Method for treating positive electrode of non-aqueous electrolyte secondary battery, and molded body

Abstract

To provide a method for processing a positive electrode of a nonaqueous electrolyte secondary battery, capable of promoting the reduction reaction of the positive electrode at low cost, and a molded body.SOLUTION: Provided is a method for processing a positive electrode of a nonaqueous electrolyte secondary battery, the nonaqueous electrolyte secondary battery including a positive electrode having an Al-containing foil and an active material that is a metal composite oxide. The method includes: a preparation step S10 of preparing the positive electrode; a heating step S11 in which the positive electrode is subjected to heat treatment; a consolidation step S12 in which the positive electrode subjected to the heat treatment is subjected to compression molding to form a molded body; a melting step S13 of obtaining a melt by melting the molded body using the heat of a reaction between the foil and the active material; and a separation step S14 of separating the melt into a slag and a metal material containing a metal constituting the metal composite oxide.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for treating a positive electrode of a non-aqueous electrolyte secondary battery and a molded body.

Background Art

[0002] Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries are used as power sources mounted on hybrid vehicles and electric vehicles, and in recent years, the demand has been rapidly increasing. Along with the increasing demand for non-aqueous electrolyte secondary batteries, the amount of used non-aqueous electrolyte secondary batteries, defective non-aqueous electrolyte secondary batteries, and process scraps generated in the manufacturing process also tends to increase. The electrodes of non-aqueous electrolyte secondary batteries, particularly the positive electrodes, contain valuable substances such as nickel (Ni) and cobalt (Co). In order to effectively utilize resources, methods for recovering valuable substances such as Ni and Co from non-aqueous electrolyte secondary batteries have been proposed.

[0003] For example, Patent Document 1 describes a method for recovering cobalt from secondary battery waste products, in which the battery waste products are roasted at 600 °C or higher and then cut, sieved, magnetically separated, and acid-dissolved to recover cobalt.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the recovery method described in Patent Document 1, processes such as magnetic separation and acid dissolution are required after roasting, so there is a problem that the recycling cost becomes high.

[0006] As one of the methods for recovering metals containing valuable substances from a positive electrode active material composed of a metal composite oxide, there is the "thermit method". In the thermit method, it is common to use raw materials in a powder state. If the positive electrode metal foil is directly subjected to the thermit reaction, external heating at a high temperature using a high-frequency induction melting furnace or the like is required, which becomes an obstacle to cost reduction. Further, in the thermit method, continuous processing cannot be performed and it is a batch process, so there is a problem that the cost increases if the processing amount per batch is small.

[0007] Therefore, an object of the present invention is to provide a method for treating a positive electrode of a non-aqueous electrolyte secondary battery and a molded body that can promote the reduction reaction of the positive electrode at low cost.

Means for Solving the Problems

[0008] The method for treating a positive electrode of a non-aqueous electrolyte secondary battery according to the present invention is a method for treating a positive electrode of a non-aqueous electrolyte secondary battery including a foil containing Al and an active material as a metal composite oxide, comprising: a preparation step of preparing the positive electrode; a heating step of performing a heat treatment for heating the positive electrode; a consolidation step of compression molding the positive electrode that has undergone the heat treatment to form a molded body; a melting step of melting the molded body by the reaction heat between the foil and the active material to obtain a melt; and a separation step of separating the melt into a metal material containing a metal constituting the metal composite oxide and slag.

[0009] The molded body according to the present invention has a configuration in which a positive electrode of a non-aqueous electrolyte secondary battery including a foil containing Al and an active material as a metal composite oxide is compression molded, and the content of the binder is 1% by mass or less.

