Method for recycling negative electrode material generated as process waste

Abstract

The present invention comprises: a current collector delamination step for separating a current collector from a negative electrode active material layer by treating, with an organic solvent, a negative electrode determined to be defective during a battery manufacturing process; and a drying step for removing the remaining aqueous solvent by performing heat treatment on the negative electrode active material layer separated from the current collector, and thus can effectively recycle electrode material determined as waste during the battery manufacturing process.

Description

Method for recycling cathode materials generated as process waste

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0029585, filed February 29, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a method for recycling negative electrode materials generated or determined as process waste during a battery manufacturing process.

[0003] End-of-life batteries (EOL-Batteries) are typically discarded. The process of disposing of batteries leads to the release of various hazardous substances and the loss of valuable metals. To address these issues, research is underway into technologies for recycling end-of-life batteries.

[0004] Meanwhile, anode material waste is generated in various forms during the battery manufacturing process. During the battery manufacturing process, electrodes and batteries are inspected in various ways. If the inspection results indicate a defect, the battery is typically discarded. Existing research has focused on technologies for recycling batteries that have reached the end of their useful life, and research on recycling anode materials generated as waste during battery manufacturing remains insufficient.

[0005] Therefore, there is a need for a technology that recycles cathode materials determined to be waste during the battery manufacturing process in an environmentally friendly and efficient manner.

[0006] In order to solve the problems of the prior art as described above, the present invention aims to provide a method for effectively recycling or reusing negative electrode materials determined as waste during the battery manufacturing process.

[0007] In order to solve the above-mentioned problem, in one embodiment, a method for recycling a negative electrode according to the present invention includes a current collector detachment step of treating a negative electrode determined to be defective during a battery manufacturing process with an aqueous solvent to separate a current collector and a negative electrode active material layer; and a drying step of performing a heat treatment on the negative electrode active material layer separated from the current collector to remove the aqueous solvent.

[0008] In a specific example, the aqueous solvent is water.

[0009] In one embodiment, the collector detachment step includes an immersion step of immersing the cathode in an aqueous solvent; and an ultrasonic application step of applying ultrasonic waves.

[0010] In one specific embodiment, the immersion step and the ultrasonic application step are performed together in a single process.

[0011] In one specific embodiment, the ultrasound application step is performed by applying ultrasound in the range of 20 to 200 KHz for 5 to 60 minutes.

[0012] In another embodiment, the drying step is performed at a temperature of 100 to 400°C for 1 to 30 hours.

[0013] Specifically, the drying step is performed under vacuum or reduced pressure conditions.

[0014] For example, the component obtained through the above drying step is a mixture of a negative electrode active material and a conductive material.

[0015] In one embodiment, the present invention includes a defect determination step for determining whether at least one of an electrode and a battery is defective during the battery manufacturing process, prior to the current collector detachment step.

[0016] The above-mentioned defective judgment step includes, when the battery is judged to be defective, a step of disassembling the outer case of the battery; a step of separating the electrode assembly into a positive electrode, a negative electrode, and a separator; and a step of washing the separated negative electrode.

[0017] For example, the battery to be recycled in the present invention is a lithium secondary battery, and specifically, a medium- to large-sized lithium secondary battery.

[0018] The present invention can effectively recycle or reuse negative electrode materials determined as waste during the battery manufacturing process.

[0019] Figure 1 is a schematic diagram showing the cross-sectional structure of a cylindrical battery.

[0020] Figure 2 is a flowchart of a cathode recycling process according to one embodiment of the present invention.

[0021] Figure 3 is a flowchart of a cathode recycling process according to another embodiment of the present invention.

[0022] Figure 4 is a flowchart of a cathode recycling process according to another embodiment of the present invention.

[0023] The present invention can be modified in various ways and has many embodiments, and specific embodiments will be described in detail in the detailed description.

