Separation method, separation apparatus, and electrode manufacturing method

Abstract

To separate a current collector and an electrode mixture material more efficiently.SOLUTION: A separation method includes: a heating step of performing a heat treatment within a predetermined heating temperature range of 200°C or higher in an oxygen-containing atmosphere on a processing target electrode including a current collector and an electrode mixture material formed on the current collector and containing a water-based binder; and an ultrasonic step of performing an ultrasonic treatment while sweeping a frequency of ultrasonic waves in a processing liquid on the processing target electrode after the heat treatment to separate the current collector and the electrode mixture material. A separation apparatus includes: a heating unit that performs the heat treatment on the processing target electrode including the current collector and the electrode mixture material formed on the current collector and containing the water-based binder; an ultrasonic unit that performs the ultrasonic treatment in the processing liquid on the processing target electrode after the heat treatment to separate the current collector and the electrode mixture material; and a control unit that controls the heating unit to perform the heat treatment within the predetermined heating temperature range of 200°C or higher in the oxygen-containing atmosphere, and controls the ultrasonic unit to perform the ultrasonic treatment while sweeping the frequency of the ultrasonic waves.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Conventionally, a method for separating the current collector and the electrode composite in battery recycling has been proposed, in which the electrodes are subjected to ultrasonic treatment while sweeping the ultrasonic frequency in water (for example, Patent Document 1). This method utilizes the physical action of the cavitation effect of ultrasound, rather than the chemical action of an organic solvent or aqueous solution. It is claimed that by using water and sweeping the ultrasonic frequency, the current collector and the electrode composite can be separated efficiently and with high precision. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-102744 Summary of the Invention [Problem to be solved by the invention]

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

[0005] The present disclosure has been made to solve such problems, and a main object of the present disclosure is to more efficiently separate the current collector and the electrode mixture. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the present inventors have found that a current collector and an electrode mixture can be efficiently separated by performing a heat treatment on a treatment target electrode having an electrode mixture layer containing an aqueous binder in an oxygen-containing atmosphere at a heating temperature range of 200°C or higher, and then performing an ultrasonic treatment in a treatment solution while sweeping the ultrasonic frequency, and have completed the present disclosure.

[0007] That is, the separation method of the present disclosure includes: a heating step of performing a heat treatment on a target electrode comprising a current collector and an electrode mixture formed on the current collector and containing an aqueous binder, in an oxygen-containing atmosphere at a predetermined heating temperature range of 200°C or higher; an ultrasonic process in which the electrode to be treated after the heat treatment is subjected to ultrasonic treatment in a treatment solution while sweeping ultrasonic frequencies, thereby separating the current collector and the electrode composite; It includes:

[0008] The separation device of the present disclosure also includes: a heating unit for performing a heat treatment on a treatment target electrode including a current collector and an electrode mixture formed on the current collector and including a water-based binder; an ultrasonic unit that performs ultrasonic treatment on the electrode to be treated after the heat treatment in a treatment liquid to separate the current collector and the electrode composite; a control unit that controls the heating unit so that the heat treatment is performed in a predetermined heating temperature range of 200°C or higher under an oxygen-containing atmosphere, and controls the ultrasonic unit so that the ultrasonic treatment is performed while sweeping the frequency of the ultrasonic waves; It is equipped with the following.

[0009] The method for producing an electrode according to the present disclosure further comprises: The method includes an electrode fabrication step in which a new electrode is fabricated using at least one of the electrode mixture and the current collector obtained by the above-described separation method. [Effects of the Invention]

[0010] The separation method and separation device of the present disclosure enable more efficient separation of the current collector and the electrode mixture. Furthermore, the electrode manufacturing method of the present disclosure, in which a new electrode is produced using at least one of the electrode mixture and the current collector obtained by this separation method, enables efficient production of a new electrode from the electrode being treated. The reason for this effect is presumed to be as follows: In this separation method, separation device, and electrode manufacturing method, a heat treatment is performed within a predetermined heating temperature range prior to ultrasonic treatment in a treatment solution. This decomposes at least a portion of the aqueous binder contained in the electrode mixture, thereby reducing the binding strength between the electrode mixture and the current collector and the binding strength between particles (such as active material and conductive material) within the electrode mixture. Furthermore, performing the heat treatment in an oxygen-containing atmosphere promotes oxidative decomposition of the aqueous binder and forms an oxide layer on the surface of the current collector, thereby reducing the adhesion between the electrode mixture and the current collector. It is presumed that these synergistic effects enable efficient separation of the electrode mixture from the current collector. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is an explanatory diagram of a sweep and a sweep cycle. [Figure 2] An explanatory diagram of sweep width. [Figure 3] FIG. 1 is an explanatory diagram showing an outline of the configuration of a separation device 10. [Figure 4] FIG. 2 is an explanatory diagram showing the outline of the configuration of a heating unit 20. [Figure 5] FIG. 2 is an explanatory diagram showing the outline of the configuration of an ultrasound unit 30. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Separation method] The separation method disclosed herein includes a heating step in which a heat treatment is performed on the electrode to be treated, and an ultrasonic step in which the electrode to be treated after the heat treatment is subjected to ultrasonic treatment in a treatment liquid to separate the current collector and the electrode composite.

