Silicon-carbon composites for lithium-ion batteries: A comparative study of different carbon deposition approaches

Silicon-carbon composites, usually in the form of core–shell silicon-carbon nanostructures, have been widely investigated as potential candidates for the replacement of graphite in anodes for lithium ion batteries. Due to the availability of a broad range of precursors and protocols for the realization of a carbon shell, research groups active in this area have typically developed their own strategy to manufacture the desired structure. This is problematic since it does not allow for a direct comparison of the performance of similar structures during electrochemical cycling, and it does not provide a mechanistic insight into the factors affecting battery performance. In this work, the authors address this issue by directly comparing core–shell silicon-carbon nanostructures in which the carbon shell is achieved by carbonization of common polymers or by chemical vapor deposition (CVD) using acetylene as precursor. The samples have been prepared using exactly the same type of silicon particles as the active material, thus allowing a direct comparison between the different carbon shell growth approaches. The authors have found that the CVD process is preferable because it allows (1) a more direct tuning of the carbon-to-silicon ratio, (2) it leads to a conformal coating of the silicon particles with a carbon layer, and (3) it avoids exposing the particles to an oxidizing environment during the coating process. Anodes fabricated using the CVD-process nanoparticles clearly show better performance compared to those fabricated using a polymer carbonization approach.