Covalent organic framework-mediated Nafion Superhydrophobic coating for stabilizing the anode of aqueous zinc-ion batteries

Despite their high energy density, cost-effectiveness and operational security , aqueous zinc-ion batteries (AZIBs) are hindered from commercialization by two critical anode issues: Zn dendrite growth and the hydrogen evolution reaction (HER). This work fabricates a superhydrophobic COF/Nafion coating for stabling the Zn anode of the AZIBs by drop-casting COF/Nafion solution containing the Py-DMTP covalent organic framework (COF) onto the surface of the Zn anode, regulating the Zn deposition behavior at the anode for suppressing dendrite growth and HER. The superhydrophobic COF/Nafion coating on the Zn anode (Zn@COF/Nafion) markedly lowers the nucleation overpotential, facilitating the transition of Zn 2+ diffusion from a 2D model to a 3D one during Zn deposition, thus mitigating concentration polarization and enabling uniform Zn plating. Furthermore, the zincophilic functional groups (-NH 2 in COF and -SO 3 H in Nafion) enhance the desolvation of [Zn(H 2 O) 6 ] 2+ in the electrolyte, effectively suppressing side reactions such as HER. Consequently, batteries equipped with the Zn@COF/Nafion anode exhibit superior electrochemical performance. Zn@COF/Nafion||Zn cell maintains stable cycling over 420 h at 5 mA cm −2 and 5 mAh cm −2 , representing a sixfold enhancement over bare Zn anode. The Zn@COF/Nafion||NVO full cell maintains a capacity and retention rate of 165.71 mAh g −1 and 57.22 % after 1000 cycles at 5 A g −1 , markedly superiors to those of Zn||NVO cell (56.53 mAh g −1 and 20.25 %). The protection of the anode by the superhydrophobic COF/Nafion coating can significantly enhance the cycling stability of AZIBs, offering a novel strategy for optimizing the anode-electrolyte interface of AZIBs.