Strong Metal‐Support Interaction to Invert Hydrogen Evolution Overpotential of Cu Coating for High‐Coulombic‐Efficiency Stable Zn Anode in Aqueous Zn‐Ion Batteries

Cu exhibits strong zincophilic properties but suffers from a much lower hydrogen evolution reaction (HER) overpotential compared to Zn, which significantly undermines the coulombic efficiency and stability of the Zn anode. Consequently, Cu is regarded as an unsuitable coating for Zn anode protection. In this work, the HER overpotential of Cu versus Zn is inverted through strong metal-support interaction (SMSI) to modify the electronic structure of Cu. This interaction facilitates electron transfer, enriching positive charge and slowing down the adsorption kinetics of H⁺ on the Cu surface. As a result, at very low current densities of 0.2 and 2 mA cm⁻², the Cu-coated-Zn||Cu cell achieves exceptionally high coulombic efficiencies of 99.11% and 99.91% over 2500 and 1600 h of cycling (100% depth of discharge (DOD)), which remarkably surpasses the performance of Zn anode protective coatings all reported. Moreover, a 1 Ah soft-packed full battery is not bulged and retains 94.7% of its initial capacity after 150 cycles. This study overturns the conventional concept by leveraging SMSI to tune the electronic structure, reverses the HER overpotential, and expands the range of viable metals for anode protection in aqueous metal batteries.