Method for manufacturing positive electrode active material for rechargeable lithium battery and rechargeable lithium battery

Abstract

The invention relates to a method for manufacturing a positive electrode active material for a rechargeable lithium battery and a rechargeable lithium battery. The method of manufacturing a positive electrode active material includes a first grinding step of grinding a positive electrode scrap of a rechargeable lithium battery; a heat treatment step of heat-treating the ground positive electrode scrap; a second grinding step of grinding the heat-treated positive electrode scrap; separating a current collector component from an active material component from the heat-treated and ground positive electrode scrap; rinsing the separated active component with a solvent, separating the solid from the liquid, and drying the solid. By this method, a positive electrode active material can be efficiently recovered from a positive electrode scrap generated during manufacturing of a rechargeable lithium battery.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of Korean Patent Application No. 10-2024-0041605 filed on March 27, 2024, in the Korean Intellectual Property Office, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to a method for manufacturing a positive electrode active material for a rechargeable lithium battery and a rechargeable lithium battery manufactured by using the positive electrode active material, and more particularly, to a method for manufacturing a positive electrode active material using positive electrode scrap and a rechargeable lithium battery manufactured by using the positive electrode scrap. Background Art

[0004] Due to their high operating voltage, excellent charge / discharge cycle, and adaptability to compactness, rechargeable lithium batteries are widely used as power sources for communication and information devices such as cellular phones, laptop computers, and digital cameras. As such, with the potential for commercialization of electric vehicles, demand for rechargeable lithium batteries is rapidly increasing.

[0005] Accordingly, the amount of positive electrode scrap (positive electrode current collector coated with a positive electrode active material layer) generated during the production of rechargeable lithium batteries has increased significantly. Since positive electrode scrap contains a large amount of precious metals (such as lithium, cobalt, nickel, and manganese), it is a material with very high recycling value.

[0006] Since huge economic benefits are expected when precious metals are recovered, methods of recovering precious metals are being actively studied. Summary of the Invention

[0007] Embodiments of the present disclosure provide methods for recovering and reusing positive electrode active materials from positive electrode waste.

[0008] Embodiments of the present disclosure provide a rechargeable lithium battery including a recycled positive electrode active material.

[0009] According to an embodiment of the present disclosure, a method for manufacturing a positive electrode active material may include: a first grinding step of grinding positive electrode waste of a rechargeable lithium battery; a heat treatment step of heat-treating the ground positive electrode waste; a second grinding step of grinding the heat-treated positive electrode waste; separating a current collector component from an active material component from the positive electrode waste ground in the second grinding step; washing the separated active material component with a solvent; separating the washed separated active material component into a solid and a liquid; and drying the solid.

[0010] According to an embodiment of the present disclosure, a method for manufacturing a positive electrode active material may include: a first milling step of milling positive electrode waste of a rechargeable lithium battery; a heat treatment step of heat-treating the milled positive electrode waste at a temperature of about 400° C. to about 600° C.; a second milling step of milling the heat-treated positive electrode waste; and separating a current collector component from an active material component from the positive electrode waste milled in the second milling step.

[0011] According to an embodiment of the present disclosure, a rechargeable lithium battery includes: a positive electrode including a positive electrode active material manufactured using one of the methods discussed above; a negative electrode including a negative electrode active material; and an electrolyte. The amount of aluminum in the positive electrode active material may be in a range of about 0.001 wt% to about 3 wt% based on the total weight of the positive electrode active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A simplified conceptual diagram showing a rechargeable lithium battery according to an embodiment of the present disclosure is illustrated.

[0013] Figures 2 to 5 A simplified diagram showing a rechargeable lithium battery according to an embodiment of the present disclosure is illustrated.

[0014] Figure 6 A flowchart illustrating a method of manufacturing a positive electrode active material according to an embodiment of the present disclosure is explained.

[0015] Figure 7 A flowchart illustrating a method of manufacturing a positive electrode active material according to another embodiment of the present disclosure is explained.

[0016] Figure 8 A graph illustrating lifespan retention rates (ie, discharge capacity retention rates) of rechargeable lithium batteries manufactured according to the embodiment and comparative examples is illustrated.

[0017] Figure 9 Graphs showing measurement results of the capacities (ie, specific capacities) of rechargeable lithium batteries manufactured according to the embodiment and comparative examples are illustrated. DETAILED DESCRIPTION

[0018] In order to fully understand the configuration and effects of the present disclosure, some embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be noted that the present disclosure is not limited to the following exemplary embodiments and can be implemented in various forms. On the contrary, the exemplary embodiments are provided only to disclose the present disclosure and enable those skilled in the art to fully understand the scope of the present disclosure.

[0019] In this description, it will be understood that when an element is referred to as being "on" another element, the element may be directly on the other element or an intervening element may be present therebetween. In the accompanying drawings, the size (e.g., thickness) of some components is exaggerated for the purpose of effectively explaining the technical content. Throughout the specification, the same reference numerals refer to the same elements.

[0020] Some embodiments described in detail in this description will be discussed with reference to the cross-sectional views and / or plan views that are ideal exemplary views of the present disclosure. In the accompanying drawings, in order to effectively explain the technical content, the sizes (e.g., thickness) of the layers and regions are magnified. Accordingly, the regions exemplarily illustrated in the accompanying drawings have general characteristics, and the shapes of the regions exemplarily illustrated in the accompanying drawings are used to exemplarily disclose specific shapes, but are not limited to the scope of the present disclosure. It will be understood that although the terms "first," "second," "third," etc. may be used in this article to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. The embodiments explained and illustrated in this article include their supplementary embodiments.

