Lithium-transition metal composite oxide

1. A lithium-transition metal composite oxide which comprises particles of a lithium composite oxide represented by the formula Li x M 1−y N y O 2 , wherein 0.2≦x≦1.2, 0≦y≦0.7, M is a transition metal element, and N is a transition metal element other than M or an alkaline earth metal element, wherein in the distribution curve of the cumulative volume particle size of said lithium composite oxide, the inclination of the curve at a cumulative volume fraction of 20% is at most 9%/μm, the inclination of the curve at a cumulative volume fraction of 80% is at least 3%/μm, and the average particle size is from 3 to 20 μm.

2. The lithium-transition metal composite oxide according to claim 1 , wherein the cumulative volume fraction of particles having particle sizes of less than 1 μm, is at most 0.1%, and the cumulative volume fraction of particles having particle sizes of more than 40 μm, is at most 0.5%.

3. The lithium-transition metal composite according to claim 1 or claim 2 , wherein the volume base cumulative 5% size is at least 2 μm, and the volume base cumulative 95% size is at most 30 μm.

4. The lithium-transition metal composite according to claim 1 or claim 2 , wherein the inclination of the curve at a cumulative volume fraction of 20% is at most 7.5%/μm, the inclination of the curve at a cumulative volume fraction of 80% is at least 4.5%/μm, the volume fraction of particles having particle sizes of less than 1 μm is at most 0.01%, the volume fraction of particles having particle sizes of more than 40 μm is at most 0.1%, the volume base cumulative 5% size is at least 3 μm, and the volume base cumulative 95% size is at most 20 μm.

5. The lithium-transition metal composite oxide according to claim 1 , wherein after the lithium-transition metal composite oxide powder is pressed under a pressure of 0.3t/cm 2 , the volume fraction of particles having particle sizes of less than 1 μm, is at most 0.1%.

6. The lithium-transition metal composite oxide according to claim 1 , wherein M is Co.

7. The lithium-transition metal composite oxide according to claim 1 , wherein M is Co, the half width of the diffraction peak for (110) face at 2θ=66.5±1°, is from 0.070 to 0.110° as measured by the X-ray diffraction using CuK α as a ray source, and y is 0.

8. The lithium-transition metal composite oxide according to claim 1 , wherein M is Co, the half width of the diffraction peak for (110) face at 2θ=66.5±1°, is from 0.080 to 0.180° as measured by the X-ray diffraction using CuK α as a ray source, N is at least one member selected from the group consisting of Ti, Zr, Hf, V, Nb and Ta, and y is 0.0005≦y≦0.02.

9. The lithium-transition metal composite oxide according to claim 1 , wherein M is Ni.

10. The lithium-transition metal composite oxide according to claim 1 , wherein M is Ni, N is Co, 0.1≦y≦0.4, and the half width of the diffraction peak for (110) face at 2θ=65±1° or its vicinity, is from 0.13 to 0.20°, as measured by the X-ray diffraction using CuK α as a ray source.

11. The lithium-transition metal composite oxide according to claim 1 , wherein M is Ni, N is Mn, and 0.4≦y≦0.6.

12. The lithium-transition metal composite oxide according to claim 1 , wherein M is Ni, N comprises Co and Mn, 0.4≦y≦0.7, and the atomic ratio of Co/Mn is from 1/4 to 4/1.

13. The lithium-transition metal composite oxide according to claim 1 , wherein M is Ni, N comprises Co and, Al or Mn, 0.1≦y≦0.4 and the atomic ratio of Co/(Al or Mn) is from 1/4 to 4/1.

14. A positive electrode for a lithium secondary cell, employing the lithium-transition metal composite oxide as defined in claim 1 , as a positive electrode active material.

15. A lithium secondary cell having the positive electrode as defined in claim 14 .