Li 4 SiO 4 Doped-Li 7 P 2 S 8 I solid electrolytes with high lithium stability synthesised using liquid-phase shaking.

In this study, mechanical milling and liquid-phase shaking are used to synthesise 3Li 2 S·P 2 S 5 LiI· x Li 4 SiO 4 (Li 7 P 2 S 8 I· x Li 4 SiO 4 ) solid electrolytes. When mechanical milling is used, the electrolyte samples doped with 10 mol% of Li 4 SiO 4 (Li 7 P 2 S 8 I·10Li 4 SiO 4 ) 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 Li 7 P 2 S 8 I·10Li 4 SiO 4 has excellent long-term cycling stability in excess of 680 cycles (1370 h), indicating that it is highly compatible with Li. Thus, Li 7 P 2 S 8 I solid electrolytes doped with Li 4 SiO 4 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 Li 4 SiO 4 doping, which can be used to improve the ionic conductivity and stability against Li anodes with Li 7 P 2 S 8 I solid electrolytes.