Bimetallic Modification Strategy: Ultra-Thin Ni-Ag Coating Prepared via One-Step Method Enables Highly Reversible Zn Anode

For aqueous zinc ion batteries (AZIBs), Zn dendritic growth and hydrogen evolution reaction (HER) usually result in the severe degradation of bare Zn anodes. Although the alloy-modified anodes can improve the reversibility of the Zn plating/stripping process, the regulation of alloy components is too complex to meet the requirements for large-scale fabrication. Herein, a Ni-Ag bimetallic coating on Zn foils (Ni-Ag@Zn) is prepared by magnetron co-sputtering. Owing to this bimetallic coating with the ultrathin thickness of 200 nm, the cycling life of Ni-Ag@Zn-based symmetric cells attains more than 5000 h at current density of 1 mA/cm 2 and areal capacity of 1 mA h/cm 2 , exceeding most of the reported binary/ternary-alloy-based symmetric cells. To the suppression of dendrite growth and HER, the regulation mechanism of the bimetallic coating on Zn deposition is assigned to the synergistic effect, the suppressed HER by the strong adsorption of Ag with H ions and the flatted Zn deposition via the strong adsorption of Ni/Ag with Zn ions. To our knowledge, both the bimetallic and ultrathin features have not been reported to optimize the anodes for AZIBs. The present bimetallic coating strategy renders the diversification of anode modification for the commercialization of high-performance AZIBs.