Hierarchical Ag Coating on Active Zinc Metal Powder Anodes via Galvanic Replacement for High‐Performance Aqueous Zn‐Ion Batteries

The energy storage performance of aqueous Zn‐ion batteries (AZIBs) is heavily influenced by the condition of the Zn metal anode. While using Zn metal powder (ZnMP) with a larger surface area, as opposed to Zn metal foil, can enhance the energy density of AZIBs, it also introduces surface‐related stability challenges. The increased surface area of ZnMP leads to more severe side reactions induced by free water and protruding dendrite growth, negatively impacting long‐term cyclability. To address these issues, Ag nanosheets (AgNSs) of controlled size are uniformly coated onto ZnMP via a simple galvanic replacement reaction (GRR) between Ag and Zn. Additionally, trisodium citrate dihydrate (TCD) is used as a stabilizer (a metal‐chelating agent) to regulate the GRR reaction rate. The slower reaction rate introduced by TCD ensures uniform and even deposition of AgNSs over the surface of ZnMP. The resulting AgNS‐coated ZnMP (Ag@ZnMP) anodes exhibit superior electrochemical properties, including higher energy densities, reduced hydrogen evolution, and improved cycling. A Ag@ZnMP symmetric cell demonstrates outstanding operational stability, maintaining performance for over 800 h at a current density of 2 mA cm −2 and a capacity of 1 mAh cm −2 . Furthermore, a Ag@ZnMP||MnO 2 full‐cell substantially enhances overall battery performance.