Separation method, separation device, and method for manufacturing electrode mixture

Abstract

To improve processing efficiency when a process for separating a current collector and an electrode mixture is simultaneously performed on a plurality of electrodes.SOLUTION: A separation method includes a separation step of ultrasonically treating a target electrode having a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite, and in the separation step, ultrasonic treatment is performed by sweeping the frequency of ultrasonic waves while immersing multiple target electrodes in a treatment liquid, and maintaining the electrode spacing of the multiple target electrodes to be treated longer than half the wavelength of the fundamental frequency of the ultrasonic waves.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a separation method, a separation device, and a method for producing an electrode mixture. [Background technology]

[0002] Conventional methods for separating the current collector and the electrode composite in battery recycling include, for example, immersing small pieces of the battery in a polar solvent such as water, alcohol, or ketone, and mechanically agitating them by stirring or ultrasonic treatment for about 30 minutes to about 5 hours (Patent Document 1), or using an ultrasonic electrode with a power density of 50 W / cm on the front surface. 2 A method of ultrasonically treating an electrode sheet under the above conditions (Patent Document 2), a method of immersing a positive electrode in NMP at 50°C for 6 hours followed by ultrasonic treatment and scraping (Non-Patent Document 1), a method of using NMP as a cleaning solution for the positive electrode and performing ultrasonic treatment at 70°C and 240 W for 90 minutes (Non-Patent Document 2), and a method of crushing the electrode into pieces of 2 to 12 mm and then ultrasonically treating it at 40 Hz and 100 W (Non-Patent Document 3) have been proposed. However, the above-mentioned methods may damage the current collector even if the electrode mixture can be removed from the current collector, or may leave the electrode mixture on the current collector even if damage to the current collector is suppressed. This may result in contamination of the current collector components with the electrode mixture after separation, or contamination of the electrode mixture components with the current collector after separation. Furthermore, the treatment efficiency may be low due to the need for long treatment times or pretreatment such as crushing. Therefore, the present inventors have previously proposed to subject the electrode to ultrasonic treatment in water while sweeping the ultrasonic frequency (Patent Document 3). This method enables the current collector and the electrode composite to be separated efficiently and with high precision. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6828214 [Patent Document 2] International Publication No. 2021 / 152302 Brochure [Patent Document 3] Japanese Patent Application Publication No. 2023-102744 [Non-patent literature]

[0004] [Non-Patent Document 1] H. Gao et al., ACS Appl. Mater. Interfaces 12, 2020, 51546-51554. [Non-patent document 2] L.-P. He et al., Waste Management 46, 2015, 523-528. [Non-patent document 3] J. Li et al., Chemosphere 77, 2009, 1132-1136. Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the method of Patent Document 3 can efficiently separate the current collector and the electrode composite with high precision, it does not consider simultaneous processing of multiple electrodes, and there has been a demand for improving the processing efficiency when simultaneously processing multiple electrodes.

[0006] The present disclosure has been made to solve such problems, and its main object is to improve the processing efficiency when a process for separating a current collector and an electrode mixture is performed simultaneously on multiple electrodes. [Means for solving the problem]

[0007] As a result of intensive research to achieve the above-mentioned object, the inventors discovered that when processing multiple electrodes simultaneously, ultrasonic processing can be performed in an arrangement in which the distance between the electrodes is longer than half the wavelength of the ultrasonic waves, thereby further improving processing efficiency, and have completed the present disclosure.

[0008] That is, the separation method of the present disclosure includes: a separation step of ultrasonically treating a treatment target electrode including a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite, In the separation process, the ultrasonic frequency is swept while the plurality of electrodes to be treated are immersed in a treatment liquid, and the ultrasonic treatment is performed while maintaining the electrode spacing between the plurality of electrodes to be treated longer than half the wavelength at the fundamental frequency of the ultrasonic waves.

[0009] In addition, the separation device of the present disclosure includes: a separation unit that ultrasonically treats a target electrode including a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite; a control unit that controls the separating unit to sweep the frequency of ultrasonic waves while the plurality of electrodes to be treated are immersed in the treatment liquid, and to perform the ultrasonic treatment while maintaining the electrode spacing of the plurality of electrodes to be treated to be longer than half the wavelength of the fundamental frequency of the ultrasonic waves; It is equipped with the following.

[0010] Further, the method for producing an electrode mixture according to the present disclosure includes the steps of: a separation step of ultrasonically treating a treatment target electrode including a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite, In the separation step, the ultrasonic treatment is performed by sweeping the frequency of ultrasonic waves while the plurality of electrodes to be treated are immersed in the treatment liquid, and the electrode spacing between the plurality of electrodes to be treated is maintained so as to be longer than half the wavelength of the fundamental frequency of the ultrasonic waves; The separated electrode mixture is recovered to obtain the electrode mixture. [Effects of the Invention]

