Controlled Growth of Porous α-Fe2O3 Branches on β-MnO2 Nanorods for Excellent Performance in Lithium-Ion Batteries

Hierarchical nanocomposites rationally designed in component and structure, are highly desirable for the development of lithium-ion batteries, because they can take full advantages of different components and various structures to achieve superior electrochemical properties. Here, the branched nanocomposite with -MnO2 nanorods as the back-bone and porous -Fe2O3 nanorods as the branches are synthesized by a high-temperature annealing of FeOOH epitaxially grown on the -MnO2 nanorods. Since the -MnO2 nanorods grow along the four-fold axis, the as-produced branches of FeOOH and -Fe2O3 are aligned on their side in a nearly four-fold symmetry. This synthetic process for the branched nanorods built by -MnO2/-Fe2O3 is characterized. The branched nanorods of -MnO2/-Fe2O3 present an excellent lithium-storage performance. They exhibit a reversible specific capacity of 1028 mAh g(-1) at a current density of 1000 mA g(-1) up to 200 cycles, much higher than the building blocks alone. Even at 4000 mA g(-1), the reversible capacity of the branched nanorods could be kept at 881 mAh g(-1). The outstanding performances of the branched nanorods are attributed to the synergistic effect of different components and the hierarchical structure of the composite. The disclosure of the correlation between the electrochemical properties and the structure/component of the nanocomposites, would greatly benefit the rational design of the high-performance nanocomposites for lithium ion batteries, in the future.