Three-dimensional functionalized graphenes with systematical control over the interconnected pores and surface functional groups for high energy performance supercapacitors

Three-dimensional functionalized multilayer graphenes (3D FMG) with systematically controllable interconnected pores and surface functional groups are prepared by using combined hydrochloric acid-assisted ultrasonic exfoliation and thermal reduction approach. Electrochemical analyses show that the optimized 3D FMG owns an amazing high specific capacitance of 508 F g^-1 at 5 mV s^-1 in aqueous electrolyte system. The energy density of 15, 32, and 66 Wh kg^-1 has been obtained at the power density of 14, 43, and 52 kW kg^-1 for the 3D FMG-based supercapacitor in the aqueous, organic and ionic liquid electrolyte system, respectively. 94% of the initial capacitance of the 3D FMG-based supercapacitor is retained after 10,000 cycles at 1 A g^-1 in the aqueous system. The outstanding electrochemical performances of the 3D FMG are attributed to the strong synergistic effect of the interconnected pores and surface functional groups. The hierarchical interconnected pore channels can efficiently facilitate the ionic/electronic transports between the electrodes and electrolyte ions and appropriately prevent the restacking of graphene sheets. The rational surface functional groups may improve a facile accessibility of the electrodes with the electrolytes and provide an additional pseudocapacitance.