Method for recycling active material, method for manufacturing active material and electrode

Abstract

This invention provides a method for recycling active material in electrodes, an active material obtained by this method, and a method for manufacturing electrodes using the active material. [Solution] According to the embodiment, a method for recycling active material is provided, comprising: step S2 of heat-treating an electrode, which includes a first current collector and an active material-containing layer supported on the first current collector and containing an active material including a first lithium titanium-containing oxide, a fluorine-containing binder, and a conductive agent, at a first temperature below the melting point of the first current collector; step S3 of separating the first current collector from the heat-treated product to obtain a mixture containing an active material, a titanium-containing material, a conductive agent, and a fluorine compound with a fluorine concentration of 5,000 ppm by mass or more and 22,000 ppm by mass or less; and step S4 of heat-treating the mixture at a second temperature higher than the first temperature to synthesize a second lithium titanium-containing oxide.

Description

[Technical Field]

[0001] The embodiments relate to a method for recycling active material, and a method for manufacturing active material and electrodes. [Background technology]

[0002] Secondary batteries equipped with negative electrodes containing lithium titanium oxides such as lithium titanate are being manufactured. Waste materials are unavoidable during the manufacturing process. Therefore, recycling of these waste materials is required. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2023-534797 [Overview of the project] [Problems that the invention aims to solve]

[0004] The problem to be solved is to provide a method for recycling active material in electrodes that enables the recycling of the active material, an active material obtained by this method, and a method for manufacturing electrodes using the active material. [Means for solving the problem]

[0005] According to the embodiment, the process involves heat-treating a first current collector and an electrode supported on the first current collector, which includes an active material containing a first lithium titanium oxide, a fluorine (F)-containing binder, and a conductive agent, at a first temperature below the melting point of the first current collector. A step of separating the first current collector from the heat-treated material to obtain a mixture containing an active material, a titanium-containing material, a conductive agent, and a fluorine compound with a fluorine (F) concentration of 5000 ppm by mass or more and 22000 ppm by mass or less, The process involves synthesizing a lithium titanium-containing oxide by heat-treating the mixture at a second temperature higher than the first temperature. A method for recycling active materials, including the above, is provided.

[0006] Further, according to an embodiment, there are provided an active material recycled by the method of the above embodiment, an electrode containing the active material, and a method for manufacturing an electrode for manufacturing an electrode using the active material.

Brief Description of the Drawings

[0007] [Figure 1] A flowchart showing an example of the flow of the method of the first embodiment. [Figure 2] A plan view showing an example of the first electrode (target electrode). [Figure 3] A cross-sectional view taken along line III-III of the electrode shown in FIG. 2. [Figure 4] A cross-sectional view taken along line IV-IV of the electrode shown in FIG. 2. [Figure 5] A flowchart showing an example of the flow of the electrode manufacturing method in the method of the second embodiment. [Figure 6] A flowchart showing an example of the flow of the method of the third embodiment. [Figure 7] A partially cut-away perspective view showing an example of a battery manufactured by the method according to the embodiment. [Figure 8] An enlarged cross-sectional view of part A of FIG. 7. [Figure 9] A diagram showing the powder X-ray diffraction pattern of the sample after heat treatment in the example.

Modes for Carrying Out the Invention

[0008] (First Embodiment) According to the first embodiment, a method for recycling active material is provided. The method of the first embodiment is a method for recycling active material contained in an electrode. The electrode includes a first current collector and an active material-containing layer supported (or formed) on the first current collector. The active material-containing layer includes an active material containing a first lithium titanium-containing oxide, a fluorine (F)-containing binder, and a conductive agent. The method of the first embodiment includes heat-treating the electrode at a first temperature below the melting point of the first current collector, separating the first current collector from the heat-treated product to obtain a mixture (referred to as the first mixture) containing the active material, titanium-containing material, conductive agent, and a fluorine compound with a fluorine (F) concentration of 5000 ppm by mass or more and 22000 ppm by mass or less, and synthesizing a second lithium titanium-containing oxide by heat-treating the first mixture at a second temperature higher than the first temperature.

[0009] The electrode, which contains the active material to be recycled, is referred to as the first electrode or target electrode. The electrode containing the active material obtained by the method of the first embodiment is referred to as the second electrode. The first electrode (target electrode) does not contain an electrolyte. The first electrode is a discarded electrode that may be generated, for example, in the manufacturing process of an electrode or battery. The first electrode is also called waste material or a waste electrode. An example of a first electrode is an off-spec electrode that may be generated in the manufacturing process of an electrode or battery. Another example of a first electrode is an electrode that has been stored unused. Another example of a first electrode is a fragment of an electrode, such as a scrap generated by cutting. When the first electrode is a waste electrode generated in the manufacturing process, the composition of the active material-containing layer is usually known. Also, because it is unused, for example, has not been charged or discharged, the degradation of the active material has hardly progressed. Therefore, by recycling the active material separated from the first electrode, the active material containing lithium titanium oxide can be easily regenerated.

[0010] A method for recycling active material according to the first embodiment will be described below with reference to the drawings. Figure 1 is a flowchart showing the method of the first embodiment. An example of the method for recycling active material according to the first embodiment includes, for example, steps S1 to S4 shown in Figure 1. Each step will be described below. <Process S1> Dry the first electrode (target electrode).

[0011] An example of the first electrode (target electrode) is shown in Figures 2 to 4. In Figures 2 to 4, the direction of the long side of the first electrode 1 is the y-axis direction. The direction of the short side of the first electrode 1 is the x-axis direction. The direction of the thickness of the first electrode 1 is the z-axis direction. The first electrode 1 includes a first current collector 2 and an active material-containing layer 3 containing an active material, a fluorine-containing binder, and a conductive agent. The first current collector 2 is, for example, a conductive sheet. The sheet has a quadrilateral shape on the surface parallel to the xy-plane. In Figure 2, it is rectangular. In Figures 2 to 4, the active material-containing layer 3 is supported on both xy-planes of the first current collector 2, but is not limited to this. For example, the active material-containing layer 3 may be supported on only one of the xy-planes of the first current collector 2. In Figures 2 to 4, the active material-containing layer 3 is supported on both sides of the first current collector 2, excluding both ends in the short-side direction, but is not limited to this. The active material-containing layer 3 may be supported on all sides of the first current collector 2 except for one end in the short-side direction, or it may be supported on all sides of the first current collector 2. The portion of the first current collector 2 on which the active material-containing layer 3 is not supported may function as a current collector tab.

