N,N-dimethylformamide tailors solvent effect to boost Zn anode reversibility in aqueous electrolyte

Rechargeable aqueous Zn batteries are considered as promising energy-storage devices because of their high capacity, environmental friendliness and low cost. However, the hydrogen evolution reaction and growth of dendritic Zn in common aqueous electrolytes severely restrict the application of Zn batteries. Here, we develop a simple strategy to suppress side reactions and boost the reversibility of the Zn electrode. By introducing 30% (volume fractions) N,N-dimethylformamide (DMF) to the 2 M Zn(CF₃SO₃)₂-H₂O electrolyte (ZHD30), the preferential hydrogen-bonding effect between DMF and H₂O effectively reduces the water activity and hinders deprotonation of the electrolyte. The ZHD30 electrolyte improves the Zn plating/stripping coulombic efficiency from ∼95.3% to ∼99.4% and enhances the cycles from 65 to 300. The Zn-polyaniline full battery employing the ZHD30 electrolyte can operate over a wide temperature range from -40°C to +25°C and deliver capacities of 161.6, 127.4 and 65.8 mAh g^-1 at 25, -20 and -40°C, respectively. This work provides insights into the role of tuning solvent effects in designing low-cost and effective aqueous electrolytes.