Regulating water molecules via bioinspired covalent organic framework membranes for Zn metal anodes

Abstract

The Zn metal anode in aqueous zinc-ion batteries (AZIBs) faces daunting challenges including undesired water-induced parasitic reactions and sluggish ion migration kinetics. Herein, we develop three-dimensional covalent organic framework (COF) membranes with bioinspired ion channels toward stabilized Zn anodes. These COFs, featured by zincophilic pyridine-N sites, enable effective regulation of water molecules at the anode-electrolyte interphase. Systematic experimental analysis and theoretical simulations reveal the optimized COF-320N membrane functions as ion pumps, accordingly facilitating Zn²⁺ transport and inhibiting direct contact between Zn anode and free water molecules. Consequently, the bio-inspired strategy achieves improved Zn²⁺ transference number (0.61), rapid de-solvation kinetics, and suppressed hydrogen evolution. The assembled Zn MnO₂ pouch cell integrated with COF-320N membrane exhibits favorable electrochemical performances. Such a bioinspired concept for optimizing Zn anodes opens new pathways in developing advanced energy storage devices.