Spherical metal mixed hydroxides and process for the production thereof

Abstract

The present invention relates to spherical metal mixed hydroxides, a process for production thereof and their use as precursors for cathode active materials of Li-ion / polymer batteries.

Description

[0001] Spherical mixed metal hydroxides and processes for their preparation

[0002] The present invention relates to spherical mixed metal hydroxides, processes for their preparation and their use as precursors for cathode active materials of Li-ion / polymer batteries.

[0003] Li-ion / polymer batteries (LIBs) are primarily used in portable devices with high energy requirements, such as mobile phones, tablets, laptops, and power tools. Recently, their importance has increased further in the context of advancing electromobility. They serve as energy storage devices in electric cars, e-bikes, and hybrid vehicles. In the future, demand for LIBs will intensify further as electromobility expands and demand for electric vehicles increases.

[0004] What all materials used in LIBs have in common is that, in addition to their limited availability, their complex extraction process has been criticized, which usually involves massive interference with the natural environment and the water resources of the mining regions. Therefore, the focus for some time has been on developing effective processes for recovering the valuable metals contained in LIBs. The aforementioned multiplication of demand will not be able to be met solely from primary raw material sources of the various valuable metals in the future, both for reasons of availability and sustainability. In addition to lithium itself, this primarily applies to nickel and cobalt, and to a limited extent, manganese for environmental reasons, which are used as the main components of LIB cathode materials.

[0005] The state of the art already describes a number of processes for reprocessing used LIBs.

[0006] US 2013 / 0302226 describes a method for recycling batteries, comprising: producing a solution of battery materials from spent cells; precipitating impurities from the produced solution; adjusting the solution to achieve a predetermined ratio of desired materials; and precipitating the desired material in the predetermined ratio to form cathode material for a new battery with the predetermined ratio of the desired transition metals. US 2017 / 0077564 discloses a method in which the elements Co, Ni, Al, and Mn are extracted from used lithium-ion batteries. Depending on the respective proportion of the elements, further raw materials can be added to achieve a desired ratio of the elements.

[0007] A common feature of the presented processes is that the process involves the introduction of significant amounts of sodium, which must be separated and disposed of at the end of the process. Initial approaches to processing without the use of sodium are described, for example, in "A novel closed loop process for recycling spent Li-ion battery cathode materials," published in International Journal of Green Energy, 18: 15, 1597-1612. In this article, J. Zhang et al. present an approach in which LiOH and U2CO3 are used as precipitation reagents instead of the commonly used NaOH and Na2CCh. Any U2SO4 produced is recovered as LiOH and H2SO4 at the end of the recycling process by electrolysis.

[0008] EP 4023610 describes a wet synthesis process for the production of NCMA precursors with a high nickel content. Small NCMA crystal seeds are first continuously produced in a first reactor using a top-feed mode. Their particle growth is then stimulated in a second reactor using a dual-feed mode until the desired particle size is reached.

[0009] US 11142466 describes a process for producing cathode materials for lithium-ion batteries, in which a metal sulfate is reacted with LiOH, optionally in the presence of a chelating agent, to form the corresponding hydroxide, whereby NaOH can also be used instead of LiOH.

[0010] EP 3916857 discloses Ni-Co-Al composite hydroxide composed of secondary particles aggregated from primary particles containing Ni, Co, and Al. The Na content of these hydroxides is less than 0.0005 wt%.

[0011] EP 3642160 relates to a ß-nickel(II) hydroxide doped with Al and Co ions. The Na content of these hydroxides is 23 ppm and their tap density is 1.97 g / cm 3 specified.

[0012] CN 102432070 discloses LiMn2Ü4 with a tap density of 2.1 to 2.4 g / cm 3 and a sodium content of < 10 ppm. However, the cathode materials obtained in this way, or the precursor compounds obtained from recycling processes, usually mixed hydroxides or carbonates, often lack sphericity. However, this, along with chemical purity, is a prerequisite for high packing densities and thus high energy densities in the battery.

