Method for recovering cleaning liquid, recovery device thereof, and cleaning liquid recovered thereby

Abstract

To provide a method and an apparatus for recovering a cleaning solution that contains lithium at a high concentration and has high quality.SOLUTION: The present invention relates to a method for recovering cleaning liquid, a recovery device thereof, and a cleaning liquid recovered thereby, and more specifically, the method includes synthesizing positive electrode active material particles including a lithium composite oxide containing nickel, introducing a first cleaning liquid into the positive electrode active material particles and mixing the first cleaning liquid, the first cleaning liquid including a coating raw material, a precipitant, and a solvent, filtering the mixture to separate a liquid mixture, and recovering the separated liquid mixture, and the lithium concentration in the recovered cleaning liquid is 3500 ppm or more.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a method for recovering a cleaning liquid, a recovery device therefor, and the cleaning liquid recovered thereby. [Background technology]

[0002] Lithium secondary batteries are used as energy storage and supply sources in a variety of fields. They are widely used as energy storage and supply sources not only in portable devices such as mobile phones, tablet PCs, wearable devices, laptops, digital cameras, and power tools, but also in transportation such as hybrid cars, electric cars, and electric scooters. Recently, their applications have expanded to future industrial fields such as drones, robots, and urban air mobility (UAM).

[0003] In particular, the electric vehicle market has grown significantly due to recent concerns about climate change and growing interest in environmentally friendly products, resulting in a rapid increase in the use of lithium secondary batteries. However, because the main raw materials needed to manufacture lithium secondary batteries must be obtained from natural resources, the process of extracting the raw materials inevitably causes environmental destruction and pollution. Therefore, there is an urgent need to develop technology to recycle the raw materials.

[0004] As a result, methods for recovering valuable metals, such as transition metal precursors and lithium precursors, from waste materials related to lithium secondary batteries, such as discarded lithium secondary batteries, waste materials generated in the manufacturing process of lithium secondary batteries, and wastewater generated in the washing process of positive electrode active materials, are attracting attention. The recovered valuable metals can be recycled for the manufacture of lithium secondary batteries, and active research and development is being conducted on recycling methods that are more environmentally friendly and less costly and can recover valuable metals in high concentrations.

[0005] Various methods have been implemented to recover valuable metals from discarded lithium secondary batteries or waste generated during the manufacturing process of lithium secondary batteries. However, conventional methods have a problem in that a large amount of basic solution must be used during the recovery process. Because by-products generated from the basic solution cause environmental pollution, an alternative that can replace the basic solution is needed.

[0006] Various methods have been implemented to recover lithium precursors from wastewater generated during the washing process of a positive electrode active material. The wastewater generated during the washing process of a positive electrode active material contains a large amount of lithium. However, conventional methods have the drawback of requiring a separate process to recover the lithium precursor from the wastewater. Furthermore, since there is no process with a 100% recovery rate, the creation of a separate process itself inevitably results in lithium loss. Therefore, an improved method for recovering lithium precursors is needed. Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a method and an apparatus for recovering a cleaning solution that contains lithium at a high concentration and has high quality. [Means for solving the problem]

[0008] A method for recovering a cleaning solution according to one embodiment of the present invention includes: synthesizing positive electrode active material particles including a lithium composite oxide containing nickel; introducing and mixing a first cleaning solution with the positive electrode active material particles, the first cleaning solution including a coating raw material, a precipitant, and a solvent; filtering the mixture to separate a liquid mixture; and recovering the separated liquid mixture, wherein a lithium concentration in the recovered cleaning solution may be 3500 ppm or more.

[0009] The cleaning liquid recovery device according to one embodiment of the present invention includes a tank unit, a valve unit, a line unit, and a pump unit, and can recover the cleaning liquid by the above-described recovery method.

[0010] The cleaning liquid according to one embodiment of the present invention can be recovered by the above-described method for recovering a cleaning liquid. [Effects of the Invention]

[0011] By using the cleaning solution recovery method and recovery device according to an embodiment of the present invention, it is possible to recover a cleaning solution containing a high concentration of lithium, and also to recover a cleaning solution containing no or only trace amounts of impurities, thereby enabling the recovery of a cleaning solution with high quality. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a conceptual diagram illustrating a lithium secondary battery according to an embodiment of the present invention; [Figure 2] 1 is a schematic diagram illustrating a lithium secondary battery according to one embodiment, showing a cylindrical battery configuration. [Figure 3] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, illustrating a prismatic battery configuration. [Figure 4] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, illustrating a pouch-type battery configuration. [Figure 5] 1 is a schematic diagram showing a lithium secondary battery according to an embodiment, illustrating a pouch-type battery configuration. [Figure 6] FIG. 2 is an enlarged view of a positive electrode active material according to one embodiment of the present invention. [Figure 7] 1 is a flowchart illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention. [Figure 8] 1 is a schematic diagram illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention. [Figure 9] 1 is a schematic diagram illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention. [Figure 10]1 is a schematic diagram illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention. [Figure 11] 4 is a flowchart illustrating a method for recovering a cleaning liquid according to an embodiment of the present invention. [Figure 12] 10 is a flowchart illustrating a method for recovering a cleaning liquid according to a comparative example of the present invention. [Figure 13] 1 is a schematic diagram illustrating a cleaning liquid recovery device according to an embodiment of the present invention. [Figure 14] 1 is a flow chart illustrating a method for extracting a lithium precursor from a cleaning solution according to an embodiment of the present invention. [Figure 15] 1 is a flowchart illustrating a method for producing a first solution in the above-described method for extracting a lithium precursor. DETAILED DESCRIPTION OF THE INVENTION

[0013] In order to fully understand the configuration and effects of the present invention, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, and may be realized in various forms and may undergo various modifications. The description of the present embodiments is provided solely to ensure complete disclosure of the present invention and to fully convey the scope of the invention to those skilled in the art.

[0014] In this specification, when a component is referred to as being on top of another component, it means that it may be formed directly on the other component, or that a third component may be interposed between them. Also, in the drawings, the thickness of the components is exaggerated for the purpose of effectively explaining the technical content. Throughout the specification, parts designated with the same reference numerals refer to the same components.

[0015] Unless otherwise stated herein, the singular can also include the plural. Additionally, unless otherwise stated, "A" or "B" can mean "including A, including B, or including A and B." As used herein, "comprises" and / or "comprising" do not exclude the presence or addition of one or more other elements to the referenced element.