Effects of the Invention

[0010] According to the present invention, by compression molding the positive electrode that has undergone the heat treatment, a molded body with improved bulk density is provided to the melting step, so that the reduction reaction of the positive electrode active material can be promoted at low cost.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0012] 1. Embodiment Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0013] FIG. 1 is a perspective view of a non-aqueous electrolyte secondary battery 10 used in a method for treating a positive electrode of a non-aqueous electrolyte secondary battery according to this embodiment. The non-aqueous electrolyte secondary battery 10 is a used lithium-ion secondary battery used as a power source for automobiles such as electric vehicles and hybrid vehicles. In the following description, the case where the non-aqueous electrolyte secondary battery 10 is a lithium-ion secondary battery will be described as an example, but the non-aqueous electrolyte secondary battery 10 is not limited to a lithium-ion secondary battery, and may be a magnesium-ion secondary battery, a sodium-ion secondary battery, a potassium-ion secondary battery, a calcium-ion secondary battery, etc. The non-aqueous electrolyte secondary battery 10 is not limited to used ones, and may also be an unused non-aqueous electrolyte secondary battery in which defects are confirmed after manufacture. Further, the positive electrode used in the method for treating the positive electrode of the non-aqueous electrolyte secondary battery according to this embodiment may be a positive electrode taken out from a used non-aqueous electrolyte secondary battery, a positive electrode taken out from an unused non-aqueous electrolyte secondary battery, a positive electrode taken out from process scraps (for example, defective products of electrode bodies) in the manufacturing process of the non-aqueous electrolyte secondary battery, process scraps in the manufacturing process of the positive electrode, etc.

[0014] The non-aqueous electrolyte secondary battery 10 includes an electrode body (not shown) and a non-aqueous electrolyte (not shown) in a cell container 12. The cell container 12 is made of, for example, an aluminum alloy. The cell container 12 includes a container body 14 and a lid 16. The container body 14 and the lid 16 are laser welded. The container body 14 is formed in a bottomed rectangular tube shape and houses the electrode body and the non-aqueous electrolyte therein. The lid 16 is provided at the opening of the container body 14 and seals the container body 14. A safety valve 18, a positive electrode terminal 20, and a negative electrode terminal 22 are provided on the lid 16. The safety valve 18 is for reducing the pressure inside the non-aqueous electrolyte secondary battery 10. The positive electrode terminal 20 is connected to a positive electrode (not shown) described later via a positive electrode lead (not shown). The negative electrode terminal 22 is connected to a negative electrode (not shown) described later via a negative electrode lead (not shown).

[0015] The electrode body includes a positive electrode (not shown) and a negative electrode (not shown) wound with a separator (not shown) therebetween. The electrode body is not limited to the wound type as described above, and may be a laminated type in which the positive electrode, the negative electrode, and the separator are laminated.

[0016] The positive electrode has a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is a foil containing aluminum (Al) (hereinafter also referred to as Al foil). The mass ratio of the positive electrode current collector in the positive electrode is 5 to 25% by mass. The positive electrode active material layer includes a positive electrode active material, a binder, and a conductive material. The mass ratios of the conductive material and the binder in the positive electrode active material layer are 0 to 30% by mass and 0 to 20% by mass of the positive electrode, respectively.

[0017] As the positive electrode active material, any metal composite oxide containing nickel (Ni) and / or cobalt (Co) can be used. For example, the positive electrode active material can be selected from lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium nickel manganese composite oxide, lithium nickel cobalt aluminum composite oxide, lithium nickel cobalt manganese composite oxide, etc. In the present embodiment, the positive electrode active material is a lithium nickel cobalt manganese composite oxide. Note that, in the case of a magnesium ion secondary battery, any magnesium composite oxide can be used as the positive electrode active material; in the case of a sodium ion secondary battery, any sodium composite oxide can be used; in the case of a potassium ion secondary battery, any potassium composite oxide can be used; and in the case of a calcium ion secondary battery, any calcium composite oxide can be used.

[0018] The binder is a fluorine-based binder containing a fluorine compound such as polyvinylidene fluoride (PVDF). The binder is not limited to fluorine-based binders, and polyimide-based binders, SBR (styrene butadiene rubber) - based binders, inorganic binders, etc. may also be used. The conductive material is a carbon material such as graphite and carbon black.

[0019] The negative electrode has a negative electrode current collector and a negative electrode active material layer. For example, the negative electrode current collector is a copper (Cu) foil, and the negative electrode active material is graphite. Generally, a porous film or non-woven fabric made of resin such as polyethylene (PE) and polypropylene (PP) is used as the separator.

