Method for preparing positive electrode material precursor by using Couette-Taylor reactor

Abstract

The invention discloses a method for preparing a positive electrode material precursor by using a Couette-Taylor reactor. The process comprises: feeding a first reaction liquid to a first Couette-Taylor reactor and performing a co-precipitation reaction, thereby forming and continuously outputting a first product stream comprising core particles; feeding the first product stream to a second Couette-Taylor reactor connected in series behind the first Couette-Taylor reactor; and feeding the second reaction liquid into a second Couette-Taylor reactor to react with the core particles so as to form the positive electrode material with the core-shell structure. Wherein the first reaction liquid is a multi-metal solution. The second reaction liquid is a transition metal aqueous solution. The method provided by the invention can replace a traditional continuous stirring type reactor, and can achieve the purpose of continuous production.

Description

Technical Field

[0001] The present invention relates to a method for preparing a precursor of a cathode active material, and particularly to a method for preparing a precursor of a cathode active material by using a Couette-Taylor reactor. Background Art

[0002] The nickel-rich ternary cathode material or quaternary cathode material has the advantages of high energy density and low cost. However, due to the limitations of the mechanical properties and conductivity of the above cathode materials, during repeated charge and discharge processes, the structure of the cathode material is prone to crushing and dissolution, resulting in insufficient cycle stability.

[0003] In the prior art, in order to improve the service life, a functional material is mostly coated on the surface of the ternary cathode material or quaternary cathode material to prevent erosion by hydrogen fluoride (HF), reduce side reactions between the electrode material and the electrolyte, inhibit the dissolution of metal ions, and at the same time can also reduce the damage to the material structure during repeated charge and discharge processes, thereby further improving the cycle performance of the material.

[0004] However, the existing methods for preparing the precursor of the cathode material have many disadvantages. For example, the impregnation method cannot be continuously produced, the dry coating method is prone to uneven material distribution, and the equipment for sputtering and atomic layer deposition is expensive and cannot be continuously produced.

[0005] Therefore, the inventor of the present invention felt that the above defects could be improved, and then devoted himself to research and combined with the application of scientific principles, and finally proposed the present invention with reasonable design and effective improvement of the above defects. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a precursor of a cathode material by using a Couette-Taylor reactor in view of the deficiencies of the prior art.

[0007] To solve the above technical problems, one of the technical solutions adopted by the present invention is to provide a method for preparing a precursor of a cathode material using a Couette-Taylor reactor, which includes: implementing a first Couette-Taylor reaction step, including: feeding a first reaction liquid into a first Couette-Taylor reactor and performing a co-precipitation reaction, thereby forming and continuously outputting a first product stream containing a plurality of core particles; wherein, the first reaction liquid is a multi-metal solution; implementing a second Couette-Taylor reaction step, including: feeding the first product stream into a second Couette-Taylor reactor connected in series (such as connected in a pipeline) after the first Couette-Taylor reactor; and feeding a second reaction liquid into the second Couette-Taylor reactor so that a functional coating layer is formed on the outer surface of each of the plurality of core particles, thereby forming a second product stream containing a plurality of core-shell structured cathode material precursors; wherein, the second reaction liquid is an aqueous solution of a coating material, and the aqueous solution of the coating material is an aqueous solution of a transition metal; and implementing a purification step, including purifying the second product stream to purify and separate a plurality of the core-shell structured cathode material precursors from the second product stream.

[0008] Preferably, the multi-metal solution contains at least three of nickel (Ni) compound, cobalt (Co) compound, manganese (Mn) compound, magnesium (Mg) compound, and aluminum (Al) compound; wherein, each of the core particles is at least one of a ternary alloy hydroxide core particle and a quaternary alloy hydroxide core particle.

[0009] Preferably, the aqueous solution of the transition metal is at least one of a zirconium ion solution, a tungsten ion solution, an aluminum ion solution, a zinc ion solution, a titanium ion solution, a molybdenum ion solution, and a tin ion solution.

[0010] Preferably, the flow rate of the second reaction liquid fed into the second Couette-Taylor reactor is 3% to 20% of the flow rate of the first reaction liquid fed into the first Couette-Taylor reactor.

[0011] Preferably, the flow rate of the first reaction liquid fed into the first Couette-Taylor reactor is between 0.5 mL / min and 3 mL / min; wherein, the flow rate of the second reaction liquid fed into the second Couette-Taylor reactor is between 0.05 mL / min and 0.30 mL / min, and the flow rate of the second reaction liquid is 3% to 20% of the flow rate of the first reaction liquid.

[0012] Preferably, the first reaction temperature in the first Couette-Taylor reactor is between 45°C and 70°C, and the rotational speed of the first rotary motor of the first Couette-Taylor reactor is between 500 rpm and 900 rpm.

[0013] Preferably, the second reaction temperature in the second Couette-Taylor reactor is between 45°C and 70°C, and the rotational speed of the second rotary motor of the second Couette-Taylor reactor is between 400 rpm and 800 rpm.

[0014] Preferably, the first Couette-Taylor reaction step further comprises: feeding a first chelating agent and a first precipitating agent into the first Couette-Taylor reactor respectively to mix with the first reaction liquid to form a reaction mixture; wherein the first residence time of the reaction mixture in the first Couette-Taylor reactor is between 300 minutes and 600 minutes.

[0015] Preferably, the second Couette-Taylor reaction step comprises: feeding a second chelating agent and a second precipitating agent into the second Couette-Taylor reactor respectively to mix with the second reaction liquid to form another reaction mixture; wherein the second residence time of the another reaction mixture in the second Couette-Taylor reactor is between 150 minutes and 500 minutes, and the second residence time is 50% to 85% of the first residence time.

