Patent ID: 8916295

Claim:
A positive electrode active material for a lithium ion secondary battery, comprising a compound represented by the following composition formula: [Li 1.5 ][Li 0.5(1-x) Mn 1-x M 1.5x ]O 3 (wherein x satisfies 0.15 ≦x ≦0.30 , and M is represented by Ni α Co β Mn γ in which α, βand γ satisfy 0 <α≦0.5, 0 ≦β≦0.33 and 0 <γ≦0.5, respectively), wherein a half width of a peak of a (001) crystal plane of the compound measured by X-ray diffraction is in a range from 0.19 to 0.212 inclusive, and an average primary particle diameter of the compound is in a range from 0.19 μm to 0.25 μm inclusive.