Enhanced ionic conductivity of sulfide solid electrolyte with high lithium content based on cryomilling

Considering the high ion conductivity and good machining properties of lithium thiophosphate (LPS), it has attracted increasing attention as a solid electrolyte for all-solid-state batteries. Chemical and thermal stability can be significantly enhanced by increasing lithium content. However, in past reports, the lithium content of LPS is commonly less than 40 %. LPS with high lithium content (Li > 40 at%) shows low ion conductivity and high grain boundary resistance. In the present work, LPS with 47.2 at% lithium was prepared by cryomilling and solid-state reaction, avoiding crystallization and adhesion in the ball milling process. By improving the ball milling process, the ion conductivity (1.36 mS/cm) and ion activation energy (10.80 kJ/mol) were optimized by 106.1 % and 41.5 %, respectively. The resulting all-solid-state battery showed a high capacity retention of 104 % after 100 cycles.