Facile Synthesis of Hollow Mesoporous CoFe2O4Nanospheres 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 (≈1030 mA h g−1 after 60 cycles at 100 mA g−1), enhanced rate capability (≈970, ≈850, ≈555 mA h g−1 at 100, 500, 5000 mA g−1, respectively), and superior cyclic stability (≈805 mA h g−1 after 305 cycles at 2000 mA g−1 with a high coulombic efficiency of ≈99.5 %); these composites are thus high-performance anode materials for lithium ion batteries.