Fig. 3

Electrochemical characterizations of VMSs/CNWs/Ni foam electrode and corresponding VMS-active carbon asymmetric capacitor. a Cycle voltammetry curves with different scan speeds (vs. SCE). b Galvanostatic charge/discharge curves at different current densities, the highest specific capacitance reached 1962 F g⁻¹ at a current density of 1 A g⁻¹ (vs. SCE). c Specific capacitances at different current densities of Ni MOF powders and VMS (vs. SCE). d Cycle voltammetry curves of activated carbon (black) and VMSs/CNWs/Ni foam (red) electrodes at 10 mV s⁻¹ (vs. SCE). e Cycle voltammetry curves of the asymmetric capacitor collected at different scan speed (vs. SCE). f The cyclability of the capacitor, it can hold 97% of its initial capacitance after 1200 cycles. The inset is galvanostatic charge/discharge curve at 0.5 A g⁻¹ (vs. SCE)