[0016] As used herein, "combinations thereof" can mean mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0017] Unless otherwise defined herein, particle size refers to the average particle size. Furthermore, particle size refers to the average particle size (D50), which refers to the diameter of particles with a cumulative volume of 50% by volume in a particle size distribution. The average particle size (D50) can be measured using methods well known to those skilled in the art, such as a particle size analyzer or a transmission electron microscope (TEM) or scanning electron microscope (SEM) image. Alternatively, measurement can be performed using a measuring device that uses dynamic light scattering, and data analysis can be performed to count the number of particles in each particle size range, followed by calculation to obtain the average particle size (D50) value. Alternatively, measurement can be performed using a laser diffraction method. When measuring by the laser diffraction method, more specifically, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size measuring device (e.g., MT 3000 manufactured by Microtrac), and ultrasonic waves of approximately 28 kHz are irradiated at an output of 60 W, after which the average particle size (D50) based on 50% of the particle size distribution in the measuring device can be calculated.

[0018] The "atomic fraction" used in the present invention is obtained by analyzing the elements on the surface of the positive electrode active material CAM using an energy dispersive spectroscopy (EDX), i.e., SEM-EDS. The electron beam and atoms on the surface of the positive electrode active material CAM can emit characteristic X-rays. The emitted X-rays can be analyzed using an EDX detector to determine the type and content of the corresponding element. The content obtained here can correspond to the "atomic fraction."

[0019] 1 is a conceptual diagram illustrating a lithium secondary battery according to an embodiment of the present invention. Referring to FIG. 1, the lithium secondary battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte solution ELL.

[0020] The positive electrode 10 and the negative electrode 20 may be separated from each other by a separator 30. The separator 30 may be disposed between the positive electrode 10 and the negative electrode 20. The positive electrode 10, the negative electrode 20, and the separator 30 may be in contact with the electrolyte solution ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in the electrolyte solution ELL.

[0021] The electrolyte ELL can be a medium for transferring lithium ions between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions can pass through the separator 30 and move toward the positive electrode 10 or the negative electrode 20.

[0022] positive electrode 10 The lithium secondary battery positive electrode 10 may include a current collector COL1 and a positive electrode active material layer AML1 formed on the current collector COL1. The positive electrode active material layer AML1 includes a positive electrode active material and may further include a binder and / or a conductive material.

[0023] As an example, the positive electrode 10 may further include an additive that may act as a sacrificial positive electrode.

[0024] The content of the positive electrode active material in the positive electrode active material layer AML1 may be 90 wt % to 99.5 wt % relative to 100 wt % of the positive electrode active material layer AML1, and the contents of the binder and conductive material may be 0.5 wt % to 5 wt % respectively relative to 100 wt % of the positive electrode active material layer AML1.

[0025] The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector COL1. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, nylon, etc.

[0026] The conductive material is used to impart conductivity to the electrode and may be any material that is electronically conductive and does not cause a chemical change in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber containing copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0027] The current collector COL1 may be made of Al, but is not limited to this.

[0028] The positive electrode active material will be described in detail later with reference to FIG.

[0029] negative electrode 20 The lithium secondary battery positive electrode 20 may include a current collector COL2 and a negative electrode active material layer AML2 formed on the current collector COL2. The negative electrode active material layer AML2 includes a negative electrode active material and may further include a binder and / or a conductive material.

[0030] For example, the negative electrode active material layer AML2 may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0% to 5% by weight of the conductive material.

[0031] The binder serves to firmly adhere the negative active material particles to each other and to firmly adhere the negative active material to the current collector COL 2. The binder may be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0032] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, and combinations thereof.

[0033] The aqueous binder may be selected from styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyether resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0034] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulose-based compound to impart viscosity. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal may be sodium, potassium, or lithium.

[0035] The dry binder is a fiberizable polymeric material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, ethylene oxide, or a combination thereof.

[0036] The conductive material is used to impart conductivity to the electrode and may be any material that is electronically conductive and does not cause a chemical change in the battery. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0037] The current collector COL2 may be selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0038] negative electrode active material The negative electrode active material in the negative electrode active material layer AML2 includes a material capable of reversibly inserting / desorbing lithium ions, lithium metal, a lithium metal alloy, a material capable of doping or dedoping lithium, or a transition metal oxide.

[0039] As the substance capable of reversibly inserting / desorbing the lithium ions, a carbon-based negative electrode active material may be used, for example, including crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0040] As the alloy of the lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0041] As the substance capable of doping or undoping the lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x < 2), an Si-Q alloy (where Q is selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, an Sn-based alloy, or a combination thereof.

[0042] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to one embodiment, the silicon-carbon composite may be in a form in which silicon particles are coated with amorphous carbon on the surface of the silicon particles. For example, it may include secondary particles (cores) formed by combining primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of the secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0043] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core including crystalline carbon and silicon particles, and an amorphous carbon coating layer disposed on the surface of the core.

[0044] The Si-based or Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0045] Separator 30 Depending on the type of lithium secondary battery, a separator 30 may be present between the positive electrode 10 and the negative electrode 20. Such separator 30 may be made of polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, but it goes without saying that mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0046] Separator 30 may include a porous substrate and a coating layer comprising an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0047] The porous substrate may be a polymer membrane made of any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these polymers.

[0048] The organic material may include a polyvinylidene fluoride polymer or a (meth)acrylic polymer.

[0049] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof.

[0050] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a coating layer containing an organic material and a coating layer containing an inorganic material.

[0051] Electrolyte ELL The electrolyte ELL for lithium secondary batteries contains a non-aqueous organic solvent and a lithium salt.

[0052] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0053] The non-aqueous organic solvent can be a carbonate, ester, ether, ketone, or alcohol solvent, an aprotic solvent, or a combination thereof.

[0054] Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).

[0055] Examples of ester solvents that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone.

[0056] Examples of ether solvents that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that can be used include cyclohexanone. Examples of alcohol solvents that can be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that can be used include nitriles such as R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane and 1,4-dioxolane, and sulfolanes.

[0057] The non-aqueous organic solvents may be used alone or in combination of two or more.

[0058] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate may be mixed together, and the cyclic carbonate and the chain cyclic carbonate may be mixed in a volume ratio of 1:1 to 1:9.

[0059] The lithium salt is dissolved in an organic solvent and acts as a lithium ion source in the battery, enabling basic lithium secondary battery operation and promoting the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (x and y are positive numbers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalato)phosphate (LiDFOB), and lithium bis(oxalato)borate (LiBOB).

[0060] Lithium secondary battery Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 2 to 5 are schematic diagrams illustrating a lithium secondary battery according to an embodiment, with FIG. 2 illustrating a cylindrical battery, FIG. 3 illustrating a prismatic battery, and FIGS. 4 and 5 illustrating pouch battery types. Referring to FIGS. 2 to 4, a lithium secondary battery 100 may include an electrode assembly 40 having a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a housing 50 in which the electrode assembly 40 is embedded. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the housing 50, as shown in FIG. 2. Also, in FIG. 3, the lithium secondary battery 100 may include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 4 and 5, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the positive electrode assembly 40 to the outside.

