Cathode active material for lithium ion secondary battery, and process for its production

2:

• The cathode active material according to claim 1, wherein the at least one metal element is at least one metal element selected from the group consisting of Al, Y, Ga, In, La, Pr, Nd, Gd, Dy, Er and Yb.

3:

• The cathode active material according to claim 1, wherein the compound (II) is Li3PO4.

4:

• The cathode active material according to claim 1, wherein the atomic ratio of the P to the at least one metal element (P/the at least one metal element) contained within 5 nm of the surface layer of the particles (III) is from 0.10 to 0.40.

5:

• The cathode active material according to claim 1, wherein the molar ratio of the at least one metal element to the lithium-containing composite oxide is from 0.001 to 0.03.

8:

• The cathode active material according to claim 1, wherein the at least one metal element in the covering layer is present in a larger amount within a range up to 30 nm from the surface of the particle (III) than at the center of the particle (III).

9:

• The cathode active material according to claim 1, wherein in formula (2-1), 1.25≤(1+x)/(y+z)≤1.75 is satisfied.

10:

• The cathode active material according to claim 1, wherein the lithium-containing composite oxide is represented by formula (2-2):
• Li(LixMnyNivCow)Op (2-2),
• wherein 0.09<x<0.3, 0.36<y<0.73, 0<v<0.32, 0<w<0.32, 1.9<p<2.1, and x+y+v+w=1.

11:

• The cathode active material according to claim 1, wherein in formula (2-1), 0.16≤x<0.3 is satisfied.

12:

• The cathode active material according to claim 18, wherein in formula (2-1), 2≤p<2.1 and q=0 are satisfied.

13:

• The cathode active material according to claim 1, wherein the compound (II) is crystalline.