[0016] Preferably, in each of the core-shell structured cathode material precursors, the core particle size of the core particles is between 4 μm and 12 μm, and the thickness of the functional coating layer is between 1% and 20% of the core particle size of the core particles.

[0017] One of the beneficial effects of the present invention is that the method for preparing the precursor of the positive electrode material using a Couette-Taylor reactor provided by the present invention can achieve the purpose of continuous production by replacing the traditional continuous stirred reactor through the technical solution of "performing a first Couette-Taylor reaction step, including: feeding a first reaction liquid into a first Couette-Taylor reactor and performing a co-precipitation reaction to form and continuously output a first product stream containing a plurality of core particles; wherein, the first reaction liquid is a multi-metal solution" and "performing a second Couette-Taylor reaction step, including: feeding the first product stream into a second Couette-Taylor reactor connected in series after the first Couette-Taylor reactor; and feeding a second reaction liquid into the second Couette-Taylor reactor so that the second reaction liquid forms a functional coating layer on the outer surface of each of the plurality of core particles, thereby forming a second product stream containing a plurality of positive electrode material precursors with a core-shell structure; wherein, the second reaction liquid is an aqueous solution of a coating material, and the aqueous solution of the coating material is an aqueous solution of a transition metal; and performing a purification step, including: purifying the second product stream to purify and separate a plurality of the positive electrode material precursors with a core-shell structure" . Among them, the first Couette-Taylor reactor is used to form core particles (i.e., the core part) with uniform element distribution and dense structure by the co-precipitation method. In addition, the second Couette-Taylor reactor is used to perform surface coating modification on the aforementioned core particles to form a positive electrode material precursor with a core-shell structure. The present invention can continuously produce a positive electrode material precursor with a core-shell structure, which can effectively improve the stability and endurance of lithium batteries and take into account the safety of the materials.

[0018] In order to further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the provided drawings are only for reference and illustration and are not used to limit the present invention. Brief Description of the Drawings

[0019] Figure 1 Schematic diagram of the device for preparing the precursor of the positive electrode material using Couette-Taylor reactors in the embodiment of the present invention.

[0020] Figure 2A SEM photograph of the positive electrode material with a core-shell structure in Example 3 of the present invention.

[0021] Figure 2B SEM photograph of the positive electrode material with only single-layer core particles in Comparative Example 1.

[0022] Figure 3AThis is the SEM experimental photograph of the cathode active material with a core-shell structure after 500 charge-discharge cycles in Example 3 of the present invention.

[0023] Figure 3B This is the SEM experimental photograph of the cathode active material with only a single-layer core particle after 500 charge-discharge cycles in Comparative Example 1.

[0024] Figure 4A For Figure 3A This is the SEM experimental photograph of the cross-section of the cathode active material.

[0025] Figure 4B For Figure 3B This is the SEM experimental photograph of the cross-section of the cathode active material. Detailed implementation manners

[0026] The following are specific embodiments to illustrate the disclosed embodiments of the present invention. Those skilled in the art can understand the advantages and effects of the present invention from the content disclosed in this specification. The present invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of the present invention. Additionally, the drawings of the present invention are only for simple schematic illustration and are not depicted according to actual dimensions, and this is stated in advance. The following embodiments will further detail the related technical content of the present invention, but the disclosed content is not used to limit the protection scope of the present invention. It should be understood that although terms such as "first", "second", "third", etc. may be used in this document to describe various units or parameters, these units or parameters should not be limited by these terms. These terms are mainly used to distinguish one unit from another unit, or one parameter from another parameter. Additionally, the term "or" used in this document should, depending on the actual situation, possibly include any one or a combination of more of the associated listed items.

[0027] Please refer to Figure 1 As shown, the embodiment of the present invention provides a method for preparing a cathode active material precursor using Couette-Taylor reactors to prepare a cathode active material precursor with a core-shell structure.

[0028] In this embodiment, the cathode active material precursor is an active substance used in a lithium battery to be mixed with a lithium salt (such as: LiOH·H2O), but the present invention is not limited thereto.

[0029] More specifically, the method for preparing a cathode active material precursor using Couette-Taylor reactors includes the following steps S110, step S120, and step S130.

[0030] Step S110 is to implement the first Couette-Taylor reaction step, which includes: feeding the first reaction liquid into the first Couette-Taylor reactor 1 through the first reaction liquid supply unit 11, and performing a co-precipitation reaction to form a first product stream P1 containing a plurality of core particles, and the core particles have the characteristics of uniform element distribution and dense structure. Wherein, each of the core particles is at least one of a ternary alloy hydroxide core particle and a quaternary alloy hydroxide core particle.

[0031] The first reaction liquid is a multi-metal solution.

[0032] In some embodiments of the present invention, the multi-metal solution contains at least three of nickel (Ni) compound, cobalt (Co) compound, manganese (Mn) compound, magnesium (Mg) compound, and aluminum (Al) compound. Preferably, the multi-metal solution contains at least nickel (Ni) compound, cobalt (Co) compound, and manganese (Mn) compound, and may not contain or selectively contain at least one of magnesium (Mg) compound and aluminum (Al) compound.

[0033] In some embodiments of the present invention, the nickel compound may be, for example, nickel sulfate (NiSO 4 ), the cobalt compound may be, for example, cobalt sulfate (CoSO 4 ), the manganese compound may be, for example, manganese sulfate (MnSO 4 ), the magnesium compound may be, for example, magnesium sulfate (MgSO 4 ), and the aluminum compound may be, for example, aluminum sulfate (Al 2 (SO 4 ) 3 ), but the present invention is not limited thereto.

