Various solid electrolytes,such as sulfides (10-3-10-2 S cm-1)and oxides (10-4-10-3 S cm-1) are explored and developed to solve the safety problems in commercial Li-ion batteries using liquid flammable electrolytes.Metallic Li anode is required for pursuing high power density (＞300Wh kg-1) for solid-state batteries [1,2].However,sulfide electrolytes react with Li and the products are ionic/electronic insulators Li3P and Li2S [3-6].