Fig. 7. (a) CV curves of the as-fabricated HSCs measured at different sweep rates from 0 to 1.6 V. (b) Galvanostatic discharge curves collected at different current densities. (c) Specific capacitance calculated from discharge curves as a function of the current density. (d) Cycling performance at a constant current density of 10 A g⁻¹. (e) Ragone plots of our HSCs in comparison with previously reported HSCs based on vanadium-based electrode materials with aqueous electrolyte (blue plots,⁴⁴ black plots,¹⁶), inset image is the corresponding specific capacitance of these HSCs calculated from discharge curves at current density of 1 A g⁻¹. (f) Schematic of intimate between the VN or V₂O₅ nanospheres and graphene facilitating rapid charge and electrolyte transport.