[0012] The first electrode may contain moisture. By drying the first electrode, the moisture can be removed from it. As a result, the generation of hydrogen fluoride (HF) in processes after S1 can be suppressed. Hydrogen fluoride can be a factor in the degradation of the active material.

[0013] Drying is performed, for example, by heating the first electrode. Heating is performed, for example, by a furnace. The form of the heating furnace is not particularly limited, but examples include batch furnaces and continuous furnaces. The heating temperature is preferably between 80°C and 150°C. By keeping the temperature within this range, it is possible to remove most of the moisture from the first electrode while suppressing the decomposition of the fluorine-containing binder. When heating is performed, for example, by a furnace, it is preferable to set the temperature inside the furnace within the above range.

[0014] Heating can be carried out at a constant temperature, or by gradually or continuously increasing the temperature. A gradual rate of heating is preferable.

[0015] The heating atmosphere can be, for example, air or an inert atmosphere.

[0016] Furthermore, since the first electrode is absorbent, it is desirable to perform step S1 before step S2. <Process S2> A heat-treated product is obtained by heat-treating the first electrode (target electrode) at a first temperature below the melting point of the first current collector.

[0017] When the first electrode is heat-treated at a temperature below the melting point of the first current collector, a portion of the fluorine-containing binder decomposes (e.g., through thermal decomposition). As a result, the bonding force between the first current collector and the active material-containing layer can be weakened. Although the first current collector is heat-treated, it does not melt and can maintain almost its original properties (e.g., shape) before heat treatment. As a result, it becomes easy to separate the heat-treated first current collector from the entire heat-treated material. One example of heat treatment is firing. Firing can be performed using a furnace or the like as a heat treatment method. Therefore, firing allows for heat treatment using a simple method.

[0018] The first current collector is preferably conductive. The composition of the first current collector can be varied depending on the type of active material. The first current collector is formed of a conductive material that is electrochemically stable at the potential in which lithium (Li) is inserted and removed. An example of the first current collector is one which includes at least one selected from the group consisting of copper, nickel, stainless steel, aluminum, and aluminum alloys. The first current collector may include at least one of aluminum or an aluminum alloy. The melting point of the first current collector which includes at least one of aluminum or an aluminum alloy may be around 660°C. A temperature below the melting point of the first current collector can be set to, for example, 660°C or less, preferably less than 660°C.

[0019] The thickness of the first current collector may vary depending on the type and size of the battery, but as an example, it is between 5 μm and 20 μm.

[0020] The conductive agent is not particularly limited, but may include carbon materials. When using a conductive agent containing carbon materials, the decomposition (thermal decomposition) of the conductive agent can be suppressed by keeping the heat treatment temperature below 660°C. By suppressing the loss of the conductive agent, the conductive paths between active materials in the regenerated electrode can be maintained. Examples of carbon materials include carbon fibers (e.g., vapor-grown carbon fiber (VGCF)), carbon nanotubes, carbon black such as acetylene black, and graphite. One of these may be used as the conductive agent, or two or more may be used in combination. The conductive agent may exist independently of the active material or be supported on the surface of the active material particles. Conductive agents containing carbon nanotubes tend to entangle with the surface of active material particles. Conductive agents containing carbon black such as acetylene black tend to adhere to the surface of active material particles. Conductive agents containing at least one of carbon nanotubes or carbon black can increase the contact area with the active material particles. Therefore, it is easy to maintain good conductive paths between active material particles even in the regenerated electrode.

[0021] The heat treatment temperature can be 20°C or more lower than the melting point of the first current collector. This further suppresses the melting of the first current collector. It also suppresses the thermal loss of the conductive agent. The heat treatment temperature can be, for example, 640°C or lower, more preferably less than 640°C.

[0022] When the first current collector contains at least one of aluminum or an aluminum alloy, the preferred heat treatment temperature is 300°C to 500°C. To remove and recover the active material-containing layer from the first current collector, it is desirable to set the heat treatment temperature to a level that thermally decomposes the binder, rendering it ineffective. On the other hand, Al is an easily oxidized element, and when heated in contact with iron oxide, it exhibits a very violent oxidation reaction called the thermite reaction. By setting the heat treatment temperature to 300°C to 500°C, the thermite reaction can be avoided while promoting the thermal decomposition of the binder.

[0023] Fluorine-containing binders may consist solely of fluorine (F)-containing binders, or they may contain both F-containing and F-free binders. The F-containing binder preferably contains a fluorine (F)-containing polymer. Examples of F-containing polymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorinated rubber. PVdF is preferred because it allows for good solubility of the binder in the solvent and ease of electrode molding while ensuring battery performance. PVdF may be modified or unmodified. PVdF can react with the Li of lithium titanium oxide to produce LiF by heat treatment at a first temperature. As a result of this reaction, the lithium titanium oxide is decomposed, and titanium oxide (e.g., TiO2) is produced from the Ti of the lithium titanium oxide. Titanium oxide is a decomposition product of lithium titanium oxide. LiF and TiO2 react by firing at temperatures above 800°C to produce lithium titanate. Examples of binders that do not contain fluorine include styrene-butadiene rubber, polyacrylic acid compounds, imide compounds, carboxymethyl cellulose (CMC), and salts of CMC. One or more types of binders may be used.

[0024] It is desirable that the content of fluorine-containing binder in the active material-containing layer be between 0.5% by mass and 5% by mass.