[0013] There is therefore still a need for cathode materials suitable for use in LIBs for high-performance applications. The present invention seeks to address this need and provide suitable materials and methods for their production.

[0014] It was surprisingly found that this task is solved by a mixed metal hydroxide with spherical morphology and a low sodium content.

[0015] A first subject matter of the present invention is therefore a spherical mixed metal hydroxide as a cathode precursor material for batteries, wherein the mixed metal hydroxide is characterized by a sodium content of 250 ppm or less, wherein the mixed metal hydroxide comprises or consists of a mixture of at least two metals, preferably three, which are selected from the group consisting of Ni, Mn, Co and Al.

[0016] The ppm values ​​refer to the total weight of the mixed metal hydroxide. The sodium content in the mixed metal hydroxide can be determined, for example, using atomic absorption spectrometry.

[0017] In the context of the present invention, the term "metal", unless otherwise stated, includes the metal in all its oxidation states.

[0018] In the context of the present invention, the term "spherical" describes the morphology of the powder.

[0019] In the conventional precipitation of mixed hydroxides by reacting metal salt solutions with sodium hydroxide solution, high Na contents can pose a problem, especially in compact, larger spherical particles, where the sodium ions cannot be easily leached from the fine pores of the particles. To counteract this problem, the precipitation of the mixed hydroxides could be carried out with LiOH instead of NaOH, as already proposed in the prior art. However, even with this precipitation method, it must be ensured that the particles are obtained in a sufficiently spherical shape.

[0020] For use in LIBs, powders with a spherical morphology are particularly preferred, as they are also characterized by low levels of impurities such as sodium. Surprisingly, it was discovered that mixed metal hydroxides, which combine the advantages of a spherical morphology and a low sodium content and are thus particularly well suited as precursors for the active materials in Li-ion / polymer batteries (hereinafter referred to as LIBs), can actually be produced from the corresponding mixed metal salt solutions by reaction with LiOH.

[0021] Accordingly, an embodiment is preferred in which the sodium content of the mixed metal hydroxide is 100 ppm or less, particularly preferably 50 ppm or less, in particular 10 ppm or less, especially 5 ppm or less, or 0.5 ppm or less.

[0022] In a preferred embodiment, the mixed metal hydroxide according to the invention has a Na content of 0.01 ppm or more, preferably 0.05 ppm or more.

[0023] For use as precursors for cathode materials in LIBs, NCM (NiCoMn) and NCA (NiCoAl) mixed hydroxides or mixtures thereof are primarily used. Therefore, an embodiment in which the metal mixed hydroxide has the general formula M (w) (OH) w -2aOa, with M = NixCo y MnzAli-(x+y+z), where 0 < x < 1; 0 < y < 1; 0 < z < 1; and 0.8 < (x+y+z) < 1, w indicates the average oxidation state of the metal and 0 < a < 1.

[0024] Furthermore, an embodiment is preferred in which 2 < w < 3+z. Also preferred is an embodiment in which 2 < w < 3, particularly preferably 2 < w < 3-x, and very particularly preferably 2 < w < 3-(x+y+z).

[0025] A particularly preferred embodiment is characterized in that 0 < a < 1-x and especially 0 < a < l-(x+y+z).

[0026] The given formulas and the ranges of the indices are not to be understood as a limitation of the inventive concept. For example, for a typical NCA composition with M = Nio,8Coo,i5MnoAli- (o,8o+o,i5+o), the skilled person would complete the formula to Nio,8Coo,i5Alo,o5(OH)i,9sOo,o5. In this case, the Al would be 3+ -ion ​​fits perfectly into the crystal lattice of the M 2+ -ions in the mixed hydroxide. While above and below the M 2+ -Layers for each M 2+ -ion ​​is an OH'-ion, is at the position where the Al 3+ -ion, an OH'-ion by a 2-valent O 2'-ion. However, the aluminum can also be present separately as AlOOH or even Al(OH)3, as long as there is an intimate mixture of the primary crystallites at the microscopic level, the sodium content is within the range according to the invention, and the powder particles have a sufficiently spherical shape. What has just been said applies not only to Al but also, for example, to Co and Mn, which can easily be oxidized to CoOOH and MnOOH by complete or partial oxidation, for example, with incomplete exclusion of air. In the case of manganese, even 2 oxide ions per Mn ion would be possible in the common crystal lattice if it is oxidized to the tetravalent oxidation state. However, even a precipitation of manganese dioxide MnO2 at the microscopic level would not impair the inventive character of the particles as long as there is a low Na content with sufficient sphericity.

