Method for manufacturing electrodes and method for manufacturing batteries

Abstract

To provide a manufacturing method of an electrode, capable of reusing an active material containing layer, and provide a manufacturing method of a battery using the manufacturing method of the electrode.SOLUTION: A manufacturing method of an electrode comprises: Step S1 of separating a first collector from a processed electrode by executing processing by an aqueous solvent to a processed electrode containing the first collector and an active material containing layer formed in the first collector; a step of obtaining a mixture containing the active material containing layer and the aqueous solvent by removing the first collector from the processed electrode after the processing; Step S2 of preparing slurry by using the mixture; and Step S3 of coating a second collector with the slurry.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The embodiments relate to a method for manufacturing electrodes and a method for manufacturing batteries. [Background technology]

[0002] In lithium-ion secondary batteries, lithium-containing metal oxides are used as the positive electrode active material, and carbon is mainly used for the negative electrode. There has been little research and development on the recycling of the negative electrode, and research and development is mainly focused on the recycling of the positive electrode.

[0003] Incidentally, development is underway on secondary batteries equipped with a negative electrode containing niobium titanium oxide or lithium titanium oxide. In order to increase the recycling rate of the manufacturing process of these secondary batteries, it is necessary to realize the recycling of the negative electrode containing niobium titanium oxide or lithium titanium oxide. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 10-92417 [Overview of the project] [Problems that the invention aims to solve]

[0005] The problem to be solved is to provide a method for manufacturing electrodes that allows for the reuse of the active material-containing layer, and a method for manufacturing batteries that utilizes this electrode manufacturing method. [Means for solving the problem]

[0006] According to the embodiment, the process involves treating the electrode to be treated, which includes a first current collector and an active material-containing layer formed on the first current collector, with an aqueous solvent to separate the first current collector from the electrode to be treated, A step of obtaining a mixture containing an active material layer and an aqueous solvent by removing the first current collector from the electrode to be treated after treatment with an aqueous solvent, mixtureJust as A step of preparing a slurry using it, A step of applying the slurry to a second current collector, and A method for manufacturing an electrode is provided, which includes these steps.

[0007] Also, according to an embodiment, a method for manufacturing a battery is provided, which manufactures a battery using the electrode manufactured by the method of the above embodiment.

Brief Description of the Drawings

[0008] [Figure 1] A flowchart showing an example of the flow of the electrode manufacturing method of the first embodiment. [Figure 2] A flowchart showing an example of the flow of the battery manufacturing process. [Figure 3] A flowchart showing an example of the flow of the electrode manufacturing method of the second embodiment. [Figure 4] A flowchart showing an example of the flow of the battery manufacturing process incorporating the electrode manufacturing method of the embodiment. [Figure 5] A partially cut-away perspective view showing an example of a battery manufactured by the method according to the embodiment. [Figure 6] An enlarged cross-sectional view of part A of FIG. 5.

Modes for Carrying Out the Invention

[0009] (First Embodiment) The method for manufacturing an electrode according to the first embodiment will be described below with reference to the drawings. The first embodiment manufactures a new electrode using a processed electrode. An example of the processed electrode is an off-specification electrode that may occur in the manufacturing process of an electrode or a battery, and is usually something that should be discarded. Alternatively, the processed electrode may be one that has been stored unused. Furthermore, the processed electrode may also be one that has been used.

[0010] An example of the electrode to be processed will be described with reference to FIG. 2. FIG. 2 is a flowchart showing an example of the flow of the battery manufacturing process. Battery manufacturing includes, for example, preparing active materials, etc. (S11), dispersion (S12), coating (S13), assembly (S14), electrolyte injection (S15), and processing for commercialization (S16). S11 is a process of preparing, for example, active materials and slurry raw materials such as auxiliary members as necessary. S12 is a process of dispersing active materials, etc. in a solvent to prepare a slurry. S13 is a process of coating the slurry on a current collector. S14 includes a process of housing the electrode (one electrode) produced through S13 and, if necessary, the other electrode and a separator in a container. S15 includes a process of injecting an electrolyte into the container and then sealing the container. S16 includes a process of performing processing necessary for commercialization such as first charging and aging. The waste electrode 1 is an electrode that was produced through the coating S13 but was not provided to the assembly S14 due to reasons such as being out of specification. The un-injected waste battery 2 is a battery in which necessary members such as electrodes are housed in the container, but the electrolyte was not injected due to reasons such as being out of specification. On the other hand, the injected waste battery 3 is a battery in which the electrolyte was injected but did not become a product due to reasons such as being out of specification. Note that after battery manufacturing, S17 of collecting the used battery as the waste battery 4 may be performed. The electrode to be processed can be, for example, the waste electrode 1 or an electrode taken out from the un-injected waste battery 2, the injected waste battery 3, or the waste battery 4. Details of the electrode to be processed will be described below.

