Unique Ni@NiOcore-shell/AC composite for supercapacitor electrodes

The unique composite of Ni@NiO core/shell structure and active carbon (AC) had been synthesized through a two-step method. The Ni2+ was first reduced to Ni on the surface of AC supporter. Then the NiO shell was obtained after the following oxidized treatment. The transmission electron microscopy (TEM) observed that Ni@NiO particles with thin shell were sporadically dispersed on AC surface without vast reaggregation. And the electrochemical impedance spectroscopy (EIS) showed that Ni@NiOcore-shell/AC composite had higher electrical conductivity. Thus, the outside thin NiO shell would expose more electroactive surface and shorten the ionic diffusion distance. While the Ni core could accelerate the electronic transport due to its low contact resistance. When employed as supercapacitor electrodes, Ni@NiOcore-shell/AC composite exhibited a high specific capacitance of ca. 700 F g−1 at 0.5 A g−1 and remained above 90% of the initial capacity after 1000 cycles at 1 A g−1. The high specific capacitance and long cycle life of the hybrid structure made it alternative for energy storage systems.