Morphology-conserved transformation: synthesis of hierarchical mesoporous nanostructures of Mn(2)O(3) and the nanostructural effects on Li-ion insertion/deinsertion properties

Abstract

By means of morphology-conserved transformation, we have synthesized hierarchically structured Mn(2)O(3) nanomaterials with different morphologies and pore structures. The key step of this method consists of the formation of a precursor containing the target materials interlaced with the judiciously chosen polyol-based organic molecules, which are subsequently knocked out to generate the final nanomaterials. In the present work, two kinds of precursor morphologies, oval-shaped and straw-sheaf-shaped, have been selectively prepared by hydrothermal treatment of different functional polyol molecules (oval-shape with fructose and straw-sheaf-shape with beta-cyclodextrin) and potassium permanganate. Thermal decomposition of the precursors resulted in the formation of mesoporous Mn(2)O(3) maintaining the original morphologies, as revealed by extensive characterization. These novel hierarchical nanostructures with different pore sizes/structures prompted us to examine their potential as anode materials for lithium ion batteries (LIBs). The electrochemical results with reference to LIBs show that both of our mesoporous Mn(2)O(3) nanomaterials deliver high reversible capacities and excellent cycling stabilities at a current density of 200 mA g(-1) compared to the commercial Mn(2)O(3) nanoparticles. Moreover, the straw-sheaf-shaped Mn(2)O(3) exhibits a higher specific capacity and a better cycling performance than the oval-shaped one, due to the relatively higher surface area and the peculiar nanostrip structure resulting in the reduced length for lithium ion diffusion. Morphology-conserved transformation yields two kinds of hierarchical mesoporous Mn(2)O(3) nanomaterials with high capacities and cycling stabilities for lithium ion batteries.