theory (DFT) calculations. Here, we discuss their reduction reaction characteristics inside graphite and compare with those in the bulk electrolyte. Our results found the first electron reduction energy for Li(EC)4Cn was positive, while that for Li(PC)4Cn was negative. This is a sharp contrast to those for Li(S)4 (S = EC or PC) in the bulk electrolyte. The results suggest that EC may be unstable against reduction, thus it may undergo a fast reduction decomposition inside graphite to release the energy, while PC is stable against reduction. This may be counter to what has been suggested in the literatures. We&’ll discuss these results in terms of charge transfer between the grapheme layers and the co-solvents.

Computational structure enumeration, analysis using an automated simulation workflow and filtering of large chemical structure libraries to identify lead systems has become a central paradigm in drug discovery research. Transferring this paradigm to challenges in materials science is now possible due to advances in the speed of computational resources and the efficiency and stability of chemical simulation packages. State-of-the-art software tools that have been developed for drug discovery can be applied to efficiently explore the chemical design space to identify solutions for problems such as Li-ion battery electrolyte components. In this presentation, virtual screening for anode SEI additives based on intrinsic quantum mechanical properties is illustrated. Also, a new approach to more reliably identify candidate systems is introduced that is based on the chemical reaction energetics of decomposition pathways for electrolyte additives.

To store effectively renewable energies such as solar and wind power, development of electrochemical performance of rechargeable batteries is desired. Sodium secondary batteries are more suitable than lithium-ion batteries because of their great advantage of using abundant and ubiquitous sodium resources. All-solid-state batteries with inorganic solid electrolytes are one of the ultimate goals of various energy-storage devices from the point of view of batteries&’ safety and reliability. A key material for realization of solid-state batteries is solid electrolytes with high ion conductivity. Recently, we have succeeded in preparing Na3PS4 glass-ceramic electrolytes with a high Na+ ion conductivity of over 10-4 S cm-1 at room temperature [1]. All-solid-state Na+ ion cells with the electrolytes operated as a rechargeable battery at room temperature. The high conductivity of the electrolytes was brought about by the precipitation of cubic-Na3PS4 phase from the mother glass. The enhancement of conductivity of solid electrolytes is expected in order to improve performance of solid-state batteries. In this study, synthesis conditions for Na3PS4-based glass-ceramic electrolytes were examined. The glass-ceramics were prepared by mechanical milling of a stating mixture of Na2S and P2S5 and subsequent heat treatment. It was revealed that the use of highly pure Na2S as a starting material was effective in increasing the conductivity of the Na3PS4 glass-ceramic electrolytes. Moreover, partial substitution of Na4SiS4 for Na3PS4 was also useful for enhancing the conductivity. The glass-ceramic electrolyte with 6 mol% Na4SiS4 showed high conductivity of 7.4×10-4 S cm-1 at room temperature and wide electrochemical window of about 5 V. The relationship between conductivity and structure of the electrolytes will be demonstrated. Reference: [1] A. Hayashi, K. Noi, A. Sakuda and M. Tatsumisago, Nat. Commun., 3 (2012) 856. Acknowledgement: This research was supported by JST, “Advanced Low Carbon Technology Research and Development Program (ALCA)”.

Organosilicon (OS) electrolytes are promising substitutes for commercial carbonate-based electrolytes because of their low flammability and high electrochemical and thermal stability. In order to understand the factors the ultimately control the stability of these compounds in formulated electrolytes and operational lithium ion batteries, we have undertaken a comprehensive analysis that integrates analysis of the gas-phase and surface products with computational studies of molecular electronic structure. A real-time headspace analysis apparatus that integrates a mass spectrometer with a temperature-controlled electrochemical cell can be used to detect the evolution of gas-phase decomposition products at specific temperatures during thermal cycling or at specific potentials during electrochemical measurements. XPS analysis of the electrodes provides complementary analysis of the surfaces. Finally, density functional calculations have been used to understand the relationships between OS molecular structure and stability. In this work we report studies using the molecule 1NM3 as a model OS compound, investigating its stability and decomposition pathways with LiPF₆ salt at high temperatures and high potentials. We show that PF₅ species (and not F^-) from LiPF₆ decomposition fluorinate 1NM3 molecules and facilitate the 1NM3 hydrolysis reaction at high temperature above 100 °C or at extreme potentials. In the absence of additional additives or blends, anode SEI layers are formed by fragmentation of the Si-O bond, leaving the SEI layer comprised largely of ethylene glycol fragments combined with LiF. The formation of the SEI layer can be manipulated through alternation of the molecular structure or through incorporation of SEI-forming additives such as vinyl carbonate. Ultimately this integrated approach provides fundamental insights into the factors controlling the chemical and electrochemical stability of OS compounds and leads to a systematic pathway toward the design of electrolytes with enhanced electrochemical performance. *RJH and RW have a financial interest in the outcome of this work.

