Separation method and separation device

Abstract

To efficiently separate a current collector and an electrode mixture.SOLUTION: A separation method includes a separation step of immersing an electrode 50 to be treated including a current collector 52 and an electrode mixture 54 which is formed on the current collector and contains a binder, in treatment liquid that is a mixture of a water-soluble organic solvent which has a distance of a Hansen solubility parameter with the binder of 8 or less and water and contains 3 vol.% or more of a water-soluble organic solvent, performing ultrasonic treatment while sweeping the frequency of ultrasonic waves, and separating the current collector and the electrode mixture. A separation device 10 includes: a separation part 22 for immersing an electrode to be treated including a current collector and an electrode mixture which is formed on the current collector and contains a binder, in treatment liquid that is a mixture of a water-soluble organic solvent which has a distance of a Hansen solubility parameter with the binder of 8 or less and water and contains 3 vol.% or more of a water-soluble organic solvent, performing ultrasonic treatment, and separating the current collector and the electrode mixture; and a control part 15 for controlling the separation part so that ultrasonic treatment is performed while sweeping the frequency of ultrasonic waves.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Conventionally, as a method for separating a current collector and an electrode mixture in battery recycling, a method of performing ultrasonic treatment while sweeping the frequency of ultrasonic waves in water with respect to the electrode has been proposed (for example, Patent Document 1). In this method, instead of the chemical action of an organic solvent or an aqueous solution, a physical action using the cavitation effect of ultrasonic waves is utilized. And by using water and sweeping the frequency of ultrasonic waves, it is said that the current collector and the electrode mixture can be efficiently and highly accurately separated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described method, when treating an electrode with a thick electrode mixture layer or a high-density electrode, it may take time to separate the current collector and the electrode mixture, and it has been desired to separate the current collector and the electrode mixture more efficiently.

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

Means for Solving the Problems

[0006] In order to achieve the above object, the inventors of the present invention have found that when an electrode having an electrode mixture containing a binder is subjected to ultrasonic treatment while sweeping the frequency of ultrasonic waves in a treatment liquid which is a mixture of a water-soluble organic solvent and water with a Hansen solubility parameter distance from the binder of 8 or less and contains 3% by volume or more of the water-soluble organic solvent, the current collector and the electrode mixture can be separated more efficiently, and thus the present disclosure has been completed.

[0007] That is, the separation method of the present disclosure is as follows. A treatment target electrode including a current collector and an electrode mixture containing a binder formed on the current collector is immersed in a treatment liquid which is a mixture of a water-soluble organic solvent and water with a Hansen solubility parameter distance from the binder of 8 or less and contains 3% by volume or more of the water-soluble organic solvent, and ultrasonic treatment is performed while sweeping the frequency of ultrasonic waves, and the separation step of separating the current collector and the electrode mixture is included.

[0008] Further, the separation device of the present disclosure is as follows. A treatment target electrode including a current collector and an electrode mixture containing a binder formed on the current collector is immersed in a treatment liquid which is a mixture of a water-soluble organic solvent and water with a Hansen solubility parameter distance from the binder of 8 or less and contains 3% by volume or more of the water-soluble organic solvent, and ultrasonic treatment is performed to separate the current collector and the electrode mixture, and a separation unit; A control unit that controls the separation unit so as to perform the ultrasonic treatment while sweeping the frequency of ultrasonic waves; It is provided with.

Advantages of the Invention

[0009] In the separation method and separation device of the present disclosure, the current collector and the electrode composite material can be separated more efficiently. The reason for obtaining such an effect is presumably as follows, for example. In this separation method and separation device, when performing ultrasonic treatment, a treatment liquid containing a water-soluble organic solvent and water is used. The water-soluble organic solvent has a Hansen solubility parameter distance of 8 or less from the binder contained in the electrode composite material, and has an effect of dissolving the binder or weakening the binding force of the binder by its chemical action. Water has a high surface tension and is more likely to generate a cavitation effect than an organic solvent, and thus has an effect of efficiently peeling the electrode composite material from the current collector by the physical action of the cavitation effect. In the present disclosure, by setting the water-soluble organic solvent in the treatment liquid to 3% by volume or more, the synergistic effect of the chemical action of the water-soluble organic solvent and the physical action of water enables efficient separation of the current collector and the electrode composite material. Further, since ultrasonic treatment is performed while sweeping the frequency of the ultrasonic wave, the energy distribution becomes suitable, and the current collector and the electrode composite material can be separated more efficiently.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0011] [Separation Method] The separation method of the present disclosure includes a separation step of immersing a processing target electrode in a processing liquid and performing ultrasonic treatment to separate a current collector and an electrode composite material.

