Sustainable synthesis of SiS2 for solid-state electrolytes by cascaded metathesis

Abstract

Sulfide-based electrolytes containing silicon offer high ionic conductivity and are employed in emerging solid-state batteries that are promising for electric vehicles due to their improved energy density and safety. However, their deployment is constrained by the high cost and low availability of the SiS2 precursor. Here we introduce a green, solution-based synthesis of SiS2 through coupled metathesis reactions. First, the key Li2S precursor is synthesized from the room-temperature reaction between abundant Na2S and LiCl in ethanol. Next, the Li2S is recovered from solution and combined with SiCl4 in ethyl acetate to form a SiS2 solution and regenerate LiCl. The synthesized Li2S and SiS2 are characterized and then combined to form a glassy solid electrolyte with a conductivity of 0.11 mS cm-1 at 30 °C, validating the utility of metathesis-derived metal sulfides to solid electrolyte synthesis. In this cascaded metathesis scheme the expensive components, LiCl and solvents, are recovered and recycled in a circular economy. The cascaded metathesis process can in principle be used to synthesize nearly any metal sulfide of interest to a wide range of applications including energy conversion/storage, catalysis, electronics, and optics.