Designing solution chemistries for the low-temperature synthesis of sulfide-based solid electrolytes

Abstract

Developing synthesis methods for high quality solid electrolytes has been a key issue for enabling all-solid-state batteries. As compared to conventional methods using mechanical ball milling, liquid-phase synthesis methods would provide a facile way to produce solid electrolytes by reducing the reaction time and heating temperature. The simplified process is also potentially applicable to scalable manufacturing. Here, we introduce a new solution-based synthesis method for an Li₂S–P₂S₅ solid electrolyte by adding a nucleophilic agent, LiSC₂H₅. The strong nucleophile can break the P–S bonds of P₂S₅, fully dissolving the P₂S₅ in tetrahydrofuran (THF) and forming soluble intermediates. The modified synthesis protocol provides kinetically favorable conditions for P₂S₅ to react with the insoluble Li₂S, demonstrating the formation of a high quality β-Li₃PS₄ solid electrolyte (1.32 × 10⁻⁴ S cm⁻¹) with a uniform particle shape.