Enhancing solid-state lithium metal battery performance via indium-based modification of electrolytes and lithium metal surfaces: mechanistic insights and optimization

Argyrodite-based solid-state lithium metal batteries exhibit significant potential as next-generation energy storage devices. However, their practical applications are constrained by the intrinsic poor stability of argyrodite towards Li metal and exposure to air/moisture. Therefore, an indium-involved modification strategy is employed to address these issues. The optimized doping yields a high Li-ion conductivity of 7.5 mS cm⁻¹ for Li_5.54In_0.02PS_4.47O_0.03Cl_1.5 electrolyte, accompanied by enhanced endurance against air/moisture and bare Li metal. It retains 92.0% of its original conductivity after exposure to air at a low dew point of −60 °C in dry room. Additionally, a composite layer comprising Li–In alloy and LiF phases is generated on the surface of lithium metal anode via the reaction between InF₃ and molten Li. This layer effectively mitigates Li dendrite growth by creating a physical barrier from the robust LiF phase, while the Li–In alloy induces uniform Li-ion deposition and accelerates Li transport dynamics across the interphase between the solid electrolyte/Li metal. Moreover, the In-doped electrolyte facilitates the in-situ generation of Li–In alloy within its voids, reducing local current density and further inhibiting lithium dendrite growth. Consequently, the combination of the Li_5.54In_0.02PS_4.47O_0.03Cl_1.5 electrolyte and the InF₃@Li anode provides exceptional electrochemical performances in both symmetric cells and solid-state lithium metal batteries across different operating temperatures. Specifically, the LiNbO₃@LiNi_0.7Co_0.2Mn_0.1O₂/Li_5.54In_0.02PS_4.47O_0.03Cl_1.5/InF₃@Li cell delivers a high discharge capacity of 167.8 mAh g⁻¹ at 0.5 C under 25 °C and retains 80.0% of its initial value after 400 cycles. This work offers a viable strategy for designing functional interfaces with enhanced stability for sulfide-based solid-state lithium batteries.