[0011] The separation method, separation device, and electrode composite manufacturing method disclosed herein can improve the processing efficiency when the process of separating the current collector and the electrode composite is performed simultaneously on multiple electrodes. The reason for this effect is presumed to be that, for example, by performing ultrasonic processing while maintaining the electrode distance longer than half the wavelength of the fundamental frequency of the ultrasonic waves, the ultrasonic waves act efficiently on the electrodes, thereby improving the processing efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is an explanatory diagram of a sweep and a sweep cycle. [Figure 2] An explanatory diagram of sweep width. [Figure 3] FIG. 2 is an explanatory diagram showing the relationship between the electrode spacing D and the half wavelength H of the ultrasonic wave. [Figure 4] FIG. 1 is an explanatory diagram showing an outline of the configuration of a separation device 10. [Figure 5] FIG. 2 is an explanatory diagram showing an outline of the configuration of an example of a jig 60. [Figure 6] Graph showing the relationship between the H / D value and the removal rate. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Separation method and electrode mixture manufacturing method] The separation method and the method for producing an electrode mixture according to the present disclosure include a separation step in which an electrode to be treated is subjected to ultrasonic treatment to separate the current collector and the electrode mixture.

[0014] (electrode to be treated) The electrode to be processed includes a current collector and an electrode mixture formed on the current collector. The electrode to be processed is an electrode of an ion secondary battery such as a lithium ion secondary battery, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, etc., and may be taken from a used or deteriorated power storage device. The electrode to be processed may be a positive electrode, a negative electrode, or a bipolar electrode with a positive electrode mixture formed on one surface and a negative electrode mixture formed on the other surface. The electrode to be processed may be left as it is taken out from the power storage device without being shredded. For example, it may have an area of 5 cm 2 or more, and may be 10 cm 2 or more, and may be 30 cm 2 or more.

[0015] Examples of the material of the current collector include aluminum, copper, titanium, stainless steel, nickel, iron, fired carbon, conductive polymer, conductive glass, etc. Among these, when the electrode to be processed is a positive electrode, it is preferable that the current collector contains aluminum. Examples of the shape of the current collector include foil shape, film shape, sheet shape, net shape, punched or expanded shape, lath body, porous body, foam body, formed body of fiber group, etc. The thickness of the current collector is, for example, 1 to 500 μm.

[0016] The electrode mixture may contain an electrode active material, a binder, and a conductive material as needed. 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 make it into a paste state, applying and drying it on the surface of the current collector, and compressing it as needed to increase the electrode density. The electrode mixture may be formed on one side or both sides of the current collector.

[0017] Examples of the electrode active material contained in the electrode mixture include transition metal sulfides such as TiS2, TiS3, MoS3, FeS2, etc., lithium manganese composite oxides with a basic composition formula of Li (1-x) MnO2 (0 < x < 1, etc., the same below) or Li (1-x) Mn2O4, etc., and basic composition formula of Li(1-x) Lithium cobalt composite oxides such as CoO2, with the basic composition formula Li (1-x) Lithium nickel composite oxide such as NiO2, the basic composition formula is Li (1-x) Ni a Co b Mn c Examples of active materials used in the positive electrodes of lithium-ion secondary batteries include lithium-nickel-cobalt-manganese composite oxides with a basic formula such as LiV2O3, transition metal oxides with a basic formula such as V2O5, and lithium iron phosphate. The term "basic formula" refers to materials that may contain other elements such as Al and Mg. Examples of electrode active materials include active materials used in the positive and / or negative electrodes of capacitors and lithium-ion capacitors, such as activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, and polyacenes. Examples of electrode active materials include inorganic compounds such as lithium alloys and tin compounds, carbonaceous materials capable of absorbing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers. 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 contained in the electrode mixture include graphite such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fibers, and metals (copper, nickel, aluminum, silver, gold, etc.).

[0018] The binder contained in the electrode mixture serves to bind the active material particles and the conductive material particles together. It may be an organic binder dissolved in an organic solvent, an aqueous binder dissolved in an aqueous solvent, or a mixture of these. Examples of organic binders include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber; 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 carboxymethyl cellulose (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. The conductive material contained in the electrode mixture can be, for example, one or a mixture of two or more of graphite, such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.). Among these, carbon black and acetylene black are preferred as the conductive material from the viewpoints of electronic conductivity and coatability.

[0019] (separation process) In the separation process, ultrasonic treatment is performed by swepting the frequency of ultrasonic waves while immersing multiple electrodes to be treated in a treatment liquid, and maintaining the electrode spacing between the multiple electrodes to be treated to be longer than half the wavelength of the fundamental frequency of the ultrasonic waves.

