Carbon fibers obtained by pyrolysis of tailored resorcinol/formaldehyde polymer particles were used to anchor Si nanoparticles at their surface. The carbonization process, carried out at 1000 °C under nitrogen, induced strong interactions between Si particles and the carbon matrix through a thick amorphous silicon oxide layer as revealed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Therefore, the actual composition of the composites was Si/SiOx/C (fibers). Component contents were determined from thermogravimetric measurements (TG) made under oxygen. The composites delivered specific capacities as high as 2500 mA h gSi−1 at rather high current densities (500 mA gsi−1) and exhibited good capacity retention on cycling. By contrast, a mixture of pristine Si nanoparticles and carbon nanofibers performed considerably worse, their capacity fading abruptly with cycling. The improved performance of composites is ascribed to a combination of the properties of the amorphous SiOx layer, and the texture and morphological properties of carbon, increasing the electrode conductivity and buffering Si expansion and shrinkage during Li insertion and deinsertion.
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