Suppressing vanadium dissolution by modulating aqueous electrolyte structure for ultralong lifespan zinc ion batteries at low current density

Vanadium-based cathodes tending to dissolution in mildly acidic aqueous zinc ion electrolytes result in serious capacity fading at a low current density. Herein, we proposed a novel aqueous electrolyte to suppress vanadium dissolution by regulating solvation structure of Zn2+ and thereby significantly boost cycling lifespan. With this optimized electrolyte system, the decrease of number and activity of free water molecules significantly reduces vanadium solubility in water, leading to stable electrolyte/cathode interfaces. Importantly, the optimization of the electrolyte solvation structure could block the electrochemically activated desolvation water molecules to attack cathode interfaces and minimize the number of co-intercalated water molecules accumulated in tunnel, which is propitious to inhibit crystalline-to-amorphous transformation and maintain the integrity of vanadium oxide host lattice. As a result, the VO2 cathode exhibits impressive cycling stability with a capacity retention of 98.2% over 400 cycles at a low current density of 0.1 A g−1. This study provides an inspiring strategy of inhibiting vanadium dissolution to realize the ultralong lifespan at a low current density for Vanadium-based cathode in aqueous ZIBs.