[0020] The treatment liquid used in ultrasonic treatment can be an aqueous treatment liquid such as water or an aqueous solution. Examples of water include tap water, distilled water, and ion-exchanged water. Examples of aqueous solutions include buffer solutions, acid solutions, and aqueous solutions containing water-soluble organic solvents. Examples of buffer solutions include acetate buffer solutions, citrate buffer solutions, phosphate buffer solutions, carbonate buffer solutions, carbonate / bicarbonate (bicarbonate) buffer solutions, citrate-phosphate buffer solutions, borate buffer solutions, and tartrate buffer solutions. Examples of salts contained in buffer solutions include lithium salts, sodium salts, and potassium salts. Examples of acids contained in acid solutions include carbonic acid, propionic acid, acetic acid, and benzoic acid. Examples of water-soluble organic solvents contained in aqueous solutions containing water-soluble organic solvents include ketones such as acetone, heterocyclic compounds such as N-methyl-2-pyrrolidone and 2-pyrrolidone, and amides such as N,N-dimethylformamide. It is preferable that the treatment liquid does not contain halogen compounds that cause pitting corrosion of aluminum. Examples of halogens include fluorine, chlorine, bromine, and iodine. The treatment liquid preferably has a low alkali metal ion concentration, from the viewpoint of suppressing the incorporation of impurities, and the alkali metal ion concentration may be, for example, 0.01 mol / L or less, or may be 0.001 mol / L or less. The treatment liquid preferably has a low halogen ion concentration, from the viewpoint of suppressing pitting corrosion of the aluminum current collector due to halogen ions, and may be, for example, 0.01 mol / L or less, or may be 0.001 mol / L or less.

[0021] The ultrasonic treatment is performed with multiple electrodes to be treated immersed in the treatment solution. The number of electrodes to be treated at one time can be appropriately selected depending on the size of the electrodes to be treated and the scale of the ultrasonic treatment device, and may be, for example, 2 or more, 5 or more, or 10 or more. The number of electrodes to be treated at one time may be, for example, 1000 or less, 100 or less, or 50 or less.

[0022] Sweeping the frequency means periodically changing the frequency, as shown in Figures 1 and 2, for example. The frequency of the ultrasonic waves may be periodically changed so as to reciprocate between a maximum frequency Fmax and a minimum frequency Fmin, centered on a fundamental frequency F0 (see Figures 1 and 2). The fundamental frequency F0 is preferably 40 kHz or more and 240 kHz or less, and more preferably 80 kHz or more and 200 kHz or less. In ultrasonic processing, when the sweep width is defined as the frequency fluctuation range centered on the fundamental frequency F0 (see Figure 2), the sweep width may be within ±5 kHz. In other words, Fmax - F0 ≦ +5 kHz, Fmin - F0 ≧ -5 kHz. The sweep width may be within ±3 kHz or within ±1 kHz. In ultrasonic processing, one sweep cycle is defined as the period from the rising edge of the wave with the minimum frequency Fmin to the falling edge of the wave with the maximum frequency Fmax (see Figure 1), and 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. The sweep rate may also be 2000 sweep cycles / second or less. Note that one sweep cycle may be half the period from the rising edge of the wave with the minimum frequency Fmin to the rising edge of the next wave with the minimum frequency Fmin.

[0023] For example, as shown in FIG. 3A, ultrasonic processing is performed by maintaining the electrode spacing D between multiple electrodes to be processed longer than the half wavelength H of the ultrasonic fundamental frequency F0, i.e., D > H. This can improve processing efficiency compared to when D ≦ H, as shown in FIG. 3B. The electrode spacing D is the distance between the centers of the thicknesses of adjacent electrodes to be processed when the electrodes are arranged in the thickness direction (the direction perpendicular to the surface of the current collector on which the electrode composite material is formed). The ratio H / D of the half wavelength H to the electrode spacing D may be less than 1, but may also be, for example, 0.9 or less, or 0.8 or less. The value of H / D may be, for example, 0.2 or more, or 0.3 or more. The electrode spacing D may be, for example, 1 mm or more, 3 mm or more, or 5 mm or more. The electrode spacing D may be, for example, 50 mm or less, 20 mm or less, or 10 mm or less.

[0024] The electrode spacing D may be maintained by fixing the target electrode to a jig. The jig may have guides arranged at a distance corresponding to the electrode spacing D (e.g., the same distance as the electrode spacing D or a distance obtained by dividing the electrode spacing D by an integer), and the target electrode may be fixed to the guide. The target electrode is preferably detachably fixed to the jig. For example, the target electrode may be fixed to the guide using a fastener such as a screw or clip, or the target electrode may be fixed by bending it and hooking it onto the guide, or the target electrode may be fixed by inserting it into a guide with an insertion groove. The guide may be movable and fixed so that the spacing can be adjusted, or may be fixed so that it cannot be moved. The guide may be configured to be movable to a predetermined position by a guide driver. Ultrasonic treatment may be performed with the jig stationary or while it is moving. The jig may be configured to perform a predetermined operation (e.g., oscillation) by a jig driver. Ultrasonic treatment may be performed with the target electrode and the jig immersed in the treatment solution. The electrode to be treated is preferably arranged upright so that the surface direction of the electrode to be treated substantially coincides with the vertical direction, for example, from the viewpoint of preventing the electrode composite material separated from the electrode to be treated from remaining on the current collector surface. The angle between the vertical direction and the surface direction of the electrode to be treated may be, for example, 45° or less, 30° or less, or 10° or less. Ultrasonic waves are preferably applied using an ultrasonic bath rather than an ultrasonic probe.

