Classifier for positive active material and method for regenerating lithium precursor using the same

Abstract

In a method for regenerating a lithium precursor, a positive electrode active material mixture including dust particles and an active material powder containing lithium composite oxide particles is prepared. The dust particles are separated from the positive electrode active material mixture using a classifier to collect the active material powder. The active material powder is reduced to form a primary precursor mixture. A lithium precursor is recovered from the primary precursor mixture. A high-purity lithium precursor can be obtained at a high yield.

Description

[0001] Cross-reference to related applications

[0002] This application is a divisional application of Chinese Patent Application No. 202180021962.3, filed on March 12, 2021, entitled "A classifier for positive electrode active materials and a method for using the regenerated lithium precursor thereof". This patent application claims the benefit of priority to Korean Patent Application No. KR10-2020-0033965, filed on March 19, 2020, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to a classifier for positive electrode active materials and a method for regenerating lithium precursors using the classifier. More specifically, this invention relates to a classifier for positive electrode active materials and a method for regenerating lithium precursors from spent lithium compounds using the classifier. Background Technology

[0004] With the development of information and display technologies, rechargeable and dischargeable secondary batteries have been widely used as power sources for mobile electronic devices such as portable cameras, mobile phones, and laptops. Secondary batteries include, for example, lithium-ion batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Lithium-ion batteries are actively being developed and applied in the battery industry due to their high operating voltage and energy density per unit weight, high charge rate, and compact size.

[0005] A lithium secondary battery may include an electrode assembly comprising a positive electrode, a negative electrode, a separator layer (separator), and an electrolyte immersing the electrode assembly. The lithium secondary battery may further include a housing having, for example, a pouch shape for housing the electrode assembly and the electrolyte.

[0006] Lithium metal oxides can be used as positive electrode active materials in lithium secondary batteries. Lithium metal oxides may also contain transition metals, such as nickel, cobalt, and manganese.

[0007] Lithium metal oxides, which are positive electrode active materials, can be prepared by reacting lithium precursors with nickel-cobalt-manganese (NCM) precursors containing nickel, cobalt, and manganese.

[0008] Because these high-cost metals are used in the cathode active material, manufacturing the cathode material requires more than 20% of the production cost. Furthermore, due to recent concerns about environmental protection, methods for recycling cathode active materials are being researched. The recycling of cathode active materials requires the efficient and high-purity regeneration of lithium precursors from spent cathodes.

[0009] For example, Korean Patent Application No. 2015-0002963 discloses a method for recovering lithium using a wet process. However, lithium is recovered from the waste liquid remaining after the extraction of cobalt, nickel, etc., through wet extraction, resulting in an excessively low recovery rate and the potential generation of a large number of impurities from the waste liquid.

[0010] (Patent Document 1) Korean Patent No. 2015-0002963 Summary of the Invention

[0011] [Technical Objectives]

[0012] According to one aspect of the present invention, a classifier for recovering lithium precursors with high purity and high yield is provided, as well as a method for regenerating lithium precursors using the classifier.

[0013] [Technical means]

[0014] In a method for regenerating lithium precursors according to an embodiment of the present invention, a positive electrode active material mixture is prepared, the mixture comprising active material powder containing lithium composite oxide particles and dust particles. The dust particles are separated from the positive electrode active material mixture using a classifier to collect the active material powder. The active material powder is reduced to form a primary precursor mixture. The lithium precursor is recovered from the primary precursor mixture.

[0015] In an exemplary embodiment, dust particles may include particles derived from carbon-based conductive materials and adhesives.

[0016] In an exemplary embodiment, the active substance powder can be graded into a first active substance powder and a second active substance powder to be collected separately.

[0017] In an exemplary embodiment, the average particle size of the second active substance powder may be smaller than the average particle size of the first active substance powder.

[0018] In an exemplary embodiment, the collected first active substance powder can be reduced to form a primary precursor mixture, and the collected second active substance powder can be treated with an acid solution.

[0019] In an exemplary embodiment, the separation of dust particles and the classification of the first active substance powder and the second active substance powder can be performed together in a classifier.

[0020] In an exemplary embodiment, the reduction of the active material powder can be carried out using a reduction reaction gas in a fluidized bed reactor.

