Separation method and separation device

Abstract

This separation method comprises a separation step for subjecting an electrode of interest including a current collector and an electrode mixture formed on the current collector to ultrasonic treatment in a treatment liquid while sweeping the frequency of ultrasonic waves to separate the current collector from the electrode mixture. In the separation step, the ultrasonic treatment is performed under a condition satisfying the following (1) and / or (2). (1) The electrode of interest is subjected to ultrasonic treatment in a degassed treatment liquid. (2) The electrode of interest is subjected to ultrasonic treatment in a degassed ultrasonic medium liquid together with a treatment tank accommodating the electrode of interest and the treatment liquid.

Description

Separation method and separation apparatus

[0001] This disclosure relates to a separation method and a separation apparatus.

[0002] Conventionally, in the recycling of electrodes, a method has been proposed to separate the current collector and the electrode composite by ultrasonic treatment while sweeping the ultrasonic frequency over the electrode in water (see, for example, Patent Document 1). This method utilizes a physical action using the cavitation effect of ultrasound, rather than the chemical action of organic solvents or aqueous solutions. It is claimed that by using water and sweeping the ultrasonic frequency, the current collector and the electrode composite can be separated efficiently and with high precision. Furthermore, regarding ultrasonic cleaning, it is known that the cleaning effect is good when the dissolved oxygen amount is in the range of 2 to 4 mg / L (see, for example, Non-Patent Document 1), and that to increase the efficiency of cavitation generation, it is highly effective to degas the dissolved gas amount to approximately half of the saturation amount (see, for example, Non-Patent Document 2).

[0003] Japanese Patent Publication No. 2023-102744

[0004] Otari Corporation, Recommendation for Ultrasonic Cleaning and Degassing - Differences between using and not using a degassing device - (https: / / otari-datuki.access21-co.jp / 006.html) NEW GLASS Vol. 33 No. 123 2018 (https: / / www.newglass.jp / mag / TITL / maghtml / 123-pdf / +123-p031.pdf)

[0005] However, when the technology described in Patent Document 1 is applied to electrodes equipped with thick-film electrode composites or high-density electrode composites, the separation efficiency may decrease, and there has been a desire to further improve the separation efficiency. Furthermore, Non-Patent Document 1 examines ultrasonic cleaning of oil-based markers applied to frosted glass, and Non-Patent Document 2 examines aluminum foil damage due to cavitation, but the separation of the current collector and the electrode composite has not been examined.

[0006] This disclosure was made to solve these problems, and its main objective is to provide a separation method and apparatus that can efficiently separate the current collector and the electrode mixture.

[0007] To achieve the above-mentioned objectives, the inventors conducted diligent research. They discovered that by performing ultrasonic treatment on the electrode to be treated, either in a degassed treatment solution or in a degassed ultrasonic medium solution, while sweeping the ultrasonic frequency, the current collector and the electrode composite can be efficiently separated, leading to the completion of this disclosure.

[0008] In other words, the separation method of the present disclosure includes a separation step of separating the current collector and the electrode mixture by ultrasonically treating an electrode to be treated, which comprises a current collector and an electrode mixture formed on the current collector, in a treatment liquid while sweeping the frequency of the ultrasound, wherein the ultrasonic treatment is performed under conditions that satisfy one or more of the following (1) and (2): (1) The electrode to be treated is ultrasonically treated in the degassed treatment liquid. (2) The electrode to be treated, together with the treatment tank containing the electrode and the treatment liquid, is ultrasonically treated in a degassed ultrasonic medium liquid.

[0009] Furthermore, the separation apparatus of the present disclosure comprises: a separation unit that ultrasonically treats an electrode to be treated, which comprises a current collector and an electrode mixture formed on the current collector, in a processing liquid to separate the current collector and the electrode mixture; and a control unit that controls the separation unit to perform the ultrasonic treatment while sweeping the ultrasonic frequency, wherein the separation unit performs the ultrasonic treatment under conditions that satisfy one or more of the following (1) and (2): (1) The electrode to be treated is ultrasonically treated in the degassed processing liquid. (2) The electrode to be treated is ultrasonically treated together with the processing tank containing the electrode and the processing liquid in a degassed ultrasonic medium liquid.

[0010] The separation method and apparatus of this disclosure can efficiently separate the current collector and the electrode mixture. The reasons for achieving such an effect are presumed to be as follows: This separation method and apparatus separates the current collector and the electrode mixture by utilizing the physical action of ultrasonic cavitation. It is presumed that by using a degassed processing liquid or ultrasonic medium liquid, large bubbles that hinder the cavitation effect and its transmission are removed, and the energy distribution within the electrode mixture and at the interface between the electrode mixture and the current collector becomes favorable, so that the cavitation effect is favorably expressed not only on the electrode surface but also within the electrode mixture and at the interface between the electrode mixture and the current collector. Furthermore, it is presumed that the energy distribution becomes even more favorable by performing ultrasonic processing while sweeping the ultrasonic frequency.

[0011] Diagrams illustrating the sweep and sweep cycle. Diagram illustrating the sweep width. Diagram showing a schematic of the configuration of the separation device 10 before ultrasonic treatment. Diagram showing a schematic of the configuration of the separation device 10 after ultrasonic treatment. Graph showing the peeling time as a function of dissolved oxygen in the inner tank. Graph showing the peeling rate per minute as a function of dissolved oxygen in the inner tank. Graph showing the peeling rate of the asphalt mixture as a function of ultrasonic treatment time when the ultrasonic frequency and output are changed.

[0012] [Separation Method] The separation method of this disclosure includes a separation step of separating the current collector and the electrode composite material by ultrasonically treating the electrode to be treated in a treatment liquid.

