A weakly solvating electrolyte towards practical rechargeable aqueous zinc-ion batteries

Structure deterioration and side reaction, which originated from the solvated H 2 O, are the main constraints for the practical deployment of both cathode and anode in aqueous Zn-ion batteries. Here we formulate a weakly solvating electrolyte to reduce the solvating power of H 2 O and strengthen the coordination competitiveness of SO 4 2− to Zn 2+ over H 2 O. Experiment results and theoretical simulations demonstrate that the water-poor solvation structure of Zn 2+ is achieved, which can (i) substantially eliminate solvated-H 2 O-mediated undesirable side reactions on the Zn anode. (ii) boost the desolvation kinetics of Zn 2+ and suppress Zn dendrite growth as well as structure aberration of the cathode. Remarkably, the synergy of these two factors enables long-life full cells including Zn/NaV 3 O 8 ·1.5H 2 O, Zn/MnO 2 and Zn/CoFe(CN) 6 cells. More importantly, practical rechargeable AA-type Zn/NVO cells are assembled, which present a capacity of 101.7 mAh and stability of 96.1% capacity retention after 30 cycles at 0.66 C. The practical deployment of aqueous zinc-ion batteries is hindered by the structure deterioration and side reactions at electrodes. Here, the authors introduce a weakly solvating electrolyte with butanone as an electrolyte additive to stabilize both the cathode and anode of aqueous zinc-ion batteries simultaneously.