Separation method and separation device

Abstract

To efficiently separate a current collector and an electrode mixture.SOLUTION: A separation method includes: a pretreatment step of bonding pretreatment liquid containing an organic solvent to an electrode to be treated including a current collector and an electrode mixture which is formed on the current collector and contains a binder; and a separation step of immersing the electrode to be treated after the pretreatment in treatment water, performing ultrasonic treatment, and separating the current collector and the electrode mixture. A separation device includes: a pretreatment part for bonding pretreatment liquid containing an organic solvent to an electrode to be treated including a current collector and an electrode mixture which is formed on the current collector and contains a binder; and a separation part for immersing the electrode to be treated after the pretreatment in treatment water, performing ultrasonic treatment, and separating the current collector and the electrode mixture.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 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 the main object 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] To achieve the above object, the inventors of the present invention found that when a pretreatment liquid containing an organic solvent is adhered to an electrode and then the electrode is immersed in treated water for ultrasonic treatment, the current collector and the electrode composite material can be separated more efficiently, and thus completed the present disclosure.

[0007] That is, the separation method of the present disclosure is a pretreatment step of adhering a pretreatment liquid containing an organic solvent to a processing target electrode including a current collector and an electrode composite material formed on the current collector and containing a binder; a separation step of immersing the processing target electrode after pretreatment in treated water for ultrasonic treatment to separate the current collector and the electrode composite material; and includes the above.

[0008] Further, the separation device of the present disclosure is a pretreatment unit that adheres a pretreatment liquid containing an organic solvent to a processing target electrode including a current collector and an electrode composite material formed on the current collector and containing a binder; a separation unit that immerses the processing target electrode after pretreatment in treated water for ultrasonic treatment to separate the current collector and the electrode composite material; and is provided with the above.

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, in the pretreatment step, the binding force of the binder is weakened by utilizing the chemical action of the organic solvent. Then, in the separation step, the current collector and the electrode composite material are separated by utilizing a physical action using the cavitation effect of ultrasonic waves, rather than the chemical action of the organic solvent or the aqueous solution. Since water has a large surface tension and is more likely to generate a cavitation effect than an organic solvent, the current collector and the electrode composite material can be separated efficiently by performing ultrasonic treatment with treated water instead of the pretreatment liquid containing an organic solvent.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

[0011] [Separation Method] The separation method of the present disclosure includes a pretreatment step of attaching a pretreatment liquid to the electrode to be treated, and a separation step of immersing the electrode to be treated after pretreatment in treated water and performing ultrasonic treatment to separate the current collector and the electrode composite material.

[0012] (Electrode to be Treated) The electrode to be treated includes a current collector and an electrode composite material formed on the current collector. The electrode to be treated is an electrode of a storage device such as an ion secondary battery such as a lithium-ion secondary battery, an electric double layer capacitor, a hybrid capacitor, or a pseudo-electric double layer capacitor, and may be taken out from a used storage device or a deteriorated storage device. The electrode to be treated may be a positive electrode, a negative electrode, or a bipolar electrode having a positive electrode composite material formed on one surface and a negative electrode composite material formed on the other surface. The electrode to be treated may be in the state of being taken out from the storage device without being shredded. For example, it may have an area of 10 cm 2 or more, and may also 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 include an electrode active material, a binder, and a conductive material, etc. as required. For example, the electrode mixture may be formed 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., lithium manganese composite oxides with a basic composition formula of Li (1-x) MnO 2 (0 < x < 1, etc., the same below) or Li (1-x) Mn 2 O 4 , etc., lithium cobalt composite oxides with a basic composition formula of Li (1-x) CoO 2 , etc., lithium nickel composite oxides with a basic composition formula of Li (1-x) NiO 2 , etc., lithium nickel cobalt manganese composite oxides with a basic composition formula of Li (1-x) Ni a Co b Mn c O 2 (a + b + c = 1), etc., lithium vanadium composite oxides with a basic composition formula of LiV 2 O 3 , etc., and vanadium oxides with a basic composition formula of 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 a layered rock salt type active material such as lithium nickel cobalt manganese composite oxide 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, 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, 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 may be a solvent-based binder that is dissolved in an organic solvent and used, or a water-based binder that is dissolved in water or various aqueous solutions and used, 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. Since the solvent-based binder is generally hydrophobic and suppresses water such as treated water from penetrating into the electrode composite material, which is one of the reasons for the time-consuming separation between the current collector and the electrode composite material, the significance of applying the present disclosure is high when the binder is a solvent-based binder. 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 fibers, metals (copper, nickel, aluminum, silver, gold, etc.). Among these, from the viewpoints of electron conductivity and coatability, carbon black and acetylene black are preferred as the conductive material.

