Eutectic Electrolytes with Doubly-Bound Water for High-Stability Zinc Anodes

摘要

The aqueous zinc-ion battery has the advantages of environmental friendliness,safety, and reliability, which is expected to be used for large-scale energystorage. However, due to the high activity of water, the hydrogen evolutionreaction (HER) easily occurs on the surface of the zinc anode during thecharge–discharge process, which is accompanied by corrosion, by-products,and dendrite formation. Herein, a new-type eutectic electrolyte consistingof ZnCl_2, tetramethylurea (TMU), and H2O with the optimal molar ratio of1:3:1 (ZT-1) is developed for the high-stability zinc anodes. The H_2O in thissystem is doubly bound through the coordination with Zn~(2+) and the hydrogenbonding with TMU, thus leading to the greatly inhibited activity of H_2O. Inaddition, the H_2O and TMU are successively stripped during the desolvationprocess of ZnCl_2(TMU)(H_2O), followed by the deposition of ZnCl_2 at the zincinterface. In this way, the tendency of HER, corrosion, dendrites, and by-productsinduced by the decomposition of H_2O molecules at the zinc interface isminimized, enabling a much more stable plating/stripping process of Zn~(2+).Consequently, the Zn//Zn symmetric cell can stably cycle for >2000 h, whilethe Zn//Cu half cell can stably cycle 800 times with an average Coulombicefficiency of 99.5.