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 rela