Green Environmentally Friendly "Zn(CH₃SO₃)₂" Electrolyte for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries are considered as an ideal substitute for lithium-ion batteries due to their abundant resource storage, high safety, and low price. However, zinc anodes exhibit poor reversibility and cyclic stability in most conventional aqueous electrolytes. Herein, an environmentally friendly Zn(CH₃SO₃)₂ electrolyte is proposed to solve the problems of common aqueous electrolytes. The bulky CH₃SO₃^- anions can regulate the solvation structure of Zn²⁺ by replacing some water molecules in the primary solvation sheath of Zn²⁺, thus slowing the hydrogen evolution side reactions and formation of zinc dendrite. Additionally, the changing solvation structure weakens the bonding between Zn²⁺ and the surrounding water molecules, which is conducive to the transport and charge transfer of Zn²⁺, thus improving the battery capacity. In the Zn(CH₃SO₃)₂ electrolyte, Zn plating/stripping exhibits a high Coulombic efficiency of >98% and long-term cyclic stability over 800 h. The specific capacity of the assembled Zn//V₂O₅ cell in 3 mol L^-1 Zn(CH₃SO₃)₂ reaches 350 mA h g^-1 at 0.1 A g^-1, much higher than that in the ZnSO₄ electrolyte (213 mA h g^-1). In conclusion, this work offers insights into the exploration of advanced green electrolyte systems for zinc-ion batteries.