Low temperature chemical synthesis of silicon nanoparticles as anode materials for lithium-ion batteries

In this study, silicon (Si) nanoparticles have been prepared by a chemical reaction of calcium silicide (CaSi₂), sulfur and metallic sodium in an autoclave at 250 °C. X-ray powder diffraction pattern indicates that the obtained sample is cubic phase Si with the calculated lattice constant a = 5.436 Å. Electron microscopy images show the obtained Si sample is composed of nanoparticles with an average size of 50 nm. As an anode for lithium ion batteries, the as-prepared Si nanoparticles exhibit a reversible capacity of 1409 mA h g⁻¹ at a current density of 2 A g⁻¹ over 300 cycles.