Lawrence Berkeley National Laboratory

Si-Sn-C nanocomposites were synthesized via a facile mechanical milling method. Phase composition and morphologies of the asproduced Si-Sn-C nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Raman spectroscopy. Both XRD and Raman studies revealed the amorphization of Si after mechanical milling process, while Sn remained as the crystalline phase in both Si-Sn and Si-Sn-C nanocomposites. Meanwhile, the particle size was significantly reduced, but Si tended to agglomerate during the milling and it was alleviated through the addition of carbon. The galvanostatic charge/discharge measurements were carried out to evaluate the electrochemical performance. Compared to milled Si, Si-Sn nanocomposites, Si-Sn-C nanocomposites exhibited a higher initial capacity of ∼1000 mAh/g, and its capacity was retained at ∼80% after 50 cycles. The possible buffering effect of Sn and carbon at different operating potentials during the lithiation/delithiation process was discussed.