[0025] The decomposition of the binder during heat treatment at the first temperature is, for example, thermal decomposition. The decomposition (thermal decomposition) of the binder only needs to occur in at least a portion of the binder contained in the first electrode (target electrode). This is because the decomposition of a portion of the binder reduces the bonding strength between the active material or conductive agent and the first current collector. This makes it easier to separate the active material and conductive agent from the first current collector. To promote the decomposition reaction of the binder, the lower limit of the heat treatment temperature can be set to be higher than the decomposition temperature of the binder. Here, if there are multiple types of binders, it is desirable to set the lower limit of the heat treatment temperature to the maximum decomposition temperature (or the higher of the two types). Details of the binder decomposition temperature will be described later.

[0026] The atmosphere used for heat treatment is not particularly limited. The oxygen concentration, moisture content, and other parameters of the atmosphere can be set to any range. One example of such an atmosphere is air.

[0027] The time required for the heat treatment is adjusted according to the heat treatment temperature, the composition of the first electrode, and other factors.

[0028] The active material can be either the positive electrode active material or the negative electrode active material. Furthermore, the electrodes may contain one or more types of active materials. The active material may take the form of particles.

[0029] The active material includes a lithium titanium-1 oxide. An example of a lithium titanium-1 oxide is lithium titanate (e.g., Li) having a ramsdelite structure. 2+y Li3O7 (0≦y≦3), lithium titanate having a spinel structure (e.g., Li 4+x Ti5O 12The first lithium titanium-containing oxide may contain metal elements other than Li and Ti. Examples of metal elements include at least one metal element (let's call it metal element α) selected from the group consisting of Mn, Co, Ni, V, Zr, Nb, Mo, and W. Metal element α may be substituted for a portion of titanium. There can be one or more types of the first lithium titanium-containing oxide.

[0030] The active material is not particularly limited in terms of its content as long as it contains lithium titanium-1 oxide, but it is desirable that the content of lithium titanium-1 oxide in the active material be between 80% by mass and 100% by mass.

[0031] The active material may contain active materials other than lithium titanium-1 oxide. Examples of other active materials include silicon, carbonaceous materials, and oxides. Each material can intercept and deintercept lithium ions.

[0032] Examples of carbonaceous materials include graphite, carbon fibers, coke, and non-graphitizable carbon.

[0033] Examples of oxides include titanium-containing oxides and niobium-containing oxides. Examples of titanium-containing oxides include monoclinic titanium dioxide (TiO2(B)), anatase-type titanium dioxide, rutile-type titanium dioxide, hollandite-type titanium composite oxides, and orthorhombic titanium-containing composite oxides. Examples of niobium-containing oxides include niobium oxide, niobium-titanium-containing oxides, niobium-tungsten-containing oxides, and niobium-titanium-molybdenum-containing oxides. <Process S3> By separating the first current collector from the heat-treated material, a first mixture is obtained containing an active material, a titanium-containing material, a conductive agent, and a fluorine compound with a fluorine concentration of 5,000 ppm by mass or more and 22,000 ppm by mass or less.

[0034] In the heat-treated product obtained by step S2, at least a portion of the fluorine-containing binder is eliminated by decomposition. The fluorine-containing binder includes, for example, a fluorine (F)-containing polymer. The heat treatment at the first temperature decomposes the F-containing polymer, but F does not volatilize and reacts with Li in the active material to produce fluorine compounds such as LiF. In addition, this reaction decomposes the first lithium titanium-containing oxide in the active material to produce a titanium-containing material, such as titanium oxide (titanium dioxide). Specific examples of titanium dioxide include rutile-type TiO2 and anatase-type TiO2. The fluorine (F) concentration in the first mixture is preferably between 5000 ppm by mass and 22000 ppm by mass. Within this range, much of the F in the binder reacts with the active material and remains in the first mixture as a fluorine compound. A more preferable range is between 9000 ppm by mass and 12000 ppm by mass.

[0035] The first current collector is heat-treated, but melting is suppressed, and it is not a molten material. The conductive agent and active material are heat-treated. Also, at least a portion of the active material is in contact with the conductive agent. In the heat-treated material, the bonding force of the conductive agent and active material to the first current collector is reduced, so the first current collector can be easily separated from the conductive agent and active material.

[0036] Separation can be performed by peeling, grasping, suctioning, centrifugal separation, or sieving the heat-treated material of the first current collector from the heat-treated material. The heat-treated material may be crushed or subjected to ultrasonic vibration before separation, but this is not required. The heat-treated material of the first current collector can be easily separated from the heat-treated material without crushing or applying ultrasonic vibration. This avoids damage such as shock to the active material and conductive agent. Furthermore, since the heat-treated material of the first current collector is not subdivided by crushing and can be kept almost to its original size, the heat-treated material of the first current collector can be easily removed. <Process S4> The first mixture is subjected to heat treatment at a second temperature higher than the first temperature.

[0037] By subjecting the first mixture to heat treatment at a second temperature, a fluorine compound such as LiF can be reacted with a titanium-containing material such as titanium oxide. As a result, a lithium titanium-containing oxide can be synthesized from the Li of the fluorine compound and the titanium-containing material. Note that the F contained in the fluorine compound volatilizes and disappears. One example of heat treatment is calcination. For calcination, a furnace or the like can be used as the heat treatment method. Therefore, calcination allows for heat treatment in a simple manner. An example of a lithium titanium-containing oxide can be the same as that of a lithium titanium-containing oxide. The lithium titanium-containing oxide may have the same composition as the lithium titanium-containing oxide, or a different composition. It is desirable that the lithium titanium-containing oxide has the same composition as the lithium titanium-containing oxide.

[0038] If the fluorine concentration of the first mixture is maintained at 5000 ppm by mass or more and 22000 ppm by mass or less, the first mixture may be subjected to crushing, washing, or the like before performing step S4. To shorten the time required for the recycling process, step S4 may be performed immediately after step S3.