[0020] The non-aqueous electrolyte contains a non-aqueous solvent and a lithium salt (electrolyte) soluble in this non-aqueous solvent. As the non-aqueous solvent, carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc. are used. These non-aqueous solvents can be used alone or in combination of two or more.

[0021] As the electrolyte, those containing a fluorine compound are used, for example, LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiTFSA (lithium trifluoromethanesulfonylamide), LiTFSI (lithium bis(trifluoromethane)sulfonimide), etc. These electrolytes can be used alone or in combination of two or more kinds.

[0022] As shown in FIG. 2, the method for treating the positive electrode of the non-aqueous electrolyte secondary battery 10 is a method for treating the positive electrode of a non-aqueous electrolyte secondary battery including a foil containing Al and a positive electrode active material as a metal composite oxide, including a preparation step S10 of preparing a positive electrode, a heating step S11 of performing a heat treatment of heating the positive electrode, a consolidation step S12 of compression molding the positive electrode that has undergone the heat treatment to form a molded body, a melting step S13 of melting the molded body by the reaction heat between the foil and the active material to obtain a melt, and a separation step S14 of separating the melt into a metal material containing the metal constituting the metal composite oxide and slag. Here, the "reaction between the foil and the active material" is an oxidation-reduction reaction that generates high heat while reducing the metal oxide with metal Al when a mixture of the positive electrode current collector, which is metal Al, and the positive electrode active material, which is a metal oxide, is reacted, and is also called a thermite reaction. The molded body obtained by compression molding the positive electrode self-heats due to the reaction heat between the foil and the active material. "Self-heating" means that the temperature of the molded body rises due to the reaction heat between the foil and the active material without applying heat energy from an external heating means (for example, a high-frequency induction melting furnace) to the molded body. Each step will be described in detail below.

[0023] [Preparation Step] In the preparation step S10, a sheet-shaped positive electrode is prepared by unwinding the wound electrode body taken out by opening the cell container 12. The sheet-shaped positive electrode is subjected to the heating step S11, which is the next step. In the preparation step S10, a discharging step of discharging the non-aqueous electrolyte secondary battery 10, a cell internal cleaning step of cleaning the inside of the cell container 12 of the discharged non-aqueous electrolyte secondary battery 10 with a cleaning liquid, etc. may be performed. The positive electrode prepared in the preparation step S10 is the positive electrode taken out from the used non-aqueous electrolyte secondary battery 10 in the present embodiment, but is not limited thereto, and may be a positive electrode taken out from an unused non-aqueous electrolyte secondary battery, a positive electrode taken out from process scraps in the manufacturing process of the non-aqueous electrolyte secondary battery, or process scraps in the manufacturing process of the positive electrode. It is preferable to prepare only the positive electrode in the preparation step S10. This is because if members other than the positive electrode (the cell container 12, the separator, the negative electrode, etc.) are included in the melting step S13, the thermite reaction will be inhibited.

[0024] [Heating Step] In the heating step S11, heat treatment is performed on the sheet-shaped positive electrode obtained in the preparation step S10. The heat-treated positive electrode is subjected to the consolidation step S12, which is the next step. By the heat treatment, the thermite reaction in the melting step S13 is promoted, and it becomes possible to melt the molded body described later and reduce the active material.

[0025] The heat treatment will be described. The heating device used for the heat treatment includes a heating furnace, a heating unit, a thermometer, a gas supply unit, a flow meter, and a control unit. The heating furnace has an internal space for accommodating the positive electrode. The heating unit heats the positive electrode disposed in the heating furnace. The thermometer measures the temperature inside the heating furnace. The gas supply unit supplies a gas containing oxygen (air in this example) into the heating furnace to create an atmosphere containing oxygen inside the heating furnace. The flow meter measures the flow rate of the air inside the heating furnace. The control unit controls the heating unit based on the measurement result of the thermometer, raises the temperature inside the heating furnace at a predetermined heating rate, and controls it to a preset heating temperature. The control unit controls the gas supply unit based on the measurement result of the flow meter to control the flow rate of the air supplied into the heating furnace. The control unit controls the heating unit and the gas supply unit so that the heating temperature and the flow rate are maintained for a predetermined time. The time for maintaining the heating temperature and the flow rate is referred to as the "keep time". Note that the above heating device is an example. Therefore, the configuration of the heating device is not limited to the above configuration and can be designed as appropriate.