[0013] (Electrode to be processed) The electrode to be processed comprises a current collector and an electrode composite formed on the current collector. The electrode to be processed is an electrode in an ion secondary battery such as a lithium-ion secondary battery, or in an energy storage device such as an electric double-layer capacitor, hybrid capacitor, or pseudo-electric double-layer capacitor, and may be taken from a used or degraded energy storage device. The electrode to be processed may be a positive electrode, a negative electrode, or a bipolar electrode in which a positive electrode composite is formed on one side and a negative electrode composite is formed on the other side. The electrode to be processed may be one that has been taken from an energy storage device and has not been shredded, for example, with an area of ​​10 cm². 2 The above is also acceptable, 30 cm 2 The above may also be used.

[0014] Examples of materials for the current collector include aluminum, copper, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymers, and conductive glass. Among these, when the electrode to be treated is a positive electrode, the current collector preferably contains aluminum. Examples of the shape of the current collector include foil, film, sheet, net, punched or expanded bodies, lath bodies, porous bodies, foamed bodies, and formed bodies of fiber groups. The thickness of the current collector is, for example, 1 to 500 µm. The thickness of the current collector may be, for example, 35 µm or less, 30 µm or less, or 20 µm or less.

[0015] The electrode mixture may contain an electrode active material, a binder, and optionally a conductive material, etc. The electrode mixture may be formed, for example, by mixing an electrode active material, a conductive material, and a binder, adding an appropriate solvent to prepare a paste, applying the paste onto the surface of a current collector, drying the paste, and compressing it to increase the electrode density as necessary. The electrode mixture may be formed on one side or both sides of the current collector. The thickness of the electrode mixture (electrode mixture layer) may be, for example, less than 300 µm, 200 µm or less, or 100 µm or less. The thickness of the electrode mixture may be, for example, 20 µm or more, 30 µm or more, or 50 µm or more. The basis weight of the electrode mixture is, for example, 40 mg / cm 2 or less, or 30 mg / cm 2 or less. The basis weight of the electrode mixture may be, for example, 10 mg / cm 2 or more, or 15 mg / cm 2 or more.

[0016] Examples of the electrode active material contained in the electrode mixture include transition metal sulfides such as TiS₂, TiS₃, MoS₃, and FeS₂, and lithium manganese composite oxides having a basic composition formula of Li (1-x) ₓMnO₂ (where 0<x<1, the same applies hereinafter) or Li (1-x) ₓMn₂O₄, lithium cobalt composite oxides having a basic composition formula of Li (1-x) ₓCoO₂, lithium nickel composite oxides having a basic composition formula of Li (1-x) ₓNiO₂, lithium nickel composite oxides having a basic composition formula of Li (1-x) Nia Co b Mn c Examples of active materials used in the positive electrode of lithium-ion secondary batteries include lithium nickel cobalt manganese composite oxide with a basic composition formula such as O2 (a + b + c = 1), lithium vanadium composite oxide with a basic composition formula such as LiV2O3, transition metal oxide with a basic composition formula such as V2O5, and lithium iron phosphate with a basic composition formula such as LiFePO4. Note that "basic composition formula" means that other elements such as Al and Mg may also be included. Examples of electrode active materials include activated carbon, coke, glassy carbon, graphite, non-graphitizable carbon, pyrolytic carbon, carbon fibers, carbon nanotubes, and polyacenes, which are used in the positive and / or negative electrodes of capacitors and lithium-ion capacitors. Examples of electrode active materials include inorganic compounds such as lithium alloys and tin compounds, carbonaceous materials capable of intercalating and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers, which are used in the negative electrode of lithium-ion secondary batteries. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Examples of composite oxides include lithium titanium composite oxide and lithium vanadium composite oxide. Examples of conductive materials included in electrode mixture 54 include graphite such as natural graphite (scaly graphite, flake graphite) and artificial graphite, acetylene black, carbon black, Ketjenblack, carbon whiskers, needle coke, carbon fibers, and metals (copper, nickel, aluminum, silver, gold, etc.).

[0017] The binder contained in the electrode mixture plays the role of binding the active material particles and conductive material particles together. It may be an organic binder used by dissolving it in an organic solvent, an aqueous binder used by dissolving it in an aqueous solvent, or a mixture thereof. Examples of organic binders include fluororesins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber, or thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). Examples of aqueous binders include polyvinyl alcohol (PVA), styrene-butadiene copolymer (SBR), and polyethylene oxide (PEO), and may also contain carboxymethylcellulose (CMC). Examples of organic solvents include N-methylpyrrolidone, dimethylformamide, dimethylacetamide, methyl ethyl ketone, cyclohexanone, methyl acetate, methyl acrylate, diethylenetriamine, N,N-dimethylaminopropylamine, ethylene oxide, and tetrahydrofuran. Examples of aqueous solvents include water and various aqueous solutions.

[0018] The conductive material included in the electrode composite can be, for example, a mixture of one or more of the following: graphite such as natural graphite (scaly graphite, flake graphite) or artificial graphite, acetylene black, carbon black, Ketjen black, carbon whiskers, needle coke, carbon fiber, or metals (copper, nickel, aluminum, silver, gold, etc.). Among these, carbon black and acetylene black are preferred as conductive materials from the viewpoint of electronic conductivity and coating properties.

[0019] (Separation Process) In the separation process, the electrode to be treated is subjected to ultrasonic treatment in a treatment solution to separate the current collector and the electrode composite material. The treatment solution used in the separation process may be an aqueous solution such as an aqueous solution or water, or an organic treatment solution such as a solution containing an organic solvent or an organic solvent. From the viewpoint of improving the cavitation effect of ultrasound and reducing environmental impact, it is preferable to use an aqueous treatment solution, and water is preferable.

[0020] In the separation process, ultrasonic treatment is performed under conditions that satisfy one or more of the following (1) and (2): (1) The electrode to be treated is ultrasonically treated in a degassed treatment solution. (2) The electrode to be treated, together with the treatment tank containing the electrode and treatment solution, is ultrasonically treated in a degassed ultrasonic medium solution.

