Hierarchical Hybrids of Mesoporous NiCo2O4 Needles/Graphene/Carbon Nanotubes with High Performance for Lithium Ion Batteries and Oxygen Reduction Reactions

Three-dimensional (3D) hierarchical NiCo2O4-graphene/carbon nanotube (NiCo-G/CNT) hybrids with NiCo2O4 needles deposited on a conductive G/CNT template have been facilely produced by a co-precipitation method. Mesoporous NiCo2O4 needles endow the NiCo-G/CNT hybrids with high specific surface area, which allows good electrolyte penetration and large electrode-electrolyte contact area, leading to fast ion and electron transfer and excellent strain accommodation. The unique hierarchical structures of NiCo-G/CNT hybrids ensure complete exposure of their active sites and endow them with dual functionalities that allow them to serve as high-performance electrodes for both lithium-ion batteries and oxygen reduction reactions. In particular, the NiCo4-G/CNT sample delivers a remarkable specific capacitance of 1392 mAhg(-1) at current density of 0.1 Ag-1, and achieves high electrocatalytic activity with long-term stability for ORR. This preparation strategy is simple and effective, and can be conveniently extended to fabricate other kinds of binary-oxide-based materials for energy-storage applications.