Method for manufacturing electrode, method for manufacturing lithium ion battery, and lithium ion battery

Abstract

In the present invention, a plurality of metal salts containing Li and a ternary material are prepared (S1), a blending ratio of the metal salts is adjusted (S2), black mass and the metal salts are mixed (S3), and then heat treatment is performed to synthesize a positive electrode active material (S4). Next, the positive electrode active material, a conductive auxiliary agent, and a binder are charged into a vibration stirring device for vibration stirring to obtain a powder mixture (S5). Thereafter, sheet forming is performed on a positive electrode current collector by using a forming method such as a hot press method (S6), and a positive electrode composed of a dry electrode is obtained. Instead of black mass, a used waste positive electrode material and a waste electrode active material layer can be used. As a result, resources are effectively utilized by reusing used lithium ion batteries, and a practical electrode and lithium ion battery having desired good battery characteristics are obtained at low cost.

Description

Method for manufacturing electrodes, method for manufacturing lithium-ion batteries, and lithium-ion batteries

[0001] The present invention relates to a method for manufacturing electrodes, a method for manufacturing lithium-ion batteries, and lithium-ion batteries, and more specifically, to a method for manufacturing electrodes using recycled used lithium-ion batteries, a method for manufacturing lithium-ion batteries produced using this method, and a lithium-ion battery formed using electrodes obtained by this method.

[0002] With the expansion of the market for portable electronic devices such as mobile phones, laptops, and tablet devices, the development of rechargeable batteries as cordless power sources for these devices is thriving. Furthermore, against the backdrop of global warming and the depletion of petroleum resources, the development of electric vehicles and hybrid vehicles powered by rechargeable batteries is also progressing rapidly.

[0003] Under these circumstances, secondary batteries are being developed that utilize alkali metal ions such as lithium ions as charge carriers and employ electrochemical reactions associated with charge transfer. In particular, lithium-ion batteries, which have a high energy density, are now widely used.

[0004] Among the components of a lithium-ion battery, the electrode active material is a substance that directly contributes to the battery electrode reactions, namely the charging and discharging reactions. Since charging and discharging are carried out by utilizing the insertion and removal reactions of lithium ions into and out of the electrode active material, it plays a central role in the lithium-ion battery.

[0005] In this type of lithium-ion battery, in the early stages of development, for example, LiCoO was used as the positive electrode active material. ２ Lithium cobalt oxide was previously used, but due to the high cost of Co and the demand for higher capacity and lower costs associated with the expansion of battery applications such as those in automobiles, ternary materials in which some of the Co is replaced with Ni or Mn have attracted attention in recent years, and lithium-ion batteries using these ternary materials as cathode active materials are being actively researched and developed.

[0006] However, while demand for lithium-ion batteries is expected to increase further in the future, Li and the ternary materials mentioned above—Co, Ni, and Mn—are all rare metals, and there is a risk that securing a supply of raw materials may become difficult in the future.

[0007] Therefore, in recent years, technologies have been proposed to recover lithium-ion battery materials from a black powder called "black mass," which is produced by processing used lithium-ion batteries, and to recycle them. For example, Patent Document 1 discloses a method for extracting metals from the aforementioned black mass.

[0008] Specifically, in Patent Document 1, the non-metallic material fraction is separated from the black mass to recover the black mass containing the anode material and cathode material. Next, a gas containing sulfur dioxide and molecular oxygen is added as an extractant to a sulfuric acid-containing solution to perform acid leaching, dissolving the cathode material in the black mass and recovering the leached solution containing the cathode material. The initial fraction of metallic material is then separated from the leached solution to recover the main fraction containing at least one of Mn, Co, Ni, and Li.

[0009] Thus, in Patent Document 1, after removing non-metallic components from black mass in a pretreatment, sulfuric acid and an extractant are used to sequentially separate and recover the initial fraction of metallic material from each leaching solution containing cathode material, thereby attempting to reuse the resource.

[0010] Furthermore, a technology has been proposed that involves extracting only the electrode material from used lithium-ion batteries and reusing this electrode material to obtain regenerated lithium-ion batteries.

[0011] For example, Patent Document 2 proposes a method for producing a recycled cathode material precursor comprising a metal element α consisting of at least one of Ni, Co, and Mn, and a metal element β consisting of at least one of Fe, Cu, and Al, the method comprising a heat treatment step of heating a lithium-ion secondary battery, which is the object to be treated, to obtain a heat-treated product; a crushing step of crushing the heat-treated product to obtain crushed material; and a physical sorting step of performing physical sorting on the crushed material to obtain a physically treated product, in which the metal element α is concentrated in the physically treated product, wherein the content of the metal element β in the recycled cathode material precursor is 0.5 to 20% by mass.

[0012] In this Patent Document 2, a recycled cathode material precursor manufactured as described above is mixed with a predetermined amount of Li source to obtain a mixed powder, which is then calcined to produce a recycled cathode material, and a recycled lithium-ion battery is obtained using this recycled cathode material.

[0013] In other words, Patent Document 2 describes a method in which used lithium-ion batteries are heat-treated along with their cells to electrically and chemically detoxify the laminate that forms the battery body within each cell. The positive electrode active material is then mechanically and magnetically recovered from this laminate through processes such as crushing and physical sorting (classification and magnetic separation), thereby extracting the positive electrode active material from the laminate and using this positive electrode active material to obtain a regenerated lithium-ion battery.

[0014] On the other hand, the manufacturing of electrodes in lithium-ion batteries has traditionally been widely carried out using wet processes.

[0015] In other words, conventional electrode manufacturing processes involve mixing electrode active material with additives such as conductive enhancers and binders in a solvent such as an organic solvent or water, stirring to create a high-viscosity slurry solution, coating this slurry solution onto a foil-shaped electrode current collector, and then drying it to form an electrode active material layer, thereby manufacturing the electrode.

[0016] However, in this conventional electrode manufacturing process, unwanted solvents are removed by evaporation using hot air drying or the like during the drying process, which requires large-scale drying equipment and solvent recovery equipment, resulting in high energy consumption, high equipment and manufacturing costs, and also the emission of large amounts of CO2. ２ It had various problems, such as emitting waste.

[0017] Therefore, in recent years, dry processes that fabricate electrodes without using solvents such as organic solvents or water have been attracting attention.

[0018] For example, Patent Document 3 proposes a method for manufacturing an electrode for a lithium-ion battery, which includes a binder coating step of applying a binder to at least one surface of a metal foil to obtain a binder-equipped current collector; a compaction step of forming an electrode active material layer on the binder-equipped current collector by a dry method of compacting a powder containing electrode active material to obtain a current collector with an electrode active material layer; a conveying step of conveying the current collector with the electrode active material layer to a heating device with a tension of 5 to 50 N / m in the width direction; and a heating step of heating the ends of the current collector with the electrode active material layer in the width direction to 25 to 150°C.

[0019] In this Patent Document 3, a binder is applied to both main surfaces of a current collector, powder (composite particles containing electrode active material) is supplied to the binder-coated current collector, the ends are heated and a predetermined tension is applied while conveying, and the powder is compressed and molded on both main surfaces of the binder-coated current collector by being sandwiched between a pair of rolls, thereby attempting to produce electrodes without using solvents such as organic solvents or water.

[0020] Japanese Patent Publication No. 2024-516955 (Claim 1, paragraphs

[0063] to

[0066] , Figures 2a, 2b, etc.), Japanese Unexamined Patent Publication No. 2023-4914 (Claim 12, paragraphs

[0041] to

[0043] ,

[0059] to

[0094] , Figure 1, etc.), Japanese Unexamined Patent Publication No. 2015-185403 (Claim 1, paragraphs

[0013] to

[0016] ,

[0036] to

[0039] , Figure 1, etc.)

[0021] However, the aforementioned Patent Document 1 involves a complicated processing step for extracting, separating, and recycling battery materials from black mass, and the equipment required is expensive, resulting in high recycling costs and poor practicality.

