Synergistic Li₆PS₅Cl@Li₃OCl Composite Electrolyte for High-Performance AllSolid-State Lithium Batteries

Li₆PS₅Cl is a highly wanted sulfide-solid-electrolyte (SSE) for developing allsolid-state lithium batteries, due to its high ionic conductivity, good processability and abundant compositional elements. However, its cyclability is poor because of harmful side reactions at the Li₆PS₅Cl/Li interface and growth of lithium dendrites inside Li₆PS₅Cl phase. Herein, we report a simple interface-engineering remedy to boost the electrochemical performance of Li₆PS₅Cl, by coating its surface with a Li-compatible electrolyte Li₃OCl having low electronic conductivity. The obtained Li₆PS₅Cl@Li₃OCl core@shell structure exhibits a synergistic effect. Consequently, compared with the bare Li₆PS₅Cl, this composite electrolyte exhibits great performance improvements: 1) In Li|electrolyte|Li symmetric cells, the critical current density at 30℃ gets increased from 0.6 mA/cm² to 1.6 mA/cm², and the lifetime gets prolonged from 320 h to 1400 h mA/cm²; 2) In Li|electrolyte|NCM721 full cells running at 30°C, the cycling capacity at 0.2 C (or 0.5 C) gets enhanced by 20% (or from unfeasible to be feasible) for 100 cycles and the rate capability reaches up to 2 C from 0.2 C; and in full cells running at 60°C, the cycling capacity is increased by 7% at 0.2 C and the rate capability is enhanced to 3.0 C from 0.5 C. The experimental studies and theoretical computations show that the performance enhancements are due to the confined electron penetration and suppressed lithium dendrites growth at the Li₆PS₅Cl@Li₃OCl interface.