[0012] (Processing Target Electrode) 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 out from a used or deteriorated power storage device. The electrode to be processed may be used as a positive electrode, a negative electrode, or a bipolar electrode having 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 in the state of being taken out from the power storage device without being shredded. For example, it may have an area of 10 cm 2 or more, and may be 30 cm 2 or more.

[0013] 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.

[0014] The electrode mixture may contain an electrode active material, a binder, and a conductive material etc. as required. 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 necessary to increase the electrode density. The electrode mixture may be formed on one side 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 2 , TiS 3 , MoS 3 , FeS 2 , etc., and basic composition formulas such as Li (1-x) MnO 2 (0 < x < 1, etc., the same below) and Li (1-x) Mn2 O 4 such as lithium manganese composite oxides with a basic composition formula of Li (1-x) CoO 2 such as lithium cobalt composite oxides with a basic composition formula of Li (1-x) NiO 2 such as lithium nickel composite oxides with a basic composition formula of Li (1-x) Ni a Co b Mn c O 2 (a + b + c = 1) such as lithium nickel cobalt manganese composite oxides with a basic composition formula of LiV 2 O 3 such as lithium vanadium composite oxides with a basic composition formula of V 2 O 5 Examples of the active materials used for the positive electrode of a lithium - ion secondary battery include transition metal oxides such as those with the formula above, lithium iron phosphate, etc. The electrode active material may include a layered rock - salt - type active material such as lithium nickel cobalt manganese composite oxides among these. Note that the "basic composition formula" means that it may contain other elements such as Al and Mg. Also, examples of the electrode active material include active materials used for the positive electrode and / or negative electrode of a capacitor or a lithium - ion capacitor, such as activated carbons, cokes, vitreous carbons, graphites, non - graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, polyacenes, etc. Further, examples of the electrode active material include active materials used for the negative electrode of a lithium - ion secondary battery, such as lithium alloys, inorganic compounds such as tin compounds, carbonaceous materials capable of occluding and releasing lithium ions, composite oxides containing multiple elements, conductive polymers, etc. Examples of the carbonaceous material include cokes, vitreous carbons, graphites, non - graphitizable carbons, pyrolytic carbons, carbon fibers, etc. Examples of the composite oxide include lithium titanium composite oxides and lithium vanadium composite oxides, etc. Examples of the conductive material contained in the electrode binder include graphites such as natural graphite (scaly graphite, flaky graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fibers, metals (copper, nickel, aluminum, silver, gold, etc.), etc.

[0016] The binder contained in the electrode composite material serves to bind the active material particles and the conductive material particles, and may be a solvent-based binder dissolved in an organic solvent, a water-based binder dissolved in water or various aqueous solutions, or a mixture thereof. Examples of the solvent-based binder include fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber, or thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, and natural butyl rubber (NBR). The solvent-based binder may be a hydrophobic binder. Examples of the water-based binder include polyvinyl alcohol (PVA), styrene-butadiene copolymer (SBR), polyethylene oxide (PEO), etc., and those containing carboxymethyl cellulose (CMC) may also be used. The water-based binder may be a hydrophilic binder. Examples of the organic solvent 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, and may be PVdF. Solvent-based binders such as PVdF are generally hydrophobic, and suppressing the penetration of water into the electrode composite material, etc., is one of the reasons for the time-consuming separation of the current collector and the electrode composite material. Therefore, when the binder is a solvent-based binder, the significance of applying the present disclosure is high. The conductive material contained in the electrode composite material can be used by mixing one or more of, for example, graphite such as natural graphite (scaly graphite, flaky graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.). Among these, from the viewpoints of electron conductivity and coatability, carbon black and acetylene black are preferable as the conductive material.

