Three-dimensional porous V2O5 hierarchical spheres as a battery-type electrode for a hybrid supercapacitor with excellent charge storage performance.

Three-dimensional porous V2O5 hierarchical spheres composed of stacked platelets were fabricated by a facile, low-cost and template-free method. The synthetic route involved precipitation of precursor microspheres in aqueous solution at room temperature and subsequent calcination. Various techniques including XRD, FE-SEM, TEM, EDS, IR, Raman and nitrogen adsorption-desorption isotherms were used to reveal the composition, morphology and structure of the as-obtained porous V2O5 hierarchical spheres. The BET specific surface area of V2O5 hierarchical spheres measured 14 m2·g-1 and their average pore size reached 18.2 nm, and a majority of pores in the hierarchical structures were mesoporous. Electrochemical properties of the as-obtained three-dimensional porous V2O5 hierarchical spheres as a battery-type electrode were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The hierarchical spheres displayed excellent rate capability and an excellent capacity up to 473 C·g-1 at 0.2 A·g-1 owing to their high ion transfer speed that transpired between electrolytes and active electrode materials. A flexible hybrid supercapacitor (HSC) device was fabricated using the as-obtained three-dimensional porous V2O5 hierarchical spheres as a cathode and activated carbon as an anode and delivered an excellent capacitance of 0.26 F cm-2 at 10 mV s-1. The good electrochemical performance of the porous V2O5 hierarchical spheres indicates their high potential as a battery-type electrode material for the HSC device.