Separation method and separation device

Abstract

This separation method includes: a pretreatment step for attaching a pretreatment liquid containing an organic solvent to a treatment target electrode provided with a current collector and an electrode mixture that is formed on the current collector and includes a binder; and a separation step for performing an ultrasonic treatment by immersing the treatment target electrode after the pretreatment in a treatment water to separate the current collector and the electrode mixture from each other. This separation device is provided with: a pretreatment unit that attaches a pretreatment liquid containing an organic solvent to a treatment target electrode provided with a current collector and an electrode mixture that is formed on the current collector and includes a binder; and a separation unit that performs an ultrasonic treatment by immersing the treatment target electrode after the pretreatment in a treatment water to separate the current collector and the electrode mixture from each other.

Description

Separation method and separation device

[0001] The present disclosure relates to a separation method and a separation device.

[0002] Conventionally, a method for separating the current collector and the electrode composite in battery recycling has been proposed, in which the electrodes are subjected to ultrasonic treatment while sweeping the ultrasonic frequency in water (for example, Patent Document 1). This method utilizes the physical action of the cavitation effect of ultrasound, rather than the chemical action of an organic solvent or aqueous solution. 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.

[0003] JP 2023-102744 A

[0004] However, with the above-mentioned method, when treating an electrode with a thick electrode composite layer or a high-density electrode, it may take a long time to separate the current collector from the electrode composite, and there has been a demand for a more efficient separation of the current collector from the electrode composite.

[0005] The present disclosure has been made to solve such problems, and a main object of the present disclosure is to provide a separation method and a separation device that can more efficiently separate a current collector and an electrode mixture.

[0006] In order to achieve the above-mentioned object, the present inventors discovered that the current collector and the electrode composite can be separated more efficiently by applying a pretreatment liquid containing an organic solvent to the electrode and then immersing the electrode in treatment water and performing ultrasonic treatment, and have completed the present disclosure.

[0007] That is, the separation method of the present disclosure includes: a pretreatment step of applying a pretreatment liquid containing an organic solvent to an electrode to be treated, the electrode including a current collector and an electrode composite formed on the current collector and containing a binder; and a separation step of immersing the pretreated electrode to be treated in treatment water and subjecting it to ultrasonic treatment, thereby separating the current collector from the electrode composite.

[0008] The separation device of the present disclosure includes a pretreatment section that applies a pretreatment liquid containing an organic solvent to a treatment target electrode that includes a current collector and an electrode composite that is formed on the current collector and contains a binder, and a separation section that immerses the pretreated treatment target electrode in treatment water and performs ultrasonic treatment on the electrode composite to separate the current collector from the electrode composite.

[0009] The separation method and separation device disclosed herein can separate the current collector and the electrode mixture more efficiently. The reason for this effect is presumed to be as follows: In this separation method and separation device, the adhesive strength of the binder is weakened in the pretreatment step by utilizing the chemical action of an organic solvent. Then, in the separation step, the current collector and the electrode mixture are separated by utilizing the physical action of the cavitation effect of ultrasound, rather than the chemical action of an organic solvent or aqueous solution. Because water has a high surface tension and is more likely to generate a cavitation effect than an organic solvent, ultrasonic treatment with treated water rather than a pretreatment solution containing an organic solvent can efficiently separate the current collector and the electrode mixture.

[0010] 1 is an explanatory diagram of a sweep and a sweep cycle; an explanatory diagram of a sweep width; an explanatory diagram showing an outline of the configuration of a separation device 10; an explanatory diagram showing an outline of the configuration of a separation device 10 before ultrasonic treatment; an explanatory diagram showing an outline of the configuration of a separation device 10 after ultrasonic treatment; a flowchart showing an example of a separation method;

[0011] [Separation Method] The separation method disclosed herein includes a pretreatment step of applying a pretreatment liquid to an electrode to be treated, and a separation step of immersing the pretreated electrode to be treated in treatment water and subjecting it to ultrasonic treatment to separate the current collector and the electrode composite.

[0012] (Electrode to be treated) The electrode to be treated comprises a current collector and an electrode composite formed on the current collector. The electrode to be treated is an electrode of an electricity storage device such as an ion secondary battery such as a lithium ion secondary battery, an electric double layer capacitor, a hybrid capacitor, or a pseudo-electric double layer capacitor, and may be removed from a used electricity storage device or a deteriorated electricity storage device. The electrode to be treated may be a positive electrode, a negative electrode, or a bipolar electrode with a positive electrode composite formed on one side and a negative electrode composite formed on the other side. The electrode to be treated may be an electrode removed from the electricity storage device without being shredded, for example, an electrode having an area of ​​10 cm 2 It may be more than 30 cm 2 The above may also be used.