[0021] In the case of (1) above, for example, the electrode to be treated may be ultrasonically treated while immersed in a treatment tank which is an ultrasonic bath, containing a degassed treatment solution. Alternatively, in the case of (1) above, for example, the electrode to be treated may be ultrasonically treated together with the treatment tank, containing an ultrasonic medium solution, while immersed in this ultrasonic medium solution, containing the electrode to be treated and a treatment tank (inner tank) containing the degassed treatment solution. In this case, the ultrasonic medium solution contained in the outer tank may or may not be degassed.

[0022] In the case of (2) above, for example, the degassed ultrasonic medium liquid may be contained in the ultrasonic bath (outer tank), and the electrode to be treated and the treatment tank (inner tank) containing the treatment liquid may be immersed in this degassed ultrasonic medium liquid, and the electrode to be treated may be ultrasonically treated together with the treatment tank. In this case, the treatment liquid contained in the inner tank may or may not be degassed.

[0023] In the separation step, it is preferable to use a degassed treatment solution with a dissolved oxygen content of 7 ppm (mg / L) or less. The dissolved oxygen content of the treatment solution is more preferably 6 ppm or less, and may be 5 ppm or less. The dissolved oxygen content of the treatment solution may be, for example, more than 0.5 ppm, more than 1 ppm, more than 2 ppm, or more than 3 ppm. Furthermore, in this separation step, it is preferable to use a degassed treatment solution with a dissolved air content of 19.9 ppm or less. The dissolved air content of the treatment solution is more preferably 16.8 ppm or less, and may be 14 ppm or less. The dissolved air content of the treatment solution may be, for example, more than 1.4 ppm, more than 2.8 ppm, more than 5.6 ppm, or more than 8.4 ppm. Furthermore, if the amount of dissolved oxygen is x [ppm], the amount of dissolved air y [ppm] can be calculated using the formula y = x + (1.8x). The saturated dissolved oxygen content of water at 25°C is 8.25 ppm.

[0024] In the separation step, it is preferable to use an ultrasonic medium solution that has been degassed to a dissolved oxygen content of 7 ppm (mg / L) or less. The dissolved oxygen content of the ultrasonic medium solution is more preferably 6 ppm or less, and may be 5 ppm or less. The dissolved oxygen content of the ultrasonic medium solution may be, for example, more than 0.5 ppm or more than 1 ppm. In addition, in this separation step, it is preferable to use an ultrasonic medium solution that has been degassed to a dissolved air content of 19.9 ppm or less. The dissolved air content of the ultrasonic medium solution is more preferably 16.8 ppm or less, and may be 14 ppm or less. The dissolved air content of the ultrasonic medium solution may be, for example, more than 1.4 ppm or more than 2.8 ppm.

[0025] In the separation step, for example, ultrasonic treatment may be performed in a state where the treatment tank containing the electrode to be treated and the degassed treatment liquid is sealed. At this time, it is preferable that gas (such as air) inside the treatment tank is removed and the treatment tank is filled with the degassed treatment liquid. This can suppress the reintroduction of gases such as oxygen and air into the treatment liquid, and allows the dissolved oxygen content and dissolved air content of the treatment liquid to be maintained at desired values. Further, in this separation step, ultrasonic treatment may be performed while degassing the treatment liquid. This also allows the dissolved oxygen content and dissolved air content of the treatment liquid to be maintained at desired values.

[0026] In the separation step, ultrasonic treatment may be performed while degassing the ultrasonic medium liquid. This allows the dissolved oxygen content and dissolved air content of the ultrasonic medium liquid to be maintained at desired values. Further, in the separation step, ultrasonic treatment may be performed in a state where the outer tank containing the degassed ultrasonic medium liquid is sealed. At this time, it is preferable that gas (such as air) inside the outer tank is removed and the outer tank is filled with the degassed ultrasonic medium liquid. This also allows the dissolved oxygen content and dissolved air content of the ultrasonic medium liquid to be maintained at desired values.

[0027] In the separation step, ultrasonic treatment may be performed in a state where the pressure inside the treatment tank containing the electrode to be treated and the treatment liquid is reduced. This allows the treatment liquid to easily penetrate into the deep part of the electrode mixture, enabling more efficient separation of the current collector and the electrode mixture. In this case, prior to the separation step, a pressure reduction step of reducing the pressure inside the treatment tank containing the electrode to be treated and the treatment liquid may be performed. For the pressure reduction, for example, a vacuum pump may be used to reduce the pressure at a predetermined pressure for a predetermined period of time. For example, the pressure reduction may be performed at 0.05 MPa or less, or 0.03 MPa or less. For example, the pressure reduction may be performed at 0.005 MPa or more, or 0.01 MPa or more. For example, the pressure reduction may be performed until no more bubbles are generated from the electrode to be treated; for example, it may be performed for 10 seconds or more, 30 seconds or more, or 5 minutes or less, 3 minutes or less. It is preferable that the container after pressure reduction is filled with the treatment liquid and sealed in a state that does not contain air.

[0028] In the separation step, ultrasonic treatment is performed on the target electrode to be treated while sweeping the frequency of ultrasonic waves. Sweeping the frequency means, for example, periodically changing the frequency as shown in FIGS. 1 and 2.

[0029] In the separation step, with the fundamental frequency F0 as the center, the maximum frequency F max and the minimum frequency F min the frequency of ultrasonic waves may be periodically changed to reciprocate between (see FIGS. 1 and 2). The fundamental frequency F0 may be, for example, 40 kHz or higher, or 60 kHz or higher. Further, the fundamental frequency may be, for example, 240 kHz or lower, or 200 kHz or lower. In the ultrasonic treatment, when the fluctuation range of the frequency centered on the fundamental frequency F0 is defined as the sweep width (see FIG. 2), the sweep width may be set to within ±5 kHz. That is, F max - F0 ≦ +5 kHz, F min - F0 ≧ -5 kHz may be satisfied. The sweep width may be within ±3 kHz, or within ±1 kHz. In the ultrasonic treatment, the minimum frequency F min from the rising edge of the wave that reaches the maximum frequency F max to the falling edge of the wave that reaches the maximum frequency is defined as one sweep cycle (see FIG. 1), and when the number of sweep cycles per second is defined as the sweep rate, the sweep rate may be 500 sweep cycles / second or more. The sweep rate may be 700 sweep cycles / second or more, or 1000 sweep cycles / second or more. Further, the sweep rate may be 2000 sweep cycles / second or less. Note that one sweep cycle is the minimum frequency F min from the rising edge of the wave that reaches the minimum frequency F min may be half of the period up to the rising edge of the next wave that reaches

[0030] In the separation step, the ultrasonic treatment is preferably performed within a range of 30 minutes or less, more preferably within 10 minutes or less, still more preferably within 300 seconds or less, and even more preferably within 180 seconds or less. In the separation step, the ultrasonic treatment may be performed for 1 second or longer, 5 seconds or longer, or 15 seconds or longer.

