Iron oxide/carbon microsphere lithium-ion battery electrode with high capacity and good cycling stability

Iron oxide/carbon composite microspheres were prepared by a simple solution polymerization followed by pyrolysis in flowing nitrogen atmosphere at high temperature. The composites were characterized using various characterization techniques including powder X-ray diffraction, high resolution transmission electron microscopy, scanning electron microscopy, N2 physical adsorption and the electrochemical performance test. The results show that the iron oxide/carbon composites consist of uniform microspheres with an average diameter of ∼2.1 μm. These iron oxide/carbon composite microspheres exhibit high capacity and good cycle stability when used as a lithium-ion battery anode. When the iron oxide content is 66%, the composite reveals the best electrochemical performance with an initial charge capacity of 730 mAh g−1, and even after ninety cycles the electrode still maintains a capacity of 664 mAh g−1, giving high capacity retention of 91%. The good electrochemical performance of the composite anode is close related with its structure, in which Fe2O3 particles are uniformly dispersed in the spherical carbon matrix; hence the volume change and aggregation of the Fe2O3 particles during lithium ion insertion/extraction process can be effectively hindered by the carbon matrix. On the other hand, carbon itself is an electronic conductor, the carbon layer and Fe2O3 particles connect closely, which ensures a good electrical contact during lithium insertion and extraction.