[0017] The electrode composite material may, for example, contain polyvinylidene fluoride (PVDF). Polyvinylidene fluoride may be included as a solvent-based binder in the electrode composite material. Since PVDF has relatively low wettability with water, it suppresses water such as treated water from penetrating into the electrode composite material, which is one of the reasons for the time-consuming separation between the current collector and the electrode composite material. Therefore, when the electrode composite material contains PVDF, the significance of applying the present disclosure is high.

[0018] The basis weight of the electrode composite material layer may be, for example, 10 mg / cm 2 or more, may be 15 mg / cm 2 or more, may be 20 mg / cm 2 or more. Also, the thickness of the electrode composite material layer may be 50 μm or more, may be 55 μm or more, may be 60 μm or more. Also, the density of the electrode composite material layer may be, for example, 1.2 g / cm 3 or more, may be 1.5 g / cm 3 or more, may be 1.6 g / cm 3 or more, may be 3 g / cm 3 or more. When the basis weight of the electrode composite material layer is large, the thickness is thick, the density is high, etc., water such as treated water is less likely to penetrate into the electrode composite material layer, and there is a tendency for the separation between the current collector and the electrode composite material to take time. Therefore, the significance of applying the present disclosure is high.

[0019] (Pretreatment step) In the pretreatment step, a pretreatment liquid containing an organic solvent is attached to the electrode to be treated. In the pretreatment step, the pretreatment liquid may be attached to the electrode to be treated by immersing the electrode to be treated in the pretreatment liquid. Also, in the pretreatment step, the pretreatment liquid may be attached to the electrode to be treated by coating or spraying. In that case, coating or spraying may be performed so as to cover the entire surface of the electrode to be treated with the pretreatment liquid. Note that, hereinafter, the case where the attachment of the pretreatment liquid is performed by immersion will be mainly described, and in some cases, the attachment of the pretreatment liquid by immersion, and the immersion liquid may be referred to as the pretreatment liquid, but appropriately, immersion can be read as the attachment of the pretreatment liquid, and the immersion liquid can be read as the pretreatment liquid. This also applies to the description of the separation device described later. The immersion time may be appropriately set within a range in which the binding force of the binder contained in the electrode composite material can be weakened. For example, it may be 0.1 second or more, 0.5 second or more, or 1 second or more. The immersion time is preferably set within a range in which the current collector and the electrode composite material do not separate in the pretreatment step and the electrode composite material remains attached to the current collector, or within a range in which the electrode composite material components do not elute in the pretreatment step. For example, it may be within 10 minutes, within 5 minutes, or within 1 minute. In the pretreatment step, it is preferable not to perform ultrasonic treatment during immersion. For example, it may be left stationary during immersion.

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

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

[0022] Regarding the organic solvent used in the immersion liquid, the distance between the solubility parameter (SP value) of the organic solvent and the binder in the electrode composite material can be used as a measure of the ability to weaken the binding force of the binder. The solubility parameter 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 thus obtained is called the HSP value (Hansen solubility parameter). The unit of the HSP value is MPa 0.5 , but this unit is omitted in this specification. Let the HSP value 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 three-dimensional coordinates. In the Hansen space represented by the three-dimensional coordinates, the closer the HSP of the target substance is to the HSP of the solvent, the more easily the target substance dissolves in the solvent and the higher the compatibility. Therefore, it is considered that the closer the distance between the HSP of the binder contained in the electrode composite material and the organic solvent used in the immersion liquid is, the higher the ability to weaken the binding force of the electrode composite material.

