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.