Coating of Vanadium Nitride Onto Carbon Nanotubes: A Binder-Free Supercapacitor Electrodes

Abstract

Supercapacitors are one of the most promising energy storage devices, which could be used in hybrid vehicles, portable electronics and other pulse-power applications. Electrodes however play a crucial role in determining the performance of supercapacitors and current study mainly focused on transition metal oxides/nitrides and conducting polymers that show a large pseudo-capacitance in repeated charging-discharging profiles. Among these materials, the vanadium nitride (VN) possesses a high specific capacitance and chemical stability and is metallic in nature. VN, however, is often made in powder form and must combine with polymer to form electrode. In this case, conductivity and ionic accessibility, due to polymer addition, are reduced and capacitance also decreases at high voltage scan rates. In this work, the carbon nanotubes (CNTs) are electrochemically coated onto nickel mesh and sol-gel technique is then used to deposit V 2 O 5 onto tube coatings, followed by calcining composite under anhydrous ammonia atmosphere. The morphology and structural properties of electrode are characterized by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Raman measurement, and X-ray photoelectron spectrometer (XPS). A three-electrode system is employed to study the electrochemical behavior, including cyclic voltammetry (CV), galvanostatic charge–discharge cycling (CD). The experimental results suggest that CNTs provide an open mesoporous texture for access of electrolytes and conductive path for electron transfer to Ni collector.