[0022] Furthermore, while Patent Document 2 describes a method for regenerating a cathode material precursor from used lithium-ion batteries and obtaining a lithium-ion battery using the regenerated cathode material precursor, the process involves heat-treating the entire used lithium-ion battery cell in the preceding step, followed by classification and magnetic separation steps to obtain the regenerated cathode material precursor. Similar to Patent Document 1, this method is complicated and results in high recycling costs.

[0023] On the other hand, while Patent Document 3 attempts to manufacture electrodes without using solvents such as organic solvents or water in the electrode manufacturing process, the preceding binder coating process involves coating the current collector with a binder-forming slurry. Therefore, a drying device is required to evaporate and remove the solvent in the slurry, limiting cost reduction. Furthermore, Patent Document 3 only describes a method for manufacturing a negative electrode using graphite as the negative electrode active material in the examples, and does not take the perspective of constructing a lithium-ion battery by reusing used lithium-ion batteries.

[0024] Under these circumstances, there is a growing demand for lithium-ion batteries that can efficiently produce high-performance electrodes at low cost while effectively utilizing resources such as rare metals.

[0025] This invention has been made in view of these circumstances, and aims to provide a method for manufacturing electrodes that can effectively utilize resources by reusing used lithium-ion batteries and produce practical electrodes with desirable good battery characteristics at a lower cost, a method for manufacturing lithium-ion batteries using this method, and a lithium-ion battery that can achieve good battery characteristics by using this electrode manufacturing method.

[0026] The black mass described above is a black powder obtained by discharging and deactivating used lithium-ion batteries, heating and drying them to evaporate the electrolyte, then crushing and pulverizing them, extracting and removing unwanted impurity elements, and sieving them.

[0027] Therefore, in the case of spent lithium-ion batteries using ternary materials (Ni, Mn, Co) as electrode active materials, since black mass contains ternary materials and Li, it is possible to synthesize electrode active materials at low cost without requiring processing steps such as acid leaching or extraction as described in Patent Document 1 by mixing these ternary materials and Li-containing metal salts with black mass, performing heat treatment, and reacting the metal salts with the black mass. This allows for the effective recycling of resources and promotes the efficient use of Earth's resources.

[0028] Furthermore, by disassembling used lithium-ion batteries to extract only the electrode material (e.g., positive electrode material), crushing this electrode material, i.e., waste electrode material, into a black powder, and reusing this powder, resources can be effectively recycled, promoting the efficient use of Earth's resources. In particular, since the waste electrode material can be virtually free from impurities originating from the electrolyte material and counter electrode (e.g., negative electrode), stable and good battery characteristics can be obtained even with a reduced amount of metal salts added to Li and ternary materials, enabling even more efficient use of resources and contributing to further improvements in recycling effectiveness.

[0029] Furthermore, it is believed that even if only the used electrode active material layer (waste electrode active material layer) is separated and extracted from the above-mentioned waste electrode material, and this is then powdered and reused, it is possible to obtain battery characteristics and recycling effects that are approximately equivalent to or better than those of the waste electrode material.

[0030] On the other hand, as mentioned in the [Background Technology] section, electrodes have conventionally been widely manufactured using wet processes with solvents such as organic solvents and water. However, considering energy consumption, cost, and environmental impact, it is preferable to devise a method for manufacturing electrodes without using solvents.

[0031] Therefore, from this perspective, the inventors used black mass, waste electrode material, and waste electrode active material layer as recycled materials, added a Li-containing ternary metal salt to these recycled materials to produce an active material, and manufactured electrodes by a dry process without using pure water or organic solvents, including the addition of conductive additives and binders and the molding process on metal foil (current collector), and evaluated their characteristics. As a result, they found that it is possible to manufacture electrodes with battery characteristics that are approximately equivalent to or better than those of electrodes manufactured by a wet process.

[0032] The present invention is based on such findings, and the method for manufacturing electrodes according to the present invention is a method for manufacturing electrodes that reuse used lithium-ion batteries, wherein the waste electrode material obtained by disassembling the used lithium-ion battery has a waste electrode active material layer and a waste electrode current collector bonded to the electrode active material layer, and the method includes the steps of preparing black mass obtained by processing the entire used lithium-ion battery, the waste electrode material, and the waste electrode active material layer, and preparing a plurality of metal salts containing Ni, Mn, Co, and Li components. The present invention is characterized by comprising the steps of: preparing the blending ratio of these metal salts; using one of the black mass, the powdered waste electrode material, and the powdered waste electrode active material layer as a recycled material, mixing the recycled material with the plurality of metal salts, and subjecting it to heat treatment to synthesize a first active material; mixing an additive containing at least a conductive additive and a binder with the first active material, subjecting it to a dry dispersion treatment to obtain a first mixture; and dry forming the first mixture into a sheet on at least one main surface of a first metal foil to produce a first dry electrode.

[0033] This allows for the production of electrodes, the final product, using used lithium-ion batteries as a starting material and without the use of solvents such as organic solvents or water, through a dry process. This enables the effective utilization of rare metal resources such as Li and ternary materials, while reducing energy consumption. As a result, electrodes with good battery characteristics, high practicality, and reduced environmental impact can be produced efficiently and at low cost.

[0034] Here, the term "dry electrode" refers to an electrode manufactured through a dry process without the use of solvents such as organic solvents or pure water.

[0035] Furthermore, the aforementioned "powdered waste electrode active material layer" includes powdered material mainly composed of metal powders separated from the waste electrode active material layer by centrifugal separation or the like.

[0036] Furthermore, the method for manufacturing an electrode of the present invention preferably includes the steps of: mixing an additive containing at least a conductive aid and a binder with a second active material, and subjecting it to a dry dispersion treatment to obtain a second mixture; and dry forming the second mixture into a sheet on at least one main surface of a second metal foil to produce a second dry electrode that will serve as a counter electrode to the first dry electrode.

[0037] This allows both the positive and negative electrodes to be manufactured using a dry process, enabling further cost reductions and energy consumption savings.

[0038] Furthermore, in the electrode manufacturing method of the present invention, it is preferable that the binder contains one or more selected from the group belonging to the category of thermoplastic materials, and the conductive additive contains at least one selected from the group consisting of conductive carbon, carbon fiber, carbon nanotube, graphene, and conductive polymer.

[0039] By using such binders and conductive additives, electrodes can be easily manufactured in a dry process without the use of solvents such as organic solvents or water.

[0040] Furthermore, in the electrode manufacturing method of the present invention, from the viewpoint of ensuring good adhesion of the metal foil and good battery characteristics, the mixing ratio of the conductive additive and the binder is preferably 1 / 5 to 5 / 1 in terms of weight ratio.

[0041] Similarly, from the viewpoint of ensuring good adhesion of the metal foil and good battery characteristics, the mixing ratio of the additive to the first active material or the second active material is preferably 1 / 20 to 1 / 3 by weight.

[0042] Furthermore, in the electrode manufacturing method of the present invention, the second active material can preferably be one selected from the group consisting of carbon-based materials, lithium metals, and oxide-based materials including lithium titanate.

[0043] Furthermore, in the electrode manufacturing method of the present invention, the dispersion treatment can preferably be any method selected from the group consisting of vibration stirring, ball milling, kneading, and dry mixing.

[0044] By selecting and using the most suitable dispersion method as needed, it becomes possible to uniformly disperse the mixture.

[0045] Furthermore, in the electrode manufacturing method of the present invention, the sheet molding can preferably be performed using any molding method selected from the group consisting of the hot press method, polymer fiberization method, dry spray deposition method, calendering method, melt extrusion method, 3D printing method, vapor deposition method, and electrostatic coating method.

[0046] This allows for the formation of desired sheets using a dry process by considering the type of binder and selecting the most suitable molding method as needed.

[0047] Furthermore, in the electrode manufacturing method of the present invention, it is preferable that the content of the plurality of metal salts is 35 to 5000 parts by weight in total per 100 parts by weight of recycled material.

