MODIFIED NATURAL GRAPHITE PARTICLES

A modified natural graphite material which provides a negative plate having improved adhesion between a negative electrode mixture and a current collector has a circularity of at least 0.92 and at most 1.0 and an incident angle dependence S 60/0 of the peak intensity ratio of at least 0.5 and at most 0.7 as determined by measurement of C K-edge X-ray absorption spectra using synchrotron radiation as an excitation source. It preferably satisfies at least one of the following conditions: an absolute specific gravity of at least 2.25 (g/cm 3 ), a tap density of at least 1.0 g/cm 3 and at most 1.4 g/cm 3 , and linseed oil absorption of at least 20 cm 3 /100 g and at most 50 cm 3 /100 g. A carbonaceous material may adhere to at least a portion of the surface of the graphite particles.