Lithium-containing composite oxide and process for its production
A lithium-containing composite oxide essentially containing Li, Ni, Co and Mn, which has a crystal structure with space group R-3m, with a c-axis lattice constant being from 14.208 to 14.228 Å, and with an a-axis lattice constant and the c-axis lattice constant satisfying the relation of 3a+5.615≤c≤3a+5.655, and of which the integrated intensity ratio (I 003 /I 104 ) of the (003) peak to the (104) peak in an XRD pattern is from 1.21 to 1.39.
1. A lithium-containing composite oxide, which is a compound represented by Formula 1:
Li p Ni x Co y Mn z Me g O r F s Formula 1
wherein 1.01≤p≤1.1, 0.414≤x≤0.5, 0.24≤y≤0.35, 0.17≤z≤0.25, 0≤q≤0.01, 0.9≤x+y+z+q≤1.05, 1.9≤r≤2.1, 0≤s≤0.03, and Me is at least one member selected from the group consisting of Mg, Ca, Sr, Ba, Al and Zr,
which has a crystal structure with space group R-3m,
with a c-axis lattice constant being from 14.208 to 14.228 Å, and
with an a-axis lattice constant and the c-axis lattice constant satisfying the relation of 3a+5.615≤c≤3a+5.655, and
of which the integrated intensity ratio (I 003 /I 104 ) of the (003) peak to the (104) peak in an XRD pattern is from 1.21 to 1.39.
2. The lithium-containing composite oxide according to claim 1 , wherein the (110) crystallite size in an XRD pattern is from 400 to 760 Å.
3. The lithium-containing composite oxide according to claim 1 , wherein the average particle size D 50 is from 0.1 to 30 μm.
4. The lithium-containing composite oxide according to claim 1 , wherein the following R-factor is from 0.37 to 0.44:
R-factor: a value calculated in accordance with the Formula 2 from the integrated intensities (I 102 , I 006 and I 101 ) of the (102), (006) and (101) peaks in an XRD pattern:
R -factor=( I 102 +I 006 )/ I 101 Formula 2.
5. The lithium-containing composite oxide according to claim 1 , wherein the (003) crystallite size in an XRD pattern is from 700 to 1,200 Å.
6. A process for producing the lithium-containing composite oxide as defined in claim 1 , which comprises
mixing a composite compound comprising Ni, Co and Mn with a lithium compound, and
firing the obtained mixture in an oxygen-containing atmosphere.
7. The process for producing the lithium-containing composite oxide according to claim 6 , wherein the composite compound is a hydroxide comprising Ni, Co and Mn, and the (100) crystallite size of the hydroxide in an XRD pattern is from 130 to 300 Å.
8. A positive electrode, which comprises the lithium-containing composite oxide according to claim 1 , a binder and an electrically conductive material.
9. A lithium ion secondary battery, which comprises the positive electrode according to claim 8 , a separator, a negative electrode and a non-aqueous electrolyte.