Synthesis of lithium oxy-thiophosphate solid electrolytes with Li 10 GeP 2 S 12 structure by a liquid phase process using 2-propanol.

Lithium oxy-thiophosphates isostructural with Li 10 GeP 2 S 12 (LGPS) were synthesized by a liquid-phase process using 2-propanol as the solvent and Li 2 S and P 2 S 5 as the starting materials. The XRD and 31 P NMR results indicate that the synthesized compound has a slightly shrieked LGPS-type crystal structure where sulfur in PS 4 3- is partially replaced by oxygen. The sample synthesized from the nominal composition of Li 2 S : P 2 S 5 = 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.