| 摘要 |
PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery with high initial charge/ discharge efficiency, high discharge capacity, and good high rate discharge characteristics, preventing the decomposition of propylene carbonate (PC) and increase in internal pressure caused by the decomposition of PC, without utilizing expensive treatment, using a negative electrode made from graphite powder and a nonaqueous electrolyte containing PC effective in the enhancement of low temperature output characteristics and having low coagulation temperature. SOLUTION: Hexafluorobenzene of 0.01-5.0 mass % is included in the nonaqueous electrolyte, and graphite powder having a line width of an ESR signal in a range of G value=2.002-2.012 of 2.5 mT or less when an ESR spectrum is measured at room temperature in the nonaqueous electrolyte is used. The graphite powder having a spacing of (002) planes in c axis determined by a lattice constant precision measuring method from X-ray diffraction pattern of 3.368 Å or less is preferably used. |