[0013] (electrode to be treated) The electrode to be processed includes a current collector and an electrode mixture formed on the current collector. The electrode to be processed is an electrode of an ion secondary battery such as a lithium ion secondary battery, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, etc., and may be taken out from a used or deteriorated energy storage device. The electrode to be processed may be a positive electrode, a negative electrode, or a bipolar electrode having a positive electrode mixture formed on one surface and a negative electrode mixture formed on the other surface. The electrode to be processed may be in the state of being taken out from the energy storage device without being shredded. For example, it may have an area of 3 cm ,<000000�>, (1-x) ,

[0016] , (1-x) , (1-x) or more.

[0014] 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.

[0015] The electrode mixture may contain an electrode active material, a binder, and a conductive material etc. as necessary. The electrode mixture may be formed, for example, by mixing an electrode active material, a conductive material, and a binder, adding an appropriate solvent to make it into a paste state, applying and drying it on the surface of the current collector, and compressing it as necessary to increase the electrode density. The electrode mixture may be formed on one side or both sides of the current collector.

[0016] Examples of the electrode active material contained in the electrode mixture include transition metal sulfides such as TiS2, TiS3, MoS3, FeS2, etc., lithium manganese composite oxides with a basic composition formula of Li (1-x) MnO2(0 < x < 1, etc., the same below) or Li (1-x) Mn2O4, etc., lithium cobalt composite oxides with a basic composition formula of Li (1-x) CoO2, etc., lithium nickel composite oxides with a basic composition formula of Li (1-x)Lithium nickel composite oxide such as NiO2, the basic composition formula is Li (1-x) Ni a Co b Mn c Examples of active materials used in the positive electrodes of lithium-ion secondary batteries include lithium-nickel-cobalt-manganese composite oxides with a basic formula such as LiV2O3, transition metal oxides with a basic formula such as V2O5, and lithium iron phosphate. The electrode active material may also include olivine-type active materials such as lithium iron phosphate. The term "basic formula" refers to the inclusion of other elements such as Al and Mg. Examples of electrode active materials include active materials used in the positive and / or negative electrodes of capacitors and lithium-ion capacitors, such as activated carbons, cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, carbon nanotubes, and polyacenes. Examples of electrode active materials include inorganic compounds such as lithium alloys and tin compounds, carbonaceous materials capable of absorbing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Examples of composite oxides include lithium-titanium composite oxide and lithium-vanadium composite oxide. Examples of conductive materials contained in the electrode mixture include graphite such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fibers, and metals (copper, nickel, aluminum, silver, gold, etc.).

[0017] The binder contained in the electrode mixture serves to bind the active material particles and the conductive material particles together, and includes an aqueous binder dissolved in an aqueous solvent. Examples of aqueous binders include polyvinyl alcohol (PVA), styrene-butadiene copolymer (SBR), polyethylene oxide (PEO), and the like, and may also include carboxymethyl cellulose (CMC). Examples of aqueous solvents include water and various aqueous solutions. Examples of the conductive material contained in the electrode mixture include graphite, such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.), or a mixture of two or more of these. Among these, carbon black and acetylene black are preferred as the conductive material from the viewpoints of electronic conductivity and coatability.

[0018] The electrode mixture may contain, for example, SBR, or may contain SBR and CMC. SBR or CMC may be contained in the electrode mixture as an aqueous binder. The electrode mixture may contain, for example, a carbon material. The carbon material is preferably one having a graphene structure, such as a graphene sheet, carbon nanotube, fullerene, or graphite. The carbon material may be contained in the electrode mixture as a conductive material or as an active material. SBR and carbon materials have relatively low wettability with water, which may be one of the reasons why it takes a long time to separate the current collector and the electrode mixture. Therefore, when the electrode mixture contains these materials, it is highly significant to apply the present disclosure.