[0031] In the separation process, the contact area between the current collector and the electrode composite material is A [cm²]. 2 When the ultrasonic output (oscillator output) is B [W], the power density (power density) expressed as B / A is 100 W / cm². 2 The ultrasonic treatment may be performed as follows: Power density B / A is 60 W / cm². 2 The following is also acceptable: 30 W / cm² 2 The following may also be used: Power density B / A is 0.1 W / cm². 2 The above is also acceptable, 0.5 W / cm 2 You may leave it at that.

[0032] In the separation process, ultrasonic treatment is preferably performed in a non-heating environment. In the separation process, ultrasonic treatment may be performed in a temperature range of 0°C to 30°C, or in a temperature range of 15°C to 25°C.

[0033] After performing the separation process described above, the electrode mixture is removed from the current collector, and the removed electrode mixture dissolves and / or disperses in water or precipitates. In this way, after ultrasonic treatment, the current collector and the electrode mixture are separated, and the current collector and the electrode mixture-containing treatment liquid are obtained. Furthermore, because a degassed treatment liquid or ultrasonic medium liquid is used, the current collector and the electrode mixture can be separated efficiently.

[0034] Before the separation process, an extraction process may be performed to remove electrodes from the energy storage device. The electrodes removed in the extraction process can be used as is, without being shredded, or in a 10 cm² area. 2 The above, or an area of ​​30 cm² 2 The material may be cut into pieces as described above and used as the electrode to be processed.

[0035] After the separation step, a current collector processing step may be performed to wash and dry the current collectors separated in the separation step. The current collectors may be washed while running a washing solution over them, or by immersion in the washing solution. Water is preferred as the washing solution. The current collectors may be dried by forced air drying, heat drying, vacuum drying, barrel drying, spin drying, suction drying, infrared drying, or a combination thereof. After the separation step, an asphalt mixture processing step may be performed to filter and dry the electrode mixture from the asphalt mixture-containing processing liquid obtained in the separation step. In the asphalt mixture processing step, the electrode mixture may be washed during or after filtering. Water is preferred as the washing solution. The electrode mixture may be dried by forced air drying, heat drying, vacuum drying, barrel drying, spin drying, suction drying, infrared drying, or a combination thereof. In addition, in the asphalt mixture processing step, instead of filtering the electrode mixture, the electrode mixture may be separated from the asphalt mixture-containing processing liquid by solid-liquid separation methods such as centrifugal separation or evaporation to dryness.

[0036] The separation process, current collector processing process, and electrode mixture processing process may be carried out in batches or continuously. When the separation process and current collector processing process are carried out continuously, a roll-to-roll method may be used. When the separation process is carried out using a roll-to-roll method, the electrodes removed in the extraction process may be sequentially wound into rolls and used as the electrodes to be processed. Since current collectors and electrode mixtures are obtained by this separation method, this separation method is both a method for manufacturing current collectors and a method for manufacturing electrode mixtures.

[0037] [Separation device] The separation device of the present disclosure comprises a separation unit that separates the current collector and the electrode mixture by ultrasonically treating the electrode to be processed in a processing liquid, and a control unit that controls the separation unit. This separation device may perform the separation method described above, or it may apply the configuration and conditions described in the separation method described above.

[0038] The following describes a separation device 10 as an example. Figures 3 and 4 show schematic diagrams illustrating the configuration of the separation device 10. Figure 3 is a schematic diagram illustrating the configuration of the separation device 10 before ultrasonic treatment. Figure 4 is a schematic diagram illustrating the configuration of the separation device 10 after ultrasonic treatment. The separation device 10 comprises a separation unit 20 and a control unit 15. In this separation device 10, ultrasonic treatment is performed on a target electrode 50, which is equipped with a current collector 52 and an electrode mixture 54, to separate the current collector 52 and the electrode mixture 54. The target electrode 50, the current collector 52, and the electrode mixture 54 may be the same as the target electrode, current collector, and electrode mixture described in the separation method.

[0039] The separation unit 20 performs ultrasonic treatment on the electrode 50 to be treated in a treatment liquid 32. The separation unit 20 comprises a treatment container 22, a transducer 28, and an oscillator 30. The treatment container 22 houses the electrode 50 to be treated and the treatment liquid 32. The treatment container 22 comprises an inner tank 24 in which the electrode 50 to be treated is housed, a mounting base 25 on which the inner tank 24 is placed, and an outer tank 26 in which the inner tank 24 and the mounting base 25 are housed. The treatment liquid 32 is housed in the inner tank 24, and the ultrasonic medium liquid 36 is housed in the outer tank 26. The treatment liquid 32 is degassed to a predetermined dissolved oxygen level, for example, 7 ppm or less. The inner tank 24, which houses the electrode 50 to be treated and the degassed treatment liquid 32, is sealed with a lid 24a. Furthermore, the inner tank 24 is filled with degassed processing liquid 32 from which gas (air) inside the inner tank 24 has been removed. This prevents gases such as oxygen and air from being reabsorbed into the processing liquid 32, and allows the dissolved oxygen and dissolved air content of the processing liquid to be maintained at predetermined values. The ultrasonic medium liquid 36 plays a role in propagating ultrasonic waves together with the processing liquid 32. The ultrasonic medium liquid 36 is degassed by the ultrasonic medium liquid degasser 40 to a predetermined dissolved oxygen content, such as 7 ppm or less. The ultrasonic medium liquid degasser 40 is connected to the outer tank 26 and is configured to pump out the ultrasonic medium liquid 36 from the outer tank 26, degas it, and return it to the outer tank 26. This allows the dissolved oxygen and dissolved air content of the ultrasonic medium liquid 36 to be maintained at predetermined values ​​even when the ultrasonic medium liquid 36 is in contact with the atmosphere (air, etc.).