[0034] More specifically, the first Couette-Taylor reactor 1 includes a first rotation axis 1a and a first reaction cavity 1b that surrounds the first rotation axis 1a in the radial direction.

[0035] The starting positions of the first Couette-Taylor reactor 1 are respectively connected to the first reaction liquid supply unit 11, the first chelating agent supply unit 12, and the first precipitating agent supply unit 13.

[0036] The first Couette-Taylor reactor 1 further includes a first rotation motor 14 connected to the first rotation axis 1a in the axial direction, and the first rotation motor 14 is configured to drive the first rotation axis 1a to rotate along the axial direction.

[0037] Among them, the first reaction liquid supply unit 11 is configured to feed the first reaction liquid (such as a multi-metal solution) into the first reaction cavity 1b of the first Couette-Taylor reactor 1 through one of the first pump infusion units 151 of the first pump module 15.

[0038] Among them, the first chelating agent supply unit 12 is configured to feed a first chelating agent (such as an aqueous ammonia solution, NH 4 OH(aq)) into the first reaction cavity 1b of the first Couette-Taylor reactor 1 through another one of the first pump infusion units 152 of the first pump module 15 to mix with the first reaction liquid (such as a multi-metal solution).

[0039] Among them, the first precipitant supply unit 13 is configured to feed a first precipitant (such as an aqueous hydroxide solution, NaOH(aq)) into the first reaction cavity 1b of the first Couette-Taylor reactor 1 through yet another one of the first pump infusion units 153 of the first pump module 15 to mix with the first reaction liquid (such as a multi-metal solution) and the first chelating agent (such as an aqueous ammonia solution) to form a reaction mixture and carry out the coprecipitation reaction.

[0040] The first rotary motor 14 is configured to drive the first rotary axis 1a to rotate along the axial direction, enabling the reaction mixture formed by the first reaction liquid (such as a multi-metal solution), the first chelating agent (such as an aqueous ammonia solution), and the first precipitant (such as an aqueous hydroxide solution) fed into the first reaction cavity 1b of the first Couette-Taylor reactor 1 to react completely.

[0041] The first product stream P1 containing a plurality of core particles formed in the first Couette-Taylor reaction step can be continuously output through at least one outlet of the first Couette-Taylor reactor 1.

[0042] In the first Couette-Taylor reaction step, a first pH monitoring unit 16 is connected to the rear side of the outlet of the first Couette-Taylor reactor 1 to monitor the first pH value (such as pH value) of the first product stream P1.

[0043] In some embodiments of the present invention, in order to improve the reaction efficiency of the first Couette-Taylor reaction step, the first reaction temperature of the first Couette-Taylor reactor 1 is between 45°C and 70°C, and preferably between 50°C and 65°C.

[0044] The rotational speed of the first motor at which the first rotary motor 14 drives the rotation of the first rotation axis 1a is between 500 rpm and 900 rpm, and preferably between 500 rpm and 700 rpm.

[0045] Furthermore, the first residence time of the reaction mixture formed by the first reaction liquid, the first chelating agent, and the first precipitating agent in the first Couette-Taylor reactor 1 is between 300 minutes and 600 minutes, and preferably between 450 minutes and 550 minutes.

[0046] The flow rate of the first reaction liquid (such as a multi-metal solution) fed into the first reaction chamber 1b of the first Couette-Taylor reactor 1 by the first reaction liquid supply unit 11 is between 0.5 mL / min and 3 mL / min, and preferably between 1.0 mL / min and 2.5 mL / min.

[0047] The flow rate of the first chelating agent (such as an aqueous ammonia solution) fed into the first reaction chamber 1b of the first Couette-Taylor reactor 1 by the first chelating agent supply unit 12 is between 0.2 mL / min and 0.8 mL / min, and the flow rate of the first chelating agent is preferably between 0.4 mL / min and 0.7 mL / min.

[0048] The flow rate of the first precipitating agent (such as an aqueous hydroxide solution) fed into the first reaction chamber 1b of the first Couette-Taylor reactor 1 by the first precipitating agent supply unit 13 is regulated so that the first pH value of the first product stream P1 is regulated to a pH between 10 and 12.

[0049] Wherein, the aqueous hydroxide solution is NaOH(aq) with a concentration between 3M and 5M, but the present invention is not limited thereto.

[0050] In the first product stream P1, the core particle size of the core particles (such as ternary alloy hydroxide or quaternary alloy hydroxide) is between 4 microns and 12 microns, and preferably between 6 microns and 10 microns.

[0051] In some embodiments of the present invention, the core particles may be hydroxides of nickel-cobalt-manganese ternary alloy, hydroxides of nickel-cobalt-manganese-magnesium quaternary alloy, or hydroxides of nickel-cobalt-manganese-aluminum quaternary alloy, but the present invention is not limited thereto.

[0052] Step S120 is to implement the second Couette-Taylor reaction step, which includes: feeding the first product stream P1 (including a plurality of core particles) continuously output from the first Couette-Taylor reactor 1 to the second Couette-Taylor reactor 2 connected in series after the first Couette-Taylor reactor 1; and feeding the second reaction liquid to the second Couette-Taylor reactor 2 through the second reaction liquid supply unit 21, so that the second reaction liquid undergoes a surface coating modification reaction on the outer surface of the plurality of core particles, and then functional coating layers are respectively formed on the outer surfaces of the plurality of core particles, thereby forming a second product stream P2 containing a plurality of core-shell structured cathode material precursors (such as core-shell structures with a coating layer covering the outer surface of the core particles).

