Hierarchical hollow urchin-like structured MnO2 microsphere/carbon nanofiber composites as anode materials for Li-ion batteries

Abstract

In this work, novel hollow urchin-like MnO2 microspheres (u-MnO2), consisting of a hollow core with nanotubes, are synthesized by a simple hydrothermal process. The morphology of the MnO2 structures could be tuned from round particles to a hierarchical hollow urchin structure by controlling the hydrothermal reaction time, with no need for surfactant or templates. The nanostructures of the obtained u-MnO2 are characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The X-ray diffraction (XRD) pattern of the u-MnO2 reveals a tetragonal structure of α-MnO2. The carbon nanofibers (CNFs) are uniformly deposited on u-MnO2 to improve the electrical conductivity and to utilize the hierarchical architecture of u-MnO2. As the anode electrode of Li-ion batteries, the u-MnO2/CNFs nanocomposites exhibit discharge capacity of 988 mAh·g−1 after 100 cycles with a good rate capability. The superior electrochemical performances of the u-MnO2/CNFs nanocomposites can be attributed to the hierarchical urchin-like structures and the superior electrical conductivity of the nanocomposites, which can facilitate fast electron and ion transport and accommodate a large volume change during charge/discharge.