One-step strategy to three-dimensional graphene/VO2 nanobelt composite hydrogels for high performance supercapacitors

A facile one-step strategy has been developed to prepare 3D graphene/VO2 nanobelt composite hydrogels, which can be readily scaled-up for mass production by using commercial V2O5 and graphene oxide as precursors. During the formation of the graphene/VO2 architecture, 1D VO2 nanobelts and 2D flexible graphene sheets are self-assembled to form interconnected porous microstructures through hydrogen bonding, which facilitates charge and ion transport in the electrode. Due to the hierarchical network framework and the pseudocapacitance contribution from VO2 nanobelts, the hybrid electrode demonstrates excellent capacitive performances. In the two-electrode configuration, the graphene/VO2 nanobelt composite hydrogel exhibits a specific capacitance of 426 F g(-1) at 1 A g(-1) in the potential range of -0.6 to 0.6 V, which greatly surpasses that of each individual counterpart (191 F g(-1) and 243 F g(-1) at 1 A g(-1) for VO2 nanobelt and graphene hydrogel, respectively). The hybrid electrode also shows an improved rate capability and cycling stability, which is indicative of a positive synergistic effect of VO2 and graphene on the improvement of electrochemical performance. These findings reveal the importance and great potential of graphene composite hydrogels in the development of energy storage devices with high power and energy densities.