[0021] The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the present disclosure. As used herein, the singular is intended to include the plural. The terms "comprises / includes" and / or "comprising / including" used in this specification do not exclude the presence or addition of one or more other components.

[0022] In the present invention, the average particle size D 50 D refers to the average diameter of particles whose cumulative volume corresponds to 50% by volume in a size distribution (e.g., cumulative distribution), and refers to a value corresponding to a particle size of 50% from the smallest particle when the total number of particles is 100% in a distribution curve accumulated in order from the smallest particle size to the largest particle size. D can be measured using a laser diffraction method for particles using a particle size analyzer. 50 .

[0023] The present disclosure relates to a rechargeable lithium battery manufactured using a method of manufacturing a positive electrode active material for a rechargeable lithium battery, in which positive electrode scrap for a rechargeable lithium battery is used.

[0024] Figure 1 A simplified conceptual diagram illustrating a rechargeable lithium battery according to an embodiment of the present disclosure is illustrated. Figure 1 , a rechargeable lithium battery may include a positive electrode 10, a negative electrode 20, a separator 30, and an electrolyte ELL.

[0025] 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 contact the electrolyte ELL. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in the electrolyte ELL.

[0026] The electrolyte ELL may be a medium through which lithium ions are transferred between the positive electrode 10 and the negative electrode 20. In the electrolyte ELL, the lithium ions may move toward one of the positive electrode 10 and the negative electrode 20 through the separator 30.

[0027] Positive electrode 10

[0028] The positive electrode 10 for a rechargeable lithium battery may include a positive electrode current collector COL1 and a positive electrode active material layer AML1 formed on the positive electrode current collector COL1. The positive electrode active material layer AML1 may include a positive electrode active material and further include a binder and / or a conductive material. Aluminum (Al) foil may be used as the positive electrode current collector COL1, but the present disclosure is not limited thereto.

[0029] Negative electrode 20

[0030] The negative electrode 20 for a rechargeable lithium battery may include a negative electrode current collector COL2 and a negative electrode active material layer AML2 on the negative electrode current collector COL2. The negative electrode active material layer AML2 may include a negative electrode active material and may further include a binder and / or a conductive material.

[0031] The negative electrode active material layer AML2 may include about 90 wt % to about 99 wt % of a negative electrode active material, about 0.5 wt % to about 5 wt % of a binder, and about 0 wt % to about 5 wt % of a conductive material.

[0032] The binder can be used to improve the attachment of the negative electrode active material particles to each other and to the negative electrode current collector COL 2. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0033] The non-aqueous binder may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0034] The aqueous binder may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinyl pyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinyl pyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol or a combination thereof.

[0035] When an aqueous binder is used as a binder in the negative electrode active material layer AML2, a cellulose compound capable of providing viscosity may be further included. The cellulose compound may include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and alkali metal salts thereof. The alkali metal may include Na, K, or Li.

[0036] The dry binder may include a fiberizable polymer material, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0037] The conductive material can be used to provide an electrode having conductivity, and any suitable conductive material that does not cause chemical changes in the battery can be used as the conductive material. For example, the conductive material may include carbon materials (such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes); metal powders or metal fibers including one or more of copper, nickel, aluminum, and silver; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0038] The negative electrode current collector COL2 may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0039] Negative electrode active material

[0040] The negative electrode active material in the negative electrode active material layer AML2 may include a material that can reversibly intercalate and deintercalate lithium ions, lithium metal, a lithium metal alloy, a material that can dope and dedope lithium, or a transition metal oxide.

[0041] The material that can reversibly intercalate and deintercalate lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. The crystalline carbon may include graphite (such as amorphous, flaky, sheet-like, spherical, or fibrous natural or artificial graphite), and the amorphous carbon may include soft carbon, hard carbon, mesophase pitch carbon, or calcined coke.

[0042] The lithium metal alloy may include an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0043] The materials that can be doped and de-doped with lithium may include Si-based negative electrode active materials or Sn-based negative electrode active materials. The Si-based negative electrode active materials may include silicon, silicon-carbon composites, SiO x (where 0 < x ≤ 2), Si-Q alloys (where Q is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element (excluding Si), Group 15 element, Group 16 element, transition metal, rare earth element or a combination thereof) or a combination thereof. The Sn-based negative electrode active materials may include Sn, SnO x (where 0 < x ≤ 2) (for example, SnO2), Sn-based alloys, and combinations thereof.

[0044] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to an embodiment, the silicon-carbon composite may have a structure in which amorphous carbon is coated on the surface of silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which primary silicon particles are aggregated and an amorphous carbon coating (shell) located on the surface of the secondary particles. 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.

[0045] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and may also include an amorphous carbon coating located on the surface of the core.

[0046] The Si-based negative electrode active material or the Sn-based negative electrode active material may be used in combination with a carbon-based negative electrode active material.

[0047] Separator 30

[0048] Based on the type of rechargeable lithium battery, the separator 30 may be present between the positive electrode 10 and the negative electrode 20. The separator 30 may include one or more of a polyethylene separator, a polypropylene separator, and a polyvinylidene fluoride separator, and may be a multi-layer separator thereof (such as a polyethylene / polypropylene bilayer separator, a polyethylene / polypropylene / polyethylene trilayer separator, and a polypropylene / polyethylene / polypropylene trilayer separator).

