Multiwalled carbon nanotube-cobalt vanadium oxide composite for high-performance supercapacitor electrodes with enhanced power density and cycling stability

Abstract

Supercapacitors are becoming increasingly popular as energy storage devices due to their fast charging and discharging characteristics, high power densities, and extended operational lifespans. However, achieving high energy densities while maintaining excellent cycling stability remains a significant challenge. This study investigates the potential of cobalt vanadium oxide (Co₃V₂O₈ or CVO-U) doped with multiwalled carbon nanotubes (CNTs) as an advanced electrode material for high-performance supercapacitors. The CNT-U-CVO composite was synthesized via a hydrothermal method and comprehensively characterized using various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron microscopy and electrical characterizations. The incorporation of CNTs into the CVO-U material resulted in significant enhancements in electrochemical performance. The CNT-U-CVO composite demonstrated an energy density of 8.49 Wh/kg (37 mWh/cm²) and an specific capacitance of 244 F/g (1076 mF/cm²), outperforming the pristine CVO material. The CNT-U-CVO composite exhibited optimal capacitance behavior, improved charge transfer kinetics, and accelerated ion transport, as demonstrated by cyclic voltammetry and galvanostatic charge-discharge experiments. These results were attributable to the CNTs' increased surface area and better electrical conductivity. A supercapacitor device with an asymmetric design was created using the CNT-U-CVO composite as the positive electrode and activated carbon as the negative electrode. This device exhibited outstanding performance, with an energy density of 6.93 Wh/kg (0.12 mWh/cm²), a power density of 320 W/kg (5.6 mWh/cm²), and remarkable cycling stability. It retained 72 % of its initial capacitance even after undergoing 6000 charge-discharge cycles. The results emphasize the promise of CNT-U-CVO materials as very attractive candidates for energy storage applications with superior performance, including enhanced energy density, power density, and cycling stability.