[0021] In an exemplary embodiment, recovering lithium precursors from a primary precursor mixture may include washing the primary precursor mixture with water.

[0022] In an exemplary embodiment, a classifier for positive electrode active materials includes: an active material inlet through which a mixture of positive electrode active materials comprising active material powder containing lithium composite oxide particles and dust particles is injected; a classification body including a classification sieve for classifying the active material powder into a first active material powder and a second active material powder; an upper outlet located at the upper part of the classification body to allow dust particles to disperse and be discharged from the positive electrode active material mixture; an active material outlet connected to the center of the classification body to discharge the first active material powder; and a lower outlet connected to the lower part of the classification body to discharge the second active material powder from the positive electrode active material mixture.

[0023] In an exemplary embodiment, a fluid inlet may be further included, located at the lower part of the graded body, through which fluid is injected.

[0024] [Invention Effects]

[0025] According to the exemplary embodiments described above, a classifier can be used to separate dust particles from a mixture of positive electrode active materials, and active material powder containing lithium composite oxide particles can be collected. In this case, the active material powder can have improved reduction processing efficiency, thus making it easier to obtain lithium precursors with high yield and high purity.

[0026] In some implementations, the dust particles may include particles derived from carbon-based conductive materials and binders. In this case, the carbon-based particles can be separated from the positive electrode active material mixture, allowing the collection of active material powder with a low concentration of carbon-based particles. Therefore, potential side reactions during the reduction process can be minimized, and the recovery rate of lithium precursors can be further improved.

[0027] In some embodiments, the active material powder can be divided into a first active material powder and a second active material powder with an average particle size smaller than that of the first active material powder. In this case, only the first active material powder with a relatively large average particle size can be fluidized.

[0028] Therefore, the recovery of lithium precursors from the first active material powder can be carried out through a reduction reaction, and the recovery of lithium precursors from the second active material powder can be carried out through an acid treatment process. Attached Figure Description

[0029] Figure 1 This is a schematic flowchart for describing a method for producing a recycled lithium precursor according to an exemplary embodiment.

[0030] Figure 2 A schematic cross-sectional view is provided to illustrate a grading machine according to an exemplary embodiment. Detailed Implementation

[0031] According to an embodiment of the present invention, a method is provided for regenerating lithium precursors with high purity and high efficiency using active material powder, which is formed by removing dust particles from a mixture of positive electrode active materials in a classifier.

[0032] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings. However, these embodiments are provided by way of example, and the invention is not limited to the specific embodiments described herein.

[0033] The term "precursor" in this application is used in general to refer to a compound containing a specific metal to provide a specific metal contained in a positive electrode active material.

[0034] Figure 1 This is a schematic flowchart for describing a method for producing a recycled lithium precursor according to an exemplary embodiment.

[0035] In an exemplary embodiment, a positive electrode active material mixture comprising active material powder containing lithium complex oxide and dust particles can be prepared. The positive electrode active material mixture may include lithium-containing compounds obtained or regenerated from electrical or chemical devices. Non-limiting examples of the positive electrode active material mixture may include various lithium-containing compounds, such as lithium oxide, lithium carbonate, lithium hydroxide, etc.

[0036] In an exemplary embodiment, the positive electrode active material mixture may include active material powder and dust particles obtained from waste lithium secondary batteries (e.g., in step S10).

[0037] Waste lithium secondary batteries may include an electrode assembly comprising a positive electrode, a negative electrode, and a separator layer between the positive and negative electrodes. For example, the positive and negative electrodes may comprise a positive active material layer coated on a positive current collector and a negative active material layer coated on a negative current collector, respectively.

[0038] For example, the positive electrode active material contained in the positive electrode active material layer may include lithium composite oxide containing lithium and transition metals.

[0039] In some implementations, the positive electrode active material may include a lithium composite oxide represented by the following chemical formula 1.

[0040] [Chemical Formula 1]

[0041] Li x M1 a M2 b M3 c O y

[0042] In Chemical Formula 1, M1, M2, and M3 may be transition metals selected from Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, or B. In Chemical Formula 1, 0 < x ≤ 1.1, 2 ≤ y ≤ 2.2, 0 < a < 1, 0 < b < 1, 0 < c < 1, and 0 < a + b + c ≤ 1.

