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 (6.02 × 10^-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.