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

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.