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 °C, 250 °C and 300 °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 .