[0048] By freely selecting the total amount of metal salts mixed with black mass within a wide range of 35 to 5000 parts by weight per 100 parts by weight of black mass, it is possible to adequately address the varying conditions of used lithium-ion batteries and the significant individual differences in the component composition of black mass depending on the processing conditions and production units during the manufacturing process. This makes it possible to produce electrode active materials with good battery characteristics while promoting the effective recycling of resources.

[0049] Furthermore, in the electrode manufacturing method of the present invention, the content of the plurality of metal salts is more preferably 35 to 1400 parts by weight in total with respect to 100 parts by weight of the recycled material.

[0050] In particular, when recycled waste electrode material or waste electrode active material layer is used, unlike black mass, these waste electrode material and waste electrode active material layer do not contain impurities that do not contribute to battery characteristics originating from the electrolyte or counter electrode. Therefore, by incorporating metal salts within the above-mentioned range, it is possible to manufacture electrodes with excellent battery characteristics that are highly practical.

[0051] Furthermore, in the electrode manufacturing method of the present invention, when the waste electrode active material layer is used as the recycled material, it is preferable to impregnate the waste electrode material in a solvent and heat it to separate the waste electrode active material layer from the waste electrode current collector, and use the waste electrode active material layer as the recycled material.

[0052] In this case, since the waste electrode material is impregnated in a solvent and heated to separate the waste electrode active material layer from the waste electrode current collector, it is possible to effectively suppress the separation of metal components in the waste electrode active material layer from the waste electrode active material layer without causing mechanical damage.

[0053] Furthermore, in the electrode manufacturing method of the present invention, it is preferable to dissolve each metal powder containing each component that forms the metal salt in a solvent to prepare a mixed solution, then process the mixed solution to produce a precipitate, obtain the metal salt from the precipitate, and mix the recycled material with the metal salt.

[0054] This makes it possible to obtain highly refined, high-quality metal salts, and thus produce high-quality electrode active materials.

[0055] Furthermore, in the method for manufacturing electrodes of the present invention, it is preferable to perform the heat treatment at a temperature of 650 to 1100°C for 0.5 to 12 hours.

[0056] By appropriately adjusting the heat treatment temperature and time in this manner, electrode active materials with desired battery performance can be easily fabricated.

[0057] Furthermore, in the electrode manufacturing method of the present invention, when the plurality of metal salts are synthesized by mixing these plurality of metal salts, the composition formula LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ (Hereinafter referred to as "NMC111") General formula LiNiｘ Mn ｙ Co ｚ O ２ (where x > 0, y > 0, z > 0, x + y + z = 1), or the general formula Li(Li ｐ Ni ｑ Mn ｒ Co ｓ )O ２ (where p > 0, q > 0, r > 0, s > 0, p + q + r + s = 1), it is preferable to prepare the blending ratio so that a metal oxide represented by the formula can be formed and mix it with the recycled material.

[0058] [[ID=二十]] The method for manufacturing a lithium ion battery according to the present invention is a method for manufacturing a lithium ion battery having a positive electrode, a negative electrode, and an electrolyte, and is manufactured by recycling a used lithium ion battery. It is characterized by manufacturing using the electrode manufactured by the manufacturing method described above.

[0059] Thus, a lithium ion battery having an electrode manufactured by a dry process using a used lithium ion battery as a starting material can be manufactured.

[0060] The lithium ion battery according to the present invention is a lithium ion battery having a positive electrode, a negative electrode, and an electrolyte, and is formed by recycling a used lithium ion battery. The first active material material is any one of the black mass obtained by treating the entire used lithium ion battery, the waste electrode material obtained by decomposing the used lithium ion battery, and the waste electrode active material layer obtained by separating the waste electrode current collector from the waste electrode material. It contains and is mainly composed of a metal oxide containing Ni, Mn, Co, and Li. The positive electrode is formed of a first dry electrode including a first metal foil and a thin film mainly composed of the first active material material formed on at least one main surface of the first metal foil.

[0061] Since the first dry electrode is manufactured by a dry process in this way, it is possible to avoid the generation of pores due to the evaporation and removal of the solvent like in the wet process on the electrode surface and inside the electrode. The electrode density and the mechanical strength of the electrode are improved, and a lithium ion battery having good battery characteristics at a lower cost can be obtained.

[0062] Furthermore, in the lithium-ion battery of the present invention, it is preferable that the negative electrode is formed of a second dry electrode comprising a second metal foil and a thin film mainly composed of a second active material formed on at least one main surface of the second metal foil.

[0063] As a result, both the positive and negative electrodes are formed through a dry process, which further improves electrode density and the mechanical strength of the electrodes, making it possible to obtain lithium-ion batteries with better battery characteristics at a lower cost.

[0064] Furthermore, the lithium-ion battery of the present invention may include one selected from the group consisting of carbon-based materials, lithium metal, and oxide-based materials including lithium titanate as the second active material.

[0065] According to the electrode manufacturing method, lithium-ion battery manufacturing method, and lithium-ion battery of the present invention, black mass, waste electrode material, or waste electrode active material layer obtained from used lithium-ion batteries are used as recycled materials, and electrodes and the final product, the lithium-ion battery, are obtained by a dry process. Therefore, remarkable effects that could not be obtained with conventional methods can be achieved as follows.

[0066] (1) This method does not require the laborious process of recovering and purifying metal salts from black mass as in Patent Document 1, nor does it require classification and separation processes or magnetic separation processes as in Patent Document 2. This method allows for the effective utilization of resources contained within used lithium-ion batteries and reduces the use of expensive rare metals such as Li and ternary materials (Ni, Mn, Co).

[0067] Furthermore, because the electrodes are fabricated using a dry process, various effects can be achieved as described below.

[0068] (2) Since the slurry preparation process for binder coating, as described in Patent Document 3, is unnecessary and no solvents such as organic solvents or pure water are used, large-scale drying equipment and solvent recovery equipment for recovering solvents are unnecessary, resulting in significant cost reductions.

[0069] (3) No electricity is required to operate the drying equipment, etc., and energy consumption can be reduced significantly.

[0070] (4) Since large-scale drying treatment is not required, CO ２ Emissions can be suppressed.

[0071] (5) As mentioned above, since no solvent is required for slurry preparation, material costs can be reduced.

[0072] (6) Organic solvents that have a significant environmental impact and are harmful to the human body are widely used as solvents for slurry preparation, but such organic solvents are unnecessary in dry processes, thus reducing the environmental impact.

[0073] (7) In the wet process, residual solvents that do not evaporate, or additives contained in the solvent, may remain in the electrodes as residues, and such residues may affect the battery characteristics. However, in the dry process, no solvent is used in the electrode manufacturing process, so no such residues remain in the electrodes, making it possible to obtain better battery characteristics.

[0074] (8) In the wet process, pores are formed inside the electrode after drying, which may affect the ion conduction of Li ions. However, in the dry process, such pores are not formed, the electrode density can be improved, and furthermore, the mechanical strength of the electrode can be improved.

[0075] Thus, by combining the effective utilization of used lithium-ion batteries with a dry process in the electrode manufacturing process, the present invention makes it possible to obtain a lithium-ion battery that has unprecedented advantages, such as significantly reducing energy consumption and costs while maintaining battery characteristics, and being environmentally friendly.

[0076] This is a schematic cross-sectional view showing one embodiment of the lithium-ion battery according to the present invention. This is an enlarged cross-sectional view of part A in Figure 1. This is a manufacturing process diagram showing a first embodiment of the method for manufacturing a positive electrode as an electrode according to the present invention. This is a manufacturing process diagram showing one embodiment of the method for manufacturing a negative electrode as an electrode according to the present invention. This is a manufacturing process diagram showing a second embodiment of the method for manufacturing a positive electrode as an electrode according to the present invention. This is a schematic cross-sectional perspective view showing the state of removing waste positive electrode material from a used lithium-ion battery. This is a manufacturing process diagram showing a third embodiment of the method for manufacturing a positive electrode as an electrode according to the present invention.