[0053] Among them, the second reaction liquid is an aqueous solution of a coating material. In this embodiment, the second reaction liquid is an aqueous solution of transition metal (transition metal aqueous solution).

[0054] For example, the aqueous solution of transition metal is at least one of zirconium ion solution, tungsten ion solution, aluminum ion solution, zinc ion solution, titanium ion solution, molybdenum ion solution, and tin ion solution (and preferably zirconium, tungsten, or aluminum ion solution), but the present invention is not limited thereto.

[0055] In some embodiments of the present invention, the zirconium ion solution is zirconium sulfate solution, and the tungsten ion solution is a solution prepared by dissolving sodium tungstate dihydrate and sodium hypophosphite in deionized water. The aluminum ion solution is a solution prepared by dissolving aluminum nitrate in deionized water, but the present invention is not limited thereto.

[0056] More specifically, the second Couette-Taylor reactor 2 includes a second rotation axis 2a and a second reaction cavity 2b that surrounds the second rotation axis 2a in the radial direction. In this embodiment, the second Couette-Taylor reactor 2 is disposed substantially along the axis direction at the rear side of the first Couette-Taylor reactor 1 and is used to receive the first product stream P1 output from the first Couette-Taylor reactor 1.

[0057] The starting position of the second Couette-Taylor reactor 2 (for example, the position close to the first Couette-Taylor reactor 1) is further respectively connected to the second reaction liquid supply unit 21, the second chelating agent supply unit 22, and the second precipitating agent supply unit 23.

[0058] In this embodiment, the position where the second reaction liquid supply unit 21 inputs the second reaction liquid (e.g., an aqueous solution of a coating material) into the second Couette-Taylor reactor 2 and the position where the first product stream P1 is input into the second Couette-Taylor reactor 2 are symmetric with each other in the radial direction of the second Couette-Taylor reactor 2, so that the first product stream P1 and the second reaction liquid can come into sufficient contact with each other, but the present invention is not limited thereto.

[0059] The second Couette-Taylor reactor 2 further includes a second rotary motor 24 connected to the second rotation axis 2a in the axial direction, and the second rotary motor 24 is configured to drive the second rotation axis 2a to rotate along the axial direction.

[0060] Wherein the first product stream P1 is fed into the second reaction cavity 2b of the second Couette-Taylor reactor 2 through another first pump infusion unit 154 of the first pump module 15.

[0061] The second reaction liquid supply unit 21 is configured to feed the second reaction liquid (e.g., an aqueous solution of a coating material) into the second reaction cavity 2b of the second Couette-Taylor reactor 2 through one of the second pump infusion units 251 of the second pump module 25.

[0062] Wherein, the second chelating agent supply unit 22 is configured to feed the second chelating agent (e.g., an aqueous ammonia solution, NH 4 OH(aq)) into the second reaction cavity 2b of the second Couette-Taylor reactor 2 through another second pump infusion unit 252 of the second pump module 25 to be mixed with the second reaction liquid (e.g., an aqueous solution of a coating material) and the first product stream P1 containing a plurality of core particles.

[0063] Wherein, the second precipitating agent supply unit 23 is configured to feed the second precipitating agent (e.g., an aqueous hydroxide solution, NaOH(aq)) into the second reaction cavity 2b of the second Couette-Taylor reactor 2 through another second pump infusion unit 253 of the second pump module 25 to be mixed with the second reaction liquid (e.g., an aqueous solution of a coating material), the second chelating agent (e.g., an aqueous ammonia solution) and the first product stream P1 containing a plurality of core particles, so as to carry out the surface coating modification reaction.

[0064] According to the above configuration, the second Couette-Taylor reactor 2 can continuously form and output a second product stream P2 containing a plurality of core-shell structured cathode material precursors (e.g., core-shell structures in which the outer surfaces of core particles are covered with functional coating layers).

[0065] In the second Couette-Taylor reaction step, a second pH monitoring unit 26 is connected to the rear side of the outlet of the second Couette-Taylor reactor 2 for monitoring the second pH value (such as pH value) of the second product stream P2.

[0066] In some embodiments of the present invention, in order to improve the reaction efficiency of the second Couette-Taylor reaction step, the second reaction temperature of the second Couette-Taylor reactor 2 is between 45 °C and 70 °C, and preferably between 50 °C and 65 °C.

[0067] The second motor speed at which the second rotary motor 24 drives the second rotary axis 2a to rotate is between 400 rpm and 800 rpm, and preferably between 400 rpm and 700 rpm. Preferably, the second motor speed is lower than the first motor speed of the above-mentioned first rotary motor 14, but the present invention is not limited thereto.

[0068] Furthermore, the second residence time of the reaction mixture formed by the second reaction liquid, the second chelating agent, and the second precipitating agent in the second Couette-Taylor reactor 2 is between 150 minutes and 500 minutes, and preferably between 240 minutes and 400 minutes. Preferably, the second residence time of the reaction mixture in the second Couette-Taylor reactor 2 is between 50% and 85% of the first residence time of the reaction mixture in the first Couette-Taylor reactor 1, but the present invention is not limited thereto.

[0069] The second reaction liquid flow rate of the second reaction liquid (such as the aqueous coating material solution) fed into the second reaction chamber 2b of the second Couette-Taylor reactor 2 through the second reaction liquid supply unit 21 is between 0.05 mL / min and 0.30 mL / min, and preferably between 0.10 mL / min and 0.25 mL / min. Further, the second reaction liquid flow rate is between 3% and 20% of the first reaction liquid flow rate (the flow rate of the aqueous multi-metal solution) in the first Couette-Taylor reactor 1, and preferably between 8% and 15%.

