Designing a carbon nanofiber-encapsulated iron carbide anode and nickel-cobalt sulfide-decorated carbon nanofiber cathode for high-performance supercapacitors.

To meet the crucial demand for high-performance supercapacitors, much effort has been devoted to exploring electrode materials with nanostructures and electroactive chemical compositions. Herein, iron carbide nanoparticles are encapsulated into carbon nanofibers (FeC@CNF-650) through electrospinning and annealing methods. Nickel-cobalt sulfide nanoparticles are hydrothermally grown on electrospun carbon nanofibers (CNF@NiCoS-650). The Faradaic electrochemical reactions of transition metal compounds improve the specific capacitance of the developed electrode. Meanwhile, the electrically conductive framework of carbon nanofibers facilitates Faradic charge transport. In detail, the FeC@CNF-650 anode and CNF@NiCoS-650 cathode achieve specific capacitances of 1551 and 205 F g, respectively, at a current density of 1 A g. A hybrid supercapacitor that is fabricated from the FeC@CNF-650 anode and CNF@NiCoS-650 cathode delivers an energy density of 43.2 Wh kg at a power density of 800 W kg. The designed nanostructures are promising for practical supercapacitor applications.