[0027] The following are some examples of compositions, without any limitation. Those skilled in the art can easily derive further examples from them, for example, by interpolation or using the above definition formulas. In addition to their low sodium content, the metal mixed hydroxides according to the invention are characterized primarily by their sphericity, which makes them particularly suitable for use in high-performance batteries. Sphericity is a parameter that indicates the extent to which the morphology of the powder particles approximates the shape of a sphere, with a sphericity of 1 corresponding to a sphere. The metal mixed hydroxides according to the invention are characterized particularly by the spheroidal shape of the particles, whose shape factor has a value of greater than 0.7, particularly preferably greater than 0.9, particularly preferably greater than 0.95, particularly preferably from 0.98 to 1.

[0028] The shape factor of the particles can be determined from SEM images of the powders according to the method described in US 5476530, columns 7 and 8 and Figure 5. The shape factor is determined by evaluating the particle circumference and the particle area and determining the diameter derived from the respective size. The diameters mentioned are derived from the v = U / 7i d A = (44 / 7r)^ 2

[0029] The shape factor of the particles f is derived from the particle circumference U and the particle area A according to:

[0030] In the case of an ideal spherical particle, dA and du are equal and the form factor would be exactly one.

[0031] To enhance the performance and properties of LIBs, various dopants can be added to the cathode material. Therefore, an embodiment is preferred in which the mixed metal hydroxide according to the invention further comprises dopants. These can originate in particular from the alkaline earth group, the rare earths, or other subgroups; they are preferably selected from the group of elements Mg, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, and W. Other main group elements such as Sn can also be included as dopants. Thus, the invention provides embodiments in which the Al is completely or partially replaced by dopants.

[0032] REPLACEMENT SHEET (RULE 26) The performance levels expected and required from batteries today represent a material challenge. To achieve the highest possible capacities, it has proven advantageous to use powders with the most spherical morphology possible, thus achieving a high packing density. The tap density of the material has proven to be a good measure of the subsequent packing density. Therefore, an embodiment of the mixed metal hydroxide according to the invention is preferred in which the mixed metal hydroxide has a tap density of 1.5 g / cm 3 or more, preferably 1.8 / cm 3 or more, particularly preferably 2.0 g / cm 3 or more and in particular 2.2 g / cm 3 or more, determined according to ASTM 527.

[0033] A further subject of the present invention is a process for preparing the mixed metal hydroxides according to the invention, the process comprising: a) providing a solution comprising MSC; b) adding LiOH in the presence of NH3 to obtain the mixed metal hydroxide and U2SO4, where M stands for a mixture of at least two metals selected from the group consisting of Ni, Mn, Co and Al.

[0034] In an alternative embodiment, the mixed metal hydroxide according to the invention is preferably prepared by a) providing a solution comprising Al2(SO4)3; b) introducing the solution provided in step a) into a solution comprising LiOH; c) providing a further solution comprising (Ni,Co,Mn)SO4; d) combining the solution obtained in step b) in the presence of NH3 with the solution provided in step c) in the reactor to obtain the mixed metal hydroxide and U2SO4, preferably continuously; and e) separating off the mixed metal hydroxide thus obtained.

