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 to be treated including a current collector and an electrode mixture which is formed on the current collector and contains an aqueous binder, in treatment liquid that is a mixture of water and a water-soluble organic solvent, or a mixture of water and a water-soluble surface active agent, performing ultrasonic treatment while sweeping the frequency of ultrasonic waves, and separating the current collector and the electrode mixture. A separation device includes: a separation part for immersing an electrode to be treated including a current collector and an electrode mixture which is formed on the current collector and contains an aqueous binder, in treatment liquid that is a mixture of water and a water-soluble organic solvent, or a mixture of water and a water-soluble surface active agent, performing ultrasonic treatment, and separating the current collector and the mixture; and a control part 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 utilizing the cavitation effect of ultrasonic waves is used. And by using water and sweeping the frequency of ultrasonic waves, it is said that the current collector and the electrode mixture can be separated efficiently and with high precision.

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 separating a current collector and an electrode mixture more efficiently.

Means for Solving the Problems

[0006] In order to achieve the above object, the inventors of the present invention have found that when ultrasonic treatment is performed on an electrode having an electrode mixture containing an aqueous binder in a treatment liquid which is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant while sweeping the frequency of the ultrasonic wave, 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 immersing a treatment target electrode including a current collector and an electrode mixture containing an aqueous binder formed on the current collector in a treatment liquid which is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant, performing ultrasonic treatment while sweeping the frequency of the ultrasonic wave, and including a separation step of separating the current collector and the electrode mixture.

[0008] Further, the separation device of the present disclosure is immersing a treatment target electrode including a current collector and an electrode mixture containing an aqueous binder formed on the current collector in a treatment liquid which is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant to perform ultrasonic treatment, a separation unit for separating the current collector and the electrode mixture, a control unit for controlling the separation unit so as to perform the ultrasonic treatment while sweeping the frequency of the ultrasonic wave, and includes the above.

Effect 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 water, a water-soluble organic solvent, and a water-soluble surfactant is used. Water has a high surface tension and is more likely to generate a cavitation effect than an organic solvent. In addition, the water-soluble organic solvent and the water-soluble surfactant have the effect of enhancing the wettability of the treatment liquid with the electrode composite material, making it easier for the treatment liquid to penetrate into the electrode composite material layer. In the present disclosure, due to these synergistic effects, the current collector and the electrode composite material can be separated efficiently. 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

Embodiments for Carrying Out the Invention

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

[0012] (Treatment 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 left as it is taken out from the power storage device without being shredded. For example, it may have an area of 3 cm 2 or more, and may be 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, for example, formed by mixing an electrode active material, a conductive material, and a binder, adding an appropriate solvent to make it paste-like, applying it to the surface of the current collector and drying it, 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 the basic composition formula is Li (1-x) MnO 2(such as 0 < x < 1, the same applies hereinafter) and Li (1-x) Mn 2 O 4 such as lithium manganese composite oxides, with the basic composition formula Li (1-x) CoO 2 such as lithium cobalt composite oxides, with the basic composition formula Li (1-x) NiO 2 such as lithium nickel composite oxides, with the basic composition formula Li (1-x) Ni a Co b Mn c O 2 (a + b + c = 1) such as lithium nickel cobalt manganese composite oxides, with the basic composition formula LiV 2 O 3 such as lithium vanadium composite oxides, with the basic composition formula V 2 O 5Examples of the active material used for the positive electrode of a lithium ion secondary battery include transition metal oxides such as etc., and lithium iron phosphate. The electrode active material may include an olivine type active material such as lithium iron phosphate among these. Note that the "basic composition formula" means that other elements such as Al and Mg may be included. Further, 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 a plurality of elements, and conductive polymers. 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 oxide and lithium vanadium composite oxide. 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 whisker, needle coke, carbon fiber, metals (copper, nickel, aluminum, silver, gold, etc.).

[0016] The binder contained in the electrode composite material serves to bind the active material particles and the conductive material particles together, and includes an aqueous binder that is dissolved in an aqueous solvent. Examples of the aqueous binder include polyvinyl alcohol (PVA), styrene-butadiene copolymer (SBR), polyethylene oxide (PEO), etc., and those containing carboxymethyl cellulose (CMC) may also be used. Examples of the aqueous solvent include water and various aqueous solutions. The aqueous binder may be a hydrophilic binder. The conductive material contained in the electrode composite material may be, for example, one or a mixture of two or more of graphite such as natural graphite (scaly graphite, flaky graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, metals (copper, nickel, aluminum, silver, gold, etc.). Among these, as the conductive material, carbon black and acetylene black are preferred from the viewpoints of electron conductivity and coatability.

