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

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, Li₂O, and Li₂CO₃) stabilized the EEI, enabling stable cycling of the symmetric cell for 2000 h. Batteries assembled with a high-voltage Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ (LRMO) cathode retain a specific capacity of 217.37 mAh g^-1 after 250 cycles, and Ah-level pouch cell utilizing LiNi_0.8Co_0.1Mn_0.1O₂ (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.