| 摘要 |
PROBLEM TO BE SOLVED: To increase charging/discharging capacity and cycle characteristics by using carbon material having the specified crystal structure in the X-ray diffraction, obtained by graphitizing treatment in the existence of boron, and containing the specified amount of boron, in a negative electrode. SOLUTION: The spacing between graphite layers measured by X-ray diffraction of a carbon material whose graphitizing treatment is performed in the existence of a boron compound is 0.338nm or less, and the size of a crystallite in the direction of the (c) axis is 35nm or more and that in the direction of the (a) axis is 50nm or more, and the ratio of diffraction peak of (101) plane to the diffraction peak of (100) plane P101 /P100 is 1.0 or more, and the content of boron is 1000-30000ppm. Preferably, carbon fibers prepared by using meso- phase pitch as a raw material are milled, then graphitized. Preferably, the pitch raw material is spun and is made nonfusible, and if necessary slightly carbonized at 1500 deg.C or lower, then milled, and graphitized at 2200 deg.C or higher after a boron compound is added. The carbon material is highly graphitized. |
