Process for manufacturing a particulate (OXY)hydroxide with narrow particle diameter distribution

Abstract

Process for making a particulate (oxy)hydroxide of TM wherein TM refers to a combination of nickel and at least one metal selected from Co and Mn and wherein said process comprises the steps of: (a) Providing one or more aqueous solution(s) (α) containing water-soluble salts of Ni and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (β) containing an alkali metal hydroxide and, optionally, an aqueous solution (γ) containing a complexing agent, (b) combining solution(s) (α) and solution (β) and, if applicable, solution (γ) at a pH value in the range of from 11.2 to 14.0, determined at 23°C in a stirred tank reactor, thereby creating solid particles of hydroxide, said solid particles being slurried, (c) transferring slurry from step (b) into a stirred tank reactor (A) where a solution (α) and a solution (β) and, if applicable, a solution (γ) are combined with the slurry at a pH value in the range of from 10.0 to 12.5, determined at 23°C, (d) wherein slurry from stirred tank reactor (A) is transferred to a side vessel (B) that contains one to 150 candle filters (C) through which liquid is withdrawn from the reaction, and slurry is returned into stirred tank reactor from step (c).

Description

[0001] Process for manufacturing a particulate (oxy)hydroxide with narrow particle diameter distribution

[0002] The present invention is directed towards a process for making a particulate (oxy) hydroxi de of TM wherein TM refers to a combination of nickel and at least one metal selected from Co and Mn and wherein said process comprises the steps of:

[0003] (a) Providing one or more aqueous solution(s) (a) containing water-soluble salts of Ni and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (P) containing an alkali metal hydroxide and, optionally, an aqueous solution (y) containing a complexing agent,

[0004] (b) combining solution(s) (a) and solution (P) and, if applicable, solution (y) at a pH value in the range of from 11.2 to 14.0 determined at 23°C in a stirred tank reactor, thereby creating solid particles of hydroxide, said solid particles being slurried,

[0005] (c) transferring slurry from step (b) into a stirred tank reactor (A) where a solution (a) and a solution (P) and, if applicable, a solution (y) are combined with the slurry at a pH value in the range of from 10.0 to 12.5, determined at 23°C,

[0006] (d) wherein slurry from stirred tank reactor (A) is transferred to a side vessel (B) that contains one to 150 candle filters (C) through which liquid is withdrawn from the reaction, and slurry is returned into stirred tank reactor from step (c).

[0007] Additionally, the present invention is directed towards cathode active materials and their precursors, and to a set-up useful for the inventive process.

[0008] Lithiated transition metal oxides are currently used as electrode active materials for lithium-ion batteries. Extensive research and developmental work have been performed in the past years to improve properties like charge density, specific energy, but also other properties like the reduced cycle life and capacity loss that may adversely affect the lifetime or applicability of a lithium-ion battery. Additional effort has been made to improve manufacturing methods.

[0009] In a typical process for making cathode materials for lithium-ion batteries, first a so-called precursor is being formed by co-precipitating the transition metals as carbonates, oxides or preferably as hydroxides that may or may not be basic, for example oxyhydroxides. The precursor is then mixed with a source of lithium such as, but not limited to LiOH, U2O or U2CO3 and calcined (fired) at high temperatures. Lithium salt(s) can be employed as hydrate(s) or in dehydrated form. The calcination - or firing - often also referred to as thermal treatment or heat treatment of the precursor - is usually carried out at temperatures in the range of from 600 to 1000 °C. During the thermal treatment a solid-state reaction takes place, and the electrode active material is formed. The thermal treatment is performed in the heating zone of an oven or kiln.

[0010] To a certain extent, properties of the precursor translate into properties of the respective electrode active material, such as particle size distribution, content of the respective transition metals and more. It is therefore possible to influence the properties, such as share of fines, pressed density or compressability, of electrode active materials by steering the properties of the precursor. Conclusions about the share of fines may be drawn from the D1 value. High shares of fines are usually undesired because they lead to losses during cathode active material productions. Such losses are usually in the form of dust in the dust filters.

[0011] Cathode active materials - and thus their precursors - with a narrow particle size distribution have been a goal of research. In EP 2 720 305 A, a two-step process is disclosed wherein the pH value is lowered in the second step, the so-called particle growth step, with respect to the first step. In EP 2 818 452 A, a two-step process is disclosed wherein mother liquor is withdrawn in the particle growth step. Care is taken that no solids are withdrawn together with said mother liquor.

[0012] It is an objective of the present invention to provide a process that allows the production of a highly spherical precursor with narrow particle size distribution. It was further an objective of the present invention to provide a precursor for an electrode active material with a narrow particle size distribution and excellent sphericity.

[0013] Accordingly, the process as defined at the outset has been found, hereinafter also defined as “inventive process” or “process according to the (present) invention”. The inventive process comprises at least four steps, hereinafter also referred to as step (a), step (b), step (c) and step (d), or - even more briefly - (a), (b), (c) and (d), respectively. The inventive process may include further - optional - steps. Steps (a), (b), (c) and (d) are described in more detail below. By the inventive process, precursors with narrow particle size distributions and a high breaking strengths are obtained.

