INTRODUCTION OF TITANIUM HOMOGENEOUSLY INTO A SOLID MATERIAL

Abstract

The invention relates to a method for the precipitation of a solid material, where the method comprises: providing an aqueous metal ion solution, said metal ion solution comprising TiOSO.sub.4 and metal ions of a metal M, where M is one or more of the elements: Mg, Co, Cu, Ni, Mn, Fe; providing an aqueous carbonate solution; and mixing said aqueous metal ion solution and said aqueous carbonate solution thereby providing a solid material comprising titanium and a metal carbonate comprising said metal(s) M, where the titanium is homogeneously distributed within the solid material. The invention also relates to a solid material, a method of preparing a positive electrode material for a secondary battery from the solid material and the use of the solid material as a precursor for the preparation of a positive electrode material for a secondary battery.

Claims

1. A method for the precipitation of a solid material, said method comprising: providing an aqueous metal ion solution, said metal ion solution comprising TiOSO.sub.4 and metal ions of a metal M, where M is one or more of the elements: Mg, Co, Cu, Ni, Mn, Fe; providing an aqueous carbonate solution; and mixing said aqueous metal ion solution and said aqueous carbonate solution thereby providing a solid material comprising titanium and a metal carbonate comprising said metal(s) M, where the titanium is homogeneously distributed within the solid material.

2. A method according to claim 1, where said metal ion solution comprises Mg.sup.2+ ions and metal ions of a metal M, where M is one or more of the elements: Co, Cu, Ni, Mn, Fe.

3. A method according to claim 1, where M contains Ni, Mn and Mg.

4. A method according to claim 1, where the metal ion solution is prepared from sulfate(s), nitrate(s) or acetate(s).

5. A method according to claim 1, wherein the method is carried out without the use of a chelating agent.

6. A method according to claim 1, wherein the solid material is precipitated and agglomerated into agglomerated particles, wherein D50 of said agglomerated particles is between 1 and 50 m.

7. A method according to claim 6, wherein the agglomerated particles are essentially spherical.

8. A method according to claim 6, wherein the agglomerated particles are characterized by an average circularity higher than 0.90 and simultaneously an average aspect ratio lower than 1.50.

9. A method according to claim 1, wherein the pH value of the mixed aqueous metal ion solution and aqueous carbonate solution is 7.5<pH<10.0.

10. A method according to claim 1, further comprising the step of: providing a NaOH solution and mixing the NaOH solution with the aqueous metal ion solution and the aqueous carbonate solution.

11. A solid material prepared by the method according to claim 1, where said solid material comprises titanium as well as a metal carbonate comprising said metal(s), where M is one or more of the elements: Mg, Co, Cu, Ni, Mn, Fe, and where titanium is homogeneously distributed within said solid material.

12. A solid material according to claim 11, wherein the solid material has an overall composition such that the atomic ratio Ti:M between titanium and said metal(s) M is 0<Ti:M0.2.

13. A solid material according to claim 11, where said solid material comprises Mg and a metal M, where M is one or more of the elements: Co, Cu, Ni, Mn, Fe.

14. A solid material according to claim 11, where M contains Ni, Mn and Mg.

15. A solid material according to claim 11, where Ti is present in the solid material as an oxide, a hydroxide, a carbonate or mixtures thereof.

16. A solid material according to claim 11, wherein the solid material after precipitation has been agglomerated into particles, wherein D50 of said agglomerated particles is between 1 and 50 m.

17. A method of preparing a positive electrode material for a secondary battery from the solid material of claim 12, comprising the steps of: mixing the solid material comprising titanium as well as a metal carbonate with a starting material comprising Li or Na, sintering the solid material and the starting material, thereby partly or fully decomposing said solid material and said starting material comprising Li or Na.

18. A precursor for the preparation of positive electrode material for a secondary battery comprising the solid material of claim 12, after lithiation or sodiation of the solid material.

Description

EXAMPLES

[0038] In the following a number of examples are described. Each example describes an experiment. In the examples, specific molarities, temperatures and CSTR parameters are indicated; however, these should not be seen as limiting the invention since the experiments indicate a larger process window allowing similar materials to be synthesized with variation of i.a. molarities, temperatures and CSTR parameters.

Example 1

Precipitation of Titanium(IV) Oxysulfate and Metal Sulfate with Carbonate

Embodiment of the Invention

[0039] A material with the proposed formula Ni.sub.aMn.sub.bMg.sub.cTi.sub.1-a-b-c(CO.sub.3).sub.x(OH).sub.2-2x (with 0<a+b+c<1 and 0<x1) can be synthesized by an aqueous co-precipitation process in a continuous stirred tank reactor (CSTR), which has been described and illustrated elsewhere [Schmidt, Lanny D. (1998). The Engineering of Chemical Reactions. New York: Oxford University Press].

