METHOD OF MAKING PARTICULATE (OXY)HYDROXIDES, AND PARTICULATE (OXY)HYDROXIDES

Abstract

Disclosed herein is a method for making a particulate (oxy)hydroxide of TM, where TM is a combination of nickel and at least one metal selected from Co and Mn, the process including: (a) providing an aqueous solution () containing water-soluble salts of Ni and of at least one transition metal selected from Co and Mn, (b) combining a solution () and a solution () and, if applicable, a solution () at a pH value in a range of from 12.0 to 13.0 determined at 23 C. in a continuous stirred tank reactor, thereby creating a slurry of solid particles of a hydroxide containing nickel, and (c) transferring slurry from step (b) into a batch-wise operated stirred tank reactor where a solution () and a solution () and optionally a solution () are combined with the slurry at a pH value in a range of from 11.0 to 12.0 determined at 23 C.

Claims

1. A process for making a particulate (oxy)hydroxide of TM, wherein TM is a combination of metals according to general formula (I)
(Ni.sub.aCo.sub.bMn.sub.c).sub.1-dM.sub.d(I) wherein a is in a range of from 0.6 to 0.95, b is in a range of from 0.025 to 0.2, c is in a range of from zero to 0.2, and d is in a range of from zero to 0.1, wherein M is selected from the group consisting of Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and a+b+c=1, or wherein TM is a combination of metals according to general formula (II)
(Ni.sub.aCo.sub.bMn.sub.c).sub.1-dM.sub.d(II) wherein a is in a range of from 0.25 to 0.4, b is in a range of from zero to 0.2, c is in a range of from 0.6 to 0.75, and d is in a range of from zero to 0.1, wherein M is selected from the group consisting of Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and a+b+c=1, and wherein said process comprises the steps of: (a) providing one or more aqueous solution(s) () containing water-soluble salts of Ni and of at least one transition metal selected from the group consisting of Co and Mn, and, optionally, at least one further metal selected from the group consisting of Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution () containing an alkali metal hydroxide and, optionally, an aqueous solution () containing a complexing agent, (b) combining solution(s) () and solution () and, if applicable, solution () at a pH value in a range of from 12.0 to 13.0 determined at 23 C. in a continuously operated stirred tank reactor, thereby creating solid particles of hydroxide, said solid particles being slurried, and (c) transferring slurry from step (b) into a stirred tank reactor wherein a solution () and a solution () and, optionally, a solution () are combined with the slurry at a pH value in a range of from 11.0 to 12.0 determined at 23 C., wherein each of the stirred tank reactor(s) is equipped with a solid-liquid separation device through which mother liquor is withdrawn from the stirred tank reactor(s).

2. The process according to claim 1, wherein the process is carried out in a cascade of at least two stirred tank reactors of which the first stirred tank reactor is equipped with an overflow system through which slurry is removed from the first stirred tank reactor and transferred to the second stirred tank reactor, directly or indirectly.

3. The process according to claim 1, wherein the slurry is removed from the continuous stirred tank reactor and transferred to a stirred storage vessel where the slurry is stored under stirring for a time period of from 15 minutes to 24 hours before being transferred to the second stirred tank reactor.

4. The process according to claim 3, wherein the temperature during the storing step is in a range of from 20 to 70 C.

5. The process according to claim 3, wherein the pH value of the slurry in the storage vessel is in a range of from 10.0 to 13.0, determined at 23 C.

6. The process according to claim 3, wherein at the same time in a range of from 5 to 30 vol-% of slurry are in the storage vessel and 70 to 95 vol-% of the slurry are in the tank reactors wherein steps (b) and (c) are performed.

7. The process according to claim 1, wherein in at least one of steps (b) and (c), a coaxial nozzle is used for addition of solution () and solution () or solution () and solution ().

8. The process according to claim 1, wherein in at least one of steps (b) and (c), a clarifier or at least one candle filter is used to mother liquor withdrawal.

