Method for producing aqueous slurry and method for producing powdered hydroxides therefrom

Abstract

The present invention relates to a process for manufacturing an aqueous slurry comprising particles of hydroxide or oxyhydroxide of one or more elements, wherein the one or more elements comprise at least one of Ni, Co and Mn. The method comprises: feeding a stream of a metal salt solution comprising the one or more elements to a reactor vessel for a period of time; mixing the metal salt solution with an aqueous solution comprising one or more alkali metal hydroxides during the period of time, thereby precipitating the hydroxides of the one or more elements and forming an aqueous slurry comprising particles of the hydroxides or oxyhydroxides of the one or more elements; and wherein the metal salt solution has a flow rate expressed as a volume per unit time, wherein the metal salt solution has a concentration of the one or more elements expressed as moles per unit volume, and wherein a mathematical product of the flow rate and the concentration continuously increases during the time period.

Description

Technical Field

[0001] Generally speaking, the present invention relates to metal hydroxides which can be used as precursors for cathode active materials for secondary battery packs and methods for manufacturing the same. Specifically, but not exclusively, the present invention relates to a method for manufacturing an aqueous slurry of a hydroxide or hydroxy-oxide containing at least one or more metal elements, a method for manufacturing a powdery hydroxide or hydroxy-oxide therefrom, and the use of the aqueous slurry or the powdery hydroxide or hydroxy-oxide for manufacturing a positive electrode active material for a secondary battery pack. Background Art

[0002] Lithium ion secondary battery packs generally include a negative electrode (anode), an electrolyte, and a positive electrode (cathode), and the positive electrode contains a lithium-transition metal oxide as an active material capable of intercalating and desorbing lithium. The lithium-transition metal oxide is usually manufactured from a transition metal hydroxide, oxide, or hydroxy-oxide sequentially manufactured in a coprecipitation method, and the coprecipitation method discloses mixing a metal salt solution and an alkali solution in the presence of a complexing agent.

[0003] It is expected that the future lithium ion battery pack market will be increasingly dominated by automotive applications. To be competitive, battery packs for automotive applications must be produced at the lowest possible cost. A large part of the cost comes from the active material, and the cost of the precursor is reflected in the cost of the active material. Providing these precursors by more efficient and / or less expensive methods, ideally without compromising their quality, can help reduce costs and increase the market acceptance of lithium ion secondary battery packs.

[0004] In view of the above, there is a continuing need for further improvements in the method for manufacturing precursors. Summary of the Invention

[0005] The present invention aims to provide an improved method for preparing materials that can be directly / indirectly used as precursors for lithium transition metal cathode materials for positive electrodes subsequently.

[0006] From a first aspect, the present invention can provide a method for manufacturing an aqueous slurry of hydroxide or hydroxy-oxide particles containing one or more elements, wherein the one or more elements include at least one of Ni, Co, and Mn. The hydroxide or hydroxy-oxide particles can ultimately be used as precursors for lithium transition metal cathode active materials for positive electrodes. Such a method according to the present invention includes:

[0007] - Supplying a stream of an aqueous solution of a metal salt containing the one or more elements to a reactor vessel for a period of time,

[0008] - During the period of time, mixing the metal salt solution with an aqueous solution containing one or more alkali metal hydroxides and additionally optionally an aqueous solution of ammonia (NH3(水) ) Mixing, thereby precipitating hydroxides of said one or more elements and forming an aqueous slurry comprising particles of hydroxides or oxyhydroxides of said one or more elements,

[0009] wherein said metal salt solution has a flow rate expressed as volume per unit time, wherein said metal salt solution has a concentration of said one or more elements expressed as moles per unit volume, and wherein the mathematical product of said flow rate and said concentration continuously increases during said time period.

[0010] Hydroxide or oxyhydroxide particles of one or more elements according to the present invention have a composition that can be represented by the general formula: Me - O x (OH) 2-x where 0 ≤ x ≤ 2, and Me includes at least one of Ni, Co, and Mn, d, and possibly at least one other element such as impurities such as Na, S, etc.

[0011] Said time period can be represented as T1 - T2, which refers to the time course starting at time T1 (i.e., the start of said time period) and ending at time T2 (i.e., the end of said time period).

[0012] According to the present invention, the continuous increase in the mathematical product of the flow rate and the concentration helps the precipitated hydroxide to grow more efficiently to the target median particle size. In addition, it helps to improve the production capacity. The concentration of the fed metal salt solution can be expressed as, for example, mol / ml, mol / ml, and the flow rate, which can also be referred to as the feed rate in the context of the present invention, can be expressed as, for example, ml / hour, ml / h. Therefore, the mathematical product of the flow rate and the concentration can be expressed as, for example, mol / hour, mol / h. It can be understood that when the concentration of the fed metal salt solution remains constant, the flow rate will continuously increase during the time period T1 - T2. In other words, during the time period T1 - T2, at any given time point T x when, the flow rate r x will be greater than the flow rate r y at an earlier time point T y , i.e., r x > r y , T2 ≥ T x > T y ≥ T1.

[0013] Therefore, the present invention provides an improved method for the precipitation process of metal hydroxides used as precursors of cathode active materials. The precipitation process generally may include feeding an aqueous metal salt solution, a neutralizing agent such as an alkali metal hydroxide, and a complexing agent such as an ammonium ion donor into a reaction vessel while stirring, and carrying out a crystallization reaction.

