Growth of silicon/carbon microrods on graphite microspheres as improved anodes for lithium-ion batteries

We report a facile chemical vapor deposition (CVD) method to grow silicon/carbon (Si/C) microrods on the surface of commercial graphite microspheres (GMs) to prepare Si/C/GM composite materials as Li-ion battery anodes. Dimethyldichlorosilane and toluene were used as Si and C precursors, respectively. The CVD temperature and time, as well as the mechanism of materials growth were investigated. The samples were characterized by using X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. It was found that the obtained Si/C/GM composites with an urchin-like morphology are composed of Si particles, amorphous carbon, and graphite. The CVD conditions have a significant impact on the morphology and electrochemical performance of the composite materials. The composite prepared under the optimum CVD conditions, namely at 900 °C for 5 h, displayed the best anode properties with a specific capacity of 562.0 mA h g−1 at a current density of 50 mA g−1, much higher than that of GMs (361.0 mA h g−1), and a good cycling performance (i.e., a reversible capacity of 590.5 mA h g−1 after 50 cycles). The improved electrochemical performance is attributed to the incorporation of Si, together with the formation of a Si/C microrod network, which connects the GMs and buffers the volume change of Si during lithium ion insertion/extraction. The work provides a simple and low-cost route to enhance the performance of commercial graphite anode materials for Li-ion batteries.