ANODE CHARACTERISTICS OF NON-GRAPHITIZABLE CARBON-FIBERS FOR RECHARGEABLE LITHIUM-ION BATTERIES

Non-graphitizable carbon fibers heat-treated between 1000 and 1200 deg rees C gave capacity higher than the capacity of LiC6 (372 mAh g(-1)) with a significant capacity below 0.1 V during oxidation. Li-7 nuclear magnetic resonance (Li-7-NMR) observation on lithium insertion into t he carbon fibers suggested that lithium in the carbons are classified into two species. One of the lithium species was the same as that in g raphitizable carbons. However, the other lithium species was quite dif ferent from that in graphitizable carbons, because the line shifts in the Li-7-NMR spectra of the carbon fibers fully lithiated to 0 V were between 80-110 ppm (versus LiCl); these shifts are larger than the max imum shift of lithium in graphitizable carbons (similar to 45 ppm). In particular, a significant capacity below 0.1 V corresponded to the fo rmation of a new lithium species. (C) 1997 Elsevier Science S.A.