Graphene-Carbon Nanotube Aerogel with a Scroll-Interconnected-Sheet Structure as an Advanced Framework for a High-Performance Asymmetric Supercapacitor Electrode

Carbon nanomaterials have received much attention due to their good electrochemical performance as electrode materials and as substrates for pseudocapacitive materials. Herein, the graphene-carbon nanotube aerogel (GCA) has been constructed by direct cryodesiccation from the aqueous dispersion of a graphene oxide-carbon nanotube hybrid, the so-called "sol-cryo" method, followed by high-temperature carbonization. The as-obtained GCA with a unique sheet-scroll conjoined architecture not only displays an excellent electrical double-layer capacitive performance but also performs as an ideal three-dimensional template for the perpendicular immobilization of Ni(OH)(2) nanosheets. The capacitance of Ni(OH)(2)@GCA is 1208 F g(-1) at 1 A g-1 with 88% retention after 2000 cycles. The Ni(OH)(2)@GCA//GCA asymmetric supercapacitor exhibits a high energy density of 30 Wh kg(-1) at a power density of 820 W kg(-1). In addition, this template-free sol-cryo method possesses simplicity and large-scale availability, which provides a novel approach for fabricating macroscopic electrode materials for supercapacitors.