9. A particulate (oxy)hydroxide of TM, wherein TM is a combination of metals according to general formula (I)
(Ni.sub.aCo.sub.bMn.sub.c).sub.1-dM.sub.d(I) wherein a is in a range of from 0.6 to 0.95, b is in a range of from 0.025 to 0.2, c is in a range of from zero to 0.2, and d is in a range of from zero to 0.1, wherein M is selected from the group consisting of Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and a+b+c=1, or wherein TM is a combination of metals according to general formula (II)
(Ni.sub.aCo.sub.bMn.sub.c).sub.1-dM.sub.d(II) wherein a is in a range of from 0.25 to 0.4, b is in a range of from zero to 0.2, c is in a range of from 0.6 to 0.75, and d is in a range of from zero to 0.1, wherein M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and a+b+c=1, wherein said particulate (oxy)hydroxide has an average particle diameter (d50) in a range of from 3 to 20 m and a core-shell structure wherein both core and shell show an essentially radial alignment of platelet-shaped primary particles and wherein the core and the shell are separated by a porous layer that contains randomly arranged primary particles.

10. The particulate (oxy)hydroxide according to claim 9, having a particle size distribution with a span [(d90)(d10)]/(d50) in a range of from 0.2 to 0.6.

11. The particulate (oxy)hydroxide according to claim 9, wherein the porous layer between the core and the shell has an average thickness in a range of from 0.1 to 1.0 m.

12. (canceled)

13. (canceled)

14. (canceled)

15. (canceled)

Description

[0113] The invention is further illustrated by working examples and by a drawing.

Brief Description of the Drawing, FIG. 1:

[0114] Schematic set-up. Reactor A for step (b), a stirred tank reactor with a clarifier, for withdrawal of mother liquor. The bottom valve is not shown.

[0115] The aging tank is in the middle. Reactor B for performing step (c) is on the right, with a clarifier.

1. Synthesis of Precursors

[0116] General: The following set-up is used:

[0117] A 3.2 liter stirred tank reactor (first precipitation reactor or Reactor A), equipped with baffles and a cross-arm stirrer with a diameter of 0.06 m, and a cylinder-shaped clarifier made from glass through which mother liquor can be withdrawn from Reactor A. Reactor A in addition has a bottom valve.

[0118] Reactor A is equipped with an overflow system that leads to an aging tank with a stirrer, volume: 25 l. The aging tank is connected to the second precipitation tank (or Reactor B), volume 3.2 liter stirred tank reactor with baffles and a cross-arm stirrer with a diameter of 0.06 m, and a cylinder-shaped clarifier made from glass.

[0119] Both clarifiers are equipped with a pump can re-introduce paste-like residue with a very high solids content from the lower part of the glass cylinder-shaped clarifier back into the respective reactor.

[0120] rpm: revolutions per minute

[0121] The following aqueous solutions were provided, step (a.1): [0122] Solution (.1): NiSO.sub.4, CoSO.sub.4 and MnSO.sub.4 dissolved in deionized water (molar ratio 91:4.5:4.5, total transition metal concentration: 1.65 mol/kg) [0123] Solution (.1): 25 wt % NaOH dissolved in deionized water [0124] Solution (.1): 25 wt % ammonia in deionized water

I.1 Synthesis of an Inventive Precursor P-CAM. 1

[0125] Reactor A of the set-up described above is charged with 1.6 l deionized water containing 15 g ammonia and heated to 55 C. Subsequently, solution (.1) is added in a way that the pH value at 23 C. is set to 12.18 and the stirrer is set to 700 rpm.

[0126] Step (b.1) Reactor A is then continuously fed with solutions (.1), (.1) and (.1) in a way that the pH value of the mother liquor at 23 C. is 12.2, measured at 23 C., and the molar ratio of NH.sub.3 to the sum of Ni and Co and Mn in Reactor A is 0.22. The precipitation is conducted under an atmosphere of N.sub.2. The individual flow rates of the solutions are adjusted to meet a hydraulic residence time of 5 hours.

[0127] In the course of step (b.1), particle free mother liquor was continuously withdrawn from the Reactor A by the clarifier while the concentrated slurry is returned into Reactor A. The pump of the clarifier is operated in a way that less than 10% of total particle mass is present in the clarifier. The mass flow of withdrawn mother liquor is 65% of the feed mass flow. In parallel to mother liquor withdrawal, the forming slurry is continuously discharged from the Reactor A via a free overflow and collected in the aging tank. By this approach, the solid content of the slurry in the Reactor A is increased to 395 g/l and kept constant during the continuous operation of step (b.1).

