Facile Synthesis of Hollow Mesoporous CoFe₂O₄ Nanospheres and Graphene Composites as High-Performance Anode Materials for Lithium-Ion Batteries

A novel, facile, self-assembly approach, based on a gas-bubble-template model and assisted by graphene oxide, is developed to fabricate hollow 3D mesoporous CoFe₂O₄ nanospheres (NSs) and graphene composites. During the hydrothermal process, the oxygen-containing functional groups and defect sites on the graphene sheets act as nucleation centers to anchor released gas bubbles, providing a soft template for the aggregation of nanosized CoFe₂O₄ crystallite building blocks to form NSs. Benefiting from the synergistic effect between the hollow 3D mesoporous CoFe₂O₄ NSs and graphene, the electrode exhibited remarkable electrochemical performance with a high reversible capacity (≈1030mAhg^-1 after 60cycles at 100mAg^-1), enhanced rate capability (≈970, ≈850, ≈555mAhg^-1 at 100, 500, 5000mAg^-1, respectively), and superior cyclic stability (≈805mAhg^-1 after 305cycles at 2000mAg^-1 with a high coulombic efficiency of ≈99.5%); these composites are thus high-performance anode materials for lithium ion batteries.