[0040] A continuous stirred tank reactor (CSTR) where reactants and products are continuously added and withdrawn is the idealized opposite of the well-stirred batch and tubular plug-flow reactors. In practice, mechanical or hydraulic agitation is required to achieve uniform composition and temperature, a choice strongly influenced by process considerations.

[0041] In this example, a 0.5 L CSTR is initially filled with distilled water corresponding to 20 vol. % of the reactor and adjusted to a pH of 9 by adding appropriate amounts of Na.sub.2CO.sub.3.

[0042] A metal salt solution comprising Ni, Mn, Mg and Ti ions with a total concentration of 2.2 M, is prepared by dissolving appropriate amounts of NiSO.sub.4, MnSO.sub.4, MgSO.sub.4 and TiOSO.sub.4 in deionized water. Total concentrations other than 2.2 M can be used, as long as the concentration is approximately 0.1 M below the solubility limit for the metal salts.

[0043] The metal salt solution is subsequently pumped into a CSTR. In order to precipitate the metal cations, a 2.08 M basic solution of Na.sub.2CO.sub.3 is simultaneously pumped separately into the CSTR. The addition of extra base in the form of 7.66 M NaOH in a separate feed can be employed to compensate for the acidity of the TiOSO.sub.4.

[0044] No chelating agent such as ammonium hydroxide or ammonium carbonate is required.

[0045] The solution is stirred at 900 rpm and the temperature of the solution is maintained at 30 C. by circulating hot water through a jacket in the CSTR.

[0046] The total feed flow rate is adjusted to 160 mL/hour assuring an average residence time (reactor volume divided by the total flow rates) of around 3 hours in the CSTR.

[0047] At the initial stage of the co-precipitation reaction, irregular secondary particles from the agglomeration of primary precipitated structures were formed. These irregular particles change gradually into spherical particles during the process.

[0048] Hence, a total of 6 residence times is passed before the product can be collected.

[0049] The resulting liquid dispersion that overflowed from the CSTR is feed into another reactor for an aging step, which is kept at the same reaction conditions as the CSTR.

[0050] Finally, the solid precipitate can be collected by filtration, washing and drying at 110 C. for 12 h to obtain the solid material.

[0051] The solid material consists of spherical particles less than 30 m with a low amount of sulfur residue impurities. The spherical morphology is preserved upon drying and heating to 900 C.

Example 2

Precipitation of Metal Sulfate with Carbonate

Comparative Example

[0052] A material with the proposed formula Ni.sub.aMn.sub.bMg.sub.1-a-b(CO.sub.3).sub.x(OH).sub.2-2x (with 0<a+b<1 and 0<x1) can be synthesized by an aqueous co-precipitation process in a continuous stirred tank reactor (CSTR) [see EXAMPLE 1 for references].

[0053] In this example, specific molarities, temperatures and CSTR parameters are mentioned, but experiments indicate a larger process window allowing similar materials to be synthesized with variations of these parameters.

[0054] In this example, a 1.0 L CSTR is initially filled with distilled water corresponding to 50 vol. % of the reactor and adjusted to a pH of 9.3 by adding appropriate amounts of Na.sub.2CO.sub.3.

[0055] A metal salt solution comprising Ni, Mn, and Mg with a total concentration of 2.0 M (total concentrations other than 2.2 M can be used, as long as the concentration is approximately 0.1 M below the solubility limit for the metal salts), is prepared by dissolving appropriate amounts of NiSO.sub.4, MnSO.sub.4, and MgSO.sub.4 in deionized water.

[0056] The metal salt solution is then pumped into a CSTR. In order to precipitate the metal cations, a 2.1 M basic solution of Na.sub.2CO.sub.3 is simultaneously pumped separately into the CSTR.

[0057] No chelating agent such as ammonium hydroxide or ammonium carbonate is required.

[0058] The solution is stirred at 650 rpm and the temperature of the solution is maintained at 40 C. by circulating hot oil through a jacket in the CSTR.

[0059] The total feed flow rate is adjusted to 260 mL/hour assuring an average residence time (reactor volume divided by the total flow rates) of around 4 hours in the CSTR.

[0060] At the initial stage of the co-precipitation reaction, irregular secondary particles from the agglomeration of primary precipitated structures were formed. These irregular particles change gradually into spherical particles during the process.

[0061] Hence, a total of 2 residence times is passed before the product can be collected.

