Electrospun carbon/iron–vanadium oxide nanofibers for high energy density supercapacitors

Abstract

Highly flexible and conductive carbon nanofibers (CNFs) embedded with pseudocapacitive iron–vanadium oxide (FVO) nanoparticles were fabricated via electrospinning of a metal salt/polyacrylonitrile solution followed by high-temperature annealing (750 °C). CNFs have a graphitic structure with defects, which could accelerate electron mobility and the access of electrolytic ions to the multivalent FVO nanoparticles, respectively. Poly(methyl methacrylate) (PMMA) was introduced as a sacrificial polymer to alter the internal structure of the nanofibers and thus enhance the electrolytic ion transport pathways. Terephthalic acid was added to provide flexibility by increasing the cross-linking within the electrospun fibers. The flexible FVO/CNFs exhibited excellent electrochemical performance. The optimal sample had a high areal capacitance of 1058 mF·cm−2 at a current density of 2.5 mA·cm−2 and showed 100 % capacitance retention during long-term cycling (10,000 cycles). The capacitance at a high current density of 25 mA·cm−2 was 81.3 % of that at a current density of 2.5 mA·cm−2. Using a wider potential window of 0–1.6 V increased the energy density to 389 μW·h·cm−2. The optimal FVO/CNF sample maintained 90 % of its initial capacitance after 200 bending cycles.