Ni(OH)2/CNTs/graphene composite with 3D hierarchical structure for supercapacitors with high performance

After twice heat-treating and ball-milling, the dimension of CNTs is shorter and the ends are open. By using the treated CNTs, graphene, and Ni(NO3)2, Ni(OH)2/CNTs/graphene ternary composites were synthesized through galvanostatic electrodeposition under supergravity field. The ternary composite presents a 3D hierarchical structure, in which graphene as the substrate primarily plays a role of external connection and conduction, while CNTs mainly have an effect on internal conduction. Ni(OH)2 flower spheres are distributed on the graphene nanosheets. The composite shows excellent performance of supercapacitance due to its special structure. The specific capacitance of Ni(OH)2/CNTs/graphene is 2868.5 F g−1 at a current density of 0.5 A g−1, which is much higher than Ni(OH)2, Ni(OH)2/graphene, and Ni(OH)2/CNTs. In addition, it still could reach 1247.9 F g−1 at a current density of 4 A g−1. This approach will be significant for the development of energy storage materials with high performance.