GRAPHITE POWDERS SUITED FOR NEGATIVE ELECTRODE MATERIAL OF LITHIUM ION SECONDARY BATTERY

摘要

A graphite powder suitable for a negative electrode material of a lithium ion secondary battery which assures a high discharging capacity not lower than 320 mAh/g is to be manufactured at a lower cost. Specifically, a graphite powder containing 0.01 to 5.0 wt% of boron and having a looped closure structure at an end of a graphite c-planar layer on the surface of a powder, with the density of the interstitial planar sections between neighboring closure structures being not less than 100/.mu.m and not more than 1500/.mu.m, and with d002 being preferably not larger than 3.3650 .ANG., is manufactured by (1) heat-treating a carbon material pulverized at an elevated speed before or after carbonization for graphization at temperature exceeding 1500 .degree. C or by (2) heat-treating the carbon material pulverized before or after carbonization at a temperature exceeding 1500 .degree. C for graphization and subsequently further heat-treating the graphized material at a temperature exceeding a temperature of the oxidating heat treatment and the heat treatment in the inert gas.