[0035] In the context of the present invention, the skilled person understands the term (Ni,Co,Mn)SO4 to mean a mixed sulfate comprising at least two, preferably three, of Ni, Co, and Mn. The Al2(SO4)3 solution used in this embodiment reacts when mixed with the LiOH solution to form lithium aluminate LiAI(OH)4 and U2SO4 according to the following equation:

[0036] 0.5 LiAl(OH)4+ 1.5U2SO4

[0037] Particularly preferably, the lithium aluminate can also be prepared by dissolving aluminum hydroxide in LiOH solution according to the equation:

[0038] Providing the aluminum as lithium aluminate offers the advantage that the aluminum is incorporated particularly evenly into the lattice of the mixed metal hydroxides and does not precipitate separately as aluminum hydroxide.

[0039] Regardless of which variant of the process is preferred, the solvent for preparing the solutions in the process according to the invention can be selected as required, although aqueous solvents, in particular water and water-alcohol mixtures, are preferred.

[0040] The process according to the invention can be operated in batch mode as well as continuously or semi-continuously. The process according to the invention is preferably operated semi-continuously or continuously. A semi-continuous process differs from a continuous process in that the product is continuously produced, but there is no continuous removal of the product. In this way, for example, the solids concentration in the production process can be increased, which has a positive influence on obtaining powder particles that are as spherical as possible.

[0041] In particular, in order to obtain powder particles that are as spherical as possible and to achieve the highest possible sphericity, it has proven advantageous in the process according to the invention to operate at comparatively high solid concentrations. Without being bound to any particular theory, it is assumed that the collisions and friction experienced by the particles among themselves can increase their sphericity.

[0042] Therefore, an embodiment of the present invention is preferred in which the process is carried out at a solids concentration of 50 g / l or more, preferably 200 g / l or more, particularly preferably 400 g / l or more, especially 600 g / l or more.

[0043] The advantageous solids concentration of the process according to the invention can be achieved, for example, by uniformly concentrating the resulting suspension of mixed metal hydroxide, for example by at least partially removing the mother liquor during precipitation. Therefore, an embodiment in which the process according to the invention is carried out with continuous separation of a portion of the mother liquor is preferred. In the context of the present invention, "mother liquor" refers to the liquid from which the mixed metal hydroxide is separated.

[0044] The separation of a portion of the mother liquor can be achieved using various methods. In the context of the present invention, separation using a static inclined clarifier has proven particularly advantageous, as this allows a further increase in the sphericity of the obtained mixed metal hydroxide to be achieved. Therefore, an embodiment in which the partial separation of the mother liquor takes place using an inclined clarifier is preferred.

[0045] In addition to the solids concentration, the morphology of the powder can also be influenced by the concentration of LiOH and NH3. In a preferred embodiment, the LiOH concentration is preferably 0.01 to 4 g / l, preferably 0.1 to 4 g / l, particularly preferably 0.1 to 2 g / l, in particular 0.3 to 2 g / l. Furthermore, an embodiment is preferred in which the NH3 concentration is 2 to 20 g / l, preferably 5 to 20 g / l, particularly preferably 5 to 15 g / l. The concentration data refer in each case to the volume used.

[0046] The present invention further provides a spherical mixed metal hydroxide having a sodium content of 250 ppm or less, the mixed metal hydroxide being obtained by a process comprising the following steps: a) providing a solution comprising MSO b) adding LiOH in the presence of NH3 to obtain the mixed metal hydroxide and U2SO4, where M is a mixture of at least two, preferably three, metals selected from the group consisting of Ni, Mn, Co and Al. A continuous or semi-continuous process has proven advantageous, in which the individual reactant solutions are continuously introduced separately from one another into the stirred suspension. In continuous operation, the mixed metal hydroxide is continuously removed, whereas in semi-continuous operation only the reactants are continuously added.

[0047] The present invention further provides a spherical mixed metal hydroxide having a sodium content of 250 ppm or less, wherein the mixed metal hydroxide is obtained by means of a process comprising the following steps: a) a solution comprising Al2(SO4)3 is provided; b) the solution provided in step a) is introduced into a solution comprising LiOH; c) a further solution comprising (Ni,Co,Mn)SO4 is provided; d) the solution obtained in step b) is combined in the presence of NH3 with the solution provided in step c) to obtain the mixed metal hydroxide and U2SO4; and e) the mixed metal hydroxide thus obtained is separated.

