Method for producing positive electrode active material

Abstract

The present invention relates to a method for preparing a positive electrode active material, comprising the steps of: providing a powder material containing Li and having a Ni content of at least 60.0 mol% on a support (2) at a first position (12) of a production line (1); and contacting the powder material on the support (2) with an aqueous solution to form a wet powder material at a second position (13) of the production line (1), wherein the method comprises continuously moving the support (2) along a direction from the first position (12) to the second position (13).

Description

[Technical Field]

[0001] The present invention relates to a method for preparing an active cathode material for a battery, preferably a method for preparing an active cathode material comprising Li and at least 60 mol % Ni. Summary of the Invention

[0002] Such a positive electrode active material having a Ni content of at least 60 mol% contains lithium impurities, for example, in the form of LiOH and Li2CO3, on its particle surface. These impurities originate from lithium sources that are unreacted with the precursor of the positive electrode active material during synthesis. Specifically, to compensate for lithium loss during calcination due to lithium volatilization at high temperatures, an excess amount of lithium salt is added to the precursor of the positive electrode active material. The excess lithium content from the synthesis remains on the particle surface and simultaneously reacts with H2O, O2, and CO2 in the air to form impurities. Furthermore, the highly reactive Ni in the positive electrode active material 3+ ions can contribute to the formation of impurities. In particular, Ni 3+ Ni 2+ When spontaneously reduced to 2- is oxidized, resulting in Li + This reacts with the following equation: Ni 3+ +O 2- (lattice)→Ni 2+ +O - (1) O - +O - →O 2- (Activity)+O (2) O - +O→O2 - ;O+O→O2(3) O 2- (Activity)+CO2 / H2O→CO3 2- / OH - (4) 2Li + +CO3 2- / 2OH - →Li2CO3 / 2LiOH (5)

[0003] The presence of these impurities can lead to reduced capacity retention, significant gassing during cell cycling, and a high pH in the electrode coating slurry, which can cause gelation of the slurry during electrode preparation.

[0004] These lithium impurities on the surface of the cathode active material particles are removed by a so-called "washing process." A conventional washing process involves placing the cathode active material in a tank filled with an aqueous solution to form a slurry, stirring the slurry for a substantial period of time, and then separating the material from the aqueous solution by a filtration process.

[0005] However, such a typical cleaning process is a batch-type cleaning process, which is time-consuming and therefore has low throughput. Specifically, the powder material of the positive electrode active material is introduced into a tank filled with an aqueous solution over a considerable period of time. Therefore, the surface treatment of the powder material is not uniform, resulting in large variations in the properties of the powder material. Furthermore, the batch-type cleaning process is not time-efficient because it requires an intermediate step, such as filling a considerable amount of aqueous solution into the cleaning tank and cleaning the cleaning tank, between the surface treatment of the powder material. The batch-type cleaning process also causes excessive contact between the powder material and the aqueous solution, which can result in several side effects, such as surface defects, an increase in the specific surface area due to cation exchange, and Li extraction from the layered structure.

[0006] Therefore, an object of the present invention is to provide a method for more efficiently preparing a cathode active material having reduced amounts of lithium impurities compared to an unwashed cathode active material, which has high throughput and allows the cathode active material to be exposed to an aqueous solution for a uniform period of time, thereby producing a cathode active material powder with minimal variation in physicochemical properties after the washing step.

[0007] For further guidance, figures are included to better understand the teachings of the present invention, which are intended to aid in the explanation of the invention and are not intended to limit the invention of this disclosure. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows an exemplary embodiment of a first aspect of the present invention; [Figure 2] 1 is a schematic diagram showing a first embodiment of a toothed distribution tray according to the present invention; FIG. [Figure 3] 1 is a schematic diagram showing a second embodiment of a toothed distribution tray according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0009] 1 shows an exemplary embodiment of a first aspect of the present invention. In the first aspect, the present invention provides a method for preparing a cathode active material, the method comprising: providing a powder material containing Li and having a Ni content of at least 60 mol% on a support (2) at a first position (12) of a production line (1); and contacting the powder material on the support (2) with an aqueous solution to form a wet powder material at a second location (13) of the production line (1); The support (2) is continuously moved along a direction from a first position (12) to a second position (13).