[0061] The lithium secondary battery according to an embodiment of the present invention may be applied to automobiles, mobile phones, and / or various types of electrical devices, but the present invention is not limited thereto.

[0062] positive electrode active material 6 is a diagram illustrating a positive electrode active material according to an embodiment of the present invention. Referring to FIG. 6, the positive electrode active material CAM is in a powder form before being used in the positive electrode active material layer AML1 described above with reference to FIG.

[0063] Referring to FIG. 6, according to one embodiment of the present invention, the positive electrode active material CAM may include a plurality of first particles PTC1, a plurality of second particles PTC2, and a plurality of aggregates ZAG.

[0064] The first particles PTC1 may have a first average particle size APD1, and the second particles PTC2 may have a second average particle size APD2. The second average particle size APD2 may be smaller than the first average particle size APD1. For example, the first average particle size APD1 may be 5 μm to 25 μm. For example, the first average particle size APD1 may be 7 μm to 25 μm, 10 μm to 25 μm, 15 μm to 25 μm, or 10 μm to 20 μm. The second average particle size APD2 may be 0.1 μm to 10 μm. For example, the second average particle size APD2 may be 0.1 μm to 7 μm, 0.5 μm to 6 μm, or 1 μm to 5 μm. The "average particle size," i.e., D50, used in the present invention may be determined by randomly selecting about 30 secondary particle-form active material particles from an electron microscope photograph of the positive electrode active material, measuring their particle sizes, and determining the diameter (D50) of the particles with a cumulative volume of 50% from the particle size distribution. In the present invention, the first particles PTC1 may be referred to as large particles, and the second particles PTC2 may be referred to as small particles.

[0065] The first and second particles PTC1 and PTC2 may have a granular or spherical shape. In one embodiment of the present invention, the first particle PTC1 may have the form of a secondary particle formed by agglomeration of primary particles. In one embodiment of the present invention, the second particle PTC2 may have a single particle form. The single particle form may include the form of a primary particle or the form of a secondary particle formed by agglomeration of several primary particles. The single particle form may include one crystal grain or several crystal grains. The crystal grain may be the smallest unit of the lithium composite oxide having one crystal direction. For example, the second particle PTC2 may include one primary particle and / or one single particle formed by merging multiple primary particles together.

[0066] The cathode active material CAM according to an embodiment of the present invention may have a bimodal structure including large particles (e.g., PTC1) and small particles (e.g., PTC2) with different average particle sizes. The small particles fill the gaps between the large particles, thereby improving the packing density of the cathode active material CAM. In other words, the cathode active material CAM according to an embodiment of the present invention may have a relatively high energy density per unit volume.

[0067] In one embodiment, the first particles PTC1 and the second particles PTC2 in the positive electrode active material CAM may have a weight ratio of 95:5 to 50:50. In another embodiment, the first particles PTC1 and the second particles PTC2 in the positive electrode active material CAM may have a weight ratio of 5:95 to 50:50. For example, the weight of the first particles PTC1 may be greater than the weight of the second particles PTC2 in the positive electrode active material CAM.

[0068] The first particles PTC1 may include a first lithium composite oxide, and the second particles PTC2 may include a second lithium composite oxide. Each of the first and second lithium composite oxides may include nickel (Ni). As an example, each of the first and second lithium composite oxides may further include at least one metal selected from the group consisting of cobalt (Co), manganese (Mn), and aluminum (Al).

[0069] For example, the first lithium composite oxide may be represented by the following Chemical Formula 1. [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0070] In the formula 1, 0.9≦a1≦1.8, 0.8≦x1≦1, 0≦y1≦0.2, 0≦z1≦0.2, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1; M 1 and M 2are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0071] In Chemical Formula 1, 0.85≦x1≦1, 0≦y1≦0.15, and 0≦z1≦0.15, or 0.9≦x1≦1, 0≦y1≦0.1, and 0≦z1≦0.1.

[0072] The second lithium composite oxide may be represented by the following Chemical Formula 2. [Chemical formula 2] Li a2 Ni x2 M 3 y2 M 4 z2 O 2-b2 X b2

[0073] In the above Chemical Formula 2, 0.9≦a2≦1.8, 0.8≦x2≦1, 0≦y2≦0.2, 0≦z2≦0.2, 0.9≦x2+y2+z2≦1.1, and 0≦b2≦0.1; M 3 and M 4 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0074] In Chemical Formula 2, 0.85≦x2≦1, 0≦y2≦0.15, and 0≦z2≦0.15, or 0.9≦x2≦1, 0≦y2≦0.1, and 0≦z2≦0.1.

[0075] First, lithium composite oxide M 1 and M 2 The ratio of the elements constituting it is M of the second lithium composite oxide. 3 and M 4and the ratio of the elements constituting it may be different. For example, the M 1 and M 2 may contain Co and Al, and M of the second lithium composite oxide 3 and M 4 may include Co and Mn. 1 and M 2 , and M 3 and M 4 Each may contain Co, Al, and Mn.

[0076] In one embodiment of the present invention, x1, the molar ratio of Ni in Chemical Formula 1, may be greater than 0.8. For example, x1 may be 0.88 or greater. If the first lithium composite oxide has a high nickel content (x1>0.8), the calcination of the first lithium composite oxide may be performed at a relatively low temperature. As a result, the first particles PTC1 may be synthesized at a relatively low temperature in the process for preparing a positive electrode active material for a lithium secondary battery, which will be described later. Ni in the first lithium composite oxide may affect the output and capacity of a lithium secondary battery. The present invention can provide a high-power lithium secondary battery by using a first lithium composite oxide having a high nickel content. In Chemical Formula 2, x2, the molar ratio of Ni, may also be greater than 0.8. For example, x2 may be 0.88 or greater. However, x2 may be different from x1.

[0077] As the Ni content in the first and second lithium composite oxides increases, the stability of the positive electrode or secondary battery may decrease. In one embodiment of the present invention, the first and second lithium composite oxides may further contain Co, which may effectively prevent structural collapse due to repeated charge and discharge, improve room temperature and high temperature life characteristics, and improve the stability and capacity retention characteristics of the secondary battery.

[0078] In one embodiment of the present invention, the first particles PTC1 may include a first coating layer CTL1 provided on their surfaces. The second particles PTC2 may include a second coating layer CTL2 provided on their surfaces. The first coating layer CTL1 and the second coating layer CTL2 may each include cobalt (Co). The first coating layer CTL1 and the second coating layer CTL2 may each be derived from a coating agent described below. Due to the first coating layer CTL1, Co can be detected in the first particles PTC1 as a result of SEM-EDS analysis. Due to the second coating layer CTL2, Co can be detected in the second particles PTC2 as a result of SEM-EDS analysis.

