Adjusting the Coordination and Deposition Environment of Zinc Ions to Stabilize the Zn Anode

Abstract

An economical and eco-friendly food sweetener erythritol with abundant hydroxyl groups and suitable site resistance has been added to ZnSO₄ electrolytes in aqueous Zn ion batteries (AZIBs). Density functional theory (DFT) calculations demonstrate that the O atoms in erythritol molecules can supply electrons to Zn²⁺, thus mitigating an electron transfer from H₂O to Zn²⁺, resulting in erythritol entering the solvation structure of Zn[(H₂O)₆]²⁺ and replacing some water molecules. Spectroscopic analysis confirms the altered solvation structure of Zn²⁺ and the reconstructed hydrogen-bonding network of the ZnSO₄ and erythritol electrolytes. With an equilibrium between “network water” and “free water” induced by erythritol additives, the possibility of active water decomposition is degraded, which further inhibits water-splitting and corrosion side reactions. In addition, theoretical studies and experimental characterizations verify that erythritol additives preferentially adsorb on the surface of Zn anodes, thus effectively protecting Zn anodes and inhibiting the mad growth of dendrites. As a result, the cells with ZnSO₄ + erythritol electrolytes demonstrated significantly higher Coulombic efficiency values and longer lifetimes than those of pure ZnSO₄ electrolytes. This study could advance the research process of small-molecule polyol additives for AZIBs.