[0039] The second temperature is preferably between 700°C and 1000°C. A temperature above 700°C promotes the reaction between the fluorine compound and the titanium-containing material, thereby accelerating the synthesis of lithium titanium dioxide. The melting point of LiF is 848°C. Therefore, while a higher second temperature promotes the synthesis of lithium titanium dioxide, it also leads to grain growth of the lithium titanium dioxide. To ensure sufficient active material capacity while promoting the synthesis of lithium titanium dioxide, the second temperature is preferably between 700°C and 1000°C. A more preferable range for the second temperature is between 800°C and 1000°C.

[0040] The atmosphere used for heat treatment is not particularly limited. The oxygen concentration, moisture content, and other parameters of the atmosphere can be set to any range. One example of such an atmosphere is air.

[0041] The time required for the heat treatment is adjusted according to the heat treatment temperature, the composition of the first mixture, and other factors.

[0042] The mixture obtained by heat treatment at the second temperature (referred to as the second mixture) may contain, in addition to the lithium titanium-containing oxides (first and second lithium titanium-containing oxides), titanium-containing materials and conductive agents. Furthermore, the second mixture may contain a binder to the extent that it does not hinder the separation in step S3.

[0043] The fluorine concentration in the second mixture is preferably lower than that in the first mixture. This is to reduce the amount of fluorine (F) that is mixed into the electrode using the lithium titanium oxide synthesized with S4. There is a risk that hydrogen fluoride may be generated in the electrode from the mixed-in F. The fluorine concentration in the second mixture is preferably half or less of the fluorine concentration in the first mixture.

[0044] To set the particle size distribution of the second mixture within the desired range, the second mixture may be subjected to grinding.

[0045] According to the method of the first embodiment described above, the fluorine-containing binder can be reduced by decomposition through heat treatment at a first temperature below the melting point of the first current collector, so that the first current collector can be easily separated from the heat-treated material without pulverizing the resulting heat-treated material. During heat treatment at the first temperature, the fluorine-containing binder decomposes and F is generated, which reacts with Li in the first lithium titanium-containing oxide in the active material to produce a fluorine compound. This reaction decomposes the first lithium titanium-containing oxide. By subjecting the mixture containing the decomposed active material and the fluorine compound to heat treatment at a second temperature, a second lithium titanium-containing oxide can be synthesized from the decomposed active material. Therefore, the active material extracted from the electrode can be recycled without adding new raw materials such as Li. Furthermore, by using an electrode discarded in the manufacturing process as the first electrode, the recycling rate in the manufacturing process can be increased.

[0046] The following describes methods for measuring the decomposition temperature of the binder, measuring the fluorine concentration in the mixture, measuring the composition of the mixture, and confirming the positive and negative electrode active materials.

[0047] First, if the electrode to be measured (positive or negative electrode) is incorporated into a battery, remove the electrode from the battery as follows: First, disassemble the battery containing the electrode in a glove box filled with argon. Remove the electrode to be measured from the disassembled battery. Wash this electrode with a suitable solvent. For example, methyl ethyl carbonate can be used as the solvent for washing. Vacuum dry the washed electrode. Thus, obtain the electrode for measurement. <Method for measuring the decomposition temperature of binders> The decomposition temperature of the binder is measured, for example, by evolved gas analysis - mass spectrometry (EGA-MS). Evolved gas analysis measures the temperature profile of the gas generated from the sample. Detection is performed by mass spectrometry (MS). Approximately 1 mg of the active material-containing layer (electrode composite) of the measuring electrode, extracted using the above method, is weighed into a sample cup for EGA-MS analysis. The measurement is performed, for example, at a heating rate of 10°C / min. Details of the measurement conditions are described below.

[0048] For the pyrolyzer, the heating temperature is maintained at 40°C for 4 minutes, and then increased to 600°C at a heating rate of 10°C / min. The sample volume is approximately 1 mg.

[0049] For GC (gas chromatography), the inlet temperature is 300°C, and the column is Ultra Alloy DTM 2.5m 0.15mm id. The temperature is maintained at 300°C. The split ratio is 1:50. The He flow rate is 1.0 mL / min. For MS, the mass range is 10 to 600 m / z. The ionization method is EI (EI stands for Electron Impact or Electron Ionization). <Qualitative analysis of binding agents> The organic components contained in the first electrode (target electrode) can be identified by pyrolysis-gas chromatography-mass spectrometry (Pyro-GC-MS). Pyrolysis-gas chromatography-mass spectrometry is an instantaneous pyrolysis method in which the sample is heated and decomposed at a set pyrolysis temperature, and the resulting material is analyzed by gas chromatography-mass spectrometry (GC-MS). The analytical conditions are described below.

[0050] Weigh approximately 1 mg of the active material-containing layer (electrode composite) of the measuring electrode into a sample cup for EGA-MS analysis. <Pyrolyzer> The heating temperature should be 400-700°C.

[0051] The sample volume should be approximately 1 mg. <gc> The pouring port temperature will be set to 300°C.

[0052] A UA-5 (HT / MS) 30m 0.25mm id column is used. The temperature is maintained at 40°C for 2 minutes, then increased to 320°C at a heating rate of 10°C / min.

[0053] The split ratio is set to 1:50.

[0054] The helium flow rate is set to 1.0 mL / min. Set the mass range to 10 - 600 m / z.

