Engineering a Charge-Neutral Solvation Sheath for Stable Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries have attracted considerable attention due to their inherent safety, low cost, and environmental compatibility. However, Zn anodes suffer from undesired dendrite formation and hydrogen evolution reactions, which severely hinder their application prospects. High-concentration electrolytes have proven effective in mitigating these issues by stabilizing the electrolyte and improving Coulombic efficiency. Nevertheless, excessive salt content increases electrolyte viscosity, impedes ion transport, and raises costs, therefore compromising overall performance. In this study, a charge-neutral solvation sheath (CNSS) strategy is proposed to enhance the performance of zinc anode. The CNSS is the result of the evolving solvation structure of Zn²⁺ upon the introduction of anions, which can replace water molecules in the primary solvation sheath. This strategy effectively regulates the reactivity of solvated water molecules by mitigating their polarization. Consequently, the CNSS structure can effectively suppress water decomposition and by-product formation. This structural feature significantly enhances the cycling stability of zinc anode under moderately concentrated conditions. Moreover, Zn||I₂ batteries utilizing this optimized electrolyte exhibit exceptional long-term durability, maintaining stable performance over 5000 cycles at a high rate of 10 C. This work offers new insights into the design of cost-effective and high-performance electrolytes for large-scale energy storage applications.