Carbon–fiber–silicon-nanocomposites for lithium-ion battery anodes by microwave plasma chemical vapor deposition

The paper presents a new synthesis method for nanocomposites made from amorphous and nanocrystalline silicon deposited on a carbon fiber substrate and the Li-ion battery anode performance results achieved with such nanocomposites. Atmospheric microwave plasma coating enables deposition of nanosized silicon onto the 3D-carbon fiber substrate containing graphite as filler. The microstructure and composition of the nanocomposites is characterized by means of XRD, SEM, Raman spectroscopy and N 2 gas adsorption. Amorphous silicon and nanocrystalline silicon act together with the graphitic carbon as Li-intercalation material. Excellent adhesion to the “electrical network” provided by the carbon fibers is observed. In half-cell measurements versus lithium, a stable capacity is found even at multiple cycling with high charge/discharge current. Anodes for Li-ion batteries made from the new material have the potential to significantly increase the reversible capacity of the battery. For example, more than 700 mAh g −1 is obtained for a composite with a silicon content of less than 20 wt.%. The irreversible specific capacity is comparable to the one of an unmodified carbon fiber substrate.