[0011] The electrode to be processed can include, for example, a first current collector and an active material-containing layer. The active material-containing layer can be laminated or formed on one or both sides of the first current collector. The active material-containing layer can include an active material, and optionally a conductive agent and a binder.

[0012] The active material is, for example, a titanium-containing oxide. Examples of the titanium-containing oxide include lithium titanate, monoclinic titanium dioxide (TiO2(B)), anatase titanium dioxide, rutile titanium dioxide, niobium pentoxide (Nb2O5), hollandite-type titanium composite oxide, orthorhombic titanium-containing composite oxide, and niobium titanium oxide.

[0013] Examples of lithium titanate oxides include, for example, lithium titanate having a lamellar structure (e.g., Li , Ti3O7, 0 ≦ y ≦ 3), lithium titanate having a spinel structure (e.g., Li 4+x Ti5O 12 , 0 ≦ x ≦ 3), and the like.

[0014] Examples of niobium titanate oxides include monoclinic niobium titanate oxide. Monoclinic niobium titanate oxide is characterized by high stability of the crystal structure, excellent resistance to water, acids, and alkalis, and high density. Examples of monoclinic niobium titanate oxide include compounds represented by Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ . Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. Each subscript in the composition formula is 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, -0.3 ≦ δ ≦ 0.3. Specific examples of monoclinic niobium titanate oxide include Li x Nb2TiO7 (0 ≦ x ≦ 5). The density of Li x Nb2TiO7 (0 ≦ x ≦ 5) is 4.34 g / cm 3 .

[0015] Other examples of monoclinic niobium titanate oxide include compounds represented by Li x Ti 1-y M3 y+z Nb 2-z O 7-δ . Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. Each subscript in the composition formula is 0 ≦ x ≦ 5, 0 ≦ y < 1, 0 ≦ z < 2, -0.3 ≦ δ ≦ 0.3.

[0016] Niobium titanate oxide may contain unavoidable impurities. Examples of unavoidable impurities include K, Na, Si, and P.

[0017] Niobium titanium oxide may contain lithium ions.

[0018] The active material can consist of one or more types. It is desirable that the active material include at least one of lithium titanium oxide or niobium titanium oxide, as this allows the active material to be supported on the current collector by a hydrophilic binder.

[0019] The active material can take the form of particles.

[0020] Conductive agents are added to enhance current collection performance and reduce contact resistance between the active material and the current collector. Examples of conductive agents include carbonaceous materials such as vapor-grown carbon fiber (VGCF), carbon nanotubes, carbon black such as acetylene black, and graphite. One of these may be used as a conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surface of the active material particles may be coated with a carbon coating or an electronically conductive inorganic material coating.

[0021] The binder can fill the gaps between the active materials and bond the active materials to the current collector. The binder is preferably a hydrophilic binder that is water-soluble or water-dispersible, such as an emulsion. Examples of hydrophilic binders include polyacrylic acid compounds, styrene-butadiene rubber, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as a binder, or two or more may be used in combination.

[0022] As an example, the mixing ratios of the active material, conductive agent, and binder in the active material-containing layer may be 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively.

[0023] The first current collector uses a material that is electrochemically stable at the potential where lithium (Li) is inserted into and extracted from the active material. An example of the first current collector is copper, nickel, stainless steel, aluminum, or an aluminum alloy. As an example, the thickness of the first current collector is 5 μm or more and 20 μm or less.

[0024] The first current collector can include a portion on its surface where an active material-containing layer is not formed. This portion functions as a current collection tab.

[0025] Hereinafter, the method for manufacturing the electrode of the embodiment will be described with reference to FIG. 1 by taking the case of using waste electrode 1 as the electrode to be processed as an example.

[0026] FIG. 1 shows an example of the process flow for manufacturing a new electrode using the above waste electrode 1. The method for manufacturing the electrode includes separation S1 with an aqueous solvent, slurry preparation S2, coating S3 of the slurry on the current collector, drying S4, pressing S5, and cutting S6. Waste electrode 1 is an off-spec electrode generated during the electrode manufacturing process or an electrode that has been stored unused. Therefore, the composition of the active material-containing layer of the newly fabricated electrode is the same as that of the active material-containing layer of waste electrode 1.