[0026] The heat treatment involves putting the positive electrode prepared in the preparation step S10 into the heating device and heating the positive electrode in an atmosphere containing oxygen at a preset heating temperature until a preset keep time elapses.

[0027] It is preferable to perform the heat treatment at a temperature at which the Al foil does not oxidize. If the heating temperature is too high, Al will oxidize, and in the thermite process in the melting step S13, that is, in the reaction due to the reaction heat between the foil and the active material, the Al foil cannot be used as a reducing agent. Also, when alumina is generated so as to cover the surface of the Al foil, it hinders the contact between the active material and Al and inhibits the reaction. By performing the heat treatment at a temperature at which the Al foil does not oxidize, the positive electrode containing Al that can be used as a reducing agent can be subjected to the consolidation step S12.

[0028] The heat treatment is preferably carried out at a temperature that decomposes the binder. If the heating temperature is too low, the decomposition of the binder will be insufficient and the binder will remain in the positive electrode. When the binder remains in the positive electrode, in the melting step S13, gases such as hydrogen and carbon oxides such as H2O, CO2, and CO are generated due to the thermal decomposition of the binder and subsequent oxidation, and the thermite reaction is inhibited. The gas that inhibits the thermite reaction is referred to as a reaction-inhibiting gas. Also, there is a risk that the generated gas expands rapidly and the molten metal spurts out or explodes, which is dangerous. By performing the heat treatment at a temperature that decomposes the binder, the molded body described later from which the binder has been removed can be subjected to the melting step S13. In the heating step S11, it is desirable to completely remove the binder contained in the positive electrode, but a small part of the binder contained in the positive electrode may remain slightly. Also, the heat treatment is preferably carried out at a temperature that oxidizes and removes the conductive material.

[0029] The heat treatment is preferably carried out by heating at 400°C or higher and 650°C or lower. By setting the heating temperature to 400°C or higher and 650°C or lower, the binder is surely decomposed and the conductive material is oxidized and removed. Furthermore, oxidation of the Al foil can be suppressed. When the heat treatment of the positive electrode is carried out at a heating temperature of 660°C or higher, which is the melting point of aluminum, it is considered that the oxide film of the Al foil is broken and the oxidation reaction easily proceeds. Also, if the heating temperature is too high, alumina is formed between the metallic Al and the active material, the contact portion between the Al foil and the positive electrode active material decreases, and the thermite reaction is inhibited. Furthermore, there is a risk that Al of the positive electrode current collector becomes a reducing agent and an unintended thermite reaction occurs, which is dangerous. The heat treatment is more preferably 450°C or higher and 600°C or lower, and even more preferably 500°C or higher and less than 600°C.

[0030] The concentration of carbon derived from the binder and the conductive material in the positive electrode can be reduced by the heat treatment. The concentration (mass ratio) of carbon in the positive electrode after the heat treatment is preferably 0.7 wt% or less, more preferably 0.5 wt% or less, and even more preferably 0.4 wt% or less.

[0031] Note that the positive electrode to be subjected to heat treatment may be in the form of a sheet, or may be, for example, cut into thin strips using a shredder or the like, or cut into pieces about 1 mm to 2 mm with a crusher, and may include those in a powdered form. By cutting, a reduction in the heat treatment time is expected. However, from the viewpoint of setting the heating conditions according to the size of the positive electrode to be supplied to the heating device, a positive electrode with a relatively uniform size is preferable. Note that the heating conditions have an upper limit of a temperature at which the Al foil is not oxidized and a lower limit of a temperature at which the binder and the conductive material are sufficiently decomposed and removed. Further, when using a heating device capable of continuously performing heat treatment such as a rotary kiln, any positive electrode having a size that can be continuously charged into the heating device may be used. On the other hand, when cutting, the bulk density decreases accordingly. The present invention is to improve the bulk density and can address this problem.

