Decorated carbon nanotubes by silicon deposition in fluidized bed for Li-ion battery anodes

Abstract

Multi-walled carbon nanotubes Graphistrength® were decorated with silicon by Fluidized Bed Chemical Vapor Deposition. The ability to fluidize of these nanotubes forming ball-shaped jumbles with diameters in the range of several hundreds of microns was first studied. Coating experiments from silane SiH4 were performed, in the 30-60wt. % range of silicon deposited. SEM and TEM imaging reveals that the nanotubes are coated by silicon nanoparticles uniformly distributed from the periphery to the center of the balls for the whole conditions tested. On-line acquisition of key process parameters evolution shows that the material remains fluidizable, even for large proportions of silicon deposited. The density of balls increases with the percentage of silicon deposited whereas their specific surface area decreases. This composite material is a promising candidate as anode material to replace graphite in lithium-ion batteries.