[0014] According to the concept of the first aspect of the present invention, a second aspect of the present invention is also provided, which is a method for manufacturing powdery hydroxides or hydroxyoxides of one or more elements, wherein the method comprises: I) providing an aqueous slurry according to the first aspect of the present invention, II) separating the hydroxide or hydroxyoxide particles from the liquid fraction of the aqueous slurry, and III) drying the separated hydroxide or hydroxyoxide particles.

[0015] A third aspect of the present invention is also provided, which is the use of the aqueous slurry according to the first aspect of the present invention or the powdery hydroxide or hydroxyoxide according to the second aspect of the present invention for manufacturing a positive electrode active material for a secondary battery pack.

[0016] A fourth aspect of the present invention is also provided, which is a method for manufacturing a positive electrode active material by using the hydroxide or hydroxyoxide particles manufactured according to the first and second aspects of the present invention.

[0017] Various embodiments according to the present invention are disclosed in the claims and the specification. Unless otherwise clearly stated, the embodiments and examples described in the claims and the specification can be freely combined with each other. Throughout the description, if any numerical range is provided, unless otherwise clearly stated, the range also includes the endpoint values. Description of the Drawings

[0018] For further guidance, drawings are included to better understand the teachings of the present invention. In the drawings:

[0019] Figure 1 A schematic timeline of the time period T1 - T2 is shown;

[0020] Figure 2 A scanning electron microscope (SEM) image of the particles obtained from Example 1 is shown;

[0021] Figure 3 A graph showing the variation of the feed rate of the metal sulfate solution of the example with the reaction time is shown; and

[0022] Figure 4 A graph showing the variation of the median particle size of the precipitated hydroxide in the example with the reaction time is shown. Detailed Description of the Invention

[0023] In the following detailed description, preferred embodiments are described in detail to enable the practice of the present invention. Although the present invention is described with reference to these specific preferred embodiments, it should be understood that the present invention is not limited to these preferred embodiments. On the contrary, the present invention includes numerous alternatives, modifications, and equivalents, as will become apparent from considering the following detailed description and the drawings.

[0024] As used herein and in the claims, the term "comprising" should not be construed as limited to the manners listed thereafter; it does not exclude other elements or steps. It should be construed as specifying the presence of the stated features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components or groups thereof. Thus, the scope of the expression "a composition comprising components A and B" should not be limited to compositions consisting only of components A and B. This means that, for the purposes of the present invention, the only relevant components of the composition are A and B. Accordingly, the terms "comprising" and "including" encompass the more restrictive terms "consisting essentially of" and "consisting of".

[0025] As used herein and in the claims, the term "positive electrode active material" (also referred to as cathode active material) is defined as a material that is electrochemically active in the positive electrode or cathode. The active material should be understood as a material that is capable of capturing and releasing Li ions when subjected to a voltage change over a predetermined period of time.

[0026] As used herein, the term "positive electrode" is defined as a material that contains a positive electrode active material in addition to other components that are not electrochemically active (in particular conductive agents such as carbon black or binders such as PVDF).

[0027] As used herein, the term "NH 3(水) concentration" and the like mean the concentration of ammonia in an aqueous solution.

[0028] In a first aspect, the present invention relates to a method for manufacturing an aqueous slurry comprising hydroxide or oxyhydroxide particles of one or more elements, wherein the one or more elements include at least one of Ni, Co and Mn. The hydroxide or oxyhydroxide particles can ultimately be used as precursors for lithium transition metal cathode active materials for positive electrodes. Such a method according to the present invention comprises:

[0029] - feeding a stream of an aqueous metal salt solution comprising the one or more elements into a reactor vessel during a time period T1 - T2, the time period having a start time T1 and an end time T2,

[0030] - during the time period T1 - T2, mixing the metal salt solution with an aqueous solution comprising one or more alkali metal hydroxides and optionally also an aqueous solution of ammonia (NH 3(水) ), thereby precipitating the hydroxide of the one or more elements and forming an aqueous slurry comprising hydroxide or oxyhydroxide particles of the one or more elements,

[0031] The metal salt solution is supplied at a flow rate expressed as a volume per unit time, the metal salt solution has a concentration of the one or more elements expressed as moles per unit volume, and the mathematical product of the flow rate and the concentration continuously increases during the time period T1 - T2.

[0032] During the manufacturing process, the precipitated hydroxide may be partially oxidized, depending on the atmosphere of the manufacturing process. Thus, the aqueous slurry may contain oxyhydroxide. It should be noted that the atmosphere conditions are not critical for achieving the claimed invention.

[0033] According to the present invention, the continuous increase in the mathematical product of the flow rate and the concentration contributes to the more efficient growth of the precipitated hydroxide to the target median particle size. In addition, it contributes to an increase in production capacity. Further, according to the present invention, the controllability of supplying the metal element during the precipitation reaction is improved. For example, according to the present invention, the controllability of supplying the metal element is implemented in such a way that a constant growth rate of the median particle size of the hydroxide can be achieved. In other words, the precipitation process can be made more stable and more controllable.

[0034] In some embodiments, at the start T1 of the time period, the mathematical product of the flow rate and the concentration is non-zero. In other words, at the start T1 of the time period, neither the flow rate of the metal salt solution nor the concentration of the metal salt solution is zero.

[0035] It can be understood that with reference to Figure 1 , when the concentration of the metal salt solution fed into the reactor vessel is kept constant, the flow rate will continuously increase during the time period T1 - T2. In other words, during the time period T1 - T2, at any given time point T x , the flow rate r x will be greater than the flow rate r y at an earlier time point T y , i.e., r x > r y , T2 ≥ T x > T y ≥ T1. In some embodiments, the flow rate of the metal salt solution preferably continuously increases during the time period T1 - T2, regardless of whether the concentration of the fed metal salt solution is kept constant, as long as the mathematical product of the flow rate and the concentration continuously increases. In some embodiments, the function between time and the flow rate may be substantially non-linear.