[0017] The electrode composite material may, for example, contain SBR, or may contain SBR and CMC. SBR and CMC may be contained as an aqueous binder in the electrode composite material. The electrode composite material may, for example, contain a carbon material. The carbon material preferably has a graphene structure, such as graphene sheets, carbon nanotubes, fullerenes, and graphites. The carbon material may be contained as a conductive material in the electrode composite material, or may be contained as an active material. Since SBR and the carbon material have relatively low wettability with water, which is one of the reasons for the time-consuming separation between the current collector and the electrode composite material, when the electrode composite material contains these, the significance of applying the present disclosure is high.

[0018] The basis weight of the electrode composite material layer may be, for example, 50 mg / cm 2 or more, 60 mg / cm 2 or more, 70 mg / cm 2 or more, 80 mg / cm 2The above may be sufficient. Further, the thickness of the electrode composite layer may be, for example, 200 μm or more, 300 μm or more, 350 μm or more, or 400 μm or more. Also, the density of the electrode composite layer may be, for example, 1.5 g / cm 3 or more, 1.7 g / cm 3 or more, 1.9 g / cm 3 or more, 2.0 g / cm 3 or more. When the basis weight of the electrode composite layer is large, the thickness is thick, the density is high, etc., water hardly penetrates into the electrode composite layer, and it tends to take time to separate the current collector and the electrode composite. Therefore, the significance of applying the present disclosure is high.

[0019] (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, periodically changing the frequency 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.

[0020] 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 30 kHz or more, and even more preferably 40 kHz or more. The fundamental frequency F 0 is preferably 240 kHz or less, more preferably 200 kHz or less, even more preferably 100 kHz or less, and may be 50 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 Figure 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.

[0021] In the separation step, it is preferable to perform ultrasonic processing within 60 minutes, more preferably within 45 minutes, still more preferably within 30 minutes, and even more preferably within 15 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.

[0022] In the separation step, when the contact area between the current collector and the electrode composite 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 150 W / cm 2 or less. The output density B / A may be 50 W / cm 2 or less, or may be 30 W / cm 2 or less. The output density B / A may be 10 W / cm 2 or more, or may be 50 W / cm 2 or more.

[0023] 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.

[0024] In this separation step, a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant is used as the treatment liquid. The water used in the treatment liquid may be tap water, distilled water, or ion-exchanged water.

[0025] Examples of the water-soluble organic solvent used in the treatment liquid include alcohols such as ethanol, methanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, ethylene glycol, and glycerin; heterocyclic compounds such as N-methyl-2-pyrrolidone (NMP); and ketones such as acetone. The water-soluble organic solvent is preferably a polar solvent.

[0026] Regarding the water-soluble organic solvent used in the treatment liquid, as a measure of the wettability between the treatment liquid and the electrode binder, the solubility parameter (SP value) between the water-soluble organic solvent and the components constituting the electrode binder (e.g., aqueous binder and carbon material) can be used. The closer the distance of the SP value, the higher the compatibility, and an effect of improving the wettability between the solvent and the target substance is expected. The 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 0 ), and the parameter thus shown is the Hansen solubility parameter (HSP). The unit of HSP is MPa 0.5 , but this unit is omitted in this specification. Let the value of HSP be δ, then the equation 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 a three-dimensional coordinate, and in the Hansen space represented by the three-dimensional coordinate, the closer the distance between the HSP of the solvent and the HSP of the target substance, the higher the compatibility between the solvent and the target substance. Therefore, it is considered that the closer the distance of the HSP between the water-soluble organic solvent used in the treatment liquid and the components constituting the electrode binder, the higher the wettability between the treatment liquid and the electrode binder.

