| abstract |
In a lithium ion secondary battery, cycle characteristics when an intermittent cycle is repeated are improved as compared with the related art. In a lithium ion secondary battery, a positive electrode includes active material particles made of a lithium composite oxide, and the lithium composite oxide has a general formula (1): Li x M 1-y L y O 2 (0.85). ≦ x ≦ 1.25, 0 ≦ y ≦ 0.50, element M is at least one selected from the group consisting of Ni and Co, element L is an alkaline earth element, transition metal element, rare earth element, IIIb At least one selected from the group consisting of group elements and group IVb elements), and the surface layer portion of the active material particles is selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W and Y The active material particles containing at least one selected element Le are surface-treated with a coupling agent. [Selection] Figure 1 |