Aqueous solution synthesis of lithium-ion conductive tin-based sulphide electrolytes†

To overcome the challenges associated with the toxicity of the majority of organic solvents for the liquid phase synthesis of solid electrolytes toward the human body and environment, we demonstrate the synthesis of tin-based sulphide electrolytes using water, which is the most environmentally friendly solvent. ortho-Thiostannate, i.e., Li₄SnS₄, was obtained from a mixture of Li₂S, Sn, and S using aqueous solution synthesis. Furthermore, Li₁₀SnP₂S₁₂, a superionic conductor, was obtained by mixing an aqueous solution of Li₄SnS₄ and tetrahydrofuran suspension of Li₃PS₄, which exhibited the highest ionic conductivity (5.9 × 10⁻³ S cm⁻¹ at 25 °C) in liquid-phase synthesis. This study successfully demonstrates that water can be efficiently used to synthesize sulphide electrolytes instead of conventional organic solvents.