[0010] The method according to the present invention is time-efficient because it is a continuous process that does not require filling or washing with an aqueous solution. Furthermore, the method according to the present invention allows for a more uniform surface treatment than methods using batch washing steps because (i) the support (2) on which the powder material is prepared is continuously moving, so that the powder material comes into contact with the aqueous solution only when the support (2) passes through the second position (13), and (ii) the method according to the present invention makes it easier to control the washing time, thus avoiding excessive contact between the powder and the aqueous solution. To ensure a uniform surface treatment, the powder material is spread evenly across the width of the support (2) to form a thin layer.

[0011] In a preferred embodiment, the powder material comprises Li, O, and M, where M is Ni with a content x, where x≧60.0 mol%; Mn with a content y of 0%≦y≦40.0 mol%; Co with a content z of 0%≦z≦40.0 mol%; A having a content p of 0%≦p≦5.0 mol%, where A is at least one element other than Li, Ni, Mn, Co, and O; x+y+z+p=100.0 mol%.

[0012] Preferably, x≧70.0 mol%, more preferably x≧75.0 mol%, and even more preferably x≧80.0 mol%.

[0013] Preferably, y≦30.0 mol%, more preferably y≦25.0 mol%, and even more preferably y≦20.0 mol%.

[0014] Preferably, z≦30.0 mol %, more preferably z≦25.0 mol %, and even more preferably z≦20.0 mol %.

[0015] Preferably, p≦4.0 mol %, more preferably p≦3.0 mol %, and even more preferably p≦2.0 mol %.

[0016] Preferably, x, y, z, and p are measured by ICP-OES (Inductively Coupled Plasma).

[0017] In one embodiment, the element A is selected from the group consisting of Ag, Al, As, Au, B, Ba, Bi, Ca, Ce, Cd, Cr, Cs, Eu, Fe, Ga, Ge, Hg, Sb, Se, In, Ir, K, La, Mg, Mo, Na, Nb, Nd, Os, P, Pb, Pd, Pr, Pt, Rb, Re, Rh, Ru, S, Sc, Se, Si, Sm, Sr, Ta, Te, Ti, Y, V, W, Zn, and Zr, or combinations thereof.

[0018] Preferably, element A is selected from the group consisting of Al, As, B, Ba, Ca, Ce, Cd, Cr, Cs, Fe, Ga, Ge, Se, In, Ir, K, Mg, Mo, Na, Nb, Nd, P, Pd, Pt, S, Sc, Se, Si, Sr, Ta, Te, Ti, Y, V, W, Zn, and Zr, or combinations thereof.

[0019] Even more preferably, the element A is selected from the group consisting of Al, B, Ba, Ca, Cr, Fe, Mg, Mo, Nb, S, Si, Sr, Ti, Y, V, W, Zn, and Zr, or combinations thereof.

[0020] In the framework of the present invention, the term "support" is to be understood as any means intended to support and hold the powder material during the preparation of the active cathode material.

[0021] In a preferred embodiment, the support (2) is permeable to aqueous solutions. Preferably, the support (2) has pores, each of which has a cross-sectional area smaller than 1% of the particle size of the cumulative volume percent distribution (D1) of the powder material measured by laser diffraction. The support (2) having pores has the advantage that unwanted particles or impurities can be removed through the pores.

[0022] In a preferred embodiment, a powder feed line (4) is disposed at a first position (12) of the production line (1) for distributing powder material onto the support (2). The thickness of the powder material layer is preferably in the range of 0.1 cm to 5.0 cm, more preferably 1.0 cm to 4.0 cm, and most preferably 2.0 cm to 3.0 cm. The powder feed line (4) may be equipped with a profiling knife at a fixed position between the first position (12) and the second position (13) above the upper surface of the support (2) from which the powder is released, to allow for better spreading of the powder across the width of the support (2).

[0023] Preferably, the gap between the profiling knife and the upper surface of the support (2) is at least 1.0 cm and at most 3.0 cm, so that the thickness of the powder is spread evenly to the same thickness as the gap between the profiling knife and the support (2).

[0024] In a preferred embodiment, at a second position (13) of the production line (1), the powder material on the support (2) is contacted with an aqueous solution to form a wet powder material.

