Nickel/cobalt metal-organic framework derived 1D hierarchical NiCo2O4/NiO/carbon nanofibers for advanced sodium storage

Rational design of nanostructured metal oxides with carbon substrates is urgently needed to improve the electrochemical properties of sodium-ion batteries (SIBs). In this paper, the preparation of one-dimensional (1D) metal-organic frameworks grown on polymer(Co/Ni) fiber films via a feasible electrospinning method and in situ growth strategy is reported. After successive carbonization and oxidation heat-treatments, hierarchical heteroatom-doped carbon nanofibers decorated with several nanocomposites (denoted as NiCo2O4/NiO/carbon nanofibers) were obtained. When their electrochemical properties were evaluated by testing Na half-cells, the resultant sample displayed a high sodium-storage capacity of 210 mAh g(-1) after 200 cycles at a current density of 100 mA g(-1) and an outstanding rate capability. The enhancement of the sodium-storage performance of NiCo2O4/NiO/carbon nanofibers was ascribed to the novel structure and the synergistic effect between Co/Ni-Oxide and carbon component. The 1D carbonized nanofibers are well intertwined to form a three-dimensional conductive matrix with heterogeneous particles embedded, which can effectively reduce the ionic diffusion distance and ensure high electronic mobility along their 1D geometry, leading to rapid diffusion kinetics. Furthermore, well-dispersed heterogeneous particles endow the composite high surface to exposure to the electrolyte, which can contribute to a high utilization rate.