Hydrothermal growth of vanadium pentoxide nanofibers on carbon nanofiber mat: An anodic material for solid-state asymmetric supercapacitors

A supercapacitor is an excellent energy storage solution due to its high-power density, rapid charge and discharging, and long cycle life. However, the main technical issue with supercapacitors is low energy density. One potential solution is to develop advanced electrode materials that store more energy. In this study, we have grown 1D vanadium pentoxide nanofibers (VNFs) on a carbon nanofibers (CNFs) mat via a hydrothermal approach. The morphological study showed that the hybrid mat consists of a sandwich structure of VNFs and CNFs with a large surface area and plenty of pores, which facilitates efficient ion transport and electron movement important for high capacitance. Furthermore, a synergistic combination of pseudo-capacitance and electrical double layer capacitance (EDLC) from redox active VNFs and porous CNFs produces high capacitances of 700.1 and 615.2 F/g at 0.1 A/g in neutral electrolytes such as Na₂SO₄ and Li₂SO₄, respectively. A flexible prototype supercapacitor was constructed using a VNF/CNF hybrid mat as an anode, activated carbon cloth as a cathode, and a Na₂SO₄ or Li₂SO₄-loaded polyvinyl alcohol (PVA) membrane as an electrolyte-cum-separator. These ASC devices delivered high energy density of 72.51 and 51.83 Wh/kg with Na₂SO₄ and Li₂SO₄-based electrolytes, respectively, which are superior to those obtained from previously reported ASCs made with various V₂O₅/C anodes. The PVA-based membrane electrolytes provide excellent bending stability and leakage-proof features to ASCs, which are critical to flexible and wearable electronics.