Tailoring defective vanadium pentoxide/reduced graphene oxide electrodes for all-vanadium-oxide asymmetric supercapacitors

Vanadium pentoxide is a highly promising cathode material for supercapacitors with neutral aqueous electrolytes. However, the insufficient understanding of energy storage mechanisms involved in the cathode material and the lack of suitable anode materials impede the development of the neutral aqueous-based supercapacitor. Herein, we report a strategy based on defect chemistry to tailor V2O5/reduced graphene oxide hybrid electrodes for assembling all-vanadium-oxide asymmetric supercapacitors. The V2O5 component in the hybrid consists of oxygen-deficient bilayer V2O5 nanobelts obtained by controlled hydrothermal synthesis, which can be mixed with a graphene oxide dispersion and assembled into V2O5/reduced graphene oxide through vacuum filtration followed by annealing. The V2O5/reduced graphene oxide electrodes are easily converted into suitable positive and negative electrodes through electrochemical formation, and along with conventional cation intercalation/ deintercalation reactions, a series of oxygen-vacancy-involving reactions render the electrodes typical pseudocapacitive behavior. The formed positive and negative electrodes exhibit excellent performance with specific capacitances of 468.5F g-1 and 406.8F g-1 at 1 A g-1, respectively. The all-vanadium-oxide asymmetric supercapacitor assembled with the formed positive and negative electrodes displays a high energy density and good cycling stability over the potential window of 0-1.7 V, demonstrating its great potential for low-cost, largescale, and safety-sensitive applications.