Hunting highly conductive Li₆PS₅I electrolyte via Sn-Cl dual doping for solid-state batteries

The low Li-ion conductivity and poor interfacial compatibility towards cathode/anode materials of Li₆PS₅I solid electrolytes have significantly impeded their applications in all-solid-state batteries. This work developed a facial design strategy to improve the ionic conductivity and lithium metal compatibility of Li₆PS₅I electrolyte by the Sn-Cl dual doping. The optimal Li_6.6P_0.8Sn_0.2S₅I_0.6Cl_0.4 electrolyte shows ultrahigh conductivity up to 0.96 mS/cm and enhanced lithium metal compatibility. The assembled battery using LiNi_0.6Mn_0.2Co_0.2O₂ cathode and Li-In anode delivers a high initial discharge capacity of 175.7 mAh/g at 0.1C and maintains 79.2% after 100 cycles. Moreover, the corresponding battery using lithium metal anode displays a higher initial capacity (137.7 mAh/g vs. 112.7 mAh/g) and superior cyclability. The superior battery performances are attributed to the smaller interfacial resistances of those solid electrolyte-involved interfaces due to the Sn-Cl dual doping. This work demonstrates that the dual doping strategy is an effective route to exploring highly conductive Li₆PS₅I electrolytes.