[0025] Preferably, the aqueous solution is water, preferably deionized water. Preferably, the aqueous solution temperature is 10°C to 50°C, preferably 15°C to 25°C.

[0026] The aqueous solution is then discharged through a discharger (6). The discharger (6) may be a spray nozzle. The spray nozzle utilizes the kinetic energy imparted to the aqueous solution to break it into droplets, thereby evenly dispersing the aqueous solution over the powder material. The spray nozzle may be positioned vertically above the support (2). The spray nozzle may be aligned in a direction perpendicular to the direction of movement of the support (2). The position of the spray nozzle is the same as the second position (13) of the production line (1) where the aqueous solution is discharged through the spray nozzle. The spray nozzle may be a plain orifice nozzle, a shaped orifice nozzle, a surface impingement single-fluid nozzle, a pressure-swirl single-fluid nozzle, a solid-cone single-fluid nozzle, or a composite nozzle. The number and spacing of the spray nozzles are adjusted so that the aqueous solution is discharged over the entire top surface of the portion of the powder material layer located vertically below the spray nozzle. The spray nozzle may be made of a non-corrosive material.

[0027] The spray angle is preferably in the range of 20° to 140°, more preferably 30° to 120°, and most preferably 45° to 90°. The spray distance is preferably in the range of 5 cm to 100 cm, more preferably 7 cm to 30 cm, and most preferably 10 cm to 20 cm.

[0028] When the aqueous solution is sprayed through a spray nozzle and strikes the surface of the powder material, a slurry is generated, filling any gaps that may be created by the aqueous solution being sucked through the support. This eliminates gaps in the cake of powder material after contact between the powder material and the aqueous solution, preventing channeling of the aqueous solution. This reduces the content of impurities in the powder material.

[0029] In another embodiment, the emitter (6) can be a toothed distribution tray. Figure 2 is a schematic diagram showing one embodiment of a toothed distribution tray. The dashed line in Figure 2 shows an enlarged view of the teeth (61) from the bottom. The toothed distribution tray (60) embodiment comprises a plurality of teeth (61) aligned in a direction perpendicular to the direction of movement of the support (2). The toothed distribution tray (60) embodiment has a flat surface with toothed zigzag edges with a fixed distance between each tooth (61). Each tooth (61) comprises an outlet (62) for the aqueous solution. The cross-sectional shape of the outlet (62) can be circular, elliptical, or polygonal, such as square, rectangular, pentagonal, or hexagonal. The area of ​​the outlet (62) is preferably 15 mm 2 ~2000mm 2 , more preferably 100 mm 2 ~1500mm 2 , most preferably 300 mm 2 ~700mm 2 The flow rate of the aqueous solution at the outlet (62) is preferably in the range of 0.01 m 3 / hour~10m 3 / hour, preferably 0.1m 3 / hour~5m 3 / hour, most preferably 1m 3 / hour~3m 3 / time range.

[0030] FIG. 3 is a schematic diagram showing one embodiment of a toothed distribution tray. The embodiment of the toothed distribution tray (60a) comprises a plurality of teeth (61a) aligned in a direction perpendicular to the direction of movement of the support (2). The embodiment of the toothed distribution tray (60a) has a flat surface with a toothed zigzag edge with a fixed gap (63a) between each tooth (61a). The aqueous solution supplied from the rear of the tray (60a) flows through the gap (63a) onto the powder material. The supply direction of the aqueous solution is indicated by a dashed arrow, but is not limited to the illustration in FIG. 3. The flow rate of the aqueous solution through the gap (63a) is preferably 0.01 m 3 / hour~10m 3 / hour, preferably 0.1m 3 / hour~5m 3 / hour, most preferably 1m 3 / hour~3m 3 / time range.

[0031] The toothed distribution tray (60, 60a) is disposed at a fixed position vertically above the support (2) so that impurities on the powder material are sufficiently removed while preventing the powder material from scattering. The distance from the toothed distribution tray (60, 60a) to the upper surface of the powder material layer is preferably in the range of 5 cm to 100 cm, more preferably 7 cm to 50 cm, and most preferably 10 cm to 20 cm. The number and spacing of the teeth (61, 61a) are adjusted so that impurities on the powder material are sufficiently removed. The toothed distribution tray (60, 60a) may be made of a non-corrosive material.

