Regulating Water Activity for Rechargeable Zinc-Ion Batteries: Progress and Perspective

Recent emerging rechargeable zinc-ion batteries have inherent benefits of intrinsic battery safety and high elemental abundance and reduce pollution toward an environmentally compatible energy storage system. However, the effort of promoting rechargeable aqueous Zn-ion batteries for large-scale energy storage applications is greatly plagued by the high activity of water molecules. The high activity of water molecules remains a threat to Zn-ion batteries, leading to premature failure of the Zn anode, cathode dissolution, and inferior low-temperature performance. Recently, a wide spectrum of effective strategies has been reported for reducing water's activity to tackle the above challenges. In view of the shallow understanding of water molecule states and their interwoven associations with Zn-ion battery performance, it becomes urgent to highlight the significance of regulating water activity and summarize recent progress in aqueous Zn-ion batteries. This Perspective aims to provide a fundamental understanding for designing better Zn-ion batteries using aqueous solution chemistry.