Multisite Crosslinked Poly(ether‐urethane)‐Based Polymer Electrolytes for High‐Voltage Solid‐State Lithium Metal Batteries

Abstract Utilizing solid‐state polymer electrolytes (SPEs) in high‐voltage Li‐metal batteries is a promising strategy for achieving high energy density and safety. However, the SPEs face the challenges such as undesirable mechanical strength, low ionic conductivity and incompatible high‐voltage interface. Here, a novel crosslinked poly(ether‐urethane)‐based SPE with a molecular cross‐linked structure is fabricated to create high‐throughput Li ⁺ transport pathway. The amino‐modified Zr‐porphyrin‐based metal‐organic frameworks (ZrMOF) are introduced as multisite cross‐linking nodes and polymer chain extenders. The abundant ether/ketonic‐oxygen and Lewis acid sites in the SPE achieve high Li ⁺ conductivity (5.7 × 10 ⁻⁴ S cm ⁻¹ at 30 °C) and Li ⁺ transference number (0.84). The interpenetrating cross‐linked structure of SPE with robust mechanical strength results in a record cycle life of 8000 h in Li||Li symmetric cell. The high structural stability of ZrMOF and abundant electron‐withdrawing urethane/ureido groups in the SPE with high oxidation potential (5.1 V) enables a discharge capacity of 182 mAh g ⁻¹ at 0.3 C over 500 cycles in a LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ||Li cell. Remarkably, a high energy density of 446 Wh kg ⁻¹ in a 1.5‐Ah pouch cell is obtained with high loading cathode (≈4 mAh cm ⁻² ), demonstrating a great prospect of the current SPE for practical application in solid‐state, high‐voltage Li‐metal batteries.