[0025] In the separation step, the ultrasonic treatment is preferably carried out for 30 minutes or less, more preferably for 10 minutes or less, even more preferably for 300 seconds or less, and even more preferably for 180 seconds or less. In the separation step, the ultrasonic treatment may be carried out for 1 second or more, 5 seconds or more, 10 seconds or more, or 15 seconds or more.

[0026] In the separation process, the total contact area between the current collector and the electrode mixture is A [cm 2] and the ultrasonic output (oscillator output) is B [W], the output density (power density) expressed as B / A is 30W / cm 2 It is preferable to perform ultrasonic treatment so that the power density B / A is 10 W / cm 2 It is preferable that the power consumption is 5 W / cm or less. 2 The power density B / A may be 0.1 W / cm or less. 2 More than 0.5W / cm 2 It may be more than that.

[0027] In the separation step, ultrasonic treatment is preferably performed in a non-heated environment. For example, 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.

[0028] By carrying out the separation process described above, the electrode composite is removed from the current collector, and the electrode composite removed from the current collector is dissolved and / or dispersed in water, or precipitates. Thus, after ultrasonic treatment, the current collector and the electrode composite are separated, and the current collector and a composite-containing treatment solution containing the electrode composite are obtained. At this time, ultrasonic treatment is performed while maintaining the electrode distance longer than half the wavelength of the fundamental frequency of the ultrasonic waves, thereby improving treatment efficiency.

[0029] In the separation step, ultrasonic treatment may be performed so that the removal rate of the electrode composite from the current collector is 95% or more. The removal rate is preferably 97% or more, and more preferably 99% or more. The removal rate R [%] is calculated using the formula R = (W1 - W2) × 100 / W1, where W1 [g] is the mass of the electrode composite attached to the current collector of the electrode to be treated before the separation step, and W2 [g] is the mass of the electrode composite attached to the current collector of the electrode to be treated after the separation step.

[0030] Before the separation step, a removal step of removing the electrode from the electricity storage device may be performed. The electrode removed in the removal step may be left as is without being shredded, or may be cut into pieces with an area of ​​5 cm. 2 More than 10cm 2 More than 30cm 2It may be cut into the above-mentioned shapes and used as the electrode to be treated.

[0031] After the separation step, a current collector treatment step may be performed in which the current collector separated in the separation step is washed and dried. The current collector may be washed while a washing liquid is flowing through it, or by immersing it in the washing liquid. The washing liquid is preferably water. The current collector may be dried by air drying, heat drying, vacuum drying, barrel drying, spin drying, suction drying, infrared drying, or a combination thereof. After the separation step, a composite treatment step may be performed in which the electrode composite is filtered from the composite-containing water obtained in the separation step and dried. In the composite treatment step, the electrode composite may be washed during or after filtration of the electrode composite. The washing liquid is preferably water. The electrode composite may be dried by air drying, heat drying, vacuum drying, barrel drying, spin drying, suction drying, infrared drying, or a combination thereof. In the composite treatment step, instead of filtering the electrode composite, the electrode composite may be separated from the composite-containing water by a solid-liquid separation method such as centrifugation or evaporation to dryness.

[0032] The separation step, current collector treatment step, and composite treatment step may be performed in a batch system or a continuous system. When the separation step or current collector treatment step is performed continuously, a roll-to-roll system may be adopted. When the separation step is performed using the roll-to-roll system, the electrodes removed in the removal step may be sequentially wound into rolls and used as electrodes to be treated. Note that this separation method produces a current collector and an electrode composite, and therefore this separation method is also a method for producing a current collector and an electrode composite.

[0033] [Separation device] The separation device of the present disclosure includes a separation unit that ultrasonically treats an electrode to be treated to separate the current collector and the electrode composite, and a control unit that controls the separation unit. This separation device may perform the above-described separation method, and the configurations and conditions described for the above-described separation method may be applied.

[0034] Hereinafter, a separation device 10 will be described as an example of a separation device. FIG. 4 is an explanatory diagram showing an outline of the configuration of the separation device 10. FIG. 5 shows an outline of the configuration of an example of a jig 60. The separation device 10 includes a separation unit 20 and a control unit 15. The separation device 10 performs ultrasonic treatment on a target electrode 50 including a current collector 52 and an electrode composite 54, thereby separating the current collector 52 from the electrode composite 54. The separation device 10 performs ultrasonic treatment on a plurality of target electrodes 50, which are fixed to a jig 60. The target electrode 50, the current collector 52, and the electrode composite 54 may be the same as the target electrode, the current collector, and the electrode composite described in the separation method, respectively. The jig 60 may also be the same as the jig described in the separation method.

[0035] The separation unit 20 performs ultrasonic treatment on the electrode 50 to be treated in the treatment liquid 32. The separation unit 20 includes a treatment container 22, a vibrator 28, and an oscillator 30. The treatment container 22 contains the electrode 50 to be treated and the treatment liquid 32. Here, the electrode 50 to be treated is contained in the treatment container 22 while being fixed to a jig 60. The treatment container 22 includes an inner bath 24 in which the electrode 50 to be treated is contained, a mounting table 25 on which the inner bath 24 is placed, and an outer bath 26 in which the inner bath 24 and the mounting table 25 are contained. The inner bath 24 contains the treatment liquid 32, and the outer bath 26 contains an ultrasonic propagation medium 36. The treatment liquid 32 is, for example, water or an aqueous solution. The ultrasonic propagation medium 36 is, for example, water, and serves to propagate ultrasonic waves together with the treatment liquid 32. The processing vessel 22 is provided with piping and valves (not shown), which allow the supply of the processing liquid 32 to the processing vessel 22 and the amount of the supply to be adjusted.