[0048] The mixed metal hydroxide according to the invention can be obtained during the processing of used LIB. In this case, an embodiment is preferred in which the solution comprising MSO4 or (Ni,Co,Mn)SO4 originates from a reprocessing process for used LIB.

[0049] One application envisaged for the metal mixed hydroxide according to the invention is its use as a precursor for cathode materials in LIBs. For this application, a specific ratio of the components of the metal mixed hydroxide is desired, which can vary depending on the battery type and nature of the application and determines the battery performance. In the nickel-cobalt-manganese mixtures (NCM) used in conventional LIBs, the metals are typically present in a ratio of 1:1:1. Recently, however, the trend has been towards nickel-enriched powders, in which the components are present in a ratio of Ni:Co:Mn of 6 / io: 2 / io: 2 / io, or even

[0050] 9 / io:°' 5 / io:°' 5 / io or intermediate forms such as 8 / io : 1 5 / io : 0 5 / io of them are present. The ratio of the constituents of the mixed metal hydroxide can advantageously be adjusted during its preparation process. Therefore, an embodiment is preferred in which the process further comprises a step in which the stoichiometry of the mixed metal hydroxide is adjusted. The stoichiometry can be adjusted either by adding the corresponding component(s) or by targeted partial separation.

[0051] In the context of the present invention, targeted separation to adjust the stoichiometric ratio is preferred, as this avoids the use of additional material and the associated disadvantages. This procedure is particularly advantageous because it can accommodate the transition from the previous cathode material, in which Ni, Co, and Mn are present in a ratio of 1:1:1, to the nickel-rich materials.

[0052] To increase the performance and properties of LIBs, various dopants can be added to the cathode material. Within the scope of the inventive process, it has proven advantageous to introduce these dopants, for example by co-precipitation, into the metal mixed hydroxide. Therefore, an embodiment of the inventive process is preferred in which further metals are added, preferably in the form of their sulfates. The further metals can originate from the alkaline earth group, the rare earths, or other subgroups, preferably selected from the elements Mg, Sc, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, and W. Other main group elements such as Sn can also be added as dopants. Dopants are preferably added to the sulfate solutions MSC and (Ni,Co,Mn)SO4.

[0053] According to the invention, the mixed metal hydroxide is obtained from the corresponding sulfates by reaction with LiOH, yielding U2SO4 as a byproduct. This U2SO4 can advantageously be used for further purposes. Preferably, the U2SO4 obtained in the process according to the invention is converted into LiOH and H2SO4 by electrolysis. Both are preferably returned to the reaction circuit, thus creating a closed process circuit. Membrane electrolysis is preferred for the electrolysis, in particular electrodialysis and especially electrodialysis with bipolar membranes. Multi-chamber electrolysis with a cation exchange membrane and an anion exchange membrane is particularly preferred.

[0054] Due to its sphericity and low sodium content, the metal mixed hydroxide according to the invention is particularly suitable for use in LIBs. The present invention therefore further relates to the use of the metal mixed hydroxide according to the invention as a cathode precursor material in the production of batteries, in particular LIBs.

[0055] The present invention is explained in more detail with reference to the following example, which should in no way be understood as a limitation of the inventive concept.

[0056] Example :

[0057] To produce spherical NCM material using LiOH as a precipitation reagent, 0.41 l / h of metal sulfate solution containing 10 g / l of metal sulfate salt solution containing 32.76 g / l nickel, 1.70 g / l manganese, and 1.83 g / l cobalt, as well as 0.31 l / h of a LiOH solution containing 98.7 g / l LiOH and 0.11 l / h of an NH3 solution containing 225 g / l NH3 were continuously added to a 10-liter stirred reactor. The reactor was thoroughly mixed using a stirrer at 500 rpm and maintained at a temperature of 50°C via a jacket heater. Approximately 0.87 l of suspension was removed from the reactor every hour within one minute via a dip tube to prevent sedimentation in the withdrawal tube. The reactor level therefore exhibited a sawtooth profile over time, with the residence time characteristics close to those of fully continuous operation.