[0014] The inventive process is a process for making a particulate (oxy) hydroxi de of TM. Said particulate (oxy) hydroxi de then serves as a precursor for electrode active materials, and it may therefore also be referred to as precursor. In one embodiment of the present invention, the resultant precursor is comprised of secondary particles that are agglomerates of primary particles. Said primary particles have the shape of platelets.

[0015] In one embodiment of the present invention the specific surface (BET) of the resultant precursor is in the range of from 2 to 70 m2 / g, determined by nitrogen adsorption, for example in accordance with to DIN-ISO 9277:2003-05. The outgassing temperature is 120°C.

[0016] The precursor is an (oxy)hydroxide of TM wherein TM comprises Ni and at least one metal selected from Co and Mn and Al, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Mg, and Nb.

[0017] In one embodiment of the present invention, TM is a combination of metals according to general formula (I)

[0018] (NiaCobMnc)i-dMd(I) wherein a is in the range of from 0.6 to 0.95, preferably from 0.8 to 0.94, b being in the range of from 0.025 to 0.2, preferably from 0.025 to 0.15, c being in the range of from zero to 0.2, preferably from zero to 0.15, and d being in the range of from zero to 0.1 ,

[0019] M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and from combinations of at least of the aforementioned, a + b + c = 1 , preferably b + c > zero or M includes Al and d > zero.

[0020] In another embodiment of the present invention, the variables in formula (I) are defined as follows: a is in the range of from 0.25 to 0.4, b is in the range of from zero to 0.2, c is in the range of from 0.6 to 0.75, and d is in the range of from zero to 0.1, M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and from combinations of at least of the aforementioned, a + b + c = 1.

[0021] In each case, TM may contain traces of further metal ions, for example traces of ubiquitous metals such as sodium, iron, calcium or zinc, as impurities but such traces will not be taken into account in the description of the present invention. Traces in this context will mean amounts of 0.05 mol-% or less, referring to the total metal content of TM.

[0022] The precursors are particulate materials. In one embodiment of the present invention, precursors have an average particle diameter (d50) in the range of from 3 to 20 pm, preferably from 4 to 16 pm. The average particle diameter may be determined, e. g., by light scattering or LASER diffraction or electroacoustic spectroscopy. The above particle diameter refers to the secondary particle diameter.

[0023] The span of the particle diameter distribution of inventive precursors may be in the range of from 0.10 to 0.19, preferably 0.15 to 0.19. The span is defined as [(d90) - (d10)] / (d50), with the values of (d90), (d50) and (d10) being the respective percentiles and determined by dynamic light scattering. Especially, (d50) is the median value but sometimes also referred to as average particle diameter.

[0024] In one embodiment of the present invention, the (d1) value is at least 80% of the average value (D50). The value of (d1) is the respective percentile and determined by dynamic light scattering. For example, for a precursor with an average particle diameter of 13.9 pm, the (d1) value is at least 11.1 pm.

[0025] The various percentiles are preferably volume based.

[0026] Said particulate material may have an irregular shape but in a preferred embodiment, said particulate material has a regular shape, for example spheroidal or even spherical. The aspect ratio may be in the range of from 1 and 10, preferably from 1 to 3 and even more preferably from 1 to 1.5. The aspect ratio is defined as the ratio of width to length or specifically the particle diameter in the longest dimension versus the particle diameter in the shortest dimension. Perfectly spherical particles have an aspect ratio of 1.

[0027] The steps (a), (b) etc. shall be described in more detail below. Step (a) includes providing at least one aqueous solution (a) containing water-soluble salts of Ni and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (P) containing an alkali metal hydroxide and, optionally, an aqueous solution (y) containing a complexing agent, for example ammonia.

[0028] The term water-soluble salts of cobalt and nickel or manganese or of metals other than nickel and cobalt and manganese refers to salts that exhibit a solubility in distilled water at 25°C of 25 g / l or more, the amount of salt being determined under omission of crystal water and of water stemming from aquo complexes. Water-soluble salts of nickel and cobalt and manganese may preferably be the respective water-soluble salts of Ni2+and Co2+and Mn2+. Examples of water- soluble salts of nickel and cobalt are the sulfates, the nitrates, the acetates and the halides, especially chlorides. Preferred are nitrates and sulfates, of which the sulfates are more preferred.

[0029] The term “water-soluble compounds of aluminum” then refers to compounds like Ah(SO4)3, AI(NO3)3, KAI(SO4)2, NaAICh and NaAI(OH)4. Depending on the choice of water-soluble compound of aluminum, the pH value of aqueous solution (a) may be in the range of from 1 to 3 or above 13.

[0030] Examples of suitable compounds of Mg are MgSO4, Mg(NOs)2, magnesium acetate and MgCh, with MgSO4being preferred.

[0031] Examples of suitable compounds of Ti are Ti(SO4)2, TiOSO4, TiO(NOs)2, Ti(NOs)4, with Ti(SO4)2 being preferred.

[0032] Examples of suitable compounds of Zr are zirconium acetate, Zr(SO4)2, ZrOSO4, ZrO(NOs)2, Zr(NOs)4, with Zr(SO4)2 being preferred.

[0033] Examples of suitable compounds of Nb are (NH4)Nb(C2O4)3 and (NH4)NbO(C2O4)2. Examples of suitable compounds of Mo are MoOs, Na2MoO4, and (NH4)2MoO4.