During cycling of a lithium-ion battery, the electrolyte undergoes electrochemical decomposition at the graphite anode surface. The electrolyte used is generally a molar solution of a lithium salt, namely LiClO₄, LiPF₆ or LiAsF₆, dissolved in a volumetric mixture of ethylene carbonate and 1,2-dimethoxyethane. The products of electrolyte decomposition form a solid electrolyte interphase (SEI) on the anode surface. The SEI is expected to be mechanically stable and maintain good adhesion at the SEI/anode interface. This is an important requirement to prevent mechanical degradation of graphite and hence to prevent impedance losses during electrochemical cycling. Hence, characterization of the SEI layer properties is important for improved understanding of the electrochemical decomposition processes, at the same time ensuring good cyclability of lithium-ion batteries. In this work, the microstructural and compositional changes that occurred in the SEI formed on graphite electrodes during voltammetery tests (vs. Li/Li⁺) at different voltage scan rates were investigated. The microstructure of SEI layer, characterized using high-resolution transmission electron microscopy, consisted of an amorphous structure incorporating crystalline domains of ~ 5-20 nm in size. Evidence of lithium compounds, namely Li₂CO₃ and Li₂O₂, and nano-sized graphite fragments were found within these crystalline domains. These fragments, mixed with the decomposition products of the SEI layers, were likely to contribute to the formation of an SEI layer that is thought to prevent further damage to the electrode surface during subsequent cycling. Additionally, it was observed that the morphology and thickness of the SEI depended on the applied voltage scan rate (dV/dt). The variations in the Li⁺ diffusion coefficient (D_Li⁺) at the electrode/electrolyte interface during the SEI formation process were measured and two regimes were identified depending on the scan rate; for dV/dt ge; 3.00 mVs^-1, D_Li⁺ was 3.13×10^-8 cm²s^-1. At lower scan rates where D_Li⁺ was low, 0.57×10^-8 cm²s^-1, a uniform and continuous SEI layer was formed as observed by cross-sectional focused ion-beam and SEM. Therefore, a low dV/dt was conducive to establishing conditions that were favorable for consistent Li⁺ diffusion at the electrode/electrolyte interface.

The continued drive for high performance lithium batteries has imposed stricter requirements on the electrolyte materials. Solid electrolytes comprising lithium super ionic conductor materials exhibit good safety and stability and are promising to replace current organic liquid electrolytes. Recently, Kamaya et al. reported a new Li super ionic conductor material Li₁₀GeP₂S₁₂ (LGPS), which has the highest conductivity ever achieved among solid lithium electrolytes of 12 mS/cm at room temperature (comparable conductivity with liquid electrolytes), and outstanding electrochemical performance in Li batteries. Using first principles modeling, we investigated the diffusivity, stability, and electrochemical window of LGPS. We provide a hypothesis for the observed wide electrochemical window of LGPS. We also identify the diffusion pathways and calculated the corresponding activation energies and diffusion coefficient. Our ab initio MD simulations confirm fast Li diffusion in the 1D diffusion channel along the c direction, but also predict two additional diffusion pathways in the ab plane. Though diffusion in the ab plane is not as facile as in the c direction, it nonetheless contributes to the overall performance of the material. Our calculated overall activation barrier and conductivity are in remarkable agreement with the experimental values. We also discuss the potential to find other substituted versions of LGPS which do not contain Ge or S.

Recently, Li ion conductors with garnet-type structure have been extensively studied for their potential use of solid electrolytes in all-solid-state batteries due to their relatively good ionic conductivity at room temperature (0.2 mS/cm), high stability with lithium metal and wide electrochemical windows ( ~9V vs. Li). However, the ionic conductivity of Li7La3Zr2O12 (LLZ) is still low compared with that of liquid-based electrolyte. Many research groups have been studying in an attempt to increase ionic conductivity of Garnet-type oxide conductor trying to increase of lithium content and enlarge of lattice parameters in the materials. Lithium content is increase as substituting of lower valence ions for La/Zr ions. Lattice parameter is enlarged by substituting of larger ion radius than La/Zr ions. This study examines the effect of partial substitution of M for La site of Li7La3Zr2O12 on the ionic conductivity and structure. In addition, the reason of improvement is suggested by the structural analysis and the results of an experiment. The conventional solid state reaction method was employed to prepare polycrystalline powder with compositions Li7+yMxLa3-xZr2O12 (x=0.0625, 0.125, 0.25, 0.5, 1) (denoted as LLMxZ thereafter). All the XRD peaks of the sintered LLM0.125Z correspond to the Li5La3Nb2O12 (JCPDS # 01-080-0457) phase of cubic-garnet structure without any other phases. When the M contents are 0.0625 and 0.125, the ionic conductivity of the LLMxZ is higher than it of LLZ. And the maximum total ionic conductivity is 0.78 mS/cm at x=0.0625. It is apparent that the ionic conductivity of the LLMxZ is decreased as the M contents are increased after x=0.125. There is maximum ionic conductivity of LLMxZ series near x=0.1. Lithium ion conduction depends on the lithium contents and mobility of lithium ion. And it is reported that lithium octahedral sites and their vacancies in garnet-type structure mainly involved on ionic conduction. So around x=0.1, optimum composition, ratio of lithium sites and vacancies are exited. The activation energy (Ea) was estimated to be Ea=0.29eV for LLM0.125Z. The lower activation energy means the barrier of ionic conduction is lower, so ionic conductivity is higher than opposite case. And its value relates the structural characteristics for lithium ion conductors. As the lattice parameter is large, the mobility of lithium ion is also high. It is well matched the results of Rietvelt refinement. A structural model of space group of Ia-3d was used and each lattice parameter for LLM0.125Z and for LLZ is 12.96361 Å and 12.96527 Å, respectively. No grain boundary is observed and some voids exist on the cross-sectional SEM images and the relative density is 90.4%. Fast lithium ion conductor with Garnet-type structure is obtained by partial substituting M for La. The highest total ionic conductivity is 0.78 mS/cm at x=0.0625 and the activation energy is 0.29eV. High dense pellet is obtained.