[0019] The weight of the electrode mixture layer is, for example, 50 mg / cm 2 It may be more than 60 mg / cm 2 It may be more than 70 mg / cm 2 It may be more than 80 mg / cm 2 The thickness of the electrode mixture layer may be, for example, 200 μm or more, 300 μm or more, 350 μm or more, or 400 μm or more. The density of the electrode mixture layer may be, for example, 1.5 g / cm3 It may be more than 1.7 g / cm 3 It may be more than 1.9 g / cm 3 It may be 2.0 g / cm or more. 3 When the electrode mixture layer has a high basis weight, a large thickness, or a high density, the treatment liquid does not easily permeate into the electrode mixture layer, and separation of the current collector and the electrode mixture tends to take time, and therefore, application of the present disclosure is highly significant.

[0020] (Heating process) In the heating step, the electrode to be treated is subjected to heat treatment in an oxygen-containing atmosphere within a predetermined heating temperature range of 200°C or higher. In the heat treatment, the oxygen concentration of the oxygen-containing atmosphere is preferably high from the viewpoint of further increasing separation efficiency, and may be, for example, 1% or higher, 5% or higher, or 10% or higher. The oxygen concentration of the oxygen-containing atmosphere may be 90% or lower, 50% or lower, or 30% or lower. The oxygen concentration of the oxygen-containing atmosphere may be 10% or lower from the viewpoint of suppressing combustion due to heating. The oxygen concentration is defined as the volume fraction of oxygen in the entire gas of the oxygen-containing atmosphere excluding water vapor. The oxygen-containing atmosphere may contain nitrogen in addition to oxygen, or may be air.

[0021] In the heat treatment, the heating temperature range may be 200°C or higher, but from the viewpoint of further increasing the separation efficiency, a higher temperature is preferable, for example, 250°C or higher, or 300°C or higher. In particular, when the oxygen concentration of the oxygen-containing atmosphere is 3% or lower, the heating temperature range is preferably 250°C or higher. From the viewpoint of energy saving and preventing deterioration of the electrode active material and the current collector, a lower heating temperature range is preferable, preferably 600°C or lower, more preferably 550°C or lower, even more preferably less than 500°C, even more preferably 450°C or lower, and even more preferably 400°C or lower.

[0022] In the heat treatment, the heating time may be, for example, 2 minutes or more, 10 minutes or more, or 20 minutes or more, and may be, for example, 24 hours or less, 12 hours or more, or 2 hours or less.

[0023] (Ultrasonic process) In the ultrasonic process, the electrode to be treated after the heat treatment is subjected to ultrasonic treatment while sweeping the ultrasonic frequency in the treatment solution (while immersed in the treatment solution). Sweeping the frequency means periodically changing the frequency, for example, as shown in Figures 1 and 2. Ultrasonic treatment may be performed using an ultrasonic probe, but is preferably performed in an ultrasonic bath.

[0024] In ultrasonic processing, the frequency of the ultrasonic waves may be periodically changed so as to reciprocate between a maximum frequency Fmax and a minimum frequency Fmin, centered on a fundamental frequency F0 (see FIGS. 1 and 2). The fundamental frequency F0 is preferably 10 kHz or higher, more preferably 30 kHz or higher, and even more preferably 40 kHz or higher. The fundamental frequency F0 is preferably 240 kHz or lower, more preferably 200 kHz or lower, and even more preferably 100 kHz or lower, and may be 50 kHz or lower. In ultrasonic processing, when the sweep width is defined as the frequency fluctuation range centered on the fundamental frequency F0 (see FIG. 2), the sweep width may be within ±5 kHz. That is, Fmax - F0 ≦ +5 kHz and Fmin - F0 ≧ -5 kHz may be satisfied. The sweep width may be within ±3 kHz or within ±1 kHz. In ultrasonic processing, one sweep cycle is defined as the period from the rising edge of the wave with the minimum frequency Fmin to the falling edge of the wave with the maximum frequency Fmax (see Figure 1), and the number of sweep cycles per second is defined as the sweep rate. The sweep rate may be 500 sweep cycles / second or more. The sweep rate may be 700 sweep cycles / second or more, or 1000 sweep cycles / second or more. The sweep rate may also be 2000 sweep cycles / second or less. Note that one sweep cycle may be half the period from the rising edge of the wave with the minimum frequency Fmin to the rising edge of the next wave with the minimum frequency Fmin.

[0025] The ultrasonic treatment is preferably carried out for 60 minutes or less, more preferably for 30 minutes or less, even more preferably for 10 minutes or less, and even more preferably for 5 minutes or less. The ultrasonic treatment may be carried out for 1 second or more, 5 seconds or more, or 15 seconds or more.

