A METHOD FOR THE PRECIPITATION OF PARTICLES OF A METAL CARBONATE MATERIAL WITHOUT USE OF A CHELATING AGENT

Abstract

In a method for the precipitation of particles of a metal carbonate material comprising nickel and manganese in an atomic ratio of 0≤Ni:Mn≤1:3, aqueous solutions comprising sulfates or nitrates of nickel and manganese are mixed with aqueous solutions of carbonates or mixtures of carbonates and hydroxides of sodium or potassium in a stirred reactor at pH>7.5 without the use of a chelating agent. Thereby agglomerated particles are formed without any subsequent process steps, in particular no subsequent process at temperatures higher than the precipitation temperature.

Claims

1. A method for the precipitation of particles of a metal carbonate material comprising nickel and manganese in an atomic ratio of 0≤Ni:Mn≤1:3, wherein aqueous solutions comprising sulfates of nickel and manganese or aqueous solutions comprising nitrates of nickel and manganese are mixed with aqueous solutions of sodium carbonate or potassium carbonate or mixtures of sodium carbonate and sodium hydroxide or mixtures of potassium carbonate and potassium hydroxide in a stirred reactor at pH>7.5 without the use of a chelating agent, thereby forming agglomerated particles without any subsequent process steps.

2. Method according to claim 1, wherein the aqueous solutions comprising sulfates of nickel and manganese or aqueous solutions comprising nitrates of nickel and manganese are contained in a first vessel, and the aqueous solutions of sodium carbonate or potassium carbonate or mixtures of sodium carbonate and sodium hydroxide or mixtures of potassium carbonate and potassium hydroxide are contained in a second vessel, and the mixing thereof takes place in a stirred reactor.

3. Method according to claim 1, wherein aqueous solutions comprising sulfates of nickel and manganese or aqueous solutions comprising nitrates of nickel and manganese are mixed with aqueous solutions of sodium carbonate or potassium carbonate.

4. Method according to claim 1, wherein the agglomerated particles are characterized by an average circularity higher than 0.90 and simultaneously an average aspect ratio lower than 1.50.

5. Method according to claim 1, wherein the agglomerated particles are essentially spherical.

6. Method according to claim 1, wherein the Ni:Mn atomic ratio in the metal carbonate material is ¼≤Ni:Mn≤⅓.

7. Method according to claim 1, wherein the pH in the stirred reactor is 7.5<pH<12.0.

8. Method according to claim 1, wherein D50 of the precipitate is between 3 and 50 μm, where D50 of a volume-based particle size distribution is defined as the median particle size.

9. Method according to claim 8, wherein the distribution of the agglomerate size of the precipitate is characterized in that the ratio between D90 and D10 is smaller than or equal to 4, wherein D10 is the particle size where 10% of the volume of the population lies below the value of D10, and D90 is the particle size where 90% of the volume of the population lies below the value of D90.

10. Method according to claim 1, wherein the agglomerated particles are subjected to growth and polishing in a stirred reactor to obtain particles of the desired morphology and size.

11. Method according to claim 10, where the stirred reactor comprises of two or more stirred sub-reactors connected in series.

12. Method according to claim 1, wherein the precipitate is used as a precursor for the preparation of lithium-ion battery positive electrode materials.

Description

EXAMPLE 1 (COMPARATIVE EXAMPLE)

[0037] A metal ion solution of NiSO.sub.4 and MnSO.sub.4 with a Ni:Mn atomic ratio of 1:3 was prepared by dissolving 258 g of NiSO.sub.4.7H.sub.2O and 521 g of MnSO.sub.4.H.sub.2O in 1775 g water. In a separate flask, a carbonate solution was prepared by dissolving 2862 g of Na.sub.2CO.sub.3.10H.sub.2O and 68 g NH.sub.3.H.sub.2O in 2995 g water. The metal ion solution and the carbonate solution are added separately into a reactor provided with vigorous stirring (650 rpm) and a temperature of 50° C. The volume of the reactor was 1 liter.

[0038] The product was continuously removed from the reactor, so that the residence time of the reactants in the reactor was 30 minutes. FIG. 1 shows Ni.sub.0.5Mn.sub.1.5(CO.sub.3).sub.2 particles made by using this method.