[0036] In some embodiments, the mathematical product of the flow rate and the concentration at the end of the time period T2 is at least twice the mathematical product of the flow rate and the concentration at the start of the time period T1. Preferably, the said mathematical product at the end of the time period T2 is at least 2.5 times the said mathematical product at the start of the time period T1. More preferably, the said mathematical product at the end of the time period T2 is at least 3 times the said mathematical product at the start of the time period T1. The greater the said mathematical product at the end of the time period T2 compared to the said mathematical product at the start of the time period T1, the shorter the precipitation time required to achieve the target median particle size.

[0037] In some embodiments, the time period T1 - T2 continues until the target median particle size of the hydroxide or oxyhydroxide particles of the said one or more elements is obtained. In other words, the target median particle size of the hydroxide or oxyhydroxide particles is reached at the end of the time period T2. In some embodiments, the time period T1 - T2 is at least 8 hours, preferably at least 10 hours, so that a target median particle size between 7 and 12 microns can be achieved.

[0038] In some embodiments, the method according to the invention further comprises establishing or maintaining, during the time period T1 - T2, a pH value range of the aqueous slurry in the reactor vessel, the range being greater than or equal to 9.0 and less than or equal to 14.0. When growing particles in the precipitation reaction, a pH value above 14.0 may cause new particle nucleation rather than the growth of the particles present in the reactor vessel. A pH value below 9 may result in incomplete precipitation, thus affecting the efficiency of the process. To further optimize the reaction conditions, the pH value is more preferably greater than or equal to 10.0 and less than or equal to 13.5, where the pH value of the aqueous slurry is the pH value measured for a sample of the aqueous slurry at 20°C; even more preferably, the pH value is at most 12.2 and preferably at least 11.5, and most preferably at most 12.1 and at least 11.6, where the pH value of the aqueous slurry is the pH value measured for a sample of the aqueous slurry at 20°C. In some embodiments, the pH value is in the range of 10.5 to 12.0, preferably 11.0 to 12.0, within which the nucleation process of new nuclei can be prevented while ensuring the growth of the precipitated particles present in the reactor vessel. Controlling the pH value during the precipitation process can be carried out by adjusting the amount of the aqueous solution containing one or more alkali metal hydroxides supplied. As understood by those skilled in the art, the pH value can be measured by using a pH meter, such as a 780 Metrohm meter.

[0039] In some embodiments of the method according to the invention, during the time period T1 - T2, the aqueous slurry in the reactor vessel has a temperature of at least 45 °C and preferably at least 75 °C, more preferably at least or equal to 85 °C. Temperatures below 45 °C may result in a more porous structure of the precipitated hydroxide. In some embodiments, the temperature is at most 99 °C, preferably at most 95 °C, and more preferably at most 90 °C. Temperatures above 95 °C may increase the difficulty of processability. When the temperature is at least 75 °C, preferably at least or equal to 80 °C, more preferably at least or equal to 85 °C, the undesired cracking of hydroxide or oxyhydroxide particles can be prevented.

[0040] In some embodiments of the method according to the invention, per m 3 the aqueous slurry is mixed with a mixing energy of at most 40 kW, preferably per m 3 the aqueous slurry with a mixing energy of at most 35 kW. A mixing energy of more than 40 kW per m 3 may break hydroxide or oxyhydroxide particles into smaller fragments. In some embodiments, the mixing energy is at least 5 kW per m 3 of the aqueous slurry, preferably at least 10 kW per m 3 of the aqueous slurry. The disclosed mixing energy helps to obtain a homogeneous reaction mixture and avoid particle agglomeration.

[0041] In some embodiments of the method according to the invention, it further includes establishing or maintaining an NH 3(水) concentration of at least 1.0 g / l and at most 13.0 g / l in the reactor vessel during the time period T1 - T2. Establishing or maintaining means that an aqueous ammonia solution (NH 3(水) ) can be provided as a starting solution in the reaction vessel before the start T1 of the time period, and additionally or alternatively, an aqueous ammonia solution (NH 3(水) ) can be supplied to the reaction vessel during the time period T1 - T2. An NH 3(水) concentration below 1.0 g / l may lead to nucleation. When the particle size of the hydroxide precipitated in the reactor is relatively small (e.g., less than 4 μm or less than 3 μm), a higher NH 3(水) concentration, for example above 13.0 g / l, may lead to agglomeration, and thus in such cases, preferably the concentration of NH 3(水) is at least 1.5 g / l and at most 7 g / l, more preferably at least 1.5 g / l and at most 6 g / l, and most preferably at least 2 g / l and at most 4 g / l. On the other hand, when the particle size of the hydroxide precipitated in the reactor is relatively large (e.g., equal to or greater than 4 μm), the concentration of NH 3(水) can be towards the higher end within the range between 1.0 g / l and 13.0 g / l; for example, NH 3(水)The concentration can be at least 7 g / l and at most 13.0 g / l, preferably at least 10 g / l and at most 12.0 g / l to allow for slower growth of the particle size (i.e., slower precipitation), which results in a denser particle structure. As understood by the person skilled in the art, NH 3(水) The concentration can be measured by using a commercially available titrator such as a Metrhom 848 Titrino Plus.

