Study On Interface Properties And Application Of Inorganic Li-ion Solid Electrolyte

The development of all-solid-state batteries and hybrid electrolyte lithium/airbatteries, as next generation batteries, are paied more attention. The research aboutlithium-ion solid electrolyte is a focus of the development on new series of lithiumbattery. The preparation and application research of lithium-ion solid electrolyte is keyand breakthrough point of the development. In this paper, the Li₂O-Al₂O₃-TiO₂-P₂O₅（LATP）and Li₂O-Al₂O₃-TiO₂-P₂O₅（LAGP） glass-ceramic electrolyte, and LiPONelectrolyte was prepared and researched. In hybrid Li/air batteries, the interfacialkinetic of LAGP solid electrolyte plate was studied by AC impedance spectroscopy（electrochemical impedance spectroscopy）, and modified at interface for improvingthe discharge performance of Li/air battries.In this work, the LATP and LAGP plate that was NASICON type solid electrolytewere prepared. The Li-ion conductivity of them reached4×10^-4S/cm and5.7×10_-4S/cm, respectively. A water stable lithium electrode （WSLE）, prepared by theLAGP and LATP solid electrolyte plate, was stably working in aqueous solution.However, as a result of introducing the solid electrolyte plate, the impedance of Li/airbatteries with WSLE was increased. Then, the output power of hybrid electrolyteLi/air batteries using WSLE was low.In order to solve the technical problem of hybrid electrolyte Li/air battery, such asbig internal resistance and low output power, the interface impedance of WSLE inaqueous solution was analyzed and discussed. The3-electrode and4-electrode testcell was designed for AC impedance spectroscopy experiment. And the ACimpedance spectra were fitted and analyzed. According to the analysis results, thelithium electrode/organic electrolyte interfacial impedance increased with time due togrowth of SEI layer, and gradually became the main impedance of Li/air battery atOCP. However, when the lithium electrode was polarized, as interface polarizationand the break of SEI layer, the interfacial impedance of lithium electrode/organicelectrolyte dramatically decreased. And the impedance of lithium electrode/organicelectrolyte interface could be reduced to a negligible level by the suitable organicelectrolyte. During the discharge polarization, the organic electrolyte/solid electrolyteinterface impedance is the limited step of discharge in hybrid electrolyte Li/air battery. And the impedance of organic electrolyte/solid electrolyte interface was affected bytemperature. The interface impedance was significantly reduced with temperatureincreasing. In order to reduce the impedance of organic electrolyte/solid electrolyteinterface, a modified layer was designed. The LTO modified layer was prepared byRF magnetron sputtering at the organic electrolyte surface. The modified layersignificantly reduced the impedance of organic electrolyte/solid electrolyte interface,and enhanced the discharge performance of hybrid electrolyte Li/air battery over80%.In this paper, the application of solid electrolyte in all-solid-state battery was alsostudied. An all-solid-state thin film battery was designed and prepared, using LiPONsolid electrolyte film. ALiCoO2positive film was prepared without annealing, and thealuminum film was deposited as current collector. The specific capacity of LiCoO2positive film can reach60μAh/cm2μm. The Al current collector, instead of Pt currentcollector, reduced the cost of battery. The elimination of annealing step improved themanufacture process. By magnetron sputtering, an all-solid-state thin film battery withthe “Al/LiCoO₂/LiPON/Cu” structure was prepared and conducted10cycles chargingand discharging test under Ar atmosphere.