[0013] Examples of materials for the current collector include aluminum, copper, titanium, stainless steel, nickel, iron, baked carbon, conductive polymers, and conductive glass. Of 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, lath, porous, foamed, and formed fiber group. The thickness of the current collector is, for example, 1 to 500 μm.

[0014] The electrode mixture may contain an electrode active material, a binder, and, if necessary, a conductive material. The electrode mixture may be, for example, a mixture of an electrode active material, a conductive material, and a binder, and an appropriate solvent added to form a paste, which is then applied to the surface of a current collector, dried, and, if necessary, compressed to increase electrode density. The electrode mixture may be formed on one or both sides of the current collector.

[0015] Examples of the electrode active material contained in the electrode mixture include transition metal sulfides such as TiS, TiS, MoS, and FeS, and those having a basic composition formula of Li (1-x) MnO2 (0<x<1, etc., same below) and Li (1-x) Lithium manganese composite oxide such as Mn2O4, the basic composition formula is Li (1-x) Lithium cobalt composite oxide such as CoO2, the basic composition formula is 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 composition formula such as LiVO (a + b + c = 1), lithium vanadium composite oxides with a basic composition formula such as LiVO, transition metal oxides with a basic composition formula such as VO, and lithium iron phosphate. The electrode active material may also include layered rock salt active materials such as lithium nickel cobalt manganese composite oxides. The term "basic composition formula" refers to the inclusion of other elements such as Al and Mg. Examples of electrode active materials include activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, 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 absorbing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers, all of which are active materials used in the negative electrodes 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 oxides and lithium-vanadium composite oxides. Examples of conductive materials included in the electrode composite include graphites 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.).

[0016] The binder contained in the electrode mixture serves to bind the active material particles and the conductive material particles together. It may be a solvent-based binder dissolved in an organic solvent, or a water-based binder dissolved in water or various aqueous solutions, or a mixture thereof. Examples of solvent-based binders include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), and fluorine-containing rubber, thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). The solvent-based binder may be a hydrophobic binder. Examples of water-based binders include polyvinyl alcohol (PVA), styrene butadiene copolymer (SBR), polyethylene oxide (PEO), and the like, and may contain carboxymethyl cellulose (CMC). The water-based binder may also be a hydrophilic binder. 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. The binder is preferably a solvent-based binder. Solvent-based binders are generally hydrophobic and inhibit water, such as process water, from seeping into the electrode mixture, which contributes to the time required for separation of the current collector and the electrode mixture. Therefore, the present disclosure is highly useful when the binder is a solvent-based binder. 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) or artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.). Of these, carbon black and acetylene black are preferred as the conductive material from the viewpoints of electron conductivity and coatability.

[0017] The electrode mixture may contain, for example, polyvinylidene fluoride (PVDF). Polyvinylidene fluoride may be contained in the electrode mixture as a solvent-based binder. PVDF has relatively low wettability with water, which inhibits water such as process water from seeping into the electrode mixture, and is one of the reasons why it takes time to separate the current collector and the electrode mixture. Therefore, it is highly significant to apply the present disclosure when the electrode mixture contains PVDF.

[0018] The basis weight of the electrode mixture layer is, for example, 10 mg / cm 2 or more, 15 mg / cm 2 or more, 20 mg / cm 2 The thickness of the electrode mixture layer may be 50 μm or more, 55 μm or more, or 60 μm or more. The density of the electrode mixture layer may be, for example, 1.2 g / cm 3 or more, 1.5 g / cm 3 or more, 1.6 g / cm 3 It may be 3 g / cm or more. 3 When the electrode mixture layer has a high basis weight, a large thickness, or a high density, water such as treated water does not easily permeate into the electrode mixture layer, and separation of the current collector and the electrode mixture tends to take time, and therefore application of the present disclosure is highly significant.

[0019] (Pretreatment Step) In the pretreatment step, a pretreatment liquid containing an organic solvent is applied to the electrode to be treated. In the pretreatment step, the electrode to be treated may be immersed in the pretreatment liquid to apply the pretreatment liquid to the electrode to be treated. Alternatively, the pretreatment liquid may be applied to the electrode to be treated by coating or spraying. In this case, the coating or spraying may be performed so that the entire surface of the electrode to be treated is covered with the pretreatment liquid. Note that, hereinafter, the case where the pretreatment liquid is applied by immersion will be mainly described, and the application of the pretreatment liquid will sometimes be referred to as immersion and the pretreatment liquid as immersion liquid. However, immersion can be appropriately interpreted as application of the pretreatment liquid and the immersion liquid as pretreatment liquid. This also applies to the description of the separation device described below. The immersion time may be set appropriately within a range that weakens the binding strength of the binder contained in the electrode mixture, and may be, for example, 0.1 seconds or more, 0.5 seconds or more, or 1 second or more. The immersion time is preferably set within a range in which the current collector and the electrode mixture do not separate and the electrode mixture remains attached to the current collector in the pretreatment step, or within a range in which the electrode mixture components do not elute in the pretreatment step, and may be, for example, within 10 minutes, within 5 minutes, or within 1 minute. In the pretreatment step, it is preferable not to perform ultrasonic treatment during immersion, and for example, the electrode mixture may be left to stand during immersion.

