Nanoconfined Polymerization Facilitates Efficient Li+ Transportation in Quasi‐Solid Electrolytes

Conventional gel polymer electrolytes (GPEs) struggle with lithium dendrite growth and long‐term cycling stability due to low ionic conductivity. A nanoconfined polymerization (NCP) strategy was employed to develop a composite GPE (PDA@CityU‐43) comprising porous COF and linear polymers. The crosslinked polymer chains are confined within the nanopores of CityU‐43 along c‐direction, improving polymer distribution and filler‐polymer compatibility. The PDA@CityU‐43 achieves a high ionic conductivity (6.02Í10‐3 S cm‐1 at 25 °C) and a high Li+ transference number (0.82), which is favorable to enhance Li+ transport dynamics and induce uniform Li+ deposition. Thus, the Li||Li cell can stably operate over 6000 h at 0.1 mA cm‐2 and 0.1 mAh cm‐2. The Li||PDA@CityU‐43||LFP demonstrates significantly improved cycling stability at 5C, a reversible capacity of 108 mAh/g after 300 cycles. The Li||PDA@CityU‐43||NCM811 cells with high mass loading (~5.8 mg cm‐2) exhibits 72.5% capacity retention after 100 cycles. This NCP strategy offers a new approach to designing advanced GPEs for Li metal batteries.