[0040] The transducer 28 is positioned to be in contact with the processing container 22. The oscillator 30 supplies power to the transducer 28 and causes it to oscillate. The oscillator 30 has a sweep function. The sweep function is a function that periodically changes the frequency, for example, as shown in Figures 1 and 2. The separation unit 20 is configured to sweep (periodically change) the frequency of the ultrasonic waves generated from the transducer 28 by using the sweep function of the oscillator 30.

[0041] The control unit 15 is configured as a microprocessor centered on a CPU, and in addition to the CPU, it includes a memory device and input / output ports (not shown). The control unit 15 is electrically connected to the oscillator 30 and is configured to control the oscillator 30 to perform ultrasonic processing while sweeping the ultrasonic frequency. The conditions for ultrasonic processing may be the same as those for the separation method described above. The control unit 15 is also electrically connected to the ultrasonic medium liquid degasser 40 and is configured to control the ultrasonic medium liquid degasser 40 to degas the ultrasonic medium liquid 36.

[0042] An example of the operation of processing the electrode 50 to be processed using the separation device 10 will be described. First, the degassed processing liquid 32 is placed in the inner tank 24 of the processing container 22, and the electrode 50 to be processed is immersed in the processing liquid 32. Next, with the inner tank 24 filled with the degassed processing liquid 32, the lid 24a is placed on and sealed. Then, the inner tank 24 is immersed in the ultrasonic medium liquid 36 contained in the outer tank 26 of the processing container 22. After that, the control unit 15 controls the ultrasonic medium liquid degasser 40 to degas the ultrasonic medium liquid 36. Once the ultrasonic medium liquid 36 has been degassed to the desired amount of dissolved oxygen, the control unit 15 continues degassing and controls the oscillator 30 to supply power to the transducer 28, causing the transducer 28 to oscillate. As a result, ultrasonic processing is performed on the electrode 50 to be processed in the processing liquid 32. During ultrasonic processing, the control unit 15 uses the sweep function of the oscillator 30 and controls the oscillator 30 to sweep the frequency under predetermined conditions. Furthermore, the control unit 15 controls the oscillator 30 to output power such that the output density B / A is a predetermined value. The control unit 15 also controls the oscillator 30 to perform ultrasonic processing for a predetermined time. Through this ultrasonic processing, the current collector 52 and the electrode composite material 54 of the electrode 50 to be processed are separated, and a composite material-containing processing liquid 33 containing the current collector 52 and the electrode composite material 54 is obtained.

[0043] The separation method and apparatus described above can efficiently separate the current collector and the electrode mixture. The reasons for this effect are presumed to be as follows: The separation method and apparatus described above utilize the physical action of ultrasonic cavitation to separate the current collector and the electrode mixture. It is presumed that by using a degassed processing liquid or ultrasonic medium liquid, large bubbles that hinder the cavitation effect and its transmission are removed, and the energy distribution within the electrode mixture and at the interface between the electrode mixture and the current collector becomes favorable, so that the cavitation effect is favorably expressed not only on the electrode surface but also within the electrode mixture and at the interface between the electrode mixture and the current collector. Furthermore, it is presumed that the energy distribution becomes even more favorable by performing ultrasonic processing while sweeping the ultrasonic frequency. In the above embodiment, it is preferable to use water as the processing liquid. Water has a high surface tension and generates a cavitation effect more easily than organic solvents, so it can efficiently separate the current collector and the electrode mixture. The separation method and apparatus described above utilize a physical action based on the cavitation effect of ultrasound, which allows for the separation of the current collector and the electrode mixture using water, regardless of whether the binder contained in the electrode mixture is aqueous or organic. Furthermore, using water as the treatment liquid offers advantages such as relatively low cost, easy removal of the treatment liquid from the separated current collector and electrode mixture, and easy disposal of waste liquid, resulting in a low environmental impact. In addition, in the embodiments described above, ultrasonic treatment is preferably performed in a non-heating environment. In this disclosure, the current collector and the electrode mixture can be separated even in a non-heating environment. It is presumed that in the case of porous electrode mixtures, the degassed treatment liquid seeps into the electrode mixture and the interface between the electrode mixture and the current collector while dissolving the air present in the mixture and at the interface. By using a degassed treatment liquid on the electrode to be treated, it is also expected that the amount of dissolved oxygen in the treatment liquid in the voids within the electrode mixture and at the interface between the electrode mixture and the current collector will be reduced.

[0044] It goes without saying that this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of this disclosure.

[0045] For example, in the embodiment described above, the separation device 10 is assumed to have an inner tank 24 filled with deaerated processing liquid 32, but there may be a small space in the inner tank 24 that is not filled with deaerated processing liquid 32.

[0046] For example, in the embodiment described above, the separation device 10 may have a processing liquid degasser (not shown) connected to the inner tank 24 for degassing the processing liquid in the inner tank 24. A control unit 15 may be electrically connected to the processing liquid degasser, and the control unit 15 may control the processing liquid degasser to pump out the processing liquid 32 from the inner tank 24, degas it, and return it to the inner tank 24. In that case, the lid 24a of the inner tank 24 may be omitted.

[0047] For example, in the embodiment described above, the separation device 10 may have a pressure reducing device (not shown) connected to the inner tank 24 to reduce the pressure inside the inner tank 24. A control unit 15 may be electrically connected to the pressure reducing device, and the control unit 15 may control the pressure reducing device to reduce the pressure inside the inner tank 24 prior to ultrasonic treatment. It is presumed that the pressure reduction improves the penetration of the treatment liquid into the electrode mixture and the interface between the electrode mixture and the current collector (for example, the penetration rate increases), thereby allowing the cavitation effect to be favorably expressed not only on the electrode surface but also within the electrode mixture and at the interface between the electrode mixture and the current collector.

