Multi-step process for making cathode active materials, and cathode active materials

1. A particulate electrode active material according to the general formula (Li a Mg b ) 1+x (TM c M 1 d ) 1−x O 2 , wherein

TM contains at least 97 mol-% Ni and, optionally, up to 1 mol-% of at least one metal selected from Ti, Al, Zr, V, Co, Zn, Ba, and Mn,

M 1 is selected from Al, Zr, Co, Mn, Nb, Ta, Mo, and W,

wherein M 1 comprises at least one of Al, Zr, Nb, Ta, Mo, and W,

a:b is in the range of from 40:1 to 200:1, and a+b=1,

c:d is in the range of from 50:1 to 250:1, and c+d=1,

total molar ratio of (Li+Mg) to (TM+M 1 ) is in the range of from 1:1 to 1.05:1,

0.00 ≤x ≤0.05;

wherein said electrode active material is comprised from secondary particles that are agglomerates of primary particles, and M 1 is enriched at the surface of the primary particles.

2. The particulate electrode active material according to claim 1 , wherein TM is nickel.

3. The particulate electrode active material according to claim 1 , wherein M 1 comprises Al, Zr or combinations thereof.

4. A process for making the particulate electrode active material according to claim 1 , wherein said process comprises the following steps:

(a) providing a hydroxide TM(OH) 2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM is one or more metals and contains at least 97 mol-% Ni and, optionally, in total up to 1 mol-% of at least one metal selected from Al, Ti, Zr, V, Co, Zn, Ba, and Mn,

(b) mixing said hydroxide TM(OH) 2 or oxide TMO or oxyhydroxide of TM or combination with a source of lithium and a source of Mg wherein the molar amount of (Li+Mg) corresponds to 75 to 95 mol-% of TM,

(c) treating the mixture obtained from step (b) thermally at a temperature in the range of from 450 to 650° C., thereby obtaining an intermediate,

(d) mixing the intermediate from step (c) with a source of Li and with at least one compound of a metal M 1 selected from Al, Zr, Co, Mn, Nb, Ta, Mo, and W, wherein M 1 comprises at least one of Al, Zr, Nb, Ta, Mo, and W, and

(e) treating the mixture obtained from step (d) thermally at a temperature in the range of from 500 to 850° C.

5. The process according to claim 4 , wherein the total molar ratio of (Li+Mg) to (TM+M 1 ) is in the range of from 1:1 to 1.05:1.

6. The process according to claim 4 , wherein in step (b), the molar ratio of Li to Mg is in the range of from 200:1 to 25:1.

7. The process according to claim 4 , wherein the source of Mg is selected from Mg(OH) 2 and MgO.

8. The process according to claim 4 , wherein in step (b), a source of Al is added.

9. The process according to claim 4 , wherein the temperature in step (e) is higher than in step (c).

10. The process according to claim 4 , wherein steps (c) and (e) are performed in an atmosphere of at least 80 vol-% oxygen.

11. The process according to claim 4 , wherein the molar ratio of M 1 to TM is in the range of from 1:50 to 1:250.

12. The process according to claim 4 , wherein the at least one compound of a metal M 1 is selected from the group consisting of oxides of M 1 , hydroxides of M 1 , and oxyhydroxides of M 1 .

13. A cathode containing

(A) at least one electrode active material according to claim 1 ,

(B) carbon in electrically conductive form, and

(C) a binder material.

14. The cathode according to claim 13 containing

(A) 80 to 98% by weight cathode active material,

(B) 1 to 17% by weight of carbon, and

(C) 3 to 10% by weight of binder material,

percentages referring to the sum of (A), (B) and (C).

15. An electrochemical cell containing at least one cathode according to claim 13 .