Anodic performances of anisotropic carbon derived from isotropic quinolinepitch

The anodic performances of anisotropic carbon derived from quinoline pitch (CQP) to be used in the lithium ion battery were studied to clarify the inf luence of nitrogen in the carbon hexagonal sheet. The quinoline pitch was s ynthesized by using HF/BF3 as a catalyst. Nitrogen in the carbon existed as pyridinic, pyrrolic and quaternary types to be converted in this sequence, depending upon HTT. Above 1000 degrees C. nitrogen started to evolve, leav ing vacancies in the sheer which were filled by graphitization at higher HT T. CQP prepared below 700 degrees C showed much lower discharge capacity th an that derived from naphthalene pitch (CNP) at the same temperature. Highe r temperature treatment reduced the capacity as observed commonly in the an isotropic carbon, however, the extent of reduction was smaller. Hence, the capacity became the same at 800 degrees C and larger at 1000 and 1200 degre es C than those of CNP. The capacity of CQP after the heat-treatment at 100 0 degrees C, where the cycle stability was acceptable was 320 mAh g(-1). Th e nitrogen in the ring disturbs the growth and stacking of hexagonal sheets by the carbonization below 700 degrees C to reduce the capacity of CQP, wh ereas the vacancies due to nitrogen evolution by the heat-treatment at 1000 degrees C appeared to provide new type sites for lithium charge. Such site s gave potentials of charge and discharge at 0.5-1.0 V reversibly and capac ity of 468 mAh g(-1). Higher temperature may remove such sites by graphitiz ation. (C) 1999 Elsevier Science Ltd. All rights reserved.