Basic study for the fabrication of all solid lithium battery

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All-solid state lithium secondary batteries are strongly desired as novel power sources with high performances because these solvent-free systems have higher safety and higher reliability than conventional lithium secondary batteries with liquid electrolytes. Thio-LISICON (LIthium SuperIonic CONductor), Li4-x Gel-x Px S4 is one of the best lithium ion conductive solids ever found in inorganic materials, and has sufficiently high conductivity, transport number, decomposition potential and thermal stability for practical use in battery. The purpose of the present study is to develop the all solid-state battery having excellent charge-discharge performance at high current density, and to characterize the interfacial behavior at various anode/electrolyte interfaces. The solid electrolyte interface (SEI) was found at Li-Al alloy/Li3.25Ge0.25P0.75S4 interface by x-ray diffraction pattern, x-ray photoelectron spectroscopy, ac impedance, and scanning electron microscopy. The SEI allowed the fastest electrochemical reaction between the anode and the electrolyte during charge-discharge process.The surface reaction and reaction mechanism of the lithium intercalation electrodes were studied using epitaxial cathode films of LiMO_2 (M=Co, Ni) and LiMn_2O_4 oxides with the layered rock-salt type and the spinel structure, respectively. The electrode films were successfully deposited on single crystal SrTiO_3 substrates by PLD method. The orientation of the epitaxial films was controlled with the substrate orientation. The anisotropic characteristics of lithium intercalation reaction and surface reaction for their cathode materials were clarified by in-situ synchrotron X-ray diffraction and reflectivity measurements in beam-line 14B1 at SPring-8.