Self-Assembled Porous NiFe2O4 Floral Microspheres Inlaid on Ultrathin Flake Graphite as Anode Materials for Lithium Ion Batteries

A fairly simple and environmentally friendly hydrothermal method is reported to synthesize anode materials composed of NiFe2O4 (NFO) and ultrathin flake graphite (UFG), which are denoted as NFO/UFG composites. Several experiments were then carried out in order to determine the most beneficial proportion of UFG in the composite. Finally, it was found that the NFO/UFG-2 composite exhibits the most beneficial morphological structure which is characterized as three-dimensional floral NFO microspheres assembled by many porous nanosheets anchored on the pedestal of UFG (as determined from SEM and TEM measurements). In addition, the NFO/UFG-2 composite also demonstrates the best electrochemical performances. It shows a stable long-term cycling performance with a high initial Coulombic efficiency of 83.4% and even obtains a high specific capacity of 963.4 mAhg(-1) after 300 cycles at a current density of 200 mAg(-1) and remarkable reversibility not only at low current densities but also at high current densities. Satisfyingly, the good synergy between porous NFO and UFG significantly enhances the electronic conductivity and relieves the huge bulk expansion of traditional transition metal oxide. This unique electrode material is demonstrated to be a promising candidate for the new-generation lithium ion batteries.