[0032] A combustion aid may be mixed with the positive electrode that has undergone the heating step S11, and the positive electrode mixed with the combustion aid may be supplied to the subsequent consolidation step S12. As the combustion aid, for example, a powder containing Al and NaClO3 (sodium chlorate) is used. By mixing the combustion aid with the positive electrode, the combustion of the compact is promoted in the melting step S13, and the thermite reaction can be further promoted.

[0033] [Consolidation Step] In the consolidation step S12, a compact is formed that has a structure in which a positive electrode having a foil containing Al and an active material as a metal composite oxide is compression-molded by performing consolidation processing on the positive electrode heat-treated in the heating step S11. The compact is subjected to the next step, which is the melting step S13. The consolidation processing is a process of compressing the positive electrode to increase its density. By compressing the positive electrode through the consolidation processing, the bulk density can be improved, and the processing amount per batch in the melting step S13, which is the next step, can be increased. As the bulk density increases, the heat generation amount per unit volume during the thermite reaction in the melting step S13 increases. By compression-molding the positive electrode, the distance between the Al foil and the positive electrode active material becomes smaller, and the contact area between the Al foil and the positive electrode active material becomes larger, so the thermite reaction in the melting step S13 is promoted. The compact in which the positive electrode is compression-molded has an increased heat generation amount per unit volume during the thermite reaction in the melting step S13, the thermite reaction is promoted, and the yield and purity of the metal material can be improved. Since the compact formed by the consolidation processing is not easily deformed, it is easier to handle during movement, storage, etc. compared to a sheet-shaped positive electrode or a powder-shaped positive electrode. In the consolidation step S12, the positive electrode can be compression-molded using a general compression device such as a hydraulic press, a roller compactor, or a briquetting machine.

[0034] In the consolidation step S12, it is preferable to compress and mold the positive electrode without adding a binder. When a binder is added in the melting step S13, reaction-inhibiting gases are generated due to thermal decomposition of the added binder and subsequent oxidation, inhibiting the thermite reaction. Also, the generated gas may rapidly expand, causing the molten metal to spurt out or explode, which is dangerous. Furthermore, the contact between the positive electrode active material and Al is hindered. Also, the volume fraction of the binder in the entire molded body and the effective bulk density of the positive electrode active material and Al in the entire molded body decrease. Since the binder contained in the positive electrode is decomposed in the heating step S11, if no binder is added in the consolidation step S12, a molded body without a binder can be obtained. The molded body is not limited to the case where no binder is completely contained, and a small part of the binder contained in the positive electrode may remain slightly. The content (mass ratio) of the binder in the molded body is preferably 1% by mass or less, more preferably 0.5% by mass or less. By setting the content of the binder in the molded body to 1% by mass or less, factors that inhibit the thermite reaction such as gas generation caused by the binder in the melting step S13 can be suppressed. By preparing only the positive electrode in the preparation step S10, the molded body does not contain materials derived from members other than the positive electrode (such as the cell container 12, separator, negative electrode, etc.), so a molded body that is not easily broken can be obtained even without adding a binder in the consolidation step S12.

[0035] In the consolidation step S12, it is preferable to apply a load of 100 kg / cm 2 or more to the positive electrode. If the load is too small, the compression of the positive electrode will be insufficient, making it difficult to achieve the desired bulk density and making the molded body prone to collapse. By setting the load applied to the positive electrode to 100 kg / cm 2 or more, the bulk density is further improved and a more collapse-resistant molded body can be obtained. Since the contact area between the Al foil and the positive electrode active material becomes larger, the yield and purity of the metal material in the melting step S13 are further improved. The load applied to the positive electrode is more preferably 200 kg / cm 2 or more, and even more preferably 800 kg / cm 2 or more. The upper limit value of the load applied to the positive electrode is, for example, 2000 kg / cm2 It may be as follows, but is not particularly limited.

