Production and advantages of carbon-coated graphite for the anode of lithium ion rechargeable batteries

Carbon coating of substrate graphite powder was carried out by carbonizing the mixture with poly(vinyl alcohol) at 600~1500°C. From the measurement of anode performance on the carbon-coated graphite prepared from 21 graphite substrates, crystallite thickness with three-dimensional regular stacking and BET surface area of the substrate graphite were used as parameters for the selection of the substrate graphite. The production scale of carbon-coated graphite powders was successfully increased up to about 1000 kg. Carbon-coated graphite was shown to give a smaller irreversible capacity for the first charge/discharge cycle than graphite without a carbon coating and could be used in an electrolyte solution containing a small amount of propylene carbonate (PC), of which anode performance was almost comparable with those in the solutions without PC. With a high discharge rate of about 10 mA/cm2, carbon-coated graphite gave better anode performance, larger discharge and smaller irreversible capacities, than the graphite without a carbon coating.