[0042] In some embodiments of the method according to the invention, the one or more alkali metal hydroxides include NaOH, KOH, LiOH, CsOH and RbOH; preferably at least NaOH.

[0043] In some embodiments of the method according to the invention, the aqueous slurry comprising hydroxide or oxyhydroxide particles of one or more elements has a liquid fraction and a solid fraction, wherein a portion of the liquid fraction is removed from the reactor vessel during the time period, and wherein the solid fraction remains in the reactor vessel during the time period T1 - T2. This can achieve a narrow size distribution of the hydroxide or oxyhydroxide particles. A narrow size distribution means the span value of the hydroxide or oxyhydroxide, expressed as (D90 - D10) / D50, is generally in the range of <0.8.

[0044] The means for removing a portion of the liquid fraction (i.e., the mother liquor) of the aqueous slurry is not particularly limited. However, for example, a commercially available concentrator can be used to remove a portion of the liquid fraction, which can be connected to the reactor vessel and is capable of selectively removing a portion of the liquid from the reactor vessel.

[0045] In some embodiments of the method according to the invention, an aqueous slurry of seed particles is provided in the reactor vessel before the start T1 of the time period. Using seed particles instead of an in - situ seeding method can prevent further nucleation, which is not desirable as it may lead to the formation of small particles that tend to agglomerate, which in turn can change the production quality. Additionally, since more crystal surface becomes available as the reaction progresses, more material can be fed without the risk of nucleation. According to the invention, using a seed slurry in combination with the disclosed precipitation helps in the stable growth of hydroxides on the seeds without further nucleation and agglomeration, such that the aqueous slurry contains hydroxide or oxyhydroxide particles with a desired median particle size having a uniform distribution, and the hydroxide or oxyhydroxide particles have excellent sphericity. When used as a precursor for a cathode material, the excellent sphericity of the hydroxide or oxyhydroxide particles according to the invention will be retained in the cathode material. In other words, the cathode material also has excellent sphericity. Sphericity is related to a higher tapped density.

[0046] In some embodiments, the seed particles are particles of a hydroxide or oxyhydroxide of at least one metal element, preferably the at least one metal element comprises at least Ni. According to the present invention, the (multiple) metal elements for the seed particles and for the hydroxide or oxyhydroxide particles can be different, which provides further flexibility for implementing the method of the present invention.

[0047] In some embodiments of the method according to the present invention, the seed particles have a median particle size D’50, and at the end of the time period T2, the hydroxide or oxyhydroxide particles of the one or more elements have a median particle size D50, where the ratio D50 / D’50 is at least 2.00 and preferably at least 3.00. The larger the D50 / D’50 ratio, the better the sphericity of the hydroxide or oxyhydroxide particles that can be obtained. In some embodiments, D’50 is at least 0.70 μm and at most 3.00 μm, and D50 is at least 3.0 μm and preferably at most 5.0 μm. In some embodiments, D’50 is at least 3.0 μm and at most 5.0 μm, and D50 is at least 8.0 µm. In some embodiments, D50 is at most 15.0 µm, preferably at most 13.0 µm, and more preferably at most 12.0 µm.

[0048] In some embodiments, D’50 is at least 0.70 μm and at most 4.00 μm, and D50 is at least 4.0 μm and preferably at most 18.0 μm. In some embodiments, D’50 is at least 4.0 μm and at most 8.0 μm, and D50 is at least 9.0 µm. In some embodiments, D50 is at most 20.0 μm.

[0049] The method for determining the particle size distribution is not particularly limited. However, for example, the size distribution can be determined based on the integral volume values measured using a laser diffraction and scattering type particle size analyzer. As the average particle size, the percentile values D10, D50, and D90 can be used as the values of the particle diameters at 10%, 50%, and 90% respectively in the cumulative distribution, and the span value (D90 - D10) / D50 can be used as a measure of the distribution range.

[0050] In some embodiments, where an aqueous slurry of seed particles is provided in a reactor vessel, the concentration of the one or more elements in the metal salt solution remains constant during the time period T1 - T2, where the flow rate (in L / h) of the metal salt solution at time t within the time period T1 - T2 is represented by the following formula:

[0051]

[0052] where m1 is the mass (grams) of the seed particles provided in the reactor vessel, G(t) is the growth rate (μm / h) of the hydroxide or oxyhydroxide particles at the said time t, where the value of G(t) is non-zero, Δt is the time period T1 - T2 expressed in hours (h), D’50 is the median particle size of the seed particles in μm, and M Me is the molar mass (grams / mole) of the said one or more elements, c Me is the concentration (grams / L) of the said one or more elements in the metal salt solution, and M Me(OH)2 is the molar mass (grams / mole) of the hydroxide or oxyhydroxide of the said one or more elements. Preferably, the value of G(t) is less than or equal to 2 μm / h, more preferably less than or equal to 1.5 μm / h. A smaller value of G(t) can contribute to a lower porosity.

[0053] In some embodiments, the value of G(t) is less than or equal to 1.0 µm / h. In some embodiments, the value of G(t) is less than or equal to 0.5 µm / h. In some embodiments, the value of G(t) is less than or equal to 0.1 µm / h.

[0054] The value of G(t) can vary depending on the embodiment. In some embodiments, the value of G(t) varies during the time period T1 - T2.

[0055] The upper limit of G(t), i.e., the maximum growth rate of the hydroxide or oxyhydroxide particles, may depend on, for example, the characteristics of the feed pump and the characteristics of the removal system for the liquid portion (i.e., the mother liquor) in the reaction mixture / aqueous slurry.

