Synthesis and characterization of electrochemically active graphite–silicon–tin composite anodes for Li-ion applications

Electrochemically active Si0.66Sn0.34 (SiSn) composite alloys dispersed in a carbon (graphite) matrix were synthesized using both wet and dry high-energy mechanical milling (HEMM). The resultant composites are comprised of amorphous carbon (in the case of dry HEMM) or crystalline carbon (in the case of wet HEMM), and crystalline silicon and tin (for both cases) as verified by X-ray diffraction (XRD). The XRD results also indicate the presence of iron–tin intermetallic (FeSn2) arising as a contaminant during dry HEMM. The composite composition of 85C–15[Si0.66Sn0.34] (mol%) resulted in reversible discharge capacities as high as 800 mAh g−1 with a reasonable capacity retention (1.36% loss/cycle). Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analyses were further conducted to examine the surface of the electrode and to determine the presence/absence of organic species resulting from reactions between the electrode, lithium ions and electrolyte, respectively.