Fast Supercapacitors Based on Graphene-Bridged V2O3/VOx Core-Shell Nanostructure Electrodes with a Power Density of 1 MW kg-1

Transition metal oxides (TMOs), with their very large pseudocapacitance effect, hold promise for next generation high-energy-density electrochemical supercapacitors (ECs). However, the typical high resistivity of TMOs restricts the reported ECs to work at a low charge-discharge (C-D) rate of 0.1-1 V s(-1). Here, a novel vanadium oxides core/shell nanostructure-based electrode to overcome the resistivity challenge of TMOs for rapid pseudocapacitive EC design is reported. Quasi-metallic V2O3 nanocores are dispersed on graphene sheets for electrical connection of the whole structure, while a naturally formed amorphous VO2 and V2O5 (called as VOx here) thin shell around V2O3 nanocore acts as the active pseudocapacitive material. With such a graphene-bridged V2O3/VOx core-shell composite as electrode material, ECs with a C-D rate as high as 50 V s(-1) is demonstrated. This high rate was attributed to the largely enhanced conductivity of this unique structure and a possibly facile redox mechanism. Such an EC can provide 1000 kW kg(-1) power density at an energy density of 10 Wh kg(-1). At the critical 45 degrees phase angle, these ECs have a measured frequency of 114 Hz. All these indicate the graphene-bridged V2O3/VOx core-shell structure is promising for fast EC development.