Heat treatment effects in oxygen-doped β-Li3PS4 solid electrolyte prepared by wet chemistry method

Abstract

For advanced all-solid-state lithium batteries, the solid electrolyte is one of the most critical components that significantly affect battery performance. Herein, solid electrolytes 75Li2S·(25-x)P2S5·xP2O5 (mol%) are successfully prepared via wet chemistry method. Their XRD patterns show that only the crystalline phase β-Li3PS4 is detected for x\u2009=\u20090, 1, 2, 3, 5 mol% and the highest room-temperature ionic conductivity of 2.53\u2009×\u200910−4 S cm−1 is obtained when x\u2009=\u20092. Next, effects of heat treatment on the structure and electrochemical performance of 75Li2S·23P2S5·2P2O5 are systematically studied. The thermal stability, morphology, structure, and crystal phase of the 75Li2S·23P2S5·2P2O5 electrolyte heated at different temperatures are characterized by thermogravimetric analysis and differential scanning calorimetry (TGA-DSC), SEM, N2 adsorption/desorption, Raman, and XRD. The 75Li2S·23P2S5·2P2O5 electrolyte heat-treated at 320 °C exhibits the highest ionic conductivity of 2.72\u2009×\u200910−4 S cm−1, the lowest electronic conductivity of 4.8\u2009×\u200910−9 S cm−1, and excellent electrochemical stability against the metallic lithium electrode. When the heat treatment temperature further increases from 320 to 500 °C, the electrolyte partially decomposes into Li4P2S6 and Li2S. Our results underscore the importance of heat treatment for the synthesis and performance optimization of solid electrolytes for the application of high-energy solid-state batteries.