EXAMPLE 2

[0039] A metal ion solution of NiSO.sub.4 and MnSO.sub.4 with a Ni:Mn atomic ratio of 1:3 was prepared by dissolving 258 g of NiSO.sub.4.7H.sub.2O and 521 g of MnSO.sub.4.H.sub.2O in 1775 g water. In a separate flask, a carbonate solution was prepared by dissolving 424 g of Na.sub.2CO.sub.3 in 1932 g water. No ammonia or other chelating agents were used. The metal ion solution and the carbonate solution are added separately into a reactor provided with vigorous stirring (450 rpm) and a temperature of 35° C. The volume of the reactor was 1 liter.

[0040] The product was removed from the reactor after 100 minutes and divided into two. Precipitation was continued on half of the product for 60 minutes, after which it was again divided into two. This last step was repeated two more times. FIG. 2 shows Ni.sub.0.5Mn.sub.1.5(CO.sub.3).sub.2 particles made by using this method.

[0041] The difference between carbonate precursor particles precipitated with and without a chelating agent can be seen in FIG. 1 and FIG. 2, showing photographs of particles made with and without a chelating agent, respectively. The particles precipitated without the use of a chelating agent look just as spherical and uniform in size (or even slightly more spherical and more uniform) than particles precipitated with the use of ammonia.

EXAMPLE 3

[0042] A metal ion solution identical to that used in Example 2 was prepared. In a separate flask, a carbonate solution was prepared by dissolving 553 g of K.sub.2CO.sub.3 in 1881 g water. No ammonia or other chelating agents were used. The metal ion solution and the carbonate solution are added separately into a reactor provided with vigorous stirring (400 rpm) and a temperature of 35° C. The volume of the reactor was 8 liters.

[0043] The product was removed from the reactor after 120 minutes and divided into two. Precipitation was continued on half of the product for 120 minutes, after which it was again divided into two. This last step was repeated two more times. The product thus obtained was collected and repeatedly and thoroughly washed on a Büchner funnel using near-boiling deionized water, until the electrical conductivity of the waste water was below 130 μS/cm. Further washing did not result in any significant further decrease in conductivity.

[0044] The washed and dried precursor samples were analyzed using room-temperature powder X-ray diffraction equipment using Cu Kα.sub.1 radiation. The Rietveld refining of the obtained spectrum results in the following phase composition: 100% rhodochrosite (a=4.793 Å, b=15.549 Å), i.e. a pure metal carbonate. The corresponding diffractogram is shown in FIG. 3.

EXAMPLE 4

[0045] A metal ion solution identical to that used in Example 2 was prepared. In a separate flask, 2 liters of a carbonate solution was prepared by dissolving 368 g K.sub.2CO.sub.3 and 75 g KOH (corresponding to a molar ratio of K.sub.2CO.sub.3 to KOH of 2:1) in deionized water. The metal ion solution and the carbonate solution were added separately into a reactor provided with vigorous stirring (650 rpm) and a temperature of 36° C. The volume of the reactor was 1 liter.

[0046] The product was removed from the reactor after 100 minutes and divided into two. Precipitation was continued on half of the product for 60 minutes. The product thus obtained was collected and repeatedly and thoroughly washed on a Büchner funnel using near-boiling deionized water, until the electrical conductivity of the waste water was below 130 μS/cm. Further washing did not result in significant further decreases in conductivity.

[0047] The washed and dried precursor samples were analyzed using room-temperature powder X-ray diffraction equipment using CuKα.sub.1 radiation. The Rietveld refining of the obtained spectrum results in the following phase composition: 100% rhodochrosite, i.e. a pure metal carbonate. The corresponding diffractogram is shown in FIG. 4. No peaks corresponding to hydroxides or hydroxycarbonates are present in the diffractogram. Therefore, pure metal carbonate material was obtained as product, even though the carbonate solution used during precipitation was a mixture of carbonate and hydroxide.

[0048] In the four examples above, the metal ion solution and the carbonate solution were added dropwise into the stirred reactor.

[0049] It is appreciated by those skilled in the art that changes can be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.