Surface-modification of anode carbon for lithium-ion battery using chemical vapor infiltration technique

To reduce the high irreversible capacity of the low crystalline carbon fiber for the anode material of lithium-ion battery, pyrolytic carbon (pyrocarbon) was coated at 950 °C from C3H8(30%)–H2 gas system using pressure-pulsed chemical vapor infiltration. Carbon fiber was coated with the dense pyrocarbon film having the laminar texture and the low surface area of 1.9 m2 g−1. It was revealed from XRD and Raman spectroscopy that the crystallinity of pyrocarbon is higher than that of the core carbon. Electrochemical properties were measured in ethylene carbonate (EC) and propylene carbonate (PC) base electrolytes. Irreversible capacity was reduced in EC-based electrolyte by coating with 8 mass% pyrocarbon, which would be attributed to the high crystallinity, laminar structure and low surface area of pyrocarbon. Irreversible capacity was also decreased in PC-based electrolyte. The crystallinity of pyrocarbon was not so high as PC-based electrolyte was decomposed in the case of the high crystalline graphite.