Retarding Deposition and Hydrogen Evolution Reaction Enables Stable and Reversible Zn Metal Anode

The hydrogen evolution reaction and heterogeneous deposition may cause inferior reversibility and stability of the Zn anode for neutral aqueous Zn-metal batteries. Notably, slow reaction kinetics plays a pivotal role in mitigating the Zn2+ concentration gradient and facilitating an elevation in the overpotential for hydrogen evolution. Here, a straightforward electrolyte tactic is implemented to create a predeposition layer characterized by a weak adsorption capability, coupled with an electric double layer featuring a relatively positive charge distribution. This configuration impedes the Volmer reaction and decelerates the deposition reaction kinetics, ultimately mitigating the hydrogen evolution reaction and ensuring a smooth deposition process. Benefiting from the uniform deposition and less hydrogen generation on the Zn anode, replacing 5% Zn2+ with Cd2+ renders a high average Coulombic efficiency in a Zn||Cu battery, a stable cycle in a Zn||Zn battery, and a high-capacity retention in a Zn||MnO2 pouch cell.