Deciphering Anionic Chemistry in Aqueous Zinc-Based Batteries: From Spectators to Regulators

Aqueous zinc-based batteries (AZBs) have emerged as promising candidates for grid-scale energy storage systems due to the high volumetric capacity, intrinsic non-flammability, and cost-effectiveness. However, their practical application is limited by insufficient reversibility and sluggish reaction kinetics. In this regard, anionic chemistry plays a key role in regulating the thermodynamics and kinetics of electrode reactions. Nevertheless, most discussions in the chemistry of AZBs focus on Zn²⁺ behavior, and a comprehensive review of anionic chemistry is still lacking. In this review, we systematically summarize the key descriptors of commonly used anions, which affect the competitive coordination among anions, Zn²⁺, and H₂O. We then critically analyze the effect of anionic chemistry on zinc anode reactions, including the hydrogen evolution reaction and Zn-deposition process, elucidating structure-performance correlations between anionic properties and electrochemical behavior. Furthermore, we discuss the role of anions as charge carriers and their impact on the kinetics of cathode reactions. Finally, we conclude with a concise perspective of future research directions in anion design and mechanistic investigation. This review may provide guidance for the rational design of high-performance AZBs for practical applications.