Abstract
Silicon is one of the most important alloying elements used in Li-ion battery negative electrodes due to its low cost and high energy density. Inductive-coupled plasma (ICP) offers a scalable, low cost, and sustainable manufacturing process, which has been proven as an effective method to produce ultrafine nano powders including Si nanoparticles. Non-thermal plasma (NTP) offers highly reactive atmosphere at low temperature that is beneficial for activating gases as coating media for nanomaterials without changing the intrinsic properties of the particles.
In this work, we integrated a NTP injector at the downstream of an ICP plasma Nano-reactor for developing Silicon nanoparticle (core) with carbon coating (shell). Solid Silicon powder was injected into the ICP plasma torch (temperature ~10000K) to generate Si vapor, which will be quickly quenched with a fast-cooling rate of up to 105-107K/s to create nano-sized Silicon particles. Downstream of the plasma reactor, the NTP injector will add carbonaceous precursor (C2H4) to form carbon core-shell structure with the synthesized Silicon particles. Optical Emission Spectroscopy (OES) was employed for in-situ plasma diagnostics and process optimization. This combines two steps in one and improves the control of the surface chemistry of the nano materials by preventing any contact of the highly reactive surface with air. It also provides a critical manufacturing route for large scale Silicon nano powder for high performance batteries application.