Green Environmentally Friendly "Zn(CH 3 SO 3 ) 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(CH 3 SO 3 ) 2 electrolyte is proposed to solve the problems of common aqueous electrolytes. The bulky CH 3 SO 3 - anions can regulate the solvation structure of Zn 2+ by replacing some water molecules in the primary solvation sheath of Zn 2+ , thus slowing the hydrogen evolution side reactions and formation of zinc dendrite. Additionally, the changing solvation structure weakens the bonding between Zn 2+ and the surrounding water molecules, which is conducive to the transport and charge transfer of Zn 2+ , thus improving the battery capacity. In the Zn(CH 3 SO 3 ) 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//V 2 O 5 cell in 3 mol L -1 Zn(CH 3 SO 3 ) 2 reaches 350 mA h g -1 at 0.1 A g -1 , much higher than that in the ZnSO 4 electrolyte (213 mA h g -1 ). In conclusion, this work offers insights into the exploration of advanced green electrolyte systems for zinc-ion batteries.