▎ 摘　　要

Supercapacitors with high power density and long cycle life are of interest to complement lithium-ion batteries. However it is necessary to increase the energy density of supercapacitors for its more widely practical application. In this paper, three-dimensional porous nitrogen-doped graphene hydrogel (N-RGOH) was investigated as supercapacitor electrodes in an ionic liquid electrolyte. The X-ray diffraction, electron microscopy and X-ray photoelectron spectroscopy results show that the N-RGOH displayed 3D porous structure, large specific surface (335.6 m(2) g(-1)) and high nitrogen content (10.8 at%). The electrochemical testing shows that the N-RGOH based supercapacitor device with 3.2 V working voltage delivered a specific capacitance of 48.6 F g(-1) at 0.5 A g(-1) resulting in a high energy density of 94.5 Wh kg(-1). The N-RGOH also shows good rate and cycling performances. Our study demonstrates an effective combination of electrode and electrolyte to achieve high energy density supercapacitors for practical application. (C) 2016 Elsevier Ltd. All rights reserved.