Solvation structure tuning for advanced aqueous zinc-ion batteries

Abstract

Aqueous zinc-ion batteries (ZIBs) have garnered significant interest as a potential solution for large-scale energy storage applications, thanks to their low cost and high safety. However, due to the strong solvation effect with water of Zn2+ and decomposition of active water molecules in the Zn2+ solvation structures, the aqueous ZIBs encounter some issues, such as sluggish Zn2+ transport kinetics, slow de-solvation kinetics, cathode materials collapse and dissolution, hydrogen evolution reaction, Zn dendrite growth, byproduct accumulation, and a narrow electrochemical working potential window. Several strategies for tuning the Zn2+ solvation structure in electrolytes have effectively addressed the above issues. However, a comprehensive review of these solvation structure tuning strategies is currently lacking. In this review, the issues induced by the strong solvation effect with water of Zn2+ and the decomposition of active water molecules in the Zn2+ solvation structures are first present. Subsequently, the solvation structure tuning strategies are summarized, mainly including electrolyte engineering (salts, high concentration electrolyte, eutectic electrolyte, electrolyte additives, etc.) and anode surface modification. More importantly, the mechanism of solvation structure tuning is discussed in detail. Finally, further development directions and perspectives regarding solvation structure tuning are proposed.