Research on highly reliable solid-state lithium batteries in NIRIM

Electrochemical reactions of LiVS2, Li2FeS4, and Li4FeS2 were investigated by using a Li+ ion conductive glass, 0.01Li3PO4–0.63Li2S–0.36SiS2, as an electrolyte. The results showed remarkable differences from that in liquid electrolyte; the redox couples of both Li2VS2/LiVS2 and LiVS2/VS2 were highly reversible, the reduction of Li2FeS2 led to the metastable phase Li4FeS2 that was completely reoxidized to the initial phase, and Li+ ions were extracted from Li2FeCl4 without dissolution of the chloride itself. These improvements by using the solid electrolyte make a large choice of electrode materials.