[0043] In some embodiments, the positive electrode active material may include an NCM-based lithium composite oxide including nickel, cobalt, and manganese. The NCM-based lithium composite oxide may be prepared by reacting a lithium precursor and an NCM precursor (e.g., an NCM oxide) with each other through a coprecipitation reaction.

[0044] However, embodiments of the present invention can generally be applied to positive electrode materials including NCM-based lithium composite oxides and lithium composite oxide positive electrode materials containing lithium.

[0045] For example, a waste positive electrode can be recovered by separating the positive electrode from a waste lithium secondary battery. The positive electrode may include a positive electrode current collector (e.g., aluminum (Al)) and a positive electrode active material layer as described above, and the positive electrode active material layer may include a conductive material, a binder, and the above positive electrode active material.

[0046] In some exemplary embodiments, the positive electrode active material mixture may further include a carbon-based conductive material, a binder, and a lithium composite oxide.

[0047] The carbon-based conductive material may include, for example, carbon-based materials such as graphite, carbon black, graphene, carbon nanotubes, etc. The binder may include resin materials such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, etc.

[0048] The positive electrode active material mixture may be prepared from the recovered positive electrode. In some embodiments, the positive electrode active material mixture may be obtained in the form of powder through physical treatment such as grinding treatment. As described above, the positive electrode active material mixture may include active material powder containing lithium composite oxide particles derived from the positive electrode active material. For example, the lithium composite oxide particles may include NCM-based lithium oxide powder (e.g., Li(NCM)O2).

[0049] In some embodiments, the recovered positive electrode may be heat-treated before the grinding treatment. Thus, during the grinding treatment, separation of the positive electrode current collector can be promoted, and the binder and the conductive material can be at least partially removed. The temperature of the heat treatment may be, for example, about 100°C to 500°C, preferably about 350°C to 450°C.

[0050] In some implementations, a mixture of positive electrode active materials can be obtained after immersing the recovered positive electrode in an organic solvent. For example, the recovered positive electrode can be immersed in an organic solvent to separate and remove the positive electrode current collector, and the mixture of positive electrode active materials can be selectively extracted by centrifugation.

[0051] Through the above process, a mixture of positive electrode active materials can be obtained, in which the content of positive electrode current collector components and carbon-based components derived from conductive materials and / or binders is substantially removed or reduced.

[0052] For example, the positive electrode active material mixture may include dust particles. For example, the dust particles may include particles derived from carbon-based conductive materials and binders (e.g., carbon black). The dust particles may also include powder formed by physically pulverizing the carbon-based conductive materials and binders.

[0053] In an exemplary embodiment, a classifier 100 can be used to separate dust particles 60 from the positive electrode active material mixture to collect active material powder 70 including lithium composite oxide particles (e.g., in step S20).

[0054] Figure 2 A schematic cross-sectional view is provided to illustrate a grading machine according to an exemplary embodiment.

[0055] For example, the classifier 100 may include an active material inlet 150 through which a mixture of positive electrode active material containing active material powder 70 of lithium composite oxide particles and dust particles 60 is injected; a classification body 110, which includes a classification sieve 115 for classifying the active material powder 70 into a first active material powder and a second active material powder; an upper outlet 120 located at the upper part of the classification body 110, through which dust particles 60 are dispersed and discharged from the positive electrode active material mixture; an active material outlet 140 connected to the center of the classification body 110 to discharge the first active material powder; and a lower outlet 130 connected to the lower part of the classification body 110 to discharge the second active material powder.

[0056] In some exemplary embodiments, the classifier 100 may further include a fluid inlet 160 located at the lower part of the classifying body 110, and fluid may be injected into the fluid inlet 160.

[0057] For example, the classifier 100 can remove dust particles 60 from the positive electrode active material mixture by means of fluid flowing into the classifier body 110. In this case, active material powder 70, in which at least some of the dust particles 60 have been removed, can be collected from the positive electrode active material mixture.