To realize the high energy density of metallic lithium anodes will likely require the protection of a solid electrolyte membrane to maintain a smooth, dendrite-free interface and to protect the surface from side reactions. Such a membrane must be thin, mechanically robust and highly conductive for lithium ions. Composites of a highly conductive ceramic electrolyte with a polymeric electrolyte are expected to provide the best overall properties, assuming the internal interfaces and grain boundaries provide good adhesion and no significant resistance to ionic conduction. Results of single phase, bilayer and composite samples will be presented with attention to the properties of the interface, simulated properties of tailored structures, and stability with metallic lithium. Acknowledgement: Research has been supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory. ORNL's Shared Research Equipment (ShaRE) User Facility, which is sponsored by the Office of Basic Energy Sciences, U.S. Department of Energy, has also supported this work.

The objective of our research is to develop dense high Li-ion conductivity (>10-4 S/cm) solid state electrolytes based on Li7La3Zr2O12 (LLZO) for use in Li/S, Aqueous Li-Air and Li batteries. There are two major problems with LLZO: 1] stabilizing the cubic structure at room temperature and 2] obtaining a material with a high relative density (>95%). To solve the first problem we have investigated doping LLZO with Al, Ga or Ta. To solve the second problem we are consolidating the material using hot-pressing. In this presentation the following will be presented: 1] A comparison of the ionic conductivity of Al, Ga, Ta stabilized LLZO. 2] The chemical stability of cubic LLZO with Li, S and water. 3] The electrochemical stability of cubic LLZO with Li,S and with various anode and high voltage cathode materials. 4] The mechanical properties of cubic LLZO such as; modulus and strength. 5] Cycling of cells containing a LLZO electrolyte at room and elevated temperature.

All solid-state rechargeable lithium battery is recognized as one of alternative technologies for rechargeable power source, because of likely higher energy density and improved safety. For all solid state lithium ion batteries, Lithium transfer in the bulk material can be the rate limiting step since the small interface between electrode and solid electrolyte, and low lithium diffusion coefficient in bulk materials. Currently solid state lithium ion batteries are thin film batteries and the thickness is only several microns, which is not suitable for some applications requiring high areal energy density. In our research work, in order to overcome the sluggish lithium diffusion in the bulk material and small electrochemical reaction area for solid state lithium ion batteries, 3D solid state lithium ion battery architecture was successfully fabricated. The areal energy density for our batteries can be more than 20 times higher than thin film batteries.

Recently, many researches in lithium ion batteries focus on the increase of energy density. Main approach for this increase is the developing of cathode or anode materials with large capacity. However, high energy density is also achieved by high voltage which is relates to the electrochemical window of electrolyte in the cell. Solid electrolytes will be a good candidate for achieving high voltage because of their wide electrochemical window. Moreover, solid electrolytes have many other advantages over liquid electrolytes.¹ For example, solid electrolytes do not require the usage of separator in the cell and can be much safer than liquid one. Despite of these advantages, solid electrolytes still suffer from low electrical conductivity to be widely utilized. Many progresses have been made to increase the electrical conductivity of solid electrolytes.² However, the conductivity mechanism of solid electrolytes may not be fully understood yet. In this presentation, we will discuss about this mechanism. The electrical conductivity of solid electrolytes depends on the concentration and the mobility of conducting ions and consists of grain (bulk) and grain boundary conductivity. In polycrystalline, the effect of grain boundaries should be considered to understand the electrical conductivity. Li_1.5 Al_0.5Ge_1.5(PO₄)₃ (LAGP) can be good example for understanding the effect of grain and grain boundary because it has high bulk conductivity, 10^-3 S/cm with lower grain boundary conductivity. In this talk, we will try to understand the grain and grain boundary conductivity through LAGP synthesized with additives or dopants. Reference 1 Abelmaula Aboulaich & Mickael Dolle, Advanced Energy Materials, 1, 179-183 (2011) 2 Noriaki Kamaya & Ryoji Kanno, nature materials, 3066 (2011)

For the past two decades, intensive research on lithium ion battery technology attempted to optimize safety and durability issues linked with the use of liquid electrolytes that may induce sizeable risks of fire and explosion in these high energy density electrochemical systems. In this respect, so-called “All-Solid State” batteries, built around non-flammable solid electrolytes, are recognized as good alternatives. Therefore, their development requires the use of an electrolyte showing high lithium ionic conductivity at ambient temperature with high electrochemical and thermal stability [1-3]. In our very recent publication we have showed the synthesis of a highly ion-conductive Li6PS5Cl Li-argyrodite through a high energy ball milling [4]. This compound exhibits an ionic conductivity of 1.33x10-3 S/cm and an activation energy of 0.3-0.4 eV for conduction with an electrochemical stability up to 7V vs. lithium. These results are obtained after only 10 hours of milling and with no additional heat treatment. All-solid-state half-cells realized with LiCoO2 and Li4Ti5O12, as active material, present a capacity of 140 and 120 mAh/g of material, respectively, and for an active material amount, in the composite electrode, of 90% for LiCoO2 and 60% for Li4Ti5O12. Notice that these results are obtained with no additional carbon for LiCoO2-based battery and only 5 wt% for Li4Ti5O12. An all-solid-state full-cell realized with these two compositions presents a reversible capacity of 135 mAh/g of LiCoO2 with a very small polarization of ~100 mV at a C/25 rate. [1] A. Hayashi, K. Minami, J. Solid State Electrochem., 2010, (14), 1761-1767. [2] N. Kamaya et al., Nature Materials., 2011, (10), 682-686. [3] G. Delaizir et al, M. Adv. Funct. Mater., 2012, (22), 2140-2147. [4] S. Boulineau et al., Solid State Ion. (2012), doi : 10.1016/j.ssi.2012.06.008.

