Effect of Methane Injection Methods on the Preparation of Silicon Nanoparticles with Carbon Coating in Induction Thermal Plasma

Induction thermal plasma is applied to prepare carbon coated silicon nanoparticles as the anode materials of a battery and the effect of methane injection methods is investigated. Silicon nanoparticles are fabricated as main products and show spherical morphologies with an average diameter of around 50 nm. The unfavorable formation of SiC, which is a byproduct and limits the practical capacity of batteries, can be identified when the methane injection position is near to plasma torch. An amorphous hydrogenated carbon coating is synthesized successfully instead of pure carbon materials. The CH4 injection position can determine the decomposition temperature of methane as well as the concentration of released H atoms. Consequently, the properties of prepared carbon coatings, including the sp2 ratio and H content, are tunable with injection positions through the etching effect of hydrogen atoms. These results are significant for the synthesis of silicon nanoparticles with carbon coating and the design of lithium ion batteries with higher energy density.