VO 2 nanoarrays are grown on graphene foam and the surface is coated with HMB for performance enhancement as LIB and supercapacitor electrodes.
Hydrogen molybdenum bronze (HMB) is electrochemically deposited as a homogeneous shell on VO 2 nanoflakes grown on graphene foam (GF), forming a GF + VO 2/HMB integrated electrode structure. Asymmetric supercapacitors based on the GF + VO 2/HMB cathode and neutral electrolyte are assembled and show enhanced performance with weaker polarization, higher specific capacitance and better cycling life than the unmodified GF + VO 2 electrode. Capacitances of 485 F g −1 (2 A g −1) and 306 F g −1 (32 A g −1) are obtained because of the exceptional 3D porous architecture and conductive network. In addition, the GF + VO 2/HMB electrodes are also characterized as the cathode of lithium ion batteries. Very stable capacities at rates up to 30 C are demonstrated for 500 cycles. This new type of shell material is expected to have its generic function in other metal oxide based nanostructures.