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

Abstract 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 mAh g⁻¹ at current density of 0.1 A g⁻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.