Topologically Entangled Network Polymer Electrolyte with Ionophilic–Protonation Dual Side Chains for High‐Voltage Lithium‐Metal Batteries

Abstract The development of high‐voltage solid‐state lithium‐metal batteries (HVSSLMBs) is severely limited by unstable ion transport, insufficient oxidative stability, and poor electrode–electrolyte interface (EEI) compatibility of conventional solid electrolytes. Herein, we report a topologically entangled polymer electrolyte featuring ionophilic–protonation dual side chains. The ionophilic functional groups on these side chains provide abundant coordination sites, significantly enhancing Li + transport, whereas exposed carboxyl (─COOH) groups induce protonation on the cathode surface, effectively suppressing transition metal (TM) ion migration. The topologically entangled polymer network ensures uniform electric‐field distribution, mitigates lattice‐oxygen release, and maintains continuous Li + conduction. As a result, this electrolyte achieves a high room‐temperature ionic conductivity of 0.81 mS cm −1 and an oxidation stability up to 4.9 V. Moreover, the in situ formed inorganic species (LiF, Li 2 O, and Li 2 CO 3 ) stabilized the EEI, enabling stable cycling of the symmetric cell for 2000 h. Batteries assembled with a high‐voltage Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O 2 (LRMO) cathode retain a specific capacity of 217.37 mAh g −1 after 250 cycles, and Ah‐level pouch cell utilizing LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode exhibits stable cycling performance over 150 cycles. These findings demonstrate the great promise of this strategy for the development of high‐energy‐density lithium‐metal batteries with outstanding cycling performance and long‐term stability.