Solid state batteries with sulfide-based solid electrolytes

Inorganic solid electrolytes are promising for the solution to the safety issue of lithium batteries. In spite of this advantage, solid state lithium batteries are, in general, lower in energy density than organic electrolyte systems. This paper presents two points, to which we have to direct our attention: compatibility of solid electrolytes with electrode materials and novel electrode materials functional only in solid systems. The consideration for the compatibility lead us to a unique construction of a solid state lithium battery employing two kinds of solid electrolytes, which enabled us to realize C/LiCoO2 solid state batteries with a high energy density. Ion-selectivity of solid electrolytes made materials that are not available in liquid system functional in solid ones. Some examples are also presented in this paper.