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

Abstract

Herein, composite materials, V_xO_y-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.