[0058] In this case, the density of dust particles 60 can be less than the density of active material powder 70, so that they can be dispersed and removed from the positive electrode active material mixture by the fluid.

[0059] Therefore, when the dust particles 60 contained in the active material powder 70 include particles derived from carbon-based conductive materials and binders, and when the dust particles 60 contained in the active material powder 70 are separated, the particles derived from carbon-based conductive materials and binders in the active material powder 70 can be separated, thereby suppressing possible side reactions in the hydrogen reduction process described below, thereby improving the recovery rate of lithium precursors.

[0060] For example, the fluid can be a liquid or a gas. For example, the fluid can be a non-reactive fluidizing gas. For example, a non-reactive fluidizing gas can include nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), or xenon (Xe).

[0061] The fluid can form a cyclone through a propeller or the like located inside the staged body 110. In this case, dust particles 60 can be removed from the positive electrode active material mixture by means of the cyclone.

[0062] In some exemplary embodiments, dust particles 60 may disperse to the upper part of the classification body 110 and be discharged through the upper outlet 120 located on the upper part of the classification body 110. The dust particles 60 discharged through the upper outlet 120 may be conveyed to the dust collection unit 200 for collection.

[0063] For example, the dust collection unit 200 can create a negative pressure inside the upper outlet 120 to draw in dust particles 60. For example, the dust particles 60 drawn into the upper outlet 120 can be collected by electrostatic discharge formed in the dust collection unit 200.

[0064] In some exemplary embodiments, the active material powder 70 formed by separating dust particles 60 from the positive electrode active material mixture may include lithium composite oxide particles derived from the positive electrode active material.

[0065] For example, lithium composite oxide particles may include a first lithium composite oxide particle 80 and a second lithium composite oxide particle 90 with different average particle sizes. For example, the average particle size (D50) of the first lithium composite oxide particle 80 may be larger than the average particle size (D50) of the second lithium composite oxide particle 90.

[0066] In this case, the first lithium composite oxide particles 80 may have a suitable particle size value that allows them to be easily fluidized in a fluidized bed reactor, and the average particle size (D50) of the second lithium composite oxide particles 90 may be smaller than the average particle size (D50) of the first lithium composite oxide particles 80, and may include fine particles that can be dispersed rather than fluidized in a fluidized bed reactor.

[0067] In this case, the average particle size (D50) of the first lithium composite oxide particle 80 can be in the range of about 10 μm to 100 μm, and the particle size distribution (PSD) can be in the range of about 10 μm to 300 μm. The average particle size (D50) of the second lithium composite oxide particle 90 can be in the range of about 1 μm to 5 μm, and the particle size distribution (PSD) can be in the range of 0.1 µm to 10 µm.

[0068] In some exemplary embodiments, the active substance powder 70 can be graded into a first active substance powder and a second active substance powder that can be collected separately. In this case, the first active substance powder and the second active substance powder can be graded by a grading sieve 115.

[0069] For example, the first active material powder can be defined as an active material powder that is easily fluidized in a fluidized bed reactor, and the second active material powder can be defined as an active material powder that is dispersed inside the fluidized bed reactor.

[0070] For example, the first active material powder may include first lithium composite oxide particles 80, and the second active material powder may include second lithium composite oxide particles 90.

[0071] For example, the first active material powder and the second active material powder may each include both the first lithium composite oxide particles 80 and the second lithium composite oxide particles 90. However, the first active material powder may include a high proportion of the first lithium composite particles 80 to be easily fluidized in the fluidized bed reactor, and the second active material powder may have a high proportion of the second lithium composite oxide particles 90 to be dispersed inside the fluidized bed reactor.

[0072] For example, the grading sieve 115 can be a porous plate with fine pores, allowing particles within a predetermined particle size range to pass through only the pores. In this case, the active substance powder 70 can be graded into a first active substance powder and a second active substance powder by the grading sieve 115. For example, the grading sieve 115 can be subjected to three-dimensional vibration by the eccentric rotation of a rotating weight located at the lower part of the grading sieve 115, and through the three-dimensional vibration of the grading sieve 115, the active substance powder 70 can be graded into a first active substance powder and a second active substance powder.