[0032] In the embodiment where the aqueous solution is discharged through a toothed distribution tray (60, 60a), dust generation can be reduced and splashing of powder material can be reduced.

[0033] In another embodiment, the aqueous solution is delivered to a flowing pool, and the support (2) transporting the powder material is immersed in the aqueous solution through the pool while the powder material on the support (2) is in contact with the aqueous solution. The support (2) may be permeable to the aqueous solution.

[0034] In a preferred embodiment, the support (2) is continuously moved along the direction from the first position (12) to the second position (13) at a speed of 0.5 cm / sec to 2 cm / sec, preferably the speed is 1 cm / sec, so that the powder material is exposed to the aqueous solution for a duration of at least 30 seconds and at most 10 minutes.

[0035] In a preferred embodiment, the suction line is located adjacent to the aqueous solution permeable support (2) along the second location (13), which facilitates faster penetration of the aqueous solution into the powder material. Preferably, the suction line is also located adjacent to the aqueous solution permeable support (2) after the second location (13), which facilitates faster removal of the aqueous solution from the wet powder material.

[0036] Furthermore, the method may further include evaporating the aqueous solution from the wet powder material. The evaporating the aqueous solution may be carried out in a hot gas compartment. The gas in the hot gas compartment is preferably, but not limited to, CO2-free dry air, N2 gas, or any inert gas. The hot gas compartment may be a vacuum heater compartment. The temperature in the vacuum heater compartment is at least 70°C and at most 300°C, preferably at least 90°C and at most 200°C.

[0037] In another embodiment, the method may further include separating the aqueous solution from the wet powder material. The step of separating the aqueous solution may be performed using at least one of a belt filter and a vacuum filter. A belt filter is a pair of filtering cloths, in which the wet powder material is placed between the cloths, and the sandwich of cloths passes through a series of rollers to press and remove the aqueous solution, thereby producing a wet cake. The filter cloth is a water-permeable material. A vacuum filter is a filter that allows the aqueous solution to easily pass through because it is subjected to a vacuum on the output side of the aqueous solution.

[0038] Preferably, the method is carried out in a CO2-free atmosphere, except for the step of contacting the powder material on the support (2) with the aqueous solution.

[0039] The atmosphere is preferably, but not limited to, CO2-free dry air, N2 gas, or any inert gas.

[0040] A second aspect of the present invention is a positive electrode active material production line (1), A support (2), a supply section (3) having a supply line (4) for preparing a powder material on the support (2); a discharge unit (5) comprising a dispenser (6) of an aqueous solution, the dispenser (6) dispensing the aqueous solution onto the powder material to form a wet powder material; and at least one drive unit (7) for continuously moving the support (2) along a direction from the supply unit (3) to the discharge unit (5), The present invention relates to a positive electrode active material production line (1), in which a support (2) extends from at least a supply section (3) to a discharge section (5).

[0041] In a preferred embodiment, the powder material has a first content of Li impurities and the wet powder material has a second content of Li impurities, the second content being lower than the first content, where the amount of Li impurities is measured by pH titration and varies depending on parameters such as the total time the powder is immersed in water.

[0042] The cathode active material production line (1) may further include an evaporator (8) configured to evaporate the aqueous solution from the wet powder material. Figure 1 shows an exemplary embodiment of the invention in which the evaporator (8) is a hot gas compartment. Hot gas is introduced into the evaporator (8) through an inlet pipe (14) and discharged through an outlet pipe (15).

[0043] The cathode active material production line (1) may further include a separator (9) configured to separate the aqueous solution from the wet powder material. The separator (9) may be disposed between the discharge section (5) and the evaporator (8). FIG. 1 shows an exemplary embodiment of the present invention in which the separator (9) is a belt filter. The belt filter includes a filter cloth (16) and rollers (18). The wet powder material on the support (2), shown as lines (17), is squeezed through the rollers (18) to separate the aqueous solution from the wet powder material.

[0044] The positive electrode active material production line (1) may further include a discharge section (10) equipped with a recovery line (11) for recovering the positive electrode active material.

