Charge storage mechanism in vanadium telluride/carbon nanobelts as electroactive material in an aqueous asymmetric supercapacitor

A novel one-step method for fabricating vanadium telluride nanobelt composites for high-performance supercapacitor applications is reported. The nanobelts are realized by direct tellurization of vanadium oxide in-situ formed via decomposition of ammonium metavanadate in argon atmosphere. Use of melamine as precursor helps in forming graphitic carbon layers during pyrolization on which the nanobelts are grafted. Morphological analysis suggests interconnected nanobelts of ∼23.0 nm width coming out of carbon structure. As pseudocapacitive electrode, vanadium telluride/carbon (C) composite exhibits interesting electrochemical performance within a potential window of 0-1.0 V in 1.0 M sodium sulfate electrolyte along with excellent capacitance retention during 5000 cycles. In-depth analysis suggests that the charge storage mechanism in the composite is governed by both diffusion-controlled and diffusion-independent processes with the former dominating at slower scan rates and later at faster scan rates. The asymmetric supercapacitor assembled using vanadium telluride/C and activated charcoal (AC) as respective positive and negative electrodes exhibited an energy/power combination of 19.3 Wh/kg and 1.8 kW/kg within a potential window of 0-1.8 V in aqueous electrolyte. This strategy to improve capacitance along with potential window in an aqueous electrolyte would facilitate development of high-performance energy storage devices with metal chalcogenides.