[0036] The compaction step S12 preferably forms a molded body having a bulk density of 1.7 g / cm 3 or more. If the bulk density is too low, the throughput per batch in the melting step S13 will decrease. When the bulk density is 1.7 g / cm 3 or more, the throughput per batch in the melting step S13 will surely increase. The bulk density is more preferably 2.3 g / cm 3 or more, and even more preferably 2.5 g / cm 3 or more. The upper limit value of the bulk density may be, for example, 2.5 g / cm 3 or less, but is not particularly limited.

[0037] The molded body obtained in the compaction step S12 has a carbon concentration comparable to that of the positive electrode subjected to the compaction step S12. That is, the carbon concentration in the molded body is preferably 0.7 wt%, more preferably 0.5 wt% or less, and even more preferably 0.4 wt% or less. Since the binder and conductive material contained in the positive electrode have been removed in the heating step S11, the carbon concentration in the molded body is reduced.

[0038] [Melting Step] The melting step S13 melts the molded body obtained in the compaction step S12. Regarding the melting step S13, the case where LiNi x Co y Mn z O2 is used as the positive electrode active material will be described as an example. In the melting step S13, the Al foil contained in the molded body serves as a reducing agent, and the following reaction occurs. As a result of the reaction, an alloy (Ni x Co y Mn z ) containing Ni, Co, and Mn is obtained as the metal material constituting the metal composite oxide. LiNi x Co y Mn z O2 + Al → 1 / 2Li2O + Ni x Co y Mnz +1 / 2Al2O3

[0039] Since the thermite reaction is a reaction accompanied by a large amount of heat generation, after reaching the temperature at which the reaction persists, the reaction proceeds by self-heating (reaction heat). As a method for exciting the thermite reaction, for example, there is the thermite method in which a compact is placed in a crucible and ignited. Basically, just this ignition causes the thermite reaction to proceed, and a metal material containing the metals constituting the metal composite oxide can be obtained. In the thermite method, a combustion aid can be appropriately used as necessary. Alternatively, there is also a method using a device that applies high-temperature heat from the outside, such as arc melting or a high-frequency induction melting furnace. In this case, the compact melts due to self-heating (reaction heat), and the compact also melts due to heat such as arc melting or high-frequency induction melting.

[0040] The binder contained in the positive electrode is removed in the heating step S11, and the positive electrode is compression-molded without adding the binder in the consolidation step S12. As a result, in the melting step S13, the generation of gas caused by the binder is suppressed, so that the thermite reaction proceeds favorably and safety is ensured. If the binder is added in the consolidation step, gases such as hydrogen and carbon oxides are generated due to thermal decomposition of the added binder and subsequent oxidation, which may inhibit the thermite reaction or cause the gas to expand rapidly and damage the melting furnace, which is not preferable.

[0041] [Separation step] In the separation step S14, the melt is cooled to separate a metal material containing the metals constituting the metal composite oxide and slag.

[0042] 2. Action and effect In the method for treating a non-aqueous electrolyte secondary battery according to this embodiment, a consolidation step S12 is carried out after the heating step S11. In the heating step S11, by heat-treating the positive electrode, a spontaneous oxidation-reduction reaction (thermit reaction) is promoted in the melting step S13. In the consolidation step S12, by compression-molding the heat-treated positive electrode, a molded body with an improved bulk density can be obtained. Therefore, in the melting step S13, the processing amount per batch can be increased, and the yield and purity of the metal material can be improved. By carrying out the consolidation step S12 after the heating step S11, the reduction reaction of the positive electrode can be promoted at low cost in the melting step S13.

[0043] In the molded body obtained by compression-molding the positive electrode in the consolidation step S12, the bulk density increases, and the contact area between the Al foil and the positive electrode active material increases. Therefore, in the melting step S13, the heat generation amount per unit volume during the thermit reaction increases, and the thermit reaction proceeds favorably. Since the compression-molded molded body is not easily deformed, it is easy to handle when moving or storing the molded body.

[0044] By applying a load of 100 kg / cm 2 or more to the positive electrode, the bulk density is further improved, and a more deformation-resistant molded body can be obtained. The contact area between the Al foil and the positive electrode active material further increases, the thermit reaction is promoted, and the yield and purity of the metal material are further improved.