[0023] The distance between the HSP of the organic solvent used in the immersion liquid and the binder is preferably smaller than the distance between the HSP of water and the binder. The distance between the HSP of the organic solvent and the 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 polyvinylidene fluoride (PVDF), the distance between the HSP of the organic solvent used in the immersion liquid and PVDF is preferably smaller than the distance between the HSP of water and PVDF (32.5), and more preferably 20 or less.

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

[0025] In the pretreatment step, it is desirable to remove the excess immersion liquid from the electrode to be treated after immersion. By removing the immersion liquid, the introduction of the organic solvent into the treated water can be suppressed. The method for removing the immersion liquid may be, for example, wiping, blowing air for drying, or hot air drying. These methods are preferable because the immersion liquid can be easily removed from the electrode.

[0026] (Separation step) In the separation step, the electrode to be treated after the pretreatment step is immersed in treated water and ultrasonic treatment is performed to separate the current collector and the electrode mixture. The ultrasonic treatment may be performed while sweeping the frequency of the ultrasonic wave. 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.

[0027] In the separation step, the fundamental frequency F 0The frequency of the ultrasonic wave may be periodically changed so as to reciprocate between the maximum frequency Fmax and the minimum frequency Fmin around (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 ultrasonic processing, when the fluctuation range 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 0 ≧ -5 kHz may be used. The sweep width may be within ±3 kHz or within ±1 kHz. In ultrasonic processing, from the rise of the wave with the minimum frequency Fmin to the fall of the wave with the maximum frequency Fmax is defined as one sweep cycle (see FIG. 1), and when the number of sweep cycles per second is defined as the sweep rate, the sweep rate may be 500 sweep cycles / second or more. The sweep rate may be 700 sweep cycles / second or more, or 1000 sweep cycles / second or more. Also, the sweep rate may be 2000 sweep cycles / second or less. Note that one sweep cycle may be half from the rise of the wave with the minimum frequency Fmin to the rise of the next wave with the minimum frequency Fmin.

[0028] In the separation step, it is preferable to perform ultrasonic processing within a range of 30 minutes or less, more preferably within a range of 10 minutes or less, even more preferably within a range of 300 seconds or less, and still more preferably within a range of 180 seconds or less. In the separation step, ultrasonic processing may be performed for 1 second or more, 5 seconds or more, or 15 seconds or more.

[0029] 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 (the output of the oscillator) is B [W], the output density (power density) represented by B / A is 50 W / cm2 It is preferable to perform ultrasonic treatment as follows. The output density B / A is 30 W / cm 2 or less, preferably, and it may be 25 W / cm 2 or less. The output density B / A may be 1 W / cm 2 or more, and it may be 5 W / cm 2 or more.

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

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

[0032] 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 water or precipitated. Thus, after ultrasonic treatment, the current collector and the electrode composite material are separated, and the current collector and the composite material-containing treatment water containing the electrode composite material are obtained.

[0033] 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, 25% or more is preferable, 30% or more is more preferable, 50% or more is further preferable, and 70% 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 electrodes before and after ultrasonic treatment, calculating the amount of composite material before separation [mg] by subtracting the above-mentioned elution amount of the composite material from the above-mentioned initial amount of the composite material, and using the following formula (2). Composite material removal rate = Amount of composite material removed / Amount of composite material before separation × 100 ··· Formula (2)

[0034] Before the pretreatment step, an extraction step of extracting the electrodes from the power storage device may be performed. The electrodes extracted in the extraction step may be used as they are without being shredded, or may be cut into an area of 10 cm 2 or more, or an area of 30 cm 2 or more, etc., and used as the electrodes to be processed.

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

[0036] The pretreatment step, 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 extraction step may be sequentially wound into a roll shape and used as the electrodes to be processed. In addition, since the current collector and the electrode composite material are obtained by this separation method, this separation method is also a method for manufacturing the current collector and a method for manufacturing the electrode composite material.