[0049] The separator 30 may include a porous substrate and a coating located on one surface or the opposite surface of the porous substrate, and the coating includes an organic material, an inorganic material, or a combination thereof.

[0050] The porous substrate may be a polymer layer comprising one selected from polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetals, polyamides, polyimides, polycarbonates, polyetherketones, polyaryletherketones, polyetherimides, polyamideimides, polybenzimidazoles, polyethersulfones, polyphenylene oxides, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fibers, and polytetrafluoroethylene (e.g., Teflon), or a copolymer or mixture comprising two or more of the above-mentioned materials.

[0051] The organic material may include a polyvinylidene fluoride-based copolymer or a (meth)acrylic acid-based copolymer.

[0052] The inorganic material may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, or combinations thereof, but the present disclosure is not limited thereto.

[0053] The organic material and the inorganic material may be present as a mixture in one coating layer or may be present as a stack of a coating layer including an organic material and a coating layer including an inorganic material.

[0054] Electrolyte ELL

[0055] The electrolyte ELL for a rechargeable lithium battery may include a non-aqueous organic solvent and a lithium salt.

[0056] The non-aqueous organic solvent may serve as a medium for transporting ions participating in the electrochemical reaction of the battery.

[0057] The non-aqueous organic solvent may include a carbonate solvent, an ester solvent, an ether solvent, a ketone solvent, an alcohol solvent, an aprotic solvent, or a combination thereof.

[0058] The carbonate-based solvent may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), or butylene carbonate (BC).

[0059] The ester solvent may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonolactone, valerolactone, or caprolactone.

[0060] Ether solvents may include dibutyl ether, tetraglyme, diglyme, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, or tetrahydrofuran. Ketone solvents may include cyclohexanone. Alcohol solvents may include ethanol and / or isopropanol. Aprotic solvents may include nitriles (such as R-CN, where R is a hydrocarbon group having a C2 to C20 linear, branched, or cyclic structure and may include a double bond, an aromatic ring, or an ether bond); amides (such as dimethylformamide); dioxolanes (such as 1,3-dioxolane or 1,4-dioxolane); or sulfolane.

[0061] The nonaqueous organic solvent may be used alone or as a mixture of two or more species.

[0062] In addition, when a carbonate-based solvent is used, cyclic carbonate and chain carbonate may be mixed and used, and the cyclic carbonate and chain carbonate may be mixed in a volume ratio of about 1:1 to about 1:9.

[0063] The lithium salt may be a material dissolved in a non-aqueous organic solvent to serve as a supply source of lithium ions in a battery, and plays a role in ensuring the basic operation of a rechargeable lithium battery and promoting the movement of lithium ions between a positive electrode and a negative electrode. The lithium salt may include, for example, a material selected from 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+1 SO2) (wherein x and y are integers between 1 and 20), at least one of lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluoro(oxalato)borate (LiDFOB), lithium difluorobis(oxalato)phosphate (LiDFBOP) and lithium bis(oxalato)borate (LiBOB).

[0064] Rechargeable lithium battery

[0065] Based on the shape of the rechargeable lithium battery, the rechargeable lithium battery can be classified into cylindrical, prismatic, pouch and coin types. Figures 2 to 5 A simplified diagram showing a rechargeable lithium battery according to an embodiment is illustrated in FIG. Figure 2 shows a cylindrical battery, Figure 3 A prismatic cell is shown, and Figure 4 and Figure 5 Pouch type battery is shown. Figures 2 to 5, the rechargeable lithium battery 100 may include an electrode assembly 40 in which a separator 30 is inserted between a positive electrode 10 and a negative electrode 20, and may also include a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be immersed in an electrolyte (not shown). Figure 2 As explained in FIG. 1 , the rechargeable lithium battery 100 may include a sealing member 60 that seals the housing 50. Figure 3 As explained in , the rechargeable lithium 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. Figure 4 and Figure 5 As shown in FIG, the rechargeable lithium battery 100 may include an electrode tab 70, or a positive electrode tab 71 and a negative electrode tab 72, which serve as an electrical path for guiding current generated in the electrode assembly 40 to the outside.

[0066] The rechargeable lithium battery according to an embodiment of the present disclosure may be used in a motor vehicle, a mobile phone, and / or any other electronic device, but the present disclosure is not limited thereto.

[0067] Production of positive electrode active material

[0068] The present disclosure relates to a method of manufacturing a positive electrode active material for a rechargeable lithium battery, wherein positive electrode scrap for the rechargeable lithium battery is used.

[0069] Figure 6 A flowchart illustrating a method of manufacturing a positive electrode active material according to an embodiment of the present disclosure is illustrated. Figure 6 , a method of manufacturing a positive electrode active material according to an embodiment of the present disclosure will be described in detail below.

[0070] refer to Figure 6 , the method for manufacturing a positive electrode active material according to an embodiment of the present disclosure may include performing a first grinding step (S100) on a positive electrode waste of a rechargeable lithium battery, a heat treatment step (S200) of heat-treating the first grinding result, performing a second grinding step (S300) on the heat-treated result, separating a current collector component from an active material component (positive electrode active material component) from the second grinding result (S400), allowing a solvent to receive and rinse the separated positive electrode active material component (S500), separating the rinsed result into a solid and a liquid (S600), and drying the solid (S700).