[0020] In the pretreatment step, immersion is preferably performed in a non-heated environment. In the pretreatment step, immersion may be performed, for example, in a temperature range of 0°C to 30°C, or in a temperature range of 15°C to 25°C.

[0021] The immersion liquid may be, for example, an organic solvent alone or a mixture of water and an organic solvent. The immersion liquid preferably contains 10% by volume or more of the organic solvent, preferably 20% by volume or more, and more preferably 50% by volume or more. Examples of organic solvents used in the immersion liquid include alcohols such as methanol, ethanol, 1-butanol, 1-propanol, 2-propanol, and ethylene glycol; ketones such as acetone; heterocyclic compounds such as N-methyl-2-pyrrolidone and 2-pyrrolidone; amides such as N,N-dimethylformamide; esters such as trimethyl phosphate; and alkyl halides such as chloroform. The organic solvent is preferably a water-soluble organic solvent. Furthermore, the organic solvent is preferably a polar solvent.

[0022] Regarding the organic solvent used in the immersion liquid, the difference in solubility parameter (SP value) between the organic solvent and the binder can be used as a measure of the ability to weaken the binding force of the binder contained in the electrode mixture. The solubility parameter is an index that indicates how easily the target substance absorbs the solvent. The SP value is calculated by multiplying the dispersion component (δ D ), polar component (δ P ), hydrogen bond components (δ H The parameter shown by dividing it into three components is called the HSP value (Hansen solubility parameter). The unit of the HSP value is MPa. 0.5 However, this unit will be omitted in this specification. If the HSP value is δ, then δ 2 = 4δ D 2 +δ P 2 +δ H 2 The formula is established. HSP (δ D , δ P , δ H The value of (a) is considered in three-dimensional coordinates, and the closer the HSP of the target substance and the HSP of the solvent are in the Hansen space expressed by three-dimensional coordinates, the easier the target substance dissolves in the solvent and the higher the compatibility. Therefore, it is considered that the closer the distance between the HSP of the binder contained in the electrode mixture and the HSP of the organic solvent used in the immersion liquid, the stronger the power to weaken the binding strength of the electrode mixture.

[0023] The HSP distance between the organic solvent used in the immersion liquid and the binder is preferably smaller than the HSP distance between water and the binder. The HSP distance between the organic solvent and the binder is preferably 30 or less, more preferably 25 or less, even more preferably 20 or less, and even more preferably 15 or less. For example, when the electrode composite contains polyvinylidene fluoride (PVDF), the HSP distance between the organic solvent used in the immersion liquid and the PVDF is preferably smaller than the HSP distance between water and PVDF (32.5), and more preferably 20 or less.

[0024] In the pretreatment step, it is preferable to perform immersion within a range in which the elution rate of the electrode composite components (hereinafter also referred to as composite elution rate) is less than 1%. This composite elution rate is more preferably less than 0.5%, and even more preferably less than 0.1%. The composite elution rate [%] can be determined by calculating the amount of eluted composite [mg] from the difference in weight of the electrode before and after immersion, and calculating the initial composite amount [mg] from the basis weight and area of ​​the electrode composite layer in the initial electrode, and then using the following formula (1): Composite elution rate = Amount of eluted composite / Initial composite amount × 100 ... formula (1)

[0025] In the pretreatment step, it is desirable to remove excess immersion liquid from the electrode to be treated after immersion. By removing the immersion liquid, it is possible to prevent organic solvents from being carried into the treatment water. The immersion liquid may be removed by, for example, wiping, blow drying, or hot air drying. These methods are preferred because they allow the immersion liquid to be easily removed from the electrode.

[0026] (Separation Step) In the separation step, the electrode to be treated after the pretreatment step is immersed in treatment water and subjected to ultrasonic treatment to separate the current collector and the electrode composite. The ultrasonic treatment may be performed while sweeping the frequency of the ultrasonic waves. Sweeping the frequency means, for example, periodically changing the frequency as shown in Figures 1 and 2. The ultrasonic treatment may be performed using an ultrasonic probe, but is preferably performed in an ultrasonic bath.

