| 摘要 |
PROBLEM TO BE SOLVED: To provide a carbon material for a nonaqueous solvent secondary battery negative electrode with high capacity and excellent charging/discharging cycle characteristics by carbonizing a carbon precursor having specified physical properties, obtained by heat treating pitch in the specified condition. SOLUTION: Pitch is heat treated under a non-oxidizing atmosphere to obtain a carbon precursor having an atomic ratio of hydrogen to carbon of 0.42 or less. The carbon precursor is carbonized in inert gas atmosphere at about 900 deg.C or higher, or graphitized by further heating at 2000 deg.C or higher. As the pitch used, meso-phase pitch having carbon yield of about 70% or more, a softening point of about 170 deg.C or higher, and an optical anisotropy phase content of about 70% or more is preferable. The production condition is selected so that the particle size of the final carbon material has an average particle size of 1-50μm or so, usually of 2-30μm. Since the carbon material is not melt-bonded between particles, drop in characteristics caused by oxidation of broken surface produced by breaking of primary particles is avoided. |