[0062] The resulting liquid dispersion that overflowed from the CSTR is feed into another reactor for an aging step, which is kept at the same reaction conditions as the CSTR.

[0063] Finally, the solid precipitate can be collected by filtration, washing and drying at 110 C. for 12 h to obtain the solid material.

[0064] The solid material consists of spherical particles less than 30 m with a low amount of sulfur residue impurities. The spherical morphology is preserved upon drying and heating to 900 C.

Comparison of Example 1 and Example 2: X-Ray Diffraction Data from Precipitation of Metal Sulfate with and without Titanium(IV) Oxysulfate

[0065] The X-ray diffractograms of two materials made by co-precipitation with and without TiOSO.sub.4 as described in EXAMPLE 1 and EXAMPLE 2 has been compared. The comparison revealed two important discoveries related to this invention. The first is that the material made by co-precipitation with TiOSO.sub.4 did not reveal any diffraction peaks related to TiO.sub.2, meaning that the co-precipitated Ti is in the form of very small or amorphous crystallites. The second is that the metal carbonate crystallites observed in the diffractogram (peaks matching Rhodochrosite) are much wider and less pronounced in the material with Ti compared to than in the material without Ti. This means that the crystalline domains of the metal carbonate phase are much smaller in the material with Ti compared to the material without Ti. These two discoveries serve to emphasize the homogeneous distribution of titanium that can be achieved with this invention.

Example 3

Precipitation of Titanium(IV) Oxysulfate and Metal Sulfate with Hydroxide

Comparative Example

[0066] A material with the proposed formula Ni.sub.aMn.sub.bMg.sub.cTi.sub.1-a-b-c(OH).sub.2 (with 0<a+b+c<1) can be synthesized by an aqueous co-precipitation process in a continuous stirred tank reactor (CSTR) (see EXAMPLE 1 for further details).

[0067] In this example, specific molarities, temperatures and CSTR parameters are mentioned, but experiments indicate a larger process window allowing similar materials to be synthesized with variations of these parameters.

[0068] In this example, a 1.35 L CSTR is initially filled with distilled water corresponding to 20 vol. % of the reactor and adjusted to a pH of 8 by adding appropriate amounts of NaOH.

[0069] A metal salt solution comprising Ni, Mn, Mg and Ti with a total concentration of 2.2 M (can be 0.1 M up to solubility limit for the metal salts), is prepared by dissolving appropriate amounts of NiSO.sub.4, MnSO.sub.4, MgSO.sub.4 and TiOSO.sub.4 in deionized water.

[0070] The metal salt solution is then pumped into a CSTR. In order to precipitate the metal cations, a 7.6 M basic solution of NaOH is simultaneously pumped separately into the CSTR. The addition of extra base in the form of increased flow of the NaOH feed can be employed to compensate for the acidity of the TiOSO.sub.4.

[0071] No chelating agent such as ammonium hydroxide or ammonium carbonate is required.

[0072] The solution is stirred at 450 rpm and the temperature of the solution is maintained at 70 C. by circulating hot water through a jacket in the CSTR.

[0073] The total feed flow rate is adjusted to 400 mL/hour assuring an average residence time (reactor volume divided by the total flow rates) of a little over 3 hours in the CSTR.

[0074] At the initial stage of the co-precipitation reaction, irregular secondary particles from the agglomeration of primary precipitated structures were formed. Even after an extended number of dwell times, these irregular particles did not completely change into spherical particles.

[0075] The resulting liquid dispersion that overflowed from the CSTR is feed into another reactor for an aging step, which is kept at the same reaction conditions as the CSTR.

[0076] Finally, the solid precipitate can be collected by filtration, washing and drying at 110 C. for 12 h to obtain the solid material.

[0077] The solid material consists of a mixture of spheroidal and irregular particles less than 10 m with a high amount of sulfur residue impurities. The morphology is preserved upon drying but assembles into larger irregular agglomerates upon heating to 900 C.

Example 4

Precipitation of Titanium(Ill) Chloride and Metal Nitrate with Carbonate

Comparative Example

[0078] A material with the proposed formula Ni.sub.aMn.sub.bMg.sub.cTi.sub.1-a-b-c(CO.sub.3).sub.x(OH).sub.2-2x (with 0<a+b+c<1 and 0<x1) can be synthesized by an aqueous co-precipitation process in a continuous stirred tank reactor (CSTR) [See EXAMPLE 1 for details].

[0079] In this example, specific molarities, temperatures and CSTR parameters are mentioned, but experiments indicate a larger process window allowing similar materials to be synthesized with variations of these parameters.

[0080] In this example, a 0.5 L CSTR is initially filled with distilled water corresponding to 20 vol. % of the reactor and adjusted to a pH of 9 by adding appropriate amounts of NaOH.