[0024] However, this is not intended to limit the present invention to a specific embodiment, but should be understood to include all modifications, equivalents, or substitutes included in the spirit and technical scope of the present invention.

[0025] In the present invention, it should be understood that terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0026]

[0027] Hereinafter, the present invention will be described in more detail.

[0028]

[0029] The negative electrode recycling method according to the present invention includes a current collector detachment step of treating a negative electrode determined to be defective during the battery manufacturing process with an aqueous solvent to separate a current collector and a negative electrode active material layer; and a drying step of performing heat treatment on the negative electrode active material layer separated from the current collector to remove the aqueous solvent.

[0030] Specifically, in the process of manufacturing a secondary battery, a process of inspecting the electrode or battery is carried out for each process. The present invention provides a method for effectively recycling an anode classified as process waste. In the present invention, a current collector and an anode active material layer are separated using an organic solvent. Specifically, the anode is immersed in a storage tank containing an organic solvent. This dissolves the binder component dispersed within the anode active material layer, and separates the active material layer component from the current collector. In addition, when the separated anode active material layer is removed by drying to evaporate the solvent, only the solid component remains. For example, the remaining solid component is a mixture of the anode active material and a conductive agent.

[0031] The above-mentioned collector desorption step is intended to remove the binder component by immersing the negative electrode in an aqueous solvent. This is because an aqueous binder is primarily used in the manufacture of the negative electrode. Specifically, in the immersion step, the aqueous solvent is water, specifically distilled water. Furthermore, the immersion step can be performed at a temperature of 15 to 50°C, 15 to 30°C, or specifically 25°C.

[0032] In one embodiment, the collector detachment step includes an immersion step of immersing the cathode in an aqueous solvent; and an ultrasonic application step of applying ultrasonic waves.

[0033] The above immersion step can be performed by immersing the cathode in distilled water. At this time, the solid-liquid ratio can be adjusted to a ratio of 1 to 20 liters of distilled water per 1 kg of cathode.

[0034] The above-mentioned immersion step and the above-mentioned ultrasonic application step are performed together in a single process. In the present invention, the ultrasonic application step may be performed before or after the immersion step. From a process efficiency perspective, it has been experimentally confirmed that it is advantageous to perform the immersion step and the ultrasonic application step together in a single process.

[0035] The above ultrasound application step can be performed by applying ultrasound in the range of 20 to 200 KHz for 5 to 60 minutes. Specifically, the conditions for applying the ultrasound can be performed under the conditions of a frequency of 120 to 200 kHz and an output of 200 to 600 W. In addition, the ultrasound application time can be adjusted in the range of 5 to 60 minutes, 10 to 50 minutes, or 20 to 40 minutes. The ultrasound application time includes cases where ultrasound is applied intermittently or periodically as well as cases where ultrasound is applied continuously within the corresponding time.

[0036] It is also possible to perform a stirring step instead of the above-mentioned ultrasonic application step. However, applying ultrasonic waves is advantageous in terms of process efficiency and quality control. In some cases, the ultrasonic application step may include performing ultrasonic application and stirring simultaneously.

[0037] The present invention may further include a step of separating the negative electrode active material and the current collector after the above-described current collector detachment step. Since the binder remaining in the negative electrode has been removed, the negative electrode active material and the current collector can be separated by a physical method using a sieve or the like. When the sieve is used, the separation can be performed using a sieve having pores of a size that the negative electrode active material can pass through, for example, a sieve having pores of 20 to 100 μm.

[0038] The drying step can be performed at a temperature of 100 to 300°C for 1 to 30 hours. The drying step includes both a direct drying method using a heating wire or the like and an indirect drying method using hot air. For example, the drying step in the present invention can be performed by hot air drying. Specifically, the drying step in the present invention can be performed for 60 to 150 minutes by supplying hot air at a temperature range of 110 to 170°C. The conditions for performing the drying step in the present invention can be adjusted depending on the state of the electrode or battery. However, the present invention performs the drying step at a relatively low temperature range and does not require high-temperature heat treatment. This can reduce process costs and energy costs, and prevent deformation or loss of the negative electrode material during the recycling process.

