Mesoporous NiO nanosheets were directly grown on three-dimensional (3D) carbon cloth substrate, which can be used as binder-free anode for lithium-ion batteries (LIBs). These mesoporous nanosheets were interconnected with each other and forming a network with interval voids, which give rise to large surface area and efficient buffering of the volume change. The integrated hierarchical electrode maintains all the advantageous features of directly building two-dimensional (2D) nanostructues on 3D conductive substrate, such as short diffusion length, strain relaxation and fast electron transport. As the LIB anode, it presents a high reversible capacity of 892.6 mAh g⁻¹ after 120 cycles at a current density of 100 mA g⁻¹ and 758.1 mAh g⁻¹ at a high charging rate of 700 mA g⁻¹ after 150 cycles. As demonstrated in this work, the hierarchical NiO nanosheets/carbon cloth also shows high flexibility, which can be directly used as the anode to build flexible LIBs. The introduced facile and low-cost method to prepare NiO nanosheets on flexible and conductive carbon cloth substrate is promising for the fabrication of high performance energy storage devices, especially for next-generation wearable electronic devices.

In this paper, ZnCo₂O₄ nanowires have been grown and self-assembled as hierarchical structures on a 3D conductive Ni foam substrate. Both leaf-like ZnCo₂O₄ and dandelion-like ZnCo₂O₄ assemblies were synthesized through a hydrothermal process followed by a post-annealing treatment. It is shown that leaf-like assemblies are directly grown on the substrate while dandelion-like assemblies are adsorbed on the surface of the structures. A possible formation mechanism of ZnCo₂O₄ hierarchical structures was proposed. It is shown that these nanowires are porous structures which provide much increased specific surface area. Further work was conducted by taking these Ni foam supported ZnCo₂O₄ structures as binder-free electrodes for Li-ion batteries. Remarkably, the leaf-like ZnCo₂O₄/Ni foam electrode exhibits greatly improved electrochemical performance with high capacity and excellent cycling stability. A high reversible capacity of 1050 mA h g⁻¹ at the rate of 100 mA g⁻¹ was obtained after 60 cycles. Meanwhile, the electrode showed a high rate of 416 mA g⁻¹ with a high capacity of 850 mA h g⁻¹ even after 50 cycles. Our work demonstrates that this unique nanowire self-assembled ZnCo₂O₄ hierarchical structure is promising for high-performance electrochemical energy applications.