Enabling superior electrochemical performances of Li₁₀SnP₂S₁₂-based all-solid-state batteries using lithium halide electrolytes

Li₁₀GeP₂S₁₂ shows great potential as solid electrolytes for solid-state batteries due to its ultrahigh Li-ion conductivity. However, the high cost of Ge and the poor stability limit its applications. Replacing Ge with Sn can significantly lower the cost and maintains the high conductivity, while the corresponding Li₁₀SnP₂S₁₂ still suffers the low interfacial stability with the bare high voltage layered oxide cathodes. Herein, Li₁₀SnP₂S₁₂ with high Li-ion conductivity up to 4.79 mS cm⁻¹ has been synthesized. All-solid-state battery using the cathode consisting of bare LiNi_0.6Co_0.2Mn_0.2O₂ and Li₁₀SnP₂S₁₂ shows low capacities and poor cyclability due to side reactions between those two particles. To improve the interfacial stability, a highly conductive Li₃InCl₆ electrolyte is introduced both in the cathode mixture and between the cathode layer and Li₁₀SnP₂S₁₂ solid electrolyte layer. This new configuration delivers superior electrochemical performances at different operating temperatures. It delivers high initial discharge capacities of 176.1 mAh g⁻¹, 186.9 mAh g⁻¹, and 73.7 mAh g⁻¹ at 0.1C when operated at room temperature, 60 ^oC, and −20 ^oC, respectively. The superior battery performances are attributed to the excellent electrochemical stability of Li₃InCl₆ electrolyte towards bare LiNi_0.6Co_0.2Mn_0.2O₂ cathode. This work provides a guideline to design Li₁₀SnP₂S₁₂-based all-solid-state lithium batteries with high energy density and long span life.