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)center dot 6H(2)O, Co(NO3)(2)center dot 6H(2)O, 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 kr, and remains 72.4 W h kg(-1) at 7600.0 W kg(-1), respectively. (C) 2018 Elsevier Inc. All rights reserved.