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

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_0.8Co_0.1Mn_0.1O₂||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.