[0036] As shown in FIG. 5 , the jig 60 has guides 64 arranged at intervals corresponding to the electrode spacing D (here, the same interval as the electrode spacing D). Here, the guides 64 are arranged on both sides of a rectangular parallelepiped frame 62 at intervals corresponding to the electrode spacing D. The target electrode 50 is fixed to the jig 60 by bending both ends and hooking them onto the guides 64 arranged on both sides of the frame 62, thereby maintaining the electrode spacing D at a predetermined interval. The guides 64 may be configured to be movable and fixed, and the spacing between the guides 64 may be adjustable. The guides 64 may be configured to be movable to a predetermined position by a guide driver (not shown), or the spacing between the guides 64 may be adjustable by controlling the guide driver. The jig 60 may be configured to perform a predetermined operation (e.g., swinging) by a jig driver (not shown). The jig 60 is not limited to the one shown in FIG. 5 as long as it can maintain the electrode spacing between the target electrodes 50 at a predetermined interval. Furthermore, if the electrode spacing of the processing target electrodes 50 can be maintained at a predetermined spacing, the jig 60 may be omitted.

[0037] The transducer 28 is disposed so as to be in contact with the processing vessel 22. The oscillator 30 supplies power to the transducer 28 to cause it to oscillate. The oscillator 30 has a sweep function. The sweep function is a function of periodically changing the frequency, as shown in FIGS. 1 and 2, for example. The separation unit 20 is configured to be able to sweep (periodically change) the frequency of the ultrasonic waves generated from the transducer 28 by using the sweep function of the oscillator 30.

[0038] The control unit 15 is configured as a microprocessor centered on a CPU, and in addition to the CPU, is equipped with a storage device and input / output ports (not shown). The control unit 15 is electrically connected to the oscillator 30 as well as a guide drive unit and a jig drive unit (not shown) as needed, and outputs signals to and receives signals from any of these. The control unit 15 is configured to control the oscillator 30 so as to perform ultrasonic treatment while sweeping the frequency of the ultrasonic waves. The control unit 15 is configured to control the oscillator 30 and, if necessary, the guide drive unit so as to perform ultrasonic treatment while maintaining the electrode spacing D of the treatment target electrode 50 longer than half the wavelength H of the fundamental frequency of the ultrasonic waves. The ultrasonic treatment conditions may be the same as those of the separation method described above.

[0039] An example of the operation of the separation device 10 will be described. First, the treatment liquid 32 is placed in the treatment container 22, and multiple electrodes 50 to be treated, fixed to the jig 60, are immersed in the treatment liquid 32. The treatment liquid 32 may be any of the treatment liquids described in the separation method above. After the electrodes 50 to be treated are immersed in the treatment liquid 32, the control unit 15 controls the oscillator 30 to supply power to the vibrator 28, causing the vibrator 28 to oscillate. This results in ultrasonic treatment of the electrodes 50 to be treated in the treatment water 32. During ultrasonic treatment, the control unit 15 uses the sweep function of the oscillator 30 to control the oscillator 30 to sweep the frequency under the following conditions: a fundamental frequency F0 of 40 kHz or more and 240 kHz or less, a sweep width within ±5 kHz, and a sweep rate of 500 sweep cycles / second or more. Furthermore, the control unit 15 controls the oscillator 30 and, if necessary, the guide drive unit, to maintain the electrode spacing D of the processing target electrode 50 longer than the half wavelength H of the fundamental frequency of the ultrasonic wave, thereby performing ultrasonic processing. 2The control unit 15 controls the oscillator 30 to output a power equal to or less than the following: Furthermore, the control unit 15 controls the oscillator 30 to perform the ultrasonic treatment for a predetermined time, for example, in the range of 1 second to 30 minutes. By such ultrasonic treatment, the current collector 52 and the electrode composite 54 of the treatment target electrode 50 are separated, and a composite-containing treatment solution containing the current collector 52 and the electrode composite 54 is obtained.