[0034] Examples of suitable compounds of W are WO3, WO3 ■ H2O, Na2WO4, ammonium tungstate and tungstic acid.

[0035] Solution (a) may have a pH value in the range of from 2 to 5. In embodiments wherein higher pH values are desired, ammonia may be added to solution (a). However, it is preferred to not add ammonia to solution (a). In case it is intended to provide a solution containing NaAICh and NaAI(OH)4it is preferred to provide at least two aqueous solutions, one containing nickel and at least one of cobalt and manganese and, optionally, at least one of Ti, Zr, Mo, W, Mg, Nb, and Ta, and another aqueous solution containing NaAICh or NaAI(OH)4.

[0036] The concentration of nickel and other constituents of TM, as the case may be, can be selected within wide ranges. Preferably, the respective total metal concentration is selected to be within a range of 1 to 1.8 mol of the metal / kg of solution, more preferably 1.3 to 1.7 mol of the metal / kg of solution.

[0037] In addition, in step (a) an aqueous solution of alkali metal hydroxide is provided, hereinafter also referred to as solution (P). Examples of alkali metal hydroxides are potassium hydroxide and a combination of sodium and potassium hydroxide, and even more preferred is sodium hydroxide.

[0038] In one embodiment of the present invention, solution (P) mainly contains alkali metal hydroxide and some amount of carbonate, e.g., 0.1 to 2 % by weight, referring to the respective amount of alkali metal hydroxide, added deliberately or by aging of the solution (P) or the respective alkali metal hydroxide.

[0039] Solution (P) may have a concentration of hydroxide in the range from 0.1 to 12 mol / l, preferably 6 to 10 mol / l.

[0040] The pH value of solution (P) is preferably 13 or higher, for example 14.5.

[0041] Solution (y) contains a complexing agent. Examples of complexing agents are ammonia and organic acids or their alkali or ammonium salts wherein said organic acid bears at least two functional groups per molecule and at least one of the functional groups is a carboxylate group.

[0042] Examples of organic acids that bear two identical functional groups are adipic acid, oxalic acid, succinic acid and glutaric acid. An example of organic acids that bears three identical functional groups is citric acid.

[0043] In one embodiment of the present invention, said organic acid is selected from malic acid, tartaric acid, citric acid, and glycine.

[0044] In one embodiment of the present invention, the concentration of complexing agent(s) in solution (Y) is in the range of froml to 30 % by weight. In embodiments wherein the complexing agent is selected from ammonia its concentration is preferably in the range of from 10 to 30 % by weight. In embodiments wherein the complexing agent(s) is or are selected from organic acids or their alkali or ammonium salts wherein said organic acid bears at least two functional groups per molecule and at least one of the functional groups is a carboxylate group, the concentration of said complexing agent in solution (y) may be in the range of from 0.2 to 10% by weight.

[0045] More preferred complexing agent is ammonia.

[0046] Step (b) includes combining solution(s) (a) and solution (P) and, if applicable, solution (y) in one or more sub-steps, in a stirred tank reactor, at a pH value in the range of from 11.2 to 14.0, preferably 12.0 to 13.0, determined at 23°C, thereby creating solid particles of hydroxide. Said solid particles are slurried. Step (b) may be performed in a continuously operated stirred tank reactor but is preferably performed as a discontinuous process. Step (b) may be performed in one or more sub-steps or in a single sub-step.

[0047] In embodiments wherein step (b) is performed in a single sub-step - that may as well be termed “in a single step” or “in a single operation””, step (b) is preferably performed at a constant pH value.

[0048] In embodiments wherein step (b) is performed in at least two sub-steps, hereinafter also referred to as sub-step (b1), sub-step (b2), and, if applicable, sub-step (b3) etc., at least two substeps, for example sub-steps (b1) and (b2), are performed at different pH values, for example at a pH values that differs by 0.2 to 1.5 units, each determined at 23°C.

[0049] In one embodiment of the present invention, step (b) is performed at a temperature in the range from 10 to 85°C, preferably at temperatures in the range from 20 to 70°C.

[0050] In one embodiment of the present invention, step (b) is performed at constant pressure, for example at ambient pressure. In other embodiments, step (b) is performed at elevated pressure, for example up to 50 bar.

[0051] In one embodiment of the present invention, step (b) is performed under an inert atmosphere, for example nitrogen or a rare gas such as argon. Oxygen-depleted air, for example with up to 2% by weight of O2, is feasible as well, especially when TM does not contain manganese. Due to the strong alkalinity of solution (P), CO2 is not a suitable atmosphere.

[0052] In a preferred embodiment, slurry is removed from the continuous stirred tank reactor in which step (b) is carried out and transferred to a stirred storage vessel where the slurry is stored under stirring for a time period of from 15 minutes to 24 hours, preferably from 30 minutes to 10 hours, before being transferred to the second stirred tank reactor. Said operation is also referred to as storage step. In the course of the storage step, neither solution (a) nor solution (P) nor solution (Y) is added. Said storage is preferably under inert gas, vide supra.

[0053] In one embodiment of the present invention, the temperature during the storage step is in the range of from 20 to 70°C, preferably 30 to 70°C.

