Preparation of Carbon-Coated Silicon Nanoparticles with Different Hydrocarbon Gases in Induction Thermal Plasma

Silicon appears as a promising candidate to replace the graphite anode for lithium ion batteries (LIBs) due to its extremely high charge capacity. However, the large volume expansion during charging leads to serious stability problems. Silicon nanoparticles coated with protective coatings are reliable to solve this problem and facilitate the practical implementation of the silicon anode. In this study, induction thermal plasma was applied to synthesize silicon nanoparticles with amorphous hydrogenated carbon coating, and the effects of additional carbon sources were investigated. A novel but simple injection method of hydrocarbons was introduced to limit the unfavorable formation of byproducts. The thickness of carbon coating ranges from 2 to 8 nm with a higher hydrocarbon gas flow rate, while silicon particles show a constant mean diameter of around 70 nm. The properties of carbon coating, like sp2 ratio and H-content, are tunable, and the thermal decomposition mechanism of carbon sources is believed as a key factor. Graphene flakes can also be obtained with abundant carbon and hydrogen radicals released. Based on the material characterizations, acetylene is regarded as a better candidate to prepare carbon coating. The above results show significance for the design of next generation of LIBs.