[0071] The first grinding step S100 may include grinding the positive electrode scrap into an appropriate size or a target size.

[0072] Positive electrode scrap can be the residue remaining after punching during the process of manufacturing a positive electrode sheet comprising a positive electrode active material layer on a current collector. Alternatively, positive electrode scrap can be obtained by collecting positive electrodes that have developed defects during the positive electrode manufacturing process. Alternatively, positive electrode scrap can be obtained by separating positive electrodes from discarded rechargeable lithium batteries.

[0073] In an embodiment involving the production of a positive electrode sheet, a slurry can be prepared by adding N-methyl-2-pyrrolidone (NMP) to a positive electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVdF) as a binder and mixing. The positive electrode active material may include, for example, lithium cobalt oxide (such as LiCoO2 (LCO)), lithium nickel cobalt aluminum oxide (NCA) containing nickel, cobalt, and aluminum, or lithium nickel cobalt manganese oxide (NCM) containing nickel, cobalt, and manganese. The slurry may be coated on an aluminum current collector. The aluminum current collector coated with the slurry may be dried in a vacuum oven at about 120°C to prepare a positive electrode sheet. The positive electrode sheet may be punched into a positive electrode plate of a specific size, and the remaining portion (or waste portion) of the positive electrode sheet may be used as positive electrode scrap.

[0074] The positive electrode active material layer of the positive electrode waste can be formed from a slurry in which a positive electrode active material, a conductive material, a binder, and a solvent are mixed. The solvent in the slurry is volatile, and the binder binds the positive electrode active material and the conductive material. When the binder is removed from the positive electrode active material mixture, the positive electrode active material can be separated from the current collector.

[0075] The method for separating positive electrode active material from positive electrode waste according to a comparative example of the present disclosure may include only a physical grinding step and a classification step. In the physical grinding step according to the comparative example, the binder may not be completely removed, thereby reducing the recovery rate of the positive electrode active material. For example, in the case of positive electrode plates with a high mixing density, when processed using the method of the comparative example, the recovery rate of the product may be significantly reduced.

[0076] In the method for separating a positive electrode active material from positive electrode waste according to an embodiment of the present disclosure, a pretreatment step may be further included to maximize the recovery rate of the positive electrode active material. The pretreatment step may be performed to effectively separate the current collector of the positive electrode plate having a high mixing density from the positive electrode active material, thereby increasing the recovery rate of the positive electrode active material.

[0077] In an embodiment, the positive electrode scrap may have a mixed density of about 2 g / cc to about 4 g / cc.

[0078] The first grinding step may use at least one selected from a cutting mill, a shearing mill, a pin mill, an impact mill, a ball mill, and a sand mill. The first grinding step may be performed two or more times.

[0079] In an embodiment, a cutting pulverizer may be used to perform the first grinding step, and the cutting pulverizer may grind the positive electrode scrap into a size equal to or less than about 1 cm. In the first grinding step, due to the difference in brittleness and / or ductility between the positive electrode active material layer and the current collector, separation of the positive electrode active material layer from the current collector may be possible to a certain extent.

[0080] The first grinding step can cut the positive electrode scrap into an appropriate size in which the horizontal length and the vertical length are in the range of about 0.1 cm to about 1 cm. Such a size can facilitate efficient heat treatment in the subsequent heat treatment step S200. The first grinding result can have an average particle size (D) of about 0.1 cm to about 1 cm. 50 ), and is in the form of a powder.

[0081] The heat treatment step S200 may include heat treating the first grinding result. According to some embodiments of the present disclosure, the heat treatment step S200 may correspond to the pre-treatment step discussed above.

[0082] A heat treatment step according to some embodiments of the present disclosure may be performed to thermally decompose the conductive material and binder combined with the positive electrode active material. The heat treatment may thermally decompose the binder and conductive material in the positive electrode active material into CO2 and H2O and remove them. Following the removal of the binder, the recovery target (aggregated positive electrode active material) in powder form may be unraveled and screened. The heat treatment may remove residual organic materials including the binder combined with the positive electrode active material, thereby reducing the bonding force between the positive electrode active material and the binder.

[0083] The heat treatment may be performed at about 400° C. to about 600° C. When the heat treatment is performed at a temperature less than about 400° C., it may be difficult to remove the binder in the milled result. When the heat treatment is performed at a temperature greater than about 600° C., the heat treatment may be performed above the melting point of the current collector, which may hinder the separation between the positive electrode active material and the current collector.

[0084] The heat treatment may be performed for a time in the range of about 30 minutes to about 3 hours, which is sufficient to completely thermally decompose the binder. When the heat treatment is performed for less than about 30 minutes, incomplete thermal decomposition of the binder may occur.

[0085] In an embodiment, the heat treatment equipment may be various types of furnaces. For example, the heat treatment equipment may be a box-type furnace, and in consideration of productivity, may be a rotary kiln capable of continuous treatment.

[0086] The heat treatment may be performed under vacuum or in a gaseous environment such as nitrogen, helium, and / or argon.

