Improving Zn anode electrochemical reversibility via crystallographic plane regulation by polyethylene glycol electrolyte additive

Aqueous zinc-ion batteries (AZIBs) are considered promising candidates for scalable and sustainable energy storage devices due to their low cost and high safety advantages. However, the practical application of AZIBs is subject to the limits of the reversibility of the Zn²⁺ stripping/plating, such as the growth of Zn dendrites, corrosion of Zn anode, and hydrogen evolution reaction (HER). Herein, we propose a solution to the issues of AZIBs by creating a versatile electrolyte via the addition of polyethylene glycol (PEG). PEG additive changes the coordination environment of Zn²⁺ and disturbs the solvation structure of H₂O, which is beneficial to alleviate the side reactions triggered by water molecules in the Zn²⁺ solvation structure. In addition, the Zn²⁺ nucleation behavior is optimized by texturing the hexagonal deposition plane and inducing the compact-grained deposition manner to resist corrosion reactions and dendrite aggravation. The solvation structure of Zn²⁺ is optimized to improve the reversibility of the Zn anode. As a result, improved reversibility of Zn plating/stripping on the Cu-working electrode is achieved by 20% PEG electrolyte with high Coulombic efficiency (CE) of 99.43% at 1 mA cm⁻², stably cycled for 750 cycles. Furthermore, the Zn||Zn symmetrical half-cell with 20% PEG electrolyte shows stable plating/stripping overpotentials for more than 1400 h. Finally, the Zn||V₂O₅ full-cells exhibit excellent long cycling stability for over 180 cycles even at 1000 mA g⁻¹ with a high reversible capacity of 168 mAh g⁻¹. This work provides valuable insights into designing electrolytes for aqueous zinc metal batteries.