[0027] <Step S1> Subjecting the electrode to be processed to treatment with an aqueous solvent to separate the first current collector from the electrode to be processed, and removing the first current collector from the processed electrode to obtain a mixture containing the active material-containing layer and the aqueous solvent.

[0028] Waste electrode 1 as the electrode to be processed is treated with an aqueous solvent. Treatments with an aqueous solvent include, for example, immersing the electrode to be processed in the aqueous solvent, shaking the electrode to be processed in the aqueous solvent, subjecting the electrode to be processed in the aqueous solvent to ultrasonic treatment, and the like. Each treatment can be performed alone or a plurality of treatments can be combined.

[0029] Treatment with an aqueous solvent causes the hydrophilic binder in the electrode to be treated to dissolve or leach into the aqueous solvent, allowing the electrode to be separated into a first current collector and an active material-containing layer. The separated active material-containing layer can then be dismantled into lumps or powder. Furthermore, since the electrode is treated with an aqueous solvent without pulverization, the first current collector separated from the electrode maintains an appropriate size, making it easy to remove. In addition, since pulverization before treatment with the aqueous solvent is unnecessary, the process is simplified, resulting in cost and energy benefits. Moreover, niobium titanium oxide is resistant to degradation when in contact with water. Therefore, treatment with an aqueous solvent allows the electrode to be dismantled without damaging the niobium titanium oxide.

[0030] Treatment with an aqueous solvent disperses the active material-containing layer, which has been broken down into a lump or powder form, and the first current collector into the aqueous solvent. By removing the first current collector from the aqueous solvent using a sieve or the like, a mixture containing the active material-containing layer and the aqueous solvent is obtained. Therefore, step S1 may include treating the electrode to be treated with an aqueous solvent and then removing the first current collector from the aqueous solvent. The removed first current collector may be subjected to a separate recycling process.

[0031] Examples of aqueous solvents include water and mixed solvents (mixed liquids) of water and organic substances. Examples of organic substances include at least one selected from the group consisting of alcohol (e.g., ethanol), acetonitrile, and acetone. It is desirable that the aqueous solvent is of the same type as the solvent contained in the slurry prepared in step S2.

[0032] The water content in aqueous solvents should preferably be 50% by volume or more. The upper limit for water content is 100% by volume.

[0033] Treatment with aqueous solvents can be carried out while maintaining the solvent temperature at approximately room temperature. This makes it possible to prevent thermal degradation of the material while accelerating the disassembly of the electrode being treated. Room temperature is, for example, between 5°C and 30°C.

[0034] The device used for aqueous solvent treatment is not particularly limited as long as it includes a container capable of containing an aqueous solvent. For example, a mixing tank equipped with stirring blades can be mentioned.

[0035] <S2 process> A slurry is prepared using the mixture containing the active material-containing layer and the aqueous solvent (hereinafter referred to as the separation composite material) obtained in the S1 process. The slurry is obtained by dispersing the active material-containing layer forming material in a solvent. The active material-containing layer forming material contains an active material and may contain at least one of a binder or a conductive agent as necessary. As an example of the solvent, water can be mentioned.

[0036] Since the separation composite material is a mixture of an aqueous solvent and the active material-containing layer of the waste electrode 1, it can have the same composition as the slurry of the electrode to be produced. By adding a composition with the same composition as the slurry to the separation composite material and slurrying it by at least one of stirring or kneading, a slurry with the target composition can be obtained.

[0037] <S3 process> The slurry is coated on the second current collector.

[0038] The coating is performed on at least a part of the second current collector. For example, the slurry can be coated on one main surface or both main surfaces of the second current collector. The main surface of the second current collector is the surface that defines the thickness of the second current collector.

[0039] The second current collector may be the first current collector separated from the electrode to be processed, or an unused current collector. Also, the second current collector may be a current collector different from the first current collector.

[0040] <S4 process> The coated slurry is dried. Thereby, an active material-containing layer is formed on the second current collector.

[0041] <S5 process> Press the second current collector on which the active material-containing layer is formed. Thereby, an electrode is obtained. In addition, in order to set the obtained electrode to a predetermined shape or size, the electrode may be cut.

[0042] <Step S6> Cut the electrode to set it to a predetermined shape or size. If the electrode after pressing has the intended shape or size, Step S6 can be omitted.

