Method for preparing cathode particles and cathode active materials having same

Abstract

The invention relates to a method for preparing cathode particles under a co-precipitation reaction by feeding NaOH and metal sulfate solution into different vessels. The invention further provides a cathode active material having the cathode particles. By the method of the invention, the number density distribution of prepared particles is much smaller than feeding NaOH and metal sulfate together into same vessel.

Claims

1. A method for preparing cathode particles under a co-precipitation reaction, comprising the following steps: providing a first vessel and a second vessel connected in parallel, the first vessel and the second vessel where a reaction takes place is defined as a precipitation zone; feeding stream (ai) solution into one vessel, feeding stream (bi) solution into the other vessel, and feeding stream (di) into either of the vessels; re-circulating the solutions between the first vessel and the second vessel to cause a reaction; after reacting between the solutions, concentration gradient precursor particles being formed in both vessel, collecting the concentration gradient precursor particles from both vessels; filtering, washing and drying the particles; after drying, mixing the dried particles with a lithium precursor; and calcining to yield the cathode particles.

2. The method of claim 1, wherein the first vessel is larger than the second vessel, or both have same volume.

3. The method of claim 1, wherein a Reynolds number of the vessels is higher than 6400 with a stirring time of 0-1,200 seconds.

4. The method of claim 1, wherein during reaction, a temperature of the precipitation zone is between 30-800° C.

5. The method of claim 1, wherein a pH of the precipitation zone is at a range of 7 to 13.

6. The method of claim 1, wherein the stream (ai) comprises cations for precipitation, and has a concentration of 0.001-6 mol cation/L.

7. The method of claim 1, wherein steam (a.sub.i) comprises at least one metal cation, the at least one metal cation of stream (a.sub.i) is at least one selected from the group consisting of Mg, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Al.

8. The method of claim 7, wherein anions corresponding to the metal cations are at least one selected from the group consisting of sulfate, carbonate, chloride, nitrate, fluoride, oxide, hydroxide, oxyhydroxide, oxalate, carboxylate, acetate, phosphate and borate.

9. The method of claim 1, wherein stream (ai) comprises Ni.sub.xMn.sub.yCo.sub.zMe.sub.1-x-y-z where x+y+z≥0.9, z≤0.4, and Me represents additional elements.

10. The method of claim 1, wherein stream (b.sub.i) comprises anions for precipitation, and has a concentration at a range of 0.001-14 mol anion/L.

11. The method of claim 10, wherein the anion in stream (b.sub.i) is at least one selected from the group consisting of OH.sup.−, CO.sub.3.sup.2−, HCO.sub.3.sup.− and C.sub.2O.sub.4.sup.2−.

12. The method of claim 1, wherein stream (d.sub.i) comprises a chelating agent to the precipitation zone, and has a concentration in a range of 0.001-14 mol chelating agent/L.

13. The method of claim 12, wherein the chelating agent is at least one selected from the group consisting of ammonia hydroxide, ammonium chloride, ammonium sulfate, ammonium dihydrogen phosphate, ethylene glycol, carboxylic acids, ammonium nitrate, glycerol, 1,3 propane-diol, urea, N,N′-dimethylurea and quaternary ammonia salts.

14. The method of claim 1, wherein the drying is under vacuum at N.sub.2, Ar or air atmosphere for 3-24 hours at a temperature between 80° C. and 2000° C.

15. The method of claim 1, wherein the lithium precursor is at least one selected from the group consisting of LiOH.H.sub.2O, Li.sub.2CO.sub.3, LiNO.sub.3, lithium acetate, lithium metal and Li.sub.2O.

16. The method of claim 1, wherein when mixing with the lithium precursor, a ratio of lithium to metal cation is between 0.5-1.5.

17. The method of claim 1, wherein the precipitated particles are calcined at a temperature between 300-9500° C. for 2 to 48 hours.

18. The method of claim 1, wherein a ramp rate during calcining is 0.5 to 10 degrees per minute.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic view of reactors in parallel according to Example 1 of the present disclosure, wherein vessel A starts partially filled and vessel B starts fully filled, the fluids recirculate between vessels A and B as a flow of NaOH is fed to vessel A and flows of MSO.sub.4 and NH.sub.4OH are fed into vessel B.

