A Binary Hydrate‐Melt Electrolyte with Acetate‐Oriented Cross‐Linking Solvation Shells for Stable Zinc Anodes

Abstract Aqueous zinc‐ion batteries (ZIBs) with low cost and high safety are promising energy‐storage devices. However, ZIBs with metal Zn anodes usually suffer from low coulombic efficiency and poor cycling performance due to the occurrence of side reactions on the Zn anodes. Here, a binary hydrate‐melt ZnCl 2 /Zn(OAc) 2 electrolyte is designed to suppress the hydrogen evolution reaction and by‐product formation on Zn anodes by adjusting the Zn 2+ solvation structure. In the solvation structure of the hydrate‐melt ZnCl 2 /Zn(OAc) 2 electrolyte, the carboxylate group in OAc − will coordinate with the Zn 2+ , which will weaken the interaction between Zn 2+ and H 2 O molecules to achieve higher ionization energy of H 2 O molecules. Simultaneously, these carboxylate groups of OAc − can serve as H‐bond acceptors to construct H‐bonds with H 2 O molecules in their neighboring solvation structures, forming a cross‐linking H‐bond network. Such a cross‐linking H‐bond network further suppresses the water activity in ZnCl 2 /Zn(OAc) 2 electrolyte. As a result, in such an electrolyte, the side reactions are effectively restricted on Zn anodes and thus Zn anodes can achieve a high coulombic efficiency of 99.59% even after cycling. To illustrate the feasibility of the ZnCl 2 /Zn(OAc) 2 electrolyte in aqueous ZIBs, Zn||p‐chloranil cells are assembled based on the ZnCl 2 /Zn(OAc) 2 electrolyte. The resultant Zn||p‐chloranil cells exhibit enhanced cycling performance compared with the cases with a conventional ZnSO 4 electrolyte.