[0017] The basis weight of the electrode composite material layer is, for example, 10 mg / cm2 It may be as above, 15 mg / cm 2 It may be as above, 20 mg / cm 2 It may be as above. Further, the thickness of the electrode composite layer may be 50 μm or more, may be 55 μm or more, and may be 60 μm or more. Further, the density of the electrode composite layer may be 1.8 g / cm 3 It may be as above, 1.9 g / cm 3 It may be as above, 2.0 g / cm 3 It may be as above, 3.0 g / cm 3 It may be as above. When the basis weight of the electrode composite layer is large, the thickness is thick, or the density is high, etc., water has difficulty penetrating into the electrode composite layer, etc., so it tends to take time to separate the current collector and the electrode composite. Therefore, the significance of applying the present disclosure is high.

[0018] (Separation step) In the separation step, ultrasonic treatment is performed while sweeping the frequency of ultrasonic waves in a state where the electrode to be treated is immersed in the treatment liquid, to separate the current collector and the electrode composite. Sweeping the frequency means, for example, changing the frequency periodically as shown in FIGS. 1 and 2. The ultrasonic treatment may be performed using an ultrasonic probe, but is preferably performed in an ultrasonic bath.

[0019] In the separation step, the frequency of the ultrasonic wave may be periodically changed so as to reciprocate between the maximum frequency Fmax and the minimum frequency Fmin around the fundamental frequency F 0 (see FIGS. 1 and 2). The fundamental frequency F 0 is preferably 10 kHz or more, more preferably 40 kHz or more, and even more preferably 80 kHz or more. The fundamental frequency F 0 is preferably 240 kHz or less, more preferably 200 kHz or less, and may be 100 kHz or less. In the ultrasonic treatment, when the fluctuation width of the frequency centered on the fundamental frequency F 0 is defined as the sweep width (see FIG. 2), the sweep width may be within ±5 kHz. That is, Fmax - F 0 ≤ +5 kHz, Fmin - F 0It may be ≧ -5 kHz. The sweep width may be within ±3 kHz, or may be within ±1 kHz. In ultrasonic processing, one sweep cycle is defined as from the rise of the wave with the minimum frequency Fmin to the fall of the wave with the maximum frequency Fmax (see Fig. 1). When the number of sweep cycles per second is defined as the sweep rate, the sweep rate may be 500 sweep cycles / second or more. The sweep rate may be 700 sweep cycles / second or more, or may be 1000 sweep cycles / second or more. Also, the sweep rate may be 2000 sweep cycles / second or less. Note that one sweep cycle may be defined as half of the period from the rise of the wave with the minimum frequency Fmin to the rise of the next wave with the minimum frequency Fmin.

[0020] In the separation step, it is preferable to perform ultrasonic processing within 30 minutes, more preferably within 10 minutes, and even more preferably within 5 minutes. In the separation step, ultrasonic processing may be performed for 1 second or more, may be performed for 5 seconds or more, or may be performed for 15 seconds or more.

[0021] In the separation step, when the contact area between the current collector and the electrode composite material is A [cm 2 , and the output of the ultrasonic wave (output of the oscillator) is B [W], it is preferable to perform ultrasonic processing so that the output density (power density) represented by B / A is 50 W / cm 2 or less. The output density B / A is preferably 30 W / cm 2 or less, and may be 25 W / cm 2 or less. The output density B / A may be 1 W / cm 2 or more, or may be 5 W / cm 2 or more.

[0022] In the separation step, it is preferable to perform ultrasonic processing in a non-heated environment. In the separation step, for example, ultrasonic processing may be performed within a temperature range of 0°C or more and 30°C or less, or may be performed within a temperature range of 15°C or more and 25°C or less.

[0023] In this separation step, a mixture of a water-soluble organic solvent and water is used as the treatment liquid. The water used in the treatment liquid may be tap water, distilled water, or ion-exchanged water.