[0073] For example, three-dimensional vibrations can include circular vibrations, elliptical vibrations, and linear vibrations caused by the eccentric rotation of a rotating weight.

[0074] For example, the separation efficiency of each particle size in the grading sieve 115 can be 60% to 90%. For example, the grading sieve 115 can include pores. For example, the pores can be quadrilateral (e.g., square).

[0075] For example, the size of the pore can be from about 5 μm to 60 μm. Preferably, the size of the pore can be from about 15 μm to 50 μm, more preferably from about 25 μm to 40 μm.

[0076] In some exemplary embodiments, the grading sieve 115 may have a multi-level structure in which multiple sieves are stacked. For example, the multi-level structure may include five or more sieves. Preferably, the multi-level structure may include 10 or more sieves, more preferably 20 or more sieves.

[0077] For example, when the grading sieve 115 includes a multi-stage structure, the separation efficiency between the first active substance powder and the second active substance powder can be further improved.

[0078] In some exemplary embodiments, the average particle size (D50) of the second active material powder may be smaller than the average particle size (D50) of the first active material powder.

[0079] For example, active material powder that does not pass through the grading sieve 115 can be defined as first active material powder, and active material powder that passes through the grading sieve 115 can be defined as second active material powder. In this case, most of the second lithium composite oxide particles 90 can pass through the grading sieve 115 contained in the grading body 110. However, only a portion of the first lithium composite oxide particles 80 can pass through the grading sieve 115, and most of the first lithium composite oxide particles 80 may not pass through the grading sieve 115.

[0080] In some exemplary embodiments, the ratio of pore size to the average particle size (D50) of the second active material powder can be in the range of about 1.5 to 5. Preferably, the ratio of pore size to the average particle size (D50) of the second active material powder can be in the range of 2.5 to 4.

[0081] For example, when the ratio of the pore size to the average particle size (D50) of the second active material powder meets the above-mentioned range, the second active material powder can be separated from the first active material powder more efficiently. For example, within the above-mentioned range, the separation rate of the second active material powder can be 90% or more.

[0082] Therefore, the first active material powder may have a higher proportion of first lithium composite oxide particles 80 than the second active material powder, and the second active material powder may have a higher proportion of second lithium composite oxide particles 90 than the first active material powder.

[0083] For example, the first active material powder may have a high proportion of easily fluidized first lithium composite oxide particles 80, thereby further improving the efficiency of the reduction process and the efficiency of lithium precursor recovery described later. Conversely, the second active material powder may have a high proportion of poorly fluidized second lithium composite oxide particles 90, and therefore may not be suitable for the reduction process described later. In this case, the lithium precursor can be recovered by acid treatment of the second active material powder.

[0084] In some exemplary embodiments, the ratio of the average particle size of the first lithium composite oxide particles 80 to the average particle size of the second lithium composite oxide particles 90 can be in the range of about 2 to 100. Within this particle size ratio range, the content of the first lithium composite oxide particles 80 contained in the first active material powder can be maximized, and the content of the first lithium composite oxide particles 80 contained in the second active material powder can be minimized. Therefore, the recovery efficiency of lithium precursors can be further improved.

[0085] For example, the proportion of the first lithium composite oxide particles 80 in the lithium composite oxide particles contained in the first active material powder can be 95% or more. For example, the proportion of the second lithium composite oxide particles 90 in the lithium composite oxide particles contained in the second active material powder can be 50% or more. Within these ranges, it is easier to improve the recovery efficiency of the lithium precursor.

[0086] In some exemplary embodiments, the first active substance powder can be discharged through the active substance outlet 140 connected to the center of the grading body 110, and the second active substance powder can be discharged through the lower outlet 130 connected to the lower part of the grading body 110.

[0087] In some exemplary embodiments, the separated second active material powder can be treated with an acid solution. In this case, the lithium precursor can be recovered from the second active material powder by acid treatment. Therefore, the recovery efficiency of the lithium precursor can be further improved.

[0088] In particular, when the second active material powder is added as a feedstock for the reduction process described below, the recovery efficiency of the lithium precursor may be reduced due to impurities and the dispersion of the second active material powder. However, the second active material powder can be used as a feedstock for wet metal extraction processes (e.g., acid solution treatment), thereby further improving the recovery efficiency of the lithium precursor.