[0079] For example, each of the first coating layer CTL1 and the second coating layer CTL2 may contain a cobalt (Co)-containing compound. The cobalt-containing compound may be, for example, cobalt oxide, cobalt hydroxide, cobalt carbonate, a composite thereof, or a mixture thereof. The cobalt-containing compound may further contain other metals or nonmetallic elements in addition to cobalt. For example, the cobalt-containing compound may further contain lithium, manganese, and / or nickel. For example, the cobalt-containing compound may be lithium cobalt oxide.

[0080] In the first coating layer CTL1, the cobalt content relative to the total amount of nickel and cobalt may be 55 at% to 70 at%, for example, 55 at% to 68 at%, 55 at% to 65 at%, 55 at% to 63 at%, 57 at% to 70 at%, 59 at% to 70 at%, 60 at% to 70 at%, 60 at% to 65 at%1, or 61 at% to 63 at%. When the cobalt coating content of the first particles PTC1 satisfies this range, uneven coating between particles is eliminated, a uniform coating is formed on the surfaces of the first particles PCT1, gas generation is suppressed, and initial charge / discharge efficiency and long-term life characteristics may be improved.

[0081] In the second coating layer CTL2, the cobalt content relative to the total amount of nickel and cobalt may be 39 at% to 45 at%, for example, 39 at% to 44 at%, 39 at% to 43 at%, 39 at% to 42 at%, 40 at% to 45 at%, or 41 at% to 45 at%. When the cobalt coating content of the second particles PTC2 satisfies this range, uneven coating between particles is eliminated, excessive coating on the second particles PCT2 is suppressed, and a uniform coating is induced, reducing resistance and improving initial charge / discharge efficiency and long-term life characteristics.

[0082] The first coating layer CTL1 may be a layer that uniformly or non-uniformly covers the surface of the first particles PCT1. If the first coating layer CTL1 non-uniformly covers the surface of the first particles PCT1, the first coating layer CTL1 may have an island shape. However, the first coating layer CTL1 may not be visible in an image taken with an electron microscope. The first coating layer CTL1 may be confirmed by the presence of cobalt (Co) in the first particles PCT1 using SEM-EDS. The second coating layer CTL2 may also be substantially the same as that described for the first coating layer CTL1.

[0083] The morphology, structure, and composition of particles constituting the positive electrode active material CAM can be confirmed by time-of-flight secondary ion mass spectrometry (TOF-SIMS) on the positive electrode active material CAM according to an embodiment of the present invention.

[0084] A TOF-SIMS device is a SIMS device equipped with a TOF, which is a mass spectrometer. Specifically, a SIMS device analyzes ions (positive or negative ions) released when primary ions collide with the surface of an analyte, thereby obtaining the chemical components and surface structure of the material. TOF-SIMS analysis may not detect Co within the first and second particles PCT1 and PCT2 of the present invention. In other words, it can be indirectly confirmed that Co exists in the form of coating layers CTL1 and CTL2 on the surface of the particles PCT1 and PCT2 of the present invention.

[0085] As described above, the first particles PCT1 may have a secondary particle shape. In this case, microcracks may form inside the secondary particles during charge and discharge of the battery, accelerating side reactions between the electrolyte (see 300 in FIG. 1 ) and the positive electrode active material CAM, which may result in gas generation inside the battery. This may reduce the stability and lifespan of the secondary battery.

[0086] According to an embodiment of the present invention, the second particles PTC2 may have a single particle form. The second particles PCT2 may be more durable and denser than the first particles PCT1. Therefore, the formation of microcracks within the second particles PTC2 may be prevented. As a result, the stability and capacity retention characteristics of the secondary battery according to the present invention may be improved.

[0087] The ZAG aggregates may be provided in the spaces between the first and second particles PTC1 and PTC2. The ZAG aggregates may be derived from the coating agent described below. The ZAG aggregates may include zirconium (Zr). More specifically, the ZAG aggregates may include zirconia. For example, the ZAG aggregates may be clumps formed by agglomeration of portions of the coating agent that are not coated on the surfaces of the first and second particles PTC1 and PTC2.

[0088] In another embodiment of the present invention, the positive electrode active material CAM may include a plurality of first particles PCT1. For example, the positive electrode active material CAM may include a plurality of aggregates ZAG in addition to the plurality of first particles PTC1.

[0089] In another embodiment of the present invention, the positive electrode active material CAM may include a plurality of second particles PCT2. For example, the positive electrode active material CAM may include a plurality of aggregates ZAG in addition to the plurality of second particles PCT2.

[0090] Method for producing positive electrode active material 7 is a flow chart illustrating a method for manufacturing a positive electrode active material according to an embodiment of the present invention, and FIGS. 8 to 10 are schematic diagrams illustrating a method for manufacturing the positive electrode active material of FIG.

[0091] 7 and 8, first particles PTC1 may be synthesized (S110). A method for synthesizing the first particles PTC1 will be described in detail. First, a first precursor PRE1 may be prepared. The first precursor PRE1 may contain Ni and M of the above-mentioned Chemical Formula 1. 1 And, M 2 M 1 and M 2 may each independently be at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr.

[0092] In one embodiment, the first precursor PRE1 can be obtained by a co-precipitation method. For example, the co-precipitation method can include dissolving a transition metal source material in a solvent such as distilled water, and then sequentially introducing the transition metal salt solution into a reactor together with a chelating agent and a basic aqueous solution to cause precipitation. The precipitate is collected in a slurry form, and the slurry solution is filtered and dried to obtain the first precursor PRE1, which is a metal composite oxide.

[0093] In the present invention, the transition metal source material may include a metal salt of at least one element selected from the group consisting of Ni, Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr. The metal salt may be a sulfate, nitrate, acetate, halide, hydroxide, or the like, but is not particularly limited as long as it is soluble in a solvent. The transition metal source material according to this embodiment may include a nickel salt, a cobalt salt, and an aluminum salt. The transition metal source materials may be mixed in an adjusted molar ratio so that the positive electrode active material has high capacity characteristics. For example, x1 in Chemical Formula 1 may be determined based on the molar ratio.

[0094] The first precursor PRE1 may be mixed with a lithium source material at a certain ratio to form a mixture. For example, the first precursor PRE1 may be mixed with the lithium source material at a molar ratio of about 1:1. The lithium source material may be any material commonly used in preparing a positive electrode active material. For example, the lithium source material may include a lithium salt such as lithium carbonate, lithium nitrate, lithium hydroxide, or lithium sulfate.

[0095] The mixture may be placed in a furnace (FRC) and subjected to a first firing process STR1 at a first temperature. The first temperature may be 700°C to 1,000°C. More specifically, the first temperature may be 900°C to 1,000°C. The first firing process STR1 may be performed in an oxidizing atmosphere such as air or oxygen. The heat treatment time for the first firing process STR1 may be 10 hours to 30 hours. In another embodiment of the present invention, a pre-firing process at 150°C to 800°C may be additionally performed before the first firing process STR1.