[0045] By removing the binder contained in the positive electrode in the heating step S11 and compression-molding the positive electrode without adding a binder in the consolidation step S12, the generation of gas due to the binder is suppressed in the melting step S13. Therefore, the thermit reaction proceeds favorably, and safety is ensured.

[0046] In the heating step S11, by heating at a temperature at which the foil does not oxidize, the generation of alumina is suppressed. Therefore, the Al foil can be effectively used as a reducing agent in the melting step S13.

[0047] In the heating step S11, by heating at a temperature at which the binder is decomposed, generation of reaction-inhibiting gas at the stage of the melting step S13 is suppressed, and the thermite reaction is promoted.

[0048] In the heating step S11, by heating at 400°C or higher and 650°C or lower, generation of the thermite reaction during the heat treatment is suppressed, and safety is improved. By the heat treatment, the binder and the conductive material are removed, and generation of reaction-inhibiting gas at the stage of the melting step S13 is suppressed. For this reason, the thermite reaction in the melting step S13 is promoted.

[0049] The melting step S13 does not require a heating means for applying high-temperature heat, and self-heats by the reaction heat of the foil and the active material, and the thermite reaction proceeds, so that the cost can be further reduced.

[0050] 3. Examples Hereinafter, experiments conducted to confirm the effects of the present invention will be described.

[0051] [Example 1] to [Example 7] A used non-aqueous electrolyte secondary battery in which a wound electrode body and a non-aqueous electrolyte were housed in a cell container 12 was prepared. The configurations of the positive electrode and the non-aqueous electrolyte included in the prepared non-aqueous electrolyte secondary battery are as follows.

[0052] [Positive Electrode] Al foil thickness 15 μm, 20 mass% Active material (LiNi 1 / 6 Co 2 / 3 Mn 1 / 6 O2) 72 to 73 mass% Binder (PVDF) 3 to 4 mass% Conductive material 4 mass% [Non-aqueous Electrolyte] Non-aqueous solvent (DMC:EMC:PC) mass ratio 28:27:28 Electrolyte (LiPF6) 1M

[0053] In the experiment, first, the prepared non-aqueous electrolyte secondary battery was discharged, and the wound electrode body taken out by opening the cell container 12 was unwound to prepare the positive electrode (preparation step S10). The prepared positive electrode was cut using a shredder manufactured by Fellowes (model number: JB-315S, set cutting size: 2 mm × 2 mm) and a shredder manufactured by Iris Ohyama (model number: AFS-150C-H, set cutting size: 4 mm × 10 mm) in combination, and then heat treatment (heating step S11) was performed using a general rotary kiln, which was taken as Example 1. The heating temperature in the heat treatment was 500°C, and the keep time was 30 minutes.

[0054] The carbon concentration of Example 1 was measured. The carbon concentration was measured using a carbon and sulfur analyzer (model number: CS744, detection method: non-dispersive infrared absorption method) manufactured by LECO Japan Co., Ltd.

[0055] The carbon concentration in the positive electrode was 6.5 wt% before the heat treatment and decreased to 0.4 wt% after the heat treatment. It was confirmed that the carbon derived from the binder and the conductive material was removed by the heat treatment.

[0056] Next, the experiment conducted to confirm the effect of the consolidation step S12 will be described.

[0057] Through the same preparation step S10 and heating step S11 as in Example 1, a heat-treated positive electrode was prepared. The size of the heat-treated positive electrode was 4 mm × 10 mm for the large ones and 1 mm or less and powdery for the small ones. The bulk density of the heat-treated positive electrode was 0.1 - 0.2 g / cm 3 It was. The bulk density was calculated by dividing the mass of the positive electrode when gently filling the positive electrode into the graduated cylinder by the volume including the voids in the container (including the voids between the positive electrodes). The heat-treated positive electrode was subjected to the consolidation step S12, and the positive electrode was compression-molded using a general compression device without adding a binder. In the consolidation step S12, the load applied to the positive electrode was 100 kg / cm 2 200 kg / cm 2 300 kg / cm 2 800 kg / cm 2, 1000 kg / cm 2 , 2000 kg / cm 2 were changed to produce six types of compacts, which were designated as Examples 2, 3, 4, 5, 6, and 7. The bulk density of Examples 2 to 7 was calculated by dividing the mass of the compact by the volume.