The purpose of this work is to develop bulk ceramic electrolyte technology to enable new Li battery technologies. The ceramic electrolyte is based on the garnet structure, with the nominal formula Li7La3Zr2O12, exhibiting the unique combination of attributes such as: i) electrochemical stability between 0-6 V vs Li/Li+, ii) ~ 1mS/cm conductivity at 298K and iii) stability in air. While this electrolyte shows promise, there have been few studies that investigate DC Li transport and interfacial phenomena when coupled with metallic Li anodes and high voltage cathodes. This report will present the results of DC Li cycling tests and efforts to characterize the interfacial impedance between high voltage cathodes and high density Li7La3Zr2O12. The data will include results from complex impedance analysis, cyclic voltammetry, DC polarization and temperature dependent cell impedance measurements. Pre and post cycling X-Ray diffraction and electron microscopy data will also be presented.

Lithium ion conducting solid electrolytes on the basis of garnet-type oxides, e.g. Al-stabilized Li7La3Zr2O12 (LLZO), are highly stable vs. Li and vs. high voltage materials. Thus, they may qualify as materials for membranes or protecting films in batteries with lithium metal electrodes. We will present a detailed study on the Li metal electrode kinetics on different garnet-type lithium solid electrolytes and discuss the data on the basis of mechanisms for interfacial ion transfer. The exchange current densities for the lithium metal electrode and its temperature dependence are correlated with the conductivity and activation energy of the bulk transport. The mechanical boundary conditions, the microstructure of the solid electrolyte membrane and whisker or dendrite formation during lithium metal cycling are also exemplified and critically discussed. Finally, results for the interface kinetics for ion transfer across solid electrolyte/liquid electrolyte are presented and discussed.

Li-ion conducting solid electrolyte materials attract attentions from the viewpoint of possible application for all solid-state Li-ion batteries with improved long-life and safety by substituting volatile and combustive organic liquid electrolyte that are used in commonly available storage of electricity. Among the ionic conductor, a group of oxide materials with garnet structure is one of the favorable candidates with respect to the reported fast ionic conductivity up to 0.3 mS/cm at room temperature in the composition of Li7La3Zr2O12 (LLZ), stability in ambient atmosphere and highly inert character to elemental Li. Needless to say the attempt for increasing intrinsic conductivity is important, though, decreasing the traveling path length of Li ions separating positive and negative electrodes is also crucial to ensure all-solid Li-ion batteries with low internal resistance. Sintered ceramic body of oxide materials, however, finds a difficulty in decreasing the thickness below several tens microns because of the brittle nature. Various film deposition techniques, in contrast, can achieve the thickness far below one micron. To obtain optimal composition and low growth temperature, chemical solution deposition techniques are advantageous in controlling composition: oxide crystals can be synthesized from solution with homogeneity at molecular level. In this study, therefore, Li-ion conducting oxide thin films with garnet-type structure were synthesized by chemical solution decomposition route and electrical properties were investigated. Solutions were prepared by dissolving Li-, La- and Zr-alkoxides materials in organic solvent and refluxed. Excess Li was added to compensate the volatile loss during thermal treatments. Al source was also added to improve sinterability and stability of cubic phase. LiCoO2 and Li4Ti5O12 electrode materials were also synthesized through similar solution routes. The solutions were repeatedly spin-cast on sputter-grown Pt blocking electrode layer on silicon substrate. The deposited films were crystallized into the tetragonal phase at a temperature below 650omicron;C. Subsequent heat treatments were performed up to 900omicron;C to transform to cubic phase. Typical film thickness of 1.2mu;m was found in SEM study. XRD studies indicate single phase of LLZ films were crystallized. Apparent orientation behavior was not observed in XRD pole figure study. After depositing Au blocking electrode layer with the diameter of 500mu;m, temperature dependence of AC impedance spectra were measured in the ranges of 25-200omicron;C (temperature) and 1Hz-10MHz(frequency). Total ionic conductivity of 0.07 mS/cm was observed at 25omicron;C and positively increased with thermally activating manner. Detailed studies of electrical properties will be presented.

Lithium ion batteries have recently drawn much attention due to their viability as energy storage devices for a wide range of applications, from portable electronics to hybrid vehicles. The higher volumetric and gravimetric energy densities make them superior among other known batteries, including lead acid and Ni-metal hydrides. The current Li ion batteries contain flammable organic solvents incorporated with an organic polymer and Li salts as the electrolyte, Li-C as the anode and LiCoO2 as the cathode. Solid electrolytes with high total (bulk + grain-boundary) ionic conductivity > 10-3 Scm-1 and high electrochemical stability have potential to replace the polymer electrolytes in current Li ion batteries. It is generally believed that all-solid-state Li ion batteries using solid electrolytes are potentially safer and will provide higher energy densities. Several inorganic metal oxides, including Li-based silicates, phosphorous oxynitrides, Na superionic conducting structured phosphates, and A-site deficient perovskite-type oxides are being considered as electrolytes for all-solid-state batteries. In this talk, we report the novel Li conducting garnet-like structured metal oxides in the Li2O-La2O3-BaO-MxOy system (M = Zr, Nb,Ta), their chemical stability with electrodes, and ion-exchange properties in water and organic acids.