[0039] The drying step is intended to remove any remaining moisture within the separated negative active material layer. By performing the drying step under reduced pressure or vacuum conditions, process efficiency can be enhanced. For example, the drying step is performed in a vacuum chamber.

[0040] In one example, the component obtained through the drying step is a mixture of a negative electrode active material and a conductive material. The negative electrode active material and the conductive material can be separated through an additional process. Alternatively, the negative electrode active material and the conductive material can be reused without being separated. The process of separating the negative electrode active material and the conductive material can be performed by physical methods. For example, particle size separation using a sieve can be used to separate the components. This method utilizes the difference in particle size between the active material particles and the conductive material particles to physically remove the conductive material particles.

[0041]

[0042] The present invention includes a defect determination step, prior to the current collector detachment step, for determining whether at least one of the electrode and the battery is defective during the battery manufacturing process. In the present invention, the defect determination step includes the entire process of manufacturing the electrode. After the defect determination step, the electrode or battery determined to be defective is subject to recycling. The electrode is specifically a negative electrode, and the electrode is specifically a lithium secondary battery.

[0043] In one embodiment, the defect determination step is a step for determining whether the electrode is defective. The electrode defect determination step includes, for example, a method for inspecting the presence of surface cracks through vision inspection, a method for inspecting the loading amount through weight measurement, etc.

[0044] In another embodiment, the defect determination step is a step for determining whether the electrode assembly is defective. For example, in the case of a pouch-type battery, this includes a method for performing a vision inspection to determine whether there is a mismatch in the laminated structure of the negative electrode, separator, and negative electrode. Alternatively, in the case of a cylindrical or prismatic battery, this includes a method for performing a vision inspection of the winding state of a coiled jelly-roll electrode assembly.

[0045] In another embodiment, the defect determination step is a step for determining whether a battery is defective. Specifically, the step includes inspection for weld defects between the electrode tab and the electrode lead (including vision inspection, low voltage inspection, or ultrasonic application inspection), initial charge / discharge efficiency inspection, and battery life / efficiency inspection.

[0046] In one embodiment, the defectiveness determination step includes, if the battery is determined to be defective, the steps of disassembling the outer case of the battery; separating the electrode assembly into a cathode, an anode, and a separator; and washing the separated cathode.

[0047] If the battery is sealed, the outer case of the battery is removed. This can be done using a punch press or waterjet cutter. The electrode assembly can be separated into the cathode, anode, and separator, and then recycled or disposed of individually. The separated cathode is then washed to remove the electrolyte. Washing methods include, for example, using distilled water.

[0048]

[0049] The battery to be recycled in the present invention is a lithium secondary battery, and specifically, a medium- to large-sized lithium secondary battery. The lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a non-aqueous electrolyte that impregnates the electrode assembly; and an external case that houses the electrode assembly and the non-aqueous electrolyte.

[0050] The above positive electrode includes a positive electrode active material layer formed on a positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a binder, a conductive agent, and the like, and may further include a positive electrode additive commonly used in the art, if necessary.

[0051] The positive electrode active material may be a lithium-containing oxide, which may be the same or different. As the lithium-containing oxide, a lithium-containing transition metal oxide may be used.

