Facile synthesis of a graphene/nickel-cobalt hydroxide ternary hydrogel for high-performance supercapacitors

In this paper, a graphene/nickel-cobalt hydroxide ternary hydrogel (G-Ni-Co) with superior electrochemical performances was prepared by a simple hydrothermal method using Ni(NO₃)₂·6H₂O, Co(NO₃)₂·6H₂O, and graphene oxide as the starting materials. The mass fraction and the pH value of the reaction system were optimized. The prepared G-Ni-Co was assembled into a symmetric supercapacitor and its electrochemical performance was estimated. In a symmetric supercapacitor, the specific capacitance of G-Ni-Co is 551.3 F g^-1 at the scan rate of 10 mV s^-1 and 646.1 F g^-1 at the current density of 0.5 A g^-1, respectively. The specific capacitance still retains 70.8% after 5000 cycles at the scan rate of 100 mV s^-1. The energy density reaches 108.6 W h kg^-1 at a power density of 550.0 W kg^-1 and remains 72.4 W h kg^-1 at 7600.0 W kg^-1, respectively.