Development of Vanadium-Coated Carbon Microspheres: Electrochemical Behavior as Electrodes for Supercapacitors

Vanadium-coated carbon-xerogel microspheres are successfully prepared by a specific designed sol-gel method, and their supercapacitor behavior is tested in a two-electrode system. Nitrogen adsorption shows that these composite materials present a well-developed micro- and mesoporous texture, which depends on the vanadium content in the final composite. A high dispersion of vanadium oxide on the carbon microsphere surface is reached, being the vanadium particle size around 4.5 nm. Moreover, low vanadium oxidation states are stabilized by the carbon matrix in the composites. The complete electrochemical characterization of the composites is carried out using cyclic voltammetry, chronopotentiometry, cycling charge-discharge, and impedance spectroscopy. The results show that these composites present high capacitance as 224 F g(-1), with a high capacitance retention which is explained on the basis of the presence of vanadium oxide, texture, and chemistry surface.