(2) FIG. 2 shows a schematic view of reactors in parallel according to Example 4 of the present disclosure, wherein vessel A starts partially filled and vessel B starts fully filled, the fluids recirculate between vessels A and B as flows of NH.sub.4OH and MSO.sub.4 are fed into A and a flow of NaOH is fed into B.

(3) FIG. 3 shows a schematic view of reactors in parallel according to Example 2 of the present disclosure, wherein vessel A starts partially filled and vessel B starts fully filled, the fluids recirculate between vessels A and B as flows of NaOH and NH.sub.4OH are fed into vessel A and a flow of MSO.sub.4 is fed into vessel B.

(4) FIG. 4 shows a schematic view of reactors in parallel according to Example 3 of the present disclosure, wherein vessel A starts partially filled and vessel B starts fully filled, the fluids recirculate between vessels A and B as a flow of MSO.sub.4 is fed into vessel A and flows of NH.sub.4OH and NaOH are fed into vessel B.

(5) FIG. 5 shows a schematic view of reactors in parallel according to example 5, wherein vessel A starts partially filled or fully filled, while vessel B starts filled, the feed streams containing NaOH, MSO.sub.4 and NH.sub.4OH could be added to vessel A, B or both.

(6) FIG. 6 shows particle number distribution of examples 1-4 and comparative example 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

(7) The present disclosure will now be described more specifically with reference to the following embodiments. It is to be noted that the following descriptions of preferred embodiments of this invention are presented herein for purpose of illustration and description only. It is not intended to be exhaustive or to be limited to the precise form disclosed.

Example 1

(8) Preparing a mixed metal sulfate solution whose concentration being 2M: Firstly, preparing a first metal sulfate (MSO.sub.4, M represents for metals Ni, Mn, Co) solution whose concentration being 2M and a metal mole ratio Ni:Mn:Co being 0.65:0.25:0.1; preparing a second metal sulfate solution whose concentration being 2M and a metal mole ratio Ni:Mn:Co being 0.9:0:0.1. Secondly, placing the metal sulfate (MSO.sub.4) solutions in series, feeding the Ni-rich second metal sulfate solution into the precipitation zone defined above, feeding the first metal sulfate solution into the precipitation zone to mix with the second metal sulfate solution to form a mixed metal sulfate solution, whose concentration still being 2M.

(9) Preparing a NH.sub.4OH solution whose concentration being 10M: As shown in FIG. 1, providing a 4 L stainless steel agitated vessel B and a 20 L glass agitated vessel A. After that, filling the vessel B with 3.5 L of NH.sub.4OH solution whose concentration being 0.7M and stirring the solution at 1,000 rpm; filling the vessel A with 5 L of NH.sub.4OH whose concentration being 0.7M and stirring the solution at 300 rpm. And then, heating both vessels A and B to 500° C. Next, setting two peristaltic pumps at 380 mL/min and transporting the fluids from vessel A to vessel B and from vessel B to vessel A by the pumps. Once confirming that the recirculation flow is stable, and the two interconnecting streams are equal, starting the reaction. At this stage, the concentration of the NH.sub.4OH solution reaches 10M.

(10) Feeding the 2M mixed metal sulfate solution continuously into the vessel B (4 L) at a flow rate of 0.35 L/hr, feeding the 10M NH.sub.4OH solution into vessel B at 0.035 L/hr, and feeding 10.8M NaOH into vessel A (20 L), wherein NaOH is fed via controller to maintain a reaction pH at 11.9 (when measured at room temperature). After that, reacting for 22.8 hrs.

(11) After the reaction was stopped, collecting the concentration gradient precursor particles from both vessels, and mixing the particles from both vessels together. And then, filtering and washing the particles with copious amounts of DI water using a large Buchner filter. After that, drying the collected particles at 1000° C. overnight in a N.sub.2 atmosphere. Next, mixing the dried particles with LiOH.H.sub.2O at a Li:M ratio of 1.03:1, wherein M represents for Ni—Mn—Co. Finally, calcining in an oxygen atmosphere at 8000° C. In this way, cathode active materials are yielded, which having the particles prepared.

Example 2

(12) The conditions used in example 2 is similar as that in example 1, except that the NH.sub.4OH feed stream was fed to the vessel A (20 L) instead of the vessel B (4 L). As shown in FIG. 3, the fluids recirculate between vessels A and B as flows of NaOH and NH.sub.4OH are fed into vessel A, while a flow of and MSO.sub.4 is fed into vessel B. Vessel A starts partially filled, while vessel B starts fully filled.

