| CPC H01M 4/525 (2013.01) [H01M 4/366 (2013.01); H01M 4/505 (2013.01); H01M 10/0525 (2013.01); H01M 2004/021 (2013.01); H01M 2004/028 (2013.01)] | 23 Claims |

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1. A positive electrode active material comprising:
a first lithium composite oxide; and
a second lithium composite oxide that covers at least a part of a surface of the first lithium composite oxide, wherein:
the first lithium composite oxide includes at least one selected from the group consisting of F, Cl, N, and S,
the first lithium composite oxide has a crystal structure belonging to a layered structure,
the second lithium composite oxide has a crystal structure belonging to space group Fd-3m, and
the following mathematical formula (I) is satisfied:
0.05≤Integrated intensity ratio)) I(18°-20°)/I(43°-46°)≤0.90 (I),
where the integrated intensity ratio)) I(18°-20°)/I(43°-46°) is a ratio of an integrated intensity) I(18°-20°) to an integrated intensity) I(43°-46°),
the integrated intensity) I(18°-20°) is an integrated intensity of a first peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 18° and less than or equal to 20° in an X-ray diffraction pattern of the positive electrode active material,
the integrated intensity) I 43°-46°) is an integrated intensity of a second peak that is a maximum peak present in a range of angle of diffraction 2θ greater than or equal to 43° and less than or equal to 46° in the X-ray diffraction pattern of the positive electrode active material,
the second lithium composite oxide is represented by composition formula LiaAbOc,
the second lithium composite oxide has a thickness of greater than or equal to 0.1 nanometers and less than or equal to 30 nanometers.
where
A is at least one element selected from the group consisting of Ni, Co, Mn, Si, Al, P, S, Ti, V, Cr, Fe, Cu, Zn, Ga, Zr, Nb, Mo, Ru, Ta, and W,
0<a≤2,
1.8≤b≤2.2, and
3.5≤c≤4.5, and
the first lithium composite oxide is represented by composition formula LixMeyOαQβ,
where
Me is at least one selected from the group consisting of Mn, Co, Ni, Fe, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, P, and Al,
Q is at least one selected from the group consisting of F, Cl, N, and S,
1.05≤x≤1.4,
0.6≤y≤0.95,
1.33≤α<2, and
0.1≤β≤0.67.
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