[0070] The second chelating agent flow rate of the second chelating agent (such as aqueous ammonia solution) fed into the second reaction chamber 2b of the second Couette-Taylor reactor 2 through the second chelating agent supply unit 22 is between 0.1 mL / min and 0.6 mL / min, and preferably between 0.1 mL / min and 0.5 mL / min.

[0071] The second precipitating agent (e.g., aqueous hydroxide solution) is fed through a second precipitating agent supply unit 23 into the second reaction chamber 2b of the second Couette-Taylor reactor 2, and the flow rate of the second precipitating agent is regulated such that the second pH value of the second product stream P2 is regulated to a pH between 10 and 12. Among them, the aqueous hydroxide solution is NaOH(aq) with a concentration between 3M and 5M, however, the present invention is not limited thereto.

[0072] In the second product stream P2, the cathode material precursor has a core particle (core layer) and a functional coating layer (shell layer) covering the outer surface of the core particle. Among them, the core particle size of the core particle is between 4 microns and 12 microns, and preferably between 6 microns and 10 microns.

[0073] Furthermore, the thickness of the functional coating layer is between 1% and 20% of the core particle size of the core particle, and preferably between 1% and 15%, but the present invention is not limited thereto.

[0074] In some embodiments of the present invention, the core particle may be a hydroxide of a nickel-cobalt-manganese ternary alloy, a hydroxide of a nickel-cobalt-manganese-magnesium quaternary alloy, or a hydroxide of a nickel-cobalt-manganese-aluminum quaternary alloy.

[0075] Furthermore, the functional coating layer is a coating layer containing transition metal elements (such as zirconium, tungsten, aluminum) to produce a protective effect on the core particle.

[0076] It is worth mentioning that the above process condition parameters listed in this embodiment are the parameters for a Couette-Taylor reactor with a volume of one liter (L), however, the present invention is not limited thereto. The volume of the Couette-Taylor reactor can be scaled up to 10 liters to 1000 liters for reaction, and the process condition parameters can be adjusted accordingly.

[0077] Furthermore, the step S130 is to implement a purification step, including: purifying the second product stream P2 containing the cathode material precursor with a core-shell structure output from the second Couette-Taylor reactor 2 to purify the cathode material precursor from the second product stream P2.

[0078] More specifically, the purification step includes: filtering the second product stream P2 to filter out the cathode material precursor, and washing and drying the cathode material precursor to obtain a purified cathode material precursor.

[0079] In some embodiments of the present invention, the purified precursor of the cathode material can be further mixed and ball-milled with a lithium-containing compound (i.e., a lithium source) to obtain a crude product of the cathode oxide; then, the crude product of the cathode oxide is calcined by introducing oxygen into a high-temperature tubular furnace to obtain the cathode oxide, which can be used as the cathode material of a lithium battery.

[0080] In this embodiment, the lithium-containing compound is lithium hydroxide (i.e., LiOH), and the cathode oxide is a nickel-rich cathode oxide, but the present invention is not limited thereto.

[0081] In summary, the embodiments of the present invention provide a method for preparing a precursor of a cathode active material using a Couette-Taylor reactor. This method uses two mutually connected first Couette-Taylor reactors and a second Couette-Taylor reactor to continuously produce a precursor of the cathode active material.

[0082] Among them, the first Couette-Taylor reactor is used to form core particles (i.e., the core part) with uniform element distribution and dense structure by coprecipitation. Furthermore, the second Couette-Taylor reactor is used to perform surface coating modification on the aforementioned core particles to form a precursor of the cathode material with a core-shell structure.

[0083] The embodiments of the present invention can continuously produce a precursor of the cathode material with a core-shell structure (i.e., a core-shell type nickel-rich ternary / quaternary cathode material composite precursor), and under the action of high energy density, the precursor of the cathode material is coated and modified with a functional material, hoping to effectively improve the stability and endurance of the battery, and while achieving high specific capacitance and capacitance retention rate, taking into account the safety of the material.

[0084] The method of the embodiments of the present invention uses mutually connected first Couette-Taylor reactors and a second Couette-Taylor reactor to replace the traditional continuous stirred reactor, and uses coprecipitation to prepare the precursor. By adjusting the reaction temperature, rotation speed, and precipitation agent dropping time, the particle size, crystallinity, specific surface area, etc. of the precursor are controlled. Therefore, the method of the embodiments of the present invention is suitable for industrial continuous production.

[0085] The method of the embodiments of the present invention passes an aqueous solution of the coating material through the second Couette-Taylor reactor, and performs heat treatment and coating on the above-mentioned core particles in Taylor flow to form a functional coating layer.

[0086] The thickness of the functional coating layer is thin and uniform, and can completely cover the cathode core particles, so that the cathode core particles are protected from electrolyte attack, thereby inhibiting the occurrence of side reactions.

[0087] The method of the embodiment of the present invention improves the disadvantages of common production methods, such as: the impregnation method cannot be continuously produced, the dry coating method is prone to uneven distribution, the sputtering method and the atomic layer deposition method have expensive equipment, etc. and cannot be continuously produced. The precursor of the cathode material of the embodiment of the present invention has undergone long-term charge and discharge tests, and its particle cracks are fewer than those of the cathode core particles without a functional coating layer. When used in a lithium battery, the cycle life of the lithium battery is significantly improved.

[0088] [Experimental data and test results]

[0089] Hereinafter, the content of the present invention will be described in detail with reference to Examples 1 to 3 and Comparative Example 1. However, the following examples are only for helping to understand the present invention, and the scope of the present invention is not limited to these examples.