[0081] Two separate metal salt solutions are prepared. The first comprising Ni, Mn, and Mg with a total concentration of 1.38 M (can be 0.1 M up to solubility limit for the metal salts), is prepared by dissolving appropriate amounts of Ni(NO.sub.3).sub.2, Mn(NO.sub.3).sub.2, and Mg(NO.sub.3).sub.2 in deionized water. The second comprising Ti in a concentration of 1.3 M (can be 0.1 up to solubility limit for the metal salts) is prepared by dissolving appropriate amounts of TiCl.sub.3 in deionized water.

[0082] The two metal salt solutions are then simultaneously pumped into a CSTR. In order to precipitate the metal cations, a 5.87 M basic solution of Na.sub.2CO is simultaneously pumped separately into the CSTR.

[0083] No chelating agent such as ammonium hydroxide or ammonium carbonate is required.

[0084] The solution is stirred at 900 rpm, and the temperature of the solution is maintained at 50 C. by circulating hot water through a jacket in the CSTR.

[0085] The total feed flow rate is adjusted to 240 mL/hour assuring an average residence time (reactor volume divided by the total flow rates) of around 2 hours in the CSTR.

[0086] At the initial stage of the co-precipitation reaction, irregular secondary particles from the agglomeration of primary precipitated structures were formed. Even after an extended number of residence times, these irregular particles did not completely change into spherical particles.

[0087] The resulting liquid dispersion that overflowed from the CSTR is feed into another reactor for an aging step, which is kept at the same reaction conditions as the CSTR.

[0088] Finally, the solid precipitate can be collected by filtration, washing and drying at 110 C. for 12 h to obtain the solid material. Upon filtration it is noticed that the mother liquor has a strong green hue indicating that not all the metals could be precipitated under these conditions.

[0089] The solid material consists of irregular particles less than 10 m.

Example 5

Preparing a Positive Electrode Material for a Na-Ion Battery

Embodiment of the Invention

[0090] To describe a further aspect of the invention, two positive electrode material for Na-ion batteries were prepared using the solid material resulting from EXAMPLE 1 and EXAMPLE 2 in order to compare their electrochemical performance.

[0091] The solid material from EXAMPLE 1 comprising titanium as well as a metal carbonate comprising Ni, Mn and Mg was mixed thoroughly with a Na.sub.2CO3 slurry. The Na.sub.2CO3 slurry was prepared by paint-shaking Na.sub.2CO.sub.3 in pure ethanol with zirconia balls in the ratio of Na.sub.2CO.sub.3 to zirconia balls of 1:5 by weight for 30 min. The mixture was dried in a large Petri-dish in a fumehood under constant agitation and then heat treated at 900 C. for 8 hours in air, thereby partly or fully decomposing the carbonates of the mixture forming a first layered oxide (LO-1). The first layered oxide comprises a mixture of layered phases with an undetectable amount of rock-salt impurity phase.

[0092] For the solid material from EXAMPLE 2 comprising only Ni, Mn, and Mg carbonate was mixed thoroughly with a TiO.sub.2Na.sub.2CO3 slurry. The TiO.sub.2Na.sub.2CO.sub.3 slurry was prepared by paint-shaking TiO.sub.2 and Na.sub.2CO.sub.3 in pure ethanol with zirconia balls in the ratio of TiO.sub.2+Na.sub.2CO.sub.3 to zirconia balls of 1:5 by weight for 30 min. The mixture was dried in a large Petri-dish in a fumehood under constant agitation and then heat treated at 900 C. for 8 hours in air, thereby partly or fully decomposing the carbonates of the mixture forming a second layered oxide (LO-2). The second layered oxide comprises a mixture of layered phases with a very small amount of rock-salt impurity phase (<1 wt. %).

[0093] Electrode slurries were prepared by mixing the first and second layered oxides (A) originating from EXAMPLE 1 and EXAMPLE 2, respectively, as described above with Poly(vinylidene fluoride-co-hexafluoropropylene) (B) as binder and TimCal SuperC65 carbon black (C) as conductive additive in N-Methyl-2-pyrrolidone (NMP) in the ratio A:B:C of 80:10:10. Using a doctor blade, the slurries were distributed onto Al-foil and dried at 80 C. The dry electrode sheets were then cut into circular disks used for the assembly of CR2032 type coin cells employing 0.5 M NaClO.sub.4 as electrolyte and Na-metal as the negative electrode. The electrochemical performance of the first layered oxide LO-1 (originating from EXAMPLE 1) is superior to the second layered oxide LO-2 (originating from EXAMPLE 2).