Self-assembly of hierarchical Fe3O4 microsphere/graphene nanosheet composite: towards a promising high-performance anode for Li-ion batteries

A hierarchical Fe3O4 microsphere/graphene nanosheet (H-Fe3O4-MS/GNS) composite has been synthesized by a facile one-pot solvothermal route. The Fe3O4 microspheres uniformly decorated the surface of the two dimensional GNS. Each Fe3O4 microsphere possesses a hierarchical and porous structure, which is composed of Fe3O4 nanoparticles with a diameter of about 10 nm. As an anode material for Li-ion batteries, the H-Fe3O4-MS/GNS composite shows high specific capacity and good cycling stability (1171.6 mA h g(-1) at 200 mA g(-1) and 940.4 mA h g(-1) at 500 mA g(-1) up to 70 cycles), reduced voltage hysteresis, as well as enhanced rate capability. The improved electrochemical performance can be attributed to the combination of the conductivity, confinement and dispersion effects of GNS and the porous hierarchical structure of the Fe3O4 microsphere.