Lithium cobalt metal oxide powder, method for making the same, and method for determining content of cobalt (II,III) oxide

1. A lithium cobalt metal oxide powder having a coating structure, wherein the lithium cobalt metal oxide powder comprises a lithium cobalt metal oxide matrix and a Co 3 O 4 coating layer, a general formula of the lithium cobalt metal oxide powder is Li a Co 1-x-y M x N y O 2 ·rCo 3 O 4 , wherein 0.002<r≤0.05, 1≤a≤1.1, 0<x≤0.02, 0≤y≤0.005, and a<1+3r, M is a doping element, and N is a coating element.

2. The lithium cobalt metal oxide powder of claim 1 , wherein a molar ratio θ 1 of Li to Co+M+N satisfies: 0.92≤θ 1 <1.

3. The lithium cobalt metal oxide powder of claim 1 wherein Co 3 O 4 is presented both in an interior and on an outer surface of the lithium cobalt metal oxide matrix, and a mass ratio of the Co 3 O 4 in the interior of the lithium cobalt metal oxide matrix to the Co 3 O 4 on the outer surface of the lithium cobalt metal oxide matrix is smaller than 1.

4. The lithium cobalt metal oxide powder of claim 1 wherein M is selected from the group consisting of Mg, Ca, Cu, Al, B, Ti, Y, Zr, any combination thereof; and N is selected from the group consisting of Na, K, Mg, Ca, Cu, Al, B, Ti, Y, Zr, Ni, Mn, and any combination thereof.

5. The lithium cobalt metal oxide powder of claim 4 , wherein M is selected from the group consisting of Mg, Al, and any combination thereof and N is selected from the group consisting of of Mg, Ti, and any combination thereof.

6. The lithium cobalt metal oxide powder of claim 1 wherein the Co 3 O 4 is in a form of spinel phase Co 3 O 4 , and an amount of residual Li on the outer surface of the lithium cobalt metal oxide matrix is smaller than or equal to 0.05%.

7. A method for making the lithium cobalt metal oxide powder of claim 1 , comprising steps of:

(1) mixing uniformly and then sintering a Li-containing precursor, a first Co-containing precursor, and a M-containing precursor to obtain a lithium-rich matrix; and

(2) if the lithium cobalt metal oxide powder comprises the coating element N, mixing uniformly and then sintering the lithium-rich matrix obtained from the step (1), a second Co-containing precursor, and a N-containing precursor to obtain the lithium cobalt metal oxide powder;

if the lithium cobalt metal oxide powder comprises no coating element N, mixing uniformly and then sintering the lithium-rich matrix obtained from the step (1) and a second Co-containing precursor to obtain the lithium cobalt metal oxide powder.

8. The method of claim 7 , wherein in the step (2), the second Co-containing precursor is selected from the group consisting of Co(OH) 2 , CoCO 3 , Co 3 O 4 , and any combination thereof.

9. The method of claim 7 , wherein, in the step (1), a sintering temperature is 900° C. to 1100° C., a sintering time is 8 h to 12 h, and the sintering is performed in an air atmosphere; in the step (2), a sintering temperature is 600° C. to 1000° C., a sintering time is 6 h to 12 h, and the sintering is performed in an air atmosphere.

10. A method for determining a content of Co 3 O 4 in the lithium cobalt metal oxide powder of claim 1 , comprising steps of:

(1) adding a soaking agent and a metal ion salt solution to the lithium cobalt metal oxide powder, stirring and dissolving fully to obtain a first solution;

(2) filtering the first solution obtained from the step (1) by a filter membrane, and washing a residue on the filter membrane after the filtration is finished;

(3) adding the filter membrane along with the residue of the step (2) into a strong acid solution, peeling off the residue totally from the filter membrane into the strong acid solution, thereby obtaining a second solution containing the residue and the strong acid solution;

(4) adding a strong acid solution again into the second solution obtained from the step (3) to obtain a mixed solution, heating, evaporating, and drying the mixed solution;

(5) cooling and then diluting to a final volume, thereby obtaining a solution to be measured;

(6) measuring a content of Co in the solution obtained from the step (5) and then calculating a corresponding content of Co 3 O 4 to obtain the content of the Co 3 O 4 in the sample.

11. The method of claim 10 , wherein the step (4) is repeated at least once before proceeding the step (5).

12. The method of claim 10 , wherein the soaking agent is selected from the group consisting of HCl, H 2 SO 4 , H 3 PO 4 , and any combination thereof, and at least selected from the group consisting of H 2 SO 4 , H 3 PO 4 , and any combination thereof.

13. The method of claim 10 , wherein the metal ion salt solution is selected from the group consisting of NiSO 4 , NiCl 2 , MnSO 4 , MnCl 2 , FeSO 4 , FeCl 2 , Cu 2 SO 4 , CuCl 2 , CrSO 4 , and CrCl 2 , and any combination thereof.

14. The method of claim 10 , wherein the strong acid is selected from the group consisting of nitric acid, hydrochloric acid, aqua regia, and any combination thereof, and mass concentrations of the nitric acid, the hydrochloric acid, and the aqua regia are 30% to 70%.

15. The method of claim 10 , wherein a stirring time is 0.5 h to 2 h.

16. The method of claim 15 , wherein the stirring time is 0.8 h to 1.4 h.

17. The lithium cobalt metal oxide powder of claim 1 , wherein 0<y≤0.005.

18. The lithium cobalt metal oxide powder of claim 1 , wherein the lithium cobalt metal oxide powder further comprising a hexagonal phase lithium cobalt metal oxide on the outer surface of the lithium cobalt metal oxide matrix.