[0043] According to the method for manufacturing an electrode of the first embodiment described above, a treatment with an aqueous solvent is performed on a treated electrode including a first current collector and an active material-containing layer formed on the first current collector to separate the first current collector from the treated electrode, and the first current collector is removed from the treated electrode after the treatment to obtain a mixture including the active material-containing layer and the aqueous solvent, and preparing a slurry using the mixture. According to the method of this embodiment, the active material-containing layer can be separated from the current collector without pulverizing the active material-containing layer included in the treated electrode. Therefore, it is possible to avoid damage to the active material-containing layer due to pulverization. In addition, since the separated active material-containing layer can be directly used to prepare a slurry having a target composition, the active material-containing layer included in the treated electrode can be easily reused. As a result, recycling of the treated electrode can be promoted. In addition, since the active material-containing layer included in the treated electrode is once mixed during the manufacture of the treated electrode, the surface properties (hydrophilicity, hydrophobicity, etc.) are stable. Therefore, since the adhesion during electrode production can be increased, an electrode with good charge / discharge efficiency can be produced. (Second Embodiment) According to the second embodiment, a method for manufacturing an electrode using a battery to be processed can be provided. The method of the second embodiment is the same as the method of the first embodiment except that it includes a step of separating the electrode to be processed from the battery to be processed. The composition of the active material-containing layer of the manufactured electrode is the same as the composition of the active material-containing layer of the electrode to be processed. As shown in FIG. 3, the method of the second embodiment includes S7 of separating the electrode to be processed from the battery to be processed, S1 of separation with an aqueous solvent, S2 of slurry preparation, S3 of coating the slurry on a current collector, S4 of drying, S5 of pressing, and S6 of cutting. Since S1 to S6 are as described in the first embodiment, the details of S7 will be described below. <Step S7> Separate the electrode to be processed from the battery to be processed. This step is performed before the separation S1 with an aqueous solvent.

[0044] The battery to be processed is, for example, an off-specification battery that may occur in the battery manufacturing process and is usually to be discarded. Alternatively, the battery to be processed may be one that has been stored unused. Furthermore, the battery to be processed may be one that has been used. Examples of the battery to be processed include the unliquid-injected waste battery 2, the liquid-injected waste battery 3, and the waste battery 4 described with reference to FIG. 2. In addition, it is desirable to use a battery to be processed whose composition of the active material-containing layer to be reused is known.

[0045] Examples of the structure of the battery to be processed include those including an exterior member, an electrode group housed in the exterior member, and an electrolyte (for example, an electrolytic solution) housed in the exterior member. The electrode group is produced, for example, by disposing a separator between a positive electrode and a negative electrode. The shape of the electrode group is not particularly limited, and for example, those in which the positive electrode, the separator, and the negative electrode are laminated, those in which the positive electrode, the separator, and the negative electrode are wound in a flat or cylindrical shape, those in which the positive electrode, the separator, and the negative electrode are folded into a ninety-nine shape, etc. can be used.

[0046] Step S7 includes at least separating the positive and negative electrodes contained in the battery to be processed. Step S7 varies depending on the state of the battery to be processed. If the battery to be processed is an unfilled waste battery 2, step S7 includes separating the outer casing from the battery to be processed and separating the positive and negative electrodes contained in the battery from which the outer casing has been removed. Details are explained below. <Exterior separation> The battery to be processed is disassembled, and the outer casing is separated from the battery. An outer casing separation device may be used for this purpose.

[0047] The outer casing separation device may be housed in a chamber together with the positive and negative electrode separation device. The chamber should preferably have a low-oxygen atmosphere, such as a nitrogen atmosphere. This prevents the electrolyte from coming into contact with air when the battery is disassembled, thus increasing safety during the process. The outer casing separation device is used to open the battery's outer casing by cutting it and to remove the electrode group from within the casing. For example, a cutter, shredder, or other cutting device can be used as the outer casing separation device. The electrode group is removed from the battery by the outer casing separation. Next, the positive and negative electrodes within the electrode group are separated. <Positive and negative electrode separation> The positive and negative electrodes included in the electrode group are separated. A positive / negative electrode separation device may be used to separate the positive and negative electrodes.

[0048] A positive / negative electrode separation device is used to separate an electrode group into a positive electrode, a separator, and a negative electrode. The electrode group can be obtained as a stack in which the positive and negative electrodes are stacked with separators in between, such as positive electrode, separator, negative electrode, separator, positive electrode, or as a wound body in which the positive electrode, separator, and negative electrode are wound together. For example, in the case of an electrode group using a continuous separator, a device with a mechanism for winding the separator is used as the positive / negative electrode separation device. In this way, the positive electrode and negative electrode can be separated into the front and back sides of the separator. By separating the positive and negative electrodes in this way beforehand, the various components constituting the positive and negative electrodes do not mix, and can be effectively recycled. The separation device may be divided into an outer casing separation device and a positive / negative electrode separation device as described above, but it may also be a device that combines both functions of outer casing separation and positive / negative electrode separation.

