Lithium-containing composite oxide, cathode active material, positive electrode for lithium ion secondary battery, and lithium ion secondary battery

2:

• The lithium-containing composite oxide of claim 1, wherein in the formula I, 1.24≤a/(b+c+d+e)≤1.4.

3:

• The lithium-containing composite oxide of claim 2, wherein in the formula I, M is at least one member selected from the group consisting of Ti, Zr and Al.

4:

• A cathode active material, comprising:
• the lithium-containing composite oxide of claim 2.

5:

• The cathode active material of claim 4, further comprising:
• a coating comprising at least one member selected from the group consisting of Zr, Ti, Al, and F, and formed on a surface of the lithium-containing composite oxide.

6:

• The cathode active material of claim 4, wherein the cathode active material comprises a secondary particle comprising a plurality of primary particles and having a D50 value of from 3 to 10 μm.

7:

• The cathode active material of claim 4, wherein the cathode active material has a specific surface area of from 0.5 to 5 m2/g.

10:

• The lithium-containing composite oxide of claim 1, wherein in a X-ray diffraction measurement of the lithium-containing composite oxide, a peak of (020) plane assigned to a space group C2/m appears at 2θ=20 to 22 deg, and a peak of (003) plane assigned to a space group R-3m appears at 2θ=18 to 20 deg.

11:

• The lithium-containing composite oxide of claim 1,
• wherein M is at least one member selected from the group consisting of Ti, Zr, and Al, and
• in the formula I, 1.1≤a/(b+c+d+e)≤1.24 and 0≤e/(b+c+d+e)≤0.005.

12:

• A cathode active material, comprising:
• the lithium-containing composite oxide of claim 11.

13:

• The cathode active material of claim 12, further comprising:
• a coating comprising at least one member selected from the group consisting of Zr, Ti, Al, and F, and formed on a surface of the lithium-containing composite oxide.

14:

• The cathode active material of claim 12, wherein the cathode active material comprises a secondary particle comprising a plurality of primary particles and having a D50 value of from 3 to 10 μm.

15:

• The cathode active material of claim 12, wherein the cathode active material has a specific surface area of from 0.5 to 5 m2/g.

18:

• The lithium-containing composite oxide of claim 11, wherein in a X-ray diffraction measurement of the lithium-containing composite oxide, a peak of (020) plane assigned to a space group C2/m appears at 2θ=20 to 22 deg, and a peak of (003) plane assigned to a space group R-3m appears at 2θ=18 to 20 deg.