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 encoun-ter 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+ sol-vation 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.