[0096] First particles PTC1 may be formed from a mixture containing a first precursor PRE1 and a lithium source through a first firing process STR1. The synthesized first particles PTC1 may be subjected to a pulverization process (S120). The pulverized first particles PTC1 may have the first average particle size APD1 described with reference to FIG.

[0097] 7 and 9, second particles PTC2 may be synthesized (S210). A method for synthesizing second particles PTC2 will be described in detail. First, a second precursor PRE2 may be prepared. The second precursor PRE2 may be a mixture of Ni and M represented by the above-mentioned Chemical Formula 2. 3 And, M 4 M 3 and M 4 may each independently contain at least one element selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr.

[0098] In one embodiment, the second precursor PRE2 can be obtained by substantially the same or similar method as the first precursor PRE1, except that the average particle size of the second precursor PRE2 can be smaller than the average particle size of the first precursor PRE1.

[0099] A second precursor PRE2 may be mixed with a lithium source material in a certain ratio to form a mixture. The mixture may be placed in a furnace FRC, and a second firing process STR2 may be performed at a second temperature. The second temperature may be 700°C to 1,000°C. More specifically, the second temperature may be 700°C to 800°C. For example, the second temperature may be lower than the first temperature. Other details regarding the second firing process STR2 may be the same as or similar to those for the first firing process STR1.

[0100] The second particles PTC2 may be formed from the mixture containing the second precursor PRE2 and the lithium source by the second firing process STR2. The synthesized second particles PTC2 may be subjected to a pulverization process (S220). The pulverized second particles PTC2 may have the second average particle size APD2 described in FIG. 6.

[0101] Referring to FIG. 7, first particles PTC1 and second particles PTC2 may be combined (S310). In one embodiment, the first particles PTC1 and the second particles PTC2 may be mixed at a weight ratio of 95:5 to 50:50. In another embodiment, the first particles PTC1 and the second particles PTC2 may be mixed at a weight ratio of 5:95 to 50:50. By mixing first particles PTC1 and second particles PTC2 having different average particle sizes, a bimodal cathode active material may be prepared. The first and second particles PTC1 and PTC2 may be washed and dried.

[0102] For example, the step S310 of mixing the first particles PTC1 and the second particles PTC2 may be omitted. That is, the first particles PTC1 and the second particles PTC2 may be independently subjected to the coating process described below. This may result in the manufacture of a cathode active material CAM including a plurality of first particles PTC1, or a cathode active material CAM including a plurality of second particles PTC2.

[0103] 7 and 10, a coating process may be performed on the first and second particles PTC1 and PTC2 (S400). The coating process may include coating the surfaces of the first and second particles PTC1 and PTC2 with cobalt (Co). Specifically, the first and second particles PTC1 and PTC2 may be mixed with a first cleaning solution WF1. The first cleaning solution WF1 may include a coating source material, a precipitant (or pH adjuster), a solvent, etc. The coating source material may be a cobalt compound. For example, the cobalt compound may include, but is not limited to, cobalt sulfate. The precipitant (or pH adjuster) may include sodium hydroxide (NaOH), etc. The solvent may include distilled water, an alkaline solution, etc.

[0104] The first and second particles PTC1 and PTC2 and the coating raw material may be uniformly mixed using the agitator MXU. Next, the first and second particles PTC1 and PTC2 may be filtered and dried, and then a surface treatment may be performed on the first and second particles PTC1 and PTC2. The surface treatment may be performed by placing the mixture in a furnace FRC and performing a third firing process at a third temperature. For example, the third temperature may be 500°C to 800°C. More specifically, the third temperature may be 700°C to 800°C. The third firing process may be performed in an oxidizing atmosphere such as air or oxygen. The heat treatment time for the third firing process may be 10 hours to 30 hours. This may produce the cathode active material CAM according to the embodiment of the present invention described with reference to FIG. 6.

[0105] Cleaning solution and its recovery method Fig. 11 is a flowchart illustrating a cleaning liquid and a method for recovering the same according to an embodiment of the present invention, and Fig. 12 is a flowchart illustrating a cleaning liquid and a method for recovering the same according to a comparative example of the present invention.

[0106] 11, a cleaning solution according to an embodiment of the present invention may be recovered during the manufacturing process of a positive electrode active material including a lithium composite oxide having a high nickel content and a cobalt coating layer. The lithium composite oxide having a high nickel content may refer to, for example, a lithium composite oxide having a nickel content of 80 mol% or more, or 88 mol% or more, of the metals excluding lithium. In other words, it may refer to the above-mentioned lithium composite oxides in which x1 or x2 is 0.8 or more, or 0.88 or more.

[0107] For example, the method for manufacturing the positive electrode active material may include the method for manufacturing the positive electrode active material described above with reference to Fig. 7. For example, the method for manufacturing the positive electrode active material may include synthesizing particles including a lithium composite oxide having a high nickel content, adding and mixing the particles with a first cleaning solution, filtering the mixture, and heat-treating a solid mixture of the filtered mixture.

[0108] In one embodiment, synthesizing particles containing a lithium composite oxide having a high nickel content (S100) may include synthesizing the first particles PTC1 or the second particles PTC2 described above. For example, the particles may include lithium by-products remaining on the surface.

[0109] The particles may be mixed with a first cleaning solution WF1 (S410). The first cleaning solution WF1 may include the above-described coating raw material, a precipitant (or pH adjuster), and a solvent. The coating raw material may be a cobalt compound. For example, the cobalt compound may include, but is not limited to, cobalt sulfate. The precipitant (or pH adjuster) may include sodium hydroxide (NaOH), etc. The solvent may include distilled water, an alkaline solution, etc.

[0110] In this step, residual lithium by-products on the particle surface can be removed.

[0111] In addition, a coating layer may be formed on the surface of the particles in this step. Lithium by-products may also be generated in this coating step. The lithium by-products may be lithium by-products remaining on the surface of the particles and / or the coating layer. The lithium by-products may also be removed in this step.

[0112] This step may include adding additional water to remove any remaining lithium by-products.

[0113] In this step, the mixture produced may include a solid mixture and a liquid mixture, and the liquid mixture may additionally contain sodium hydroxide as well as distilled water, alkaline solution, etc.

[0114] The mixture may be filtered (S430). Before the particles are heat-treated, the liquid mixture may be removed through this step, and only the solid mixture may be separated. In this specification, the liquid mixture may be referred to as a second washing liquid.

[0115] The separated solid mixture may be heat-treated (S450). That is, this step may include the surface treatment described above. The surface treatment may involve placing the mixture in a furnace FRC and performing a third firing process at a third temperature. For example, the third temperature may be 500°C to 800°C. More specifically, the third temperature may be 700°C to 800°C. The third firing process may be performed in an oxidizing atmosphere such as air or oxygen. The heat treatment time for the third firing process may be 10 hours to 30 hours. As a result, the cathode active material CAM according to the embodiment of the present invention described with reference to FIG. 6 may be produced.

