Fast Supercapacitors Based on Graphene‐Bridged V₂O₃/VO<i>_x</i> Core–Shell Nanostructure Electrodes with a Power Density of 1 MW kg⁻¹

Abstract

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 V 2 O 3 nanocores are dispersed on graphene sheets for electrical connection of the whole structure, while a naturally formed amorphous VO 2 and V 2 O 5 (called as VO x here) thin shell around V 2 O 3 nanocore acts as the active pseudocapacitive material. With such a graphene‐bridged V 2 O 3 /VO x 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° phase angle, these ECs have a measured frequency of 114 Hz. All these indicate the graphene‐bridged V 2 O 3 /VO x core–shell structure is promising for fast EC development.