[0090] <Example 1>

[0091] Feed a multi-metal solution (i.e., an aqueous solution mixed in a molar ratio of 8:1:1 of NiSO 4 : CoSO 4 : MnSO 4 ), and the molar concentration of the multi-metal is 2M) into the first Couette-Taylor reactor, and additionally feed the precipitating agent NaOH(aq) and the chelating agent NH 4 OH(aq) into the first Couette-Taylor reactor to carry out a co-precipitation reaction, thereby forming a solution containing nickel-cobalt-manganese ternary alloy hydroxide particles.

[0092] Among them, the reaction temperature of the first Couette-Taylor reactor is 60°C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 500 min, the flow rate of the feed material (multi-metal solution) is 1.5 mL / min, the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min, and the flow rate of the precipitating agent NaOH(aq) (concentration 4M) is adjusted so that the pH value of the solution is controlled at pH = 11.

[0093] Then, feed the solution containing nickel-cobalt-manganese ternary alloy hydroxide particles output from the above-mentioned first Couette-Taylor reactor into the second Couette-Taylor reactor, and additionally feed an aqueous solution of the coating material (i.e., zirconium sulfate solution, and the molar concentration is 1M), another precipitating agent NaOH(aq), and another chelating agent NH 4 OH(aq) into the second Couette-Taylor reactor, thereby forming a transition metal coating material layer on the surface of the nickel-cobalt-manganese ternary alloy hydroxide particles, and generating a solution containing a core-shell structured cathode material precursor.

[0094] Among them, the reaction temperature of the second Couette-Taylor reactor is 60 °C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 377 min, the flow rate of the feed material (coating material aqueous solution) is 0.15 mL / min, and the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min. The flow rate of the precipitating agent NaOH(aq) (concentration 4 M) is adjusted to control the pH value of the solution at pH = 11.

[0095] Finally, the solution containing the core-shell structured cathode material precursor is filtered, washed, and dried, and then mixed and ball-milled with a lithium source (lithium hydroxide). Then, it is calcined by introducing oxygen through a high-temperature tubular furnace to obtain a nickel-rich cathode oxide. After that, the nickel-rich cathode oxide is subjected to an electrochemical performance test.

[0096] <Example 2>

[0097] A multi-metal solution (i.e., an aqueous solution mixed in a molar ratio of 8:1:1 of NiSO 4 : CoSO 4 : MnSO 4 with a molar concentration of 2 M of the multi-metal) is fed into the first Couette-Taylor reactor, and the precipitating agent NaOH(aq) and the chelating agent NH 4 OH(aq) are also fed into the first Couette-Taylor reactor to carry out a co-precipitation reaction, thereby forming an aqueous solution containing nickel-cobalt-manganese ternary alloy hydroxide particles. Among them, the reaction temperature of the first Couette-Taylor reactor is 60 °C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 500 min, the flow rate of the feed material (multi-metal solution) is 1.5 mL / min, the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min, and the flow rate of the precipitating agent NaOH(aq) (concentration 4 M) is adjusted to control the pH value of the solution at pH 11.

[0098] Then, the solution containing nickel-cobalt-manganese ternary alloy hydroxide particles output from the above-mentioned first Couette-Taylor reactor is fed into the second Couette-Taylor reactor, and an aqueous solution of the coating material (i.e., a tungsten ion solution with a molar concentration of 0.1 M), another precipitating agent NaOH(aq), and another chelating agent NH 4 OH(aq) are also fed into the second Couette-Taylor reactor, thereby forming a transition metal coating material layer on the surface of the nickel-cobalt-manganese ternary alloy hydroxide particles, generating a solution containing a core-shell structured cathode material precursor.

[0099] Among them, the reaction temperature of the second Couette-Taylor reactor is 60 °C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 377 min, the flow rate of the feed material (coating material aqueous solution) is 0.15 mL / min, and the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min. The flow rate of the precipitating agent NaOH(aq) (concentration 4 M) is regulated to control the pH value of the solution at pH = 11.

[0100] Finally, the solution containing the core-shell structured cathode material precursor is filtered, washed, and dried, and then mixed and ball-milled with a lithium source (lithium hydroxide). Subsequently, it is calcined by introducing oxygen in a high-temperature tubular furnace to obtain a nickel-rich cathode oxide. After that, the electrochemical properties of the nickel-rich cathode oxide are tested.

[0101] <Example 3>

[0102] A multi-metal solution (i.e., an aqueous solution mixed according to a molar ratio of NiSO 4 : CoSO 4 : MnSO 4 : MgSO 4 at 8:1:0.9:0.1) with a volume molar concentration of 2 M for the multi-metal is fed into the first Couette-Taylor reactor, and the precipitating agent NaOH(aq) and the chelating agent NH 4 OH(aq) are fed into the first Couette-Taylor reactor to carry out a co-precipitation reaction, thereby forming a solution containing nickel-cobalt-manganese ternary alloy hydroxide particles.

[0103] Among them, the reaction temperature of the first Couette-Taylor reactor is 60 °C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 500 min, the flow rate of the feed material (multi-metal solution) is 1.5 mL / min, and the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min. The flow rate of the precipitating agent NaOH(aq) (concentration 4 M) is regulated to control the pH value of the solution at pH = 11.2.