[0116] The cleaning solution according to the embodiment of the present invention may include the second cleaning solution discharged in the filtering step S430 of the mixture, or may be a recovered second cleaning solution.

[0117] The cleaning solution according to the embodiment of the present invention may contain a high concentration of lithium (Li). For example, the concentration of lithium (Li) in the cleaning solution may be 3500 ppm or more. For example, the concentration of lithium (Li) in the cleaning solution may be 3500 ppm to 10000 ppm, or 3500 ppm to 5000 ppm.

[0118] The cleaning solution according to the embodiment of the present invention may be free of impurities. Alternatively, the cleaning solution according to the embodiment of the present invention may contain trace amounts of impurities. For example, the impurities may include sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), chlorine (Cl), sulfate (SO4), etc. For example, the concentration of the impurities in the cleaning solution may be 30,000 ppm or less. For example, the concentration of the impurities in the cleaning solution may be 20 ppm to 30,000 ppm. For example, the concentration of sulfate (SO4) in the cleaning solution may be 30,000 ppm or less, or 10 ppm to 30,000 ppm.

[0119] For example, the components and content of the cleaning solution can be confirmed by inductively coupled plasma (ICP) analysis.

[0120] 12, the cleaning solution according to the comparative example of the present invention may include a third cleaning solution that is obtained by discharging the second cleaning solution through a wastewater treatment process described below. The cleaning solution according to the comparative example of the present invention may be a recovered third cleaning solution.

[0121] The wastewater treatment process may be performed by a wastewater treatment device. For example, the wastewater treatment device may include an excess liquid tank, a submersion tank, a settling tank, a filter unit, a sludge discharge unit, etc. Other domestic wastewater may be introduced into the excess liquid tank. The second cleaning solution may be discharged as a third cleaning solution by the wastewater treatment device.

[0122] The cleaning solution according to the comparative example of the present invention may contain a low concentration of lithium (Li). For example, the lithium (Li) concentration of the cleaning solution according to the comparative example of the present invention may be less than 3500 ppm, or between 1000 ppm and 3000 ppm. The cleaning solution according to the comparative example of the present invention may also contain excessive amounts of impurities. For example, the impurities may include sodium (Na), sulfate (SO4), etc. For example, the impurity concentration of the cleaning solution may exceed 30,000 ppm. For example, the sodium (Na) concentration of the cleaning solution may exceed 1000 ppm, or between 1000 ppm and 90,000 ppm. For example, the potassium (K) concentration of the cleaning solution may exceed 10,000 ppm, or between 10,000 ppm and 30,000 ppm. For example, the magnesium (Mg) concentration of the cleaning solution may exceed 5,000 ppm, or between 5,000 ppm and 20,000 ppm. For example, the cleaning solution may have a chlorine (Cl) concentration greater than 100,000 ppm, or between 100,000 ppm and 200,000 ppm. For example, the cleaning solution may have a sulfate (SO4) concentration greater than 30,000 ppm, or between 30,000 ppm and 300,000 ppm.

[0123] The cleaning solution according to the embodiment of the present invention may have the following advantages by eliminating the wastewater treatment process described above. The cleaning solution according to the embodiment of the present invention may contain a high concentration of lithium. Furthermore, the cleaning solution according to the embodiment of the present invention may contain no or only trace amounts of impurities, thereby providing a high-quality cleaning solution. Lithium may be recovered more economically and easily using the cleaning solution according to the embodiment of the present invention. The recovered lithium may be recycled into lithium secondary batteries.

[0124] Cleaning liquid recovery device 13 is a schematic diagram illustrating a cleaning liquid recovery device according to an embodiment of the present invention. Referring to FIG. 13, the cleaning liquid recovery device according to the embodiment of the present invention may include an additional tank unit, a valve unit, a line unit, a pump unit, etc.

[0125] Use of cleaning fluid The cleaning solution according to the present invention may be used to recover a lithium precursor, which may then be used as a raw material for producing a positive electrode active material.

[0126] 14 is a flow chart illustrating a method for recovering a lithium precursor according to an embodiment of the present invention, and FIG. 15 is a flow chart illustrating a method for preparing a first solution.

[0127] 14, a method for extracting a lithium precursor may include preparing a first solution containing lithium ions (S500), preparing a second solution using wastewater generated during the washing process of the positive electrode active material (S600), adding the second solution to the first solution to prepare a third solution (S700), removing precipitated solid impurities (S800), and extracting the lithium precursor (S900). Finally, the lithium precursor may be extracted from the wastewater generated during the washing process of the positive electrode active material and the discarded lithium transition metal composite oxide. In this case, the second solution may include a cleaning solution according to an embodiment of the present invention.

[0128] 15, a method S500 for preparing a first solution from a discarded lithium transition metal composite oxide ML1 may include adding the discarded lithium transition metal composite oxide ML1 to an acid solution AS and filtering to remove undissolved solids (S510), adding sodium hydroxide (NaOH) BS1 and filtering to remove precipitate (S530), adding a transition metal extractant TE to extract transition metals (S550), adding sodium phosphate (NaPO) and filtering to obtain precipitated lithium phosphate (LiPO) (S570), dissolving the lithium phosphate in a sulfuric acid solution (S590), and adding ferric sulfate (Fe(SO)) and filtering to remove precipitated iron phosphate (FePO) (S590). Finally, a first solution containing lithium ions may be prepared from the discarded lithium transition metal composite oxide ML1.

[0129] The discarded lithium transition metal composite oxide ML1 may be derived from powder obtained by crushing discarded lithium secondary batteries or waste generated during the manufacturing process of lithium secondary batteries. For example, the discarded lithium transition metal composite oxide ML1 may include a compound represented by the following Chemical Formula 3: [Chemical formula 3] LiM1 a M2 b M3 c M4 d O2

[0130] In Chemical Formula 3, 0≦a≦1, 0≦b≦1, 0≦c≦1, 0≦d≦1, and a+b+c+d=1. Each of M1, M2, M3, and M4 in Chemical Formula 3 may be an element selected from Ni, Co, Al, Cu, Mn, Ti, Mo, Zn, Zr, Si, Ge, V, Cr, B, Mg, Na, Sr, Ag, Nb, Ga, Ca, or Ba.

[0131] The discarded lithium transition metal composite oxide ML1 may be an NCA-based oxide containing nickel (Ni), cobalt (Co), and aluminum (Al), or an NCM-based oxide containing nickel (Ni), cobalt (Co), and manganese (Mn).