[0049] The negative electrode, separated from the battery to be processed by the S7 process described above, is then subjected to the S1 process.

[0050] If the battery to be processed is a liquid-filled waste battery 3 or a waste battery 4, step S7 may include, if necessary, a discharge treatment and a heat treatment as an electrolyte treatment before separating the outer casing. <Heat treatment> The battery to be treated is subjected to heat treatment. The battery may or may not have an outer casing. Heat treatment can remove organic substances such as electrolyte from the battery. Examples of organic substances include organic solvents, carbon materials, and binders. As a result, it is possible to avoid environmental pollution and hazards caused by organic substances, and to separate the current collectors from the positive and negative electrodes. Examples of heat treatment equipment include furnaces and rotary kilns.

[0051] The heat treatment can be carried out, for example, under atmospheric conditions. The heat treatment temperature can be in the range of 300°C to 900°C. Preferably, it is between 400°C and 600°C. This is because performing the treatment below the melting point of aluminum that can be used as a current collector allows for a larger size of aluminum pieces, making them easier to separate in subsequent processes. The treatment time can be in the range of 15 minutes to 6 hours. If the heat treatment temperature is too low or the heat treatment time is too short, organic matter may remain in the battery being treated. On the other hand, if the heat treatment temperature is too high or the heat treatment time is too long, metal materials such as current collectors may melt, making it difficult to separate the metal materials from the active material-containing layer.

[0052] After heat treatment, the battery may be cooled as needed. Cooling methods include, for example, air cooling or water cooling. <Discharge treatment> If necessary, the battery to be treated is subjected to a discharge treatment before heat treatment. The discharge treatment device is not particularly limited as long as it is capable of discharging the battery. Examples of discharge treatment devices include charge / discharge devices and resistors. If there is still usable remaining capacity in the battery, there is a risk of self-discharge or short circuit causing sparks and ignition. Therefore, it is necessary to discharge the battery sufficiently through the positive and negative electrodes so that no usable remaining capacity remains. Specifically, the battery is discharged by connecting it to a charge / discharge device or by attaching an appropriate resistor to the battery. It is desirable to discharge the battery sufficiently until the voltage drops below the voltage at which the battery's usable remaining capacity is lost.

[0053] The negative electrode, separated from the battery to be processed by the S7 process described above, is then subjected to the S1 process.

[0054] According to the method of the second embodiment, electrodes can be manufactured using electrodes removed from a battery to be processed, in accordance with the method of the first embodiment. Therefore, the active material-containing layer contained in the electrode to be processed can be separated from the current collector without crushing the active material-containing layer. This prevents damage to the active material-containing layer due to crushing. Furthermore, since the separated active material-containing layer can be used as is to prepare a slurry of the desired composition and manufacture electrodes, the reuse of the active material-containing layer contained in the electrode to be processed can be promoted. This promotes the recycling of the electrode to be processed. In addition, since the active material-containing layer contained in the electrode to be processed is mixed once during the manufacture of the electrode to be processed, the surface properties (hydrophilicity, hydrophobicity, etc.) are stable. Therefore, adhesion during electrode fabrication can be improved, and electrodes with good charge-discharge efficiency can be manufactured. (Third embodiment) The third embodiment is a method for manufacturing a battery using electrodes manufactured in the first or second embodiment. The third embodiment includes manufacturing electrodes using the method of the first or second embodiment, manufacturing an electrode group including the manufactured electrodes as negative electrodes, housing the electrode group in an outer casing, holding an electrolyte in the electrode group housed in the outer casing, and sealing the outer casing. The electrode group is manufactured, for example, by placing a separator between a positive electrode and a negative electrode. The shape of the electrode group is not particularly limited, and for example, a stack of positive electrodes, separators, and negative electrodes, a flattened or cylindrical winding of positive electrodes, a zigzag bend of positive electrodes, separators, and negative electrodes can be used.