[0104] Then, the solution containing nickel-cobalt-manganese-magnesium quaternary alloy hydroxide particles output from the above first Couette-Taylor reactor is fed into the second Couette-Taylor reactor, and an aqueous solution of a coating material (i.e., an aluminum ion solution with a volume molar concentration of 1 M), another precipitating agent NaOH(aq), and another chelating agent NH 4 OH(aq) are fed into the second Couette-Taylor reactor, thereby forming a transition metal coating material layer on the surface of the nickel-cobalt-manganese-magnesium quaternary alloy hydroxide particles, generating a solution containing a core-shell structured cathode material precursor.

[0105] Among them, the reaction temperature of the second Couette-Taylor reactor is 60 °C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 384 min, the flow rate of the feed material (coating material aqueous solution) is 0.15 mL / min, and the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min. The flow rate of the precipitating agent NaOH(aq) (concentration 4 M) is adjusted to control the pH value of the solution at pH = 11.2.

[0106] Finally, after filtering, washing, and drying the solution containing the core-shell structured cathode material precursor, it is continuously mixed and ball-milled with a lithium source (lithium hydroxide), and then calcined by introducing oxygen into a high-temperature tubular furnace to obtain a nickel-rich cathode oxide. After that, the electrochemical properties of the nickel-rich cathode oxide are tested.

[0107] <Comparative Example 1>

[0108] A multi-metal solution (i.e., an aqueous solution mixed in a molar ratio of NiSO 4 : CoSO 4 : MnSO 4 at 8:1:1) with a molar concentration of 2 M of the multi-metal is fed into a single Couette-Taylor reactor, and the precipitating agent NaOH(aq) and the chelating agent NH 4 OH(aq) are additionally fed into the Couette-Taylor reactor to carry out a co-precipitation reaction, thereby forming a solution containing nickel-cobalt-manganese ternary alloy hydroxide particles. Among them, the reaction temperature of the first Couette-Taylor reactor is 60 °C, the motor speed is 600 rpm, the average residence time (retention time) of the material is 500 min, the flow rate of the feed material (multi-metal solution) is 1.5 mL / min, and the flow rate of the chelating agent NH 4 OH(aq) is 0.5 mL / min. The flow rate of the precipitating agent NaOH(aq) (concentration 4 M) is adjusted to control the pH value of the solution at pH = 11.

[0109] Finally, after filtering, washing, and drying the solution containing the nickel-cobalt-manganese ternary alloy hydroxide particles, it is continuously mixed and ball-milled with a lithium source (lithium hydroxide), and then calcined by introducing oxygen into a high-temperature tubular furnace to obtain the cathode oxide of Comparative Example 1. After that, the electrochemical properties of the cathode oxide are tested.

[0110] The main difference between Comparative Example 1 and the above Examples 1 to 3 is that Comparative Example 1 only uses a single Couette-Taylor reactor to prepare the core particles and does not form a functional coating layer on the core particles.

[0111] A more detailed description of the preparation of the positive electrode oxide (i.e., the positive electrode material of the lithium battery) in the above-mentioned examples and comparative examples is as follows.

[0112] The positive electrode oxide was prepared by using a solid-phase reaction method (i.e., planetary ball milling) with a precursor and a lithium salt (LiOH·H 2 O, 98%, Sigma-Aldrich) to prepare an oxide positive electrode material with a chemical composition of LiNi0.8Co0.1Mn0.1XZO 2 (abbreviated as NCM811, where X is the surface metal), and the molar ratio of the precursor to the lithium salt is 1:1.05.

[0113] Then, the above mixed material was calcined in a pure oxygen (O 2 ) atmosphere at 830 °C for 12 hours.

[0114] <Electrochemical property test>

[0115] The electrical property tests of Examples 1 to 3 and Comparative Example 1 were carried out on a button-type CR2032 battery for the assembly and electrical property test of the positive electrode and the lithium metal negative electrode.

[0116] First, the positive electrode electrode formula was made into an electrode slurry (including positive electrode active material, Super P conductive additive, and PVDF adhesive) through processing steps such as slurry stirring, coating, drying, rolling, and cutting.

[0117] Then, the obtained positive electrode sheet was assembled into a CR2032 half-cell, and then the specific discharge capacity detection and analysis of the synthesized material, and the analysis of electrochemical performance indexes (KPIs) such as discharge specific capacity, Coulombic efficiency (CE%), and specific capacity retention (CR%) were carried out.

[0118] The electrical property test results of Examples 1 to 3 and Comparative Example 1 are shown in Table 1 below.

[0119] [Table 1]

[0120]

[0121] From the experimental results in Table 1 above, it can be seen that the 100-cycle retention rates of Examples 1 to 3 have better performance (i.e., the cycle retention rates of 81.95% to 91.56%). Furthermore, the positive electrode materials of Examples 1 to 3 were tested for 500 charge-discharge cycles, and there were no obvious cracks on the surface of the positive electrode materials.

[0122] In terms of the analysis of the scanning electron microscope (SEM), Figure 2AShown is the SEM experimental photograph of the positive electrode material with a core-shell structure in Example 3 of the present invention. Figure 2B Shown is the SEM experimental photograph of the positive electrode material with only single-layer core particles in Comparative Example 1.