[0056] In some embodiments, the value of G(t) in the formula does not change during the time period T1 - T2, where the flow rate of the metal salt solution is continuously increased according to Formula 1, and the growth rate of the hydroxide or oxyhydroxide particles in the slurry is constant during the time period T1 - T2. Thus, by continuously increasing the flow rate of the metal salt solution, a constant growth rate of the median particle size of the hydroxide or oxyhydroxide can be obtained. In other words, it may be possible to make the precipitation process more stable and more controllable. This is especially true when the target median particle size is large (such as at least 10 μm). While other factors remain constant, with the continuous increase in the flow rate, compared to a process that is otherwise similar but in which the metal salt solution is fed at a constant rate throughout the precipitation process, the precipitation time can be saved by up to half or even a quarter.

[0057] In some embodiments of the method according to the present invention, the said one or more elements in the hydroxide or oxyhydroxide particles include:

[0058] - Ni with a content x, where 5.0 mol% ≤ 99 mol%,

[0059] - Co with a content of y, where 0 ≤ y ≤ 30.0 mol%, and

[0060] - Mn with a content of z, where 0 ≤ z ≤ 85.0 mol%,

[0061] - Al with a content of q, where 0 ≤ q ≤ 10.0 mol%, and

[0062] - One or more additional elements with a content of r, where the additional elements are elements from the list of B, Ba, Ca, Ce, Cr, Fe, La, Mg, Mo, Nb, Si, Sr, Ti, Y, V, W, Zn, Na, S, and Zr, where 0 ≤ r ≤ 5.0 mol%, and

[0063] where x, y, z, q, and r are contents expressed in mol% relative to the total molar content of the one or more elements in the hydroxide or hydroxy - oxide particles, and where x + y+ z + q + r = 100 mol%; preferably, where x ≥ 60.0 mol%, where z ≤ 30.0 mol%, and where (y + z) ≥ 1.0 mol%, more preferably, where x ≥ 70.0 mol%, and where preferably x ≥ 80.0 mol; or where z ≥ 50.0 mol%, and preferably where r ≤ 3.0 mol%; and / or where z ≥ 60.0 mol%; and / or where z ≤ 90.0 mol%, preferably where z ≤ 85.0 mol%. The values of x, y, z, q, r are measured by an inductively coupled plasma (ICP) method. It is understood that the expression ≥0 includes the absence of the element.

[0064] According to the present invention, there is also provided a method for manufacturing powdery hydroxide or hydroxy - oxide of one or more elements, where the method comprises: I) providing an aqueous slurry according to the method of the present invention described above, II) separating the hydroxide or hydroxy - oxide particles from the liquid fraction of the aqueous slurry, and III) drying the separated hydroxide or hydroxy - oxide particles.

[0065] During the manufacturing process, the hydroxide or hydroxy - oxide particles from the aqueous slurry may be further partially oxidized.

[0066] For example, a precursor containing Ni, Co, and Mn in a molar ratio of x:y:z can be prepared in a mixed form by a precipitation reaction as follows: (1) Provide a seed slurry, which can be accomplished by continuous precipitation, followed by batch precipitation of the mixed hydroxide in a reactor having NaOH and a mixed metal salt at a controlled pH according to the present invention as described, (2) Remove the precursor suspension and filter, (3) Dry the filtered wet cake. In step (1), the mixed salt can be a mixed sulfate, and the pH can generally be between 11 and 12. Efficient precursor drying is typically carried out at about 100 °C for a certain time to remove most of the moisture. The typical moisture content after drying is less than 1 wt%, and can be measured by the well-known Karl Fischer titration method (ASTM D6869) at 250 °C. Before drying, the precursor has a pure or ideal hydroxide crystal structure (with space group P-3m1).

[0067] In the method according to the present invention, the drying of the hydroxide or oxyhydroxide precursor can be carefully carried out under well-defined conditions such as temperature, gas atmosphere, and time, which can interact with each other. For example, a higher drying temperature requires less time to obtain the desired product, especially for large-scale production.

[0068] The dried hydroxide or oxyhydroxide particles according to the present invention, i.e., powdered hydroxide or oxyhydroxide, can be used to manufacture a positive electrode active material. The powdered hydroxide or oxyhydroxide can be mixed with a lithium source to obtain a mixture. The mixture is sintered at a temperature between 650 °C and 1000 °C. Optionally, a heat treatment can be carried out at a temperature between 105 °C and 750 °C before mixing.

[0069] Therefore, the present invention also relates to the use of an aqueous slurry containing hydroxide or oxyhydroxide particles obtainable by the method according to the first aspect of the present invention and powdered hydroxide or oxyhydroxide obtainable by the second aspect of the present invention for manufacturing a positive electrode active material for a secondary battery pack.

[0070] Examples

[0071] The present invention will be further illustrated below with reference to some examples and comparative examples. In all examples, the pH value refers to the value measured at a temperature of 20 °C. Furthermore, in all processes of the examples, unless otherwise stated, a reducing atmosphere is ensured by applying a nitrogen gas flow to the reactor vessel during the precipitation reaction.

[0072] Measurement method used in the examples

[0073] pH Analysis

[0074] The pH value of the sample was measured using a 780 Metrohm meter calibrated with pH 7 and pH 13 standards. The sample was cooled to 20 °C, and the pH was measured from the sample by lowering the pH electrode into the sample and waiting for the pH reading to stabilize.

