Coating of Low-Cost Asphaltenes-Derived Carbon Fibers with V₂O₅ for Supercapacitor Application

V 2 O 5 -coated, low-cost carbon fibers were produced using asphaltenes and V 2 O 3 as precursors, both industrial byproducts. Asphaltenes can be used without any further treatment to fabricate low-cost carbon fibers. The carbon fibers were coated with V 2 O 5 using a straightforward two-step coating procedure, that is, surface etching of fibers with NH 4 OH, followed by dipping into a V 2 O 3 solution. This facile process represents a time-saving and low-cost alternative to other metal oxide coating techniques, such as atomic layer deposition, to create fiber-based electrode materials. After annealing, the fibers were homogeneously coated with V 2 O 5 and exhibited porosity. Annealing time and temperature influenced the porosity and structure of the fiber material. The highest surface area (440 m 2 g –1 ) was obtained at the highest annealing temperature. The coated fibers show both micropores and mesopores. The different fiber samples were then utilized as supercapacitors using a 1 M Li 2 SO 4 electrolyte. Specific capacitances of up to 125 F g –1 at a rate of 0.25 A g –1 were achieved. Long-term cycling tests showed a capacitance retention of 89% after 10,000 cycles. A strong surface area dependence for the capacitance and increased pseudocapacitance for higher annealing temperatures are demonstrated.