Lithium secondary battery with a negative electrode of heat-treated natural graphite

摘要

A lithium secondary battery comprises a natural graphite as a negative electrode capable of occluding and discharging lithium ion, in which the natural graphite has been heat treated at a temperature of from 2,400-3,000° C. The heat treatment removes impurities from natural graphite. As a result, the electrolyte solution used for the battery hardly decomposes during charge and discharge and self discharge hardly occurs during storage of the battery.