Ternary doped iodine-enriched argyrodite solid electrolyte with superior air stability and excellent lithium compatibility for all-solid-state Li metal batteries

초록

Li6PS5I is a promising sulfide-based solid-state electrolyte (SSE) for all-solid-state lithium metal batteries (ASSLMBs) due to its low cost and favorable interfacial stability. However, its practical applications are limited by relatively low ionic conductivity and poor moisture sensitivity upon air exposure. In this study, we propose a halide-oxide dual-doping strategy to simultaneously enhance both ionic conductivity and air stability of argyrodite-type Li6PS5I. By partially substituting Cl_ for I_ and incorporating Sb2O5 as a dopant, we have synthesized a series of Li6P1-xSbxS5-2.5xO2.5xI0.3Cl0.7 (x = 0 to 0.08) solid electrolytes via a conventional solid-state process. The Cl_ substitution promotes anion site disorder and facilitates Li+ transport, while Sb2O5 doping induces the formation of Sb-S and P-O bonds, suppressing H2S emission under humid conditions. The optimized composition Li6P0.98Sb0.02S4.95O0.05I0.3Cl0.7 (x = 0.02) exhibits a high ionic conductivity of 1.158 mS cm_1 and significantly improved air stability, with HAS emission reduced by 40% under 30% relative humidity. The Li symmetric cells employing Li6P0.98Sb0.02S4.95O0.05I0.3Cl0.7 (x = 0.02) electrolyte demonstrate an excellent critical current density (CCD) of 0.52 mA cm_ 2 and stable cycling performance over 1000 h, which is attributed to the presence of LiI and the formation of a Li-Sb alloy for excellent interfacial stability. Furthermore, ASSLMBs incorporating the Li6P0.98Sb0.02S4.95O0.05I0.3Cl0.7 (x = 0.02) electrolyte have achieved a high initial discharge capacity of 158.4 mAh g_ 1 and maintained stable operation over 100 cycles. This work demonstrates that the proposed ternary doping strategy offers a viable pathway toward the development of high-performance ASSLMBs by overcoming trade-offs between ionic conductivity and air stability.

키워드