Suitable Stereoscopic Configuration of Electrolyte Additive Enabling Highly Reversible and High-Rate Zn Anodes

Electrolyte additive engineering is a crucial method for enhancing the performance of aqueous zinc-ion batteries (AZIBs). Recently, most research predominantly focuses on the role of functional groups in regulating electrolytes, often overlooking the impact of molecule stereoscopic configuration. Herein, two isomeric sugar alcohols, mannitol and sorbitol, are employed as electrolyte additives to investigate the impact of the stereoscopic configuration of additives on the ZnSO₄ electrolyte. Experimental analysis and theoretical calculations reveal that the primary factor for improving Zn anode performance is the regulation of the solvation sheath by these additives. Among the isomers, mannitol exhibits stronger binding energies with Zn²⁺ ions and water molecules due to its more suitable stereoscopic configuration. These enhanced bindings allow mannitol to coordinate with Zn²⁺, contributing to solvation structure formation and reducing the active H₂O molecules in the bulk electrolyte, resulting in suppressed parasitic reactions and inhibited dendritic growth. As a result, the zinc electrodes in mannitol-modified electrolyte exhibit excellent cycling stability of 1600 h at 1 mA cm^-2 and 900 h at 10 mA cm^-2, respectively. Hence, this study provides novel insights into the importance of suitable stereoscopic molecule configurations in the design of electrolyte additives for highly reversible and high-rate Zn anodes.