The current organic liquid electrolytes used in lithium-ion battery is the major source of safety and reliability problem as they are flammable, reactive on anodes below 0.8 V and decomposes above 4.5 volts on most advanced cathodes limiting the utilization of high voltage cathodes. Replacing the current electrolyte with a stable chemical stable electrolyte with high mechanical strength may solve many issues of current lithium batteries.. We report a novel free standing solid electrolyte with high lithium ion conductivity (10-4 - 10-3 S/cm within -30 - 80 C) to as a replacement for the current liquid electrolyte. . The single ion solid state lithium ion conductor is a composite based on a modified lithium germanium-silicon phosphorous oxysulfide compound made in a thin flexible film that provides a very low interfacial resistance at the electrode/electrolyte interfaces. The compound is prepared by a simple solid state reaction, compounded and casted as a thin-film. The crystallinity and phase purity of the sample is checked by XRD. The ionic conductivity of the new electrolyte is measured by Wagner-Huggins-Weppner method (ion-blocking electrode), 4-probe, and impedance techniques. Results indicate enhanced lithium-ion conductivity with very low activation energy. Fast lithium ion transport through the electrolyte and reversible lithium deposition/stripping on/from ion-blocking electrode and high voltage cathodes were confirmed . The local lithium ion dynamics was studied by Raman spectroscopy in the far-IR region and octahedral and tetrahedral coordinations of lithium ions were analyzed. Electrochemical stability of the electrolyte up to 10 Volts versus lithium reference was verified by cyclic voltammetry. We will discuss the mechanism of the enhanced ion conduction and inherent stability in this class of super ion conductors, and propose a new generation of safe and high voltage lithium battery for small and large format applications.

Most of today&’s applications of Lithium-ion batteries (e-mobility, portable electronics etc.) face growing demands for significantly improved performance: higher energy density, improved cycling performance, safety, flexibility in device integration, etc. For these reasons, there is a great interest in development of nanostructured anode and cathode materials. Colloidal chemical synthesis is very attractive as it offers routine access to materials with the mean crystallite size in the range of 3-20 nm. Non-aqueous synthesis, in particular, allows also inexpensive access to nanocrystals and nanoparticles with very high degree of compositional, morphological and size-uniformity. We will present two examples of highly-monodisperse, sub-20nm nanocrystals: Metallic Tin nanocrystals as anode material and Iron fluoride nanocrystals as cathode material. These materials were synthesized using inexpensive precursors such as metal chlorides and recyclable, technical grade high-boiling organic solvents such as hydrocarbons, yet enabling narrow size distributions of 3-6%. We will also present detailed structural and electrochemical characterization of these nanostructures. Small crystallite size and proper surface functionalization with small molecules allows good charge transport and solution-based mixibility with other components of battery electrodes (binders, conductive additives). For Sn-based nanocrystal based anodes, high reversible capacity in the excess of 700 mAh/g over more than 500 cycles at charge/discharge rates of 1-20 C were obtained. We also show that monodisperse nanocrystals can be arranged into long-range ordered, densely packed superlattice structures with enhanced electrochemical performance.

All solid state batteries have always been considered with a peculiar interest due to the advantages they offer, especially when safety issues are concerned. While thin film micro-batteries have been widely studied, their use remains limited to microelectronic applications. In order to answer today&’s energy needs, bulk-type all solid batteries, offering higher energy densities than thin films, are required. Here, we report on the use of Spark Plasma Sintering (SPS) as an assembling technique to prepare all inorganic monolithic Li-ion batteries having cycling characteristics approaching their liquid Li-ion counterparts while being safer and faster to be made [1]. Such an achievement is nested in the structural quality of the electrode-electrolyte interfaces, which enable both good charge transfer and mechanical integrity upon cycling. The different steps to reach our goal will be detailed with the development of composite ceramic electrodes and full cells in few minutes by SPS. The influence of some parameters such as electrodes thickness, operating temperature will also be addressed in this presentation. The obtained cells already display high surface capacity of 2 to 6 mAh.cm-2 at 80 °C. This work provides a new path worth pursuing for designing Li-ion batteries capable of operating safely over a wide temperature range [2]. Acknowledgements The French National Research Agency (ANR) and the competitiveness Aerospace Valley cluster are acknowledged for their financial support. [1] A. Aboulaich, R. Bouchet, G. Delaizir, V. Seznec, L. Tortet, M. Morcrette, P. Rozier, J-M. Tarascon, V. Viallet, M. Dollé, Adv. En. Mat., 1 (2011) 179-183. [2] G. Delaizir, V. Viallet, A. Aboulaich, R. Bouchet, L. Tortet, V. Seznec, M. Morcrette, J-M Tarascon, P. Rozier, M. Dollé, Adv. Funct. Mat., in press, doi : 10.1002/adfm.201102479.

Electrochemical shock - the electrochemical cycling induced fracture of materials - has been implicated as a degradation mechanism contributing to capacity fade and impedance growth in lithium-ion batteries. The mechanisms for electrochemical shock in lithium-storage compounds depend on many factors, including but not limited to: solution thermodynamics with respect to lithium composition (solid solution vs. phase transformative), electrochemical duty cycle, and particle microstructure (single vs. poly- crystalline). Using several model systems, including layered and spinel structured compounds, we study experimentally and computationally the mechanisms for electrochemical shock in these materials and suggest strategies to avert electrochemical cycling induced degradation.