[0024] Regarding the water-soluble organic solvent used in the treatment liquid, there is a measure of the effect of promoting the peeling effect of peeling the electrode binder from the current collector in terms of the distance between the solubility parameter values (SP values) of the water-soluble organic solvent and the binder. The closer the distance of the SP values, the higher the compatibility, which means that the binding force of the binder is weakened. The solubility parameter (SP value) is an index indicating how easily the target substance absorbs the solvent. The SP value is divided into three components: the dispersion component (δ D ), the polar component (δ P ), and the hydrogen bond component (δ H ). The parameter shown by dividing into these three components is the Hansen solubility parameter (HSP value). Note that the unit of HSP is MPa 0.5 , but this unit is omitted in this specification. If the value of HSP is δ, then δ 2 = 4δ D 2 + δ P 2 + δ H 2 holds. The value of HSP (δ D , δ P , δ H ) can be considered in three-dimensional coordinates. In the Hansen space represented by three-dimensional coordinates, the closer the HSP value of the target substance and the HSP value of the solvent, the easier the target substance dissolves in the solvent and the higher the compatibility. Therefore, it is considered that the closer the distance of HSP between the water-soluble organic solvent used in the treatment liquid and the binder contained in the electrode binder, the higher the ability of the treatment liquid to weaken the binding force of the binder.

[0025] The distance of HSP between the water-soluble organic solvent used in the treatment liquid and the binder contained in the electrode binder may be 8 or less, preferably 5 or less, more preferably 4 or less, and may be 3.5 or less. For example, when the electrode binder contains polyvinylidene fluoride (PVdF), it is preferable that the distance of HSP between the water-soluble organic solvent contained in the treatment liquid and PVdF is 5 or less.

[0026] Examples of the water-soluble organic solvent used in the treatment liquid include ketones such as acetone, heterocyclic compounds such as N-methyl-2-pyrrolidone and 2-pyrrolidone, and amides such as N,N-dimethylformamide. The water-soluble organic solvent is preferably a polar solvent.

[0027] The concentration of the water-soluble organic solvent in the treatment liquid may be 3% by volume or more, preferably 5% by volume or more, more preferably 10% by volume or more, and may be 20% by volume or more. The concentration of the water-soluble organic solvent in the treatment liquid may be 90% by volume or less, 70% by volume or less, or 50% by volume or less.

[0028] When the separation step described above is performed, the electrode composite material is removed from the current collector, and the electrode composite material removed from the current collector is dissolved and / or dispersed in the treatment liquid or precipitated. Thus, after the ultrasonic treatment, the current collector and the electrode composite material are separated, and the current collector and the composite material-containing treatment liquid containing the electrode composite material are obtained. In addition, as the treatment liquid, a mixture of a water-soluble organic solvent and water with a Hansen solubility parameter distance from the binder of 8 or less and containing 3% by volume or more of the water-soluble organic solvent is used, so that the current collector and the electrode composite material can be separated more efficiently.

[0029] In the separation step, the higher the removal rate of the electrode composite material (hereinafter also referred to as the composite material removal rate), the more preferable. For example, 40% or more is preferable, 50% or more is more preferable, 70% or more is further preferable, and 90% or more is even more preferable. The composite material removal rate [%] can be obtained by calculating the amount of composite material removed [mg] from the weight difference of the electrode before and after the ultrasonic treatment, calculating the initial amount of composite material [mg] from the basis weight and area of the electrode composite material layer in the initial electrode, and using the following formula (1). Composite material removal rate = Amount of composite material removed / Initial amount of composite material × 100 ··· Formula (1)

[0030] Before the separation step, an extraction step of taking out the electrode from the energy storage device may be performed. The electrode taken out in the extraction step may be used as it is without being shredded, or with an area of 10 cm 2 or more, and an area of 30 cm 2It may be cut as described above and used as the electrode to be processed.

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

[0032] The separation step, the current collector treatment step, and the composite material treatment step may be performed in a batch manner or a continuous manner. When the separation step and the current collector treatment step are performed continuously, a roll-to-roll method may be adopted. When the separation step is performed by the roll-to-roll method, the electrodes taken out in the take-out step may be sequentially wound into a roll shape and used as the electrodes to be processed. In addition, since a current collector and an electrode composite material are obtained by this separation method, this separation method is also a method for manufacturing a current collector and a method for manufacturing an electrode composite material.

[0033] [Separator] The separator of the present disclosure includes a separation unit that immerses the electrode to be processed in a treatment liquid and performs ultrasonic treatment to separate the current collector and the electrode composite material, and a control unit that controls the separation unit. In this separator, the above-described separation method may be performed, and the configurations and conditions described in the above-described separation method may be applied.