[0055] Figure 4 shows a flowchart illustrating an example of the manufacturing process for the battery according to the third embodiment. First, a waste electrode 1 is prepared as the electrode to be processed. Alternatively, an unfilled waste battery 2, a filled waste battery 3, or a waste battery 4 is prepared as the battery to be processed. The filled waste battery 3 or waste battery 4 is subjected to discharge treatment, electrolyte treatment such as heat treatment as necessary (S21). Next, the filled waste battery 3 or waste battery 4, or the unfilled waste battery 2, after processing is separated from its outer casing, and then the positive electrode and negative electrode are separated (S22). The separated negative electrode is subjected to separation S1 with an aqueous solvent to separate the current collector and the active material-containing layer (S23). The slurry is redispersed using the separated active material-containing layer according to the method described in S2 (S24).

[0056] Next, the redispersed slurry is applied to the second current collector (S13). After that, the applied slurry is dried to form an active material-containing layer on the second current collector. Subsequently, the second current collector with the active material-containing layer is pressed to obtain electrodes.

[0057] Next, in assembly step S14, an electrode group including the fabricated electrode as the negative electrode is manufactured, and then the electrode group is housed in an outer casing.

[0058] Next, in the liquid injection step S15, the electrolyte is held in the electrode group housed in the outer casing, and then the outer casing is sealed.

[0059] Subsequently, in the S16 processing step for product development, initial charging, aging, etc., are performed to obtain the battery.

[0060] The battery manufactured according to the third embodiment is not particularly limited. Examples of batteries include batteries with an aqueous electrolyte and batteries with a non-aqueous electrolyte. Furthermore, the battery may be a single cell, a battery pack, or a battery assembly.

[0061] The battery manufactured by the method of the third embodiment may be used as a battery pack or incorporated into a battery pack. The battery according to the embodiment is suitable for use in applications where excellent cycle performance is required when drawing a large current. Specifically, it can be used as a power source for a digital camera, or as a vehicle battery for, for example, two-wheeled or four-wheeled hybrid electric vehicles, two-wheeled or four-wheeled electric vehicles, electric assist bicycles, or railway vehicles (e.g., electric trains), or as a stationary battery. In particular, it is suitable for use as an on-board battery mounted in a vehicle.

[0062] An example of a battery (secondary battery) will be described with reference to Figures 5 and 6. Figure 5 is a partially cutaway perspective view showing a non-aqueous electrolyte secondary battery, which is an example of a battery. Figure 6 is an enlarged cross-sectional view of part A of the non-aqueous electrolyte secondary battery shown in Figure 5. As shown in Figure 5, the non-aqueous electrolyte battery 20 includes a bottomed rectangular cylindrical metal container 21, a group of flattened electrodes 22, a metal sealing plate 23, a negative electrode terminal 24, and a positive electrode terminal 25. The group of flattened electrodes 22 is housed inside the metal container 21.

[0063] The flattened electrode group 22 includes a negative electrode 26, a positive electrode 27, and a separator 28. The electrode group 22 has a structure in which the negative electrode 26 and the positive electrode 27 are wound in a spiral shape with the separator 28 interposed between them to form a flattened shape. Although a wound electrode group is described here, the electrode group may also be a stacked electrode group in which multiple negative electrodes 26, separators 28, and positive electrodes 27 are stacked. As shown in Figure 6, the negative electrode 26 comprises a negative electrode current collector 26a and a negative electrode active material containing layer 26b supported on the negative electrode current collector 26a. As shown in Figure 6, the positive electrode 27 comprises a positive electrode current collector 27a and a positive electrode active material containing layer 27b supported on the positive electrode current collector 27a. An electrolyte (not shown) is held in the electrode group 22. The opening of the metal container 21 is sealed with a metal sealing plate 23. The metal container 21 and the sealing plate 23 constitute the outer casing.

[0064] As shown in Figure 5, a negative electrode terminal 24 is provided on the metal sealing plate 23. A negative electrode current collector tab 29 is electrically connected to the negative electrode terminal 24. The negative electrode current collector tab 29 is electrically connected to the negative electrode current collector 26a of the negative electrode 26. The positive electrode terminal 25 is fixed to the metal sealing plate 23 via an insulating member 30. A positive electrode current collector tab 31 is electrically connected to the positive electrode terminal 25. The positive electrode current collector tab 31 is electrically connected to the positive electrode current collector 27a of the positive electrode 27.

[0065] An example of the negative electrode 26 is an electrode containing a titanium-containing oxide as described in the first embodiment. The positive electrode active material contained in the positive electrode 27 can be, for example, a compound that can insert and remove Li or Li ions. The positive electrode current collector 27a can be, for example, a metal foil.

[0066] For example, the separator 28 can be made of a porous film, a nonwoven fabric made of synthetic resin, a solid electrolyte layer, or the like.