[0054] In one embodiment of the present invention, the pH value of the slurry in the storage vessel is in the range of from 10.0 to 13.0 determined at 23°C, preferably from 11.0 to 12.0.

[0055] Step (c) includes transferring slurry from step (b) into a stirred tank reactor (A) where a solution

[0056] (a) and a solution (P) and, if applicable, a solution (y) are combined with the slurry at a pH value in the range of from 10.0 to 12.5 and preferably lower than in step (b), determined at 23°C. Step (c) is preferably carried out in a batch mode. Solutions (a) and (P) in step (c) may have a composition different from the composition of solutions a) and (P) in step (b) or preferably the same.

[0057] In one embodiment of the present invention, the residence time in step (c) is in the range of from 30 minutes to 36 hours.

[0058] As indicated above, the pH value in step (c) is preferably lower than in step (b), for example by 0.2 to 2.0 units, determined at 23°C. For example, when the pH value in step (c) is 12.5, step

[0059] (b) is performed at a pH value of least 12.7, for example 12.7 to 14.0 or 12.8 to 13.5. In another example, when the pH value in step (b) is 12.0, step (b) is performed at a pH value of at most 11.9, for example 10.0 to 11.8 or 10.5 to 11.5.

[0060] In one embodiment of the present invention, step (c) is performed at a temperature in the range from 10 to 85°C, preferably at temperatures in the range from 20 to 70°C.

[0061] In one embodiment of the present invention, step (c) is performed at constant pressure, for example at ambient pressure. In other embodiments, step (c) is performed at elevated pressure, for example up to 50 bar.

[0062] In one embodiment of the present invention, step (c) is performed under an inert atmosphere, for example nitrogen or a rare gas such as argon. Oxygen-depleted air, for example with up to 2% by weight of O2, is feasible as well, especially when TM does not contain manganese. Due to the strong alkalinity of solution (P), CO2 is not a suitable atmosphere. The stirred tank reactor (A) comprises at least piping through which slurry formed in step (c) is transferred into a side vessel (B) in which step (d) is performed. While step (b) and step (c) are performed subsequently, step (d) is performed at least partially at the same time as step (c).

[0063] In step (d), slurry from step (c) is transferred to a side vessel (B) that contains one to 150 candle filters, preferably 10 to 100 candle filters, through which liquid is withdrawn from the reaction, and slurry is returned into stirred tank reactor from step (c). Said returned slurry has a higher particle content than the slurry transferred to the side vessel (B), and step (d) thus results in a thickening of the slurry. In embodiments wherein more than one candle filter is used, such candle filters are arranged as registers.

[0064] In the transfer of slurry into side vessel (B), the amounts of slurry are selected in a way that there is no turbulence around the candle filter(s), and a laminar flow is accomplished instead. A laminar flow is accomplished by inlet baffle(s) or a distributor installed at the upper part of side vessel (B).

[0065] Returning the slurry from side vessel (B) into stirred tank reactor (A) may be performed by flushing, for example with inert gas such as nitrogen, or by water or filtrate from step (d). It should be noted that volumes of water or filtrate needed to be applied in the flushing that are smaller than the volumes of liquid that are withdrawn.

[0066] Withdrawal of the liquid may be supported by suction / ”vacuum”.

[0067] In one embodiment of the present invention, candle filter(s) are made from sintered metal or from polymers such as polypropylene or polyethylene. They need to stand a pressure of at least 5 bar, preferably at least 8 bar. A maximum pressure is, e.g., 10 bar.

[0068] In one embodiment of the present invention, candle filter(s) have a diameter of from 60 to 150 mm and a length of from 800 to 2500 mm.

[0069] Candle filters may be designed as symmetrical or asymmetrical. Symmetrical candle filters have a porous structure with a pore size distribution characterized by an average pore size that is essentially the same over the entire candle. In asymmetrical candles, the average pore size varies across the candle, with the size generally increasing from one surface to the other.

[0070] In one embodiment of the present invention, candle filter(s) have a pore diameters of 5 pm or less, for example 0.3 to 5 pm, preferably 0.5 to 3 pm. The pores may be uniform in diameter or have a pore diameter distribution. In one embodiment of the present invention, candle filters have a filter cloth from porous materials such as polypropylene, polyethylene such as HDPE, PVDF (polyvinylidendifluoride), poly- eetheretherketone, fleece, polytetrafluoroethylene, polyethersulfone (“PES”) or paper, polysulfone or the like, with an average pore diameter of up to 10 pm. Pores from filter cloth may have a diameter of from 0.1 to 5 pm, preferably 0.3 to 3 pm.

[0071] Polypropylene may be employed as monofilament or multifilament. While monofilament based fabrics have the advantages of a high filtration speed and that the filter cake is removed more easily, and less solids are retained in the filter cloth, multifilament based fabrics have the advantages of higher mechanical stability, resulting in less wear.

[0072] In one embodiment of the present invention, the volume ratio of side vessel (B) to stirred tank reactor (A) is in the range of from 1 :20 to 1 :4. Side vessel (B) is then smaller than stirred tank reactor (A).

[0073] Step (d) is performed multiple times. In one embodiment of the present invention, about 10% to up to the 10-fold of the volume of stirred tank reactor are transferred into side vessel (B) per hour and returned back into stirred tank reactor (A).

