Core-Shell Carbon Nanofibers@Ni(OH)2/NiO Composites for High-Performance Asymmetric Supercapacitors

The application of transition metal oxides/hydroxides in energy storage has long been studied by researchers. In this paper, the core-shell CNFs@Ni(OH)(2)/NiO composite electrodes were prepared by calcining carbon nanofibers (CNFs) coated with Ni(OH)(2) under an N-2 atmosphere, in which NiO was generated by the thermal decomposition of Ni(OH)(2). After low-temperature carbonization at 200 degrees C, 250 degrees C and 300 degrees C for 1 h, Ni(OH)(2) or/and NiO existed on the surface of CNFs to form the core-shell composite CNFs@Ni(OH)(2)/NiO-X (X = 200, 250, 300), in which CNFs@Ni(OH)(2)/NiO-250 had the optimal electrochemical properties due to the coexistence of Ni(OH)(2) and NiO. Its specific capacitance could reach 695 F g(-1) at 1 A g(-1), and it still had 74% capacitance retention and 88% coulomb efficiency after 2000 cycles at 5 A g(-1). Additionally, the asymmetric supercapacitor (ASC) assembled from CNFs@Ni(OH)(2)/NiO-250 had excellent energy storage performance with a maximum power density of 4000 W kg(-1) and a maximum functional capacity density of 16.56 Wh kg(-1).