[0132] Among the raw materials that can be used for the waste lithium transition metal composite oxide ML1, the powder obtained by crushing waste lithium secondary batteries can be obtained by crushing, heat treating, and sorting waste lithium secondary batteries. The powder obtained by crushing waste lithium secondary batteries can include materials derived from the positive electrode, negative electrode, separator, and electrolyte. In one embodiment, the material derived from the positive electrode can be aluminum (Al). The material derived from the negative electrode can be copper (Cu).

[0133] Among the waste materials that can be used as raw materials for the lithium transition metal composite oxide ML1, the waste generated during the manufacturing process of the lithium secondary battery may be a positive electrode active material and / or a positive electrode that has been crushed, heat-treated, and sorted. Alternatively, the waste generated during the manufacturing process of the lithium secondary battery may be a positive electrode slurry that has been subjected to solid-liquid separation and heat-treatment. The waste generated during the manufacturing process of the lithium secondary battery may include materials derived from the positive electrode active material, the positive electrode, and the positive electrode slurry. In one embodiment, the material derived from the positive electrode may be nickel (Ni).

[0134] The acid solution AS may contain at least one selected from the group consisting of sulfuric acid (H2SO4), hydrochloric acid (HCl), nitric acid (HNO3), and phosphoric acid (H3PO4). When the acid solution AS is added, hydrogen peroxide (H2O2) and / or sulfur dioxide (SO2) may be added together to promote the dissolution of the transition metal.

[0135] The addition of sodium hydroxide BS1 can be carried out within a pH range where manganese (Mn), cobalt (Co), and nickel (Ni) do not readily precipitate. In one embodiment, when the amount of sodium hydroxide added is adjusted so that the pH is in the range of 3 to 4, iron (Fe) can be precipitated as Fe(OH)3 while manganese (Mn), cobalt (Co), and nickel (Ni) remain in ionic form.

[0136] The precipitate generated after adding sodium hydroxide BS1 may include transition metals excluding manganese (Mn), cobalt (Co), and nickel (Ni). In one embodiment, the precipitate may include iron (Fe), aluminum (Al), copper (Cu), zinc (Zn), magnesium (Mg), and / or calcium (Ca). The precipitate may include divalent and / or trivalent transition metals excluding manganese (Mn), cobalt (Co), and nickel (Ni). In one embodiment, the precipitate may include aluminum hydroxide (Al(OH)3) and / or copper hydroxide (Cu(OH)2).

[0137] The precipitate generated after adding sodium hydroxide BS1 can be filtered using a solid-liquid separation device such as a filter, filter press, or decanter (centrifuge).

[0138] After adding sodium hydroxide BS1 and removing the precipitate by filtration, unprecipitated transition metal elements may still be present. In one embodiment, small amounts of aluminum (Al), copper (Cu), and / or iron (Fe) may still be present. The unprecipitated elements may be included in the first solution produced.

[0139] The transition metal extractant TE may include a phosphoric acid-based compound, a phosphonic acid-based compound, a phosphinic acid-based compound, and / or a carboxylic acid-based compound.

[0140] Extracting transition metals by adding a transition metal extractant (TE) (S550) can be performed by gradually increasing the pH. In one embodiment, manganese (Mn) can be extracted by adding di-(2-ethylhexyl)phosphoric acid (DEHPA) while maintaining the pH in the range of 3 to 4. Next, sodium hydroxide (NaOH) can be added to adjust the pH to 4 to 5, and then bis(2,2,4-trimethylpentyl)phosphinic acid (Cyanex 272) can be added to extract cobalt (Co). Next, sodium hydroxide (NaOH) can be added to adjust the pH to 5 to 6, and then 2-ethylhexyl-2-ethylhexylphosphonic acid (PC88A) can be added to extract nickel (Ni).

[0141] A saponified transition metal extractant may be used instead of the transition metal extractant TE. The mechanism by which transition metals are extracted with the transition metal extractant TE is that the hydrogen ions of the transition metal extractant TE are substituted with transition metal ions, and the substituted transition metal ions bind to the anions of the transition metal extractant TE. In this case, the hydrogen ions released from the transition metal extractant TE lower the pH of the solution, which may make it difficult to extract transition metals by gradually increasing the pH as described above. Therefore, to compensate for this, a saponified transition metal extractant in which the hydrogen ions of the transition metal extractant TE are substituted with sodium ions may be used.

[0142] After the transition metal extractant TE is added to extract the transition metals, the resulting first solution may still contain unprecipitated transition metal elements. In one embodiment, small amounts of aluminum (Al), copper (Cu), and / or iron (Fe) may still be present. The unprecipitated elements may be included in the resulting first solution.

[0143] In the method for producing the first solution described above, the steps of adding sodium phosphate (NaPO) and then obtaining precipitated lithium phosphate (LiPO) by filtration (S570) and / or adding ferric sulfate (Fe(SO)) and then removing precipitated iron phosphate (FePO) by filtration (S590) may be omitted.

[0144] 14, the second cleaning solution recovered by the method according to the embodiment of the present invention described above, i.e., the second solution, may contain lithium hydroxide (LiOH) and / or lithium carbonate (LiCO) (S600). The second solution may further contain sodium hydroxide (NaOH). The mass of lithium relative to the total mass of the second solution may be 1,000 ppm to 10,000 ppm.

[0145] The pH of the second solution may be between 10 and 15. Such a basic pH may be due to lithium hydroxide (LiOH) and / or lithium carbonate (Li2CO3) present in the second solution.

[0146] In the step of calcining a mixture of a transition metal precursor and a lithium precursor to prepare a first positive electrode active material (S201), the lithium precursor may be a lithium precursor extracted by the method for extracting a lithium precursor of the present invention. That is, the waste liquid generated in the process of washing the positive electrode active material prepared using the lithium precursor extracted by the present invention may be further used as a raw material for preparing the second solution of the present invention.

[0147] The first solution may be added to the second solution to prepare a third solution (S700). The addition of the second solution (S700) may be for removing impurity ions, excluding lithium ions, from the first solution. The addition of the second solution (S700) may also be for recovering lithium ions contained in the second solution as a lithium precursor without performing a separate process.

[0148] The second solution (S700) may be added so that the weight of lithium contained in the third solution relative to the total weight of the third solution (weight of lithium contained / weight of third solution) is not less than 3,000 ppm. In one embodiment, the first solution may be added to the second solution (S303) while maintaining the pH of the third solution in the range of 7 to 11. By adding the second solution while satisfying the lithium content condition, an environment may be created in which precipitation of lithium ions is difficult but precipitation of ions other than lithium is easy. This may result in the extraction of impurity ions other than lithium ions while preventing a decrease in the lithium ion content, thereby achieving the effect of later obtaining a high-purity lithium precursor.

[0149] When the second solution is added to the first solution, precipitated solid impurities may occur. Removing the precipitated solid impurities (S800) may utilize a solid-liquid separation device such as a filter, a filter press, or a decanter (centrifuge).