[0087] The second grinding step S300 may include grinding the heat treatment result into a fine particle size. The second grinding step may use at least one selected from a cutting mill, a shearing machine, a pin mill, an impact mill, a ball mill, and a sand mill. The second grinding step may be performed two or more times. In an embodiment, the second grinding step may be performed by an impact mill, and the impact mill may grind the positive electrode waste into a powder form with a particle size equal to less than about 3 mm. The second grinding step may be a step in which the heat treatment result is cut into particles having an average particle size (D) of about 1 mm to about 3 mm. 50 ) of the fine-grained step.

[0088] In the present disclosure, a heat treatment step may be performed to reduce the adhesive force between the positive electrode active material and the binder, and then a second grinding step may be performed to effectively increase the recovery rate of the positive electrode active material.

[0089] The separation step S400 may include classifying the current collector component and the positive electrode active material component from the second milling result. The positive electrode active material component may have an average particle size (D 50 ).

[0090] The classification step may use a sieve. During the classification step, the positive electrode active material component of the second grinding result may pass through the sieve and fall downward, while the current collector component of the second grinding result may not pass through the sieve. Thus, the positive electrode active material component and the current collector component may be separated from each other. In embodiments, the sieve may have a mesh size ranging from about 100 mesh to about 1,000 mesh.

[0091] The rinsing step S500 may include adding the separated positive electrode active material component to a solvent and rinsing the positive electrode active material component using an ultrasonic generator. In the rinsing step S500, vibrations may be induced on the surface of the positive electrode active material component to remove residual organic materials with fine particles attached to the positive electrode active material component. In an embodiment, the ultrasonic oscillator of the ultrasonic generator may use a bolt-clamped Langevin type converter (BLT), wherein the ultrasonic wave has a frequency of about 40kHz and an intensity of about 50W to about 3,000W. In an embodiment, the ultrasonic treatment may be performed for about 10 seconds to about 100 seconds.

[0092] The solvent may include one of water, N-methyl-2-pyrrolidone (NMP), isopropyl alcohol (IPA), dimethyl sulfoxide (DMSO), dimethylformamide (DMF), N-cyclohexyl-2-pyrrolidone (CHP), ethanol, methanol, acetone, chlorobenzene, and dichlorobenzene. The solvent may include a solvent having a Hansen solubility parameter value equal to or greater than the Hansen solubility parameter value of polyvinylidene fluoride (PVDF). In embodiments, a solvent having a Hansen solubility parameter value of 2 to 3 may be used.

[0093] The separation step S600 may be performed by using gravity separation or magnetic separation.

[0094] The separation step S600 may separate the current collector component from the positive electrode active material component. According to an embodiment, the rinsed result may be centrifuged at about 1,000 rpm to about 5,000 rpm for about 1 minute to about 20 minutes to separate the solid from the liquid.

[0095] The separated liquid may be collected to be reused as a solvent in the washing step S500 .

[0096] In the solid drying step ( S700 ), the solid separated in the separation step ( S600 ) may be heat-treated to ultimately recover the positive electrode active material. The solid drying step ( S700 ) may be performed at a temperature of approximately 120° C. to approximately 180° C. Furthermore, the solid drying step ( S700 ) may be performed for approximately 2 hours to approximately 24 hours, but the present disclosure is not limited thereto.

[0097] The dried solid result can be provided in the form of a powder. The powder can contain essentially precious metals such as Co, Ni, Mn, and Li, and can contain small amounts of carbon and impurities such as Al, Fe, and Cu.

[0098] The dried solid may include a current collector component, and the amount of the current collector component in the dried solid may be in the range of about 0.001 wt % to about 3 wt % based on the total weight of the dried solid. The dried solid may have an average particle size (D 50 The positive electrode active material in the dried solid may have an average particle size (D 50 ). In an embodiment, the current collector component may include aluminum.

[0099] Figure 7 A flowchart illustrating a method of manufacturing a positive electrode active material according to another embodiment of the present disclosure is illustrated. Figure 7 , the following description will focus on a method of manufacturing a positive electrode active material according to another embodiment of the present disclosure.

[0100] A method for manufacturing a positive electrode active material according to another embodiment of the present disclosure may include performing a first grinding step (S110) on a positive electrode waste of a rechargeable lithium battery, heat-treating the first grinding result at a temperature of about 400°C to about 600°C (S210), performing a second grinding step (S310) on the heat-treated result, and separating a current collector component from an active material component (positive electrode active material component) from the second grinding result (S410).

[0101] In the following embodiments, the above reference Figure 6 The detailed description of the technical features discussed will be repeated, and the differences will be discussed in detail. The method of manufacturing a positive electrode active material according to another embodiment of the present disclosure may have the same characteristics as those of the reference Figure 6 The configuration of the method of manufacturing a positive electrode active material according to an embodiment of the present disclosure (including the first grinding step S100 , the heat treatment step S200 , the second grinding step S300 , and the separation step S400 ) is described as the same configuration.

[0102] In the heat treatment step S210 in the method for manufacturing a positive electrode active material according to another embodiment of the present disclosure, the first grinding result may be heat treated at a temperature of about 400°C to about 600°C. When the heat treatment is performed at a temperature of less than about 400°C, it may be difficult to remove the binder in the grinding result. When the heat treatment is performed at a temperature greater than about 600°C, the heat treatment may be performed above the melting point of the current collector, which may hinder the separation between the positive electrode active material and the current collector. The heat treatment may be performed for a time in the range of about 30 minutes to about 3 hours, which is sufficient to completely thermally decompose the binder. When the heat treatment is performed for less than about 30 minutes, incomplete thermal decomposition of the binder may occur.