[0123] Figure 3A Shown is the SEM experimental photograph of the positive electrode material with a core-shell structure in Example 3 of the present invention after 500 charge-discharge cycle tests. Figure 3B Shown is the SEM experimental photograph of the positive electrode material with only single-layer core particles in Comparative Example 1 after 500 charge-discharge cycle tests. Figure 4A is Figure 3A the SEM experimental photograph of the cross-section of the positive electrode material of Figure 4B is Figure 3B the SEM experimental photograph of the cross-section of the positive electrode material of. Among them, Figure 3A and Figure 4A after the positive electrode material with a core-shell structure has undergone 500 charge-discharge cycle tests, no obvious cracks are observed on the surface of the material. Figure 3B and Figure 4B after the positive electrode material with only single-layer core particles in

[0124] [Advantages of the Embodiment]

[0125] One of the advantages of the present invention is that the method for preparing the precursor of the positive electrode material using a Couette-Taylor reactor provided by the present invention can replace the traditional continuous stirred tank reactor through the technical solution of "implementing the first Couette-Taylor reaction step, including: feeding the first reaction liquid into the first Couette-Taylor reactor and performing a co-precipitation reaction to form and continuously output a first product stream containing a plurality of core particles; wherein, the first reaction liquid is a multi-metal solution" and "implementing the second Couette-Taylor reaction step, including: feeding the first product stream into the second Couette-Taylor reactor connected in series after the first Couette-Taylor reactor; and feeding the second reaction liquid into the second Couette-Taylor reactor so that the second reaction liquid forms a functional coating layer on the outer surface of each of the plurality of core particles, thereby forming a second product stream containing a plurality of positive electrode material precursors with a core-shell structure; wherein, the second reaction liquid is an aqueous solution of the coating material, and the aqueous solution of the coating material is an aqueous solution of a transition metal; and implementing a purification step, including: purifying the second product stream to purify and separate a plurality of the positive electrode material precursors with a core-shell structure", and can achieve continuous production.

[0126] Among them, the first Couette-Taylor reactor is used to form core particles with uniform element distribution and dense structure by coprecipitation method. The second Couette-Taylor reactor is used to perform surface coating modification on the aforementioned core particles, so as to form a precursor of the cathode material with a core-shell structure.

[0127] The method of the present invention can continuously produce a precursor of the cathode material with a core-shell structure, which can effectively improve the stability and endurance of lithium batteries, and take into account the safety of the materials.

[0128] The content disclosed above is only the preferred and feasible embodiment of the present invention, and does not limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made by using the content of the specification and drawings of the present invention are included in the scope of the patent application of the present invention.

Claims

1. A method for preparing a precursor of a cathode material using a Couette-Taylor reactor, characterized in that, the method comprises: performing a first Couette-Taylor reaction step, including: feeding a first reaction liquid into a first Couette-Taylor reactor and performing a coprecipitation reaction to form and continuously output a first product stream containing a plurality of core particles; wherein the first reaction liquid is a multi-metal solution; performing a second Couette-Taylor reaction step, including: feeding the first product stream into a second Couette-Taylor reactor connected in series after the first Couette-Taylor reactor; and feeding a second reaction liquid into the second Couette-Taylor reactor so that a functional coating layer is formed on the outer surface of each of the plurality of core particles, thereby forming a second product stream containing a plurality of core-shell structured cathode material precursors; wherein the second reaction liquid is an aqueous solution of a coating material, and the aqueous solution of the coating material is an aqueous solution of a transition metal; and performing a purification step, including: purifying the second product stream to purify and separate a plurality of the core-shell structured cathode material precursors from the second product stream.

2. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 1, characterized in that, the multi-metal solution contains at least three of nickel compound, cobalt compound, manganese compound, magnesium compound, and aluminum compound; wherein each of the core particles is at least one of a ternary alloy hydroxide core particle and a quaternary alloy hydroxide core particle.

3. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 1, characterized in that, the aqueous solution of the transition metal is at least one of a zirconium ion solution, a tungsten ion solution, an aluminum ion solution, a zinc ion solution, a titanium ion solution, a molybdenum ion solution, and a tin ion solution.

4. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 1, characterized in that, the flow rate of the second reaction liquid fed into the second Couette-Taylor reactor is 3% to 20% of the flow rate of the first reaction liquid fed into the first Couette-Taylor reactor.

5. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 1, characterized in that, the flow rate of the first reaction liquid fed into the first Couette-Taylor reactor is between 0.5 mL / min and 3 mL / min; wherein the flow rate of the second reaction liquid fed into the second Couette-Taylor reactor is between 0.05 mL / min and 0.30 mL / min, and the flow rate of the second reaction liquid is 3% to 20% of the flow rate of the first reaction liquid.

6. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 1, characterized in that, The first reaction temperature in the first Couette-Taylor reactor is between 45°C and 70°C, and the rotational speed of the first rotary motor of the first Couette-Taylor reactor is between 500 rpm and 900 rpm.

7. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 6, wherein, the second reaction temperature in the second Couette-Taylor reactor is between 45°C and 70°C, and the rotational speed of the second rotary motor of the second Couette-Taylor reactor is between 400 rpm and 800 rpm.

8. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 1, wherein, the first Couette-Taylor reaction step further comprises: feeding a first chelating agent and a first precipitating agent into the first Couette-Taylor reactor respectively to be mixed with the first reaction liquid to form a reaction mixture; wherein, the first residence time of the reaction mixture in the first Couette-Taylor reactor is between 300 minutes and 600 minutes.

9. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to claim 8, wherein, the second Couette-Taylor reaction step further comprises: feeding a second chelating agent and a second precipitating agent into the second Couette-Taylor reactor respectively to be mixed with the second reaction liquid to form another reaction mixture; wherein, the second residence time of the another reaction mixture in the second Couette-Taylor reactor is between 150 minutes and 500 minutes, and the second residence time is 50% to 85% of the first residence time.

10. The method for preparing a precursor of a cathode material using a Couette-Taylor reactor according to any one of claims 1 to 9, wherein, in each of the core-shell structured cathode material precursors, the core particle size of the core particles is between 4 microns and 12 microns, and the thickness of the functional coating layer is between 1% and 20% of the core particle size of the core particles.

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