High-performance asymmetric supercapacitor based on vanadium dioxide/activated expanded graphite composite and carbon-vanadium oxynitride nanostructures

The vanadium dioxide/activated expanded graphite (VO2/AEG) composite and carbon-vanadium oxynitride (C-V2NO) porous web-like structures were successfully synthesized by chemical vapor deposition (CVD) method. The X-ray diffraction analysis of the VO2/AEG composite revealed the diffraction peaks of the monoclinic VO2 and hexagonal AEG structures respectively while for the C-V2NO material, a cubic crystal structure was observed. The Raman spectroscopy analysis of VO2/AEG composite and C-V2NO depicted vibration brands linked to vanadium dioxide with the distinct D, G, and D' peaks confirming the presence of disordered carbon into the main vanadium-based matrix. The electrochemical performance of the electrode material (VO2/AEG//C-V2NO) was evaluated in a two-electrode asymmetric device with the VO2/AEG composite as the positive electrode and C-V2NO as the negative electrode operating in a 6 M KOH electrolyte. The asymmetric device exhibited a specific energy of 41.6 Wh kg(-1) with a corresponding specific power of 904 W kg(-1) at a 1 A g(-1) specific current in a large operating voltage of 1.8 V. The specific energy was still retained at 9 Wh kg(-1) at an amplified specific current of 20 A g(-1) with a specific power of 18 kW kg(-1). The supercapacitor showed a 93% capacity retention for up to 10,000 constant gravimetric current cyclic stability test at a specific current of 10 A g(-1) with a good rate capability. A notable device stability was maintained without any failure via voltage floating tests for up to 100 h. (C) 2019 Elsevier Ltd. All rights reserved.