Homogenized Current Collector Surface for High Reversibility Anode‐Free Zinc Metal Batteries

Abstract The advancement of anode‐free batteries (AFBs) presents a promising approach to enhance the energy density of secondary batteries. Nonetheless, a prevalent challenge associated with AFBs is the low Coulombic efficiency (CE), which arises from the surface inhomogeneity of the current collector. Conventional strategies load a variety of metalophile materials on its surface to enhance CE. However, without the solution of the intrinsic inhomogeneity of the current collector, the modification cannot be absolutely uniform, resulting in defect generation and even interface failures. Herein, anode‐free zinc metal batteries employing copper foil as a representative are used to eliminate the inhomogeneity of the oxide layer on the commercial copper foil surface while simultaneously adhering a homogenized thin chlorine (Cl) atomic layer with 100% conformal coverage (modified‐Cu) by a one‐step method. The homogenized Cl atomic layer exhibits a 3D diffusion for Zn atoms and induces dense growth of Zn (100) crystal plane, promoting reversible Zn plating/stripping. Additionally, the modified‐Cu||Zn x MnO 2 anode‐free full battery exhibits superior cycling stability (500 cycles with 80% capacity retention). In addition to this, meter‐level modified‐Cu is produced in large quantities through a roll‐to‐roll system. This innovative strategy for constructing homogenized surfaces can promote the development of high‐energy‐density anode‐free metal batteries toward practical applications.