[0075] NH 3(水) Concentration analysis

[0076] The NH concentration was measured from the reactor sample by end-point titration using a Metrhom 848 Titrino Plus instrument. 3(水) One milliliter of the sample solution was added to the titration vessel. 30 - 40 ml of deionized water and 1 ml of 1M NaOH were added. The sample was titrated to the end point with 0.1M HCl.

[0077] Solid content analysis

[0078] To determine the solid content of the precipitated hydroxide in the aqueous slurry, a sample taken from the aqueous slurry (the "reaction mixture" in the examples) was thoroughly mixed, and 10 - 30 ml of the mixed sample was pipetted onto a filter paper and then filtered onto a washed and weighed 0.8 µm membrane. The filtered membrane was rinsed with DI water, then dried and the weight of the dried membrane was measured. The solid content was calculated therefrom and expressed as the weight of dry hydroxide per liter of aqueous slurry (g / l).

[0079] Surface area analysis

[0080] The specific surface area (SA) of the example samples was measured using the Brunauer - Emmett - Teller (BET) method with a Quantachrome Monosorb. The powder sample was placed in the sample tube and heated at 90 °C for 2 hours under nitrogen (N2) before measurement to remove adsorbed substances. Then the sample was degassed at room temperature for five minutes. The instrument was used to perform nitrogen adsorption tests at 77 K. The total specific surface area of the sample (unit: m 2 / g) was obtained by acquiring the nitrogen isothermal adsorption / desorption curve.

[0081] Tap density analysis

[0082] The tap density (TD) of the example samples was measured by mechanically tapping a graduated cylinder (100 ml) containing the sample (with a mass W of about 60 - 120 g). After observing the initial powder volume, the graduated cylinder was mechanically tapped for 15 minutes until no further volume (V, unit cm 3 ) or mass (W) change was observed. TD was calculated as TD = W / V. The TD measurement was performed on a J.Engelsmann Stamping volumeter STAV II instrument.

[0083] Particle size distribution (PSD) analysis

[0084] After dispersing the particles of the sample in an aqueous medium, the PSD was measured using a Malvern Mastersizer 3000 with a Hydro MV wet dispersion unit. To improve the dispersion of the metal hydroxide powder, sufficient ultrasonic irradiation and stirring were applied, and a suitable surfactant was introduced. The percentile values D10, D50, and D90 are the particle diameter values at 10%, 50%, and 90% respectively in the cumulative distribution. The span value of the hydroxide is the value of (D90 - D10) / D50.

[0085] Metal content analysis

[0086] The metal content of the hydroxide was measured by inductively coupled plasma - optical emission spectrometry (ICP - OES) using an Agilent ICP 720 - OES instrument. 1 g of the powder sample of each example was dissolved in 50 mL of high - purity hydrochloric acid in a conical flask. The flask was covered with a watch glass and heated on a hot plate at 380 °C until the sample was completely dissolved. After cooling to room temperature, the solution and rinsing water in the conical flask were transferred to a 250 mL volumetric flask. Thereafter, the volumetric flask was filled with deionized (DI) water to the 250 mL mark and then homogenized completely. An appropriate amount of the solution was taken with a pipette and transferred to a 250 mL volumetric flask for a second dilution, where the volumetric flask was filled with an internal standard and 10% hydrochloric acid to the 250 mL mark and then homogenized. Finally, the solution was used for ICP - OES measurement. The contents of metals such as Ni, Mn, and Co are expressed as mol% relative to the total metal content in the measured hydroxide.

[0087] Example 1

[0088] An aqueous slurry of the metal hydroxide was prepared according to the following procedure:

[0089] By adding 6 L of DI water, 350 mL of 220 g / L NH₃(aq), and 515 mL of an 800 g / L aqueous slurry of seed particles of Ni 65 Mn 15 Co 20 (OH)₂ with a D50 of 4.0 µm into a reactor vessel with an effective volume of 8.75 L, adjusting the temperature in the reactor vessel to 85 °C and maintaining this temperature throughout the process to prepare the starting solution.

[0090] Next, by adding a metal sulfate solution containing Ni, Mn, and Co (in a stoichiometric molar ratio of Ni:Mn:Co of 65:15:20) at 120 g / L, 220 g / L NH₃(aq), and 230 g / L NaOH solution, while at 30 kW / m for the first 6 hours3 The power densities around are mixed and the precipitation reaction is carried out at a power density of about 20 kW / m 3 around for the rest of the process. The feed rate of the metal sulfate solution is 600 mL / h at the beginning and continuously increases according to Equation 1 disclosed above to keep the particle growth rate constant at 0.4 μm / h (i.e., G(t) = 0.4 µm / h). During the reaction, the feed rate of the NaOH solution is adjusted so that the pH value of the reaction mixture in the reactor vessel is kept stable at 11.8 ± 0.1, and the feed rate of NH3(aq) is adjusted so that the NH 3(水) concentration in the reaction mixture is kept stable at 12.0 ± 1 g / L. Reactor samples of the reaction mixture are taken every two hours and D50 is measured therefrom. When the D50 of the reactor sample reaches the target value of about 10.2 µm, the reaction is stopped, and the duration of this process is 15 hours. During this process, a part of the liquid fraction of the reaction mixture is pumped out of the reactor by using a concentrator, and the solid content of the reaction mixture (which is an aqueous slurry containing hydroxide particles) in the reactor vessel at the end of the process is about 780 g / L.