[0027] It is preferable that the distance of the Hansen solubility parameter (HSP) between the water-soluble organic solvent used in the treatment liquid and the aqueous binder is smaller than the distance of the HSP between water and the aqueous binder. Further, it is preferable that the distance of the HSP between the water-soluble organic solvent used in the treatment liquid and the carbon material is smaller than the distance of the HSP between water and the carbon material. The binder and the carbon material contained in the electrode mixture have low wettability with water, which is considered to inhibit the penetration of water into the electrode mixture and contribute to lengthening the time required for the separation of the current collector and the electrode mixture. Therefore, by using a water-soluble organic solvent having an HSP distance from the binder or the carbon material smaller than that of water, the wettability between the binder or the carbon material and the treatment liquid is improved, and a large amount of water quickly penetrates into the electrode during ultrasonic treatment, increasing the cavitation effect, thereby presumably shortening the time required for the separation of the current collector and the electrode mixture. The distance of the Hansen solubility parameter between the water-soluble organic solvent and the aqueous binder is preferably 30 or less, more preferably 25 or less, still more preferably 20 or less, and even more preferably 15 or less. For example, when the electrode mixture contains a styrene-butadiene copolymer (SBR), it is preferable that the distance of the HSP between the water-soluble organic solvent used in the treatment liquid and SBR is smaller than the distance of the HSP between water and SBR, and preferably 30 or less. SBR may be included as an aqueous binder in the electrode mixture. Further, for example, when the electrode mixture contains a carbon material, it is preferable that the distance of the HSP between the water-soluble organic solvent used in the treatment liquid and graphene is smaller than the distance of the HSP between water and graphene, and preferably 30 or less. In this case, the carbon material preferably has a graphene structure, such as a graphene sheet, a carbon nanotube, a fullerene, or graphites. The carbon material may be included as a conductive material or as an active material in the electrode mixture.

[0028] The concentration of the water-soluble organic solvent in the treatment liquid is preferably, for example, 0.1% by volume or more, more preferably 0.3% by volume or more, still more preferably 0.5% by volume or more. The concentration of the water-soluble organic solvent in the treatment liquid is preferably, for example, 50% by volume or less, more preferably 20% by volume or less, still more preferably 10% by volume or less, and even more preferably 5% by volume or less.

[0029] As the water-soluble surfactant used in the treatment liquid, for example, an anionic surfactant or a nonionic surfactant can be preferably used. Examples of the anionic surfactant include linear alkylbenzene-based surfactants such as sodium linear alkylbenzene sulfonate, fatty acid-based surfactants such as sodium laurate, and olefin-based surfactants such as sodium α-olefin sulfonate. Examples of the nonionic surfactant include alkylphenol-based surfactants such as polyoxyethylene(10) octylphenyl ether and fatty acid-based surfactants such as polyoxyethylene fatty acid alkanolamide.

[0030] The concentration of the water-soluble surfactant in the treatment liquid is preferably, for example, 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. The concentration of the water-soluble surfactant in the treatment liquid is preferably, for example, 1% by mass or less, more preferably 0.5% by mass or less, and may be 0.3% by mass or less.

[0031] 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. Further, since a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant is used as the treatment liquid, the current collector and the electrode composite material can be separated more efficiently.

[0032] 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 can be used as the electrode to be treated as it is without being shredded, or cut into an area of 3 cm 2 or more, an area of 10 cm 2 or more, an area of 30 cm 2 or more, etc.

[0033] After the separation step, a current collector treatment step of washing and drying the current collector separated in the separation step may be performed. The washing of the current collector may be performed while flowing a washing liquid, or may be performed by immersing it in the washing liquid. Water is preferable as the washing 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 washing 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 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.

[0034] The separation step, the current collector treatment step, and the composite material treatment step may be performed batchwise or continuously. 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 taking-out step may be sequentially wound into a roll shape and used as the electrodes to be treated. In this separation method, since a current collector and an electrode composite material are obtained, this separation method is also a method for manufacturing a current collector and a method for manufacturing an electrode composite material.

[0035] [Separation device] The separation device of the present disclosure includes a separation unit that immerses an electrode to be treated in a treatment liquid and performs ultrasonic treatment to separate a current collector and an electrode composite material, and a control unit that controls the separation unit. In this separation device, the above-described separation method may be performed, and the configurations and conditions described in the above-described separation method may be applied.

[0036] Hereinafter, as an example of the 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 the processing target electrode 50 including the current collector 52 and the electrode composite material 54, and the current collector 52 and the electrode composite material 54 are separated. The processing target electrode 50, the current collector 52, and the electrode composite material 54 may be the same as the processing target electrode, the current collector, and the electrode composite material described in the separation method, respectively.

