Fabrication of vanadium oxide, with different valences of vanadium, -embedded carbon fibers and their electrochemical performance for supercapacitor

Herein, composite materials, VxOy-embedded carbon fibers, were fabricated through a facile electrospinning method followed by calcination. The as-prepared composite was characterized via X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The relevant results showed that (1) the V2O3 nanoparticles were uniformly embedded in carbon fibers (V2O3/CFs); (2) the VO2 particles were embedded in carbon fibers with mixed valence of V5+ (VO2-V2O5/CFs); and (3) amorphous V2O5 were homogeneously dispersed in carbon fibers (V2O5/CFs). The as-prepared composite was then used as a working electrode in a supercapacitor device without the addition of a binder and conductive agent, and its electrochemical properties were evaluated using cyclic voltammetry (CV), galvanostatic charge/discharge (GV), and electrochemical impedance spectroscopy (EIS). The specific capacitance values of V2O3/CFs, VO2-V2O5/CFs, and V2O5/CFs were 557 F g(-1), 476 F g(-1), and 606 F g(-1) at 0.5 A g(-1), respectively. Consequently, the samples exhibited a high cyclic stability after 5000 cycles at the current density of 5 A g(-1). These results demonstrate that the variable valence of the embedded vanadium oxide can be obtained through different calcination processes, and the electrochemical performance of V2O5/CFs is better than that of V2O3/CFs and VO2-V2O5/CFs when they are applied in a supercapacitor.