Fe3O4 Hollow Nanosphere-Coated Spherical-Graphite Composites: A High-Rate Capacity and Ultra-Long Cycle Life Anode Material for Lithium Ion Batteries

The spherical-graphite/Fe3O4 composite has been successfully fabricated by a simple two-step synthesis strategy. The oxygenous functional groups between spherical-graphite and Fe3O4 benefit the loading of hollow Fe3O4 nanospheres. All of the composites as anodes for half cells show higher lithium storage capacities and better rate performances in comparison with spherical-graphite. The composite containing 39 wt% of hollow Fe3O4 nanospheres exhibits a high reversible capacity of 806 mAh g−1 up to 200 cycles at 0.5 A g−1. When cycled at a higher current density of 2 A g−1, a high charge capacity of 510 mAh g−1 can be sustained, even after 1000 long cycles. Meanwhile, its electrochemical performance for full cells was investigated. When matching with LiCoO2 cathode, its specific capacity can remain at 137 mAh g−1 after 100 cycles. The outstanding lithium storage performance of the spherical-graphite/Fe3O4 composite may depend on the surface modification of high capacity hollow Fe3O4 nanospheres. This work indicates that the spherical-graphite/Fe3O4 composite is one kind of prospective anode material in future energy storage fields.