[0037] 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 water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant is used. The ultrasonic propagation medium 36 is, for example, water, and plays a role of propagating ultrasonic waves together with the treatment liquid 32. The treatment container 22 is provided with pipes and valves (not shown) so that the supply presence or absence and the supply amount of the treatment liquid 32 to the treatment container 22 can be adjusted.

[0038] The vibrator 28 is arranged to contact the treatment container 22. The oscillator 30 supplies power to the vibrator 28 and oscillates the vibrator 28. The oscillator 30 has a sweep function. The sweep function is, for example, a function of periodically changing the frequency as shown in FIGS. 1 and 2. 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.

[0039] The control unit 15 is configured as a microprocessor centered around a CPU, and in addition to the CPU, it is equipped with a storage device, input / output ports, etc. (not shown). 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 wave. As the conditions for ultrasonic processing, the same conditions as the separation method described above may be applied.

[0040] 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 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, and the oscillator 30 is controlled to sweep the frequency. Also, the control unit 15 controls the oscillator 30 to output power such that, for example, the output density B / A is 150 W / cm 2 or less. Further, the control unit 15 controls the oscillator 30 to execute ultrasonic processing for a predetermined time within a range of, for example, 1 second or more and 60 minutes or less. By such ultrasonic processing, the current collector 52 and the electrode composite material 54 of the electrode 50 to be processed are separated, and a composite material-containing processing liquid 33 containing the current collector 52 and the electrode composite material 54 is obtained.

[0041] In the separation method and separation device described above, the current collector and the electrode binder 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 treatment, a treatment liquid containing water, a water-soluble organic solvent, and a water-soluble surfactant is used. Water has a high surface tension and is more likely to generate a cavitation effect than an organic solvent. In addition, the water-soluble organic solvent and the water-soluble surfactant have the effect of enhancing the wettability of the treatment liquid with the electrode binder, making it easier for the treatment liquid to penetrate into the electrode binder layer. In the present disclosure, due to these synergistic effects, the current collector and the electrode binder can be separated efficiently. Note that in the case of 100% organic solvent, although the wettability with the electrode binder is good, since the organic solvent has a lower surface tension and a lower cavitation effect than water, the current collector and the electrode binder cannot be separated efficiently. Therefore, it is necessary to mix the organic solvent with water, and the organic solvent is limited to being water-soluble.

[0042] In addition, 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 binder can be separated more efficiently. Furthermore, since the current collector and the electrode binder can be separated efficiently, for example, even at a high frequency (low energy) such as 10 to 240 kHz, even if the electrode to be treated is relatively large, and even in a non-heated environment, the effect that the current collector and the electrode binder can be separated efficiently can be obtained.

[0043] In addition, since an aqueous binder is used for the electrode binder, even when the concentration of the water-soluble organic solvent in the treatment liquid is low compared to the case where a solvent-based binder is used, the effect of weakening the binding force by the binder can be obtained, and the current collector and the electrode binder can be separated efficiently. Also, since an aqueous binder is used for the electrode binder, even when the distance of the Hansen solubility parameter from the organic solvent is larger than in the case where a solvent-based binder is used, the separation effect is relatively high, and even when a safer alcohol is used as the organic solvent, the current collector and the electrode binder can be separated efficiently. In addition, since an aqueous binder is used for the electrode binder, if the wettability between the treatment liquid and the electrode binder is enhanced, a separation effect can be obtained, and even when a water-soluble surfactant is used instead of the water-soluble organic solvent, the same effect as when the water-soluble organic solvent is used can be obtained.

[0044] Note that the present disclosure is not limited to the above-described embodiments at all, and it goes without saying that various embodiments can be implemented as long as they belong to the technical scope of the present disclosure.

[0045] For example, in the above-described embodiment, the separation device 10 performs ultrasonic treatment in a batch manner, but it may perform ultrasonic treatment in a continuous manner.

