In-Flight Plasma Induced Silicon Synthesis and and Carbon Deposition for Lithium-Ion Battery Applications

Lithium-ion batteries are rechargeable batteries commonly used in electronics. They consist of an anode, cathode, separator, and electrolytic material that allows for charge transfer. Commercial anodes use graphite which have a limited capacity of 372 mAh/g. With a capacity of 4200 mAh/g, silicon is a much more appealing option. However, it is not highly conductive and cannot expand much without causing structural failure. To overcome this, we implement a highly conductive carbon coating. Rather than a three-part process of chemical vapor deposition (CVD) in which we first plasma-produce silicon nanoparticles (SNP), coat with carbon by flowing acetylene (C2H2) in a separate vacuum furnace, and then graphitize the coating, we simplified this by implementing a two-stage plasma set up. In the first stage, we utilize a silane plasma to synthesize SNP, immediately followed by an acetylene plasma to coat with amorphous carbon. We then anneal the carbon-coated silicon in a furnace, graphitizing the carbon coating. We perform chemical analysis on the different silicon-carbon composite structures from our tests using energy-dispersive x-ray spectroscopy (EDS) and we also utilize transmission electron microscopy (TEM) and x-ray diffraction (XRD) to determine size of particles and to confirm silicon carbide is not being produced. Following this, we make and test batteries using these novel anodes. Plasma enhanced CVD allows for lower deposition temperature and higher purity, so by employing this method, we aim to increase electrochemical performance and stability. With this method and the manipulation of different parameters, such as silicon particle size, acetylene flow, and annealing temperature, we aim to produce viable silicon based anodes with a broad range of applications throughout industry.