Rechargeable Aqueous Zn–V 2 O 5 Battery with High Energy Density and Long Cycle Life

We report an aqueous Zn–V 2 O 5 battery chemistry employing commercial V 2 O 5 cathode, Zn anode, and 3 M Zn(CF 3 SO 3 ) 2 electrolyte. We elucidate the Zn-storage mechanism in the V 2 O 5 cathode to be that hydrated Zn 2+ can reversibly (de)intercalate through the layered structure. The function of the co-intercalated H 2 O is revealed to be shielding the electrostatic interactions between Zn 2+ and the host framework, accounting for the enhanced kinetics. In addition, the pristine bulk V 2 O 5 gradually evolves into porous nanosheets upon cycling, providing more active sites for Zn 2+ storage and thus rendering an initial capacity increase. As a consequence, a reversible capacity of 470 mAh g –1 at 0.2 A g –1 and a long-term cyclability with 91.1% capacity rentention over 4000 cycles at 5 A g –1 are achieved. The combination of the good battery performance, safety, scalable materials synthesis, and facile cell assembly indicates this aqueous Zn–V 2 O 5 system is promising for stationary grid storage applications.