[0037] [Separator] The separation device of the present disclosure includes a pretreatment unit that adheres a processing target electrode to a pretreatment liquid containing an organic solvent, a separation unit that immerses the processing target electrode after pretreatment in processing water and performs ultrasonic treatment to separate a current collector and an electrode composite material, and a control unit that controls the pretreatment unit and 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.

[0038] Hereinafter, as an example of the separation device, the separation device 10 will be described. FIGS. 3 to 5 show explanatory diagrams schematically showing the configuration of the separation device 10. FIG. 4 is an explanatory diagram schematically showing the configuration of the separation device 10 before ultrasonic treatment. FIG. 5 is an explanatory diagram schematically showing the configuration of the separation device 10 after ultrasonic treatment. However, in FIGS. 4 and 5, the pretreatment unit 40 is omitted. As shown in FIG. 3, the separation device 10 includes a pretreatment unit 40, a separation unit 20, and a control unit 15. In this separation device 10, the processing target electrode 50 including the current collector 52 and the electrode composite material 54 is subjected to an immersion treatment of being immersed in the immersion liquid 42 containing an organic solvent in the pretreatment unit 40, and then ultrasonic treatment is performed in the processing water 32 in the separation unit 20 to separate the current collector 52 and the electrode composite material 54. 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.

[0039] The pretreatment unit 40 immerses the processing target electrode 50 in the immersion liquid 42. The pretreatment unit 40 includes an immersion container 44. The immersion container 44 houses the processing target electrode 50 and the immersion liquid 42. The immersion liquid 42 may be a single organic solvent or a mixed liquid of water and an organic solvent. The pretreatment unit 40 may have an immersion liquid removing device that removes the immersion liquid 42 from the processing target electrode 50 taken out from the immersion liquid 42. The immersion liquid removing device may be, for example, a wiping device that wipes the immersion liquid 42 or a drying device that performs blowing drying or warm air drying. The pretreatment unit 40 has a pretreatment unit internal transfer unit (not shown) that performs operations such as storing and discharging the immersion liquid 42 into and from the immersion container 44, and immersing and taking out the processing target electrode 50 into and from the immersion liquid 42. In the pretreatment unit 40, a processed target electrode 50a having an electrode composite material 54a with weakened adhesive force is obtained by the chemical action of the immersion liquid 42.

[0040] The separation unit 20 performs ultrasonic treatment on the electrode 50a to be processed after the pretreatment in the treatment water 32. The separation unit 20 includes a treatment container 22, a vibrator 28, and an oscillator 30. The treatment container 22 houses the electrode 50 to be processed and the treatment water 32. The treatment container 22 includes an inner tank 24 in which the electrode 50a to be processed after the pretreatment is housed, a mounting table 25 on which the inner tank 24 is placed, and an outer tank 26 that houses the inner tank 24 and the mounting table 25. The treatment water 32 is housed in the inner tank 24, and the ultrasonic propagation medium 36 is housed in the outer tank 26. The treatment water 32 may include 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 water 32. The treatment container 22 is provided with pipes and valves (not shown) so that the supply or non-supply and the supply amount of the treatment water 32 to the treatment container 22 can be adjusted. The separation unit 20 has a separation unit internal transfer unit (not shown) that performs operations such as housing and discharging the treatment water 32 into and from the treatment container 22, and immersing and taking out the electrode 50a to be processed in the treatment water 32.

[0041] The vibrator 28 is arranged to contact the treatment 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, 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.

[0042] 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 preprocessing unit 40, the separation unit 20, etc., and outputs signals to any of these or inputs signals from any of these. For example, as shown in FIGS. 4 and 5, the control unit 15 is electrically connected to the oscillator 30 of the separation unit 20 and outputs a signal to the oscillator 30. The control unit 15 is configured to control the oscillator 30 to perform ultrasonic processing while sweeping the frequency of the ultrasonic wave. The conditions for ultrasonic processing may be the same as those of the separation method described above.