[0103] In an embodiment, the heat treatment apparatus may be a furnace of various shapes. For example, the heat treatment apparatus may be a box-type furnace, and in consideration of productivity, may be a rotary kiln capable of continuous processing.

[0104] The heat treatment may be performed under vacuum or in a gaseous environment such as nitrogen, helium, and / or argon.

[0105] A method of manufacturing a positive electrode active material according to another embodiment of the present disclosure may differ from the above-described method of manufacturing a positive electrode active material in that no additional steps are performed after step S410 of separating the current collector component from the positive electrode active material component.

[0106] A rechargeable lithium battery according to another embodiment of the present disclosure may include a positive electrode active material obtained by the manufacturing method.

[0107] A rechargeable lithium battery according to another embodiment of the present disclosure may include a positive electrode including a positive electrode active material obtained by the manufacturing method; a negative electrode including a negative electrode active material; and an electrolyte.

[0108] The method for manufacturing a rechargeable lithium battery may be as follows: The positive electrode active material obtained by the manufacturing method may be used alone or mixed with a fresh positive electrode active material so as to be recycled when manufacturing a positive electrode.

[0109] In an embodiment, the positive electrode active material, the conductive material, and the binder obtained by the manufacturing method may be mixed and added to a solvent (such as N-methyl-2-pyrrolidone (NMP)), and then mixed to prepare a positive electrode slurry. The prepared positive electrode slurry may be coated on a current collector and dried to prepare a positive electrode for recycling. Finally, a separator may be inserted between the recycled positive electrode and the negative electrode, and an electrolyte may be introduced to manufacture a rechargeable lithium battery.

[0110] The following description will focus on some embodiments of the present disclosure. The embodiments discussed below are merely exemplary to help understand the present disclosure, and it should be understood that the scope of the present disclosure is not limited thereto.

[0111] Positive electrode active materials were manufactured by the following embodiments and comparative examples.

[0112] Implementation Method 1

[0113] Lithium nickel cobalt aluminum oxide (NCA) positive electrode scrap generated during the manufacture of rechargeable lithium batteries was collected and then subjected to a first grinding step using a cutting pulverizer. After the first grinding step, the pulverized material had a width and length of approximately 1 cm or less. The positive electrode scrap consisted of positive electrode plates in which a positive electrode active material layer was roll-pressed onto an aluminum current collector, and the mixed density of the positive electrode plates was approximately 3.0 g / cc to 4.0 g / cc.

[0114] The pulverized material after the first grinding step was heat-treated at 500° C. for 2 hours under vacuum conditions.

[0115] The heat-treated pulverized material was subjected to a second grinding step using an impact mill.

[0116] The average particle size of the pulverized material after the second grinding step (D 50 ) is equal to or less than about 3 mm.

[0117] The pulverized material after the second grinding step was passed through a 500-mesh sieve to separate the positive electrode active material component from the current collector component, thereby recovering the positive electrode active material from the positive electrode scrap.

[0118] Implementation Method 2

[0119] The positive electrode active material powder recovered in Embodiment 1 was added to a reactor containing N-methyl-2-pyrrolidone (NMP) solvent and then ultrasonicated for 10 seconds. The ultrasonicated product was then added to a centrifuge and centrifuged at 2,000 rpm for 3 minutes.

[0120] The supernatant was decanted from the centrifugal separation result, and the precipitated powder of the positive electrode active material was dried at a temperature of 150° C. for 4 hours, and finally the positive electrode active material was recovered from the positive electrode scrap.

[0121] Embodiment 3 (reference embodiment)

[0122] The recovery of the powder of the positive electrode active material is performed in substantially the same manner as in the first embodiment, except that the second grinding step is not performed.

[0123] A method for recovering the positive electrode active material according to Embodiment 3 is described below.

[0124] Lithium nickel cobalt aluminum oxide (NCA) positive electrode scrap generated during the manufacture of rechargeable lithium batteries was collected and then subjected to a first grinding step using a cutting pulverizer. After the first grinding step, the width and length dimensions of the pulverized material were both equal to or less than about 1 cm.

[0125] The pulverized material after the first grinding step was heat treated at 500° C. for 2 hours under vacuum conditions.

[0126] The heat-treated pulverized material was passed through a 500-mesh sieve to separate the positive electrode active material component from the current collector component, thereby recovering powder of the positive electrode active material from the positive electrode scrap.

[0127] Embodiment 4 (reference embodiment)

[0128] The recovery of the positive electrode active material powder was carried out in basically the same manner as in the third embodiment, except that the powder was heat-treated at 400°C.

[0129] Embodiment 5 (reference embodiment)

[0130] The recovery of the positive electrode active material powder was carried out in basically the same manner as in the third embodiment, except that the powder was heat-treated at 450°C.

[0131] Comparative Example 1

[0132] The powder of the positive electrode active material is recovered in substantially the same manner as in Embodiment 1, except that neither the heat treatment step nor the second grinding step is performed.

[0133] A method of recovering the positive electrode active material according to Comparative Example 1 is described below.

[0134] Lithium nickel cobalt aluminum oxide (NCA) positive electrode scrap generated during the manufacture of rechargeable lithium batteries was collected and then subjected to a first grinding step using a cutting mill. After the first grinding step, the width and length of the pulverized material were both equal to or less than approximately 1 cm. The positive electrode scrap consisted of positive electrode plates in which a positive electrode active material layer was roll-pressed onto an aluminum current collector, and the mixed density of the positive electrode plates was approximately 3.0 g / cc to 4.0 g / cc.