[0074] In one embodiment of the present invention, the residence time of a certain portion of solids in side vessel (B) is in the range of some seconds, for example 10 seconds, to up to 5 minutes. Preferably, the residence time in side vessel (B) decreases with increasing solids content of the slurry transferred from stirred tank reactor (A) into side vessel (B). Such decrease may be performed stepwise or continuously.

[0075] Preferably, in the side vessel (B), no stirrer is required.

[0076] The efficiency of the withdrawal of liquid is increased if no big filter cake build-up is possible. In one embodiment of the present invention, a major filter cake build-up in said side vessel is prevented by flushing back the filter cake into stirred tank reactor (A) together with the slurry.

[0077] In one embodiment of the present invention, the filter cake build-up in side vessel (B) is kept in the range of from 5 seconds to 10 minutes, and the filter cake is discharged into the stirred tank reactor (A).

[0078] Liquid withdrawn in step (d) is an aqueous medium containing alkali metal salt with anions from the nickel salt and the transition metal salt(s) that are dissolved to form aqueous solution (a), traces non-precipitated transition metal salts, and furthermore complexing agent from solution (Y), if applicable. Liquid withdrawn in step (d) is preferably a clear and translucent liquid, but it may contain small particles of hydroxide. Preferably, the solid particles content in liquor withdrawn in step (d) through the candle filter(s) is below 1 mg / l.

[0079] In one embodiment of the present invention, slurry from step (b) is transferred to a side vessel (B) as well, and a step (d) is performed likewise. Said side vessel may be the same as for slurry from step (c) or in a separate.

[0080] In one embodiment of the present invention, in at least one of steps (b) and (c), a coaxial mixer is used for addition of at solution (a) and (P) or solution (a) and (y), see, e.g., WO 2020 / 207901. In a preferred embodiment of the present invention, aqueous solution (a) is introduced through the inner pipe of a coaxial mixer and aqueous solution (y) is introduced through the outer pipe, this will lead to a minor degree of incrustations.

[0081] In one embodiment of the present invention, in step (d), to achieve a suited flow distribution device into the inflow section of side vessel (B) may be improved by insertion of an inlet baffle or a distributor. Such inlet baffle or distributor may improve the homogeneity of distribution of residence time in the side vessel and minimize the hold-up of side vessel (B).

[0082] In one embodiment of the present invention, the inventive process is performed in parallel in several stirred tank reactors (A) that are connected to a side vessel (B), and liquid from the reaction is withdrawn through candle filter(s). In such embodiment, it is preferred to have at least 10 candle filters in side vessel (B), preferably at least 50, in order to have a greater surface through which liquid is removed. Such embodiments are useful when large quantities of (oxy) hydroxi de are desired with the same composition.

[0083] By performing the inventive process, a hydroxide of TM is obtained. Upon drying, especially upon drying in air at a temperature in the range of from 80 to 150°C, partial oxidation and dewatering may take place, and an oxyhydroxide is formed.

[0084] A further aspect of the present invention refers to particulate (oxy) hydroxi de of TM, hereinafter also referred to as inventive (oxy) hydroxi des or inventive precursors. Inventive precursors are advantageously made according to the inventive process.

[0085] In inventive (oxy) hydroxide, TM refers to a combination of nickel with of at least one metal selected from cobalt and manganese, wherein said inventive (oxy)hydroxide has an average parti- cle diameter (d50) in the range of from 3 to 20 pm, preferably 4 to 16 pm. Inventive (oxy)hydroxide preferably has a monomodal particle diameter distribution.

[0086] In inventive (oxy) hydroxide, TM refers to a combination of nickel with of at least one metal selected from cobalt and manganese, wherein said inventive (oxy)hydroxide has an average particle diameter (d50) in the range of from 3 to 20 pm, preferably 4 to 16 pm, and a core-shell structure wherein both core and shell show an essentially radial alignment of platelet-shaped primary particles, and wherein core and shell are separated by a porous layer that contains randomly arranged primary particles.

[0087] The porous layer may be detected by scanning electron microscopy (“SEM”) or transmission electron microscopy (“TEM”). In said porous layer, usually only few voids may be detected. Preferably, said porous layer between core and shell has an average thickness in the range of from 0.1 to 1.0 pm.

[0088] The portion of radially aligned primary particles may be determined, e.g., by SEM (Scanning Electron Microscopy) of a cross-section of at least 5 secondary particles.

[0089] “Essentially radially alignment” does not require a perfect radial orientation but includes that in an SEM analysis, a deviation to a perfectly radial orientation is at most 5 degrees.

[0090] Furthermore, at least 70% of the secondary particle volume is filled with radially oriented primary particles. Preferably, only a minor inner part, for example at most 30%, preferably at most 20%, of the volume of those particles is filled with non-radially oriented primary particles, for example, in random orientation.

[0091] In the porous layer, preferably the share of voids is more than 10% if determined by choosing 5 representative particles in SEM and calculating the voids.

[0092] In one embodiment of the present invention, inventive (oxy)hydroxides have a particle size (d1) of at least 80% of the average particle diameter (D50).

