Facile Synthesis of Hollow Mesoporous CoFe 2 O 4 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 CoFe 2 O 4 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 CoFe 2 O 4 crystallite building blocks to form NSs. Benefiting from the synergistic effect between the hollow 3D mesoporous CoFe 2 O 4 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.