[0058] Figure 3 is a graph showing the relationship between the load and the bulk density during the compression molding of the positive electrode. It was confirmed that the bulk density increased as the load increased. When the load was 100 kg / cm 2 or more, the bulk density became 1.7 g / cm 3 or more.

[0059] Next, Example 5 with a load of 800 kg / cm 2 during compression molding and Example 7 with a load of 2000 kg / cm 2 during compression molding were subjected to the melting step S13 to evaluate the thermite reaction. The compacts of Examples 5 and 7 were placed in separate crucibles and ignited without using a combustion aid. The melt obtained in the melting step S13 was taken out of the crucible, and it was visually observed whether the compact had melted, and the thermite reaction was evaluated according to the following criteria. "◎" and "〇" indicate passing, and "×" indicates failing.

[0060] "◎": The positive electrode melted, a metal material was obtained, and the thermite reaction occurred. "〇": A part of the positive electrode melted, a metal material was obtained, and the thermite reaction occurred. "×": A metal material was not obtained, and the thermite reaction did not occur.

[0061] It was confirmed that in both Examples 5 and 7, the compact melted, a metal material was obtained, the thermite reaction was good, and the evaluation result was "◎".

[0062] Also, when comparing the thermite reaction between Example 6 with a load of 1000 kg / cm 2 during compression molding and Example 1 with the same mass, it was confirmed that Example 6 in which the densification step S12 was performed emitted stronger light and heat than Example 1 in which the densification step S12 was not performed. From this result, the effect of promoting the thermite reaction by the densification step S12 was confirmed.

[0063] By compression-molding the heat-treated positive electrode without adding a binder, the carbon concentration was 0.4 wt%, which was equivalent to that of the positive electrode before compression-molding. As the bulk density increased, the heat generation per unit volume during the thermite reaction increased, and it is considered that the thermite reaction was promoted.

[0064] The present invention is not limited to the above embodiments, and can be appropriately modified within the scope of the gist of the present invention.

[0065] The method for manufacturing a molded body includes a heating step of performing a heat treatment for heating a positive electrode having a foil containing Al and an active material as a metal composite oxide, and a consolidation step of compression-molding the positive electrode subjected to the heat treatment to form a molded body. It is preferable to have a preparation step of preparing a positive electrode before the heating step.

Explanation of reference numerals

[0066] 10 Non-aqueous electrolyte secondary battery S10 Preparation step S11 Heating step S12 Consolidation step S13 Melting step S14 Separation step

Claims

1. A method for treating a positive electrode of a non-aqueous electrolyte secondary battery, the positive electrode having a foil containing Al and an active material as a metal composite oxide, the method comprising: a preparation step of preparing the positive electrode; a heating step of performing a heat treatment for heating the positive electrode; a consolidation step of compression molding the positive electrode that has undergone the heat treatment to form a molded body; a melting step of melting the molded body by the heat of reaction between the foil and the active material to obtain a melt; a separation step of separating the melt into a metal material containing a metal constituting the metal composite oxide and slag A method for treating a positive electrode of a non-aqueous electrolyte secondary battery having the above steps.

2. The method for treating a positive electrode of a non-aqueous electrolyte secondary battery according to claim 1, wherein the consolidation step compression-molds the positive electrode without adding a binder.

3. The positive electrode subjected to the heating step contains a binder, The method for treating a positive electrode of a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the heat treatment is performed at a temperature at which the binder is decomposed.

4. The method for treating a positive electrode of a non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the positive electrode is any one of process scraps generated in a positive electrode manufacturing process, unused positive electrodes of non-aqueous electrolyte secondary batteries, and used positive electrodes of non-aqueous electrolyte secondary batteries.

5. A molded body having a configuration in which a positive electrode of a non-aqueous electrolyte secondary battery having a foil containing Al and an active material as a metal composite oxide is compression-molded, and having a binder content of 1% by mass or less.

6. The molded body according to claim 5, wherein the carbon concentration is 0.7 wt% or less.

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