Chen, Jiatang (2015-12). Silicon-Incorporated Carbon Spheres As Anode Material for Lithium-ion Batteries. Master's Thesis.
In this study, a porous silicon-incorporated carbon material is studied as anode material in Lithium-ion batteries. This material is synthesized with carbonization, spray-pyrolysis and magnesiothermic reduction, from sucrose and silica as carbon and silicon precursors. Carbonization of sucrose was conducted in 0.125 M sulfuric acid with addition of colloidal silica at 90 ? for 48 hours. The C/SiO2 spheres obtained from subsequent spray-pyrolysis were reduced by magnesium at 750 ? for 2 hours in a home-made Swagelok-type stainless steel reactor. The carbon was sacrificed to maintain the spherical structure of the composite during magnesiothermic reduction while silicon formed a highly porous sponge-like structure inside the spheres. C/Si (1:8) showed high recovery (85%) of specific capacity at the second cycle. However, the rapid capacity loss of porous silicon spheres was found to be caused by fracture the of thin silicon structure. Without the carbon shell, the debris dissolved into the electrolyte easily, leading to a lower availability of the silicon material.