[0052] For example, the lithium-containing transition metal oxide is Li x CoO2(0.5 <x<1.3), Li x NiO2(0.5 <x<1.3), Li x MnO2(0.5 <x<1.3), Li x Mn2O4(0.5 <x<1.3), Li x (Ni a Co b Mn c)O2(0.5 <x<1.3, 0<a<1, 0<b<1, 0<c<1, a+b+c=1), Li x Ni 1-y Co y O2(0.5 <x<1.3, 0<y<1), Li x Co 1-y Mn y O2(0.5 <x<1.3, 0≤y<1), Li x Ni 1-y Mn y O2(0.5 <x<1.3, O≤y<1), Li x (Ni a Co b Mn c )O4(0.5 <x<1.3, 0<a<2, 0<b<2, 0<c<2, a+b+c=2), Li x Mn 2-z Ni z O4(0.5 <x<1.3, 0<z<2), Li x Mn 2-z Co z O4(0.5 <x<1.3, 0<z<2), Li x CoPO4(0.5 <x<1.3) 및 Li x FePO4(0.5 <x<1.3)로 이루어진 군으로부터 선택되는 어느 하나 또는 이들 중 2종 이상의 혼합물일 수 있으며, 상기 리튬 함유 전이금속 산화물은 알루미늄(Al) 등의 금속이나 금속산화물로 코팅될 수도 있다. 또한, 상기 리튬 함유 전이금속 산화물 외에 황화물(sulfide), 셀렌화물(selenide) 및 할로겐화물(halide) 등도 사용될 수 있다.

[0053] The cathode according to the present invention can be applied to various types of lithium secondary batteries, but is preferably utilized in high-output batteries. The cathode active material layer of the present invention is applied to a high-nickel content (High-Ni) NCM battery.

[0054] In a specific example, the positive electrode active material layer according to the present invention includes an active material component having a structure represented by the following chemical formula 1.

[0055] [Chemical Formula 1]

[0056] Li x (Ni a Co b Mn c )O2

[0057] (0.5 <x<1.3, 0.3<a<1, 0<b<0.5, 0<c<0.5, a+b+c=1)

[0058] In the above chemical formula 1, the a value is greater than 0.3, 0.6 or more, and specifically, 0.8 or more. In the above chemical formula 1, when the a value increases, the b value and / or the c value decrease within a range satisfying the above chemical formula 1. Through this, the positive electrode for a lithium secondary battery according to the present invention is applied to a high-nickel content (High-Ni)-based NCM secondary battery. The NCM secondary battery is, for example, an NCM 622 or NCM 811 lithium secondary battery.

[0059] The current collector used for the positive electrode may be any metal with high conductivity, to which the positive electrode active material slurry can readily adhere, and which is non-reactive within the voltage range of the electrochemical device. Non-limiting examples of current collectors for the positive electrode include foils made of aluminum, nickel, or a combination thereof.

[0060] The above-mentioned positive electrode active material may be included in the positive electrode active material layer in a range of 94.0 to 98.5 wt%. When the content of the positive electrode active material satisfies the above range, it is advantageous in terms of manufacturing a high-capacity battery and providing sufficient positive electrode conductivity and inter-electrode material adhesion.

[0061] The binder used in the anode may be any binder commonly used in the art without limitation. For example, various types of binders such as poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, and polymethyl methacrylate may be used.

[0062] The conductive material used in the positive electrode is typically added in an amount of 1 to 10 wt% based on the total weight of the mixture including the positive electrode active material. There is no particular limitation on the conductive material as long as it is conductive and does not cause chemical changes in the secondary battery. For example, the conductive material may include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, and the like. For example, the conductive material may include at least one of carbon nanotubes and carbon black.

[0063]

[0064] The above negative electrode includes a negative electrode active material layer formed on a negative electrode current collector. The negative electrode active material layer includes a negative electrode active material, a binder, and a conductive agent, and may further include a negative electrode additive commonly used in the art, if necessary.

[0065] The negative active material may include carbon, lithium metal, silicon, or tin. When a carbon material is used as the negative active material, both low-crystalline carbon and high-crystalline carbon may be used. Representative low-crystalline carbons include soft carbon and hard carbon, and representative high-crystalline carbons include natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. As another example, the negative active material may include at least one of natural graphite and artificial graphite. For example, the negative active material may be manufactured by mixing 10 to 80 parts by weight of natural graphite and 20 to 90 parts by weight of artificial graphite. As another example, the negative electrode active material may further include silicon (Si). The content of the silicon (Si) may be in the range of 1 to 20 parts by weight or 3 to 16 parts by weight based on 100 parts by weight of the negative electrode active material. The silicon (Si) may be at least one of Si, SiOx (where x is an integer between 1 and 3), and SiC. In addition, the silicon (Si) includes a case where it has a carbon-coated structure.

