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

Structure deterioration and side reaction, which originated from the solvated H₂O, 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 H₂O and strengthen the coordination competitiveness of SO₄^2- to Zn²⁺ over H₂O. Experiment results and theoretical simulations demonstrate that the water-poor solvation structure of Zn²⁺ is achieved, which can (i) substantially eliminate solvated-H₂O-mediated undesirable side reactions on the Zn anode. (ii) boost the desolvation kinetics of Zn²⁺ 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/NaV₃O₈·1.5H₂O, Zn/MnO₂ 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.