Trifluoroacetamide-mediated electrolyte solvation structure reconstruction for highly reversible Zn plating/stripping in aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have emerged as promising candidates for next generation energy storage systems, benefiting from their high intrinsic safety, cost-effectiveness, and environmental benignity. However, practical applications of AZIBs are severely hindered by critical issues of poor reversibility, dendrite growth, interfacial corrosion, and the hydrogen evolution reaction (HER). Herein, trifluoroacetamide (TFA) is proposed to optimize the Zn²⁺ solvation configuration and stabilize the anode interface to suppress dendrite growth. In contrast to prior strategies relying on a single fluorine source (BF₄⁻or inert anions), this work uses BF₄⁻ and the -CF 3 group of TFA as dual fluorine sources for synergistic organic/inorganic interfacial regulation. ATR-FTIR, Raman, and NMR spectra show that TFA effectively modulates the Zn 2+ solvation structure, and XPS depth profiling confirms the formation of a dense hybrid SEI consisting of inorganic ZnF 2 (from BF₄⁻) and organic fluorides (from -CF 3 ). Comprehensive electrochemical and physical characterizations reveal that the 1 M Zn(BF₄)₂-5% TFA exhibits a minimum contact angle of 45°, which remarkably enhances the wettability Zn/electrolyte interface, enables uniform Zn deposition, and promotes stable three-dimensional diffusion kinetics. The Zn||Zn symmetric cell assembled with the same electrolyte delivers excellent long-cycle stability (≈ 360 h at 1 mA cm⁻² and 0.5 mAh cm⁻²) and high critical current density (12 mA cm⁻²). This work elucidates the pivotal role of TFA in modulating interfacial ion transport and Zn deposition behavior, furnishing a viable strategy for the construction of highly reversible zinc-based batteries.