Synergetic modulation on ionic association and solvation structure by electron-withdrawing effect for aqueous zinc-ion batteries

Aqueous zinc-ion batteries are emerging as one of the most promising large-scale energy storage systems due to their low cost and high safety. However, Zn anodes often encounter the problems of Zn dendrite growth, hydrogen evolution reaction, and formation of by-products. Herein, we developed the low ionic association electrolytes (LIAEs) by introducing 2, 2, 2-trifluoroethanol (TFE) into 30 m ZnCl₂ electrolyte. Owing to the electron-withdrawing effect of -CF₃ groups in TFE molecules, in LIAEs, the Zn²⁺ solvation structures convert from larger aggregate clusters into smaller parts and TFE will construct H-bonds with H₂O in Zn²⁺ solvation structure simultaneously. Consequently, ionic migration kinetics are significantly enhanced and the ionization of solvated H₂O is effectively suppressed in LIAEs. As a result, Zn anodes in LIAE display a fast plating/stripping kinetics and high Coulombic efficiency of 99.74%. The corresponding full batteries exhibit an improved comprehensive performance such as high-rate capability and long cycling life.