[0058] Figure 1 shows optical microscope images of the resulting mixed metal hydroxide after a residence time of 36 hours at 500x magnification (left) and 200x magnification (right). The spherical shape of the particles is clearly visible.

Claims

Patent claims 1. Spherical mixed metal hydroxide as cathode precursor material for batteries, characterized in that the mixed metal hydroxide has a sodium content of 250 ppm or less, wherein the mixed metal hydroxide comprises or consists of a mixture of at least two metals, preferably three, selected from the group consisting of Ni, Mn, Co and Al.

2. Metal mixed hydroxide according to claim 1, characterized in that the metal mixed hydroxide has the general formula M (w) (OH) w -2aOa, with M = NixCo y MnzAli-(x+y+z), where 0 < x < l; 0 < y < 1; 0 < z < 1; and 0.8 < (x+y+z) < 1, w indicates the average oxidation state of the metal and 0 < a < 1.

3. Metal mixed hydroxide according to at least one of the preceding claims, characterized in that the shape factor of the particles has a value of greater than 0.7, particularly preferably greater than 0.9, particularly preferably greater than 0.95, particularly preferably from 0.98 to 1.

4. Metal hydroxide according to at least one of the preceding claims, characterized in that the mixed metal hydroxide has 100 ppm or less, particularly preferably 50 ppm or less, very particularly preferably 10 ppm or less and especially 5 ppm or less or 0.5 ppm or less sodium.

5. Metal mixed hydroxide according to at least one of the preceding claims, characterized in that the metal mixed hydroxide has a tap density of 1.5 g / cm 3 or more, preferably 1.8 g / cm 3 or more, particularly preferably 2.0 g / cm 3 or more, in particular 2.2 g / cm 3 or more, determined according to ASTM 527.

6. A process for the preparation of spherical mixed metal hydroxides according to at least one of the preceding claims, the process comprising: a) providing a solution comprising MSC; b) adding LiOH in the presence of NH3 to obtain the mixed metal hydroxide and U2SO4, where M represents a mixture of at least two metals selected from the group consisting of Ni, Mn, Co and Al.

7. A process for producing spherical mixed metal hydroxides according to at least one of claims 1 to 5, characterized in that a) a solution comprising Al2(SO4)3 is provided; b) the solution provided in step a) is introduced into a solution comprising LiOH; c) a further solution comprising (Ni,Co,Mn)SO4 is provided; d) the solution obtained in step b) is combined in the presence of NH3 with the solution provided in step c) to obtain the mixed metal hydroxide and U2SO4; and e) the mixed metal hydroxide thus obtained is separated.

8. Process according to at least one of claims 6 to 7, characterized in that the process is operated semi-continuously or continuously.

9. Process according to at least one of claims 6 to 8, characterized in that the process is carried out with continuous separation of a portion of the mother liquor.

10. Process according to claim 9, characterized in that the separation of the mother liquor takes place via an inclined clarifier.

11. Process according to at least one of claims 6 to 10, characterized in that the process is carried out at a solids concentration of 50 g / l or more, preferably 200 g / l or more, particularly preferably 400 g / l or more, especially 600 g / l or more.

12. The method according to at least one of claims 6 to 11, characterized in that the method further comprises a step of adjusting the stoichiometry of the mixed metal hydroxide.

13. The process according to at least one of claims 6 to 12, characterized in that the process further comprises a step in which the resulting U2SO4 is converted into LiOH and H2SO4 by electrolysis.

14. Process according to claim 13, characterized in that LiOH and / or H2SO4 is returned to the reaction cycle.

15. Use of a mixed metal hydroxide according to at least one of claims 1 to 5 as a cathode precursor material for batteries, in particular Li-ion / polymer batteries.

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