GRAPHITE PARTICLE FOR LITHIUM SECONDARY BATTERY NEGATIVE ELECTRODE, NEGATIVE ELECTRODE FOR LITHIUM SECONDARY BATTERY, AND LITHIUM SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To reduce decomposition of an electrolyte to enhance discharge capac ity and safety by keeping pH of pure water of specified times having graphite particles dispersed in it in a specified range. SOLUTION: Graphite particles are dispersed in pure water of 25 times in weight and the dispersed water shows a pH of 5.2-6.1. The graphite particles have an interlayer distance d002 (0.337 nm or less) of crystal at X-ray diffraction and a crystalline size Lc in the direction of C axis is 50 nm or more. Graphite particles dispersed in water showing pH out of the above rang and showing high irreversible capacity can be improved in production in such a way that when pH is lower than the lower limit, the graphite particle are heat-treated in inert or low oxygen atmosphere at 500-1000 deg.C for ten minutes to one hour, and when higher than the upper limit, the graphite particles are heat-treated in oxidizing atmosphere at 300-500 deg.C for 1-30 minutes.