Halogenated solvation structure and preferred Zn (002) deposition via trace additive towards high reversibility for aqueous zinc-ion batteries

Abstract

Tremendous progress has been achieved in cathode materials for aqueous zinc-ion batteries (AZIBs), however their practical applications are hindered by the poor cycling stability of Zn anode. Herein, amphiphilic choline bromine (ChBr) is introduced as additive into highly-concentrated ZnSO₄ aqueous electrolyte, which not only regulates the traditional Zn²⁺ solvation structure but also establishes an electrostatic shielding layer at electrolyte-anode interface. Compared to the pristine 3 M ZnSO₄ electrolyte, ChBr-modified ZnSO₄ electrolyte (ZSO-ChBr) is proven effective in promoting the reversibility of zinc plating/stripping and the preferred growth of Zn (002) plane, as well as suppressing the hydrogen evolution and side reactions on Zn anode surface. As a result, Zn||Zn symmetric cell in optimal ZSO-ChBr electrolyte could harvest a remarkable lifespan over 6000 h at 5 mA cm⁻² and 1 mAh cm⁻², besides a highly-reversible zinc plating/stripping process over 1500 cycles was achieved in Zn||Cu asymmetric cell. Moreover, the Zn||MnO₂ full cell could exhibit an excellent rate capability and the cycling stability with a capacity retention of 80 % after 400 cycles. This work provides an integrated strategy of electrolyte engineering to elevate the desolvation kinetics of Zn²⁺ at anode-electrolyte interface and enhance the cycling stability of Zn anode, effectively improving the electrochemical performances of aqueous zinc-ion batteries (AZIBs) and promoting the development of various energy storage systems.