[0077] Next, embodiments of the present invention will be described in detail with reference to the drawings.

[0078] Figure 1 is a schematic cross-sectional view showing a lithium-ion battery (cylindrical type) according to the present invention, and Figure 2 is an enlarged cross-sectional view of part A in Figure 1.

[0079] As shown in Figure 1, this lithium-ion battery has a convex positive electrode terminal 1 made of Al or the like, and a bottomed cylindrical negative electrode case 2 made of Cu or the like that also serves as the negative electrode terminal. Multiple sets of battery body parts 6, each consisting of a positive electrode 3, a separator 4, and a negative electrode 5, are stacked and housed in the negative electrode case 2. The positive electrode 3 is electrically connected to the positive electrode terminal 1 via a positive electrode support member 7, and the negative electrode 5 is electrically connected to the negative electrode terminal (negative electrode case 2). The positive electrode terminal 1 and the negative electrode case 2 are electrically insulated by insulating plates 8, 9 and a gasket 10.

[0080] As shown in Figure 2, the positive electrode 3 has positive electrode active material layers 13a and 13b formed on both main surfaces of a positive electrode current collector (first metal foil) 12 made of Al foil or the like. The negative electrode 5 has negative electrode active material layers 15a and 15b, mainly composed of carbon-based materials or lithium metal, formed on both main surfaces of a negative electrode current collector (second metal foil) 14 made of Cu foil or the like. The separator 4 is made of a porous sheet or film such as a microporous membrane, woven fabric, or nonwoven fabric, and is interposed between the positive electrode 3 and the negative electrode 5. The internal space of these battery body parts 6 is filled with electrolyte 11.

[0081] Furthermore, this lithium-ion battery is formed by reusing used lithium-ion batteries.

[0082] The following describes the method for manufacturing electrodes and lithium-ion batteries according to the present invention.

[0083] (First Embodiment) In the first embodiment, the positive electrode active material that forms the main component of the positive electrode active material layers 13a and 13b contains black mass obtained by processing the entire used lithium-ion battery, and is formed mainly of a ternary metal oxide such as NMC111. The positive electrode 3 is formed from a first dry electrode manufactured through a dry process, and the positive electrode active material layers 13a and 13b (thin films) mainly composed of the positive electrode active material are formed on both main surfaces of the positive electrode current collector 12.

[0084] Furthermore, in this first embodiment, the negative electrode 5 is also formed from a dry electrode (first dry electrode) manufactured through a dry process, and negative electrode active material layers 15a and 15b (thin films) mainly composed of the negative electrode active material are formed on both main surfaces of the negative electrode current collector 14.

[0085] In this first embodiment, black mass is used as a recycled material, and the positive electrode 3 (first dry electrode) and negative electrode 5 (second dry electrode) are manufactured using a dry process. The manufacturing methods for the positive electrode 3 and negative electrode 5 will be described in detail below.

[0086] <Fabrication of the positive electrode> Figure 3 is a manufacturing process diagram showing a first embodiment of the method for manufacturing a positive electrode as an electrode according to the present invention.

[0087] First, prepare the black mass. As described in the section on [Means for Solving the Problem], this black mass is a powder obtained by discharging and deactivating used lithium-ion batteries, heating and drying them to evaporate the electrolyte, then crushing and pulverizing them, extracting and removing unwanted impurity elements, and sieving them.

[0088] Then, in step S1, several metal salts containing Li, Ni, Mn, and Co are prepared. Here, the metal salts are not particularly limited, and various metal salts such as acetate compounds, nitrate compounds, carbonate compounds, and chlorides can be used.

[0089] Next, in step S2, the mixing ratio of these metal salts is prepared. Specifically, first, each metal salt is weighed out such that, for example, Li, Ni, Mn, and Co are in molar ratios of Li:Ni, Mn, Co = 1:1 / 3:1 / 3:1 / 3, and these weighed materials are dissolved in a large amount of solvent such as pure water to prepare a mixed solution.

[0090] On the other hand, a precipitating agent solution is prepared by dissolving a precipitating agent such as citric acid in a large amount of solvent such as pure water.

[0091] Then, the mixed solution and the precipitating agent solution are mixed to produce a precipitate, the precipitate is filtered to remove the supernatant, the obtained precipitate is thoroughly washed and dried to obtain a metal salt with the adjusted blending ratio.

[0092] This allows for the production of highly refined, high-quality metal salts, enabling the manufacture of high-quality cathodes.

[0093] Next, in step S3, the black mass and the plurality of metal salts are mixed to obtain a mixture.

[0094] Here, the mixing ratio of metal salts to black mass is not particularly limited, but it is preferable to mix them so that the total content of metal salts is 35 to 5000 parts by weight per 100 parts by weight of black mass.

[0095] In other words, as described above, black mass is obtained by processing used lithium-ion batteries (hereinafter referred to as "processed material"), but the component composition of this processed material varies depending on the processed material, and in reality, the component composition of black mass also varies greatly depending on the processing conditions in the black mass manufacturing process and the production unit. That is, some individual black masses have a high content of Li and the ternary materials mentioned above, while others have a low content. Therefore, in order to effectively utilize black mass to promote resource recycling and obtain electrode active materials with practical value, it is desirable to set the content of metal salts over a wide range so as to be able to deal with the component composition of each individual black mass.

[0096] However, if the total content of metal salts is less than 35 parts by weight per 100 parts by weight of black mass, even if a considerable amount of ternary materials and Li components are present in the black mass, the total content of metal salts is insufficient. As a result, it may not be possible to secure a sufficient capacity density compared to lithium-ion batteries manufactured by conventional methods, and it may become impossible to obtain a lithium-ion battery with the desired battery capacity. On the other hand, if the total content of metal salts exceeds 5,000 parts by weight per 100 parts by weight of black mass, the large total content of metal salts allows for good battery characteristics even with small amounts of ternary materials and Li components in the black mass. However, this may not meet the requirement of recycling and utilizing effective resources.

[0097] Therefore, from the viewpoint of ensuring practical battery characteristics while promoting the effective reuse of resources, the total content of metal salts is preferably 35 to 5000 parts by weight per 100 parts by weight of black mass.

[0098] In the following step S4, the mixture obtained in step S3 is subjected to heat treatment at a predetermined heat treatment temperature for a predetermined time, and then allowed to cool naturally until it reaches room temperature, thereby synthesizing the positive electrode active material (first active material).

[0099] Here, the heat treatment temperature is not particularly limited, but it is generally preferable to carry it out in the range of 650°C to 1100°C. At low temperatures below 650°C, sufficient crystallization may not occur, making it difficult to obtain the desired capacity density. On the other hand, at high temperatures above 1100°C, crystallization may proceed excessively, inhibiting the movement of Li ions and potentially leading to a deterioration of the cycle characteristics.

[0100] Furthermore, while there are no particular limitations on the heat treatment time, it is preferable to perform it for approximately 0.5 to 12 hours. If the heat treatment time is less than 0.5 hours, sufficient crystallization may not occur, and it may become difficult to obtain the desired capacity density. On the other hand, if the heat treatment time exceeds 12 hours, crystallization may proceed excessively, inhibiting the movement of Li ions and potentially leading to a deterioration of the cycle characteristics.

[0101] Next, the process proceeds to step S5, where a vibrating agitator such as a vortex mixer is prepared. The positive electrode active material and additives containing a conductive additive and a binder are then placed into the vibrating agitator and subjected to a vibrating agitator treatment, thereby uniformly or substantially uniformly dispersing the additives in the positive electrode active material to obtain a powder mixture (the first mixture).

[0102] Here, the mixing ratio of the conductive additive and the binder (conductive additive / binder) is not particularly limited, but a ratio of 1 / 5 to 5 / 1 by weight is preferred. If the mixing ratio is less than 1 / 5, the binder content will be excessive, leading to increased insulation and resistance, which may result in a decrease in battery characteristics. On the other hand, if the mixing ratio exceeds 5 / 1, the binder content will be insufficient, which may lead to a decrease in adhesion between the positive electrode active material and the positive electrode current collector.

