Solvation Sheath Regulation to Induce Sulfide Solid–Electrolyte Interphase on Zn Metal Anode

Abstract

Zn metal anode experiences dendritic growth and side reactions in aqueous Zn batteries. ZnS with relatively high ionic conductivity is a suitable solid−electrolyte interphase (SEI) component, and an organic coverage would provide further protection for the underlying Zn. Herein, we reveal that SO 4 2− anions solvating with Zn 2+ are more prone to reduction than the nonsolvating ones and thus capable of ZnS generation. Nevertheless, in the conventional ZnSO 4 electrolyte, their solvation with Zn 2+ is limited by the shielding effect and steric hindrance from solvating water. Accordingly, erythritol (ET) additive with strong H-bonding and chelation abilities is introduced, which weakens water coordination and regulates solvation geometry. The enhanced solvating SO 4 2− together with chelating ET generates the target SEI. As a result, the Zn//Zn symmetric cell reaches a 960 h cycle life at 8.9 mA cm −2 and 8.9 mAh cm −2 . The ET additive further enables the stable cycling of full cells by suppressing cathode dissolution.