[0034] Hereinafter, as an example of a separation device, the separation device 10 will be described. FIGS. 3 and 4 show explanatory diagrams showing the outline of the configuration of the separation device 10. FIG. 3 is an explanatory diagram showing the outline of the configuration of the separation device 10 before ultrasonic treatment. FIG. 4 is an explanatory diagram showing the outline of the configuration of the separation device 10 after ultrasonic treatment. The separation device 10 includes a separation unit 20 and a control unit 15. In this separation device 10, ultrasonic treatment is performed on a processing target electrode 50 including a current collector 52 and an electrode binder 54 to separate the current collector 52 and the electrode binder 54. The processing target electrode 50, the current collector 52, and the electrode binder 54 may be the same as the processing target electrode, the current collector, and the electrode binder described in the separation method, respectively.

[0035] The separation unit 20 performs ultrasonic treatment on the processing target electrode 50 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 houses the processing target electrode 50 and the treatment liquid 32. The treatment container 22 includes an inner tank 24 in which the processing target electrode 50 is housed, 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 housed. The treatment liquid 32 is housed in the inner tank 24, and the ultrasonic propagation medium 36 is housed in the outer tank 26. As the treatment liquid 32, a mixture of a water-soluble organic solvent and water is used. The water-soluble organic solvent has an HSP distance from the binder of 8 or less and is contained in the treatment liquid 32 at a ratio of 3% by volume or more. The water may be tap water, distilled water, ion-exchanged water, or the like. The ultrasonic propagation medium 36 is, for example, water and plays a role of propagating ultrasonic waves together with the treatment liquid 32. Pipes and valves (not shown) are provided in the treatment container 22 so that the supply presence / absence and supply amount of the treatment liquid 32 to the treatment container 22 can be adjusted.

[0036] The vibrator 28 is arranged to be in contact with the processing container 22. The oscillator 30 supplies power to the vibrator 28 to oscillate the vibrator 28. 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.

[0037] The control unit 15 is configured as a microprocessor centered on a CPU, and in addition to the CPU, it is equipped with a storage device, input / output ports, etc. not shown in the figure. The control unit 15 is electrically connected to the oscillator 30 and outputs a signal to the oscillator 30. The control unit 15 is configured to control the oscillator 30 so as to perform ultrasonic processing while sweeping the frequency of the ultrasonic waves. The conditions for ultrasonic processing may apply the same conditions as the separation method described above.

[0038] An example of the operation of the separation device 10 will be described. First, the processing liquid 32 is contained in the processing container 22, and the electrode 50 to be processed is immersed in the processing liquid 32. As the processing liquid 32, any one of those described in the above separation method may be used. The control unit 15 controls the oscillator 30 to supply power to the vibrator 28 and oscillate the vibrator 28. Thereby, ultrasonic processing is performed on the electrode 50 to be processed in the processing liquid 32. The control unit 15 may oscillate the vibrator 28 before the electrode 50 to be processed is immersed in the processing liquid 32, or may oscillate the vibrator 28 after the electrode 50 to be processed is immersed in the processing liquid 32. In ultrasonic processing, the control unit 15 uses the sweep function of the oscillator 30. For example, the control unit 15 controls the oscillator 30 to sweep the frequency under the conditions that the basic frequency F 0 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. Also, the control unit 15, for example, has an output density B / A of 50 W / cm 2The oscillator 30 is controlled to output the following power. Further, the control unit 15 controls the oscillator 30 to execute ultrasonic processing for a predetermined time in a range of, for example, 1 second or more and 30 minutes or less. By such ultrasonic processing, the current collector 52 of the processing target electrode 50 and the electrode composite material 54 are separated, and a composite material-containing processing liquid 33 containing the current collector 52 and the electrode composite material 54 is obtained.

