Regionally Localized Electrolyte Engineering via UV Crosslinking for Stable Ether–Carbonate Lithium Metal Batteries

ABSTRACT Electrolytes in Li metal batteries (LMBs) are employed primarily with ether‐ or carbonate‐based, each offering distinct interfacial advantages yet facing critical compatibility challenges. Ether‐based electrolytes exhibit high reductive stability toward Li metal but suffer from oxidative decomposition at high‐voltage cathodes. Conversely, carbonate‐based electrolytes maintain stability at the cathode but promote uneven SEI formation and dendritic lithium growth. Here, a regionally localized electrolyte (RLE) concept—an interface‐specific electrolyte design that spatially separates electrolyte functions is introduced. An ether‐rich electrolyte layer is locally immobilized on the lithium surface via a UV‐curable trimethylolpropane ethoxylate triacrylate (ETPTA) polymer matrix, while the bulk electrolyte remains carbonate‐based, enabling each to perform optimally at its respective interface. By tuning the ETPTA content, a balance between mechanical robustness and ionic mobility was achieved. Both experimental and theoretical analysis confirm that the optimized RLE anode promotes Li ⁺ ‐selective transport, effectively suppresses parasitic side reactions, and lowers interfacial overpotential. This leads to a more uniform Li deposition, and markedly improved cycling performance. Moreover, RLE facilitates sustained ion‐transfer stability and the formation of a homogeneous, LiF‐rich SEI layer. Overall, the RLE approach offers a practical electrolyte design framework to harmonize electrode interfaces and enhance the interfacial stability of high‐energy LMBs.