Composite Lithium Protective Layer Formed In Situ for Stable Lithium Metal Batteries

Lithium metal is considered as the ideal anode for next-generation rechargeable batteries due to its highest theoretical specific capacity and lowest electrochemical potential. However, lithium dendrite growth during lithium deposition could lead to a short circuit and even cause severe safety issues. Here, we use solid-state electrolyte Li₃InCl₆ as an additive in nonaqueous electrolytes because of its high ionic conductivity (10^-3 to 10^-4 S cm^-1) and good electrochemical stability. It is found that Li₃InCl₆ can in situ react with metallic lithium to form a ternary composite solid electrolyte interphase (SEI) consisting of a Li-In alloy, LiCl, and codeposited Li₃InCl₆. The composite SEI can effectively suppress Li dendrite growth and thereby maintain stable long-term cycling performance in lithium metal batteries. The protected lithium electrode exhibits stable cycling performance in a symmetric Li|Li battery for nearly 1000 h at a current density of 1 mA cm^-2. Besides, the full battery with a LiFePO₄ cathode and a metallic lithium anode delivers a stable capacity of 140.6 mA h g^-1 for 500 cycles with a capacity retention of 95%. The Li|S battery with Li₃InCl₆-added LiTFSI in 1,3-dioxolane/1,2-dimethoxyethane electrolyte also shows significant improvement in capacity retention at 0.5 C. This work demonstrates an effective approach to design dendrite-free metal anodes.