Tuning the Electrolyte Solvation Structure to Suppress Cathode Dissolution,Water Reactivity,and Zn Dendrite Growth in Zinc-Ion Batteries

The cycle life of aqueous zinc-ion batteries (ZIBs) is limited by the notable challenges of cathode dissolution, water reactivity, and zinc dendrites. Here, it is demonstrated that by tuning the electrolyte solvation structure, the issues for both the electrodes and the electrolyte can be addressed simultaneously. Specifically, a fire-retardant triethyl phosphate (TEP) is demonstrated as a cosolvent with strong solvating ability in a nonaqueous/aqueous hybrid electrolyte. The TEP features a higher donor number (26 kcal mol⁻¹) than H₂O (18 kcal mol⁻¹), preferring to form a TEP occupied inner solvation sheath around Zn²⁺ and strong hydrogen bonding with H₂O. The TEP coordinated electrolyte structure can inhibit the reactivity of H₂O with V₂O₅ and leads to a robust polymeric-inorganic interphase (poly-ZnP₂O₆ and ZnF₂) on zinc anode effectively preventing the dendrite growth and parasitic water reaction. With such an optimized electrolyte, the Zn/Cu cells perform high average Coulombic efficiency of 99.5%, and the full cell with a low capacity ratio of Zn:V₂O₅ (2:1) and lean electrolyte (11.5 g Ah⁻¹) delivers a reversible capacity of 250 mAh g⁻¹ for over 1000 cycles at 5 A g⁻¹. This study highlights the promise of a successful electrolyte regulation strategy for the development of high-performance and practical ZIBs.