| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery having excellent room temperature cycle characteristics and high temperature cycle characteristics even when high charge end voltage is applied to obtain high capacity. <P>SOLUTION: The lithium ion secondary battery includes a positive electrode 2 having a lithium composite oxide, a negative electrode 3, a separator 4 interposed between the positive electrode 2 and negative electrode 3 and having porous polyolefin, and a nonaqueous electrolyte. Open circuit voltage in the full charge state of a pair of positive electrode and negative electrode is within a range of 4.25-4.55 V. The positive electrode 2 contains a positive active material covering the surface of lithium cobaltate with an oxide of nickel and/or manganese, and the electrolyte contains 4-fluoroethylene carbonate and a vinylene carbonate. The negative electrode 3 has a negative mix layer, the volume density of the negative mix layer is 1.65-1.85 g/ml, and its thickness is within a range of 160-220 μm in total of both surfaces. <P>COPYRIGHT: (C)2009,JPO&INPIT |
