Si–Mn composite anodes for lithium ion batteries

Si–Mn composites were prepared by mechanical ball milling for different periods. The microstructure and electrochemical performance of the composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical methods. XRD showed that the materials prepared by ball milling were composites consisting of Si and Mn powders. The particle size was about 1 μm from the SEM images. The Si–Mn composites after 60 h ball milling showed the best performance, especially when annealed at 300 °C for 2 h, which had a reversible capacity of 455 mAh g−1 and an initial Coulomb efficiency of 52%. Mn acted as an inactive buffer of the Si–Mn composite electrode and enhanced the cyclic performance of the active center (Si). It was also observed that nanosized Si–Mn particles merged together after the insertion/extraction of lithium ions, which decreased the electric contact between the active materials and copper substrate.