Fabrication of Carbon-Encapsulated Mono- and Bimetallic (Sn and Sn/Sb Alloy) Nanorods. Potential Lithium-Ion Battery Anode Materials

Novel carbon-encapsulated mono- and bimetallic (Sn and Sn/Sb alloy) core-shell nanorods were synthesized as potential anode materials for future lithium-ion batteries by a reductive, thermochemical vapor deposition at different acetylene/nitrogen (1:9) gas flow rates (20, 30, and 200 sccm) between 750 and 810 degrees C over SnO2/Sb2O10 and SnO2 nanopowders. Their morphologies and structures were characterized by SEM and TEM. Nanorod morphologies varied depending on the acetylene flow rate. The outer carbon layer thickened with time. More irregular nonuniform growth occurred at longer growth periods at 810 degrees C, giving spherical, conical, bulblike, and/or lumpy structures containing various amounts of metal. Sharp powder X-ray diffraction (XRD) peaks proved that well-crystallized Sn metal and Sn/Sb alloy formed within the carbon shells. Certain conditions generated some SnO2 within the carbon shell. X-ray photoelectron spectroscopy (XPS) determined the elements present and their oxidation states. The main carbon peak in all nanorods was graphitic carbon. C-1s and O-1s high-resolution spectra confirmed a variety of oxygenated carbon species were present on the outer carbon surface region. The metallic core in the carbon-encased Sn nanorods contained Sn metal, SnO2, and possibly SnO (XPS), in good agreement with XRD measurements.