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