Cobalt-based lithium metal oxide cathode material

1. A layered lithium metal oxide powder for a cathode material used in a rechargeable battery, with the general formula (1−x)[Li a-b A b ] 3a [Co 1-c M c ] 3b [O 2-d-e N′ e ] 6c .xLi 3 PO 4 , with 0.0001<x<0.05, 0.90<a<1.10, 0<b+c<0.1, −0.1<d<0.1 and e<0.05, wherein

the Li to Co+A+M+3P molar ratio is between 0.970 and 1.005, wherein A and M comprise one or more elements including at least one element selected from the group consisting of Mg, Ti and Al; wherein N′ comprises one or more dopants selected from the group consisting of F, S, N and P; wherein the powder comprises

a core having a layered crystal structure comprising the elements Li, Co and oxygen and having a molar ratio P to Co between 0 and less than 0.05,

a surface layer comprising a mixture of the elements Li, Co and oxygen, oxides comprising one or more elements selected from the group consisting of Mg, Ti and Al, and Li 3 PO 4 , wherein the oxides optionally further comprise one or both of Li and Co, and the mixture further comprising a plurality of ion conductive Li 3 PO 4 particles in the form of discrete particles densely attached to the core.

2. The lithium metal oxide powder of claim 1 , wherein

0.970≤[((1−x)·(a−b))+3x]/[((1−x)·(1+b))+3x]≤1.000.

3. The lithium metal oxide powder of claim 1 , wherein

0.970≤[((1−x)·(a−b))+3x]/[((1−x)·(1+b))+3x]≤0.990.

4. The lithium metal oxide powder of claim 1 , wherein Li 3 PO 4 is attached to a surface of the core in a combination of a film layer and discrete particles, thereby creating an ion-conductive electron-insulating surface layer on the core.

5. The lithium metal oxide powder of claim 1 , wherein discrete particles of the Li 3 PO 4 have a size below 5 μm.

6. The lithium metal oxide powder of claim 4 , wherein the Li 3 PO 4 present as a film layer covers at least 50% of the surface of the core.

7. The lithium metal oxide powder of claim 4 , wherein a thickness of the film layer is less than 10 nm.

8. The lithium metal oxide powder of claim 1 , wherein the Li 3 PO 4 is a crystalline compound.

9. The lithium metal oxide powder of claim 1 , wherein the Li 3 PO 4 has up to 25 at % nitrogen doping on oxygen site.

10. The lithium metal oxide powder of claim 4 , wherein a thickness of the ion-conductive electron-insulating surface layer, defined as the depth where the molar ratio of (A+M)/Co>(2·(b+c))/(1−c) mol/mol, as determined by XPS, is 1 μm or less.

11. The lithium metal oxide powder of claim 10 , wherein the thickness of the ion-conductive electron-insulating surface layer is 0.5 μm or less.

12. The lithium metal oxide powder of claim 1 , wherein A further comprises at least one element selected from the group consisting of Na, Si, S, K, Ca, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Nb, Zr, W, F and rare earth metals.

13. The lithium metal oxide powder of claim 1 , wherein M further comprises at least one element selected from the group consisting of Li, Na, Si, S, K, Ca, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Nb, Zr, W, F and rare earth metals.

14. The lithium metal oxide powder of claim 1 , wherein electronic conductivity of the powder at room temperature is below 10 −3 S/cm.

15. The lithium metal oxide powder of claim 1 , wherein the P/Co molar ratio is between 0.01 and 5 mol %.

16. The lithium metal oxide powder of claim 1 , wherein the Li/(Co+3P) molar ratio is between 0.980 and 1.020.

17. The lithium metal oxide powder of claim 1 , having a soluble base content <20 μmol/g.

18. A method for manufacturing the lithium metal oxide powder of claim 1 , comprising:

providing a first mixture of a first Co— or Co, A and M-comprising precursor powder and a first Li-comprising precursor powder, the first mixture having a Li:Co molar ratio >1.02,

sintering the first mixture in an oxygen comprising atmosphere at a temperature T1 of at least 350° C., thereby obtaining a Li-enriched lithium metal oxide compound,

providing a second Co— or Co, A and M-comprising precursor powder and a phosphate containing reagent,

mixing the Li-enriched lithium metal oxide compound, the second Co— or Co, A and M-comprising precursor powder, and the phosphate containing reagent, thereby obtaining a second mixture wherein the Li to Co+A+M+3P molar ratio is between 0.970 and 1.005, and

sintering the second mixture in an oxygen comprising atmosphere at a temperature T2 of at least 600° C.

19. A method for manufacturing the lithium metal oxide powder of claim 1 , comprising:

providing a first mixture of a first Co— or Co, A and M-comprising precursor powder, and a first Li-comprising precursor powder, the first mixture having a Li:Co molar ratio >1.02,

sintering the first mixture in an oxygen comprising atmosphere at a temperature T1 of at least 350° C., thereby obtaining a Li-enriched lithium metal oxide compound,

mixing the Li-enriched lithium metal oxide compound with phosphate and lithium containing reagents,

precipitating Li 3 PO 4 particles on the surface of the Li-enriched lithium metal oxide compound, thereby obtaining a second mixture,

providing a second Co— or Co, A and M-comprising precursor powder, and

mixing the second mixture and the second Co— or Co, A and M-comprising precursor powder, thereby obtaining a third mixture, whereby the third mixture has a Li to Co+A+M+3P molar ratio between 0.970 and 1.005, and

sintering the third mixture in an oxygen comprising atmosphere at a temperature T2 of at least 600° C.