Boosting Zn Anode Utilization by Trace Iodine Ions in Organic‐Water Hybrid Electrolytes through Formation of Anion‐rich Adsorbing Layers

Abstract

AbstractAqueous Zn batteries are attracting extensive attentions, but their application is still hindered by H2O‐induced Zn‐corrosion and hydrogen evolution reactions. Addition of organic solvents into aqueous electrolytes to limit the H2O activity is a promising solution, but at the cost of greatly reduced Zn anode kinetics. Here we propose a simple strategy for this challenge by adding 50 mM iodine ions into an organic‐water (1,2‐dimethoxyethane (DME)+water) hybrid electrolyte, which enables the electrolyte simultaneously owns the advantages of low H2O activity and accelerated Zn kinetics. We demonstrate that the DME breaks the H2O hydrogen‐bond network and exclude H2O from Zn2+ solvation shell. And the I− is firmly adsorbed on the Zn anode, reducing the Zn2+ de‐solvation barrier from 74.33 kJ mol−1 to 32.26 kJ mol−1 and inducing homogeneous nucleation behavior. With such electrolyte, the Zn//Zn symmetric cell exhibits a record high cycling lifetime (14.5 months) and achieves high Zn anode utilization (75.5 %). In particular, the Zn//VS2@SS full cell with the optimized electrolyte stably cycles for 170 cycles at a low N : P ratio (3.64). Even with the cathode mass‐loading of 16.7 mg cm−2, the full cell maintains the areal capacity of 0.96 mAh cm−2 after 1600 cycles.