[0048] For example, in the embodiment described above, the separation device 10 uses an inner tank 24 as a processing tank for containing the electrode 50 to be processed and the processing liquid 32, and ultrasonically processes the electrode 50 in the inner tank 24 via an ultrasonic medium liquid 36 contained in an outer tank 26 which is an ultrasonic bath. However, the device is not limited to this configuration. For example, the separation device 10 may directly contain the electrode 50 to be processed and the processing liquid 32 in an ultrasonic bath which serves as a processing tank, and ultrasonically process the electrode 50.

[0049] For example, in the embodiment described above, the separation device 10 may have a lid (not shown) that seals the outer tank 26. In that case, it is preferable that the outer tank 26 is filled with degassed ultrasonic medium liquid 36 from which the gas (air) inside the outer tank 26 has been removed, but there may be a small space inside the outer tank 26 that is not filled with degassed ultrasonic medium liquid 36. If the separation device 10 has a lid that seals the outer tank 26, the ultrasonic medium liquid degasser 40 of the separation device 10 may be omitted.

[0050] For example, in the embodiment described above, the separation device 10 uses degassed processing liquid 32 and ultrasonic medium liquid 36, but it is not limited to this. For example, degassed processing liquid 32 may be used only, in which case the ultrasonic medium liquid degasser 40 and other components for maintaining the dissolved oxygen content of the ultrasonic medium liquid 36 may be omitted. Alternatively, degassed ultrasonic medium liquid 36 may be used only, in which case the lid 24a of the inner tank 24 and other components for maintaining the dissolved oxygen content of the processing liquid 32 may be omitted.

[0051] For example, in the embodiment described above, the separation device 10 performs ultrasonic processing in a batch manner, but it may also perform ultrasonic processing in a continuous manner.

[0052] This disclosure may be as shown in any of the following [1] to [8]. [1] A separation method comprising a separation step of ultrasonically treating an electrode to be treated, which comprises a current collector and an electrode mixture formed on the current collector, in a processing liquid while sweeping the frequency of ultrasound to separate the current collector and the electrode mixture, wherein the ultrasonic treatment in the separation step is performed under conditions that satisfy one or more of the following (1) and (2): (1) The electrode to be treated is ultrasonically treated in the degassed processing liquid. (2) The electrode to be treated is ultrasonically treated together with the treatment tank containing the electrode and the processing liquid in a degassed ultrasonic medium liquid. [2] The separation method according to [1], wherein the ultrasonic treatment in the separation step is performed under conditions that satisfy one or more of the following: using the processing liquid which has been degassed to a dissolved oxygen content of 6 ppm or less, or using the ultrasonic medium liquid which has been degassed to a dissolved oxygen content of 6 ppm or less. [3] The separation method according to [1] or [2], wherein the ultrasonic treatment is performed in the separation step under the condition that one or more of the following conditions are met: water is used as the treatment liquid or water is used as the ultrasonic medium liquid. [4] The separation method according to any one of [1] to [3], wherein the electrode to be treated comprises the electrode composite material having a thickness of less than 300 μm. [5] The separation method according to any one of [1] to [4], wherein the ultrasonic treatment is performed in the separation step with the treatment tank containing the electrode to be treated and the degassed treatment liquid sealed. [6] The separation method according to any one of [1] to [5], wherein the ultrasonic treatment is performed in the separation step while degassing the ultrasonic medium liquid. [7] The separation method according to any one of [1] to [6], wherein the ultrasonic treatment is performed in the separation step under the condition that one or more of the following conditions (3) to (9) are met. (3) The ultrasonic treatment is performed in the separation step while sweeping the ultrasonic frequency around a fundamental frequency of 60 kHz or more and 200 kHz or less. (4) In the separation step, the contact area between the current collector and the electrode composite material is A [cm²]. 2 When the output of the ultrasound is B [W], the power density expressed as B / A is 100 W / cm². 2The ultrasonic treatment is performed as follows: (5) In the separation step, the ultrasonic treatment is performed while sweeping the ultrasonic frequency with a sweep width of ±3 kHz around the fundamental frequency. (6) In the separation step, the ultrasonic treatment is performed for a period of 10 minutes or less. (7) In the separation step, the ultrasonic treatment is performed while sweeping the ultrasonic frequency with a sweep rate of 500 sweep cycles / second or more. (8) In the separation step, the ultrasonic treatment is performed in a non-heated environment. (9) In the separation step, the ultrasonic treatment is performed in a batch or continuous manner. [8] Separation apparatus comprising: a separation unit that ultrasonically treats an electrode to be treated, comprising a current collector and an electrode composite formed on the current collector, in a processing liquid to separate the current collector and the electrode composite; and a control unit that controls the separation unit to perform the ultrasonic treatment while sweeping the ultrasonic frequency, wherein the separation unit performs the ultrasonic treatment under conditions that satisfy one or more of the following (1) and (2). (1) The electrode to be treated is subjected to ultrasonic treatment in the degassed treatment solution. (2) The electrode to be treated, together with the treatment tank containing the electrode and the treatment solution, is subjected to ultrasonic treatment in the degassed ultrasonic medium solution.

[0053] The following describes examples of implementing the separation method of this disclosure. Experimental Examples 2-12 and 14-30 correspond to the Examples, while Experimental Examples 1, 13, and 31-39 correspond to the Comparative Examples.