[0039] In the separation method and separation device described above, the current collector and the electrode composite material can be separated more efficiently. The reason for obtaining such an effect is presumably as follows, for example. In the separation method and separation device described above, when performing ultrasonic processing, a processing liquid containing a water-soluble organic solvent and water is used. The water-soluble organic solvent has a Hansen solubility parameter distance of 8 or less from the binder contained in the electrode composite material, and has an effect of dissolving the binder or weakening the binding force of the binder by its chemical action. Water has a high surface tension and is more likely to generate a cavitation effect than an organic solvent. Therefore, it has an effect of efficiently peeling the electrode composite material from the current collector by the physical action of the cavitation effect. In the separation method and separation device described above, by setting the water-soluble organic solvent in the processing liquid to 3% by volume or more, the synergistic effect of the chemical action of the water-soluble organic solvent and the physical action of water enables efficient separation of the current collector and the electrode composite material. Further, since ultrasonic processing is performed while sweeping the frequency of the ultrasonic wave, the energy distribution becomes suitable, and the current collector and the electrode composite material can be separated more efficiently. Furthermore, since the current collector and the electrode composite material can be separated efficiently, for example, even at a high frequency (low energy) such as 40 to 240 kHz (preferably 80 to 200 kHz), even if the processing target electrode is relatively large, and even in a non-heated environment, the effect of efficiently separating the current collector and the electrode composite material can be obtained.

[0040] Note that the present disclosure is not limited to the above-described embodiments at all, and it goes without saying that the present disclosure can be implemented in various modes as long as it belongs to the technical scope of the present disclosure.

[0041] For example, in the above-described embodiment, the separation device 10 is configured to perform ultrasonic processing in a batch manner, but it may be configured to perform ultrasonic processing in a continuous manner.

[0042] This disclosure may be as shown in any of [1] to [7] below. [1] A treatment target electrode including a current collector and an electrode mixture containing a binder formed on the current collector is immersed in a treatment liquid which is a mixture of a water-soluble organic solvent and water with a distance of Hansen solubility parameter from the binder of 8 or less and contains 3% by volume or more of the water-soluble organic solvent, and ultrasonic treatment is performed while sweeping the frequency of ultrasonic waves, and the method includes a separation step of separating the current collector and the electrode mixture. [2] The separation method according to [1], wherein the distance of the Hansen solubility parameter of the water-soluble organic solvent from the binder is 5 or less. [3] The separation method according to [1] or [2], wherein the treatment liquid contains the water-soluble organic solvent in a range of 5% by volume or more and 50% by volume or less. [4] The separation method according to any one of [1] to [3], wherein the binder is a solvent-based binder. [5] The separation method according to any one of [1] to [4], wherein the binder is polyvinylidene fluoride, and the water-soluble organic solvent is one or more of acetone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, trimethyl phosphate, and 2-pyrrolidone. [6] The separation method according to any one of [1] to [5], wherein in the separation step, the ultrasonic treatment is performed within 5 minutes to remove 40% by volume or more of the electrode mixture. [7] A treatment target electrode including a current collector and an electrode mixture containing a binder formed on the current collector is immersed in a treatment liquid which is a mixture of a water-soluble organic solvent and water with a distance of Hansen solubility parameter from the binder of 8 or less and contains 3% by volume or more of the water-soluble organic solvent, and ultrasonic treatment is performed, and a separation unit for separating the current collector and the electrode mixture, A separation device including a control unit for controlling the separation unit so as to perform the ultrasonic treatment while sweeping the frequency of ultrasonic waves.

Example

[0043] Examples of the separation method of the present disclosure will be described below. The experiment was conducted according to the procedure shown in FIG. 5. Note that Experimental Examples 20 to 23, 26 to 29, 32 to 35, 38 to 41, and 44 to 47 correspond to Examples, and Experimental Examples 1 to 17, 18 to 19, 24 to 25, 30 to 31, 36 to 37, and 42 to 43 correspond to Comparative Examples.

[0044] [Preparation of the electrode to be processed] As the electrode to be processed, the following positive electrode was prepared. Specifically, as the positive electrode active material, LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM) (manufactured by Toda Kogyo) at 95% by mass, acetylene black (manufactured by Denka) as a conductive material at 3% by mass, and polyvinylidene fluoride (PVdF) (manufactured by Kuraray) as a binder at 2% by mass were applied to both sides of an aluminum current collector foil with a thickness of 20 μm to obtain a positive electrode. Regarding the positive electrode composite layer, the basis weight was 20 mg / cm 2 , the thickness was 60 μm, and the area was 20 mm × 50 mm.