[0046] The present disclosure may be any of the following [1] to [7]. [1] A separation method including a separation step of immersing a processing target electrode including a current collector and an electrode mixture containing an aqueous binder formed on the current collector in a processing liquid that is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant, and performing ultrasonic treatment while sweeping the frequency of the ultrasonic wave to separate the current collector and the electrode mixture. [2] The separation method according to [1], wherein the processing liquid is a mixture of water and a water-soluble organic solvent, and the distance between the Hansen solubility parameters of the water-soluble organic solvent and the aqueous binder is smaller than the distance between the Hansen solubility parameters of water and the aqueous binder. [3] The separation method according to [1] or [2], wherein the processing liquid is a mixture of water and a water-soluble organic solvent, and the distance between the Hansen solubility parameters of the water-soluble organic solvent and the aqueous binder is 30 or less. [4] The separation method according to any one of [1] to [3], wherein the processing liquid is a mixture of water and a water-soluble organic solvent, and the concentration of the water-soluble organic solvent in the processing liquid is 0.1% by volume or more and 50% by volume or less. [5] The separation method according to [1], wherein the processing liquid is a mixture of water and a water-soluble surfactant, and the concentration of the surfactant in the processing liquid is 0.01% by mass or more and 1% by mass or less. [6] The aqueous binder contains carboxymethyl cellulose and styrene-butadiene copolymer, and the treatment liquid contains one or more of ethanol, methanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, ethylene glycol, glycerin, N-methyl-2-pyrrolidone, and acetone as the water-soluble organic solvent, or contains one or more of sodium linear alkylbenzene sulfonate, sodium laurate, polyoxyethylene (10) octylphenyl ether, sodium α-olefin sulfonate, and polyoxyethylene fatty acid alkanolamide as the water-soluble surfactant. The separation method according to any one of [1] to [5]. [7] In the separation step, the ultrasonic treatment is performed within 60 minutes. The separation method according to any one of [1] to [6]. [8] A treatment target electrode including a current collector and an electrode composite material containing an aqueous binder formed on the current collector is immersed in a treatment liquid that is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant, and ultrasonic treatment is performed to separate the current collector and the electrode composite material. A separation unit, A control unit that controls the separation unit to perform the ultrasonic treatment while sweeping the frequency of the ultrasonic wave. A separation device comprising.

Example

[0047] Examples of implementing the separation method of the present disclosure will be described below. Note that Experimental Examples 2 to 36 correspond to Examples, and Experimental Example 1 corresponds to a Comparative Example.

[0048] [Preparation of treatment target electrode] As a treatment target electrode, a positive electrode using an aqueous binder was prepared. Specifically, a positive electrode composite material containing 97% by mass of LiFePO 4 (LFP), 0.5% by mass of single-walled carbon nanotubes (SW-CNT) as a conductive material, 0.5% by mass of carboxymethyl cellulose (CMC) as a binder, and 1.5% by mass of styrene-butadiene copolymer (SBR) was applied to one side of an aluminum current collector foil with a thickness of 40 μm to obtain a positive electrode. Regarding the positive electrode composite material layer, the basis weight was 80 mg / cm2 The thickness was 400 μm and the area was 10 mm × 40 mm.

[0049] [Ultrasonic treatment] Using an ultrasonic device (GCX-M-3FQ12 manufactured by Branson, output 500 W, inner tank capacity 20 L), water was put into the cleaning tank (outer tank), 50 mL of the treatment liquid described below was put into the glass container in the inner tank, ultrasonic waves were applied from the vibrator under the outer tank, the electrode to be treated was immersed therein, and the time until the electrode composite layer was completely peeled off was measured visually. And those that did not peel off within 60 minutes were regarded as NG. The conditions for ultrasonic treatment were a frequency of 40 kHz, an output of 500 W, a sweep width of ±1 kHz, and a sweep speed (sweep rate) of 1000 sweep cycles / second.

