Principles of Carbon Scaffold Selection for Silicon/Carbon Composite Battery Anodes

Silicon/carbon (Si/C) composites are now the demonstrated successor to graphite as high-energy density lithium-ion battery (LIB) anodes due to the increased capacity of silicon and only slight change to the overall charge/discharge potential and reversibility in optimized cases. However, selection of the scaffold and overall guiding principles for the composite structure remain under active investigation. Herein, three carbon scaffold families spanning a broad phase space of crystallinity and surface area were employed as substrates for silane and acetylene deposition experiments to yield Si/C composites with varying structural characteristics and compositions. Differential thermogravimetric analysis (DTGA) was employed to determine the content of silicon, carbon, and silicon oxide present in each Si/C composite. The silicon environments formed in the composites could be distinctly classified as Type I (intraparticle, nanoscale) or Type II (interparticle, bulk scale) by comparison to a series of pure silicon samples. These classifications were correlated with electrochemical performance, demonstrating that Type I and Type II silicon contents could be relevant predictors for the LIB performance of present and future Si/C composite anodes.