NEGATIVE ELECTRODE OF LITHIUM ION SECONDARY BATTERY AND LITHIUM ION SECONDARY BATTERY

摘要

PROBLEM TO BE SOLVED: To provide a negative electrode of a lithium ion secondary battery whose life can be prolonged with keeping a high initial coulomb efficiency specific to cylindrical graphite carbon fiber, and to provide a lithium ion secondary battery using the same. SOLUTION: The negative electrode of a lithium ion secondary battery in relation to the invention mainly comprises a composite body wherein cylindrical graphite carbon fiber is mixed with scale-like graphite powder. A ratio of the scale-like graphite powder in the mixed composite is from 20 to 50 weight percentages, granular diameter thereof is from 0.1 to 30 μm, and granular diameter of the cylindrical graphite carbon fiber is from 5 to 50 μm. In the negative electrode in relation to the invention, inner stress accompanied by compression and shrink caused by repetitive use can be dispersed owing to the existence of both cylindrical graphite carbon fiber and the scale-like graphite powder so that the negative electrode is not deformed. Therefore, the lithium ion battery including the negative electrode and a positive electrode formed of an appropriate material can express excellent cyclic properties.