Copper Surface Engineering Enables Uniform Zn Plating in Zn Batteries at Unity N/P Ratio

Zinc (Zn) metal plating is notoriously sensitive to interfacial inefficiencies under Zn‐limited conditions, where small losses of active Zn rapidly lead to premature cell failure. Here, we demonstrate a surface reconstruction strategy for copper (Cu) current collectors that enables exceptional performance at a negative‐to‐positive (N/P) capacity ratio of 1.0. By chemically etching Cu to create a sacrificial cuprous chloride (γ‐CuCl) interface, we obtained a micro‐textured Cu substrate with increased electrochemical surface area (ECSA). Upon initial electrochemical reduction, γ‐CuCl converts to metallic Cu while releasing Cl − ions into the local interfacial region of the electrolyte. Density functional theory calculations indicate that localized Cl − ions favorably regulate Zn 2+ adsorption energy while suppressing the hydrogen evolution reaction. Benefitting from the synergistic combination of enhanced ECSA and dynamic Cl − mediated interfacial engineering, Zn//Cu cells achieve stable plating/stripping cycling for 1654 h (69 days). Notably, Zn//MnO 2 full cells using 3D‐printed etched Cu substrate assembled under a nominal N/P ratio of 1.0 (determined by a reversible capacity at 10 mA cm −2 ) deliver a remarkable device volumetric capacity of 53.5 mAh cm −3 . Under high‐rate cycling (80 mA cm −2 ), the cell retains 70% of initial capacity over 500 cycles. This performance represents a benchmark for Zn reversibility under extreme material‐limited conditions.