[0026] Ultrasonic treatment is carried out by increasing the contact area between the current collector and the electrode mixture in A [cm 2 ] and the ultrasonic output (oscillator output) is B [W], the output density (power density) expressed as B / A is 150W / cm 2 It is preferable to perform ultrasonic treatment so that the power density B / A is 50 W / cm. 2 It may be less than 30W / cm 2 The power density B / A can be 10 W / cm or less. 2 More than 50W / cm 2 It may be more than that.

[0027] The ultrasonic treatment is preferably carried out in a non-heated environment, for example, in a temperature range of 0°C to 30°C, or in a temperature range of 15°C to 25°C.

[0028] The treatment liquid may be an aqueous treatment liquid such as an aqueous solution or water, or may be an organic treatment liquid such as a solution containing an organic solvent or an organic solvent. From the viewpoint of improving the cavitation effect of ultrasonic waves and reducing the environmental load, the treatment liquid is preferably an aqueous treatment liquid, and more preferably water.

[0029] In the separation method described above, the electrode mixture is removed from the current collector, and the electrode mixture removed from the current collector is dissolved and / or dispersed in the treatment liquid, or precipitates. Thus, after ultrasonic treatment, the current collector and the electrode mixture are separated, and the current collector and a mixture-containing treatment liquid containing the electrode mixture are obtained. The mixture-containing treatment liquid may be separated into a solid phase containing the electrode mixture and a liquid phase by a solid-liquid separation technique such as filtration or centrifugation.

[0030] The electrode mixture removal rate (peeling rate) from the current collector by this separation method is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more.

[0031] This separation method may be carried out batchwise or continuously. When this separation method is carried out continuously, a roll-to-roll method may be adopted. Note that this separation method produces a current collector and an electrode mixture, and therefore this separation method is also a method for producing a current collector and an electrode mixture.

[0032] Before the heating step, a removal step of removing the electrode from the electricity storage device may be performed. The electrode removed in the removal step may be left as is without being shredded, or may be cut into pieces with an area of ​​3 cm. 2 The electrode may be cut into the above-mentioned shapes and used as a target electrode. Furthermore, before the heating step, a removal treatment may be performed to remove organic solvents contained in the electrode (for example, organic solvents originating from the electrolyte of the electricity storage device). The removal treatment may be a heating treatment under an inert atmosphere.

[0033] [Separation device] The separation device of the present disclosure includes a heating unit that performs a heat treatment on the electrode to be treated, an ultrasonic unit that performs an ultrasonic treatment on the electrode to be treated after the heat treatment in a treatment liquid to separate the current collector and the electrode composite, and a control unit that controls the heating unit and the ultrasonic unit. This separation device may perform the above-mentioned separation method, and the configurations and conditions described in the above-mentioned separation method may be applied.

[0034] Hereinafter, a separation device 10 will be described as an example of a separation device according to the present disclosure. FIG. 3 is an explanatory diagram showing an outline of the configuration of the separation device 10. As shown in FIG. 3, the separation device 10 includes a heating unit 20, an ultrasonic unit 30, and a control unit 15 that controls the entire separation device 10. FIG. 4 is an explanatory diagram showing an outline of the configuration of the heating unit 20. FIG. 5 is an explanatory diagram showing an outline of the configuration of the ultrasonic unit 30. FIG. 5A is an explanatory diagram showing an outline of the configuration of the ultrasonic unit 30 before ultrasonic treatment. FIG. 5B is an explanatory diagram showing an outline of the configuration of the ultrasonic unit 30 after ultrasonic treatment. The separation device 10 treats a target electrode 50 including a current collector 52 and an electrode mixture 54 containing an aqueous binder, thereby separating the current collector 52 from the electrode mixture 54. The target electrode 50, the current collector 52, and the electrode mixture 54 may be the same as the target electrode, the current collector, and the electrode mixture described in the separation method described above, respectively.

[0035] The heating unit 20 is configured as a heat treatment device that heats the electrode 50 to be treated at a predetermined temperature of 200° C. or higher in an oxygen-containing atmosphere. As shown in Fig. 4, the heating unit 20 has a treatment chamber 22 equipped with a heating element 21, and is configured so that the interior of the treatment chamber 22 becomes a predetermined oxygen-containing atmosphere by introducing an oxygen-containing gas through a gas inlet pipe 24 and discharging it through a gas outlet pipe 26.