[0054] 1. Experimental Example A (Experimental Examples 1-20) [Preparation of the electrode to be treated] The following positive electrode was prepared as the electrode to be treated. Specifically, LiNi was used as the positive electrode active material. 0.5 Co 0.2 Mn 0.3 A positive electrode composite material containing 98% by mass of O2 (NCM) (manufactured by Toda Kogyo), 1% by mass of acetylene black (manufactured by Denka) as a conductive material, and 1% by mass of polyvinylidene fluoride (PVDF) (manufactured by Kureha) as a binder was coated on both sides of a 20 μm thick aluminum current collector foil to form the positive electrode. The basis weight of the positive electrode composite layer was 16 mg / cm² per side. 2 The thickness was 80 μm and the area was 20 mm x 50 mm.

[0055] [Ultrasonic Treatment] For ultrasonic treatment, an ultrasonic device (Branson GCX-M-3FQ12, output 500W, outer tank capacity 20L) was used. Specifically, as shown in Figures 3 and 4, the ultrasonic medium solution described later was placed in the washing tank (outer tank 26), 50 mL of the treatment solution described later was placed in the glass container (inner tank 24), and ultrasound was applied from the transducer 28 below the outer tank 26. The electrode 50 to be treated was immersed in this solution, and the time until the electrode composite layer was completely peeled off was measured visually. Alternatively, the electrode to be treated was removed after applying ultrasound for 1 minute, and the composite layer peeling rate was calculated from the weight before and after ultrasonic treatment. The conditions for ultrasonic treatment were a frequency of 80 kHz, an output of 500 W, a sweep width of ±1 kHz, and a sweep speed (sweep rate) of 1000 sweep cycles / second. The treatment solution was water, which was used as is or degassed using the degassing method (degassing of the inner tank) described below. The ultrasonic medium was water, which was used either as is or after being degassed using the degassing method described below (degassing of the outer tank).

[0056] [Degassing Method] <Degassing of the outer tank (ultrasonic medium liquid)> Using a degassing system (KAIJO WRS), 18 L of water in the outer tank of the ultrasonic device described above was degassed for 20 minutes. After sufficient degassing, ultrasonic treatment was performed while continuously degassing and circulating the water. Due to the circulating system, the dissolved oxygen content of the water in the outer tank was approximately 3 ppm when degassed and approximately 8 ppm when not degassed. Due to the circulating system, there are some fluctuations in the dissolved oxygen content. <Degassing of the inner tank (treatment liquid)> 1 L of water was degassed in a container using a vacuum pump at 0.001 MPa for more than 2 hours to produce sufficiently degassed water. The dissolved oxygen content was 1 ppm or less. This degassed water was filled to the brim in a 50 mL glass container (inner tank 24), the electrodes were immersed, and the container was sealed without air. Since the inside of the bottle does not come into contact with air, the same dissolved oxygen content as when the degassed water was added can be maintained. If the amount of dissolved oxygen in the inner tank needs to be changed, prepare saturated air water by bubbling 1 liter of water in a container for at least 2 hours. The saturated air water had a dissolved oxygen content of approximately 8.5 ppm at 25°C. The above deaerated water and saturated air water were mixed in predetermined amounts to prepare water (deaerated water) with a dissolved oxygen content between 1 ppm and 8.5 ppm. This was then poured into a 50 mL glass container (inner tank 24) to the fullest extent, as described above, and sealed to remove air.

[0057] [Measurement of Dissolved Oxygen] The amount of dissolved oxygen was measured using a dissolved oxygen measuring device (HORIBA D200). Before measurement, (1) DO zero solution (pure water with an excess of sodium sulfite added) and (2) DO air saturated solution (pure water with air bubbling) were prepared and used for calibration. The measurement was performed by measuring 100 ml of the sample solution while stirring it at 700 rpm. From the measured dissolved oxygen amount x [ppm], the amount of dissolved air [ppm] was calculated using the formula y = x + (1.8x). When oxygen was removed by N2 bubbling and then ultrasonic treatment was performed, there was no peeling effect. From this, it was inferred that what affects the peeling effect is not the amount of dissolved oxygen itself, but the amount of dissolved gas (usually about the same as the amount of dissolved air).

[0058] Table 1 summarizes the peeling time to complete removal for Experimental Examples 1 to 12, including whether or not the inner and outer tanks were degassed, the amount of dissolved oxygen and dissolved air in the inner tank, the amount of dissolved oxygen and dissolved air in the outer tank, and the peeling time. Figure 5 shows a graph of peeling time against the amount of dissolved oxygen in the inner tank. As shown in Table 1 and Figure 5, the order of peeling effect from highest to lowest was inner and outer tank degassing > inner tank degassing > outer tank degassing > no degassing. Compared to no degassing, degassing at least one of the processing liquid contained in the inner tank and the ultrasonic medium liquid contained in the outer tank resulted in a shorter peeling time and a better peeling effect. When only the inner tank was degassed, an oxygen concentration of 4 ppm resulted in the shortest peeling time and the highest peeling effect.

[0059] Table 2 summarizes the results for Experimental Examples 13-20, including whether or not the inner and outer tanks were degassed, the amount of dissolved oxygen and dissolved air in the inner tank, the amount of dissolved oxygen and dissolved air in the outer tank, and the asphalt peeling rate (1-minute peeling rate) after 1 minute of ultrasonic treatment. Figure 6 shows a graph of the 1-minute peeling rate as a function of the dissolved oxygen amount in the inner tank. As shown in Table 2 and Figure 6, the order of highest 1-minute peeling rate was inner and outer tank degassing > inner tank degassing > outer tank degassing > no degassing. This order was consistent with the peeling effect shown in Table 1 and Figure 5. Compared to no degassing, degassing at least one of the treatment liquid contained in the inner tank and the ultrasonic medium liquid contained in the outer tank resulted in a higher 1-minute peeling rate and a greater peeling effect.