[0050] [Treatment liquid] The treatment liquids for Experimental Examples 1 to 36 were prepared as follows. (Experimental Example 1) Pure water was used as it was. (Experimental Example 2) Ethanol was mixed with water at 0.1% by volume for preparation. (Experimental Example 3) Ethanol was mixed with water at 0.2% by volume for preparation. (Experimental Example 4) Ethanol was mixed with water at 0.3% by volume for preparation. (Experimental Example 5) Ethanol was mixed with water at 0.4% by volume for preparation. (Experimental Example 6) Ethanol was mixed with water at 0.5% by volume for preparation. (Experimental Example 7) Ethanol was mixed with water at 1% by volume for preparation. (Experimental Example 8) Ethanol was mixed with water at 5% by volume for preparation. (Experimental Example 9) Ethanol was mixed with water at 10% by volume for preparation. (Experimental Example 10) Ethanol was mixed with water at 15% by volume for preparation. (Experimental Example 11) Ethanol was mixed with water at 20% by volume for preparation. (Experimental Example 12) Ethanol was mixed with water at 50% by volume for preparation. (Experimental Example 13) Methanol was mixed with water at 1% by volume for preparation. (Experimental Example 14) 1-Propanol was mixed with water at 1% by volume for preparation. (Experimental Example 15) It was prepared by mixing 1% by volume of 2-propanol in water. (Experimental Example 16) It was prepared by mixing 1% by volume of 1-butanol in water. (Experimental Example 17) It was prepared by mixing 1% by volume of 1-pentanol in water. (Experimental Example 18) It was prepared by mixing 1% by volume of ethylene glycol in water. (Experimental Example 19) It was prepared by mixing 1% by volume of glycerin in water. (Experimental Example 20) It was prepared by mixing 1% by volume of N-methyl-2-pyrrolidone (NMP) in water. (Experimental Example 21) It was prepared by mixing 1% by volume of acetone in water. (Experimental Example 22) It was prepared by mixing 0.1% by mass of sodium linear alkylbenzene sulfonate in water. (Experimental Example 23) It was prepared by mixing 0.2% by mass of sodium linear alkylbenzene sulfonate in water. (Experimental Example 24) It was prepared by mixing 0.5% by mass of sodium linear alkylbenzene sulfonate in water. (Experimental Example 25) It was prepared by mixing 0.1% by mass of sodium laurate in water. (Experimental Example 26) It was prepared by mixing 0.2% by mass of sodium laurate in water. (Experimental Example 27) It was prepared by mixing 0.5% by mass of sodium laurate in water. (Experimental Example 28) It was prepared by mixing 0.01% by mass of polyoxyethylene (10) octyl phenyl ether in water. (Experimental Example 29) It was prepared by mixing 0.05% by mass of polyoxyethylene (10) octyl phenyl ether in water. (Experimental Example 30) It was prepared by mixing 0.1% by mass of polyoxyethylene (10) octyl phenyl ether in water. (Experimental Example 31) It was prepared by mixing 0.2% by mass of polyoxyethylene (10) octyl phenyl ether in water. (Experimental Example 32) It was prepared by mixing 0.5% by mass of polyoxyethylene (10) octyl phenyl ether in water. (Experimental Example 33) A mixed solution of sodium α-olefin sulfonate and polyoxyethylene fatty acid alkanolamide was mixed at 0.013% by mass in water for preparation. (Experimental Example 34) A mixed solution of sodium α-olefin sulfonate and polyoxyethylene fatty acid alkanolamide was mixed at 0.065% by mass in water for preparation. (Experimental Example 35) A mixed solution of sodium α-olefin sulfonate and polyoxyethylene fatty acid alkanolamide was mixed at 0.13% by mass in water for preparation. (Experimental Example 36) A mixed solution of sodium α-olefin sulfonate and polyoxyethylene fatty acid alkanolamide was mixed at 0.26% by mass in water for preparation.

[0051] [Results and Discussion] Table 1 shows the time until the composite layer was completely removed for each of Experimental Examples 1 to 21, and Table 2 shows the same for Experimental Examples 22 to 36. Table 1 also shows the distance of the Hansen solubility parameters (HSP) between the compound mixed with water, graphene, and styrene-butadiene copolymer (SBR). The HSP values of the compound mixed with water and SBR were referred to, for example, 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). The HSP value of graphene was referred to, for example, in Reference 3 (Langmuir 2010, 26 (5), 3208-3213).

[0052] In the ultrasonic treatment in pure water of Experimental Example 1, the composite layer could not be removed even after 60 minutes of treatment. In contrast, in the ultrasonic treatment in the treatment liquid mixed with 0.1% to 50% by volume of the organic solvent in Experimental Examples 2 to 21 and in the ultrasonic treatment in the treatment liquid added with 0.01% to 0.5% by mass of the surfactant in Experimental Examples 22 to 32, the composite layer could be peeled off within 60 minutes in all cases.