[0036] The ultrasonic unit 30 is configured as an ultrasonic processing device that performs ultrasonic processing on the heated electrode 50A to be processed in a processing liquid 42. As shown in FIG. 5 , the ultrasonic unit 30 includes a processing container 32, a vibrator 38, and an oscillator 40. The processing container 32 accommodates the electrode 50A to be processed and the processing liquid 42. The processing container 32 includes an inner tank 34 that accommodates the electrode 50A to be processed, a mounting table 35 on which the inner tank 34 is placed, and an outer tank 36 that accommodates the inner tank 34 and the mounting table 35. The inner tank 34 accommodates the processing liquid 42, and the outer tank 36 accommodates an ultrasonic propagation medium 46. Water, for example, is used as the processing liquid 42. The processing liquid 42 may be tap water, distilled water, ion-exchanged water, or the like. The ultrasonic propagation medium 46 is, for example, water, and functions to propagate ultrasonic waves together with the processing liquid 42. The processing vessel 32 is provided with piping and valves (not shown), which allow adjustment of whether or not the processing liquid 42 is supplied to the processing vessel 32 and the amount of supply. The vibrator 38 is arranged in contact with the processing vessel 32. The oscillator 40 supplies power to the vibrator 38 to cause it to oscillate. The oscillator 40 has a sweep function. The sweep function is a function of periodically changing the frequency, as shown in FIGS. 1 and 2, for example. The ultrasonic unit 30 is configured to be able to sweep (periodically change) the frequency of the ultrasonic waves generated from the oscillator 38 by using the sweep function of the oscillator 40.

[0037] The control unit 15 is configured as a microprocessor centered on a CPU, and in addition to the CPU, includes a storage device and input / output ports (not shown). The control unit 15 is electrically connected to the heating element 21 of the heating unit 20 and the oscillator 40 of the ultrasonic unit 30, and outputs signals to and receives signals from either of these. The control unit 15 is configured to control the heating element 21 so that the processing chamber 22 of the heating unit 20 reaches a predetermined temperature. The heating conditions may be the same as those in the separation method described above. The control unit 15 is also configured to control the oscillator 40 of the ultrasonic unit 30 so that ultrasonic processing is performed while sweeping the ultrasonic frequency. The ultrasonic processing conditions may be the same as those in the separation method described above.

[0038] An example of the operation of the separation device 10 will be described. First, the control unit 15 controls the heating element 21 to generate heat so that the processing chamber 22 of the heating unit 20 is heated within a predetermined heating temperature range. Once the processing chamber 22 reaches the predetermined heating temperature range, an oxygen-containing gas is introduced into the processing chamber 22 through the gas inlet pipe 24, and the processing target electrode 50 is placed in the processing chamber 22 and heated for a predetermined period of time. The oxygen-containing gas may be any of the oxygen-containing atmospheres described in the separation method above. The oxygen concentration of the oxygen-containing atmosphere may be, for example, 1% to 30%. The heating temperature range may be, for example, 200°C to 400°C. The heating time may be, for example, 2 minutes to 2 hours. This heating process is thought to decompose at least a portion of the aqueous binder contained in the electrode mixture 54 of the processing target electrode 50, resulting in an electrode mixture 54A in which the binding strength between the electrode mixture 54 and the current collector 52 and the binding strength between particles within the electrode mixture 54 are reduced. In this way, the heated treatment target electrode 50A having the electrode mixture 54A is obtained.

[0039] Next, the processing vessel 32 is filled with a processing liquid 42, and the heated electrode 50A to be processed is immersed in the processing liquid 42. The processing liquid 42 may be any of those described in the separation method above. After the electrode 50A to be processed is immersed in the processing liquid 42, the control unit 15 controls the oscillator 40 to supply power to the vibrator 38, causing the vibrator 38 to oscillate. This performs ultrasonic processing on the electrode 50A to be processed in the processing liquid 42. For ultrasonic processing, the control unit 15 uses the sweep function of the oscillator 40 to control the oscillator 40 to sweep the frequency under the conditions, for example, that the fundamental frequency F0 is 10 kHz or more and 240 kHz or less, the sweep width is within ±5 kHz, and the sweep rate is 500 sweep cycles / second or more. Furthermore, the control unit 15 controls the oscillator 40 to sweep the frequency under the conditions, for example, that the power density B / A is 150 W / cm 2 The control unit 15 controls the oscillator 40 to output a power equal to or less than the following: Furthermore, the control unit 15 controls the oscillator 40 to perform the ultrasonic treatment for a predetermined time, for example, in the range of 1 second to 60 minutes. By such ultrasonic treatment, the current collector 52 and the electrode composite 54A of the treatment target electrode 50A are separated, and a composite-containing treatment solution 43 containing the current collector 52 and the electrode composite 54A is obtained.