[0103] Furthermore, the mixing ratio of the total amount of conductive additive and binder to the positive electrode active material ((conductive additive + binder) / positive electrode active material) is not particularly limited, but is preferably 1 / 20 to 1 / 3 in terms of weight ratio. If the mixing ratio is less than 1 / 20, the total amount of conductive additive and binder will be insufficient. If the amount of conductive additive decreases, it may lead to a decrease in conductivity and a deterioration of battery characteristics, and if the amount of binder decreases, it may lead to a decrease in adhesion between the positive electrode active material and the positive electrode current collector. On the other hand, if the mixing ratio exceeds 1 / 3, the total amount of conductive additive and binder increases, resulting in an insufficient amount of positive electrode active material, which may lead to a deterioration of battery characteristics.

[0104] Here, the conductive additive is not particularly limited and can be, for example, conductive carbon such as graphite, carbon black, and acetylene black, carbon-based fibers such as carbon nanohorns, carbon nanotubes, graphene, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. Furthermore, two or more types of conductive additives can be mixed and used.

[0105] Furthermore, while the binder is not particularly limited, one or more types selected from the group belonging to the category of various thermoplastic materials such as polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyethylene (PE), polypropylene (PP), polyethylene oxide (PEO), polylactic acid (PLA), carboxymethylcellulose (CMC), styrene-butadiene copolymer (SBR), and acrylonitrile-butadiene-styrene copolymer (ABS) can be preferred.

[0106] Next, in step S6, the powder mixture obtained in step S5 is dry-formed into a sheet on both main surfaces of the positive electrode current collector 12, for example using a hot press method, thereby producing the positive electrode 3, which is a dry electrode.

[0107] That is, for example, a well-known uniaxial press type hot press machine having an upper die and a lower die is prepared. The powder mixture obtained in step 5 is placed on both main surfaces of the foil-shaped positive electrode current collector 12, such as Al foil, and the powder mixture and the positive electrode current collector 12 are set in the lower die. The upper die is driven toward the lower die while heating to about 150 to 200°C by induction heating or the like, and the powder mixture is pressurized at a pressure of about 8 to 12 MPa for about 1 hour to produce a pressed product, after which the pressed product is removed from the hot press machine. Next, a roll press machine equipped with a pair of rolls that rotate inward from each other is prepared. The pressed product is then passed between the pair of rolls and subjected to compression and rolling, thereby producing a positive electrode 3 in which positive electrode active material layers 13a and 13b are formed on both main surfaces of the positive electrode current collector 12.

[0108] Thus, in this first embodiment, black mass is used as a recycled material, and the positive electrode 3 is manufactured by a dry process that does not use any solvents such as organic solvents or water. Therefore, there is no need to recover and purify metal salts etc. from black mass, and resources contained in used lithium-ion batteries can be effectively utilized, and the use of expensive rare metals such as Li and ternary materials (Ni, Mn, Co) can be reduced.

[0109] Furthermore, since the cathode is manufactured without using any solvents such as organic solvents or water, material costs can be reduced. In addition, because large-scale drying equipment and solvent recovery equipment for recovering solvents are not required, significant cost reductions are possible, and energy consumption can be drastically reduced.

[0110] Furthermore, as mentioned above, large-scale drying treatment is unnecessary, so CO ２ Because it can reduce emissions and does not use organic solvents harmful to the human body, it can contribute to reducing the environmental burden.

[0111] Furthermore, since no solvent is used for slurry preparation, there are no residues on the positive electrode 3 caused by the solvent or additives in the solvent, making it possible to improve battery characteristics.

[0112] Furthermore, while wet processes may generate pores within the positive electrode after drying, potentially affecting ion conduction, dry processes do not generate such pores, allowing for improved electrode density and, moreover, enhanced mechanical strength of the electrode.

[0113] Thus, in this embodiment, by combining the effective utilization of used lithium-ion batteries with a dry process in the electrode manufacturing process, it is possible to achieve significant cost reductions while ensuring battery performance, and to manufacture an environmentally friendly cathode.

[0114] <Fabrication of the negative electrode> In the fabrication of the positive electrode described above, black mass was recycled and the positive electrode 3 was manufactured using a dry process. In this embodiment, the negative electrode 5 is also manufactured using a dry process.

[0115] Figure 4 is a manufacturing process diagram showing one embodiment of a method for manufacturing a negative electrode as an electrode according to the present invention.

[0116] First, the negative electrode active material (second active material) is prepared. Here, the negative electrode active material is not particularly limited as long as it is an active material that functions as a counter electrode to the positive electrode. Carbon-based materials such as graphite and graphene, lithium metal, and oxide-based negative electrode materials containing lithium titanate can be used, and can be appropriately selected as needed, taking into consideration the desired energy density, cost, etc.

[0117] Then, in step S11, using the same method and procedure as for the production of the positive electrode, for example, using a vibrating stirring device such as a vortex mixer, the negative electrode active material and additives containing a conductive additive and a binder are put into the vibrating stirring device and mixed and stirred, thereby dispersing the additives uniformly or almost uniformly in the negative electrode active material, thereby obtaining a powder mixture (second mixture).

[0118] Furthermore, the preferred mixing ratio of the conductive additive and the binder (conductive additive / binder) is 1 / 5 to 5 / 1, as in the case of positive electrode fabrication described above.

[0119] Furthermore, the mixing ratio of the total conductive additive and binder to the negative electrode active material ((conductive additive + binder) / negative electrode active material) is preferably 1 / 20 to 1 / 3 for the same reasons as in the positive electrode fabrication described above. In addition, the same materials as those used in the positive electrode fabrication can be used for the conductive additive and binder.

[0120] Next, in step S12, the powder mixture obtained in step S11 is placed on both main surfaces of the foil-shaped negative electrode current collector 14, such as a Cu foil, and the powder mixture and the negative electrode current collector 14 are set in the lower mold. Sheet molding is performed dry using a uniaxial press type hot press and a roll press in the same manufacturing method and procedure as for the positive electrode, thereby producing a negative electrode (second dry electrode) 5 in which negative electrode active material layers 15a and 15b are formed on both main surfaces of the negative electrode current collector 14.

[0121] Thus, in this first embodiment, the negative electrode 5 is also manufactured by a dry process, so the same effects as those of the positive electrode manufacturing process described above can be obtained.

[0122] <Manufacturing of Lithium-ion Battery> This lithium-ion battery can be manufactured using the positive electrode 3 and the negative electrode 5 described above, as follows.

[0123] Specifically, the positive electrode 3 and the negative electrode 5 are impregnated with the electrolyte 11, and a separator 4 impregnated with the electrolyte 11 is interposed between the positive electrode 3 and the negative electrode 5. Multiple sets of battery body parts 6, each consisting of the positive electrode 3, separator 4, and negative electrode 5, are then stacked in the negative electrode case 2, and the electrolyte 11 is injected into the internal space. A gasket 10 is then placed around the periphery, and the negative electrode case 2 and the positive electrode terminal 1 are fixed together using a crimping machine or the like to seal the exterior, thereby manufacturing a lithium-ion battery.

[0124] Furthermore, the electrolyte 11 is interposed between the positive electrode 3 and the negative electrode 5, which is the opposing electrode, to transport charge carriers between the two electrodes. As such an electrolyte 11, an electrolyte solution obtained by dissolving an electrolyte salt in an organic solvent, a polymer-based electrolyte solution obtained by adding a polymer such as polyethylene oxide to this, or an ionic liquid-based electrolyte solution obtained by dissolving an ionic liquid such as 1-ethyl-3-methylimidazolium tetrafluoroborate in an electrolyte salt can be used.

[0125] Here, the electrolyte salt is, for example, LiPF ６ LiClO ４ LiBF ４ F ２ LiNO ４ S ２ , C ４ F ９ LiO ３ S, LiN (CF ３ SO ２ ) ２ LiCF ３ SO ３ , C ４ F ９ LiO ３ S, F ２ LiNO ４ S ２ , Li(CF ３ SO ２ ) ２ C, LiH ２ PO ４ , LiCl, (CH ３ CO) ２Various lithium salts, such as Li, can be used.