[0093] In one embodiment of the present invention, inventive (oxy) hydroxi des have a particle size distribution with a span [(d90) - (d10)] / (d50) in the range of from 0.10 to 0.19, preferably from 0.11 to 0.18. The diameters (d10), (d50) and (d90) may be determined by dynamic light scattering and refer to the respective percentiles. In one embodiment of the present invention, TM in inventive (oxy)hydroxides is a combination of metals according to general formula (I)

[0094] (NiaCobMnc)i-dMd(I) with a being in the range of from 0.6 to 0.95, preferably from 0.8 to 0.94, b being in the range of from 0.025 to 0.2, c being in the range of from zero to 0.2, and d being in the range of from zero to 0.1 ,

[0095] M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1.

[0096] In another embodiment of the present invention, the variables in formula (I) are defined as follows: a is in the range of from 0.25 to 0.4, b is in the range of from zero to 0.2, c is in the range of from 0.6 to 0.75, and d is in the range of from zero to 0.1,

[0097] M is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1.

[0098] In one embodiment of the present invention, inventive precursors have a porous layer between core and shell with an average thickness in the range of from 0.1 to 1.0 pm.

[0099] Inventive (oxy)hydroxides are excellent precursors for cathode active materials which are suitable for producing batteries with a high volumetric energy density and excellent cycling stability. Another aspect of the present invention is thus the use of inventive precursors for the manufacture of cathode active materials for lithium-ion batteries. Such cathode active materials are made by mixing inventive precursor with a source of lithium, e.g., LiOH or U2O2 or U2CO3, followed by calcination, for example at a temperature in the range of from 750 to 900°C. Especially in embodiments wherein TM of inventive (oxy)hydroxides corresponds to formula (I), said calcination is preferably performed in an atmosphere of oxygen or oxygen-enriched air, for example with at least 60 vol-% of oxygen, preferably 80 vol-% of oxygen and more preferably at least 90 vol-% oxygen. In embodiments wherein the variable a in formula (I) is in the range of from 0.25 to 0.4, said calcination may be performed in air atmosphere.

[0100] Examples of suitable set-ups for said calcination are rotary kilns, roller hearth kilns, and pusher kilns.

[0101] In one embodiment of the present invention, the temperature is ramped up before reaching the desired temperature of from 750 to 900°C. For example, first a mixture of precursor and source of lithium and oxide or hydroxide of Al is heated to a temperature to 350 to 550°C and then held constant for a time of 10 min to 4 hours, and then it is raised to 650°C up to 1000°C, preferably 650 to 850°C.

[0102] In embodiments wherein in the mixing step at least one solvent has been used, as part of step such solvent(s) are removed, for example by filtration, evaporation or distilling of such solvents). Preferred are evaporation and distillation.

[0103] In one embodiment of the present invention, said calcination is performed in a roller hearth kiln, a pusher kiln or a rotary kiln or a combination of at least two of the foregoing. Rotary kilns have the advantage of a very good homogenization of the material made therein. In roller hearth kilns and in pusher kilns, different reaction conditions with respect to different steps may be set quite easily. In lab scale trials, box-type and tubular furnaces and split tube furnaces are feasible as well.

[0104] By performing the inventive calcination process cathode active materials with excellent properties and a narrow particle size distribution are available through a straightforward process. Preferably, the electrode active materials so obtained have a specific surface (BET) in the range of from 0.1 to 0.8 m2 / g, determined according to DIN-ISO 9277:2003-05. Preferably, such cathode active materials also have a high breaking strength.

[0105] Another aspect of the present invention is related to a set-up, hereinafter also referred to as inventive set-up, in which an inventive process may be performed.

[0106] Inventive set-ups comprise

[0107] (A) at least one stirred tank reactor,

[0108] (B) a side vessel connected to stirred tank reactor (A) through at least two pipes, (P1) and (P2), (C) one to 150 candle filters located in side vessel (B) through which liquid may be withdrawn from the reaction and slurry is returned into said stirred tank reactor (A) through pipe (P2).

[0109] Side vessel (B) together with the candle filter(s) may serve as a thickener.

[0110] In one embodiment of the present invention, side vessel (B), inlet baffle(s) or a distributor installed at the upper part of side vessel (B). This will cause a laminar flow of slurry during operation, and it will avoid turbulences.

[0111] Preferably, the inventive set-up additionally comprises a means for introducing aqueous medium such as water or mother liquor, or a gas such as nitrogen into side vessel (B) for the purpose of flushing back slurry into stirred tank reactor (A). Such means may be selected from pumps and pressure generators.

[0112] The present invention is further illustrated by a working example and by a drawing.

[0113] The following experimental set-up is used:

[0114] 1.1 Set-Up

[0115] (A.1): Stirred tank reactor, with baffles, volume: 200 liter, with feed inlets for solutions (a.1), (p.1), (y.1) and double jacket for heating omitted [simplified drawing]

[0116] (B.1): side vessel, connected through a pipe (P1.1) and a pump, gross volume of side vessel (B.1): 12 liter

[0117] In side vessel (B.1): one candle filter (not displayed), material: polyethylene, pore diameter: 0.3 to 3 pm, length 1000 mm: diameter: 80 mm. Filter cloth: HDPE, pore diameter up to 0.8 pm, air permeability 0.2 to 0.5 L / (dm2min)

[0118] Another pipe is attached at the bottom of the side vessel (B.1) and leads to stirred tank reactor (A.1).