[0066] For example, the negative active material layer may have a two-layer structure, the lower layer may have a composition including a mixture of natural graphite and artificial graphite, and the upper layer may have a composition including at least one type of graphite among artificial graphite and natural graphite and silicon (Si).

[0067] Non-limiting examples of current collectors used in the above negative electrode include foils made of copper, gold, nickel, or copper alloys, or combinations thereof.

[0068] Additionally, the cathode may include a conductive material and a binder commonly used in the field.

[0069] The binder used in the cathode may be any binder commonly used in the art without limitation. For example, various types of binders such as styrene-butadiene rubber (SBR) and carboxyl methyl cellulose (CMC) may be used.

[0070] The conductive material used in the negative electrode is typically added in an amount of 1 to 10 wt% based on the total weight of the mixture including the negative electrode active material. There is no particular limitation on the conductive material as long as it has conductivity and does not cause chemical changes in the secondary battery. For example, the conductive material may include graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or summer black; conductive fibers such as carbon fiber or metal fiber; metal powders such as fluorinated carbon, aluminum, or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; polyphenylene derivatives, and the like. For example, the conductive material may include at least one of carbon nanotubes and carbon black.

[0071] In the present invention, the separator may be any porous substrate used in a lithium secondary battery, and for example, a polyolefin porous membrane or non-woven fabric may be used, but is not particularly limited thereto.

[0072] Examples of the above polyolefin porous membrane include a membrane formed from a single or mixed polymer of polyolefin polymers such as polyethylene, polypropylene, polybutylene, polypentene, etc., such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene, and ultra-high molecular weight polyethylene.

[0073] The above nonwoven fabric may include, in addition to polyolefin-based nonwoven fabrics, nonwoven fabrics formed from polymers such as polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalene, either singly or in combination. The structure of the nonwoven fabric may be a spunbond nonwoven fabric composed of long fibers or a meltblown nonwoven fabric.

[0074] The thickness of the porous substrate is not particularly limited, but may be 5 to 50 μm, and the pore size and pore content present in the porous substrate are also not particularly limited, but may be 0.01 to 50 μm and 10 to 95%, respectively.

[0075] Meanwhile, in order to improve the mechanical strength of the separator composed of the porous substrate and to suppress short circuits between the anode and cathode, a porous coating layer including inorganic particles and a binder polymer may be further included on at least one side of the porous substrate.

[0076] In the present invention, the non-aqueous electrolyte may include an organic solvent and an electrolyte salt, and the electrolyte salt is a lithium salt. The lithium salt may be any of those commonly used in non-aqueous electrolytes for lithium secondary batteries without limitation. For example, the anion of the lithium salt may be F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may include one or two or more of the group consisting of:

[0077] As the organic solvent included in the non-aqueous electrolyte described above, those commonly used in non-aqueous electrolytes for lithium secondary batteries can be used without limitation, and for example, ethers, esters, amides, linear carbonates, cyclic carbonates, etc. can be used singly or in combination of two or more. Among these, representative examples include carbonate compounds that are cyclic carbonates, linear carbonates, or mixtures thereof.

[0078] The injection of the above non-aqueous electrolyte may be performed at an appropriate stage during the electrochemical device manufacturing process, depending on the final product's manufacturing process and required physical properties. That is, it may be applied prior to electrochemical device assembly or at the final stage of electrochemical device assembly.

[0079] Hereinafter, the present invention will be described in more detail with reference to drawings and the like. However, the drawings and the like are merely illustrative of the present invention, and the contents of the present invention are not limited thereto.

