| abstract |
An excellent lithium ion secondary battery having both high room temperature cycle characteristics and high temperature cycle characteristics even when a high end-of-charge voltage is applied to increase capacity. A 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 the negative electrode 3, and a non-aqueous electrolyte. Is provided. The open circuit voltage in a fully charged state per pair of positive electrode and negative electrode is in the range of 4.25V to 4.55V. The positive electrode 2 includes a positive electrode active material in which the surface of lithium cobaltate is coated with an oxide of nickel and / or manganese, and the electrolytic solution includes 4-fluoroethylene carbonate and vinylene carbonate. The negative electrode 3 has a negative electrode mixture layer, the negative electrode mixture layer has a volume density of 1.65 g / ml to 1.85 g / ml, and a total thickness of 160 μm to 220 μm on both sides. [Selection] Figure 1 |