[0089] For example, acid solution treatment can be a leaching process using an acidic extractant. For instance, in acid solution treatment, lithium precursors can be extracted by mixing a second active material powder with an acidic extractant diluted with a diluent, and then adjusting the pH to achieve equilibrium. The second active material powder after lithium precursor extraction can then be mixed with sulfuric acid as a removal agent to extract transition metals.

[0090] For example, the acidic extractant may include at least one selected from a mixture of di-2-ethylhexylphosphonic acid, 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, di-2-ethylhexylphosphonic acid and tributyl phosphate, and a mixture of 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester and tributyl phosphate.

[0091] For example, diluents may include non-aromatic hydrocarbons.

[0092] For example, the equilibrium pH can be in the range of approximately 5.5 to 6.5. Within this equilibrium pH range, lithium extraction rate can be effectively improved.

[0093] In some exemplary embodiments, the separation of dust particles 60 and the classification of the first active material powder and the second active material powder can be performed simultaneously in the classifier 100. Therefore, the lithium precursor recovery process can be simplified, and process efficiency can be further improved.

[0094] In an exemplary embodiment, a primary precursor mixture can be prepared from the active material powder 70 (e.g., in step S30). In an exemplary embodiment, the first active material powder can be subjected to hydrogen reduction treatment to form the primary precursor mixture.

[0095] In some implementations, a fluidized bed reactor can be used for hydrogen reduction treatment. For example, active material powder can be introduced into the fluidized bed reactor and hydrogen can be injected from the bottom of the reactor.

[0096] For example, if a first active material powder is used, the proportion of the first lithium composite oxide particles can be increased by 80%, making fluidization easier to achieve. Therefore, the efficiency of the hydrogen reduction process and the recovery efficiency of the lithium precursor can be further improved.

[0097] A cyclone of hydrogen can be formed from the bottom of the fluidized bed reactor, and a primary precursor mixture can be generated simultaneously with the contact of the active material powder 70. In this case, the active material powder 70 may be free of dust particles 60 or may contain trace amounts of dust particles 60, thereby preventing undesirable side reactions other than hydrogen reduction. Therefore, the yield of lithium precursors can be further improved.

[0098] In some embodiments, the carrier gas can be mixed with and injected together with hydrogen from the bottom of the fluidized bed reactor. This promotes gas-solid mixing in the fluidized bed to facilitate the reaction, and allows for the easy formation of a reaction layer of the primary precursor mixture within the fluidized bed reactor. The carrier gas can include, for example, an inert gas, such as nitrogen (N2) or argon (Ar).

[0099] The primary precursor mixture may include the hydrogen reduction product of the lithium-transition metal oxide contained in the active material powder 70. If an NCM-based lithium oxide is used as the lithium-transition metal oxide, the primary precursor mixture may include a primary lithium precursor and a transition metal-containing product.

[0100] Primary lithium precursors may include lithium hydroxide, lithium oxide, and / or lithium carbonate. In an exemplary embodiment, the primary lithium precursor can be obtained via a hydrogen reduction reaction, thereby reducing the mixed content of lithium carbonate.

[0101] Products containing transition metals can include Ni, Co, NiO, CoO, MnO, etc.

[0102] The hydrogen reduction reaction can be carried out at a temperature of about 400°C to 700°C, preferably 450°C to 550°C.

[0103] In an exemplary embodiment, after collecting the primary precursor mixture, it can be washed with water (e.g., in step S40).

[0104] Primary lithium precursors can be converted into lithium precursors consisting primarily of lithium hydroxide through a washing process. For example, lithium oxide and lithium carbonate mixed in the primary lithium precursor can be converted into lithium hydroxide by reacting with water, or they can be washed and removed. Thus, high-purity lithium precursors converted into the desired form of lithium hydroxide can be produced.

[0105] The primary lithium precursor can react with water to dissolve it, thus essentially preparing an aqueous solution of lithium hydroxide.

[0106] Transition metal-containing products contained in the primary precursor mixture can be precipitated and dissolved or reacted in water without washing. Therefore, transition metal-containing products can be separated by filtration, and lithium precursors including high-purity lithium hydroxide can be obtained.