[0126] Furthermore, as the organic solvent for dissolving the electrolyte 11, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, dimethoxyethane, and mixtures thereof can be used.

[0127] Furthermore, a solid electrolyte may be used as the electrolyte. Both inorganic and polymeric solid electrolytes can be used. For example, Li ７ La ３ Zr ２ O 12 Ya(La,Ti)TiO ３ Oxide-type solid electrolytes such as Li 10 GeP ２ S 12 Examples of sulfide-based solid electrolytes include polypyridene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-ethylene copolymer, and various other copolymers.

[0128] Thus, since this lithium-ion battery is manufactured using the positive electrode 3 and negative electrode 5 produced by the manufacturing method described above, it contributes to resource recycling by effectively utilizing black mass. Furthermore, because the positive electrode 3 and negative electrode 5 are dry electrodes produced by a dry process, it is possible to obtain a lithium-ion battery with good battery characteristics, such as significantly reduced energy consumption, reduced environmental impact, and improved electrode density and mechanical strength of the electrodes, at a low cost.

[0129] Furthermore, in this first embodiment, both the positive electrode 3 and the negative electrode 5 are manufactured using a dry process. However, even if only the positive electrode 3 is manufactured using a dry process, the electrode density and mechanical strength of the positive electrode 3 are improved, making it possible to obtain improved and favorable battery characteristics. In Example 1, described later, in which black mass is used as a recycled material, only the positive electrode 3 is manufactured using a dry process, and the negative electrode 5 is manufactured using a wet process, and the samples are evaluated.

[0130] (Second Embodiment) In the first embodiment described above, black mass is used as the recycled material. However, in this second embodiment, waste cathode material (used cathode material) obtained by disassembling used lithium-ion batteries is used as the recycled material to produce the cathode (first dry electrode) 3.

[0131] Figure 5 is a manufacturing process diagram showing a second embodiment of the method for manufacturing a positive electrode as an electrode according to the present invention.

[0132] First, a used lithium-ion battery using a ternary material as the positive electrode active material is prepared. Then, in step S21, this used lithium-ion battery is fully discharged to deactivate it, in step S22, this used lithium-ion battery is disassembled, and in step S23, the waste positive electrode material and waste separator are separated, and the waste positive electrode material is extracted from the lithium-ion battery.

[0133] Figure 6 is a schematic cross-sectional perspective view showing the process of removing positive electrode material and other components from a used lithium-ion battery.

[0134] The negative electrode case 22 of the used lithium-ion battery lithium 21 contains multiple sets of battery body parts 26, each set consisting of a waste positive electrode material 23, a waste separator 24, and a waste negative electrode material 25, arranged in a stacked manner. The waste positive electrode material 23, waste separator 24, and waste negative electrode material 25 are then removed from this used lithium-ion battery. A cutting tool such as a cutter is then inserted between the waste positive electrode material 23 and the waste separator 24 to separate them.

[0135] Next, in step S24 (Figure 5), the waste cathode material 23 is crushed and pulverized using a pulverizer to obtain a black powder material of about 20 to 100 μm.

[0136] Next, in step S25, a metal salt is prepared, similar to step S1 of the first embodiment, and the blending ratio of the metal salt is adjusted in step S26.

[0137] Next, in step S27, the black mass and the plurality of metal salts are mixed to obtain a mixture.

[0138] Here, the mixing ratio of metal salt to waste cathode material is not particularly limited, but when such waste cathode material is used as recycled material, it is preferable to mix in a total of 35 to 1400 parts by weight of metal salt per 100 parts by weight of waste cathode material.

[0139] In other words, if the total amount of metal salts is less than 35 parts by weight per 100 parts by weight of waste cathode material, the amount of metal salts will be insufficient. Similar to the case where black mass is used as recycled material, it may not be possible to secure a sufficient capacity density compared to lithium-ion batteries manufactured by conventional methods, and there is a risk that a lithium-ion battery with the desired battery capacity cannot be obtained.

[0140] On the other hand, in this second embodiment, since waste cathode material is used as the recycled material, impurities originating from used electrolyte, separator, and counter electrode (negative electrode) are not mixed into the recycled material, as in black mass, and good battery characteristics can be obtained even if the metal salt content is reduced. From this perspective, considering the balance between effective resource utilization and battery characteristics, the upper limit of the total metal salt content is preferably about 1400 parts by weight per 100 parts by weight of waste cathode material.

[0141] In the following step S28, similar to the first embodiment, a heat treatment is performed at a predetermined temperature for a predetermined time to synthesize the positive electrode active material (first active material).

[0142] Subsequently, the process proceeds to step S29, in the same manner and procedure as in the first embodiment, a vibrating stirring device such as a vortex mixer is prepared, and the positive electrode active material and additives containing a conductive additive and a binder are introduced into the vibrating stirring device and vibrating stirring is performed to uniformly or substantially uniformly disperse the additives in the positive electrode active material, thereby obtaining a powder mixture (first mixture).

[0143] Next, in step S30, using the same method and procedure as in step S6 of the first embodiment, for example, by using a hot press method, the powder mixture obtained in step S29 is dry-formed into a sheet on both main surfaces of the positive electrode current collector 12, thereby producing a positive electrode (first dry electrode) 3 in which positive electrode active material layers 13a and 13b are formed on both main surfaces of the positive electrode current collector 12.

[0144] Thus, in this second embodiment, waste cathode material is used as recycled material and the cathode 3 is manufactured by a dry process. Therefore, there is no need for classification and sorting processes or magnetic separation processes as described in Patent Document 2, and resources contained in used lithium-ion batteries can be effectively utilized, reducing the use of expensive rare metals such as Li and ternary materials (Ni, Mn, Co).

[0145] Furthermore, as with the first embodiment, since the positive electrode 3 is manufactured by a dry process, material costs can be reduced, manufacturing costs can be significantly reduced, and energy consumption can be significantly reduced. ２ This method can suppress emissions, contribute to reducing environmental impact, and prevent the accumulation of residues caused by solvents within the positive electrode 3, thereby improving battery performance. Furthermore, it prevents the formation of pores within the positive electrode 3, improving electrode density and the mechanical strength of the electrodes.

[0146] The negative electrode 5 can be manufactured from the negative electrode active material by a dry process using the same method and procedure as in the first embodiment, and a lithium-ion battery can be easily obtained using these positive electrode 3 and negative electrode 5.

[0147] Thus, in this second embodiment as well, by combining the effective utilization of used lithium-ion batteries with a dry process in the electrode manufacturing process, it is possible to obtain a lithium-ion battery that has advantages over conventional batteries, such as ensuring battery performance while significantly reducing costs and being environmentally friendly.

[0148] (Third Embodiment) In the first embodiment, black mass was used as the recycled material, and in the second embodiment, waste cathode material was used. However, in this third embodiment, the waste cathode current collector is separated from the waste cathode material, separating the waste cathode material into a waste cathode active material layer and a waste cathode current collector, and the waste cathode active material layer is used as the recycled material.

[0149] Figure 7 is a manufacturing process diagram showing a third embodiment of the method for manufacturing a positive electrode as an electrode according to the present invention.

[0150] That is, similar to the second embodiment, after the used lithium-ion battery is sufficiently discharged and deactivated, the lithium-ion battery is disassembled, the waste positive electrode material 23 and the waste separator 24 are separated, and the waste positive electrode material 23 is removed (steps S31 to S33).

[0151] In step S34, the waste positive electrode current collector is separated from the waste positive electrode active material layer by a coating agent applied to both main surfaces of the waste positive electrode current collector, thereby bonding the waste positive electrode current collector to the waste positive electrode active material layer. For example, if the coating agent is a water-based coating agent, the waste positive electrode active material layer can be separated from the waste positive electrode current collector by impregnating it in pure water and heating it to about 80°C. Alternatively, if the coating agent is a solvent-based coating agent, the waste positive electrode active material layer can be separated from the waste positive electrode current collector by impregnating it in a solvent and heating it to about 130°C.

