Reversible insertion of lithium ions into carbon/carbon nanocomposite

Polyacrylonitrile (PAN) fibers were used as a precursor to prepare novel carbon materials regarded as anodes for rechargeable lithium-ion cells. For PAN fibers heat-treated at 1000°C the insertion charge of lithium ions was as high as 460 mA h/g but during the deinsertion cycle only 66% of charge could be recovered. A very high reversibility (93%) was attained for carbon/carbon nanocomposite prepared by chemical vapor deposition of thin layer of pyrolytic carbon onto carbon fibers followed by heat-treatment at 2200°C. To explain such a behaviour the cyclic galvanostatic measurements and X-ray diffraction data are discussed.