PROCESS FOR PREPARING LITHIUM TRANSITION METAL OXIDES
A process for producing a lithium transition metal oxide is provided. The process comprises pre-calcination of a transition metal precursor in the absence of a lithium source followed by a high-temperature calcination of the pre-calcined intermediate compound in the presence of a lithium source.
1 . A process for preparing a lithium transition metal oxide, the process comprising:
(a) pre-calcination of a transition metal precursor in the absence of a lithium source to form a pre-calcined intermediate compound, the transition metal precursor comprising nickel, cobalt and magnesium; followed by
(b) high-temperature calcination of the pre-calcined intermediate compound in the presence of a lithium source.
2 . The process according to claim 1 wherein the pre-calcination process includes a heating stage during which the temperature is increased and a hold phase during which the temperature is maintained at an elevated level, and wherein the hold phase of the pre-calcination is performed at a temperature in the range from 275° C. to 600° C. for between 1 and 4 hours.
3 . The process according claim 1 , wherein the pre-calcination is carried out at a temperature in the range from 300° C. to 500° C. for a period of 1 to 3 hours.
4 . The process according to claim 1 , wherein the pre-calcination step is carried out in a rotary furnace.
5 . The process according to claim 1 , wherein the high-temperature calcination includes a heating stage during which the temperature is increased and a hold phase during which the temperature is maintained at an elevated level, and wherein the hold phase of the high-temperature calcination is performed at a temperature in the range from 600° C. to 1000° C. for between 4 and 10 hours.
6 . The process according to claim 1 , wherein the high-temperature calcination is carried out at a temperature in the range from 600° C. to 800° C. for a period of 5 to 7 hours.
7 . The process according to claim 1 , wherein during the heating phase of the high-temperature calcination process the temperature is increased at a rate of 4° C./min or less.
8 . The process according to claim 1 , wherein in step (b) the pre-calcined intermediate is calcined in the presence of lithium hydroxide and/or lithium carbonate.
9 . The process according to claim 1 , wherein the lithium transition metal oxide does not contain manganese or contains less than 10 mol % of manganese with respect to the total moles of transition metal in the lithium transition metal oxide.
10 . The process according to claim 1 , wherein the transition metal precursor is a transition metal hydroxide, a transition metal oxyhydroxide, or a mixture thereof.
11 . The process according to claim 1 , wherein the transition metal precursor comprises Ni, Co and optionally one or more transition metals selected from Ti, Zr, Mn and Zn.
12 . The process according to claim 1 , wherein the transition metal precursor comprises one or more additional metals selected from group 1, 2 or 13 metals.
13 . The process according to claim 1 , wherein the mixed transition metal precursor comprises a mixed transition metal compound according to the formula:
Ni x Co y TM w M z O a (OH) b
wherein:
0.65≤x≤1.0
0<y≤0.4
0<z≤0.1
0≤w≤0.3
0≤a≤0.1
1.7≤b≤2.0
wherein TM is one or more transition metals selected from Mn, Ti, Zr and Zn, and
wherein M is Mg and optionally one or more metals selected from Na, K, Ca and Al.
14 . The process according to claim 1 , wherein the lithium transition metal oxide has the layered α-NaFeO 2 -type structure.
15 . The process according to claim 1 , wherein the lithium transition metal oxide has a composition according to the formula:
Li c Ni x Co y TM w M z O 2±d
wherein:
0.6≤x≤1.0
0<y≤0.4
0<z≤0.1
0≤w≤0.1
0.9≤c≤1.1
−0.2≤d≤0.2
wherein TM is one or more metals selected from Mn, Ti, Zr and Zn, and
wherein
M is Mg and optionally one or more selected from Na, K, Ca and Al.
16 . The process according to claim 1 , wherein a coating step is carried out on the lithium transition metal oxide material obtained from the high-temperature calcination.
17 . The process according to claim 1 , wherein the process further comprises the step of forming an electrode comprising the lithium transition metal oxide material.
18 . The process according to claim 17 , wherein the process further comprises constructing an electrochemical cell including the electrode comprising the lithium transition metal oxide material.