[0055] The ionization method is EI (EI stands for Electron Impact or Electron Ionization). <Method for Measuring Fluorine (F) Concentration in a Mixture> The details of the combustion - ion chromatography method are described below. Place the sample in a combustion decomposition unit and combust it in a combustion gas stream containing oxygen, and collect the generated gas in an absorption liquid. Separate and quantify the fluoride ions collected in the absorption liquid by ion chromatography. <Positive Electrode Active Material> The crystal structure and elemental composition of the positive electrode active material can be confirmed by powder X - ray diffraction (XRD: X - ray diffraction) measurement and inductively coupled plasma (ICP: Inductively Coupled Plasma) optical emission spectrometry. <Negative Electrode Active Material> The crystal structure and elemental composition of the negative electrode active material can be confirmed by powder X - ray diffraction (XRD: X - ray diffraction) measurement and inductively coupled plasma (ICP: Inductively Coupled Plasma) optical emission spectrometry. <XRD Measurement Method> The powder X - ray diffraction measurement of the positive electrode active material, negative electrode active material, and their mixture can be performed as follows, for example. First, pulverize the active material or mixture as necessary to prepare a sample with an average particle size of less than about 5 μm. The average particle size can be determined by the laser diffraction method. Fill the obtained sample into a holder portion with a depth of 0.2 mm formed on a glass sample plate. Then, press another glass plate from the outside to flatten the surface of the filled sample. Take care to fill an appropriate amount of sample so that there are no cracks, voids, unevenness, etc. in the filled sample. Also, pay attention to pressing the glass plate with sufficient pressure. Then, place the glass plate filled with the sample in a powder X - ray diffractometer and obtain an XRD pattern using Cu - Kα rays.

[0056] The average particle size is measured using the laser diffraction method, for example, by the following method. The average particle size is measured using a laser diffraction particle size distribution analyzer (Shimadzu SALD-300 manufactured by Shimadzu Corporation or an equivalent device). Approximately 0.1 g of the sample, a surfactant, and 1-2 mL of distilled water are added to a beaker and thoroughly mixed. This mixture is then poured into a stirring tank, and the photometric distribution is measured 64 times at 2-second intervals. The average particle size is then obtained from the resulting particle size distribution data. (Second embodiment) A method for manufacturing electrodes is provided according to a second embodiment. The method of the second embodiment includes the steps of: preparing a slurry containing an active material containing lithium titanium oxide (first and second lithium titanium oxides) obtained by the method of the first embodiment and a binder; applying the slurry to a second current collector; drying the resulting laminate; and pressing the laminate. A cutting step may be performed to make the electrodes to the desired size. Cutting can be performed before or after pressing.

[0057] The electrodes can be manufactured by a method including steps S11 to S15, as illustrated in Figure 5. Steps S11 to S15 will be described below. <Process S11> A slurry is prepared using a second mixture containing the active material obtained by the method of the first embodiment. The amount of active material is equal to or less than the amount before recycling (initial value). Therefore, the amount of active material in the second mixture can be estimated based on the composition of the active material-containing layer of the first electrode (target electrode). Also, the conductive agent may disappear in the second heat treatment and not be included in the second mixture. A conductive agent, binder, and solvent are added to the second mixture containing the active material to achieve the desired composition. Active material may be added as needed. After addition, the slurry is prepared by mixing these. An example of a solvent is an organic solvent such as n-methyl-2-pyrrolidone (NMP). The composition of the slurry may be the same as the composition of the active material-containing layer of the first electrode, but it may also be different. For example, the types of conductive agent and binder in the slurry may be different from the types of conductive agent and binder contained in the first electrode.

[0058] Alternatively, the amount of active material in the second mixture may be measured, and based on the obtained measurement, the active material, conductive agent, binder, and solvent may be added to the second mixture and mixed to prepare the slurry.

[0059] Before preparing the slurry, the second mixture may be ground. Grinding allows the particle size of the second mixture to be set within the desired range. <Process S12> The slurry is applied to the second current collector.

[0060] The coating is applied to at least a portion of the second current collector. For example, the slurry can be applied to one or both main surfaces of the second current collector. The main surfaces of the second current collector are, for example, surfaces that define the thickness of the second current collector or surfaces that intersect the thickness direction of the second current collector.

[0061] The second current collector may be the first current collector separated from the first electrode, or it may be an unused current collector. Furthermore, the second current collector may be a different current collector from the first current collector. <Process S13> The coated slurry is dried. This forms an active material-containing layer on the second current collector. As an example, when the total mass of the active material-containing layer is 100% by mass, the active material, conductive agent, and binder may be blended in the following proportions: 68% to 96% by mass, 2% to 30% by mass, and 2% to 30% by mass, respectively. <Process S14> The second current collector, on which the active material-containing layer is supported, is pressed. This yields an electrode. In order to set the obtained electrode to a predetermined shape or size, the electrode may be cut as shown in step S15.

[0062] Since the active material is mixed once during the manufacturing of the first electrode, its surface properties (hydrophilicity, hydrophobicity, etc.) are kept stable. As a result, newly manufactured electrodes have improved adhesion between the active material-containing layer and the second current collector, and also exhibit superior charge and discharge efficiency. <Process S15> The electrodes are cut to set them to a predetermined shape or size. If the electrodes after pressing have the desired shape or size, step S15 can be omitted.

[0063] The manufactured electrode can have a structure similar to that of the first electrode. The details of the structure are illustrated in Figures 2 to 4.

[0064] Alternatively, instead of steps S11 to S15, the following method may be used: Active material, conductive agent, and binder are added to a mixture containing the active material to achieve the desired composition, and these are mixed. The resulting mixture is then formed into pellets. The electrodes are then obtained by placing the pellets on a current collector.

[0065] According to the electrode manufacturing method of the second embodiment described above, electrodes can be manufactured using active material recycled by the method of the first embodiment. Therefore, the recycling efficiency of electrodes can be improved. (Third embodiment) The third embodiment is a method for manufacturing a battery using electrodes manufactured in the second embodiment. The third embodiment includes manufacturing electrodes using the method of the 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 may include a positive electrode in addition to the negative electrode. The electrode group may also include a separator.

