A new room temperature and solvent free carbon coating procedure for battery electrode materials

Carbon coating on battery electrode active material powders is a common practice in order to improve their electronic conductivity and the battery calendar life by limiting side reactions (i.e. active material surface degradation and electrolyte decomposition). Such a coating is currently achieved through chemical procedures involving dispersing the powder in a liquid medium with a carbon precursor followed by thermolysis at high temperatures (ca. 700 degrees C). This energy consuming procedure has the drawback of not being applicable to materials which may decompose or reduce under such conditions. We present herein an alternative procedure based on physical deposition of carbon, carried out at room temperature under dry conditions, hence avoiding the limitations mentioned above and being generally applicable to any electrode active material. Moreover it allows easy achievement of a homogeneous conformal coating with fine control of the coating thickness. Results on selected materials are reported to exemplify the wide application spectrum and performance improvements induced by the coating.