Natural graphite coated by Si nanoparticles as anode materials for lithium ion batteries

Nano-sized crystalline silicon particles, prepared by a laser-induced vapour deposition method, were coated onto the surface of particles of a modified natural graphite ( SSG) by sonicated dispersion and a subsequent heat-treatment process. The microstructure of the Si-coated SSG was characterized by X-ray diffraction ( XRD) and scanning electron microscopy ( SEM). It was found that the nanometer-scale Si particles were uniformly and completely coated on the surface of SSG particles, and both the Si and SSG particles existed in the crystalline state. The Si-coated SSG exhibits a much higher reversible capacity than pristine SSG, while keeping the good cycling performance of SSG material. The higher capacity can be ascribed to the alloying of Si with lithium. Because of the heat-treatment at 600 degrees C, used to achieve a good combination of Si with the SSG base, the cycling of the composites is very satisfactory. As a result, Si-coated SSG is a promising anode material for lithium ion batteries.