[0119] Flushing arrangement: Flushing is performed in the reverse direction via the filtrate (mother liquor) line

[0120] The following aqueous solutions were provided:

[0121] Solution (a.1): NiSCU, CoSO4 and MnSC>4 dissolved in deionized water (molar ratio 91:4.5:4.5, total transition metal concentration: 1.45 mol / kg)

[0122] Solution (p.1): 25wt% NaOH dissolved in deionized water

[0123] Solution (y.1): 25wt% ammonia in deionized water 1.2 Manufacture of the inventive precursor P-CAM.1

[0124] 1.2.1 Manufacture of a slurry of seeds, step (b.1):

[0125] A 10 I stirred vessel equipped with baffles and a three-stage pitch-blade stirrer (45° blade angle) with a diameter of 0.21 m was charged with 4 liters of de-ionized water. The stirrer element was activated to reach an average energy dissipation of 0.8 W / l and the water was heated to 55°C. Afterwards, solution (y.1) was added to reach an NH3 concentration of 0.23w%. Then, the pH of the solution was adjusted to 12.2 by adding solution (p.1 ).

[0126] Then, the stirrer rotation speed was increased and constantly operated at 420 rpm (average energy input -12.6 W / l). Subsequently, feeding of solutions (a.1), (p.1 ) and (y.1) was started simultaneously. The total flow of feeds was adjusted to reach an average residence time of 7.5 hours. The molar ratio between ammonia and metal was adjusted to 0.17. The flow rate of the NaOH was adjusted by a pH value regulation circuit to keep the pH value in the vessel at a constant value of 12.4. The apparatus was operated continuously keeping the liquid level in the reaction vessel constant. The resulting seed suspension for step (b1.2) was collected via free overflow from the vessel. The resulting slurry contained about 110 g / l mixed hydroxide of Ni, Co and Mn with an average particle size (D50) of 3.9 pm and a span of 1 .28.

[0127] Step (c.1 )

[0128] The set-up according to Figure 1 is charged with 150 I de-ionized water so that both stirrer stages are submersed. The stirrer speed is adjusted to 130 rpm (0.36 W / l) while the water is heated via the double jacket to 55°C. The temperature is kept constant at 55°C during the complete batch. Then, 7 kg of solution (p.1 ) are added. As a next step, 12 kg of slurry of seeds from step (b.1 ) is added to the mixture leading to an initial solid content of approx. 5 g / l. The pH value after addition of all feeds is 11 .65. Subsequently, the stirrer speed was adjusted to 396 rpm (corresponds to 7.9 W / l), and the feed of solutions (a.1), (p.1 ), and (y.1) is started simultaneously. The stirrer speed is stepwise decreased during the batch synthesis to a final stirrer speed of 130 rpm (0.36 W / l). The pH value is kept constant at 11 .5 by adjusting the addition of solutions (p.1 ) and (y.1) to obtain an ammonia concentration in mother liquor of 0.7w%. The ratio between reactor volume (200 I) and volume flow of total feeds (residence time equivalent) was started in a way that an average residence time of 40 hours would have resulted.

[0129] The side vessel (B.1) is empty at the beginning. After a reaction time of two hours, suspension transfer to the side vessel (B.1) is started with a volume flow of 50 l / h. 10 minutes later, suspension transfer from side vessel (B.1) back to the reactor is started with a volume flow of 340 l / h. The volume flows of suspension transfer to side vessel (B.1) and back to the reactor (A.1) are adjusted during above mentioned feed ramp to keep reactor volume constant at 200 I during the complete synthesis. Flushing back to stirred tank reactor (A.1) is achieved through nitrogen pressure of 5 bar.

[0130] Once the side vessel (B.1) is filled (after approx. 10 minutes), mother liquor is withdrawn through the candle filters. The mother liquor withdrawn appears clear to the naked eye.

[0131] The complete synthesis is 24 hours leading to a solids content in the reactor of 450 g / L, measured via H2SO4 dissolution of suspension and subsequent ICP analysis of Ni, Co, Mn.

[0132] After completion of the batch all feed flows are stopped and the final suspension from reactor and side vessel (B.1) were discharged to a stirred suspension buffer vessel and finally filtered using a filter press. The filter cake was washed with solution (p.1) and de-ionized water and dried at 120 °C for 14 hours to obtain the precursor P-CAM.1 with a molar composition of Ni:Co:Mn = 91 :4.5:4.5, an average particle size (dDO) = 13.9 pm and span = 0.19. The (D1) value was 11 .3 pm which corresponds to 81 .2% of the (D50).

[0133] In a comparison experiment, a set-up was selected but with a lamellar clarifier instead of side vessel (B.1). After an analogous reaction, a comparative precursor was obtained with an average particle size (dDO) = 13.8 pm and a D1 value of 8.3 pm, corresponding to 60.1 % of the (D50).