[0080]

[0081] Fig. 1 is a schematic diagram showing the cross-sectional structure of a cylindrical battery. Referring to Fig. 1, the cylindrical battery includes an electrode assembly having a structure in which a positive electrode (10), a negative electrode (20), and a separator (31, 32) are alternately laminated and wound in a cylindrical shape. A positive electrode tab (11) is formed on the upper end of the core of the electrode assembly, and a negative electrode tab (21) is formed on one side of the lower end of the electrode assembly. The electrode assembly is housed in a cylindrical battery case (40), and sealed by covering the upper end with a positive electrode cap while an electrolyte is injected.

[0082]

[0083] FIG. 2 is a flowchart illustrating a cathode recycling process according to one embodiment of the present invention. Referring to FIG. 2, first, a cathode inspection step (S110) is performed. In the cathode inspection step (S110), for example, a cathode that has gone through a drying process is inspected for surface cracks through a vision inspection. If the degree of surface cracks exceeds a standard, it is determined to be defective. Alternatively, in the cathode inspection step (S110), for example, a weight inspection of the cathode is performed to determine whether it is defective. If the cathode inspection step (S110) is determined to be normal, the cathode is transferred to the battery manufacturing process.

[0084] The cathode that is judged to be defective in the above cathode inspection step (S110) undergoes an immersion step (S121), which is a step of immersing the cathode in an aqueous solvent, i.e., distilled water. The immersion step (S121) is performed for 30 minutes under room temperature conditions.

[0085] Then, the cathode undergoes an ultrasonic application step (S122). The ultrasonic application step (S122) is performed for 15 minutes under conditions of a frequency of 160 kHz and an output of 400 W.

[0086] Through the above immersion step (S121) and the ultrasonic application step (S122), the SBR (styrene-butadiene rubber) binder present in the negative electrode is removed, and the current collector and the negative electrode active material layer are separated. The separated current collector goes through a separate current collector recycling process.

[0087] In addition, the separated active material components go through a hot air drying step (S130). The separated negative electrode active material layer has solid components separated by particle. The separated negative electrode active material layer goes through a hot air drying step (S130) in which hot air is supplied at 150°C to dry for 120 minutes. Through the hot air drying step (S130), any moisture remaining within the negative electrode active material layer is removed.

[0088]

[0089] Figure 3 is a flowchart illustrating a cathode recycling process according to another embodiment of the present invention. Referring to Figure 3, a cathode inspection step (S210) is performed. If the cathode inspection step (S210) is determined to be normal, the cathode is transferred to the battery manufacturing process.

[0090] The cathode that is judged to be defective in the above cathode inspection step (S210) undergoes a current collector detachment step (S220). The current collector detachment step (S220) is performed by applying ultrasonic waves while the target cathode is immersed in distilled water. The current collector detachment step (S220) is performed for 20 minutes at room temperature. The ultrasonic application is performed under conditions of a frequency of 160 kHz and an output of 400 W.

[0091] Through the above-mentioned current collector removal step (S220), the SBR binder present in the negative electrode is removed, and the current collector and the negative electrode active material layer are separated. The separated current collector then goes through a separate current collector recycling process.

[0092] Additionally, the separated active material components undergo a hot air drying step (S230). The separated negative active material layer has solid components separated into particles. The separated negative active material layer undergoes a hot air drying step (S230) in which hot air is supplied at 150°C for 120 minutes.

[0093]

[0094] FIG. 4 is a flowchart illustrating a cathode recycling process according to another embodiment of the present invention. Referring to FIG. 4, a battery inspection step (S310) is performed on a battery that has been manufactured or is in the manufacturing process. The battery inspection step (S310) inspects, for example, whether welding between an electrode tab and an electrode lead has been performed normally. In this case, the battery inspection step (S310) may be performed through a visual inspection, a vision inspection, or a low-voltage inspection. Alternatively, the battery inspection step (S310) may be performed through, for example, a visual inspection for electrolyte leakage in the battery, an initial charge / discharge inspection, a battery efficiency inspection, or a cycle characteristic inspection to determine whether the battery satisfies the criteria and determine whether it is defective. If the battery inspection step (S310) determines that the battery is normal, the battery is transferred to the next step for shipment.

