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

Antimony-based sulfide solid electrolyte Na 3 SbS 4 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 Na 3 SbS 4 by liquid-phase reaction of Na 2 S, Sb 2 S 3 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 Na 3 SbS 4 (t-Na 3 SbS 4 ) 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-Na 3 SbS 4 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). Graphical Solid electrolyte ! The reaction processes of synthesizing Na 3 SbS 4 by liquid-phase reaction using acetonitrile are extensively investigated, and tetragonal Na 3 SbS 4 with high ionic conductivity (0.46 mS cm −1 ) is obtained after heating at 450 °C. Remarkably, the tetragonal Na 3 SbS 4 is further prepared into a sheet-type electrolyte membrane (0.17 mS cm −1 ) using polytetrafluoroethylene.