Prussion blue-supported annealing chemical reaction route synthesized double-shelled Fe₂O₃/Co₃O₄ hollow microcubes as anode materials for lithium-ion battery.

Fe2O3/Co3O4 double-shelled hierarchical microcubes were synthesized based on annealing of double-shelled Fe4[Fe(CN)6]3/Co(OH)2 microcubes, using Co(AC)2 as a Co(2+) source to react with OH(-) generated from the reaction of ammonium hydroxide and water. The robust Fe2O3 hollow microcube at the inner layer not only displays a good electronic conductivity but also acts as stable supports for hierarchical Co3O4 outside shell consisting of nanosized particles. The double-shelled hollow structured Fe2O3/Co3O4 nanocomposites display obvious advantages as anode materials for LIBs. The hollow structure can ensure the presence of additional free volume to alleviate the structural strain associated with repeated Li(+)-insertion/extraction processes, as well as a good contact between electrode and electrolyte. The robust Fe2O3 shell acts as a strong support for Co3O4 nanoparticles and efficiently prevents the aggregation of the Co3O4 nanoparticles. Furthermore, the charge transfer resistance can be greatly decreased because of the formation of interface between Fe2O3 and Co3O4 shells and a relative good electronic conductivity of Fe2O3 than that of Co3O4, resulting in a decrease of charge transfer resistance for improving the electron kinetics for the hollow double-shelled microcube as anode materials for LIBs. The Fe2O3/Co3O4 nanocomposite anode with a molar ratio of 1:1 for Fe:Co exhibits the best cycle performance, displaying an initial Coulombic efficiency of 74.4%, delivering a specific capacity of 500 mAh g(-1) after 50 cycles at a current density of 100 mA g(-1), 3 times higher than that of pure Co3O4 nanoparticle sample. The great improvement of the electrochemical performance of the synthesized Fe2O3/Co3O4 double-shelled hollow microcubes can be attributed to the unique microstructure characteristics and synergistic effect between the inner shell of Fe2O3 and outer shell of Co3O4.