The fruitful contribution of Broadband Dielectric Spectroscopy (BDS) to study materials applied to batteries electrodes has been previously shown. The BDS measurement was up to now ex situ measurement, on dry electrode [1, 2] or electrode soaked with electrolyte [3]. They provide a fundamental insight into the conduction properties at all scales of the materials before being integrated in a real battery. However, these properties evolve when the electrode comes in contact with the electrolyte during and after electrochemical cycling (charge and discharge processes). To study this evolution, an innovative device (measurement cell) has been developed to perform BDS measurements and electrochemical cycling at the same time, i.e. operando measurements. The frequency range is about 1 kHz - 5 GHz. This new device completes the traditional ex situ measurements. In this work, we will demonstrate the design and development of this cell as well as several steps followed to validate it. Furthermore, we will demonstrate a representative measurement of an NMC (LiNi1/3Ni1/3Co1/3O2) based composite electrode in a lithium-ion battery using the new cell. Data acquisitions were made on dry electrode and then on an electrode wetted with an electrolyte, after the first charge, the first discharge, and several cycles. Very interesting evolutions are witnessed during the measurements and a preliminary interpretation drawn will be presented. The measurements provide original data in the area in such a way that it is possible to see the evolution of complex conductivity at different scales with electrochemical performance. It is important to note that the classical impedance spectroscopy does not allow probing the electrical properties in the MHz - GHz range. This new device opens thus important prospects to determine the evolutions of the multi-scales electrical properties during electrochemical cycling. [1] J.-C. Badot et col., Multi-scale description of the electronic transport within the hierarchical architecture of a composite electrode for lithium battery, Adv. Func. Mat., 19, 2749minus;58, 2009. [2] K. A. Seid et col., Multiscale electronic transport mechanism and true conductivities in amorphous carbon-LiFePO4 nanocomposites, J. of Mat. Chem., 22, 2641minus;9, 2012. [3] C. Perca et col., Broadband Dielectric Spectroscopy study of the solvent/electrolyte-soaked C-LiFePO4 Li-ion battery electrode, MRS Fall, Boston, 2011. Financial funding from the ANR program no. ANR-09-STOCK-E-02-01 is acknowledged.

Precise knowledge of the thermodynamic properties of materials used in lithium ion batteries is a key issue for the improvement of the entire system. Moreover, specific microstructures and compositions of electrodes as well as changes in their thermodynamic properties over time become more and more important. As a consequence, well adapted techniques to study thermodynamic properties are required. The work is focused on a newly developed measurement system which enables to investigate the thermodynamic properties of thin films including battery layer sequences in a temperature range from -20 to 900 °C. The functional demonstration of this Thin Film Calorimeter is done using Li(Co,Ni)-based layered oxides which are commercially relevant cathode materials as well as anode materials like MoS₂ and Ti/TiO₂-Si. Thin films with a thickness of several micrometers of the material of interest are deposited on high-temperature stable piezoelectric resonators which are used as Thin Film Calorimeter. Thereby, langasite crystals (La₃Ga₅SiO₁₄) are applied in order to cover the temperature range mentioned above. By measuring the temperature dependent shift of the resonance frequency, the device is working as a precise temperature sensor. The production or consumption of latent heat by the active layer(s) results in temperature fluctuations with respect to the furnace where the sensor is placed. Those information enable to extract the temperature and time dependence of phase transformations as well as the associated enthalpies. Initially, metallic layers of tin and aluminum are used to test and verify this approach. The enthalpies of solid-liquid as well as of solid-solid phase transitions are observed in the correct manner. Further, the thermodynamic data of the cathode materials Li(Ni_0.8Co_0.15Al_0.05)O_2-δ and Li(Ni_1/3Co_1/3Mn_1/3)O_2-δ obtained by Thin Film Calorimetry are determined as well as those for the solid electrolyte Li_3.4V_0.6Si_0.4O_4-δ. As a promising anode material MoS₂ is investigated. Here, a phase transformation indicated by a frequency shift at 478 °C is observed. The associated thermodynamic parameters as well as the structural changes are discussed. Another anode material of interest is silicon due to its very high (theoretical) capacity of 4200 mAhg^-1). A solution for its main drawback, i.e. its mechanical instability due to strong volume expansion during lithium intercalation, could be the application of thin silicon films on a supporting matrix. Nanoporous titania shows good stability, high surface area and satisfying electrochemical properties. In this approach titanium is deposited on the resonators and further on anodized in 0.5% NH₄F to TiO₂. In this supporting matrix Si is deposited potentiostatically or by magnetron sputtering. Finally, thermodynamic data of these nanoporous Ti/TiO₂ and Ti/TiO₂-Si compounds are determined and presented.