[0107] In some implementations, the water washing process can be carried out under conditions where carbon dioxide (CO2) is removed. For example, the washing process can be carried out in a CO2-free atmosphere (e.g., an air atmosphere from which CO2 has been removed), thereby preventing the regeneration of lithium carbonate.

[0108] In one embodiment, the water provided during the washing process can be purified using a CO2-deficient gas (e.g., nitrogen purification) to produce a CO2-free atmosphere.

[0109] In some embodiments, the precipitated and separated transition metal-containing products can be treated with an acid solution to form precursors in the form of acid salts of each transition metal. In one embodiment, sulfuric acid can be used as the acid solution. In this case, NiSO4, MnSO4, and CoSO4 can be recovered as transition metal precursors.

[0110] As described above, a lithium precursor consisting primarily of lithium hydroxide can be obtained by washing the primary precursor mixture produced by hydrogen reduction with water. Therefore, a positive electrode active material with higher capacity and longer lifespan can be obtained, while preventing byproducts from other types of lithium precursors such as lithium carbonate.

[0111] Lithium precursors can include lithium hydroxide (LiOH), lithium oxide (Li₂O), or lithium carbonate (Li₂CO₃). Considering the charge / discharge characteristics, lifetime characteristics, and high-temperature stability of lithium-ion secondary batteries, lithium hydroxide may be advantageous as a lithium precursor. For example, lithium carbonate may cause deposition reactions on the separator layer, thereby reducing lifetime stability.

[0112] Therefore, according to an embodiment of the present invention, a method for using highly selectively regenerated lithium hydroxide as a lithium precursor can be provided.

[0113] [Explanation of reference numerals in the attached figures]

[0114] 100: Grading machine; 110: Grading body

[0115] 115: Grading screen; 120: Upper outlet.

[0116] 130: Lower outlet; 140: Active substance outlet

[0117] 150: Active substance inlet; 160: Fluid inlet

[0118] 60: Dust particles; 70: Active substance powder

[0119] 80: First lithium composite oxide particles

[0120] 90: Second lithium composite oxide particles

Claims

1. A classifier for positive electrode active materials, comprising: An active material inlet is provided through which a mixture of positive electrode active material, comprising active material powder containing lithium composite oxide particles and dust particles, is injected. A grading body includes a grading sieve for grading the active substance powder into a first active substance powder and a second active substance powder based on the average particle size. The upper outlet, located at the top of the grading body, allows dust particles to be dispersed and discharged from the positive electrode active material mixture; An active substance outlet, connected to the central portion of the grading body, discharges the first active substance powder; and The lower outlet is connected to the lower part of the grading body to discharge the second active material powder of the positive electrode active material mixture. The average particle size of the second active substance powder is smaller than that of the first active substance powder. The lithium composite oxide particles include first lithium composite oxide particles and second lithium composite oxide particles with different average particle sizes, wherein the average particle size of the first lithium composite oxide particles is larger than that of the second lithium composite oxide particles; the first lithium composite oxide particles have a particle size value that allows them to be easily fluidized in a fluidized bed reactor, and the second lithium composite oxide particles comprise fine particles that are dispersed rather than fluidized in the fluidized bed reactor. The grading sieve is a porous plate with holes. The ratio of the pore size to the average particle size D50 of the second active substance powder is in the range of 1.5 to 5.

2. The classifier for positive electrode active materials according to claim 1, further comprising a fluid inlet located at the lower part of the classifier body, such that fluid is injected through the fluid inlet.

3. The classifier for positive electrode active materials according to claim 1, wherein, The dust particles include particles derived from carbon-based conductive materials and adhesives.

4. The classifier for positive electrode active materials according to claim 1, wherein, The grading screen vibrates in three dimensions through the eccentric rotation of a rotating weight located at the bottom of the grading screen.

5. The classifier for positive electrode active materials according to claim 1, wherein, The separation efficiency of each particle size of the grading sieve is 60% to 90%.

6. The classifier for positive electrode active materials according to claim 1, wherein, The grading sieve has a multi-level structure in which multiple sieves are stacked.

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