Pyrocarbon-coating on powdery hard-carbon using chemical vapor infiltration and its electrochemical characteristics

Using the pressure-pulsed chemical vapor infiltration technique, thin pyrocarbon films were coated on the surface of the hard-carbon particles. The crystallinity of pyrocarbon shell was higher than that of the core carbon. The BET surface area and the pores with the diameter of 1.5-5 nm were extremely decreased after coating with 7 wt.% pyrocarbon. These changes in the nano-scaled structure of carbon surface could lead to the reduction of irreversible capacity. The cycleability was improved by pyrocarbon-coating, which would be attributed to the increase of the surface roughness on sub-micron scale by coating with the pebble-like pyrocarbon film to increase the adhesion among the particles by the organic binders.