Superior Electrochemical Properties of Composite Microspheres Consisting of Hollow Fe₂O₃ Nanospheres and Graphitic Carbon

Several micron-sized composite microspheres comprising hollow metal oxide nanospheres and in situ-formed graphitic carbon (GC) can be efficiently applied as anode materials for lithium-ion batteries. Herein, unique porous structured microspheres consisting of hollow Fe2O3 nanospheres and GC layers are prepared by spray drying. Fe nanocrystals are formed by carbothermal reduction. They are responsible for the transformation of the dextrin-derived amorphous carbon (AC) into well-developed GC layers, while the excess amount of dextrin remains as AC. The key point is the selective elimination of the AC without burning, which is achieved by a low-rate airflow during the oxidation process. Finally, porous- and hierarchical-structured Fe2O3-GC composite microspheres are obtained via Kirkendall diffusion. Because of their superior structural stability and excellent electrical conductivity, the porous-structured Fe2O3-GC microspheres show excellent lithium-ion storage performances. The discharge capacity of Fe2O3-GC-350 for the 1000th cycle at 3 A g–1 is 760 mA h g–1, and their capacity retention calculated from the second cycle is 92%