[0040] The separation method and apparatus described above can improve processing efficiency when simultaneously performing processing to separate a current collector from an electrode composite on multiple electrodes, achieving, for example, a composite removal rate of 95% or more. The reasons for this effect are presumed to be as follows: By performing ultrasonic processing while maintaining an electrode distance longer than half the wavelength of the fundamental frequency of the ultrasonic waves, the ultrasonic waves efficiently act on the electrodes, thereby improving processing efficiency. Furthermore, by performing ultrasonic processing while sweeping the ultrasonic frequency in the processing solution, optimal energy distribution is achieved, suppressing damage to the current collector and residual electrode composite, thereby enabling high-precision separation of the current collector and electrode composite. Furthermore, because the separation utilizes the physical action of the cavitation effect of ultrasonic waves, the current collector and electrode composite can be separated using an aqueous processing solution. Furthermore, because water has a high surface tension and is more likely to generate a cavitation effect than organic solvents, the current collector and electrode composite can be separated efficiently. The separation method and apparatus described above utilize a physical action based on the cavitation effect of ultrasound, which allows for separation of the current collector and electrode composite using an aqueous treatment solution, regardless of whether the binder contained in the electrode composite is aqueous or organic. Aqueous treatment solutions offer the following advantages: they are relatively inexpensive, the treatment solution is easy to remove from the separated current collector and electrode composite, and wastewater treatment is easy and environmentally friendly. Furthermore, because aqueous treatment solutions can efficiently separate the current collector and electrode composite, they can be used at high frequencies (low energy), such as 40 to 240 kHz (preferably 80 to 200 kHz), to separate the current collector and electrode composite with high precision, even when the electrode being treated is relatively large and in a non-heated environment.

[0041] In addition, the separated electrode mixture can be recovered to obtain an electrode mixture, thereby enabling efficient production of the electrode mixture. When producing the electrode mixture, the recovered electrode mixture may be used as is, or a new electrode mixture may be produced by extracting the active material from the recovered electrode mixture and adding a binder and a conductive material.

[0042] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure.

[0043] For example, in the above-described embodiment, the separation device 10 performs ultrasonic treatment in a batch manner, but may also perform ultrasonic treatment in a continuous manner.

[0044] The present disclosure may be any of the following [1] to

[10] . [1] A separation method including a separation step of ultrasonically treating a target electrode having a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite, wherein the ultrasonic frequency is swept while a plurality of the target electrodes are immersed in a treatment solution, and the ultrasonic treatment is performed while maintaining the electrode spacing of the plurality of target electrodes to be treated longer than half the wavelength of the fundamental frequency of the ultrasonic waves. [2] The separation method according to [1], wherein the value of H / D is 0.2 or more and 0.9 or less, where D [mm] is the electrode distance and H [mm] is the half wavelength. [3] The separation method according to [1] or [2], wherein the electrode spacing is 1 mm or more and 50 mm or less. [4] The separation method according to any one of [1] to [3], wherein the plurality of electrodes to be processed are fixed to a jig to maintain the electrode spacing. [5] The separation method according to [4], wherein the ultrasonic treatment is carried out while moving the jig. [6] The separation method according to any one of [1] to [5], wherein the fundamental frequency is 80 kHz or more and 200 kHz or less. [7] The separation method according to any one of [1] to [6], wherein the ultrasonic treatment is carried out for a period of 10 seconds to 10 minutes. [8] The separation method according to any one of [1] to [7], which satisfies any one or more of the following (1) to (6): (1) The ultrasonic treatment is carried out so that the removal rate of the electrode mixture from the current collector is 95% or more. (2) A water-based processing liquid is used as the processing liquid. (3) The sweep is performed with a sweep width of ±3 kHz around the fundamental frequency. (4) The sweep is performed at a sweep rate of 500 sweep cycles / second or greater. (5) The total contact area between the current collector and the electrode mixture is A [cm 2 ] and the ultrasonic output is B [W], the power density expressed as B / A is 10W / cm 2 The ultrasonic treatment is carried out as follows. (6) The ultrasonic treatment is carried out in a non-heated environment. [9] A separation device comprising: a separation unit that ultrasonically processes a target electrode comprising a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite; and a control unit that controls the separation unit to perform the ultrasonic processing by sweeping the frequency of ultrasonic waves while immersing multiple target electrodes in a processing solution, and maintaining the electrode spacing of the multiple target electrodes to be processed longer than half the wavelength of the fundamental frequency of the ultrasonic waves.

[10] A method for producing an electrode composite, comprising: a separation step of ultrasonically treating a target electrode having a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite; in the separation step, a plurality of the target electrodes are immersed in a treatment solution, the frequency of ultrasonic waves is swept, and the ultrasonic treatment is performed while maintaining the electrode spacing of the plurality of target electrodes to be treated longer than half the wavelength of the fundamental frequency of the ultrasonic waves; and the separated electrode composite is recovered to obtain the electrode composite. [Example]

[0045] Examples of carrying out the separation method of the present disclosure are described below. Experimental Examples 2 to 7, 9, 11, 15, and 17 correspond to Examples, and Experimental Examples 1, 8, 10, 12 to 14, 16, and 18 to 21 correspond to Comparative Examples.

[0046] [Preparing the electrode to be treated] The electrode to be treated is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 A positive electrode composite containing 92% by mass of O2 (NCM, manufactured by Toda Kogyo Kogyo Co., Ltd.), 5% by mass of acetylene black (manufactured by Denka Co., Ltd.), and 3% by mass of polyvinylidene fluoride (PVDF, manufactured by Kureha) was made into a paste using N-methylpyrrolidone (NMP), and this paste was applied to both sides of a 20 μm thick aluminum current collector foil to produce a 24 mm × 66 mm electrode.

