SiMn–Graphite composites as anodes for lithium ion batteries

Two Si–Mn–C composites were obtained by sequentially ball milling the mixture of the silicon and manganese powders (atomic ratio of 3:5), followed by addition of 20 wt.% and 10 wt.% graphite, respectively. The phase structure and morphology of the composite were analyzed by X-ray diffraction (XRD) and scanning electromicroscopy (SEM). The results of XRD show that there is no new alloy phase in the composite obtained by mechanical ball milling. SEM micrographs confirm that the particle size of the Si–Mn–C composite is about 0.5–2.0 μm and the addition of graphite restrains the morphological change of active center (Si) during cycling. The Si–Mn particles are dispersed among the carbon matrix homogeneously, which ensures a good electrical contact between the active particles. Electrochemical tests show that the Si–Mn–C composite achieves better reversible capacity and cycleability. The Si–Mn–20 wt.% C composite electrode annealed at 200 °C for 2 h reveals an initial reversible capacity of 463 mAh·g− 1 and retains 387 mAh·g− 1 after 40 cycles.