[0027] In the separation process, the ultrasonic frequency 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 FIGS. 1 and 2). The fundamental frequency F0 is preferably 10 kHz or higher, more preferably 40 kHz or higher, and even more preferably 80 kHz or higher. The fundamental frequency F0 is preferably 240 kHz or lower, more preferably 200 kHz or lower, and may be 100 kHz or lower. In the ultrasonic treatment, when the sweep width is defined as the frequency fluctuation range centered on the fundamental frequency F0 (see FIG. 2), the sweep width may be within ±5 kHz. That is, Fmax - F0 ≦ +5 kHz, Fmin - F0 ≧ -5 kHz may be used. 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 a wave with a minimum frequency Fmin to the falling edge of a wave with a maximum frequency Fmax (see FIG. 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 a wave with a minimum frequency Fmin to the rising edge of the next wave with a minimum frequency Fmin.

[0028] 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, or 15 seconds or more.

[0029] In the separation step, the 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 50 W / cm 2 It is preferable to perform ultrasonic treatment so that the power density B / A is 30 W / cm 2It is preferable that the power density is 25 W / cm or less. 2 The power density B / A may be 1 W / cm or less. 2 or more, 5 W / cm 2 It may be more than that.

[0030] In the separation step, ultrasonic treatment is preferably performed in a non-heated environment. In the separation step, ultrasonic treatment may be performed, for example, in a temperature range of 0°C to 30°C, or in a temperature range of 15°C to 25°C.

[0031] The treated water used in the separation step may be any water, including tap water, distilled water, ion-exchanged water, etc. The treated water may contain substances other than water, but the concentration of substances other than water is preferably low, and may be 5% by mass or less, 1% by mass or less, or 0.1% by mass or less.

[0032] By carrying out the separation process described above, the electrode mixture is removed from the current collector, and the electrode mixture removed from the current collector is dissolved and / or dispersed in the treated water, or precipitates. Thus, after the ultrasonic treatment, the current collector and the electrode mixture are separated, and the current collector and mixture-containing treated water containing the electrode mixture are obtained.

[0033] In the separation step, the greater the removal rate of the electrode composite (hereinafter also referred to as composite removal rate), the more preferable, for example, 25% or more is preferable, 30% or more is more preferable, 50% or more is even more preferable, and 70% or more is even more preferable. The composite removal rate [%] can be calculated by calculating the amount of composite removed [mg] from the weight difference of the electrode before and after ultrasonic treatment, subtracting the amount of composite elution described above from the initial composite amount described above to calculate the amount of composite before separation [mg], and then using the following formula (2): Composite removal rate = amount of composite removed / amount of composite before separation × 100 ... formula (2)

[0034] Before the pretreatment step, a removal step of removing the electrodes from the electricity storage device may be performed. The electrodes removed in the removal step may be used as they are without being shredded, or may be used in a manner to remove the electrodes from the electricity storage device. 2 or more, area 30 cm 2 It may be cut into the above-mentioned shapes and used as the electrode to be treated.

[0035] 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 treated 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 treated water by a solid-liquid separation method such as centrifugation or evaporation to dryness.

[0036] The pretreatment step, 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 a electrode composite.

[0037] The separation device according to the present disclosure includes a pretreatment unit that adheres a target electrode to a pretreatment liquid containing an organic solvent, a separation unit that immerses the target electrode after the pretreatment in treatment water and ultrasonically treats it to separate the current collector from the electrode composite, and a control unit that controls the pretreatment unit and the separation unit. This separation device may perform the separation method described above, and the configuration and conditions described for the separation method may be applied.

[0038] Below, a separation device 10 will be described as an example of a separation device. FIGS. 3 to 5 are explanatory diagrams showing an outline of the configuration of the separation device 10. FIG. 4 is an explanatory diagram showing an outline of the configuration of the separation device 10 before ultrasonic treatment. FIG. 5 is an explanatory diagram showing an outline of the configuration of the separation device 10 after ultrasonic treatment. Note that the pre-treatment unit 40 is omitted in FIGS. 4 and 5 . As shown in FIG. 3 , the separation device 10 includes a pre-treatment unit 40, a separation unit 20, and a control unit 15. In this separation device 10, a target electrode 50 including a current collector 52 and an electrode composite 54 is subjected to an immersion treatment in the pre-treatment unit 40 by immersing the target electrode 50 in an immersion liquid 42 containing an organic solvent. Then, the separation unit 20 performs ultrasonic treatment in treatment water 32 to separate the target electrode 52 from the electrode composite 54. 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.

[0039] The pretreatment unit 40 immerses the target electrode 50 in the immersion liquid 42. The pretreatment unit 40 includes an immersion container 44. The immersion container 44 contains the target electrode 50 and the immersion liquid 42. The immersion liquid 42 may be an organic solvent alone or a mixture of water and an organic solvent. The pretreatment unit 40 may include an immersion liquid removal device that removes the immersion liquid 42 from the target electrode 50 after it has been removed from the immersion liquid 42. The immersion liquid removal device may be, for example, a wiping device that wipes off the immersion liquid 42, or a drying device that performs air drying or hot air drying. The pretreatment unit 40 includes a pretreatment unit internal transport unit (not shown) that receives and discharges the immersion liquid 42 from the immersion container 44, and immerses and removes the target electrode 50 from the immersion liquid 42. In the pretreatment section 40, the chemical action of the immersion liquid 42 results in a pretreated electrode 50a to be treated, which has an electrode mixture 54a with weakened binding strength.