[0066] Figure 6 shows a flowchart illustrating an example of the manufacturing process for the battery according to the third embodiment. First, a waste electrode 11 is prepared as the first electrode 1. The waste electrode 11 is, for example, an electrode that is not up to standard, an electrode that has been stored unused, or a fragment of an electrode such as a piece generated by cutting. Alternatively, the waste electrode 11 may be an electrode taken from an unfilled waste battery 12 that may be generated in the battery manufacturing process. An unfilled waste battery 12 is a battery in which the necessary components such as electrodes are contained in the container, but the electrolyte was not filled due to reasons such as being out of standard. An example of how to remove it from the battery will be described later. In any case, the waste electrode 11 does not contain electrolyte. The composition of the active material-containing layer of the waste electrode 11 is known. Also, since the waste electrode 11 has not been charged or discharged, the degradation of the active material has hardly progressed. Therefore, by recycling the active material separated from the waste electrode 11, an electrode with an active material-containing layer having the same composition as the active material-containing layer of the waste electrode 11 can be easily regenerated.

[0067] A second mixture containing the active material is obtained from the waste electrode 11 by steps S1 to S4. The details of steps S1 to S4 are as described in the first embodiment.

[0068] Next, the electrodes are manufactured, for example, according to steps S11 to S15.

[0069] First, a slurry is prepared using the dispersion shown in step S11, i.e., the second mixture. The details of step S11 are as described in the second embodiment.

[0070] Next, the electrodes are manufactured by performing the coating, drying, pressing, and cutting processes shown in steps S12 to S15 in that order. The details of steps S12 to S15 are as described in the second embodiment.

[0071] Next, as the assembly step S21, after manufacturing an electrode group including the manufactured electrode as a negative electrode, the electrode group is housed in an exterior member. The electrode group is manufactured, 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 a positive electrode, a separator, and a negative electrode are laminated, those in which a positive electrode, a separator, and a negative electrode are wound in a flat or cylindrical shape, those in which a positive electrode, a separator, and a negative electrode are bent into a ninety-fold shape, etc. can be used.

[0072] Subsequently, as the electrolyte injection step S22, after causing the electrode group housed in the exterior member to hold an electrolyte, the exterior member is sealed.

[0073] Thereafter, as the processing step S23 for commercialization, initial charging, aging, etc. are performed to obtain a battery.

[0074] Examples of the positive electrode, separator, electrolyte, and exterior member used in the above steps will be described. <Positive electrode> The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer carried on one side (one main surface) or both surfaces of the current collector and containing a positive electrode active material. The positive electrode active material-containing layer contains a positive electrode active material. The positive electrode active material-containing layer may contain a binder, a conductive agent, or both.

[0075] Examples of the positive electrode active material include Li x M y O2 (0 < x ≤ 1, 0 < y ≤ 1, M is, for example, Mn), Li x M 2y O4 (0 < x ≤ 1, 0 < y ≤ 1, M is, for example, Mn), lithium phosphate having an olivine structure (for example, Li x M y PO4 (M is at least one element selected from Mn, Ni, Co, Fe, 0 < x ≤ 1.1, 0.8 ≤ y ≤ 1.1), Li x FePO4 (0 < x ≤ 1.1), Li x Fe 1-y Mn y PO4 (0 < x ≤ 1.1, 0 ≤ y ≤ 1), Li x CoPO4 (0 < x ≤ 1.1), Li x MnPO4(0 < x ≤ 1.1)), lithium nickel cobalt composite oxide (e.g., LixNi 1-a Co a O2, 0 < x ≤ 1, 0 < a ≤ 1), lithium cobalt composite oxide (e.g., Li x CoO2, 0 < x ≤ 1), lithium nickel manganese cobalt composite oxide (e.g., Li x Ni 1-a-b Mn a Co b O2, 0 < x ≤ 1, 0 < 1 - a - b < 1, 0 < a < 1, 0 < b < 1), lithium manganese cobalt composite oxide (e.g., Li x Mn 1-a Co a O2, 0 < x ≤ 1, 0 < a < 1), spinel - type lithium manganese nickel composite oxide (e.g., Li x Mn 2-a Ni a O4, 0 < x ≤ 1, 0 < a < 2), fluorinated iron sulfate having a tabularite structure (e.g., Li x M y SO4F(0 < x ≤ 1, 0 < y ≤ 1, M is at least one of Fe or Mn), Li x Fe 1-a Mn a SO4F(0 < x ≤ 1, 0 < a ≤ 1), etc. are included. The type of the positive electrode active material can be one type or two or more types.

[0076] The positive electrode active material - containing layer may contain a conductive agent. Examples of the conductive agent include acetylene black, carbon black, graphite, etc. The type of the conductive agent can be one type or two or more types.

[0077] The positive electrode active material - containing layer may contain a binder. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine - based rubber, acrylic - based materials, etc. The type of the binder can be one type or two or more types.

[0078] The positive electrode current collector may contain at least one of aluminum or an aluminum alloy. For example, aluminum foil or aluminum alloy foil can be used as the positive electrode current collector.

[0079] The mixing ratio of the positive electrode active material, conductive agent, and binder is preferably in the range of 80-95% by mass for the positive electrode active material, 3-19% by mass for the conductive agent, and 1-7% by mass for the binder.

[0080] The positive electrode can be manufactured, for example, by suspending a positive electrode active material, a conductive agent, and a binder in a suitable solvent, coating this suspension onto a positive electrode current collector, drying it, and pressing it. Alternatively, the positive electrode may be manufactured by the following method: First, the active material, conductive agent, and binder are mixed to obtain a mixture. Next, this mixture is formed into pellets. Then, these pellets are placed on a current collector to obtain an electrode. <Separator> For the separator, for example, a porous film, a nonwoven fabric made of synthetic resin, or a solid electrolyte layer can be used. <Electrolyte> 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). <Exterior components> For example, the outer packaging material can be a container made of laminate film or a metal container.

[0081] The shape of the exterior components is not particularly limited. For example, the exterior components may be flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior components can be appropriately selected according to the battery dimensions and intended use.

[0082] The batteries manufactured by the embodiments are not particularly limited. Examples of batteries include batteries with an aqueous electrolyte and batteries with a non-aqueous electrolyte. Furthermore, the batteries may be individual cells, battery packs, or battery arrays.

