Carbon fiber structures for use as lithium-ion secondary cell anode material

摘要

Carbon fiber capable of carrying out doping/undoping of lithium and having cross sectional shape which satisfies area replenishment rate of 0.8 or more is used as anode material for non-aqueous electrolyte secondary battery. Alternatively, since value of fractal dimension of cross section high order structure of the random radial type carbon fiber can be utilized as material parameter for evaluating the cross sectional structure, carbon fiber in which the value of the fractal dimension is caused to fall within the range from 1.1 to 1.8 and the crystallinity has been controlled such that it falls within reasonable range is used as anode material for non-aqueous electrolyte secondary battery. Further, carbon fiber having cross section high order structure such that the central portion is radial type structure and the surface layer portion is random radial type structure is used as anode material for non-aqueous electrolyte secondary battery. Furthermore, it is also effective to use carbon fiber having notch structure at the cross section. In addition, graphitized carbon fiber having cross sectional portions different in the crystal structure at predetermined periods in the fiber length direction is made up. By crushing the graphitized carbon fiber thus obtained, carbon fiber crushed powder having less unevenness and predetermined aspect ratio can be easily made up.