[0047] [Ultrasonic treatment] For the ultrasonic treatment, an ultrasonic device (Branson GCX-M-3FQ12, maximum output 500 W, outer tank capacity 20 L) was used. Specifically, as shown in Figure 4, water was placed in the outer tank 26, and 1 L of water was placed in the glass container (inner tank 24) as the treatment solution 32. A jig 60 containing the target electrode 50 was immersed in the treatment solution, and ultrasonic waves were applied from the transducer 28 below the outer tank 26. The ultrasonic treatment was performed under the following conditions: frequency 40 kHz, 80 kHz, 120 kHz, or 170 kHz; sweep width ±1 kHz; sweep speed 1000 sweep cycles / second; output power 250 W or 500 W; and treatment time 30 seconds. The mass of the target electrode was measured before and after the ultrasonic treatment, and the removal rate of the electrode composite was calculated. The output power (500 W) of the ultrasonic device was divided by the contact area between the current collecting foil and the electrode composite layer (here, the number of electrodes × electrode area × 2) to calculate the power density. The electrodes 50 to be treated were set in the jig 60 as follows: A predetermined number of electrodes (24 mm × 66 mm) were set vertically at a predetermined interval on a jig equipped with guides. The electrodes were folded 6 mm on each side to ensure they would not come off the jig during ultrasonic treatment or cleaning, and the inter-electrode distance was maintained without bending. Because composite material may remain at the folds, the peeling condition was confirmed on the flat areas other than the folds. The composite removal rate was calculated as the maximum removal rate from the mass difference before and after ultrasonic treatment by cutting a 20 mm × 50 mm piece from the flat part of the electrode with the most peeling, excluding the electrodes at both ends. Table 1 shows the ultrasonic conditions, electrode installation conditions, composite removal rate, etc. Figure 6 shows the relationship between the H / D value and removal rate for Experimental Examples 1 to 21.

[0048] [Results and Discussion] In Experimental Examples 1 to 4, we investigated the following conditions: output power of 250 W, electrode spacing of 12.7 mm, five electrodes, and frequencies of 40, 80, 120, and 170 kHz. As shown in Table 1 and Figure 6A, in Experimental Examples 2 to 4, where frequencies were 80, 120, and 170 kHz, the electrode spacing was greater than half the wavelength, and composite removal rates of 95% or more were achieved. In Experimental Example 1, where the electrode spacing was less than half the wavelength, the composite removal rate was 91%, which was inferior to the composite removal rates of Experimental Examples 2 to 4. The fact that Experimental Example 4, which used a frequency of 170 kHz, had a lower removal rate than Experimental Examples 2 to 3, which used frequencies of 80 and 120 kHz, is presumed to indicate that higher frequencies tend to have a lower cavitation effect.

[0049] In Experimental Examples 5 to 7, we investigated the following conditions: output power of 500 W, electrode spacing of 12.7 mm, five electrodes, and frequencies of 80, 120, and 170 kHz. As shown in Table 1 and Figure 6B, in Experimental Examples 5 to 7 where the frequencies were 80, 120, and 170 kHz, the electrode spacing was greater than half the wavelength, and the composite removal rate was 99% or more. At a frequency of 170 kHz, the composite removal rate increased slightly by increasing the output power (see Experimental Examples 4 and 7).

[0050] In Experiments 8 to 11, the electrode spacing was 6.4 mm, five electrodes were used, and different output powers of 250 W and 500 W and frequencies of 80 kHz and 120 kHz were investigated. As shown in Table 1 and Figure 6, at both the 250 W and 500 W output powers, when the frequency was 80 kHz and the electrode spacing was less than half the wavelength, the composite removal rate was 90% or less (see Experiments 8 and 10), whereas when the frequency was 120 kHz and the electrode spacing was greater than half the wavelength, the composite removal rate was 100% (see Experiments 9 and 11). At the 80 kHz frequency, increasing the output power slightly increased the composite removal rate (see Experiments 8 and 10).

[0051] In Experimental Examples 12 and 13, the electrode spacing was 3.2 mm, five electrodes were used, the frequency was 120 kHz, and the outputs were different, 250 W and 500 W. As shown in Table 1 and Fig. 6, the composite removal rate was higher in Experimental Example 13 with an output of 500 W than in Experimental Example 12 with an output of 250 W, but in both cases the electrode spacing was smaller than half the wavelength, and the composite removal rate was less than 90%.

[0052] In Experiments 14 to 17, we investigated different cases: an electrode spacing of 6.4 mm, ten electrodes, output power of 250 W, 500 W, and frequency of 80 kHz and 120 kHz. As shown in Table 1 and Figure 6, at both 250 W and 500 W outputs, when the frequency was 80 kHz and the electrode spacing was less than half the wavelength, the composite removal rate was 73% or less (see Experiments 14 and 16), whereas when the frequency was 120 kHz and the electrode spacing was greater than half the wavelength, the composite removal rate was 100% (see Experiments 15 and 17). At a frequency of 80 kHz, increasing the output power slightly increased the composite removal rate (see Experiments 14 and 16).