[0040] The separation unit 20 performs ultrasonic treatment on the pretreated electrode 50a in the treatment water 32. The separation unit 20 includes a treatment container 22, a vibrator 28, and an oscillator 30. The treatment container 22 contains the treatment electrode 50 and the treatment water 32. The treatment container 22 includes an inner tank 24 in which the pretreated electrode 50a is contained, a mounting table 25 on which the inner tank 24 is placed, and an outer tank 26 in which the inner tank 24 and the mounting table 25 are contained. The inner tank 24 contains the treatment water 32, and the outer tank 26 contains an ultrasonic propagation medium 36. The treatment water 32 may include tap water, distilled water, ion-exchanged water, etc. The ultrasonic propagation medium 36 is, for example, water, and serves to propagate ultrasonic waves together with the treatment water 32. The treatment container 22 is provided with piping and valves (not shown) that allow the supply and amount of treatment water 32 to the treatment container 22 to be adjusted. The separation unit 20 has an internal separation unit transport unit (not shown) that stores and discharges the treatment water 32 into the treatment container 22, and immerses and removes the treatment target electrode 50a from the treatment water 32, etc.

[0041] The vibrator 28 is disposed so as to be in contact with the processing vessel 22. The oscillator 30 supplies power to the vibrator 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 vibrator 28 by using the sweep function of the oscillator 30.

[0042] The control unit 15 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a storage device and input / output ports (not shown). The control unit 15 is electrically connected to the pre-processing unit 40, the separation unit 20, etc., and outputs signals to or receives signals from either of these. For example, as shown in FIGS. 4 and 5, the control unit 15 is electrically connected to the oscillator 30 of the separation unit 20, and outputs a signal to the oscillator 30. The control unit 15 is configured to control the oscillator 30 so that ultrasonic processing is performed while sweeping the frequency of the ultrasonic waves. The ultrasonic processing conditions may be the same as those of the separation method described above.

[0043] An example of the operation of the separation device 10 will be described. First, the control unit 15 controls the separation unit transport unit (not shown) to place the immersion liquid 42 in the immersion container 44 of the pretreatment unit 40, immerse the target electrode 50 in the immersion liquid 42, and remove it after a predetermined immersion time has elapsed. The immersion liquid 42 may be any of those described in the separation method. The immersion time may be, for example, 0.1 seconds to 10 minutes. The control unit 15 may then control the immersion liquid removal device (not shown) to remove the immersion liquid 42 from the target electrode 50 removed from the immersion liquid 42. This pretreatment weakens the adhesive strength of the binder contained in the electrode mixture 54, resulting in a pretreated target electrode 50a having an electrode mixture 54a with weakened adhesive strength. Next, the control unit 15 controls the separation unit transport unit (not shown) to place the treated water 32 in the treatment container 22. The treated water may be tap water, distilled water, ion-exchanged water, or the like. Thereafter, the control unit 15 controls the oscillator 30 to supply power to the vibrator 28, causing the vibrator 28 to oscillate. Furthermore, the control unit 15 controls the separation unit internal transport unit (not shown) to immerse the electrode 50a to be treated in the treatment water 32 to which ultrasonic waves have been applied. This causes ultrasonic treatment to be performed on the electrode 50 to be treated in the treatment water 32. For 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 conditions, for example, that the fundamental frequency F0 is 10 kHz or more and 240 kHz or less, the sweep width is within ±5 kHz, and the sweep rate is 500 sweep cycles / second or more. Furthermore, the control unit 15 controls the oscillator 30 to sweep the frequency under the conditions, for example, that the output density B / A is 50 W / cm 2 The control unit 15 controls the oscillator 30 to output the following power. The control unit 15 also 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 this ultrasonic treatment, the current collector 52 and the electrode composite 54 of the treatment target electrode 50 are separated, and composite-containing treated water 33 containing the current collector 52 and the electrode composite 54 is obtained.

[0044] The separation method and separation device described above can separate the current collector and the electrode composite more efficiently. The reason for this effect is presumed to be as follows: In the separation method and separation device described above, the adhesive strength of the binder is weakened in the pretreatment process by utilizing the chemical action of an organic solvent. Then, in the separation process, the current collector and the electrode composite are separated using water, utilizing the physical action of the cavitation effect of ultrasound. Furthermore, water has a high surface tension and is more likely to generate a cavitation effect than organic solvents, allowing for efficient separation of the current collector and the electrode composite. Furthermore, ultrasonic treatment is performed while sweeping the ultrasonic frequency, resulting in a more optimal energy distribution and more efficient separation of the current collector and the electrode composite. Furthermore, since the current collector and the electrode composite can be separated efficiently, there is also an effect that the current collector and the electrode composite can be separated with high precision even at a high frequency (low energy) such as 40 to 240 kHz (preferably 80 to 200 kHz), even when the electrode to be treated is relatively large, and even in a non-heated environment.

