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. The Zn(Otf)2‐TEP‐H2O electrolyte has a significant effect on reducing the water activity and inhibiting the V‐dissolution, which helps the V2O5 material to support a reversible reaction mechanism during discharging/charging processes. This electrolyte is also found to protect zinc metal from serious depletion by generating a novel polymeric‐inorganic solid‐electrolyte interphase, which could block electron transport and enable fast Zn2+ diffusion.