[0128] The resulting slurry with mean particle size (d50) of 4.2 m is collected in the stirred aging tank. After a residence time of one day, parts of this slurry are transferred to Reactor B which is charged with 55 C. solution containing 20 g ammonia with a pH value measured at 23 C. of 11.4.

[0129] Step (c.1): Then, dosage of solutions (.1), (.1) and (.1) is started. The individual flow rates of the solutions are adjusted to meet a hydraulic residence time of 5 hours. Over a precipitation time of 21 hours, mother liquor is continuously withdrawn from the slurry resulting in a high solids slurry that was finally removed from Reactor B through a bottom valve.

[0130] Then, the slurry is separated by filtration, washed with deionized water and solution (1), and dried at 120 C. for 16 hours to obtain the precursor P-CAM. 1 with molar composition of Ni:Co:Mn=91:4.5:4.5, an average particle size (d50)=13.4 m and span=0.42. The precursors show an excellent sphericity with a form factor of 0.989. Furthermore, SEM analyses of P-CAM.1 shows a core-shell structure with essentially radial alignments of platelet-shaped primary particles in the core and the shell, and a porous layer between the core and the shell in which the primary particles are randomly oriented.

I.2 Synthesis of a Comparative Precursor, C-P-CAM.2

[0131] Step (a.2): The same solutions (.1), (.1) and (.1) as in I.1 were used.

[0132] Step c-(b.2): A 3.2 l-stirred tank reactor similar to Reactor A but without clarifier is charged with 1.6 l deionized water containing 7 g ammonia and heated to 55 C. Subsequently, solution (.1) is added in a way that the pH value measured at 23 C. is set to 12.2, and the stirrer is set to 1000 rpm. The tank reactor is then continuously fed with solutions (.1), (.1) and (.1) in a way that the pH value of the mother liquor at 23 C. is 12.2 and the molar ratio of NH.sub.3 to the sum of Ni and Co and Mn in the reactor is 0.1. The process is conducted under inert gas atmosphere. The individual flow rates of the solutions are adjusted to meet a hydraulic residence time of 5 hours.

[0133] The slurry with an average particle size (d50) of 4.1 m was continuously discharged via a free overflow and collected in the aging tank. The slurry had a solid content of 125 g/l.

[0134] After 24 hours, parts of this slurry are transferred to Reactor B which is charged with 55 C. solution containing 20 g ammonia with a pH value measured at 23 C. of 11.4. This 2.sup.nd reactor was also equipped with a mother liquor withdrawal device but had no free overflow.

[0135] Step (c.2): Then, dosage of solutions (.1), (.1) and (.1) is started. The individual flow rates of the solutions are adjusted to meet a hydraulic residence time of 5 hours. Over a precipitation time of 21 h mother liquor was continuously withdrawn from the slurry resulting in a high solids slurry that was finally removed from Reactor B through a bottom valve.

[0136] The collected slurry was separated by filtration, washed with deionized water and with solution (.1), and dried at 120 C. for 16 hours to obtain the comparative precursor C-P-CAM.2 with molar composition of Ni:Co:Mn=91:4.5:4.5, an average particle size (d50)=13.2 m, determined by LASER diffraction, and a span=0.45. Compared to P-CAM. 1, the sphericity was lower with a form factor of 0.974. Furthermore, only the shell of comparative precursor C-P-CAM.2 showed a radial alignment of platelet-shaped primary particles while the core consisted of randomly oriented primary particles.

II. Manufacture of Inventive and Comparative Cathode Material

II.1 Preparation of Dehydrated Metal Oxide Precursors

[0137] 50 g of P-CAM.1 was heated in a Linn oven for 2 hours at 450 C. under flowing air. The metal oxide P-CAM.O.1 had an average particle diameter (D50) of 13.3 m and a span of 0.39.

[0138] For comparison purposes, 50 g of C-P-CAM.2 was heated in a Linn oven for 2 hours at 450 C. under flowing air. The metal oxide C-P-CAM.O.2 had an average particle diameter (D50) of 13.1 m and a span of 0.42

II.2 Calcination and Post-Treatments

[0139] 30 g of P-CAM.O.1 was mixed with LiOH monohydrate (molar ratio Li/metal=1.02), 133 mg TiO.sub.2 and 122 mg ZrO.sub.2 for 15 minutes in a grinding mill. A saggar was charged with the resultant mixture and transferred into a Linn oven. The temperature was raised at rate of 2 C/min to 750 C. under flowing oxygen and then held constant at 750 C. for 8 hours and subsequently allowed to naturally cool under flowing oxygen. The resultant powder was then deagglomerated in a grinding mill and sieved. After de-agglomeration, the powder had an average particle diameter (D50) of 13.2 m, a span of 0.37 and an average form factor of 0.991.