[0152] After thoroughly drying the waste positive electrode active material layer obtained in this manner, in the following step S35, the waste positive electrode active material layer is crushed, the waste positive electrode active material layer is turned into a black powder, and a powder is obtained.

[0153] Subsequently, similar to the first embodiment, a plurality of metal salts containing a ternary material and Li salt are prepared, the mixing ratio of each metal salt is adjusted, and then the metal salt is added and heat treatment is performed at a predetermined temperature for a predetermined time, thereby producing a positive electrode active material (first active material material) using the waste positive electrode active material layer as recycled material (steps S36 to S39).

[0154] Subsequently, the process proceeds to step S40, in the same manner and procedure as in the first and second embodiments, using a vibrating stirring device such as a vortex mixer, the positive electrode active material and additives containing a conductive additive and a binder are introduced into the vibrating stirring device and vibrating stirring treatment (dry mixing) is performed to uniformly or substantially uniformly disperse the additives in the positive electrode active material, thereby obtaining a powder mixture (first mixture).

[0155] Next, in step S41, the powder mixture obtained in step S39 is dry-formed into a sheet on both main surfaces of the positive electrode current collector 12 using a method and procedure similar to that of the first and second embodiments, for example, by using a hot press method. This allows for the production of a positive electrode (first dry electrode) 3 in which positive electrode active material layers 13a and 13b are formed on both main surfaces of the positive electrode current collector 12.

[0156] In this third embodiment, the waste positive electrode active material layer is used as a recycled material and the positive electrode is manufactured by a dry process. Therefore, similar to the second embodiment, there is no need for a classification sorting process or magnetic separation process as described in Patent Document 2, and resources contained in used lithium-ion batteries can be effectively utilized, reducing the use of expensive rare metals such as Li and ternary materials (Ni, Mn, Co).

[0157] Furthermore, as with the first and second embodiments, since the positive electrode 3 is manufactured by a dry process, material costs can be reduced, manufacturing costs can be significantly reduced, and energy consumption can be significantly reduced. ２ This method can suppress emissions, contribute to reducing environmental impact, and improve battery performance by preventing the accumulation of residues caused by solvents in the positive electrode 3. Furthermore, it prevents the formation of pores within the positive electrode 3, thereby improving electrode density and the mechanical strength of the electrode.

[0158] The negative electrode 5 can be manufactured from the negative electrode active material by a dry process using the same method and procedure as in the first embodiment, and a lithium-ion battery can be easily obtained using these positive electrode 3 and negative electrode 5.

[0159] Thus, in this third embodiment as well, by combining the effective utilization of used lithium-ion batteries with a dry process in the electrode manufacturing process, it is possible to obtain a lithium-ion battery that has advantages over conventional batteries, such as ensuring battery performance while significantly reducing costs and being environmentally friendly.

[0160] (Other embodiments of the dispersion method) In each of the embodiments described above, a vibration stirring treatment such as a vortex mixer is used to dry mix the electrode active material and additives containing a conductive aid and a binder to disperse them uniformly or substantially uniformly. However, the dispersion method is not limited to vibration stirring treatment, and for example, ball milling, kneading, dry mixing, etc., can be appropriately selected and used as needed.

[0161] For example, in ball milling, electrode active material and additives are placed in a cylindrical pot along with hard balls used as a grinding medium, and the pot is rotated at a predetermined speed to agitate the mixture, thereby uniformly or nearly uniformly dispersing the additives in the electrode active material.

[0162] Furthermore, in the kneading process, the blades inside the kneader are rotated, or two rolls arranged horizontally in parallel are rotated inward relative to each other, while the electrode active material and additives placed in the container are kneaded together. This allows the additives to be uniformly or nearly uniformly dispersed in the positive electrode active material.

[0163] In a dry mixing process, for example, electrode active material and additives are placed in a mill equipped with double blades that rotate in opposite directions, and the double blades are rotated in predetermined directions, thereby uniformly or nearly uniformly dispersing the additives in the electrode active material.

[0164] By selecting and using the most suitable dispersion method as needed, it is possible to uniformly or nearly uniformly disperse additives, including conductive additives and binders, within the positive electrode active material.

[0165] (Other Embodiments of the Molding Method) In the above embodiments, sheet molding was described exemplified by the hot press method. However, the molding method is not limited to the hot press method described above, and an appropriate molding method can be selected depending on the type of conductive additive and binder. For example, polymer fiberization, dry spray deposition, calendering, melt extrusion, 3D printing, vapor deposition, and electrostatic coating can be used.

[0166] The polymer fiber formation method is particularly suitable when polytetrafluoroethylene (PTFE) is used as a binder. PTFE is known to fibrillate (form fibers) when heated to a predetermined temperature and subjected to shear force. The electrode active material and conductive additive become entangled within its fine fibrous structure, forming a mass. This mass can then be pressed onto an electrode current collector to form a sheet, thereby creating an electrode.

[0167] The dry spray deposition method involves charging a powder mixture in which additives are uniformly or nearly uniformly dispersed in the electrode active material with a spray gun, attracting the powder mixture to a grounded electrode current collector, thereby depositing the powder mixture on the electrode current collector, and then forming it into a sheet to create an electrode.

[0168] The calendering method allows for the formation of electrodes in an endless and inexpensive manner without the need for molds, by passing a powder mixture through a pair of calender rolls that rotate inward from each other while heating and pressurizing them to form a sheet.

[0169] In the melt extrusion method, a powder mixture is fed into an extruder, heated and melted as it is pushed forward by a screw or the like, and then passed through a die (mold) at the end of the extrusion port to form a sheet, thereby forming an electrode.

[0170] 3D printing allows for the fabrication of sheet-formed electrodes by applying well-known 3D printing techniques to powder mixtures.

[0171] The vapor deposition method involves heating and evaporating a powder mixture in a vacuum chamber, and then depositing the powder mixture onto an electrode current collector placed inside the vacuum chamber using thin-film formation technology, thereby creating an electrode.

[0172] Electrostatic coating is a method that uses a spray gun to charge a powder mixture, and then utilizes the properties of static electricity to deposit the powder mixture onto an electrode current collector, thereby producing an electrode formed into a sheet.

[0173] By selecting and using the most suitable dispersion treatment method as needed, such as the type of binder, sheet formation can be achieved.

[0174] Furthermore, the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0175] For example, additives added to the positive electrode active material or negative electrode active material only need to contain at least a conductive additive and a binder, and may contain other trace amounts of components as needed, and trace amounts of impurities that inevitably become mixed in are also acceptable.

[0176] Furthermore, in each of the above embodiments, the mixing ratio of the multiple metal salts mixed into the recycled material is adjusted so that, for example, NMC111 can be formed when the metal salts are mixed together and heat-treated for synthesis. However, the metal salts only need to contain Li, Ni, Mn, and Co, and other general formula LiNi salts other than NMC111 are also acceptable. ｘ Mn ｙ Co ｚ O ２ A ternary metal oxide represented by (where x > 0, y > 0, z > 0, x + y + z = 1), for example, NMC433 (LiNi 0.4 Mn 0.3 Co 0.3 O ２ ), NMC523 (LiNi 0.５ Mn 0.２ Co 0.3 O ２ ), NMC622 (LiNi 0.6 Mn 0.2 Co 0.２ O ２ ) and NMC811 (LiNi 0.8 Mn 0.1 Co 0.1 O ２ It goes without saying that the above-mentioned intended effects will also be achieved with respect to ) and the like. Also, the general formula Li(Li ｐ Ni ｑ Mn ｒ Co ｓ ) O ２ Even if the blending ratio is adjusted so that a lithium-rich ternary metal oxide, etc., represented by (where p > 0, q > 0, r > 0, s > 0, p + q + r + s = 1) can be formed, the above-mentioned desired effects can be achieved.

