Synthesis of lithium oxy-thiophosphate solid electrolytes with Li10GeP2S12 structure by a liquid phase process using 2-propanol.

Lithium oxy-thiophosphates isostructural with Li10GeP2S12 (LGPS) were synthesized by a liquid-phase process using 2-propanol as the solvent and Li2S and P2S5 as the starting materials. The XRD and 31P NMR results indicate that the synthesized compound has a slightly shrieked LGPS-type crystal structure where sulfur in PS43- is partially replaced by oxygen. The sample synthesized from the nominal composition of Li2S : P2S5 = 2.5 : 1 and at the annealing temperature of 300 °C exhibited the ionic conductivity of 1.6 × 10-4 S cm-1 at 25 °C. The synthesized solid electrolyte was found to be electrochemically stable in the potential range of 0-5 V, and also relatively stable under air with low relative humidity.