[0045] 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.

[0046] For example, in the above-described embodiment, ultrasonic processing is performed while sweeping the frequency of the ultrasonic processing, but ultrasonic processing may be performed without sweeping the frequency of the ultrasonic processing.

[0047] In the above-described embodiment, the transport unit within the pretreatment unit performs the storage and discharge of the immersion liquid 42 into the immersion container 44, and the immersion and removal of the electrode 50 to be treated into the immersion liquid 42, while the transport unit within the separation unit performs the storage and discharge of the treatment water 32 into the treatment container 22, and the immersion and removal of the electrode 50a to be treated into the treatment water 32, but these operations may also be performed by an operator.

[0048] The present disclosure may be implemented as any one of the following items [1] to

[10] . [1] A separation method including: a pretreatment step of applying a pretreatment solution containing an organic solvent to a target electrode including a current collector and an electrode mixture formed on the current collector and containing a binder; and a separation step of immersing the pretreated target electrode in treatment water and subjecting it to ultrasonic treatment to separate the current collector from the electrode mixture. [2] The separation method according to item [1], wherein the pretreatment solution contains 10% by volume or more of the organic solvent. [3] The separation method according to item [1] or [2], wherein the binder is a solvent-based binder. [4] The separation method according to any one of items [1] to [3], wherein the distance between the Hansen solubility parameters of the organic solvent and the binder is smaller than the distance between the Hansen solubility parameters of water and the binder. [5] The separation method according to any one of [1] to [4], wherein, in the pretreatment step, the electrode to be treated is immersed in the pretreatment liquid for an immersion time of 0.1 seconds to 10 minutes. [6] The separation method according to any one of [1] to [5], wherein, in the pretreatment step, the pretreatment liquid is applied to the electrode to be treated, then wiped off, and the pretreatment liquid is removed from the electrode to be treated by air drying or hot air drying. [7] The separation method according to any one of [1] to [6], wherein, in the separation step, the ultrasonic treatment is performed for a period of 10 minutes or less. [8] The separation method according to any one of [1] to [7], wherein, in the separation step, the ultrasonic treatment is performed while sweeping the frequency of the ultrasonic waves. [9] The separation method according to any one of claims [1] to [8], wherein the binder contains polyvinylidene fluoride, and the pretreatment liquid contains one or more of methanol, ethanol, 1-butanol, 1-propanol, 2-propanol, ethylene glycol, acetone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, trimethyl phosphate, 2-pyrrolidone, and chloroform as the organic solvent.

[10] A separation device comprising: a pretreatment unit that applies a pretreatment liquid containing an organic solvent to a treatment target electrode including a current collector and an electrode mixture formed on the current collector and containing a binder, and a separation unit that immerses the treatment target electrode after the pretreatment in treatment water and performs ultrasonic treatment to separate the current collector from the electrode mixture.

[0049] Below, an example of implementing the separation method of the present disclosure will be described. The experiment was conducted according to the procedure shown in Figure 6. Experimental Examples 3 to 13 and 15 to 42 correspond to Examples, and Experimental Examples 1, 2, and 14 correspond to Comparative Examples.

[0050] [Preparation of 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 containing 95% by mass of O2 (NCM) (manufactured by Toda Kogyo Co., Ltd.), 3% by mass of acetylene black (manufactured by Denka) as a conductive material, and 2% by mass of polyvinylidene fluoride (PVDF) (manufactured by Kureha) as a binder was applied to both sides of a 20 μm-thick aluminum current collector foil to form a positive electrode. The positive electrode composite layer had a basis weight of 20 mg / cm per side. 2 The thickness was 60 μm and the area was 20 mm×50 mm.