[0060] 2. Experiment B (Experimental Examples 21-39) The same procedure as in Experimental Example A was followed, except that the ultrasonic treatment was performed as described below. [Ultrasonic Treatment] An ultrasonic device (Branson GCX-M-3FQ12, output 500W, outer tank capacity 20L) was used for the ultrasonic treatment. Specifically, as shown in Figures 3 and 4, the ultrasonic medium solution described later was placed in the washing tank (outer tank 26), 10 mL of the treatment solution described later was placed in the glass container (inner tank 24), and ultrasonic waves were applied from the transducer 28 below the outer tank 26. The electrode 50 to be treated was immersed in the solution, and after applying ultrasonic waves for a predetermined time, the electrode was removed, and the asphalt peeling rate was calculated from the weight before and after the ultrasonic treatment. The conditions for the ultrasonic treatment were: frequency 80, 120 kHz, output 250, 500 W, sweep width ±1 kHz, sweep speed (sweep rate) 1000 sweep cycles / second. Water was used as the treatment solution. The ultrasonic medium was water, used either as is or degassed using the degassing method described below (degassing of the outer tank). The dissolved oxygen content of the treatment solution was 8.5 ppm. The dissolved oxygen content of the ultrasonic medium was 8.5 ppm without degassing and 2.5 ppm with degassing.

[0061] Table 3 summarizes the results for experimental examples 21-39, including whether or not the inner and outer tanks were degassed, the ultrasonic frequency, ultrasonic output, processing time, and peeling rate. Figure 7 shows a graph of the asphalt peeling rate against ultrasonic processing time when the ultrasonic frequency and output were varied. At all frequencies and outputs, when comparing with and without degassing of the outer tank, the asphalt peeling rate was higher when degassing was performed. When comparing 80 kHz and 120 kHz, the peeling rate tended to be slightly higher at 120 kHz than at 80 kHz. In the case of normal ultrasonic treatment without degassing, the cavitation effect and peeling rate were higher at lower frequencies, but degassing the outer tank had the effect of improving the peeling rate even at a high frequency of 120 kHz.

[0062] Compared to Example A, Example B had less water in the inner tank for the same positive electrode area, resulting in a lower peeling rate and a longer peeling time. However, regardless of the experimental conditions, the improvement in the peeling effect due to degassing was confirmed.

[0063] From the above, it was found that by performing ultrasonic treatment using degassed water as at least one of the processing liquid and the ultrasonic medium liquid, the current collector and the electrode mixture can be efficiently separated.

[0064]

[0065]

[0066]

[0067] This application is based on the priority claim of Japanese Patent Application No. 2025-048201, filed on 24 March 2025, the entire contents of which are incorporated herein by reference.

[0068] This disclosure is applicable to the field of the battery industry.

[0069] 10 Separation device, 15 Control unit, 20 Separation unit, 22 Processing container, 24 Inner tank, 24a Lid, 25 Mounting platform, 26 Outer tank, 28 Transducer, 30 Oscillator, 32 Processing liquid, 33 Processing liquid containing composite material, 36 Ultrasonic medium liquid, 50 Electrode to be processed, 40 Ultrasonic medium liquid degassing device, 52 Current collector, 54 Electrode composite material.

Claims

1. A separation method comprising a separation step of ultrasonically treating an electrode to be treated, which comprises a current collector and an electrode composite formed on the current collector, in a treatment liquid while sweeping the frequency of the ultrasonic waves, thereby separating the current collector and the electrode composite, wherein the ultrasonic treatment in the separation step is performed under conditions that satisfy one or more of the following (1) and (2): (1) The electrode to be treated is ultrasonically treated in the degassed treatment liquid. (2) The electrode to be treated is ultrasonically treated together with the treatment tank containing the electrode and the treatment liquid in a degassed ultrasonic medium liquid.

2. The separation method according to claim 1, wherein the ultrasonic treatment is performed in the separation step under the condition that one or more of the following conditions are met: using the treatment liquid from which the dissolved oxygen content has been reduced to 6 ppm or less, or using the ultrasonic medium liquid from which the dissolved oxygen content has been reduced to 6 ppm or less.

3. The separation method according to claim 1 or 2, wherein the separation step is performed under conditions that satisfy one or more of the following: water is used as the processing liquid, or water is used as the ultrasonic medium.

4. The separation method according to claim 1 or 2, wherein the electrode to be processed comprises the electrode composite material with a thickness of less than 300 μm.

5. The separation method according to claim 1 or 2, wherein the ultrasonic treatment is performed in a sealed state in the treatment tank containing the electrode to be treated and the degassed treatment liquid during the separation step.

6. The separation method according to claim 1 or 2, wherein the ultrasonic treatment is performed while degassing the ultrasonic medium liquid during the separation step.

7. The separation method according to claim 1 or 2, wherein the ultrasonic treatment is performed in the separation step under conditions that satisfy one or more of the following (3) to (9): (3) In the separation step, the ultrasonic treatment is performed while sweeping the ultrasonic frequency around a fundamental frequency of 60 kHz or more and 200 kHz or less. (4) In the separation step, the contact area between the current collector and the electrode composite is A [cm] 2 When the output of the ultrasound is B [W], the power density expressed as B / A is 100 W / cm². 2 The ultrasonic treatment is performed as follows: (5) In the separation step, the ultrasonic treatment is performed while sweeping the ultrasonic frequency with a sweep width of ±3 kHz around the fundamental frequency. (6) In the separation step, the ultrasonic treatment is performed for a period of 10 minutes or less. (7) In the separation step, the ultrasonic treatment is performed while sweeping the ultrasonic frequency with a sweep rate of 500 sweep cycles / second or more. (8) In the separation step, the ultrasonic treatment is performed in a non-heated environment. (9) In the separation step, the ultrasonic treatment is performed in a batch or continuous manner.

8. Separation device comprising: a separation unit that ultrasonically treats an electrode to be treated, which comprises a current collector and an electrode composite formed on the current collector, in a processing liquid to separate the current collector and the electrode composite; and a control unit that controls the separation unit to perform the ultrasonic treatment while sweeping the ultrasonic frequency, wherein the separation unit performs the ultrasonic treatment under conditions that satisfy one or more of the following (1) and (2): (1) The electrode to be treated is ultrasonically treated in the degassed processing liquid. (2) The electrode to be treated and the processing tank containing the electrode and the processing liquid are ultrasonically treated in a degassed ultrasonic medium liquid.

Images