Polycation‐Regulated Electrolyte and Interfacial Electric Fields for Stable Zinc Metal Batteries

Zn metal as one of promising anode materials for aqueous batteries but suffers from disreputable dendrite growth, grievous hydrogen evolution and corrosion. Here, a polycation additive, polydiallyl dimethylammonium chloride (PDD), is introduced to achieve long‐term and highly reversible Zn plating/stripping. Specifically, the PDD can simultaneously regulate the electric fields of electrolyte and Zn/electrolyte interface to improve Zn 2+ migration behaviors and guide dominant Zn (002) deposition, which is veritably detected by Zeta potential, Kelvin probe force microscopy and scanning electrochemical microscopy. Moreover, PDD also creates a positive charge‐rich protective outer layer and a N‐rich hybrid inner layer, which accelerates the Zn 2+ desolvation during plating process and blocks the direct contact between water molecules and Zn anode. Thereby, the reversibility and long‐term stability of Zn anodes are substantially improved, as certified by a higher average coulombic efficiency of 99.7 % for Zn||Cu cells and 22 times longer life for Zn||Zn cells compared with that of PDD‐free electrolyte.