Concentrated weak hydrated electrolytes towards ultra-stable high-voltage zinc ion batteries

Hydrogen evolution reactions (HER), dendritic growth, narrow electrochemical windows, and dissolution of cathode materials severely limit the development of aqueous zinc metal batteries. Herein, the unique bisphenylsulfonamide anion (BBI−) is employed to reduce the ion-dipole interaction between Zn2+ and H2O by complexing Zn2+ to suppress H2O decomposition. Meanwhile, the solvent sheath structure of Zn2+-BBI− coordination can provide a large nucleation overpotential, thus producing uniform deposition to suppress dendrites. The hydrogen bonds between BBI− and H2O effectively limit the diffusion of H2O, thereby reducing the dissolution of the water-soluble cathode material into the electrolyte. Both experimental and simulated results are carried out and quantitively confirm the ion paring, hydrogen bond and solvent effect evolution of Zn(BBI)2 electrolytes. This concentrated electrolyte enables Zn||Zn symmetric cells to achieve a superlong cycling life of over 7100 h even at a current of 2 mA cm−2 and capacity of 2 mAh cm−2, while the high mass loading Zn||NaV3O8·1·5H2O and Zn||Zn3(Fe(CN)6)2 cells also exhibit excellent cycling performance at a cut-off voltage of 2.1 V. The findings of this work point to a very promising strategy for the development of long-life aqueous batteries.