Synthesis of Si/SiOx from talc and its characteristics as an anode for lithium ion batteries

A mixture of silicon (Si) and silicon suboxide (SiOx < 2) phases is prepared from talc by magnesio-thermal reduction and acid etching processes. Talc is a clay mineral composed of hydrated magnesium silicate and is one of the most abundant minerals on earth. The reduced Si/SiOx nanoparticles are found to be porous after acid etching and are closely connected. The Si/SiOx particles are supported on a carbon layer which imparts them with electronic conductivity and improved durability towards stresses associated with the volume change of Si/SiOx during cycling. The structural, physical, and electrochemical properties of these electrodes are analyzed through X-ray diffraction, scanning electron microscopy, Fourier transform-infrared spectroscopy, transmission electron microscopy, thermogravimetric analysis, electrochemical impedance spectroscopy and galvanostactic charge-discharge tests. The initial discharge capacity of the carbon-coated Si/SiOx obtained from talc is measured to be 842 mAh/g at 1 C (1500 mA/g) which decreases to 470 mAh/g after 300 cycles, showing a much higher capacity retention (similar to 55.8%) than pure Si nanoparticles. This superior cycling stability may be attributed to the porous network structure of the magnesio-thermally reduced Si/SiOx and its endurance towards volume changes during cycling.