[0134] II. Synthesis of a cathode active material

[0135] 11.1 Manufacture of inventive CAM.1

[0136] P-CAM.1 is mixed with LiOH in a molar ratio Li / TM of 1.04 and calcined in a laboratory Linn furnace for 8 hours at 765°C. After natural cooling to ambient temperature, the resultant CAM.1 is deagglomerated in a lab mill. The resulting CAM.1 has an average particle size of 13.7 pm and a span of 0.19.

[0137] In electrochemical cells / lithium-ion batteries, cathodes containing CAM.1 have excellent properties. In addition, their pressed density and compressability is high.

Claims

Patent Claims1. Process for making a particulate (oxy)hydroxide of TM wherein TM refers to a combination of nickel and at least one metal selected from Co and Mn and wherein said process comprises the steps of:(a) Providing one or more aqueous solution(s) (a) containing water-soluble salts of Ni and of at least one transition metal selected from Co and Mn, and, optionally, at least one further metal selected from Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, and an aqueous solution (P) containing an alkali metal hydroxide and, optionally, an aqueous solution (y) containing a complexing agent,(b) combining solution(s) (a) and solution (P) and, if applicable, solution (y) at a pH value in the range of from 11.2 to 14.0 determined at 23°C in a stirred tank reactor, thereby creating solid particles of hydroxide, said solid particles being slurried,(c) transferring slurry from step (b) into a stirred tank reactor (A) where a solution (a) and a solution (P) and, if applicable, a solution (y) are combined with the slurry at a pH value in the range of from 10.0 to 12.5, determined at 23°C,(d) wherein slurry from step (c) is transferred to a side vessel (B) that contains one to 150 candle filters (C) through which liquid is withdrawn from the reaction, and slurry is returned into stirred tank reactor from step (c).

2. Process according to claim 1 wherein TM is a combination of metals according to general formula (I)(NiaCobMnc)i-dMd(I) whereinM is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1 , a being in the range of from 0.6 to 0.95, b being in the range of from 0.025 to 0.2, c being in the range of from zero to 0.2, and d being in the range of from zero to 0.1 ,or wherein a is in the range of from 0.25 to 0.4, b is in the range of from zero to 0.2, c is in the range of from 0.6 to 0.75, and d is in the range of from zero to 0.1.

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

4. Process according to any of the preceding claims wherein the volume ratio of side vessel (B) to tank reactor (A) is in the range of from 1 :20 to 1 :4.

5. Process according to any of the preceding claims wherein from 10 vol-% up to then tenfold of the volume of stirred tank reactor (A) are transferred to side vessel (B) per hour.

6. Process according any of the preceding claims wherein a filter cake build-up in side vessel (B) is kept in the range of from 5 seconds to 5 minutes, and the filter cake is rapidly discharged into the stirred tank reactor (A).

7. Process according to any of the preceding claims wherein in at least one of steps (b) and (c), a coaxial nozzle is used for addition of solution (a) and solution (P) or solution (a) and solution (y).

8. Process according to any of the preceding claims wherein in step (c), the solid particles content in mother liquor withdrawn in step (d) through the candle filter(s) is below 1 mg / l.

9. Particulate (oxy)hydroxide of TM wherein TM refers to a combination of nickel with of at least one metal selected from cobalt and manganese , wherein said particulate (oxy)hydroxide has an average particle diameter (d50) in the range of from 3 to 20 pm and a core-shell structure wherein both core and shell show an essentially radial alignment of platelet-shaped primary particles and wherein core and shell are separated by a porous layer that contains randomly arranged primary particles, and wherein said particulate (oxy)hydroxide has a particle size distribution with a span [(d90) - (d10)] / (d50) in therange of from 0.15 to 0.19, or said particulate (oxy)hydroxide has a particle diameter (d1) that is at least 80% of the average particle diameter (d50).

10. Particulate (oxy)hydroxide according to claim 9 wherein TM is a combination of metals according to general formula (I)(NiaCobMnc)i-dMd(I) whereinM is selected from Mg, Al, Ti, Zr, Mo, W, Al, Mg, Nb, and Ta, a + b + c = 1 , and a is in the range of from 0.6 to 0.95, b is in the range of from 0.025 to 0.2, c is in the range of from zero to 0.2, and d is in the range of from zero to 0.1, or a is in the range of from 0.25 to 0.4, b is in the range of from zero to 0.2, c is in the range of from 0.6 to 0.75, and d is in the range of from zero to 0.1.

11. Particulate (oxy)hydroxide according to claim 9 or 10 wherein the porous layer between core and shell has an average thickness in the range of from 0.1 to 1.0 pm.

12. Use of a particulate (oxy)hydroxide according to any of claims 9 to 112 for the manufacture of a cathode active material.

13. Process for making a cathode active material according to general formula Lii+xTMi-xO2 comprising the step of mixing a particulate (oxy)hydroxide according to any of claims 9 to 11 with a source of lithium, followed by a thermal treatment at a temperature in the range of from 750 to 950°C in an oxidizing atmosphere.

14. Set-up comprising(A) at least one stirred tank reactor,(B) a side vessel connected to stirred tank reactor (A) through at least two pipes, (P1) and (P2),(C) one to 150 candle filters located in side vessel (B) through which liquid is withdrawn from the reaction and slurry is returned into said stirred tank reactor (A) through pipe (P2).

15. Set-up according to claim 14 wherein pipe P1 is connected to a pump.

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