[0140] 30 g powder was then added to 15 ml deionized water stirred for 2 minutes and then immediately filtered on a Buchner funnel to remove water. The wet filter cake was then dried under an N.sub.2 atmosphere with reduced pressure at 120 C. for 10 hours.

[0141] The resultant powder was then dry coated with boric acid by mixing 30 g powder, mixing media and 30 mg boric acid for 40 minutes at low speed on a roller mill. A saggar was charged with the dried powder and heat treated in Linn oven. The Linn oven was heated to 300 C. for 2 hours under oxygen atmosphere and allowed to cool naturally. Inventive CAM.1 was obtained.

[0142] The comparative oxide PCAM C-P-CAM.O.2 was treated in the same way and C-CAM.2 was obtained. After de-agglomeration, the resultant powder had an average particle diameter (D50) of 13.0 m, a span of 0.41 and an average form factor of 0.973.

III. Testing of Cathode Active Material

III.1 Cathode Manufacture

[0143] Positive electrode: PVDF binder (Solef 5130) was dissolved in NMP (Merck) to produce a 7.5 wt. % solution. For electrode preparation, binder solution (3 wt. %), graphite (SFG6L, 2 wt. %), and carbon black (Super C65, 1 wt.-%) were suspended in NMP. After mixing using a planetary centrifugal mixer (ARE-250, Thinky Corp.; Japan), either inventive CAM.1 or C-CAM.2 (94 wt. %) was added and the suspension was mixed again to obtain a lump-free slurry. The solid content of the slurry was adjusted to 65%. The slurry was coated onto Al foil using a KTF-S roll-to-roll coater (Mathis AG). Prior to use, all electrodes were calendared. The thickness of cathode material was 70 m, corresponding to 15 mg/cm.sup.2. All electrodes were dried at 105 C. for 7 hours before battery assembly.

III.2 Electrolyte Manufacture

[0144] A base electrolyte composition was prepared containing 12.7 wt % of LiPF.sub.6, 26.2 wt % of ethylene carbonate (EC), and 61.1 wt % of ethyl methyl carbonate (EMC) (EL base 1), based on the total weight of EL base 1. To this base electrolyte formulation 2 wt. % of vinylene carbonate (VC) was added (EL base 2).

III.3 Coin Cell Manufacture

[0145] Coin-type half cells (20 mm in diameter and 3.2 mm in thickness) comprising a cathode prepared as described under II.1.1 and lithium metal as working and counter electrode, respectively, were assembled and sealed in an Ar-filled glove box. In addition, the cathode and anode and a separator were superposed in order of cathode//separator//Li foil to produce a half coin cell. Thereafter, 0.15 mL of the EL base 1 which is described above (III.2) were introduced into the coin cell.

III.4 Cycling Tests

[0146] The initial performance, C-rate performance and cycling performance were measured as follows: Coin half cells according to III.3 were tested in a voltage range between 4.3 V to 2.8 V at room temperature. For the initial cycles, the initial lithiation was conducted in the CC-CV mode, i.e., a constant current (CC) of 0.1 C was applied until reaching 4.3V, followed by the CV step until the current dropped to 0.01 C. After 10 min resting time, reductive lithiation was carried out at constant current of 0.1 C up to 2.8 V. For the C-rate test charge and discharge rates were adjusted accordingly. For the cycling test, the constant current was chosen to be 1C until 100 cycles were reached. The results are summarized in Table 1.

TABLE-US-00001 TABLE 1 Physical and electrochemical data of cathode active materials. The pressed densities were determined at 250 MPa 0.1 C rate Press D50 1.sup.st Discharge capacity density m Span mAh/g mAh/g g/cm.sup.3 CAM. 1 13.2 0.37 228.6 225.8 3.42 C-CAM. 2 13.0 0.41 225.7 222.3 3.29