[0091] Example 2

[0092] An aqueous slurry of metal hydroxide is prepared according to the following process:

[0093] By adding 6 L of DI water, 350 mL of 220 g / L NH3(aq), and 447 mL of 440 g / L aqueous slurry of Ni 94 Mn 03 Co 03 (OH)2 seed particles into a reactor vessel with an effective volume of 8.75 L, adjusting the temperature in the reactor vessel to 85°C and maintaining it at this temperature throughout the process to prepare the starting solution.

[0094] Next, by adding a metal sulfate solution containing Ni, Mn, and Co (in a stoichiometric molar ratio of Ni:Mn:Co of 94:03:03) at 120 g / L, 220 g / L NH3(aq), and 230 g / L NaOH solution, while mixing at a power density of about 30 kW / m for the first 6 hours and at a power density of about 20 kW / m for the rest of the process steps 3 for the rest of the process 3Precipitation reaction is carried out by mixing power densities on the left and right. The feeding rate of the metal sulfate solution is 540 mL / h at the beginning and continuously increases according to Formula 1 disclosed above to keep the growth rate of the particles constant at 0.5 μm / h. During the reaction, the feeding rate of the NaOH solution is adjusted so that the pH value of the reaction mixture in the reactor vessel is kept stable at 11.7 ± 0.1, and the feeding rate of NH3(aq) is adjusted so that the concentration of NH3(aq) in the reaction mixture is kept stable at 12.0 ± 1 g / L. Reactor samples of the reaction mixture are taken every two hours and D50 is measured therefrom. When the D50 of the reactor sample reaches the target value of about 10.0 µm, the reaction is stopped, and the duration of this process is 11 hours. During this process, a part of the liquid fraction of the reaction mixture is pumped out of the reactor by using an external concentrator, and the solid content of the reaction mixture in the reactor vessel at the end of the process is about 180 g / L.

[0095] Comparative Example 1

[0096] An aqueous slurry of metal hydroxide is prepared according to the following process:

[0097] By adding 1.6 L of DI water, 50 mL of 220 g / L NH3(aq), and 185 mL of 726 g / L containing Ni with a D50 of 5.0 µm 94 Mn 03 Co 03 (OH)2 seed particle aqueous slurry is added to a reactor vessel with an effective volume of 3.65 L, the temperature in the reactor vessel is adjusted to 85 °C and maintained at this temperature throughout the process to prepare the starting solution.

[0098] Next, by adding a metal sulfate solution containing Ni, Mn, and Co (in a stoichiometric molar ratio of Ni:Mn:Co of 94:03:03) at 120 g / L, 220 g / L NH3(aq), and 240 g / L NaOH solution, while at 33 kW / m 3Precipitation reaction is carried out by mixing power densities of around. The feeding rate of the metal sulfate solution is kept constant at 400 mL / h. During the reaction, the feeding rate of the NaOH solution is adjusted so that the pH value of the reaction mixture in the reactor vessel is kept stable at 11.8 ± 0.2, and the feeding rate of NH3 (aqueous) is adjusted so that the NH3 concentration in the reaction mixture is kept stable at 3.0 to 4 g / L. Reactor samples of the reaction mixture are taken every two hours and D50 is measured therefrom. When the D50 of the reactor sample reaches the target value of approximately 10.0 µm, the reaction is stopped, and the duration of this process is 22 hours. During this process, a part of the liquid fraction of the reaction mixture is pumped out of the reactor by using an external concentrator, and the solid content of the reaction mixture in the reactor vessel at the end of the process is around 726 g / L.

[0099] Dried product of the example

[0100] The reaction mixtures obtained in all examples (i.e., the aqueous slurries of metal hydroxides) are filtered and washed with 220 g / L NaOH solution and 60 °C DI water. The filter cake is dried in an oven at 120 °C for 12 hours.

[0101] Summary of the examples

[0102] The reaction conditions in the examples and some characteristics of the obtained aqueous slurries are schematically shown in Table 1. Some characteristics of the dried hydroxides obtained in these examples are schematically shown in Table 2.

[0103] Table 1

[0104]

[0105] Table 2

[0106]

Claims

1. A method for manufacturing an aqueous slurry of hydroxide or oxyhydroxide particles comprising one or more elements, wherein the one or more elements include at least one of Ni, Co, and Mn, and wherein the method comprises: - Supplying a stream of an aqueous metal salt solution comprising the one or more elements during a time period (T1 - T2), the time period having a start time (T1) and an end time (T2), - During the time period (T1 - T2), mixing the metal salt solution with an aqueous solution comprising one or more alkali metal hydroxides, thereby forming the aqueous slurry comprising hydroxide or oxyhydroxide particles of the one or more elements, wherein the metal salt solution is supplied at a flow rate expressed as a volume per unit time, wherein the metal salt solution has a concentration of the one or more elements expressed as moles per unit volume, and wherein the mathematical product of the flow rate and the concentration continuously increases during the time period (T1 - T2).

2. The method according to claim 1, wherein the time period (T1 - T2) continues until a target median particle size D50 of the hydroxide or oxyhydroxide particles of the one or more elements is obtained.

3. The method according to claim 1 or 2, the method further comprising maintaining a pH value range of the aqueous slurry in the reactor vessel during the time period (T1 - T2), the range being greater than or equal to 9.0 and less than or equal to 14.0, and more preferably greater than or equal to 10.0 and less than or equal to 13.5, wherein the pH value of the aqueous slurry is the pH value measured for a sample of the aqueous slurry at 20°C.

4. The method according to any one of the preceding claims, wherein during the time period (T1 - T2), the aqueous slurry in the reactor vessel has a temperature of at least 45°C and preferably at least 75°C, more preferably at least or equal to 85°C; and / or the temperature is at most 99°C, preferably at most 95°C, and more preferably at most 90°C.