[0043] An example of the operation of the separation device 10 will be described. First, the control unit 15 controls a conveyance unit inside the separation unit (not shown) to store the immersion liquid 42 in the immersion container 44 of the preprocessing unit 40, immerse the electrode to be processed 50 in the immersion liquid 42, and take it out after a predetermined immersion time has elapsed. The immersion liquid 42 may use any of those described in the above separation method. The immersion time is, for example, 0.1 second or more and 10 minutes or less. Thereafter, the control unit 15 may control an immersion liquid removal device (not shown) to remove the immersion liquid 42 from the electrode to be processed 50 taken out from the immersion liquid 42. Through such preprocessing, the adhesive force of the binder contained in the electrode composite material 54 is weakened, and the electrode to be processed 50a after preprocessing having the electrode composite material 54a with weakened adhesive force is obtained. Next, the control unit 15 controls a conveyance unit inside the separation unit (not shown) to store the processing water 32 in the processing container 22. The processing water can be tap water, distilled water, ion-exchanged water, etc. Thereafter, the control unit 15 controls the oscillator 30 to supply power to the vibrator 28 and cause the vibrator 28 to oscillate. Further, the control unit 15 controls a conveyance unit inside the separation unit (not shown) to immerse the electrode to be processed 50a in the processing water 32 to which ultrasonic waves are applied. Thereby, ultrasonic processing is performed on the electrode to be processed 50 in the processing water 32. In ultrasonic processing, the control unit 15 uses the sweep function of the oscillator 30, for example, the fundamental frequency F 0The oscillator 30 is controlled to sweep the frequency under the conditions that the frequency 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. Further, the control unit 15 controls the oscillator 30 to output power such that, for example, the output density B / A is 50 W / cm 2 or less. Further, the control unit 15 controls the oscillator 30 to execute ultrasonic treatment for a predetermined time within a range of, for example, 1 second or more and 30 minutes or less. By such ultrasonic treatment, the current collector 52 of the electrode 50 to be processed and the electrode composite material 54 are separated, and the composite material-containing treatment water 33 containing the current collector 52 and the electrode composite material 54 is obtained.

[0044] 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, in the pretreatment step, the chemical action of the organic solvent is used to weaken the binding force of the binder. Then, in the separation step, a physical action using the cavitation effect of ultrasonic waves is used for the separation of the current collector and the electrode composite material, so that the current collector and the electrode composite material can be separated with water. And water has a large surface tension and is more likely to generate a cavitation effect than an organic solvent, so that the current collector and the electrode composite material can be separated efficiently. Further, since the 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. 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 electrode to be processed is relatively large, and even in a non-heated environment, an effect that the current collector and the electrode composite material can be separated with high precision can be obtained.

[0045] It should be noted 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.

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

[0047] In the above-described embodiment, the pretreatment unit internal transfer unit performs operations such as storing and discharging the immersion liquid 42 into and from the immersion container 44, and immersing and removing the electrode 50 to be treated into and from the immersion liquid 42. The separation unit internal transfer unit performs operations such as storing and discharging the treatment water 32 into and from the treatment container 22, and immersing and removing the electrode 50a to be treated into and from the treatment water 32. However, these operations may be performed by an operator.

