A Large-Area Uniform Three-Dimensional Covalent Organic Framework Membrane for Stabilizing Li-Metal Electrodes via Solvation Cages

Covalent organic frameworks (COFs), known for their ordered structures, hold promise as ion-conducting materials in cells/batteries. Nevertheless, the rigid cross-linking of porous materials prevents them from being processed into membranes, while composite membranes weaken the material's conductivity advantage due to phase interruptions. Here, we report a phase-continuous 3-dimensional COF (3D-COF) membrane with a large size of 15 cm × 25 cm, fabricated via in situ interfacial engineering. The COF membranes possessed a non-interpenetrating dia topology that facilitated 3D continuous ionic pathways at the molecular level. Further, the hydroxyl and imine groups on the framework could form Li⁺-solvation cages, providing the hydrogen-bonding locking sites that facilitate the conversion of the Li-solvates into more readily reducible species. Combined with the dense nanoporous feature, this 3D-COF membrane was found to be very effective in inhibiting Li-dendrites and parasitic reactions and demonstrated a stabilizing effect and good cycling performance in the Li|NMC622 batteries.