[0045] Experimental Tests Used in the Examples In the examples, the following analytical methods are used:

[0046] Measurement of median particle size by laser diffraction method The particle size distribution (PSD) of the cathode active material powders was measured by laser diffraction particle size analysis using a Malvern Mastersizer 3000 equipped with a Hydro MV wet dispersion accessory (https: / / www.malvernpanalytical.com / en / products / product-range / mastersizer-range / mastersizer-3000#overview) after dispersing each powder sample in aqueous media. Sufficient ultrasonic irradiation and stirring were applied and appropriate surfactants were introduced to improve powder dispersion. D1 is defined as the particle size at 1% of the cumulative volume percent distribution obtained from the Malvern Mastersizer 3000 using Hydro MV measurements.

[0047] Measurement of Li impurity content by pH titration First, calibrate the pH electrode. Add 5 g of the positive electrode active material powder to 100 g of deionized (DI) water in a closed flask and stir for 10 minutes. The slurry is suction filtered to obtain approximately 98–99 g of clear solution. Filtration takes only a few seconds. 90 g of the clear solution is used for the pH titration experiment and can be kept in an open 250 mL glass flask. Start the pH titration within 1 minute after the filtration is complete. During the pH titration experiment, insert the electrode into the clear solution and stir it continuously. After 30 seconds, begin adding acid (0.1 M HCl). Add the acid at a rate of 0.5 mL / min. Record pH data points every 3 seconds. Perform the pH titration at room temperature. Terminate the pH titration when a value below pH 3.0 is reached. The lithium impurity is assumed to contain only two contributing components: (1) LiOH and (2) Li2CO3. A typical pH titration will show two inflection points. The first pH is about 8.4, and the second pH is about 4.7. Both inflection points are due to Li2CO3 and can be used to calculate the amount of Li2CO3. The formula used to calculate the amount of Li2CO3 and LiOH (wt%) is as follows:

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[0048] The present invention is further illustrated in the following examples.

[0049] Example 1 EX1.1 is prepared by solid-state reaction of a lithium source with a transition metal-based source precursor according to the following steps.

[0050] Step 1) The metal composition Ni was obtained by a coprecipitation process in a large continuous stirred tank reactor (CSTR) containing mixed nickel-manganese-cobalt sulfate, sodium hydroxide, and ammonia. 0.80 Mn 0.10 Co 0.10 A transition metal oxide hydroxide precursor is prepared having the formula:

[0051] Step 2) The precursor prepared from step 1) is heated in an oxidizing atmosphere at 375° C. for 7 hours to obtain a heated precursor.

[0052] Step 3) The prepared heated precursor from step 2) is mixed with LiOH in an industrial blender to obtain a first mixture with a lithium to metal ratio of 1.00.

[0053] Step 4) The first mixture from step 3) is heated at 750°C for 2 hours under a constant flow of oxygen to obtain a second heated powder.

[0054] Step 5) The second heated powder from step 4) is reheated in a tray furnace at 810°C for 12 hours in an oxidizing atmosphere, followed by a grinding and sieving process to obtain a calcined powder labeled as EX1.1.

[0055] EX1.3 is a positive electrode active material prepared according to the method of the present invention in a production line (1) comprising a powder dispenser unit, a support (2), an aqueous solution dispenser (6), and further comprising an evaporator (8) for evaporating the aqueous solution from the wet powder material EX1.2.

[0056] Step 1) EX1.1 is placed on a support (2) which is a conveyor belt by a powder dispenser unit.

[0057] Step 2) EX1.1, placed on the first position (12) of the support (2), is moved by a conveyor belt line to the second position (13) of the support (2) at a moving speed of 1 cm / sec. To form a uniformly distributed powder bed of EX1.1, a profiling knife is placed 2 cm above the upper surface of the support (2) between the first position (12) and the second position (13). The measured powder bed depth of EX1.1 is 2.0 ± 0.1 cm.