[0150] The precipitated solid-phase impurities may include impurities that remain unprecipitated after adding sodium hydroxide BS1 to the acidic solution containing the discarded lithium transition metal composite oxide ML1 and then filtering to remove the precipitate (S530). The precipitated solid-phase impurities may include transition metal elements excluding manganese (Mn), cobalt (Co), and nickel (Ni). In one embodiment, the solid-phase impurities may include iron (Fe), aluminum (Al), copper (Cu), zinc (Zn), magnesium (Mg), and / or calcium (Ca).

[0151] The precipitated solid impurities may include impurities remaining after extracting transition metals from the acidic solution containing the discarded lithium transition metal composite oxide ML1 (S550). In one embodiment, the precipitated solid impurities may include manganese (Mn), cobalt (Co), and / or nickel (Ni).

[0152] The precipitated solid impurities may include divalent and / or trivalent transition metals. In one embodiment, the precipitated solid impurities may include Al(OH)3 and / or Co(OH)2. The precipitation may occur due to the basicity of the second solution. The hydroxide ions (OH) from the second solution may be present in the precipitated solid impurities. - ) may combine with divalent and / or trivalent transition metal ions to form the precipitated solid-phase impurities. Unlike conventional methods for recovering valuable metals, the present invention reduces the use of basic solutions that cause environmental pollution by introducing a second solution instead of a conventional basic solution.

[0153] A lithium precursor may be extracted from the third solution from which the impurities have been removed (S900). An alkali carbonate may be added to the third solution from which the impurities have been removed, and a lithium precursor in the form of lithium carbonate (Li2CO3) may be recovered by solid-liquid separation. In one embodiment, the alkali carbonate may be sodium carbonate (Na2CO3). For example, the obtained lithium carbonate may be used as a raw material for a nickel-containing positive electrode active material in which the mole ratio of nickel to the moles of metal elements excluding lithium in the positive electrode active material is 70% or less, 60% or less, or 50% or less.

[0154] An additional process may be performed to extract a lithium precursor in the form of sodium hydroxide (LiOH). The obtained lithium carbonate may be dispersed in an aqueous solution, and a hydroxide may be added to the aqueous solution. In one embodiment, calcium hydroxide (Ca(OH)2) is added as the hydroxide, and then calcium carbonate (CaCO3) is removed by solid-liquid separation, and a lithium precursor in the form of lithium hydroxide (LiOH) is extracted by evaporation. The obtained lithium hydroxide may be used as a raw material for a high-nickel positive electrode active material in which the moles of nickel exceed 50% of the moles of metal elements excluding lithium in the positive electrode active material. In one embodiment, the high-nickel positive electrode active material is LiNi 0.8 Co 0.15 Al 0.05 It can be O2.

[0155] The lithium precursor obtained by the present invention can be used as a raw material for preparing a positive electrode active material. For example, the transition metal precursor used as a raw material for preparing the positive electrode active material can be a transition metal precursor represented by the following Chemical Formula 4: [Chemical formula 4] M9 i M10 j M11 k M12 l O2

[0156] In the above Chemical Formula 4, 0≦i≦1, 0≦j≦1, 0≦k≦1, 0≦l≦1, and i+j+k+l=1; Each of M9, M10, M11, and M12 in Chemical Formula 4 is an element selected from Ni, Co, Al, Cu, Mn, Ti, Mo, Zn, Zr, Si, Ge, V, Cr, B, Mg, Na, Sr, Ag, Nb, Ga, Ca, or Ba.

[0157] The present invention will be described in more detail below with reference to examples. However, these examples are for illustrative purposes only and the scope of the present invention is not limited to these examples.

[0158] Example The second washing solution was collected and prepared as follows:

[0159] Ni 0.88 Co 0.09 Al 0.03 Positive electrode active material particles were prepared by mixing (OH)2 and lithium hydroxide (LiOH) and then calcining the mixture. The positive electrode active material particles were then mixed with a first cleaning solution. The first cleaning solution contained cobalt sulfate (CoSO4), sodium hydroxide (NaOH), and distilled water. Thus, the mixture contained both a solid mixture and a liquid mixture.

[0160] The mixture was filtered, and the liquid mixture was separated to obtain the second washing liquid. The second washing liquid was collected to obtain the washing liquid of the present invention.

[0161] Comparative Example A third cleaning solution was recovered and prepared. The third cleaning solution was the second cleaning solution described above that had been discharged after undergoing a wastewater treatment process. The wastewater treatment process was carried out using a wastewater treatment device. The wastewater treatment device included an excess liquid tank, a submersion tank, a settling tank, a filter / filtration section, and a sludge treatment / discharge section.

[0162] Experimental example: Component analysis The components and contents of the cleaning solutions according to the examples and comparative examples were analyzed by ICP, and the results are shown in Table 1.

[0163] [Table 1]

[0164] Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention may be embodied in other specific forms without changing the technical spirit or essential features thereof. Therefore, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting.

Claims

1. synthesizing positive electrode active material particles containing a lithium composite oxide containing nickel; adding a first cleaning solution to the positive electrode active material particles and mixing the first cleaning solution, the first cleaning solution including a coating raw material, a precipitant, and a solvent; filtering the mixture to separate a liquid mixture; recovering the separated liquid mixture; Including, The concentration of lithium in the recovered cleaning solution is 3500 ppm or more. How to recover cleaning fluid.

2. The positive electrode active material particles include a nickel-containing lithium composite oxide represented by the following chemical formula 1: The method for recovering a cleaning solution according to claim 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the formula 1, 0.9≦a1≦1.8, 0.8≦x1≦1, 0≦y1≦0.2, 0≦z1≦0.2, 0.9≦x1+y1+z1≦1.1, and 0≦b1≦0.1; Said M 1 and M 2 are each independently one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr; The X includes one or more elements selected from the group consisting of F, P, and S.

3. The coating source material includes a cobalt compound; The method for recovering a cleaning liquid according to claim 1 .

4. The precipitating agent comprises sodium hydroxide. The method for recovering a cleaning liquid according to claim 1 .

5. The solvent includes at least one of distilled water and an alkaline solution. The method for recovering a cleaning liquid according to claim 1 .

6. The lithium concentration of the recovered cleaning solution is 3500 ppm to 10000 ppm. The method for recovering a cleaning liquid according to claim 1 .

7. The concentration of impurities in the recovered cleaning solution is 20 ppm to 30,000 ppm. The method for recovering a cleaning liquid according to claim 1 .

8. The system includes a tank section, a valve section, a line section, and a pump section, The cleaning liquid is recovered by the recovery method according to claim 1. Cleaning fluid recovery device.

9. The cleaning liquid is recovered by the method of recovering the cleaning liquid according to claim 1, The lithium concentration is 3500 ppm or more; Cleaning solution.

Images