[0051] [Preparation of Immersion Liquid] The immersion liquids for Experimental Examples 1 to 42 were prepared as follows: (Experimental Example 1) None (Experimental Examples 2 and 14) Pure water was used as is (Experimental Examples 3 and 15) Methanol was used as is (Experimental Examples 4 and 16) Ethanol was used as is (Experimental Examples 5 and 17) 1-butanol was used as is (Experimental Examples 6 and 18) 1-propanol was used as is (Experimental Examples 7, 19, and 43) 2-propanol was used as is (Experimental Examples 8 and 20) Ethylene glycol was used as is (Experimental Examples 9 and 21) Acetone was used as is (Experimental Examples 10 and 22) N-methyl-2-pyrrolidone (NMP) was used as is (Experimental Examples 11 and 23) N,N-dimethylformamide (DMF) was used as is (Experimental Examples 12 and 24) Trimethyl phosphate was used as is. (Experimental Examples 13 and 25) 2-pyrrolidone was used as is. (Experimental Example 26) Chloroform was used as is. (Experimental Examples 27 and 28) Acetone was used as is. (Experimental Example 29) A solution was prepared by mixing 10% by volume of acetone with water. (Experimental Example 30) A solution was prepared by mixing 20% ​​by volume of acetone with water. (Experimental Example 31) A solution was prepared by mixing 50% by volume of acetone with water. (Experimental Example 32) A solution was prepared by mixing 10% by volume of 2-propanol with water. (Experimental Example 33) A solution was prepared by mixing 20% ​​by volume of 2-propanol with water. (Experimental Example 34) A solution was prepared by mixing 30% by volume of 2-propanol with water. (Experimental Example 35) A solution was prepared by mixing 50% by volume of 2-propanol with water. (Experimental Example 36) A solution was prepared by mixing 20% ​​by volume of ethanol with water. (Experimental Example 37) 30% by volume of ethanol was mixed with water to prepare a solution. (Experimental Example 38) 40% by volume of ethanol was mixed with water to prepare a solution. (Experimental Example 39) 50% by volume of ethanol was mixed with water to prepare a solution. (Experimental Example 40) Acetone was used as is. (Experimental Example 41) 2-propanol was used as is. (Experimental Example 42) Ethanol was used as is.

[0052] [Pretreatment] Pretreatment for Experimental Examples 1 to 42 was performed using a petri dish as follows. (Experimental Example 1) No immersion treatment was performed. (Experimental Examples 2 to 13) The electrode to be treated was immersed in the immersion liquid for 1 second, and then the immersion liquid was removed by wiping with a cloth. (Experimental Examples 14 to 26) The electrode to be treated was immersed in the immersion liquid for 60 seconds, and then the immersion liquid was removed by wiping with a cloth. (Experimental Example 27) The electrode to be treated was immersed in the immersion liquid for 300 seconds, and then the immersion liquid was removed by wiping with a cloth. (Experimental Example 28) The electrode to be treated was immersed in the immersion liquid for 60 seconds, and then the immersion liquid was removed by drying with hot air. (Experimental Examples 29 to 42) The electrode to be treated was immersed in the immersion liquid for 60 seconds, and then the immersion liquid was removed by wiping with a cloth.

[0053] The amount of eluted composite material [mg] was calculated from the difference in weight of the electrode before and after immersion. In all of Experimental Examples 1 to 42, elution of the composite material was not confirmed.

[0054] [Ultrasonic Treatment] Using an ultrasonic device (Branson GCX-M-3FQ12, output 500 W, outer tank capacity 20 L), water was placed in the cleaning tank (outer tank), 10 mL of treatment water (pure water) was placed in the glass container of the inner tank, ultrasonic waves were applied from the vibrator below the outer tank, and the electrode to be treated was immersed in the water for the following ultrasonic treatment time. The ultrasonic treatment conditions 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. After ultrasonic treatment, the composite removal rate was calculated using the above-mentioned formula (2). (Experimental Examples 1 to 39) The ultrasonic treatment time was 1 minute. (Experimental Examples 40 to 42) The ultrasonic treatment time was 30 seconds.

[0055] [Results and Discussion] Table 1 shows the composite removal rate for Experimental Examples 1 to 13, Table 2 shows Experimental Examples 14 to 26, and Table 3 shows Experimental Examples 27 to 42. Tables 1 to 3 also show the Hansen solubility parameter (HSP) distance between the organic solvent in the immersion solution and polyvinylidene fluoride (PVDF). The HSP values ​​were referenced in Reference 1 (HANSEN, Charles M. Hansen solubility parameters: a user's handbook. CRC press, 2007.) and Reference 2 (https: / / www.stevenabbott.co.uk / practical-solubility / hsp-basics.php).

[0056] In Experimental Example 1, in which only ultrasonic treatment in water was performed without immersion treatment, and in Experimental Examples 2 and 14, in which ultrasonic treatment in water was performed after immersion treatment in pure water, the composite removal rate was less than 30%. In contrast, in Experimental Examples 3 to 13, in which ultrasonic treatment in water was performed after immersion in an organic solvent for 1 second, and Experimental Examples 15 to 26, in which ultrasonic treatment in water was performed after immersion in an organic solvent for 60 seconds, the composite removal rate was 100%. The separation effect was the same whether the immersion time was 1 second or 60 seconds, so it was found that an immersion time of 1 second is sufficient and that long immersion is not necessary.