[0040] The separation method and separation device described above enable more efficient separation of the current collector and the electrode composite. The reason for this effect is presumed to be, for example, as follows: In this separation method and separation device, ultrasonic treatment is performed in a treatment solution. Since the ultrasonic treatment is performed while sweeping the ultrasonic frequency, the energy distribution is optimized, enabling efficient separation of the current collector and the electrode composite. Furthermore, prior to the ultrasonic treatment in the treatment solution, heat treatment is performed within a predetermined heating temperature range. This decomposes at least a portion of the aqueous binder contained in the electrode composite, reducing the binding strength between the electrode composite and the current collector and the binding strength between particles (such as active material and conductive material) within the electrode composite. Furthermore, heat treatment in an oxygen-containing atmosphere promotes oxidative decomposition of the aqueous binder and forms an oxide layer on the surface of the current collector, thereby reducing the adhesion between the electrode composite and the current collector. It is presumed that these synergistic effects enable efficient separation of the current collector and the electrode composite. This allows efficient separation of the current collector and the electrode mixture, even when a thick electrode to be treated, for example, with an electrode mixture layer of 50 μm or more, is used.

[0041] Furthermore, the above-described separation method and separation device can efficiently separate the current collector and electrode composite even at low temperatures compared to when heat treatment is performed in an oxygen-free atmosphere, thereby reducing CO2 emissions and energy consumption. Furthermore, by using a low heat treatment temperature, deterioration of the separated electrode composite (or the active material and conductive material contained in the electrode composite) and the current collector can be suppressed, making them suitable for direct recycling. While electrode active materials such as LiFePO4 can oxidize when heated in an oxygen-containing atmosphere, heat treatment at low temperatures, such as 300°C or below, is thought to minimize deterioration due to oxidation.

[0042] Furthermore, the separation method and separation device described above treat an electrode having an electrode mixture containing an aqueous binder. While the electrode mixture containing an aqueous binder is often formed into a thick film of, for example, 50 μm or more, the separation method and separation device described above can efficiently separate the current collector and the electrode mixture even when the electrode mixture layer is a thick film of, for example, 50 μm or more.

[0043] Furthermore, since the above-described separation method and separation device can obtain an electrode mixture or a current collector, at least one of these can be used to produce a new electrode (the electrode manufacturing method of the present disclosure). The electrode mixture or current collector separated by the above-described separation method or separation device may be used as is to produce an electrode, or an active material or a conductive material may be separated from the electrode mixture and used, or specific components may be separated from the active material or conductive material and used.

[0044] It goes without saying that the present disclosure is not limited to the above-described embodiments, and can be embodied in various forms as long as they fall within the technical scope of the present disclosure.

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

[0046] The present disclosure may be any of the following [1] to

[10] . [1] A separation method comprising: a heating step of subjecting a target electrode, which comprises a current collector and an electrode composite formed on the current collector and containing an aqueous binder, to heat treatment in an oxygen-containing atmosphere within a predetermined heating temperature range of 200°C or higher; and an ultrasonic step of subjecting the target electrode after the heat treatment to ultrasonic treatment while sweeping ultrasonic frequencies in a treatment solution, thereby separating the current collector and the electrode composite. [2] The separation method according to [1], wherein in the heating step, the heat treatment is carried out in a heating temperature range of 250°C or higher when the oxygen concentration of the oxygen-containing atmosphere is 3% or lower. [3] The separation method according to [1] or [2], wherein in the heating step, the heat treatment is carried out in an oxygen-containing atmosphere with an oxygen concentration of 1% or more. [4] The separation method according to any one of [1] to [3], wherein in the heating step, the heating treatment is carried out at a heating temperature range of 400° C. or less. [5] The separation method according to any one of [1] to [4], wherein in the heating step, the heating treatment is carried out for 2 minutes or more. [6] The separation method according to any one of [1] to [5], wherein the electrode to be treated contains a styrene-butadiene copolymer and carboxymethyl cellulose as the aqueous binder. [7] The separation method according to any one of [1] to [6], wherein the electrode to be treated has a layer of the electrode mixture having a thickness of 50 μm or more. [8] The separation method according to any one of [1] to [7], wherein the electrode to be treated contains LiFePO4 as an electrode active material. [9] A separation device comprising: a heating unit that performs a heat treatment on a target electrode comprising a current collector and an electrode composite formed on the current collector and containing an aqueous binder; an ultrasonic unit that performs an ultrasonic treatment on the target electrode in a treatment liquid after the heat treatment to separate the current collector from the electrode composite; and a control unit that controls the heating unit to perform the heat treatment within a predetermined heating temperature range of 200°C or higher in an oxygen-containing atmosphere, and controls the ultrasonic unit to perform the ultrasonic treatment while sweeping the frequency of the ultrasonic waves.

