Research Progress on Solvation Sheath Regulation Additives in ZnSO4 Electrolytes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are promising for scalable energy storage, yet their practical viability is constrained by zinc dendrite propagation, parasitic hydrogen evolution, and interfacial corrosion. Formulating electrolyte additives represents an economically viable strategy to address these long-standing bottlenecks by modulating the bulk solution and double-layer environments. Diverging from traditional composition-based classifications, this review categorizes recent additive strategies according to their underlying physical chemistry mechanisms. Specifically, we evaluate how these additives regulate the primary and secondary Zn2+ solvation sheaths, reconstruct the electric double layer (EDL) for crystallographic facet control, induce sacrificial or mineralized solid electrolyte interphases (SEIs), and establish responsive polymer confinement networks. Furthermore, we critically discuss the operational limitations, trade-offs, and parameter dependencies of these strategies under non-ideal, realistic conditions. Finally, prospective directions are outlined—focusing on descriptor-driven design, operando non-equilibrium characterizations, and performance validation under standard industrial metrics (e.g., low E/C ratios and high depths of discharge)—to provide an objective framework for advancing electrolyte optimization in practical zinc-based energy storage.