Bespoke Dual‐Layered Interface Enabled by Cyclic Ether in Localized High‐Concentration Electrolytes for Lithium Metal Batteries

Abstract Lithium metal anodes (LMAs) are regarded as a highly promising candidate for next‐generation batteries owing to their exceptional energy density. Nevertheless, the instability of the interphase poses significant safety and degradation challenges for LMAs, thereby impeding their feasibility for commercial application. Herein, based on the lessons learned from the stable solid‐electrolyte‐interface (SEI) layer formed with ethylene carbonate (EC) solvents for graphite anodes, the effects of cyclic‐ethers are systematically investigated in localized high concentration electrolytes (LHCEs) using tetrahydrofuran (THF), 1,3‐dioxolane (DOL), and 1,4‐epoxybuta‐1,3‐diene (Furan) as co‐solvents. When using DME and THF as co‐solvents, the most stable interface, a LiF‐rich SEI layer with a polymeric outer‐layer, is formed, elongating the cyclability of the Li | Li symmetric cells up to 1200 h at 1 mA cm −2 and 1 mAh cm −2 . This research gives useful insight into how to enhance the mechanical strength of the SEI layer with polymeric compounds by incorporating cyclic‐ether co‐solvents in LHCEs.