Structure of carbonized paper coated with pyrolytic carbon and its anode property for lithium-ion battery

Using pressure-pulsed chemical vapor infiltration (PCVI) technique, pyrolytic carbon (pyrocarbon) was infiltrated at 950°C from C3H8 (30%)-H2 gas system into the carbonized paper substrate. Carbon fibers in the carbonized paper were coated with dense pyrocarbon films having a laminar texture oriented parallel to the surface of carbonized fibers. It was revealed from XRD and Raman spectroscopy that the crystallinity of pyrocarbon was higher than that of carbonized fiber. BET surface area was decreased from 210 m2g-1 of the original substrate to 1.9 m2 g-1 of the pyrocarbon-coated sample.Reversible capacity of the sample coated with 8 mass % pyrocarbon was 500 mA h g-1, which were nearly close to that of the original carbonized paper. High irreversible capacity of 180 mA h g-1 was observed in the original carbonized paper, reflecting the disordered structure and high surface area. Irreversible capacity was reduced to 100 mA h g-1 by coating with 8 mass % pyrocarbon, which would be attributed to high crystallinity, laminar structure and low surface area of pyrocar-bon. Irreversible capacity was further decreased with increasing the mass fraction of pyrocarbon, however, reversible capacity was also decreased.