Characteristics of graphite anode modified by CVD carbon coating

Graphite particles modified with carbon film coating were prepared by a CVD method. Surface characteristics of carbon-coated graphite were analyzed by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). Carbon film was uniformly coated on the graphite surface. Raman, HRTEM, and EELS studies indicated that the structures of the carbon coatings were disordered. Specific surface area of the graphite particles was decreased by carbon coating. Graphite particles coated with carbon were used as anode materials for Li-ion batteries and tested the charge/discharge ability. Uncoated graphite can only achieve 260 mAh/g specific capacity. After disordered carbon was coated onto graphite, the discharge capacity showed an increase up to 300 mAh/g. The anode can achieve a stable discharge capacity and excellent coulombic efficiency after about 60 cycles at 300 mAh/g specific capacity cutoff, and maintain a capacity cutoff of 350 mAh/g capacity without fading after another 30 cycles at a capacity cutoff of 350 mAh/g. The improvements on capacity and cyclability were due to suppression of electrolyte decomposition by the disordered carbon coated on the graphite.