[0095] Batteries judged to be defective are subjected to an outer case disassembly step (S311), if necessary. This outer case disassembly step (S311) can be performed using a punching press or a water jet cutter. After the outer case disassembly step (S311), the negative electrode is separated from the electrode assembly. The separated negative electrode then undergoes an electrolyte removal step (S312). This electrolyte removal step (S312) can be performed, for example, by washing with distilled water.

[0096] The negative electrode from which the electrolyte has been removed undergoes a current collector detachment step (S220). The current collector detachment step (S320) is performed by applying ultrasonic waves while the target negative electrode is immersed in distilled water. The current collector detachment step (S320) is performed for 20 minutes at room temperature. The ultrasonic application is performed at a frequency of 160 kHz and an output of 400 W.

[0097] Through the above-mentioned current collector removal step (S320), the SBR binder present in the negative electrode is removed, and the current collector and the negative electrode active material layer are separated. The separated current collector goes through a separate current collector recycling process.

[0098] Additionally, the separated active material components undergo a hot air drying step (S330). The separated negative active material layer is in a state where the solid components are separated into particles. The separated negative active material layer undergoes a hot air drying step (S330) in which hot air is supplied at 150°C for 120 minutes.

[0099]

[0100] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that various modifications and changes to the present invention can be made without departing from the spirit and technical scope of the present invention as set forth in the claims to be described below.

[0101] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the patent claims.

[0102]

[0103] [Explanation of symbols]

[0104] 10: Bipolar

[0105] 11: Positive tab

[0106] 20: Cathode

[0107] 21: Negative tab

[0108] 31, 32: Membrane

[0109] 40: Battery case

Claims

1. A current collector detachment step in which a negative electrode that has been determined to be defective during the battery manufacturing process is treated with an aqueous solvent to separate the current collector and the negative electrode active material layer; and A method for recycling a negative electrode, comprising a drying step of removing an aqueous solvent by performing heat treatment on a negative electrode active material layer separated from a current collector.

2. In paragraph 1, A cathode recycling method characterized in that the aqueous solvent is water.

3. In paragraph 1, The above-mentioned full-body detachment step is: An immersion step of immersing the cathode in an aqueous solvent; and A cathode recycling method comprising an ultrasonic application step of applying ultrasonic waves.

4. In paragraph 3, The above immersion step and the above ultrasonic application step are, A cathode recycling method characterized in that it is performed together in a single process.

5. In paragraph 3, The above ultrasonic application step is, A cathode recycling method characterized in that it is performed by applying ultrasonic waves in the range of 20 to 200 KHz for 5 to 60 minutes.

6. In paragraph 1, The above drying step is, A cathode recycling method characterized in that it is performed for 1 to 30 hours under temperature conditions of 100 to 400℃.

7. In paragraph 6, The above drying step is, A cathode recycling method characterized in that it is performed under vacuum or reduced pressure conditions.

8. In paragraph 1, The components obtained through the above drying step are: A method for recycling a cathode, characterized in that it is in a mixed state of a cathode active material and a conductive material.

9. In paragraph 1, Before the above-mentioned full-body detachment step, A cathode recycling method further comprising a defect determination step for determining whether at least one of an electrode and a battery is defective during the battery manufacturing process.

10. In paragraph 1, The above defect judgment step is: If the battery is judged to be defective, A step of disassembling the outer case for the above battery; A step of separating the electrode assembly into a positive electrode, a negative electrode, and a separator; and A cathode recycling method further comprising a step of washing the separated cathode.

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