[0057] In Experimental Examples 29 to 39, the samples were immersed in an immersion solution containing a mixture of water and either acetone, 2-propanol, or ethanol, followed by ultrasonic treatment in water. For each organic solvent, the higher the concentration in the immersion solution, the higher the composite removal rate. Acetone achieved a 100% composite removal rate at 20%, 2-propanol at 50%, and ethanol at 40%. Acetone has a smaller distance between its Hansen solubility parameters and PVDF than 2-propanol or ethanol, and is effective at dissolving PVDF, presumably resulting in its effectiveness at low concentrations.

[0058] In Experimental Examples 3 to 13 and 15 to 42, an organic solvent was used as the immersion liquid, but the amount of composite eluted into the immersion liquid was 0 mg. For example, even when the electrode was immersed in acetone for a long period of 300 seconds as in Experimental Example 27, the amount of composite eluted was 0 mg. This indicates that immersion in an immersion liquid containing an organic solvent does not separate the composite, but leaves it attached to the current collector foil, and that this state can be transferred to underwater ultrasonic treatment. This makes it possible to avoid the process of separating the composite from the immersion liquid containing an organic solvent in which the electrode was immersed, and it was found that the composite can be recovered from water, which allows for easy post-treatment.

[0059] In Experimental Examples 3 to 13 and 15 to 39, ultrasonic treatment was performed at 80 kHz, 500 W, and 1 minute, and the composite removal rate was 100%. In Experimental Examples 40 to 42, the ultrasonic treatment time was reduced to 30 seconds, but the composite removal rate was also 100%. It was found that the composite could be separated in a short time of less than 1 minute in all cases.

[0060] In Experimental Examples 3 to 13, Experimental Examples 15 to 27, and Experimental Examples 29 to 42, the immersion liquid on the electrode was wiped off with a rag after immersion in an immersion liquid containing an organic solvent, and then underwater ultrasonic treatment was performed. This resulted in more composite material being removed than in Experimental Example 1, which did not involve immersion treatment, and Experimental Examples 2 and 14, which involved immersion treatment in pure water. Furthermore, in Experimental Example 28, the electrode was immersed in an immersion liquid containing an organic solvent, then dried with hot air, and then underwater ultrasonic treatment was performed. This resulted in more composite material being removed than in Experimental Examples 1, 2, and 14. It was found that removing the immersion liquid containing the organic solvent from the electrode after immersion by wiping with a rag, drying, or the like, achieved a separation effect. This immersion liquid removal treatment was found to be preferable because it allowed treatment without introducing organic solvents into the treatment water used for ultrasonic treatment.

[0061]

[0062]

[0063]

[0064] This application claims priority from Japanese Patent Application No. 2023-196573, filed on November 20, 2023, the entire contents of which are incorporated herein by reference.

[0065] The present disclosure is applicable to the field of the battery industry.

[0066] 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, 33 Composite-containing treated water, 36 Ultrasonic propagation medium, 40 Pretreatment unit, 42 Immersion liquid, 44 Immersion container, 50, 50a Electrode to be treated, 52 Current collector, 54, 54a Electrode composite.

Claims

1. A separation method comprising: a pretreatment step of applying a pretreatment liquid containing an organic solvent to a treatment target electrode having a current collector and an electrode mixture formed on the current collector and containing a binder; and a separation step of immersing the pretreated treatment target electrode in treatment water and subjecting it to ultrasonic treatment to separate the current collector and the electrode mixture.

2. The separation method according to claim 1, wherein the pretreatment liquid contains 10% by volume or more of the organic solvent.

3. The separation method according to claim 1 or 2, wherein the binder is a solvent-based binder.

4. The method for separation according to claim 1 or 2, wherein the distance between the Hansen solubility parameters of the organic solvent and the binder is smaller than the distance between the Hansen solubility parameters of water and the binder.

5. A separation method according to claim 1 or 2, wherein in the pretreatment step, the electrode to be treated is immersed in the pretreatment liquid for an immersion time of 0.1 seconds or more and 10 minutes or less.

6. A separation method according to claim 1 or 2, wherein in the pretreatment step, the pretreatment liquid is applied and then wiped off, and then the pretreatment liquid is removed from the electrode to be treated by blowing air or drying with hot air.

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

8. The separation method according to claim 1 or 2, wherein in the separation step, the ultrasonic treatment is carried out while sweeping the frequency of the ultrasonic waves.

9. The separation method according to claim 1 or 2, wherein the binder contains polyvinylidene fluoride, and the pretreatment liquid contains, as the organic solvent, one or more of methanol, ethanol, 1-butanol, 1-propanol, 2-propanol, ethylene glycol, acetone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, trimethyl phosphate, 2-pyrrolidone, and chloroform.

10. A separation device comprising: a pretreatment section that applies a pretreatment liquid containing an organic solvent to a treatment target electrode having a current collector and an electrode mixture formed on the current collector and containing a binder; and a separation section that immerses the treatment target electrode after pretreatment in treatment water and performs ultrasonic treatment to separate the current collector and the electrode mixture.

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