[0135] The pulverized material after the first grinding step was passed through a 500-mesh sieve to separate the positive electrode active material component from the current collector component, thereby recovering the positive electrode active material from the positive electrode scrap.

[0136] Evaluation Example 1: Recovery Rate

[0137] Before performing the process of recovering the positive electrode active material from the positive electrode waste, the total weight of the collected positive electrode waste is measured. Additionally, the positive electrode waste is weighed to determine the weight of each of the positive electrode active material, conductive material, binder, and aluminum current collector contained therein. For example, the positive electrode waste can be pretreated to separate each component, and then the weight of each component can be measured. The weight of the aluminum current collector is obtained by multiplying the area of ​​the positive electrode waste by the density of the aluminum current collector.

[0138] The weight of the recovered positive electrode active material in the embodiments and comparative examples was measured, and the recovery rate was calculated and listed in Table 1 below. For example, with respect to the weight of the positive electrode active material included in the positive electrode waste before the recovery process, a method can be used to pre-treat the positive electrode waste to separate each component, and then measure the weight of the positive electrode active material included in the positive electrode waste. The recovery rate (E) is calculated according to the following equation 1.

[0139] [Equation 1]

[0140] Recovery rate (E) = (weight of recovered positive electrode active material / weight of positive electrode active material included in positive electrode waste before recovery process) × 100 (%)

[0141] Table 1

[0142]

[0143] Referring to Table 1, it was confirmed that, compared with Comparative Example 1, in the embodiment in which the first grinding step was followed by the heat treatment step at a temperature in the range of 400° C. to 600° C., the recovery rate was large.

[0144] In the present disclosure, when the heat treatment step is performed at a temperature of 700°C or higher, because the aluminum current collector has a melting point of 660.3°C, the current collector components may melt and be incorporated into the positive electrode active material. Therefore, compared to the embodiment, when the heat treatment step is performed at a temperature of 700°C or higher, the amount of current collector in the recovered positive electrode active material may be greater. This may adversely affect the electrochemical characteristics. Accordingly, in the present disclosure, the heat treatment step may be performed at a temperature equal to or lower than about 600°C.

[0145] In addition, the positive electrode active material of Embodiment 1 and Embodiment 2, in which the heat treatment step is followed by the second grinding step, achieved a higher positive electrode active material recovery rate than any other embodiment. In particular, it was determined that the recovery rate of the positive electrode active material was the highest in Embodiment 2, in which the second grinding step is followed by ultrasonic treatment.

[0146] Evaluation Example 2: Composition and particle size of recovered positive electrode active material

[0147] To determine the characteristics of the powder of the positive electrode active material recovered in Embodiment 2, field emission scanning electron microscopy (FE-SEM) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) were used to perform component analysis and particle size measurement.

[0148] It was determined that the positive electrode active material recovered in Embodiment 2 contained aluminum and carbon, each in an amount of 3 wt% or less relative to 100 wt% of the positive electrode active material. In addition, the positive electrode active material recovered in Embodiment 2 was measured to have an average particle size (D) equal to or less than about 20 μm. 50 ).

[0149] Evaluation Example 3: Battery Characteristics

[0150] The rechargeable lithium battery according to the embodiment is manufactured using the positive electrode active material recovered in embodiment 2. 94 wt% of the positive electrode active material of embodiment 2, 3 wt% of a polyvinylidene fluoride binder, and 3 wt% of a carbon black conductive material are mixed in an N-methyl-2-pyrrolidone (NMP) solvent to prepare a positive electrode active material slurry. An aluminum current collector having a thickness of 15 μm is coated with the positive electrode active material slurry, and the amount of the positive electrode active material slurry reaches 15 mg / cm 2 The current collector was then dried and roll-pressed to produce a lithium nickel cobalt aluminum oxide (NCA) positive electrode.

[0151] A 2032-type coin cell was fabricated using a positive electrode and a lithium metal counter electrode. A separator (having a thickness of approximately 16 μm) formed of a porous polyethylene (PE) film was inserted between the positive electrode and the lithium metal counter electrode, and an electrolyte was introduced to fabricate a rechargeable lithium battery. 1.3M LiPF6 was mixed with a solvent comprising ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) mixed in a volume ratio of 3:4:3, and the mixture was used as the electrolyte.

[0152] A rechargeable lithium battery (2016-type coin cell) according to a comparative example was manufactured using the same composition and manufacturing steps, except that unused fresh lithium nickel cobalt aluminum oxide (NCA) positive electrode active material was used instead of the recycled positive electrode active material.

[0153] The electrochemical properties of the rechargeable lithium batteries manufactured according to the embodiment and the comparative example were evaluated.

[0154] Each of the rechargeable lithium batteries was initially charged at 25° C. under constant current (0.2C) and constant voltage (4.3V) conditions, and after standing for 10 minutes, the rechargeable lithium battery was discharged under constant current (0.2C) until the voltage reached 3.0V to measure the discharge capacity as the initial discharge capacity, which is shown in Table 2 below. Thereafter, at 45° C., charging and discharging were repeated 50 times under 1.0C / 1.0C conditions (charging conditions were: CC-CV, 1.0C, 4.30V, and cut-off at 0.05CmA; and discharging conditions were: 1.0C, and cut-off at 3.0V.). Table 2 below and Figure 8 and Figure 9 The results of electrochemical performance evaluation are listed.