[0083] The batteries manufactured by the method of the embodiment may be used as battery packs or incorporated into battery packs. The batteries according to the embodiment are suitable for use in applications where excellent cycle performance is required when drawing high current. Specifically, they can be used as power sources for digital cameras, or as batteries for vehicles such as 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 stationary batteries. They are particularly suitable for use as on-board batteries mounted in vehicles.

[0084] An example of a battery (secondary battery) will be described with reference to Figures 7 and 8. Figure 7 is a partially cutaway perspective view showing a non-aqueous electrolyte secondary battery, which is an example of a battery. Figure 8 is an enlarged cross-sectional view of part A of the non-aqueous electrolyte secondary battery shown in Figure 7. As shown in Figure 7, 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.

[0085] 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 8, 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 8, 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.

[0086] As shown in Figure 7, 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.

[0087] Here, we will describe an example of a method for removing electrodes from an unfilled waste battery 12. An unfilled waste battery 12 is, for example, an off-spec battery that may be generated before the electrolyte filling process S22 during battery manufacturing. First, the outer casing is separated from the unfilled waste battery 12. Next, the positive and negative electrodes contained in the battery from which the outer casing has been removed are separated. The details of each step will be described below. <Exterior separation> The unfilled waste battery 12 is disassembled and the outer casing is separated. An outer casing separation device may be used for this purpose.

[0088] 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.

[0089] 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. Note that 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 the functions of outer casing separation and positive / negative electrode separation.

[0090] The electrodes (e.g., the negative electrode) separated from the unfilled waste battery 12 by the external separation and positive / negative electrode separation described above are subjected to recycling treatment according to a method including steps S1 to S4.

[0091] According to the third embodiment, since the battery is manufactured using electrodes regenerated by the method of the second embodiment, it is possible to manufacture batteries with a high recycling rate. Furthermore, since the regenerated electrodes have excellent electronic conductivity and can suppress the degradation of the active material, it is possible to realize a battery with superior durability. [Examples]

[0092] The following describes an example of the active material recycling method of the embodiment. First, the first electrode (target electrode) is removed from the unfilled waste battery. If the outer casing of the unfilled waste battery is a metal can, the first electrode is removed using the method described below. The unfilled waste battery 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. This electrode group is then subjected to a positive / negative electrode separation device provided in the chamber to separate it into a positive electrode, a separator, and a negative electrode. For example, a negative electrode is used as the first electrode. A positive electrode can also be used instead of a negative electrode.

[0093] (Example 1) The first electrode, the negative electrode, comprises a negative electrode active material-containing layer containing 90% by mass of negative electrode active material, 5% by mass of graphite as a conductive agent, and 5% by mass of PVdF as a binder, and a first current collector made of aluminum foil. The negative electrode active material is lithium titanate Li4Ti5O, which has a spinel structure. 12 It consists of particles. Moisture in the negative electrode was removed by drying it in air at 100°C for 1 hour. Next, the first heat treatment (referred to as the first heat treatment) was performed by heating it to 400°C in air at a heating rate of 10°C / min and firing it at 400°C for 2 hours.

[0094] The calcined material of the first current collector was separated from the obtained calcined material by sieving. This yielded a first mixture containing negative electrode active material, TiO2, conductive agent, and LiF. The fluorine (F) concentration of the first mixture was measured by the method described above, and the measured values ​​shown in Table 1 were obtained.

[0095] Next, the first mixture was subjected to a heat treatment at a second temperature (second heat treatment), which involved firing in air at 700°C for 1 hour. The temperature and time of the second heat treatment are shown in Table 1. The fluorine (F) concentration of the second mixture obtained by the second heat treatment was measured using the method described above, and the measured values ​​shown in Table 1 were obtained.

[0096] The powder X-ray diffraction pattern (Cu-Kα) of the second mixture was measured using the method described above, and the results are shown in Figure 9. Figure 9 also shows the powder X-ray diffraction pattern (Cu-Kα) of the first mixture, measured using the same method. In Figure 9, the peaks appearing around 18°, 36°, 43°, 47°, 57°, and 63° of 2θ(Cu-Kα) are Li4Ti5O 12 This is a peak specific to [the function]. As is clear from Figure 9, the second mixture obtained by the method of Example 1 is Li4Ti5O 12 It contained rutile-type TiO2 and anatase-type TiO2. On the other hand, the first mixture before the second heat treatment contained Li4Ti5O 12 The solution contained rutile-type TiO2, anatase-type TiO2, and graphite. Figure 9 shows that the peak originating from graphite 2H disappeared after the second heat treatment.

[0097] To the second mixture, 10% by mass of graphite, 5% by mass of PVdF, and NMP as a solvent were added, and the mixture was stirred to prepare a slurry. The obtained slurry was coated onto a second current collector made of aluminum foil, then dried and pressed to produce the negative electrode of Example 1.

[0098] (Examples 2-5) The negative electrode was prepared in the same manner as in Example 1, except that the temperature and time in the second heat treatment were set as shown in Table 1 below.

[0099] Figure 9 shows the powder X-ray diffraction pattern (Cu-Kα) of the second mixture from Example 2-5. As is clear from Figure 9, the second mixture obtained by the method of Example 2-4 is Li4Ti5O 12 It contained rutile-type TiO2. On the other hand, the second mixture obtained by the method of Example 5 contained Li4Ti5O 12 Although it contained [something], neither rutile-type TiO2 nor anatase-type TiO2 was detected.

[0100] Coin cells with metallic Li as the counter electrode were fabricated using the electrodes prepared in each example, and their battery characteristics were evaluated. The discharge capacity (mAh / g) at 0.1C is shown in Table 1. The discharge capacity at 0.1C is the discharge capacity obtained when the battery is charged to 1.2V with a constant current of 0.1C, then charged with a constant voltage of 1.2V, charging is stopped when the current reaches 1 / 100, and then discharged to 2V with a constant current of 0.1C. All F in the PVdF contained in the target electrode is Li4Ti5O 12 It reacts with LiF to form Li4Ti5O, and all the Li in LiF is converted to Li4Ti5O 12 The theoretical capacity (mAh / g) when these are combined is also listed as a reference example.

