High lithium ion conducting glass-ceramics in the system Li 2S–P 2S 5

Abstract

Highly ion-conductive Li 2S–P 2S 5 glass-ceramic electrolytes were prepared by controlling the compositions and heat treatment temperatures of the glasses. The 70Li 2S·30P 2S 5 (mol%) glass-ceramic heated at 360 °C showed the highest conductivity of 3.2 × 10 − 3 S cm − 1 at room temperature and the lowest activation energy of 12 kJ mol − 1 for conduction in the binary system Li 2S–P 2S 5. The outstanding property was attributed to both the precipitation of the new crystal as a metastable phase and the increase in crystallinity of the phase. With increasing heat treatment temperatures, the metastable phase changed into thermodynamically stable phases such as the Li 4P 2S 6 crystal by heat treatment up to 550 °C, resulting in low conductivities of the glass-ceramics. It was, thus, found that the formation of superionic metastable phases by heating the Li 2S–P 2S 5 glasses is responsible for the marked enhancement on the conducting properties of the glass-ceramics.