Example 3

(13) The conditions used in example 3 is similar as that in example 1, except that the MSO.sub.4 feed stream was fed to the 20 L, and the NaOH was fed to the 4 L. As shown in FIG. 4, the fluids recirculate between vessels A and B as a flow of MSO.sub.4 was fed into vessel A, while flows of NH.sub.4OH and NaOH were fed into vessel B. Vessel A starts partially filled, while vessel B starts filled.

Example 4

(14) The conditions used in example 4 is similar as that in example 1, except that flows of MSO.sub.4 and NH.sub.4OH feed streams were fed to vessel A (20 L), and a flow of NaOH was fed to vessel B(4 L), as shown in FIG. 2.

Comparative Example 1

(15) The conditions used in comparative example 1 is similar as that in example 1, except that vessel A (20 L glass reactor) was firstly filled with 5 L of 0.7M NH.sub.4OH and heated to 500° C. while mixing at 300 rpm, and then the NaOH, MSO.sub.4 and NH.sub.4OH feed streams, with compositions and flowrate identical to example 1, were fed into the vessel A for the same amount of time as example 1. Once the precipitation finished, collecting the particles, filtering and drying the particles using the same conditions as in example 1.

(16) Characterization of Particles

(17) A tap density was tested by the following steps: loading 20 g of cathode active material into a 25 mL graduated cylinder, and then tapping the cylinder 2000 times at 250/min speed on a tap density instrument.

(18) A particle number distribution was collected on an Mastersizer 2000 laser particle size analyzer. About 2 g sample was first pre-disper 5 min by a dispersant with 1 ultrasonic, then disper in 1000 ml water. After that, the particle number distribution was tested.

(19) FIG. 6 shows the particle number distributions of Examples 1-4 and comparative example 1. Table 1 shows the obtained tap density, particle number D50 and particle size D50 of examples 1-4 and comparative example 1.

(20) TABLE-US-00001 TABLE 1 Particle Number Tap Density Particle Size D50 (μm) (g/cc) D50 (μm) Example 2 10.03 2.45 12.29 Comparative 9.39 2.38 11.48 Example 1 Example 3 7.10 2.26 9.09 Example 1 2.64 2.21 12.55 Example 4 4.12 1.96 6.8

(21) The comparison above shows that through the proposed method above, the number density distribution of prepared particles is controlled to be below 15 μm, in one embodiment, the number density distribution of the particles is below 10 μm; in another embodiment, the number density distribution of the particles is below 5 μm. In one embodiment, the final active material particles have a tap density in a range of 1-3 g/cc. In another embodiment, the final active material particles have a tap density in a range of 1.5-2.7 g/cc.

(22) Further, using the present procedure, the number density D50 can be decreased by 1-1000 times by feeding a flow of NaOH stream and flows of MSO.sub.4 and NH.sub.3 streams into various combinations of two agitation vessels. Under these conditions, a large decrease in the number density distribution occurs, as shown by FIGS. 1-6. The tap density of the final active material is also decreased by 33-100% under these processing conditions.

(23) The proposed effect is most prominent when the flows of MSO.sub.4 and NH.sub.3 are fed into the weaker agitated vessel A, and NaOH is fed to the stronger agitated vessel B in the parallel configuration, as shown in the results of example 4.

(24) Meanwhile, by using the present process, the particle number density D50 can be changed by 0.01-3 times when the NaOH stream is fed to the lesser agitated vessel A and the MSO.sub.4 is fed to the stronger agitated vessel B. The NH.sub.3 can be delivered to either vessel. By separating the NaOH and MSO.sub.4 steam, particle growth via agglomeration will occur. Referring to examples 1 and 2.

(25) FIG. 6 and Table 1 show that comparing with a method wherein NaOH, MSO.sub.4 and NH.sub.4OH are fed simultaneously into same vessel(s), feeding NaOH and MSO.sub.4 into different vessels would yield a larger number of smaller particles except when both NaOH and NH.sub.3OH are fed into same vessel.

(26) It should be noted that the data of example 2 shows a way to control the particle number distribution larger. What we are really trying to do is manipulate the number density lower, because we expect that to make more broad packed electrodes. However, example 2 is a condition tested, and the result of it going higher could be needed if a reaction base case was too small.

(27) While the invention has been described in terms of what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention needs not be limited to the disclosed embodiment. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures.