Lithium-containing composite oxide, cathode active material, positive electrode for lithium ion secondary battery, and lithium ion secondary battery
To provide a lithium-containing composite oxide capable of obtaining a lithium ion secondary battery having a large discharge capacity wherein the deterioration of the discharge voltage due to repetition of a charge and discharge cycle is suppressed, a cathode active material, a positive electrode for a lithium ion secondary battery and a lithium ion secondary battery. A lithium-containing composite oxide, which is represented by the formula I: Li a i Ni b Co c Mn d M e O 2 Formula I, wherein M is at least one member selected from the group consisting of Na, Mg, Ti, Zr, Al, W and Mo, a+b+c+d+e=2, 1.1≤a/(b+c+d+e)≤1.4, 0.2≤b/(b+c+d+e)≤0.5, 0≤c/(b+c+d+e)≤0.25, 0.3≤d/(b+c+d+e)≤0.6, and 0≤e/(b+c+d+e)≤0.1, and wherein the valence of Ni is from 2.15 to 2.45.
1. A lithium-containing composite oxide, which is represented by the formula I:
Li a Ni b Co c Mn d M e O 2 (I),
wherein M is at least one member selected from the group consisting of Ti, Zr, and Al,
a+b+c+d+e= 2,
1.1≤ a /( b+c+d+e )≤1.24,
0.2≤ b /( b+c+d+e )≤0.5,
0≤ c /( b+c+d+e )≤0.25,
0.3≤ d /( b+c+d+e )≤0.6, and
0.005≤ e /( b+c+d+e )≤0.1, and
wherein a valence of Ni is from 2.15 to 2.45, a valence of Li is 1, a valence of Co is 3, a valence of Mn is 4, a valence of Ti is 4, a valence of Zr is 4, a valence of Al is 3, and a valence of oxygen (O) is −2, and
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.
2. The lithium-containing composite oxide of claim 1 , wherein in the formula I, 0.05≤c/(b+c+d+e)≤0.25.
3. A cathode active material, comprising:
the lithium-containing composite oxide of claim 1 .
4. The cathode active material of claim 3 , 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.
5. The cathode active material of claim 3 , wherein the cathode active material comprises a secondary particle comprising a plurality of primary particles and having a D 50 value of from 3 to 10 μm.
6. The cathode active material of claim 3 , wherein the cathode active material has a specific surface area of from 0.5 to 5 m 2 /g.
7. A positive electrode for a lithium ion secondary battery, comprising:
the cathode active material of claim 3 ;
an electrically conductive material; and
a binder.
8. A lithium ion secondary battery, comprising:
the positive electrode for a lithium ion secondary battery of claim 7 ;
a negative electrode; and
a non-aqueous electrolyte.
9. The lithium-containing composite oxide of claim 1 , wherein the valence of Ni is from 2.15 to 2.4.
10. The lithium-containing composite oxide of claim 1 , wherein the valence of Ni is from 2.15 to 2.35.
11. The positive electrode of claim 7 , wherein the electrically conductive material comprises at least one selected from the group consisting of graphite, a vapor-grown carbon fiber, and a carbon nanotube.
12. The lithium-containing composite oxide of claim 1 , wherein in the formula I, M is Ti.
13. The lithium-containing composite oxide of claim 1 , wherein in the formula I, M is Zr.
14. The lithium-containing composite oxide of claim 1 , wherein in the formula I, M is Al.
15. The lithium-containing composite oxide of claim 1 , wherein in the formula I, 1.13≤a/(b+c+d+e)≤1.20.
16. The lithium-containing composite oxide of claim 1 , wherein in the formula I, 0.25≤b/(b+c+d+e)≤0.5.
17. The lithium-containing composite oxide of claim 1 , wherein in the formula I, 0.05≤c/(b+c+d+e)≤0.20.
18. The lithium-containing composite oxide of claim 1 , wherein in the formula I, 0.35≤d/(b+c+d+e)≤0.57.
19. The lithium-containing composite oxide of claim 1 , wherein in the formula I, 0.005≤e/(b+c+d+e)≤0.05.
20. The lithium-containing composite oxide of claim 1 , wherein in the formula I,
1.13≤ a /( b+c+d+e )≤1.20,
0.25≤ b /( b+c+d+e )≤0.5,
0.05≤ c /( b+c+d+e )≤0.20,
0.35≤ d /( b+c+d+e )≤0.57, and
0.005≤ e /( b+c+d+e )≤0.05.