“Pumping” Trace Cu Impurity out of Zn Foil for Sustainable Aqueous Battery Interface

Abstract Dendritic zinc (Zn) electrodeposition presents a significant obstacle to the large‐scale development of rechargeable zinc‐ion batteries. To mitigate this challenge, various interfacial strategies have been employed. However, these approaches often involve the incorporation of foreign materials onto Zn anode surface, resulting in increased material costs and processing complexities, not to mention the compromised interface endurability due to structural and compositional heterogeneity. Realizing that Cu atoms typically exist as trace impurities in commercial Zn, a novel approach is demonstrated that leverages these Cu impurities to create a Cu‐rich surface for effective modulation of Zn electrodeposition. By simply heating commercially available Zn foil with a naturally oxidized surface, not only the internal Cu atoms are thermally activated to become diffusible, their diffusion is also navigated toward the surface via oxygen attraction. The resulting Cu‐rich surface effectively regulates Zn electrodeposition, comparable to conventional interfacial strategies, yet exhibits superior cycling durability. 3D in situ microscopy confirms that this Cu‐rich surface enables dendrite‐free, compact, and (101)‐oriented Zn electrodeposition, contrasting with the traditional (002)‐oriented dendrite‐suppression mechanism. By transforming trace Cu impurity within Zn foil into a Cu‐rich surface, this work demonstrates a straightforward, cost‐effective and efficient method for controlling Zn electrodeposition.