[0048] The present disclosure may be any of the following [1] to

[10] . [1] A pretreatment step of attaching a pretreatment liquid containing an organic solvent to a processing target electrode including a current collector and an electrode composite material containing a binder formed on the current collector, and immersing the processing target electrode after pretreatment in processing water to perform ultrasonic treatment to separate the current collector and the electrode composite material. A separation method including a separation step. [2] The separation method according to [1], wherein the pretreatment liquid contains 10% by volume or more of the organic solvent. [3] The separation method according to [1] or [2], wherein the binder is a solvent-based binder. [4] The separation method according to any one of [1] to [3], wherein the distance between the Hansen solubility parameters of the organic solvent and the binder is smaller than the distance between the Hansen solubility parameters of water and the binder. [5] The separation method according to any one of [1] to [4], wherein in the pretreatment step, the processing target electrode is immersed in the pretreatment liquid, and the immersion time is 0.1 second or more and 10 minutes or less. [6] The separation method according to any one of [1] to [5], wherein in the pretreatment step, after the pretreatment liquid is attached, it is wiped off, and the pretreatment liquid is removed from the processing target electrode by blowing air drying or warm air drying. [7] The separation method according to any one of [1] to [6], wherein in the separation step, the ultrasonic treatment is performed within a range of 10 minutes or less. [8] The separation method according to any one of [1] to [7], wherein in the separation step, the ultrasonic treatment is performed while sweeping the frequency of the ultrasonic wave. [9] The binder contains polyvinylidene fluoride, and the pretreatment liquid contains at least one of methanol, ethanol, 1-butanol, 1-propanol, 2-propanol, ethylene glycol, acetone, N-methyl-2-pyrrolidone, N,N-dimethylformamide, trimethyl phosphate, 2-pyrrolidone, and chloroform as the organic solvent. The separation method according to any one of claims [1] to [8].

[10] A separation device including a pretreatment unit that attaches a pretreatment liquid containing an organic solvent to a treatment target electrode including a current collector and an electrode composite material containing a binder formed on the current collector, and a separation unit that performs ultrasonic treatment by immersing the treatment target electrode after pretreatment in treatment water to separate the current collector and the electrode composite material.

Example

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

[0050] [Preparation of treatment target electrode] The following positive electrode was prepared as the treatment target electrode. Specifically, a positive electrode composite material containing 95% by mass of LiNi 0.5 Co 0.2 Mn 0.3 O 2 (NCM) (manufactured by Toda Kogyo), 3% by mass of acetylene black (manufactured by Denka) as a conductive material, and 2% by mass of polyvinylidene fluoride (PVDF) (manufactured by Kureha) as a binder was coated on both sides of an aluminum current collector foil with a thickness of 20 μm to form a positive electrode. Regarding the positive electrode composite material layer, the basis weight per side was 20 mg / cm 2 , the thickness was 60 μm, and the area was 20 mm × 50 mm.

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

[0052] [Pretreatment] The pretreatment for Experimental Examples 1 to 42 was carried out as follows using a petri dish. (Experimental Example 1) Immersion treatment was not performed. (Experimental Examples 2 to 13) The electrode to be treated was immersed in the immersion liquid for 1 second and then the immersion liquid was removed by wiping with a tissue. (Experimental Examples 14 to 26) The electrode to be treated was immersed in the immersion liquid for 60 seconds and then the immersion liquid was removed by wiping with a tissue. (Experimental Example 27) The electrode to be treated was immersed in the immersion liquid for 300 seconds and then the immersion liquid was removed by wiping with a tissue. (Experimental Example 28) The electrode to be treated was immersed in the immersion liquid for 60 seconds and then the immersion liquid was removed by drying with warm air. (Experimental Examples 29 to 42) The electrode to be treated was immersed in the immersion liquid for 60 seconds and then the immersion liquid was removed by wiping with a tissue.

[0053] The elution amount [mg] of the composite material was calculated from the weight difference of the electrode before and after immersion. In none of Experimental Examples 1 to 42 was the elution of the composite material confirmed.

[0054] [Ultrasonic treatment] An ultrasonic device (GCX-M-3FQ12 manufactured by Branson, output 500 W, outer tank internal volume 20 L) was used. Water was put into the cleaning tank (outer tank), 10 mL of treated water (pure water) was put into the 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 therein. Ultrasonic treatment was performed over the following ultrasonic treatment time. The conditions for ultrasonic treatment were a frequency of 80 kHz, an output of 500 W, a sweep width of ±1 kHz, and a sweep speed (sweep rate) of 1000 sweep cycles / second. After ultrasonic treatment, the removal rate of the composite material was calculated by the above-mentioned formula (2). (Experimental Examples 1 to 39) The ultrasonic treatment time was 1 minute. (Experimental Examples 40 to 42) The ultrasonic treatment time was 30 seconds.