[0045] [Preparation of the treatment liquid] The treatment liquids for Experimental Examples 1 to 47 were prepared as follows. (Experimental Example 1) Pure water was used as it was. (Experimental Examples 2 to 5) Prepared by mixing 5 to 50% by volume of methanol in water. (Experimental Examples 6 to 9) Prepared by mixing 5 to 50% by volume of ethanol in water. (Experimental Examples 10 to 13) Prepared by mixing 5 to 50% by volume of 1-propanol in water. (Experimental Examples 14 to 17) Prepared by mixing 5 to 50% by volume of 2-propanol in water. (Experimental Examples 18 to 23) Prepared by mixing 1 to 50% by volume of acetone in water. (Experimental Examples 24 to 29) Prepared by mixing 1 to 50% by volume of N-methyl-2-pyrrolidone (NMP) in water. (Experimental Examples 30 to 35) Prepared by mixing 1 to 50% by volume of N,N-dimethylformamide (DMF) in water. (Experimental Examples 36 to 41) Prepared by mixing 1 to 50% by volume of trimethyl phosphate in water. (Experimental Examples 42 - 47) 2-Pyrrolidone was mixed with water in a volume ratio of 1 - 50% to prepare the solution.

[0046] [Ultrasonic Treatment] An ultrasonic device (GCX-M-3FQ12 manufactured by Branson, output 500W, outer tank capacity 20L) was used. Water was placed in the cleaning tank (outer tank), 10 mL of the treatment solution was placed in a glass container in the inner tank, ultrasonic waves were applied from the vibrator under the outer tank, and the electrode to be treated was immersed in it for ultrasonic treatment for 5 minutes. The conditions for ultrasonic treatment were a frequency of 80 kHz, an output of 500W, a sweep width of ±1 kHz, and a sweep rate of 1000 sweep cycles / second. After ultrasonic treatment, the composite material removal rate was calculated according to the above formula (1).

[0047] [Results and Discussion] The composite material removal rates for Experimental Examples 1 - 17 are shown in Table 1, Experimental Examples 18 - 35 in Table 2, and Experimental Examples 36 - 47 in Table 3. Tables 1 - 3 also show the distance of the Hansen solubility parameter (HSP) between the water-soluble organic solvent mixed with water and polyvinylidene fluoride (PVdF). The HSP values were referred to from 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).

[0048] In Experimental Example 1 where the treatment solution was water, the composite material removal rate was 35%. In contrast, among the experimental examples where the treatment solution was a mixture of a water-soluble organic solvent and water, in Experimental Examples 2 - 5 with methanol as the water-soluble organic solvent, Experimental Examples 6 - 9 with ethanol, Experimental Examples 10 - 13 with 1-propanol, and Experimental Examples 14 - 17 with 2-propanol, the composite material removal rates were all lower than that in Experimental Example 1. Regarding the influence of the concentration of the water-soluble organic solvent in the treatment solution, when the water-soluble organic solvent was 50% by volume rather than 5% by volume, the composite material removal rate increased slightly.

[0049] On the other hand, among the cases where the treatment liquid was a mixture of a water-soluble organic solvent and water, in Experimental Examples 18-23 where the water-soluble organic solvent was acetone, Experimental Examples 24-29 where NMP was used, Experimental Examples 30-35 where DMF was used, Experimental Examples 36-41 where trimethyl phosphate was used, and Experimental Examples 42-47 where 2-pyrrolidone was used, the composite removal rate was higher than that of pure water when the water-soluble organic solvent was 5% by volume or more, and in all cases when the concentration was 10% by volume or more, 50% or more of the composite was peeled off. The HSP distance between these water-soluble organic solvents and PVdF was 5 or less.

[0050] The reason why the composite removal rate decreased due to the addition of a water-soluble organic solvent in Experimental Examples 2 to 17 was presumed to be as follows: That is, the HSP distance between the water-soluble organic solvents methanol, ethanol, 1-propanol, and 2-propanol and PVdF was large and the chemical action was small, so the effect of improving the strippability due to the water-soluble organic solvent was not obtained, and further, it was presumed that the effect of improving the strippability due to the cavitation effect of water was reduced by mixing the water-soluble organic solvent with water.

