GRAPHITE MATERIAL FOR A LITHIUM ION SECONDARY CELL NEGATIVE ELECTRODE, METHOD OF MANUFACTURING SAME, AND LITHIUM ION SECONDARY CELL

摘要

Provided is a graphite material for the negative electrode of a lithium ion secondary cell, the material capable of suppressing capacity degradation in association with repeated charge/discharge cycles, storage in a charged state, floating discharge, or the like. The graphite material for the negative electrode of a lithium ion secondary cell is characterized in that the size Lc (112) of a crystal in the c-axis direction as calculated from the diffraction line (112) measured by powder X-ray diffractometry is 4.0-30 nm; the carbon spectrum measured using the X band and expressed by electron spin resonance spectroscopy is in the range of 3,200-3,400 gauss (G); the relative signal strength ratio (I4.8K/I40K) of the signal strength (I4.8K) of the spectrum measured at a temperature of 4.8K to the signal strength (I40K) of the spectrum measured at a temperature of 40K is 1.5-3.0; and the line width ?Hpp of the spectrum calculated from a primary derivative spectrum at a temperature of 4.8K is 20-40 gauss (G).