[0053] In Experimental Examples 18 to 21, we investigated different cases where the electrode spacing was 3.2 mm, the frequency was 120 kHz, the number of electrodes was 10 or 20, and the output was 250 W or 500 W. As shown in Table 1 and Figure 6, at both the output of 250 W or 500 W and with both 10 or 20 electrodes, when the frequency was 120 kHz and the electrode spacing was less than half the wavelength, the composite removal rate was 64% or less (see Experimental Examples 18 to 21).

[0054] From the above, we found that regardless of ultrasonic frequency, power, or number of sheets, composite removal rates of 95% or more can be achieved when the relationship "electrode spacing > half wavelength (D > H)" shown in Figure 3 holds. At a high ultrasonic frequency of 170 kHz, the cavitation effect is reduced, as in Experimental Example 4, and composite removal rates can be reduced at low power levels. Therefore, we inferred that a frequency of 80 to 120 kHz is optimal. Increasing the power level slightly increased composite removal rates, but when the relationship "electrode spacing > half wavelength" did not hold, composite removal rates did not exceed 95%. This rule was also observed when the number of sheets was changed with the same electrode spacing. Therefore, we found that methods and devices that maintain the relationship "electrode spacing > half wavelength" are preferable for more efficient mass-processing of composite material removal using ultrasonic treatment.

[0055] In the experimental example, the jig was left stationary in the beaker while ultrasonic treatment was performed, but since there is a risk that the peeled composite material remaining between the electrodes will inhibit the ultrasonic waves, it was inferred that ultrasonic treatment would be even more effective if the jig was moved in the treatment solution.

[0056] [Table 1] [Industrial Applicability]

[0057] The present disclosure is applicable to the field of the battery industry. [Explanation of symbols]

[0058] 10 Separation device, 15 Control unit, 20 Separation unit, 22 Treatment container, 24 Inner tank, 25 Mounting table, 26 Outer tank, 28 Vibrator, 30 Oscillator, 32 Treated water, 36 Ultrasonic propagation medium, 50 Electrode to be treated, 52 Current collector, 54 Electrode mixture, 60 Jig, 62 Frame, 64 Guide, D Electrode spacing, H Half wavelength.

Claims

1. a separation step of ultrasonically treating a treatment target electrode including a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite, In the separation step, the ultrasonic treatment is performed by sweeping the frequency of ultrasonic waves while the plurality of electrodes to be treated are immersed in the treatment liquid, and the electrode spacing between the plurality of electrodes to be treated is maintained so as to be longer than half the wavelength of the fundamental frequency of the ultrasonic waves. Separation method.

2. 2. The separation method according to claim 1, wherein when the electrode distance is D [mm] and the half wavelength is H [mm], the value of H / D is 0.2 or more and 0.9 or less.

3. The separation method according to claim 1 or 2, wherein the electrode spacing is 1 mm or more and 50 mm or less.

4. The separation method according to claim 1 or 2, wherein the plurality of electrodes to be treated are fixed to a jig to maintain the electrode spacing.

5. The separation method according to claim 4 , wherein the ultrasonic treatment is performed while the jig is moving.

6. 3. The separation method according to claim 1, wherein the fundamental frequency is between 80 kHz and 200 kHz.

7. The separation method according to claim 1 or 2, wherein the ultrasonic treatment is carried out for a period of 10 seconds to 10 minutes.

8. The separation method according to claim 1 or 2, which satisfies any one or more of the following (1) to (6): (1) The ultrasonic treatment is carried out so that the removal rate of the electrode mixture from the current collector is 95% or more. (2) A water-based processing liquid is used as the processing liquid. (3) The sweep is performed with a sweep width within ±3 kHz centered on the fundamental frequency. (4) The sweep is performed at a sweep rate of 500 sweep cycles / second or more. (5) The total contact area between the current collector and the electrode mixture is A [cm 2 ] and the ultrasonic output is B [W], the power density expressed as B / A is 10 W / cm 2 The ultrasonic treatment is carried out as follows. (6) The ultrasonic treatment is carried out in a non-heated environment.

9. a separation unit that ultrasonically treats a target electrode including a current collector and an electrode composite formed on the current collector to separate the current collector and the electrode composite; a control unit that controls the separating unit to sweep the frequency of ultrasonic waves while the plurality of electrodes to be treated are immersed in the treatment liquid, and to perform the ultrasonic treatment while maintaining the electrode spacing of the plurality of electrodes to be treated to be longer than half the wavelength of the fundamental frequency of the ultrasonic waves; A separation device comprising:

10. a separation step of ultrasonically treating a treatment target electrode including a current collector and an electrode composite formed on the current collector to separate the current collector from the electrode composite, In the separation step, the ultrasonic treatment is performed by sweeping the frequency of ultrasonic waves while the plurality of electrodes to be treated are immersed in the treatment liquid, and the electrode spacing between the plurality of electrodes to be treated is maintained so as to be longer than half the wavelength of the fundamental frequency of the ultrasonic waves; recovering the separated electrode mixture to obtain an electrode mixture; Manufacturing method of electrode mixture.

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