5. The method according to any one of the preceding claims, wherein the aqueous slurry is mixed with a mixing energy of at most 40 kW, preferably at most 35 kW, per m 3 of the aqueous slurry; and / or the mixing energy is at least 5 kW, preferably at least 10 kW, per m 3 of the aqueous slurry. 3 3 ​ 6. The method according to any one of the preceding claims, the method further comprising maintaining in the reactor vessel a concentration of NH of at least 1.0 g / l and at most 13.0 g / l during the time period (T1-T2). 3(水) concentration.

7. The method according to any one of the preceding claims, wherein at the end (T2) of the time period, the aqueous slurry in the reactor vessel comprising hydroxide or oxyhydroxide particles of the one or more elements has a solids content of at least 200 g / l, preferably at least 350 g / l, more preferably at least 600 g / l, even more preferably at least 750 g / l, and most preferably 800 g / l.

8. The method according to any one of the preceding claims, wherein an aqueous slurry of seed particles is provided in the reactor vessel before the start (T1) of the time period, preferably wherein the seed is particles of hydroxide or oxyhydroxide of at least one metal element, preferably wherein the at least one metal element comprises at least Ni.

9. The method according to claim 8, wherein the seed particles have a median particle size D’50, and wherein at the end (T2) of the time period, the hydroxide or oxyhydroxide particles of the one or more elements have a median particle size D50, where the ratio D50 / D ’ 50 is at least 2.00 and preferably at least 3.00; and / or wherein D’50 is at least 0.70 μm and at most 3.00 μm, where D50 is at least 3.0 μm and preferably at most 5.0 μm; and / or wherein D’50 is at least 3.0 μm and at most 5.0 μm, where D50 is at least 8.0 μm; and / or wherein D50 is at most 15.0 μm, preferably at most 13.0 μm, and more preferably at most 12.0 μm.

10. The method according to any one of the preceding claims, wherein the mathematical product of the flow rate and the concentration at the end (T2) of the time period is at least 2 times the mathematical product of the flow rate and the concentration at the start (T1) of the time period; preferably, the mathematical product at the end (T2) of the time period is at least 2.5 times the mathematical product at the start (T1) of the time period; more preferably, the mathematical product at the end (T2) of the time period is at least 3.0 times the mathematical product at the start (T1) of the time period.

11. The method according to any one of the preceding claims, wherein the one or more elements in the hydroxide or oxyhydroxide particles comprise: - Ni at a content x, where 5.0 mol% ≤ x ≤ 99 mol%, - Co at a content y, where 0 ≤ y ≤ 30.0 mol%, and - Mn at a content z, where 0 ≤ z ≤ 85.0 mol%, - Al at a content q, where 0 ≤ q ≤ 10.0 mol%, and - one or more additional elements at a content r, where the additional elements are elements from the list of B, Ba, Ca, Ce, Cr, Fe, La, Mg, Mo, Nb, Si, Sr, Ti, Y, V, W, Zn, Na, S, and Zr, where 0 ≤ r ≤ 5.0 mol%, and where x, y, z, q, and r are contents expressed in mol% relative to the total molar content of the one or more elements in the hydroxide or oxyhydroxide particles, and where x + y + z + q + r = 100 mol%.

12. The method according to claim 11, wherein x ≥ 60.0 mol%, wherein z ≤ 30.0 mol%, and wherein (y + z) ≥ 1.0 mol%; more preferably, wherein x ≥ 70.0 mol%, and preferably wherein x ≥ 80.0 mol%; or wherein z ≥ 50.0 mol%, and preferably wherein r ≤ 3.0 mol%; and / or wherein z ≥ 60.0 mol%; and / or wherein z ≤ 90.0 mol%, preferably wherein z ≤ 85.0 mol%.

13. The method according to any one of claims 8 to 12, wherein the concentration of the one or more elements in the metal salt solution remains constant during the time period (T1 - T2), and wherein the flow rate of the metal salt solution at time t within the time period (T1 - T2) is represented by Equation 1: where m1 is the mass (grams) of the seed particles provided in the reactor vessel, G(t) is the growth rate of the hydroxide or oxyhydroxide particles at the time t, where the value of G(t) is non-zero, Δt is the time period (T1 - T2) expressed in hours h, D’50 is the median particle size of the seed particles expressed in µm, and M Me is the molar mass (grams / mole) of the one or more elements, c Me is the concentration (grams / l) of the one or more elements, and M Me(OH)2 is the molar mass (grams / mole) of the hydroxide or oxyhydroxide of the one or more elements, preferably the value of G(t) is less than or equal to 2 µm / h, more preferably less than or equal to 1.5 µm / h.

14. A method for manufacturing a powdery hydroxide or oxyhydroxide of one or more elements, wherein the method comprises: 1) Producing an aqueous slurry comprising hydroxide or oxyhydroxide particles of one or more elements according to any one of the preceding claims, 2) Separating the hydroxide or oxyhydroxide particles from the liquid fraction of the aqueous slurry, and 3) Drying the separated hydroxide or oxyhydroxide particles.

15. A method for manufacturing a positive electrode active material, the method comprising: 1) Produce a powdery hydroxide or hydroxyoxide of one or more elements according to claim 14; 2) Mix the powdery hydroxide or hydroxyoxide with a lithium source to obtain a mixture; and 3) Sinter the mixture at a temperature between 650 °C and 1000 °C.

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