[10] A method for producing an electrode, comprising an electrode production step of producing a new electrode using at least one of the electrode mixture and the current collector obtained by the separation method according to any one of [1] to [8]. [Example]

[0047] Examples of carrying out the separation method of the present disclosure will be described below, with Experimental Examples 4 to 32 corresponding to working examples of the present disclosure, and Experimental Examples 1 to 3 and 33 to 38 corresponding to comparative examples.

[0048] (electrode to be treated) A positive electrode using an aqueous binder was prepared as the electrode to be treated. Specifically, a positive electrode composite containing 97.5% by mass of LiFePO4 (LFP), 0.5% by mass of single-walled carbon nanotubes (SW-CNT), 0.5% by mass of carboxymethyl cellulose (CMC), and 1.5% by mass of styrene-butadiene copolymer (SBR) was applied to one side of a 40 μm-thick aluminum current collector to prepare the positive electrode. The positive electrode composite layer had a basis weight of 80 mg / cm. 2 The thickness was 400 μm and the area was 10 mm × 40 mm.

[0049] (heat treatment) A circular furnace equipped with a 30 mm diameter quartz tube was used. A cathode (10 mm x 40 mm) was placed on a quartz boat, which was then inserted into a soaking zone while atmospheric gas was flowing at 500 mL / min. Heat treatment was performed at a predetermined heating temperature of 100 to 350 °C for a predetermined time of 2 to 60 minutes. The atmospheric gas was a mixture of nitrogen and oxygen mixed using a mass flow controller to adjust the oxygen concentration to 20%, 10%, 5%, 3%, 2%, 1%, or 0%. The nitrogen used had a purity of over 99.999% and a moisture content with a dew point below -70 °C. The oxygen used had a purity of over 99.5% and a moisture content with a dew point below -70 °C.

[0050] (ultrasonic treatment) Using an ultrasonic device (Branson GCX-M-3FQ12, output power 500W, cleaning tank capacity 20L), water was placed in the outer cleaning tank, 50ml of water was placed in the glass container of the inner tank, and the heat-treated positive electrode (area 10mm x 40mm) was placed therein. Ultrasonic waves were immediately applied from the transducer below the outer tank. The ultrasonic treatment conditions were an ultrasonic frequency (fundamental frequency F0) of 40kHz, output power 500W, sweep width ±1kHz, and sweep speed 1000 sweep cycles / second. This ultrasonic treatment was performed for up to 60 minutes, and the time until the composite layer was completely peeled was measured. Peeling of the composite layer was confirmed visually. Complete peeling of the composite layer within 60 minutes of ultrasonic treatment was evaluated as ○. For samples that did not completely peel after 60 minutes of ultrasonic treatment, peeling rates of 80% or more were evaluated as △, and those less than 80% were evaluated as ×.

[0051] (Results and Discussion) The heat treatment conditions (oxygen concentration, temperature, time), ultrasonic treatment time, and evaluation results are shown in Tables 1 and 2. In Experimental Example 1, which was not subjected to heat treatment, the peeling rate of the composite layer was less than 80% even after 60 minutes of ultrasonic treatment.

[0052] In Experimental Examples 2 to 7, in which heat treatment was performed for 60 minutes at an oxygen concentration of 20%, the composite layer could be completely peeled off with a short ultrasonic treatment when heat treatment was performed at 200°C or higher, but the composite layer peeling rate was less than 80% even after 60 minutes of ultrasonic treatment when heat treatment was performed at 150°C or lower. In Experimental Examples 8 to 12, in which heat treatment was performed at 300°C with an oxygen concentration of 20%, there was a tendency that the shorter the heat treatment time, the longer the ultrasonic treatment time until the composite layer was completely peeled off. However, in all cases (for example, even when the heat treatment time was 2 minutes or less), the composite layer could be completely peeled off with ultrasonic treatment within 60 minutes.

[0053] In Experimental Examples 13 to 16, in which heat treatment was performed for 60 minutes at an oxygen concentration of 10%, and Experimental Examples 17 to 20, in which heat treatment was performed for 60 minutes at an oxygen concentration of 5%, the composite layer was able to be completely peeled off with short ultrasonic treatment by performing heat treatment at 200°C or higher, just as when heat treatment was performed at an oxygen concentration of 20%.

