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A solvothermal synthesis is developed to build a 3D network of nanoparticles, enhancing the electrochemical performances of both TiNb 2 O 7 and Ti 2 Nb 10 O 29 , especially at high current densities, with up to 190 mAh g -1 at 10C. A set of 11 mAh pouch cells combining the nanosized TiNb 2 O 7 with LiMn 1.5 Ni 0.5 O 4 is tested and is the first to be reported for this material. Soft shell cells are used, not only to evaluate the electrochemical performances of this oxide in a larger scale battery, but also to assess its gassing behavior, a well-known limitation for application of Li 4 Ti 5 O 12 in hybrid electric vehicles. In order to evaluate the sole contribution of TiNb 2 O 7 to the swelling, an additional set of soft shell TiNb 2 O 7 /Li(Ni 1/3 Mn 1/3 Co 1/3 )O 2 cells is assembled and stored at 45 ºC in a charged state. A higher swelling behavior is observed for TiNb 2 O 7 in comparison to Li 4 Ti 5 O 12 ; a clear trend also appears between surface area of the oxide and amount of gassing. The swelling of TiNb 2 O 7 or Ti 2 Nb

Two classes of cathode materials have been developed for high energy density applications. The Li-rich layered oxide material with the general formula Li1+xM1-xO2 (M = Ni, Mn, Co) and the lithium manganese silicate Li 2 MnSiO 4 . Both materials have theoretical capacities higher than commercialized ones, which may give rise to higher energy density batteries. Li-rich materials have been prepared by solid state and co-precipitation routes. Transmission Electron Microscopy (TEM) characterization showed an irreversible evolution of the structure through a spinel phase during the first charge. Electron Energy Loss Spectroscopy (EELS) also showed a continuous cation migration during cycling of the material leading to charge/discharge voltage decay. The redox process has been studied by X-Ray Diffraction (XRD) in synchrotron facilities (ESRF, Grenoble, France). Ni/Mn ratio has been identified to have a great role on capacity fading of the material. Finally, a Li-rich optimized composition has been prepared and stable reversible capacity of 250 mAh.g -1 has been obtained. Li2MnSiO4 has a large theoretical specific capacity (333 mAh/g) through exchange of 2 lithium ions per formula unit. The thermal stability due to strong Si-O bonds makes Li2MnSiO4 a very promising material for future energy storage in space applications. Preparation in inert atmosphere showed beneficial improvements of LMSO's electrochemical properties. Nano-sizing and carbon coating have been effective ways to improve electronic conductivity and therefore electrochemical performance. Up to 1.66 Li per formula unit can be reinserted in the 1 st cycle. XRD analysis showed complete amorphization of Li2MnSiO4 after the 1 st charge at 4.8 V with complete modification of the charge/discharge curves in the next cycles. Increasing the carbon coating ratio limits capacity loss during cycling but did not avoid amorphization. Finally influence of voltage window on structure stability was investigated. Careful choice of upper limit voltage has been showed to stabilize Li2MnSiO4 structure but for now is still limited to low Li + insertion/extraction from the host material.