Kinetics Compensation Mechanism in Cosolvent Electrolyte Strategy for Aqueous Zinc Batteries

Abstract

Aqueous zinc batteries are the ideal choices to realize intrinsically safe energy storage, but parasitic side reactions make it difficult to achieve in practice. Although the cosolvent electrolyte effectively inhibits zinc dendrites and mitigates unexpected side reactions, it brings inevitable kinetics losses. Here, we systematically investigate and compare the interactions between Zn²⁺ and various oxygen-coordinated cosolvents under pure aqueous environments and the interactions between Zn²⁺ and OTf^– under mixed solvent environments containing different oxygen-coordinated cosolvents. And the differences in the effect of different oxygen-coordinated cosolvents on the solvation structure of Zn²⁺ and the kinetics of ion migration are quantitatively analyzed and summarized. On this basis, we propose a new kinetics compensation mechanism in cosolvent electrolyte strategy that can compensate the kinetics losses due to the introduction of cosolvents by weakening the anion–cation pair interaction and increasing the Zn²⁺ transfer number. Theory and experiments both demonstrate that this strategy can achieve kinetics compensation of aqueous zinc batteries while improving the electrochemical performance. This work provides a comprehensive and deep understanding of designing cosolvent electrolytes with superior electrochemical performance. More importantly, the proposed strategy can be applied to other cosolvents with similar properties and other aqueous battery systems.