Ionic transport in Li ion battery electrodes is influenced by their low porosity and the highly tortuous pathways between particles. In negative electrodes, this structural limitation to the ionic transport is particularly severe for the anisotropic graphite particles which tend to align with their normals parallel to the electrode normal creating more tortuous pathways for the through-plane diffusion. In thicker electrodes, this effect is even more extreme. An alternative approach that provides a less tortuous path is inspired by the mammalian lung where large bronchi successively branch into smaller bronchi and provides a shortened pathway to the large surface area of the alveoli with minimal flow restriction. Our implementation of this approach is through the use of engineered porosity to augment through-plane ionic transport in graphitic anodes to improve charge acceptance rates and reduce the risk of Li-plating. Advanced materials processing technology was implemented to fabricate the engineered porosity. Preliminary results show an improvement in charge capacity retention as a function of Li-intercalation rate of 50% in thicker electrodes (2.8 mAh/cm2) between 0.5 and 1 C. A theoretical analysis will be presented to bolster the understanding of the phenomena that limit the charge acceptance at various rates in thick electrodes. Simple expressions will be provided to quickly evaluate limitations wherever feasible.

NMR shifts in active materials for Li Batteries are mostly governed by the Fermi contact shift due to transfer of some density of electron spin from the paramagnetic transition metal to the nucleus of interest.(1) Understanding the mechanisms of this interaction is a prerequisite for a full exploitation of the NMR characterization of such materials and of their lithiation/delithiation mechanisms. The first step of this process is to be able to accurately model the experimental NMR shifts through electronic structure calculations to validate them. Some of us have earlier demonstrated the performance of ab initio methods for the qualitative interpretation of NMR paramagnetic shift(2) and more recently, quantitative approaches were proposed based either on pseudo potential/plane wave methods(3) or full potential methods using LCAO basis set.(4) In this paper, we propose, as an alternative approach, a more accurate, efficient, and robust method based on the use of a Linearized Augmented Plane Wave (LAPW) basis set. The full-potential (L)APW method, as implemented in the WIEN2k code, is coupled with the use of hybrid functionals for the evaluation of hyperfine field quantities. The WIEN2k code uses an autoadaptive basis set that is highly accurate for the determination of the hyperfine field and the way hybrid functional approaches are implemented offers the possibility to use them at no additional computational cost. In this paper, NMR Fermi contact shifts for lithium are studied in different classes of paramagnetic materials that present an interest in the field of Li-ion batteries: olivine LiMPO4 (M = Mn, Fe, Co, Ni), anti-NASICON type Li3M2(PO4)3 (M = Fe, V), and antifluorite-type Li6CoO4. Making use of the possibility to apply partial hybrid functionals either only on the magnetic atom or also on the anionic species, we evidence the role played by oxygen atoms on polarization mechanisms. Our method is quite general for an application on various types of materials and our simulations can be easily discussed in terms of electronic structure and chemical bonding analysis in order to correlate NMR paramagnetic shifts with a “through-bond hyperfine interaction” scheme based on well-known delocalization and polarization mechanisms. (1) C.P. Grey, N. Dupre, Chem. Rev. 2004, 104, 4493. (2) D. Carlier, M. Ménétrier, C.P. Grey, C. Delmas and G. Ceder, Phys. Rev. B Condens. Matter Mater. Phys. 67 2003, 67, 174103(14). (3) G. Mali, A. Meden and R. Dominko, Chem. Commun. 2010, 46, 3306-3308. (4) J. Kim, D.S. Middlemiss, N.A. Chernova, B.Y.X. Zhu, C. Masquelier and C.P. Grey, J. Am. Chem. Soc. 2010, 132, 16825-16840

We will present recent transmission X-ray microscopy (TXM) work on high capacity battery materials, such as Si, Ge, Sn, and Li_xFePO₄, for next generation rechargeable batteries. High resolution X-ray imaging offers a direct means of observing Li-ion batteries during operation from the full electrode down to single particles. Additionally, the reduction and oxidation of active material can be spatially resolved during cycling. The theoretical capacity (4200 mAhg^-1) of silicon is more than ten times higher than existing commercial anode materials. The capacities of Ge and Sn, although not as high as Si, are still significantly higher than graphite. Nevertheless, large volume changes during lithiation and delithiation are believed to cause crack formation leading to particle pulverization and capacity fading in all three materials. With 2D and 3D in situ TXM studies, we can quantify the volume change in a single particle as well as directly observe the development of cracks during operation. Despite being one of the most studied cathode materials, the reaction mechanism of Li_xFePO₄ remains poorly understood. Using the high resolution and chemical sensitivity of the TXM, we can visualize how the two-phase reaction front between FePO₄ and LiFePO₄ travels through particles and between particles. Additional information, such as volume change during cycling can be tracked simultaneously.

We present the applicability of X-ray Raman Spectroscopy of light elements to probe the electronic structure of lithium air and lithium ion batteries under in-situ conditions. In particular, recent advances in resolution and throughput of x-ray raman spectroscopy (XRS) offer the capability to measure, with true bulk sensitivity (10s um to mm probing depth), 1s x-ray absorption profiles of light elements and L edges of transition metals with less than 0.3eV resolution. We present initial results from the Spectroscopy program at SSRL and resulting from collaborations with groups in the lithium battery fields, including ex-situ and in-situ measurements of cathodes, anodes and lithium compounds. References: [1] “A high resolution and large solid angle x-ray Raman spectroscopy end-station at the Stanford Synchrotron Radiation Lightsource” D. Sokaras, D. Nordlund, T.-C. Weng, R. Alonso Mori, P. Velikov, D. Wenger, A. Garachtchenko, M. George, V. Borzenets, B. Johnson, Q. Qian, T. Rabedeau, and U. Bergmann

