Synthesis, structure, and electrochemical properties of crystalline Li-P-S-O solid electrolytes: Novel lithium-conducting oxysulfides of Li10GeP2S12 family

Novel lithium-ion (Li+)-conducting oxysulfides of the Li10GeP2S12 family were found in the ternary Li2S-P2S5-P2O5 system; Li10GeP2S12-type solid solutions with compositions Li3 + 5xP1 − xS4 − zOz (x = 0.03-0.08, z = 0.4-0.8) were confirmed. The solid solutions showed ionic conductivities from 4.14 × 10− 5 to 2.64 × 10− 4 S cm− 1 at 298 K and a wide electrochemical window of 0-5.0 V (vs. Li/Li+). Among the solid solutions synthesized, the purest phase had the composition Li3.35P0.93S3.5O0.5 (x = 0.07, z = 0.5). Structural analysis revealed that the novel oxysulfides are isostructural to the original Li10GeP2S12 structure and the (P/□)(S/O)4 tetrahedra, which indicates the presence of cation defects with oxygen substitution in the crystal structure. Electrochemical stability of the oxysulfides was confirmed in the voltage range of 0-5.0 V. The solid-electrolyte interphase (SEI) resistivity and its cycle-dependence evaluation for new materials demonstrated that the oxysulfides had lower resistivities and furnished well-contacted SEI layers during the charge-discharge process.