Mixture electrolyte suppressing water-induced parasitic reactions on Zn anode by tuning multilayer solvating structure

Abstract

Though aqueous zinc ion batteries have been identified as a feasible option for energy storage, there are still some challenges that block the development of aqueous zinc ion battery, especially the issues from zinc metal anode. Tuning solvating structure of Zn2+ and adjusting the electrolyte in recent years is considered to be a simple but potential strategy to improve stability of zinc anode. In this work, a mixture electrolyte was obtained by dessolving LiTFSI/TEGDME Li-O2 battery electrolyte into 2 M aqueous ZnSO4 solution to tune solvating structure and adjust the striping/plating process of anode. Molecular spectrum and X-ray based method clarified that the mixture electrolyte plays dual functions to protect anode during electrochemical process. From one aspect, TEGDME partially replaced water and reconstructed a new multilayer solvating shell with TFSI-, which is beneficial for fast dendrite-free deposition. From the other aspect, surface spectrum also revealed that due to the participation of Li+ and TFSI-, a surface layer with ZnOHS framework and ZnF2 fillings formed on anode which further inhibit the dendrite growth and stabilize anode. This work combines the method of tuning solvation structure and construct SEI together and opens a new view designing new electrolytes for aqueous Zn-ion battery.