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 N2 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.