One-pot synthesis of manganese oxide-carbon composite microspheres with three dimensional channels for Li-ion batteries

Abstract

The fabrication of manganese oxide-carbon composite microspheres with open nanochannels and their electrochemical performance as anode materials for lithium ion batteries are investigated. Amorphous-like Mn3O4 nanoparticles embedded in a carbon matrix with three-dimensional channels are fabricated by one-pot spray pyrolysis. The electrochemical properties of the Mn3O4 nanopowders are also compared with those of the Mn3O4-C composite microspheres possessing macropores resembling ant-cave networks. The discharge capacity of the Mn3O4-C composite microspheres at a current density of 500 mA g(-1) is 622 mA h g(-1) after 700 cycles. However, the discharge capacity of the Mn3O4 nanopowders is as low as 219 mA h g(-1) after 100 cycles. The Mn3O4-C composite microspheres with structural advantages and high electrical conductivity have higher initial discharge and charge capacities and better cycling and rate performances compared to those of the Mn3O4 nanopowders.

Figure 1. Morphologies of the Mn₃O₄-C composite microspheres with open-nanochannels: (a) SEM image, (b) SEM image of the crushed powders, (c)–(e) TEM images, (f) SAED pattern, and (g) dot-mapping images.

Figure 2. XRD patterns of the Mn₃O₄-C composite microspheres and Mn₃O₄ nanopowders.

Figure 3. Morphologies and dot-mapping images of the well-faceted Mn₃O₄ nanopowders prepared by flame spray pyrolysis: (a) TEM image, (b) high-resolution TEM image, and (c) dot-mapping images.

Figure 4. Electrochemical properties of the Mn₃O₄-C composite microspheres and Mn₃O₄ nanopowders: (a) and (b) charge/discharge curves of the Mn₃O₄-C composite microspheres and Mn₃O₄ nanopowders at a constant current density of 500 mA g⁻¹, respectively, and (c) and (d) CVs of the Mn₃O₄-C composite microspheres and Mn₃O₄ nanopowders, respecitvely.

Figure 5. (a) Cycling performances and (b) Coulombic efficiencies of the Mn₃O₄-C composite microspheres and Mn₃O₄ nanopowders at a constant current density of 500 mA g⁻¹, and SEM images of the Mn₃O₄-C composite microspheres after (c) 200 and (d) 700 cycles.

Figure 6. Electrochemical properties of the Mn₃O₄-C composite microspheres and Mn₃O₄ nanopowders: (a) rate performances and Nyquist plots of the electrochemical impedance spectra (b) before and (c) after 50 cycles at a current density of 500 mA g⁻¹.