[0053] In the cases where the ethanol concentrations in Experimental Examples 2 to 12 were changed to 0.1% by volume to 50% by volume, the peeling rate was faster than that in pure water in all cases, and it was particularly significantly faster between 0.5% by volume and 5% by volume in Experimental Examples 6 to 8. As the reason for the appearance of the concentration range having a large effect of increasing the peeling rate, it was presumed that the peeling rate was determined by the balance between the decrease in the physical action of water due to the mixing of the organic solvent and the increase in the chemical action due to the organic solvent.

[0054] Experimental Examples 13 to 21 are those in which various organic solvents other than ethanol were mixed with water at 1% by volume. In all cases, an effect of increasing the peeling rate compared to pure water was recognized. Also, regarding the difference in the peeling rate due to each organic solvent, the smaller the difference in the HSP value of each organic solvent with the carbon material (graphene) and SBR contained in the electrode, although it did not completely match, a generally faster tendency was recognized. In particular, the effects of ethanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, N-methyl-2-pyrrolidone (NMP), and acetone, whose difference in the HSP value with graphene is 15 or less and whose difference in the HSP value with SBR is 20 or less, were large. From these facts, it was presumed that the peeling rate was increased by mixing an organic solvent with water because the wettability was improved and the penetration of water into the electrode was accelerated due to the chemical action with the electrode caused by the inclusion of the organic solvent in water.

[0055] Experimental Examples 22 to 36 are those in which various surfactants were mixed with water. In all cases, an effect of increasing the peeling rate compared to pure water was recognized. Also, that effect appeared at a lower concentration compared to the organic solvent. It was presumed that this was because the surfactant has a large effect of improving the wettability with the electrode even at a low concentration.

[0056]

Table 1

[0057]

Table 2

Industrial Applicability

[0058] The present disclosure is applicable to the field of the battery industry.

Description of Signs

[0059] 10 Separator, 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 separation method comprising a separation step of immersing a processing target electrode including a current collector and an electrode mixture containing an aqueous binder formed on the current collector in a processing liquid that is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant, performing ultrasonic treatment while sweeping the frequency of the ultrasonic wave, and separating the current collector and the electrode mixture.

2. The separation method according to claim 1, wherein the processing liquid is a mixture of water and a water-soluble organic solvent, and the distance between the Hansen solubility parameters of the water-soluble organic solvent and the aqueous binder is smaller than the distance between the Hansen solubility parameters of water and the aqueous binder.

3. The separation method according to claim 2, wherein the processing liquid is a mixture of water and a water-soluble organic solvent, and the distance between the Hansen solubility parameters of the water-soluble organic solvent and the aqueous binder is 30 or less.

4. The separation method according to claim 1, wherein the processing liquid is a mixture of water and a water-soluble organic solvent, and the concentration of the water-soluble organic solvent in the processing liquid is 0.1% by volume or more and 50% by volume or less.

5. The separation method according to claim 1, wherein the processing liquid is a mixture of water and a water-soluble surfactant, and the concentration of the surfactant in the processing liquid is 0.01% by mass or more and 1% by mass or less.

6. The aqueous binder includes carboxymethyl cellulose and a styrene-butadiene copolymer, and the processing liquid contains one or more of ethanol, methanol, 1-propanol, 2-propanol, 1-butanol, 1-pentanol, ethylene glycol, glycerin, N-methyl-2-pyrrolidone, and acetone as the water-soluble organic solvent, or one or more of sodium linear alkylbenzene sulfonate, sodium laurate, polyoxyethylene (10) octylphenyl ether, sodium α-olefin sulfonate, and polyoxyethylene fatty acid alkanolamide as the water-soluble surfactant. The separation method according to any one of claims 1 to 5.

7. The separation method according to any one of claims 1 to 5, wherein the ultrasonic treatment is performed within 60 minutes in the separation step.

8. A separation unit that immerses a processing target electrode including a current collector and an electrode mixture containing an aqueous binder formed on the current collector in a processing liquid that is a mixture of water and a water-soluble organic solvent or a mixture of water and a water-soluble surfactant, performs ultrasonic treatment, and separates the current collector and the electrode mixture. A control unit that controls the separation unit to perform the ultrasonic treatment while sweeping the frequency of the ultrasonic wave; A separation device comprising the same.

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