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

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

[0057] In Experimental Examples 29 to 39, immersion treatment was performed in an immersion liquid that was a mixture of water and either acetone, 2-propanol, or ethanol, followed by ultrasonic treatment in water. For each organic solvent, the higher the concentration in the immersion liquid, the higher the composite removal rate. The composite removal rate was 100% at 20% acetone, 50% 2-propanol, and 40% ethanol. Acetone has a smaller distance between its Hansen solubility parameter and PVDF than 2-propanol or ethanol, and has a dissolving effect on PVDF, so it was presumed to be effective at low concentrations.

[0058] In Experimental Examples 3 to 13 and 15 to 42, an organic solvent was used in the immersion liquid, but the elution amount of the composite material into the immersion liquid was 0 mg. For example, even when the electrode was immersed in acetone for a long time of 300 seconds as in Experimental Example 27, the elution amount of the composite material was 0 mg. From this, it was found that in the immersion in the immersion liquid containing an organic solvent, the composite material remained attached to the current collector foil without being separated, and in that state, it was possible to shift to underwater ultrasonic treatment. Thereby, it was found that the separation operation of the composite material from the immersion liquid containing the organic solvent in which the electrode was immersed could be avoided, and the composite material could be recovered from water, which was easy to post-process.

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

[0060] In all of Experimental Examples 3 to 13, Experimental Examples 15 to 27, and Experimental Examples 29 to 42, after immersion in the immersion liquid containing an organic solvent, the immersion liquid on the electrode was wiped off with a wipe, and then underwater ultrasonic treatment was performed. However, more composite materials could be removed than in Experimental Example 1 where no immersion treatment was performed, Experimental Example 2 where the immersion treatment was performed with pure water, and Experimental Example 14. Further, in Experimental Example 28, after immersion in the immersion liquid containing an organic solvent, the electrode was dried with warm air, and then underwater ultrasonic treatment was performed. However, more composite materials could be removed than in Experimental Example 1, Experimental Example 2, and Experimental Example 14. It was found that a separation effect could be obtained even when the immersion liquid containing an organic solvent was removed from the electrode by wiping with a wipe, drying, etc. after immersion. It was found that performing such an immersion liquid removal treatment was preferable because the treatment water for ultrasonic treatment could be treated without bringing an organic solvent into it.

[0061]

Table 1

[0062]

Table 2

[0063]

Table 3

Industrial Applicability

[0064] The present disclosure is applicable to the field of the battery industry.

Description of Reference Numerals

[0065] 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 water, 33 Composite material-containing processing water, 36 Ultrasonic propagation medium, 40 Pretreatment unit, 42 Immersion liquid, 44 Immersion container, 50, 50a Electrodes to be processed, 52 Current collector, 54, 54a Electrode composite material.

Claims

1. A pretreatment step of attaching a pretreatment liquid containing an organic solvent to a target electrode to be processed, the target electrode being provided with a current collector and an electrode mixture containing a binder formed on the current collector; A separation step of immersing the target electrode after pretreatment in treated water to perform ultrasonic treatment to separate the current collector and the electrode mixture; A separation method comprising the above.

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

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

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

5. The separation method according to Claim 1 or 2, wherein in the pretreatment step, the target electrode is immersed in the pretreatment liquid, and the immersion time is 0.1 second or more and 10 minutes or less.

6. The separation method according to Claim 1 or 2, wherein in the pretreatment step, after the pretreatment liquid is attached, it is wiped off, and the pretreatment liquid is removed from the target electrode by blowing air drying or warm air drying.

7. The separation method according to Claim 1 or 2, wherein in the separation step, the ultrasonic treatment is performed within 10 minutes.

8. The separation method according to Claim 1 or 2, wherein in the separation step, the ultrasonic treatment is performed while sweeping the frequency of the ultrasonic wave.

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

10. A pretreatment unit that attaches a pretreatment liquid containing an organic solvent to a target electrode to be processed, the target electrode being provided with a current collector and an electrode mixture containing a binder formed on the current collector; A separation unit that immerses the target electrode after pretreatment in treated water to perform ultrasonic treatment to separate the current collector and the electrode mixture; A separation device comprising the above.

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