Li4SiO4 Doped-Li7P2S8I solid electrolytes with high lithium stability synthesised using liquid-phase shaking

Abstract

In this study, mechanical milling and liquid-phase shaking are used to synthesise 3Li₂S·P₂S₅ LiI·xLi₄SiO₄ (Li₇P₂S₈I·xLi₄SiO₄) solid electrolytes. When mechanical milling is used, the electrolyte samples doped with 10 mol% of Li₄SiO₄ (Li₇P₂S₈I·10Li₄SiO₄) have the highest ionic conductivity at ∼25–130 °C. When liquid-phase shaking is used, they exhibit a relatively high conductivity of 0.85 mS cm⁻¹ at ∼20 °C, and low activation energy for conduction of 17 kJ mol⁻¹. A cyclic voltammogram shows that there are no redox peaks between −0.3 and +10 V, other than the main peaks near 0 V (v.s. Li/Li⁺), indicating a wide electrochemical window. The galvanostatic cycling test results demonstrate that the Li₇P₂S₈I·10Li₄SiO₄ has excellent long-term cycling stability in excess of 680 cycles (1370 h), indicating that it is highly compatible with Li. Thus, Li₇P₂S₈I solid electrolytes doped with Li₄SiO₄ are synthesised using the liquid-phase shaking method for the first time and achieve a high ionic conductivity of 0.85 mS cm⁻¹ at 25 °C. This work demonstrates the effects of Li₄SiO₄ doping, which can be used to improve the ionic conductivity and stability against Li anodes with Li₇P₂S₈I solid electrolytes.