In order to improve the electric range of EV on one charge, Toyota has challenged to develop all solid state battery as the most practical candidate of beyond lithium ion batteries (LIBs). It is known that inorganic solid electrolytes provide some advantages compared with an organic electrolyte for conventional LIBs, such as high lithium ion transference number, wide electrochemical potential window and thermal stability. These advantages would enable to design a high energy density type of battery package.
Also, lithium ion conductivity is a key characteristic of electrolyte for high rate battery. In general, sulfide electrolyte shows higher conductivity than oxide, polymer and other solid electrolytes. In this lecture, I will introduce the study of lithium ion conductivity mechanism of sulfide solid electrolyte and the battery performance when the sulfide solid electrolyte is used, in comparison with conventional liquid system lithium ion battery.