[0155] Figure 8 The graph shows the lifespan retention ratio (ie, discharge capacity retention ratio) of rechargeable lithium batteries manufactured according to the embodiment and the comparative example. The lifespan retention ratio means discharge capacity after each cycle / initial discharge capacity×100.

[0156] Figure 9 FIG. 1 is a graph showing measurement results of 0.2C formation capacity (ie, specific capacity) of rechargeable lithium batteries manufactured according to the embodiment and comparative examples.

[0157] Table 2

[0158]

[0159] Refer to Table 2 and Figure 8 and Figure 9 , it can be determined that the comparative example and the embodiment show comparable performance results in terms of capacity and life retention.

[0160] In the method of manufacturing a positive electrode active material according to the present disclosure, the positive electrode active material may be efficiently recovered from positive electrode scrap generated during the manufacture of a rechargeable lithium battery.

[0161] Although some embodiments of the present disclosure have been discussed with reference to the accompanying drawings, it will be understood that various changes in form and details can be made therein without departing from the spirit and scope of the invention. Therefore, it will be understood that the above embodiments are only illustrative and not restrictive.

Claims

1. A method for producing a positive electrode active material, the method comprising: A first grinding step of grinding positive electrode waste of rechargeable lithium batteries; a step of heat-treating the ground positive electrode scrap; a second grinding step of grinding the heat-treated positive electrode scrap; separating a current collector component and an active material component from the positive electrode scrap ground in the second grinding step; washing the separated active substance components with a solvent; separating the washed active substance components into solid and liquid; and The solid was dried.

2. The method according to claim 1, wherein each of the first grinding step and the second grinding step uses at least one selected from a cutting mill, a shearing mill, a pin mill, an impact mill, a ball mill, and a sand mill.

3. The method according to claim 1, wherein the positive electrode scrap after the first grinding step has an average particle size D of 0.1 cm to 1 cm. 50 . 4 . The method according to claim 1 , wherein the heat treatment is performed at 400° C. to 600° C. under vacuum conditions for 30 minutes to 3 hours.

5. The method according to claim 1, wherein the positive electrode scrap after the second grinding step has an average particle size D of 1 mm to 3 mm. 50 . 6 . The method of claim 1 , wherein separating the current collector component from the active material component comprises using a sieve having a mesh size ranging from 100 mesh to 1,000 mesh.

7. The method of claim 1, wherein the current collector component comprises aluminum, and the amount of aluminum in the dried solid is in a range of 0.001 wt% to 3 wt% based on the total weight of the dried solid.

8. The method according to claim 7, wherein the positive electrode active material in the dried solid has an average particle size D of 1 μm to 20 μm. 50 . 9 . The method according to claim 1 , wherein washing the separated active substance components comprises performing ultrasonic treatment for 10 seconds to 100 seconds.

10. The method according to claim 1, wherein the solvent comprises at least one of water, N-methyl-2-pyrrolidone, isopropyl alcohol, dimethyl sulfoxide, dimethylformamide, N-cyclohexyl-2-pyrrolidone, ethanol, methanol, acetone, chlorobenzene and dichlorobenzene. 11 . The method according to claim 1 , wherein separating the washed active substance component into the solid and the liquid comprises performing centrifugal separation at 1,000 rpm to 5,000 rpm for 1 minute to 20 minutes.

12. The method according to claim 1, wherein drying the solid is performed at 120°C to 180°C for 2 hours to 24 hours.

13. A method for producing a positive electrode active material, the method comprising: A first grinding step of grinding positive electrode waste of rechargeable lithium batteries; a heat treatment step of heat-treating the ground positive electrode scrap at a temperature of 400° C. to 600° C.; a second grinding step of grinding the heat-treated positive electrode scrap; as well as A current collector component and an active material component from the positive electrode scrap ground in the second grinding step are separated.

14. The method according to claim 13, wherein each of the first grinding step and the second grinding step uses at least one selected from a cutting mill, a shearing mill, a pin mill, an impact mill, a ball mill, and a sand mill.

15. The method according to claim 13, wherein the positive electrode scrap after the first grinding step has an average particle size D of 0.1 cm to 1 cm. 50 .

16. The method according to claim 13, wherein the positive electrode scrap after the second grinding step has an average particle size D of 1 mm to 3 mm. 50 . 17 . The method of claim 13 , wherein separating the current collector component from the active material component comprises using a sieve having a mesh size ranging from 100 mesh to 1,000 mesh. 18 . The method of claim 13 , wherein the current collector component comprises aluminum, and an amount of aluminum in the separated active material component is in a range of 0.001 wt % to 3 wt % based on the total weight of the separated active material component.

19. The method according to claim 18, wherein the positive electrode active material in the separated active material components has an average particle size D of 1 μm to 20 μm. 50 .

20. A rechargeable lithium battery comprising: A positive electrode comprising a positive electrode active material manufactured by the method according to any one of claims 1 to 19; a negative electrode, including a negative electrode active material; as well as electrolyte, Wherein, based on the total weight of the positive electrode active material, the amount of aluminum in the positive electrode active material is in the range of 0.001 wt % to 3 wt %.

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