Boosting Zn anode reversibility via electrolyte solvation structure mediation by ethylene glycol monomethyl ether additive

Aqueous zinc-ion batteries are considered promising energy storage devices due to their low cost, high capacity, and high safety. However, the application of aqueous zinc-ion batteries is subject to the limits of Zn anode reversibility, such as the formation of Zn dendrites, Zn anode corrosion, and hydrogen evolution reaction. In this study, we reported an electrolyte additive ethylene glycol monomethyl ether (MOE) with a modulated electrolyte solvation structure, which can suppress the growth of Zn dendrites and enhance the reversibility of Zn chemistry. The MOE molecular shows a higher electron cloud density of oxygen atoms, which enhances the strength of H–O covalent bonds. Therefore, MOE can break the interaction between H₂O and H₂O and the interaction between H₂O and Zn²⁺. The solvation structure of Zn²⁺ is optimized to improve the reversibility of the Zn anode. As a consequence, the reversibility of Zn plating/stripping is promoted by 20% MOE-modified electrolyte with high CE of 99.4% at the current density of 1 mA cm⁻², stably cycled for 2100 cycles. The Zn||Zn symmetrical cells can keep dendrite-free cycling for more than 4000 h in the same target electrolyte. In addition, the Zn||V₂O₅ cell can exhibit excellent long cycling stability for over 1000 cycles even at 5 A g⁻¹ with the reversible capacity of 100 mAh g⁻¹. This work provides a universal additive strategy to design versatile electrolytes for aqueous zinc-ion batteries.