[0067] For electrolytes, for example, aqueous electrolytes and non-aqueous electrolytes can be used. Non-aqueous electrolytes include, for example, non-aqueous electrolytes prepared by dissolving an electrolyte salt, such as a lithium salt, in an organic solvent. Aqueous electrolytes include, for example, aqueous electrolytes prepared by dissolving an electrolyte salt, such as a lithium salt, in an aqueous solvent. Examples of electrolyte salts include lithium salts such as lithium perchlorate (LiClO4), lithium hexafluoride phosphate (LiPF6), lithium tetraborate (LiBF4), lithium arsenide hexafluoride (LiAsF6), lithium trifluoromethanesulfonate (LiCF3SO3), and lithium bistrifluoromethylsulfonylimide (LiN(CF3SO2)2).

[0068] The exterior components illustrated in Figures 5 and 6 are made of metal, but are not limited to metal. For example, laminate film may be used as the exterior component. Furthermore, the shape of the exterior component is not particularly limited. The shape of the exterior component may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior component can be appropriately selected according to the battery dimensions and the battery's application.

[0069] According to the third embodiment, since electrodes manufactured in the first or second embodiment are used, it is possible to manufacture batteries with a high recycling rate.

[0070] The following describes a specific example of the electrode manufacturing method of the embodiment. The battery to be processed is an unfilled waste battery 2 using a metal can as the outer casing. The unfilled waste battery 2 is placed in an outer casing separation device installed in a chamber set to a nitrogen atmosphere, and the outer casing (can) is cut to remove the electrode group. Furthermore, this electrode group is passed through a positive and negative electrode separation device provided in the chamber to separate it into a positive electrode, a separator, and a negative electrode.

[0071] The separated negative electrode contains a negative electrode active material-containing layer comprising 80% by mass of niobium titanium oxide (represented by Nb2TiO7) as a titanium-containing oxide, 10% by mass of acetylene black as a conductive agent, and 10% by mass of CMC as a binder, and a first current collector made of aluminum foil. The negative electrode is immersed in water. This separates the negative electrode into the first current collector and the active material-containing layer, and also allows the separated active material-containing layer to be broken down into lumps or powder. Subsequently, by removing the first current collector in the water with a coarse mesh, a slurry is obtained in which the lumps or powder of the active material-containing layer are dispersed in water. A composition with the same composition as the obtained slurry (a slurry in which 80% by mass of niobium titanium oxide, 10% by mass of acetylene black, and 10% by mass of CMC are dispersed in an aqueous solvent) is added, and a slurry of the desired composition is obtained by stirring or kneading. The obtained slurry is applied onto a second current collector made of aluminum foil, and then dried and pressed to produce an electrode.

[0072] The electrode manufacturing method of at least one embodiment or example described above includes: treating the electrode to be processed, which includes a first current collector and an active material-containing layer formed on the first current collector, with an aqueous solvent to separate the first current collector from the electrode to be processed; removing the first current collector from the electrode after processing to obtain a mixture containing the active material-containing layer and the aqueous solvent; and preparing a slurry using the mixture. This makes it possible to reuse the active material-containing layer as is while avoiding damage to the active material-containing layer contained in the electrode to be processed by crushing, thereby promoting the recycling of the electrode to be processed.

[0073] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents.

[0074] The invention according to the embodiment is described below. <1> A step of separating the first current collector from the electrode to be treated by treating the electrode, which includes a first current collector and an active material-containing layer formed on the first current collector, with an aqueous solvent. A step of obtaining a mixture containing the active material layer and the aqueous solvent by removing the first current collector from the electrode to be treated after the above treatment, A step of preparing a slurry using the aforementioned mixture, The process involves applying the slurry to the second current collector. A method for manufacturing electrodes, including <2> The active material contained in the active material-containing layer comprises at least one of niobium titanium oxide or lithium titanium oxide. <1> A method for manufacturing electrodes as described above. <3> The aforementioned aqueous solvent is either water or a mixed solvent of water and an organic substance. <1> or <2> A method for manufacturing electrodes as described above. <4> The treatment with the aqueous solvent includes immersing the electrode to be treated in the aqueous solvent. <1> from <3> A method for manufacturing an electrode as described in any of the following. <5> The active material-containing layer further comprises a hydrophilic binder and a conductive agent. <1> from <4> A method for manufacturing an electrode as described in any of the following. <6> The aforementioned niobium titanium oxide has the general formula Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Niobium titanium oxide represented by the general formula Li x Ti 1-y M3 y+z Nb 2-z O 7-δ It includes at least one selected from the group consisting of niobium titanium oxides represented by the following: M1 is at least one selected from the group consisting of Zr, Si, and Sn; M2 is at least one selected from the group consisting of V, Ta, and Bi; M3 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo; x satisfies 0 ≤ x ≤ 5; y satisfies 0 ≤ y < 1; z satisfies 0 ≤ z < 2; and δ satisfies -0.3 ≤ δ ≤ 0.3. <2> from <5> A method for manufacturing an electrode as described in any of the following. <7> The slurry is prepared by adding a composition having the same composition as the slurry to the mixture and forming a slurry. <1> from <6> A method for manufacturing an electrode as described in any of the following. <8> The process further includes separating the electrode to be treated from the battery to be treated before the treatment with the aqueous solvent is performed. <1> from <7> A method for manufacturing an electrode as described in any of the following. <9> <1> from <8> A method for manufacturing a battery, comprising manufacturing a battery using electrodes manufactured by one of the methods described above. [Explanation of Symbols]