[0051] The reason why the composite removal rate decreased due to the addition of a water-soluble organic solvent in Experimental Examples 18-19, 24-25, 30-31, 36-37, and 42-43 was presumed to be as follows: Although the HSP distance between acetone, NMP, DMF, trimethyl phosphate, and 2-pyrrolidone as water-soluble organic solvents and PVdF was small, the proportion of the water-soluble organic solvent was small at 2% by volume or less, so the effect of improving the strippability due to the chemical action of the water-soluble organic solvent was small, and furthermore, it was presumed that the effect of improving the strippability due to the cavitation effect of water was reduced by mixing the water-soluble organic solvent with water.

[0052] In Experimental Examples 20 to 23, 26 to 29, 32 to 35, 38 to 41, and 44 to 47, the reason for the increase in the composite material removal rate by adding a water-soluble organic solvent was speculated as follows. That is, the distance of the HSP between acetone, NMP, DMF, trimethyl phosphate, 2-pyrrolidone as water-soluble organic solvents and PVdF is small, and the ratio of the water-soluble organic solvent is as high as 5% by volume or more. Therefore, it was speculated that the effect of improving the peelability due to the chemical action of the water-soluble organic solvent was sufficient. Also, even if the effect of improving the peelability due to the cavitation effect of water decreased by mixing the water-soluble organic solvent with water, it was speculated that this was because the effect of improving the peelability due to the chemical action of the water-soluble organic solvent exceeded it.

[0053] From the above, it was found that by using a treatment liquid for ultrasonic treatment as a mixture of water and a water-soluble organic solvent, the water-soluble organic solvent having a distance of 8 or less in HSP from the binder, and further setting the ratio of the water-soluble organic solvent in the treatment liquid to 3% or more, the current collector and the electrode composite material can be separated more efficiently.

[0054] [Table 1]

[0055] [Table 2]

[0056] [Table 3]

Industrial Applicability

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

Explanation of Signs

[0058] 10 Separation device, 15 Control unit, 20 Separation unit, 22 Processing container, 24 Inner tank, 25 Mounting table, 26 Outer tank, 28 Vibrator, 30 Oscillator, 32 Processing liquid, 33 Composite material-containing processing liquid, 36 Ultrasonic propagation medium, 50 Electrode to be processed, 52 Current collector, 54 Electrode composite material.

Claims

1. A processing target electrode including a current collector and an electrode composite material containing a binder formed on the current collector is immersed in a treatment liquid which is a mixture of a water-soluble organic solvent having a Hansen solubility parameter distance of 8 or less from the binder and water and contains 3% by volume or more of the water-soluble organic solvent, and ultrasonic treatment is performed while sweeping the frequency of the ultrasonic wave, and the method includes a separation step of separating the current collector and the electrode composite material. Separation method.

2. The separation method according to claim 1, wherein the water-soluble organic solvent has a Hansen solubility parameter distance of 5 or less from the binder.

3. The separation method according to claim 1, wherein the treatment liquid contains the water-soluble organic solvent in a range of 5% by volume or more and 50% by volume or less.

4. The separation method according to any one of claims 1 to 3, wherein the binder is a solvent-based binder.

5. The separation method according to any one of claims 1 to 3, wherein the binder is polyvinylidene fluoride, and the water-soluble organic solvent is one or more of acetone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, trimethyl phosphate, and 2-pyrrolidone.

6. The separation method according to any one of claims 1 to 3, wherein in the separation step, the ultrasonic treatment is performed within 5 minutes to remove 40% by volume or more of the electrode composite material.

7. A separation apparatus including: a separation unit that immerses a processing target electrode including a current collector and an electrode composite material containing a binder formed on the current collector in a treatment liquid which is a mixture of a water-soluble organic solvent having a Hansen solubility parameter distance of 8 or less from the binder and water and contains 3% by volume or more of the water-soluble organic solvent, and performs ultrasonic treatment to separate the current collector and the electrode composite material; and a control unit that controls the separation unit to perform the ultrasonic treatment while sweeping the frequency of the ultrasonic wave. Separation apparatus.

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