Mesoporous CoFe2O4 nanospheres cross-linked by carbon nanotubes as high-performance anodes for lithium-ion batteries

Abstract

We report the synthesis and characterization of mesoporous cobalt ferrite (CoFe₂O₄, named CFO) nanospheres cross-linked by carbon nanotubes (CNTs) as anode nanocomposites (CFO/CNT) for Li-ion batteries. CFO/CNT nanocomposites were synthesized by a facile one-pot solvothermal method using Co(CH₃COO)₂ and FeCl₃ as the metal precursors in the presence of CH₃COOK, CH₃COOC₂H₅, HOCH₂CH₂OH, and CNTs. The obtained samples were characterized by X-ray diffraction, thermogravimetric analysis, nitrogen adsorption, transmission electron microscopy, and scanning electron microscopy. It is found that most CFO nanospheres are interconnected with CNTs forming a network composite possibly due to the presence of defects at the open ends and on the external surface of CNTs. These defects may act as nucleation centers for growth of CFO nanospheres. Compared with the bare CFO nanospheres and the physically mixed CFO nanospheres with CNTs, the CFO/CNT composite containing 16.5 wt% CNTs shows much higher capacities of 1137.6, 1003.4, 867.3, and 621.7 mA h g⁻¹ at the current densities of 200, 500, 1000, and 2000 mA g⁻¹ after 10 charge–discharge cycles, respectively, and even after 100 cycles, it still maintains a high capacity of 1045.6 mA h g⁻¹ at 200 mA g⁻¹. The super electrochemical properties of the CFO/CNT composite should originate from the formed network structure with the intimate interconnection between CFO nanospheres and CNTs, which not only provides stable electrical and ionic transfer channels but also significantly shortens the diffusion length of the Li⁺ ions. This work opens a new way for fabrication and utilization of metal oxide–CNT composites as anode materials for Li-ion batteries.