[0075] 1...Waste electrode, 2...Unfilled waste battery, 3...Waste battery with electrolyte, 4...Waste battery, 20...Non-aqueous electrolyte battery, 21...Metal container, 22...Electrode group, 23...Metal sealing plate, 24...Negative electrode terminal, 25...Positive electrode terminal, 26...Negative electrode, 26a...Negative electrode current collector, 26b...Negative electrode active material containing layer, 27...Positive electrode, 27a...Positive electrode current collector, 27b...Positive electrode active material containing layer, 28...Separator, 29...Negative electrode current collector tab, 30...Insulating material, 31...Positive electrode current collector tab, S1... S2...Separation with aqueous solvent, S3...Slurry preparation, S4...Slurry coating onto current collector, S5...Drying, S6...Pressing, S7...Separation of electrodes to be processed from the battery to be processed, S11...Preparation of active material, etc., S12...Dispersion, S13...Coating, S14...Assembly, S15...Injection of liquid, S16...Product, S17...Recovery, S21...Electrolyte treatment, etc., S22...Positive and negative electrode separation, S23...Separation of current collector and active material-containing layer, S24...Redispersion of slurry.

Claims

1. A step of separating the first current collector from the electrode to be treated by treating the electrode, which includes a first current collector and an active material-containing layer formed on the first current collector, with an aqueous solvent. A step of obtaining a mixture containing the active material layer and the aqueous solvent by removing the first current collector from the electrode to be treated after the above-mentioned processing, A step of preparing a slurry using the aforementioned mixture as is, The process of applying the slurry to the second current collector A method for manufacturing electrodes, including

2. The method for manufacturing an electrode according to claim 1, wherein the active material contained in the active material-containing layer includes at least one of niobium titanium oxide or lithium titanium oxide.

3. The method for manufacturing an electrode according to claim 2, wherein the aqueous solvent is water or a mixed solvent of water and an organic substance.

4. The method for manufacturing an electrode according to claim 2, wherein the treatment with the aqueous solvent includes immersing the electrode to be treated in the aqueous solvent.

5. The method for manufacturing an electrode according to claim 2, wherein the active material-containing layer further comprises a hydrophilic binder and a conductive agent.

6. The method for producing an electrode according to claim 5, wherein the hydrophilic binder comprises at least one selected from the group consisting of polyacrylic acid compounds, styrene-butadiene rubber, carboxymethylcellulose, and salts of carboxymethylcellulose.

7. The niobium titanium oxide is represented by the general formula Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ and includes at least one selected from the group consisting of niobium titanium oxides represented by the general formula Li x Ti 1-y M3 y+z Nb 2-z O 7-δ ​ The method for manufacturing an electrode according to claim 2, wherein M1 is at least one selected from the group consisting of Zr, Si, and Sn, M2 is at least one selected from the group consisting of V, Ta, and Bi, M3 is at least one selected from the group consisting of Mg, Fe, Ni, Co, W, Ta, and Mo, x satisfies 0 ≤ x ≤ 5, y satisfies 0 ≤ y < 1, z satisfies 0 ≤ z < 2, and δ satisfies -0.3 ≤ δ ≤ 0.

3.

8. The method for producing an electrode according to claim 1, wherein the slurry is prepared by adding a composition having the same composition as the slurry to the mixture and forming a slurry.

9. The method for manufacturing an electrode according to claim 1, further comprising the step of separating the electrode to be treated from the battery to be treated before the treatment with the aqueous solvent.

10. A method for manufacturing a battery, comprising manufacturing a battery using electrodes manufactured by the method described in any one of claims 1 to 9.

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