[0058] Step 3) The powder bed of EX1.1 is contacted with an aqueous solution, which is deionized water, at a second position (13). At the second position (13), deionized water is released onto the powder bed of EX1.2 through a spray nozzle of the aqueous solution releaser (6) to form a wet powder material EX1.1. The temperature of the deionized water before spraying is approximately 15°C. The support (2) is a water-permeable material with a pore size of 5 μm, allowing the aqueous solution to pass through the support (2). The production line (1) further comprises a solution suction line adjacent to the water-permeable support (2) to facilitate faster water removal from the wet powder material EX1.2.

[0059] Step 4) The wet powder material EX1.2 is dried in a hot gas compartment at 100° C. The dried powder is designated EX1.3.

[0060] Example 2 EX2.2 is prepared according to the same method as EX1.3, except that at a second position (13) EX1.1 dispensed onto a support (2) is contacted with deionized water discharged through a toothed dispensing tray (60) to form a wet powder material EX2.1.

[0061] The toothed distribution tray (60) is placed in a fixed position 10 cm above the top of the support (2), thereby allowing deionized water to flow steadily over the surface of the distributed powder. The temperature of the deionized water is controlled at 15°C before flowing into the tray (60).

[0062] Example 3 EX3 is a dry powder prepared according to the same method as EX1.3, except that EX3 is dried in both the belt filter and the hot gas compartment.

[0063] The belt filter is made from a water-permeable material with a pore size of 5 μm, allowing the aqueous solution to pass through the filter and convert the wet powder material into a wet cake.

[0064] The wet cake from the belt filter passes through a hot gas section where gas having a temperature of 100° C. flows through the wet cake. The gas is dry air that does not contain CO2.

Claims

1. 1. A method for preparing a positive electrode active material, comprising: providing a powder material containing Li and having a Ni content of at least 60.0 mol% on a support (2) at a first position (12) of a production line (1); and contacting the powder material on the support (2) with an aqueous solution to form a wet powder material at a second location (13) of the production line (1); The method comprises the step of continuously moving the support (2) along a direction from the first position (12) to the second position (13).

2. The powder material comprises Li, O, and M, wherein M is Ni with a content x, where x≧60.0 mol%; Mn with a content y of 0%≦y≦40.0 mol%; Co with a content z of 0%≦z≦40.0 mol%; A having a content p of 0%≦p≦5.0 mol%, where A is at least one element other than Li, Ni, Mn, Co, and O; 2. The method of claim 1, wherein x+y+z+p=100.0 mol %.

3. 3. The method of claim 1 or 2, wherein the aqueous solution is discharged through a spray nozzle.

4. The method according to any one of claims 1 to 3, wherein the aqueous solution is discharged through a toothed distribution tray (60, 60a).

5. 5. The method according to claim 4, wherein said support (2) is permeable to said aqueous solution.

6. 5. The method according to claim 4, wherein during the step of contacting the powder material on the support (2) with the aqueous solution, the support (2) is immersed in the aqueous solution.

7. The method of any one of claims 1 to 6, further comprising evaporating the aqueous solution from the wet powder material.

8. The method of claim 7 , wherein the step of evaporating the aqueous solution occurs in a hot gas compartment.

9. The method of claim 8 , wherein the hot gas compartment is a vacuum heater compartment.

10. 10. The method of any one of claims 1 to 9, further comprising separating the aqueous solution from the wet powder material.

11. 11. The method of claim 10, wherein the step of separating the aqueous solution is performed in at least one of a belt filter and a vacuum filter.

12. The method according to any one of the preceding claims, wherein the aqueous solution is aspirated through a suction line placed adjacent to the support (2) that is permeable to the aqueous solution.

13. The method of any one of claims 1 to 12, wherein the aqueous solution is water.

14. A positive electrode active material production line (1), A support (2), a supply section (3) including a supply line (4) for providing a powder material containing Li and having a Ni content of at least 60.0 mol% on the support (2); a discharge unit (5) comprising a dispenser (6) of an aqueous solution, said dispenser (6) providing said aqueous solution onto said powder material to form a wet powder material; and at least one drive unit (7) for continuously moving the support (2) along a direction from the supply unit (3) to the discharge unit (5), The positive electrode active material production line (1) includes a support (2) extending from at least the supply section (3) to the discharge section (5).

15. 15. The positive electrode active material production line of claim 14, wherein the powder material has a first content of Li impurities and the wet powder material has a second content of Li impurities, the second content being lower than the first content.

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