Facile hydrothermal synthesis of monoclinic VO2/graphene nanowhisker composite for enhanced performance electrode material for energy storage applications

Abstract

Vanadium dioxide/reduced graphene oxide (VO2/G) nanowhisker composites are synthesized under hydrothermal conditions by a simple method. VO2 nanowhisker and 2D flexible graphene sheets are formed during the formation of VO2/G architecture to build interconnected porous microstructure via hydrogen bonding which allows charging and ion transport in the electrode. The composite electrode shows outstanding electrochemical performances due to the hierarchical network structure and pseudo-capacity contribution from VO2 nanowhiskers. The composite electrode used for electrochemical investigations in the aqueous electrolyte solution of 1 M Na2SO4. Noteworthy is the galvanostatic charge-discharge test which shows that, with a current density of 1 Ag−1, the specific capacitance value of the composite attained a high value of 294.5 Fg−1, which is significantly better than pure vanadium dioxide (VO2), and retains its capacitance at 203 Fg−1 at 10 Ag−1. The specific capacitance remained 96.3 % after 5000 continuous discharge cycles at 0.6 Ag−1 and shows an excellent cycle life for the material. It has also a high power density with a reasonably high-energy density. (i.e) energy density reached 48.07 Wh kg−1 at a power density of 213.6 Wkg−1. The results of the composite electrode were due to synergistic effects of VO2 and graphene, and excellent VO2 redox activity coupled with high electronic graphene sheet conductivity.