Method of preparing lithium-ion cathode particles and cathode active material formed therefrom
A method of preparing cathode particles using a co-precipitation reaction in a reactor is disclosed. A feed stream (a) containing metal cations is fed into the reactor, and a feed stream (b) containing anions is fed into the reactor, wherein a ratio of the metal cations in the feed stream (a) is continuously changed from A 1 at time t 1 to A 2 at time t 2 . The feed stream (a) and the feed stream (b) are contacted in the reactor to form precipitated precursor particles, and at least one transition metal component in the particle has a non-linear continuous concentration gradient profile over at least a portion along a thickness direction of the particle.
1. A method of preparing cathode particles using a co-precipitation reaction in a reactor, comprising:
feeding a feed stream (a) containing metal cations into the reactor, the metal cations including at least one transition metal component;
feeding a feed stream (b) containing anions into the reactor;
wherein a composition ratio of the metal cations to each other in the feed stream (a) is continuously changed from A 1 at time t 1 to A 2 at time t 2 ;
wherein the feed stream (a) and the feed stream (b) are contacted in the reactor to form precipitated precursor particles, and the at least one transition metal component in the particle has a non-linear continuous concentration gradient profile over at least a portion along a thickness direction of the particle.
2. The method of claim 1 , wherein the composition ratio of the metal cations in the feed stream (a) is fixed at Ai over the period from t 0 to t 1 , and the composition ratio of the metal cations in the feed stream (a) is fixed at A 2 over the period from t 2 to t f , wherein t 0 and t f are defined respectively as the start time and the end time of the co-precipitation reaction, wherein t 0 ≤t 1 <t 2 ≤t f .
3. The method of claim 2 , wherein t 0 =t 1 <t 2 =t f ,t 0 <t 1 <t 2 =t f , t 0 =t 1 <t 2 <t f , or t 0 <t 1 <t 2 <t f .
4. The method of claim 1 , wherein the metal cations in the feed stream (a) are selected from Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, or any combination thereof.
5. The method of claim 4 , wherein the metal cations in the feed stream (a) comprise at least two of Ni, Mn and Co.
6. The method of claim 5 , wherein at least one of the metal cations have a concentration which changes not linearly with respect to the reaction time over the period from t 1 to t 2 .
7. The method of claim 6 , wherein each of the metal cations has a concentration which changes not linearly with respect to the reaction time over the period from t 1 to t 2 .
8. The method of claim 1 , wherein the composition ratio of the metal cations in the feed stream (a) is described as Ni x Mn y Co z Me 1-x-y-z , where x+y+z≥0.9, z≤0.4, and Me is one or more additional elements, wherein the composition ratio A 1 is selected from 0.85≤x≤1, 0≤z≤0.1, and the composition ratio A 2 is selected from 0.4≤x≤0.7; 0.25≤y≤0.5.
9. The method of claim 1 , wherein the reactor is connected with a first tank containing a first transition metal solution, the first tank is connected with a second tank containing a second transition metal solution, the first transition metal solution has a metal cation ratio of A 1 , the second transition metal solution has a metal cation ratio of A 2 , the second transition metal solution in the second tank begins to feed into the first tank from time t 1 and is mixed with the first transition metal solution, the mixed transition metal solutions are fed into the reactor from the first tank over the period from t 1 to t 2 .
10. The method of claim 9 , wherein the first transition metal solution in the first tank is fed into the reactor over the period from t 0 to t 2 , the second transition metal solution in the second tank is fed into the first tank over the period from t 1 to t f , no second transition metal solution is fed into the first tank from the second tank over the period from t 0 to t 1 , a mixture of the first transition metal solution and the second transition metal solution is fed into the reactor from the first tank over the period from t 1 to t 2 , and no first transition metal solution is fed into the reactor from first tank over the period from t 2 to t f .
11. The method of claim 10 , wherein a flowrate leaving the first tank and fed into the reactor is F 1 , a flowrate leaving the second tank and fed into the first tank is F 2 , F 1 is greater than F 2 , such that all of the first transition metal solution in the first tank has been fed into the reactor at time t 2 , and the second transition metal solution in the second tank is directly fed into the reactor via the first tank over the period from t 2 to t f .
12. The method of claim 11 , wherein the first transition metal solution in the first tank has a volume V 1 at time t 1 , the second transition metal solution in the second tank has a volume V 2 at time t 1 , wherein V 1 ≥V 2 .
13. The method of claim 9 , wherein the second transition metal solution feeding into the first tank is mixed adequately with the first transition metal solution in the first tank through agitation during the period from t 1 to t 2 .
14. The method of claim 1 , wherein the reactor is connected with a first tank containing a first transition metal solution, the reactor is further connected with a second tank containing a second transition metal solution, the first transition metal solution has a metal cation ratio of A 1 , the second transition metal solution has a metal cation ratio of A 2 , the second transition metal solution in the second tank begins to feed into the reactor from time t 1 .
15. The method of claim 14 , wherein the first transition metal solution in the first tank is fed into the reactor over the period from t 0 to t 2 , the second transition metal solution in the second tank is fed into the reactor over the period from t 1 to t f , no second transition metal solution is fed into the reactor from the second tank over the period from t 0 to t 1 , the first transition metal solution in the first tank and the second transition metal solution in the second tank are concurrently fed into the reactor over the period from t 1 to t 2 , no first transition metal solution is fed into the reactor from the first tank over the period from t 2 to t f .
16. The method of claim 14 , wherein the first tank has a feed stream (a 1 ) feeding into the reactor, the second tank has a feed stream (a 2 ) feeding into the reactor, the feed stream (a) is the sum of the feed stream (a 1 ) and the feed stream (a 2 ), the feed stream (a 1 ) and the feed stream (a 2 ) are contacted and mixed in a mixing apparatus without mechanical agitation before they are fed into the reactor.
17. The method of claim 16 , wherein the feed stream (al) has a flowrate of F 1 , the feed stream (a 2 ) has a flowrate of F 2 , the flowrates of F 1 and F 2 between t 1 and t 2 are defined as: F 1 =f(t); F 1 ≥0; F 2 =f(t); F 2 ≥0; and F 1 ≠F 2 .
18. The method of claim 1 , wherein after the co-precipitation reaction, the slurry of the precipitated precursor particles is drained out from the reactor by an outflow (c), the precursor particles drained out are filtered and dried to get dried precursor particles, the dried precursor particles are mixed with a lithium resource and then calcined to form concentration gradient cathode particles.
19. The method of claim 1 , wherein the method further comprises feeding a feed stream (d) containing chelating agents into the reactor, the feed stream (d) is selected from ammonia hydroxide, ammonium chloride, ammonium sulfate, ammonium dihydrogen phosphate, ethylene glycol, carboxylic acids, ammonium nitrate, glycerol, 1,3 propane-diol, urea, N,N′-dimethylurea, quaternary ammonia salts, or any combination thereof.