Formation Process of Na3SbS4 Solid Electrolyte via a Liquid‐Phase Reaction Using Acetonitrile

Abstract

AbstractAntimony‐based sulfide solid electrolyte Na3SbS4 with good moisture stability is attractive for practical application in all‐solid‐state sodium batteries. Liquid‐phase reaction is a facile and widely‐used strategy, but the specific reactions in synthetic process and related mechanisms are still unclear. Herein, the reaction processes of synthesizing Na3SbS4 by liquid‐phase reaction of Na2S, Sb2S3 and S in acetonitrile (ACN) are extensively investigated. A colorless supernatant and dark green precipitate are obtained after reacting for 24 h, the raw materials are negligible in supernatant. More importantly, the post‐treatment temperature is investigated and the tetragonal Na3SbS4 (t‐Na3SbS4) with high ionic conductivity (0.46 mS cm−1 at 25 °C) is obtained after heating at 450 °C for 3 h. Remarkably, the direct stacking of electrolyte is developed and t‐Na3SbS4 is further prepared into a free‐standing sheet‐type solid electrolyte membrane using polytetrafluoroethylene (PTFE) fibrillation, then an ionic conductivity is achieved (0.17 mS cm−1 at 25 °C).