Sn and Sn-based intermetallics have lately attracted considerable attention for use as negative electrodes in lithium-ion batteries because Sn exhibits a much higher lithiation capacity (993.5 mAh/g) than graphite (372 mAh/g). However, Sn-based electrodes suffer from large irreversible capacity loss in the first lithiation/delithiation cycle and poor capacity retention in subsequent cycles. These are typically attributed to electrode decrepitation due to large volume changes during lithiation and delithiation. In order to understand the mechanics of electrode failure due to large deformation associated with the alloying and de-alloying processes, it is essential to quantify the stress values as a function of lithium concentration. We report in situ measurements of stress evolution in tin thin-film electrodes during galvanostatic lithiation and delithiation using the wafer-curvature method. Upon lithiation, constrained by the underlying substrate, the Sn electrode undergoes rapid increase in compressive stress. The magnitude of this stress increases with increasing lithium concentration reaching a maximum of ca. 0.62 GPa at the specific capacity of 848.34 mAh g-1. Upon subsequent delithiation, the stress decreases rapidly and goes tensile. After reaching a maximum tensile stress of ca. 0.09 GPa, the stress decreases monotonically with decreasing lithium concentration. At the end of delithiation, the electrode reaches a state of moderate compressive stress of ca. 0.23 GPa. Though both Li and Sn are very soft metals with yield stresses of 4 MPa and 15 MPa, respectively, almost all Li-Sn intermetallic alloys that form electrochemically show much higher stiffness values, which could provide mechanistic insights on the performance and failure characteristics of Sn-based lithium-ion battery electrodes.

In this study, we developed an integrative bio-inspired approach that improves the power and safety of Li-ion batteries (LIBs) by the surface modification of polyethylene (PE) separators. The approach involves the synthesis of a diatom-inspired silica layer on the surface of the PE separator, and the adhesion of the silica layer was inspired by mussels. The mussel- and diatom-inspired silica coating increased the electrolyte wettability of the separator, resulting in enhanced power and improved thermal shrinkage, resulting safer LIBs. Furthermore, the overall processes are environmentally friendly and cost-effective. The process described herein is the first example of the use of diatom-inspired silica in practically important energy storage applications. The improved wetting and thermal properties are critical, particularly for large-scale battery applications.

We report that a solid-state battery architecture enables the reversible, four electron storage of fully utilized solvothermally synthesized cubic-FeS2 (pyrite). With a sulfide based glass electrolyte (77.5Li₂S:22.5P₂S₅, mol%) we successfully confine electro-active species (nano-Fe⁰ and S_n^2-) and permit the safe use of a lithium metal anode. Our FeS₂/Li solid-state cells deliver a theoretical specific capacity of 894 mAh g^-1 at 60°C. Prior to our study, the full reversibility of a FeS₂/Li metal cell was never demonstrated at temperatures < 400°C. For the first time, we also observe nano-particles of orthorhombic-FeS₂ (marcasite) as a charge product and use this finding to come to a better understanding of the FeS₂ redox chemistry at low operating temperatures.

Over-lithiated layered oxide (OLO) materials are receiving much attention owing to high specific capacity of 250 mAh g-1. However, the electronic conductivity of OLO is relatively poor comparing the conventional cathode materials and this severely limits the rate capability which is essential for the electric vehicles. For increasing the conductivity of electrode, the carbon coating by heat treatment has been studied as one of the most feasible ways, but in the case of the oxide cathode, it is restricted by the undesired carbon-thermal reduction. Therefore, conductive carbon coating have not been studied vigorously on the oxide. The multi-wall carbon nano tubes (MWCNT) which are highly conductive are introduced for the surface modification by the noble physical coating method to overcome the limitation of poor conductivity. MWCNT coated OLO (C-OLO) was prepared by the physical coating method with 2wt.% of MWCNT and OLO. To confirm the MWCNT-coating, HR-SEM analyses were conducted. For further examination of coating effect, the surface was analyzed by XPS and the atomic concentration ratio of carbon and manganese was calculated. As surface treatment proceeds, the ratio of C/Mn was increased from having a high carbon on the surface. The photoelectron of Mn is generated from OLO and this atomic concentration behavior reflects that the carbon layer successfully covers the OLO with considering the top surface is active for making photoelectron by XPS. The conductivities of prepared C-OLOs were higher than that of bare (for example, 4.14 vs. 170 mS /cm at 94:3 wt.% of sample and carbons). The conductivity-gap between OLO and C-OLO decreases when the conducting agent increases. It indicates that the electron path ways are effectively established when the MWCNT increase the point and the surface conductivity between the cathode material particles even in the same amount of carbon materials. Further, electrochemical aspects of C-OLO were evaluated with coin half cell and the rate capability of the C-OLO under 2 C rate was highly improved (199.5 vs. 157.1 mAh g-1 at 2 C). This means the intrinsic poor electronic conductivity of OLO provokes the kinetic resistance and this is highly relieved by MWCNT coating on the OLO materials. And furthermore, the C-OLO shows the high capacity over 180 mAh even at the 1 C condition with only 3 wt.% carbons, (cf. untreated OLO exhibits low capacities around 140 mAh g-1). In summary, the MWCNT coating enhances the electronic conductivity of OLO, it could be a solution for improving the rate capability and the usable specific capacity. Although carbon is hard to be coated on the oxide cathode materials, the highly conductive MWCNT was successfully coated on the OLO by the physical coating process. The characteristic of coated OLO was elucidated by XPS and HR-SEM and the improvement of electronic conductivity was checked. MWCNT coated OLO shows a superior rate capability and the cycleability to the bare OLO.