[0054] In Experimental Examples 21 to 24, in which heat treatment was performed for 60 minutes at an oxygen concentration of 3%, Experimental Examples 25 to 28, in which heat treatment was performed for 60 minutes at an oxygen concentration of 2%, and Experimental Examples 29 to 30, in which heat treatment was performed for 60 minutes at an oxygen concentration of 1%, the composite layer could be completely peeled off with a relatively short ultrasonic treatment of less than 60 minutes when heat treatment was performed at 250°C or higher, but the composite layer could not be completely peeled off with 60 minutes of ultrasonic treatment when heat treatment was performed at 200°C or lower. However, the peeling rate of the composite layer after 60 minutes of ultrasonic treatment was relatively high, at over 80%.

[0055] In Experimental Examples 33 to 38, in which heat treatment was performed for 60 minutes at an oxygen concentration of 0%, the effect of the heat treatment was small, and it was not possible to remove 80% or more of the composite layer, particularly when heated at 250°C or below. When heat treatment was performed at 300°C or above, the composite layer could be completely peeled off with ultrasonic treatment for 60 minutes or less, but a longer ultrasonic treatment time was required compared to when heat treatment was performed in an oxygen-containing atmosphere.

[0056] As explained above, the peeling efficiency improved when the heating treatment was performed in an oxygen-containing atmosphere followed by ultrasonic treatment. This effect was presumably due to the oxidative decomposition of part of the CMC in the electrode composite, which reduced the adhesive strength between the electrode composite and the current collector, as well as between the active material and conductive material in the composite. The effect was presumably greater the higher the oxygen concentration.

[0057] [Table 1]

[0058] [Table 2] [Industrial Applicability]

[0059] The present disclosure is applicable to the field of the battery industry. [Explanation of symbols]

[0060] 10 Separation device, 15 Control unit, 20 Heating unit, 21 Heating element, 22 Treatment chamber, 24 Gas inlet pipe, 26 Gas outlet pipe, 30 Ultrasonic unit, 32 Treatment container, 34 Inner tank, 35 Mounting table, 36 Outer tank, 38 Vibrator, 40 Oscillator, 42 Treatment liquid, 43 Composite-containing treatment liquid, 46 Ultrasonic propagation medium, 50, 50A Treatment target electrode, 52 Current collector, 54, 54A Electrode composite.

Claims

1. a heating step of performing a heat treatment on a target electrode including a current collector and an electrode mixture formed on the current collector and containing an aqueous binder, in an oxygen-containing atmosphere at a predetermined heating temperature range of 200°C or higher; an ultrasonic process in which the electrode to be treated after the heat treatment is subjected to ultrasonic treatment in a treatment solution while sweeping ultrasonic frequencies, thereby separating the current collector and the electrode composite; A separation method comprising:

2. 2. The separation method according to claim 1, wherein in the heating step, the heat treatment is performed in the heating temperature range of 250° C. or higher when the oxygen concentration of the oxygen-containing atmosphere is 3% or lower.

3. The separation method according to claim 1 or 2, wherein the heating step is performed in an oxygen-containing atmosphere with an oxygen concentration of 1% or more.

4. The separation method according to claim 1 or 2, wherein the heating step performs the heat treatment in a heating temperature range of 400° C. or less.

5. The separation method according to claim 1 or 2, wherein the heating step comprises performing the heating treatment for 2 minutes or more.

6. 3. The separation method according to claim 1, wherein the electrode to be treated contains a styrene-butadiene copolymer and a carboxymethyl cellulose as the aqueous binder.

7. The separation method according to claim 1 or 2, wherein the electrode to be treated has a layer of the electrode mixture having a thickness of 50 μm or more.

8. The electrode to be treated contains LiFePO as an electrode active material. 4 The separation method according to claim 1 or 2, comprising:

9. a heating unit for performing a heat treatment on a treatment target electrode including a current collector and an electrode mixture formed on the current collector and including a water-based binder; an ultrasonic unit that performs ultrasonic treatment on the electrode to be treated after the heat treatment in a treatment liquid to separate the current collector and the electrode composite; a control unit that controls the heating unit so that the heat treatment is performed in a predetermined heating temperature range of 200° C. or higher under an oxygen-containing atmosphere, and controls the ultrasonic unit so that the ultrasonic treatment is performed while sweeping the frequency of the ultrasonic waves; A separation device comprising:

10. A method for producing an electrode, comprising an electrode production step of producing a new electrode using at least one of the electrode mixture and the current collector obtained by the separation method according to claim 1 or 2.

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