[0101] [Table 1]

[0102] As is clear from Table 1, the methods of Examples 1-5 allowed for the recycling of lithium titanium-containing oxide extracted from the electrodes, resulting in electrodes with practical capacity. The methods of Examples 1-3 were able to achieve a higher battery discharge capacity than the theoretical capacity of the reference example. This is because the temperature of the second heat treatment was less than 900°C, which suppressed the grain growth of lithium titanate while synthesizing lithium titanate with a spinel structure. Furthermore, a comparison of Examples 1-3 shows that the method of Example 3, in which the F concentration of the second mixture is less than half the F concentration of the first mixture, yields a higher capacity.

[0103] According to the active material recycling method of at least one embodiment or example described above, by heat-treating the electrodes at a first temperature below the melting point of the first current collector, the fluorine-containing binder can be reduced by decomposition, allowing the first current collector to be easily separated from the heat-treated material without pulverizing the resulting heat-treated material. By heat-treating the separated mixture at a second temperature, lithium titanium-containing oxide can be synthesized without adding new raw materials such as Li. Therefore, lithium titanium-containing oxide can be efficiently regenerated. Furthermore, since active material can be regenerated from waste materials that may be generated in the manufacturing process, the amount of waste material can be reduced. This increases the recycling rate of active material. It also reduces manufacturing costs.

[0104] 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.

[0105] The invention according to the embodiment is described below. <1> A step of heat-treating an electrode, which includes a first current collector and an active material-containing layer supported on the first current collector and containing a first lithium titanium-containing oxide, a fluorine-containing binder, and a conductive agent, at a first temperature below the melting point of the first current collector, A step of separating the first current collector from the heat-treated product to obtain a mixture containing the active material, the titanium-containing material, the conductive agent, and a fluorine compound with a fluorine concentration of 5000 ppm by mass or more and 22000 ppm by mass or less, A step of synthesizing a lithium titanium-containing oxide by heat-treating the mixture at a second temperature higher than the first temperature. A recycling method for active materials, including [the specified material]. <2> The titanium-containing material is a decomposition product of the first lithium titanium-containing oxide. <1> The recycling method for the active material described in [the document]. <3> The aforementioned titanium-containing material is titanium oxide. <1> or <2> The recycling method for the active material described in [the document]. <4> The first temperature is between 300°C and 500°C. <1> ~ <3> A recycling method for active materials as described in any of the following. <5> The second temperature is between 700°C and 1000°C. <1> ~ <4> A recycling method for active materials as described in any of the following. <6> The fluorine compound includes lithium fluoride. <1> ~ <5> A recycling method for active materials as described in any of the following. <7> The process further includes drying the electrode before heat treatment at the first temperature, <1> ~ <6> A recycling method for active materials as described in any of the following. <8> The fluorine concentration of the mixture that has been heat-treated at the second temperature is less than the fluorine concentration of the mixture before heat treatment at the second temperature. <1> ~ <7> A recycling method for active materials as described in any of the following. <9> <1> ~ <8> Active material recycled by any one of the methods described in item 1. <10> <1> ~ <8> A step of preparing a slurry containing active material recycled by the method of any one of the items and a binder, The process involves applying the slurry to the second current collector. A method for manufacturing electrodes, including <11> <1> ~ <8> An electrode comprising an active material recycled by the method described in any one of the items. [Explanation of Symbols]

[0106] 1...First electrode (target electrode), 2...First current collector, 3...Active material containing layer, 11...Waste electrode, 12...Unfilled waste battery, 20...Nonaqueous electrolyte battery, 21...Metallic container, 22...Electrode group, 23...Made of 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...drying of electrodes, S2...heat treatment of electrodes at a first temperature, S3...separation of the first current collector from the heat-treated material, S4...heat treatment of the mixture at a second temperature, S11...slurry preparation (dispersion), S12...coating, S13...drying, S14...pressing, S15...cutting, S21...assembly, S22...liquid injection, S23...product. < / gc>

Claims

1. A step of heat-treating an electrode, which includes a first current collector and an active material-containing layer supported on the first current collector and containing a first lithium titanium-containing oxide, a fluorine-containing binder, and a conductive agent, at a first temperature below the melting point of the first current collector, A step of separating the first current collector from the heat-treated product to obtain a mixture containing the active material, the titanium-containing material, the conductive agent, and a fluorine compound with a fluorine concentration of 5,000 ppm by mass or more and 22,000 ppm by mass or less, A step of synthesizing a lithium titanium-containing oxide by heat-treating the mixture at a second temperature higher than the first temperature. A recycling method for active materials, including [the specified material].

2. The method for recycling an active material according to claim 1, wherein the titanium-containing material is a decomposition product of the first lithium titanium-containing oxide.

3. The method for recycling an active material according to claim 1, wherein the titanium-containing material is titanium oxide.

4. The method for recycling active material according to claim 1, wherein the first temperature is 300°C or more and 500°C or less.

5. The method for recycling active material according to claim 1, wherein the second temperature is 700°C or more and 1000°C or less.

6. The method for recycling an active material according to claim 1, wherein the fluorine compound includes lithium fluoride.

7. The method for recycling an active material according to claim 1, further comprising the step of drying the electrode before heat treatment at the first temperature.

8. The method for recycling an active material according to claim 1, wherein the fluorine concentration of the mixture heat-treated at the second temperature is less than the fluorine concentration of the mixture before heat-treatment at the second temperature.

9. Active material recycled by the method described in any one of claims 1 to 8.

10. A step of preparing a slurry containing an active material recycled by the method of any one of claims 1 to 8 and a binder, The process of applying the slurry to the second current collector A method for manufacturing electrodes, including

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