Vanadium dioxide (IV) (B) nanostructures prepared via electrodeposition for zinc-ion storage in electrochemical energy storage devices

Electrode materials for aqueous zinc ion storage are essential in the development of next-generation energy storage devices. Crystalline VO2 (B) nanostructures are grown on the carbon cloth (CC) substrate using a galvanostatic electrodeposition method followed by thermal annealing. When used as the electrode material, the specific capacity reaches 223.6 mAh g- 1 at 1 A g- 1 in 2 M ZnSO4 in the three-electrode test. The electrode exhibits battery-type charge storage behavior. This high specific capacity is originated from the combination of high number of electrochemically active sites and from the facile ion diffusion achieved by the homogeneous coverage of VO2(B) nanostructures at the CC surface. The charge storage mechanism is investigated using ex-situ X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, and both H+ and Zn2+ participate in the charge storage. Also, the VO2(B) phase is irreversibly transformed to V2O5 during chargedischarge cycling. An electrochemical energy storage device is assembled with VO2/CC and zinc foil as electrodes and with 2 M ZnSO4 aqueous solution as electrolyte. The device can deliver an energy density of 70 Wh kg- 1 at a power density of 351 W kg- 1, and retains 78 % of its initial capacity after 2000 cycles at 10 A g- 1.