[0177] Also, in each of the above embodiments, a precipitate is prepared from a mixed solution in which each metal powder is dissolved in a solvent, and this is washed and dried to obtain a metal salt. However, a plurality of powdery metal salts may simply be mixed with the recycling material.

[0178] Further, in the above-described third embodiment, the entire waste positive electrode active material layer obtained by separating and peeling the waste positive electrode current collector from the waste positive electrode material is used as the recycling material. However, the waste positive electrode active material layer may be subjected to a centrifugation treatment or the like, and only the metal powder particles contained in the waste positive electrode active material layer may be taken out and used as the recycling material.

[0179] Furthermore, in each of the above embodiments, a cylindrical lithium ion battery has been described. Needless to say, the battery shape is not particularly limited, and it can also be applied to square, sheet, coin, etc. Also, the packaging method is not particularly limited, and an aluminum laminate film, a molded resin, or the like may be used. Next, examples of the present invention will be specifically described.

[0180] [Preparation of Samples] (Sample No. 1) First, black mass was procured from Kawajima Co., Ltd. and prepared. Also, as the Ni source, (CH ３ COO) ２ Ni·4H ２ O (molecular weight: 248.84), as the Mn source, (CH ３ COO) ２ Mn·4H ２ O, (molecular weight: 245.09), as the Co source, (CH ３ COO) ２ Co·4H ２ O (molecular weight: 249.08), and as the Li source, CH ３ COOLi·2H ２ O (molecular weight: 102.02) of each metal salt powder were prepared.

[0181] And, when the mixing ratios of Li, Ni, Mn, and Co are such that Li:Ni:Mn:Co = 1:1 / 3:1 / 3:1 / 3 in terms of molar ratio when these metal salt powders are mixed and synthesized, (CH ３ COO) ２ Ni·4H ２ O was 82.95 g, (CH ３ COO) ２ Mn·4H ２81.70 g of O, (CH ３ COO) ２ Co·4H ２ O was weighed at 83.03 g, and CH ３ COOLi·2H ２ O was weighed at 107.12 g. These weighed substances (total 354.80 g) were dissolved in 2000 g of pure water to prepare a mixed solution.

[0182] On the other hand, citric acid monohydrate ((HOOCCH ２ )( ２ C(OH)COOH·H ２ [[ID=]19]O) (molecular weight 210.14) was dissolved in 2000 g of pure water to prepare a citric acid aqueous solution.

[0183] Next, the above mixed solution and the above citric acid aqueous solution were mixed to prepare a precipitate. After filtering with a paper filter to remove the supernatant, this precipitate was washed three times and dried to obtain a metal salt. Then, the black mass and the metal salt were mixed so that the total of the metal salts was 350 parts by weight with respect to 100 parts by weight of the black mass, and heat treatment was performed at a temperature of 800 °C for 1 hour, and then it was naturally cooled until it dropped to room temperature. Then, this was sieved using a stainless steel mesh with a mesh opening of 75 μm, whereby a positive electrode active material mainly composed of NMC111 was synthesized.

[0184] Next, the positive electrode active material, carbon black, and PVDF were put into a vortex mixer so that the positive electrode active material was 80 wt%, carbon black as a conductive carbon was 15 wt%, and PVDF as a binder was 5 wt%. The vortex mixer was driven to vibrate and stir for 1 minute to disperse the carbon black and PVDF uniformly or substantially uniformly in the positive electrode active material, thereby obtaining a powder mixture.

[0185] Incidentally, the carbon black used was manufactured by Lion Corporation (product name: Ketjenblack EC600JD), and the PVDF used was manufactured by Arkema. [[ID=]]30]

[0186] Next, a uniaxial press type hot press machine having an upper die and a lower die was prepared. Then, an Al foil with a thickness of 16 μm was placed in the lower die, and the powder mixture was placed on the Al foil. The upper die was driven toward the lower die with a pressure of 10 MPa while heating to a temperature of 180°C, and the powder mixture was subjected to pressurization for 1 minute to obtain a pressed product. Next, using a roll press machine equipped with a pair of rolls that rotate inward from each other, the pressed product was passed between the pair of rolls to form a sheet, and a positive electrode, i.e., a first dry electrode, was fabricated by forming a positive electrode active material layer with a thickness of 50 μm on a positive electrode current collector made of Al foil.

[0187] On the other hand, the negative electrode was fabricated using a conventional wet process.

[0188] Specifically, first, graphite (manufactured by Nippon Kuroen Kogyo Co., Ltd.) was prepared as the negative electrode active material. Then, 2.7 g of this graphite and 6 g of N-methyl-2-pyrrolidone (hereinafter referred to as "NMP") (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were mixed and stirred for 120 seconds using a stirring and defoaming device (manufactured by Kurabo Corporation, Mazelstar). After that, 0.15 g of carbon black was added and stirred for another 360 seconds using the same stirring and defoaming device to obtain the stirred product.

[0189] Next, an NMP solution was prepared by dissolving 5 wt% PVDF in NMP. Then, 3.0 g of the NMP solution was added to the stirred mixture and stirred for 360 seconds using the stirring and degassing device, followed by stirring for another 180 seconds, then stirring for another 360 seconds, and finally degassing for 90 seconds to obtain a slurry-like coating solution.

[0190] Next, using the doctor blade method, the coating solution was applied onto a 19 μm thick Cu foil to form a 50 μm thick coating film, which was then dried at 100°C for 8 hours to produce a negative electrode with the Cu foil as the negative electrode current collector.

[0191] Next, the positive and negative electrodes formed in this manner were impregnated with a carbonate-based electrolyte, and a separator made of polypropylene was interposed between the positive and negative electrodes. Furthermore, the carbonate-based electrolyte was injected between the positive and negative electrodes, thereby creating the flat cell (experimental simple cell) of sample number 1.

[0192] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 145.9mAh / g.

[0193] (Sample No. 2) A flat cell for Sample No. 2 was prepared using the same method and procedure as for Sample No. 1, except that the carbon black content in the powder mixture was 10 wt% and the PVDF content was 10 wt%.

[0194] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 140.5mAh / g.

[0195] (Sample No. 3) A flat cell for Sample No. 3 was prepared using the same method and procedure as for Sample No. 1, except that the carbon black content in the powder mixture was 5 wt% and the PVDF content was 15 wt%.

[0196] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 132.6mAh / g.

[0197] (Sample No. 4) As a comparative example, both the positive and negative electrodes were fabricated using a wet process.

[0198] Specifically, the positive electrode active material was synthesized using the same method and procedure as for sample number 1. Next, 2.7 g of this positive electrode active material and 6 g of NMP were mixed and stirred for 120 seconds using a stirring and defoaming device. Then, 0.15 g of carbon black was added to this mixture, and the mixture was stirred for another 360 seconds using the same stirring and defoaming device to obtain the stirred product.

[0199] Next, an NMP solution was prepared by dissolving 5 wt% PVDF in NMP. Then, 3.0 g of the NMP solution was added to the stirred mixture and stirred for 360 seconds using the stirring and degassing device, followed by stirring for another 180 seconds, then stirring for another 360 seconds, and finally degassing for 90 seconds to obtain a slurry-like coating solution.

[0200] Next, using the doctor blade method, the coating solution was applied onto a 16 μm thick Al foil to form a 50 μm thick coating film, which was then dried at 100°C for 8 hours to produce a positive electrode with the Al foil as the positive electrode current collector.

[0201] On the other hand, a negative electrode was prepared using the same method and procedure as for sample number 1, and a flat cell for sample number 4 was prepared using this positive and negative electrode.

[0202] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 129.5mAh / g.

[0203] [Sample Evaluation] For each of the samples numbered 1 to 4, the cycle characteristics were evaluated by repeating the charge and discharge cycle 100 times within a voltage range of 2.0V to 4.6V.

[0204] Table 1 shows the manufacturing conditions for the positive and negative electrodes in samples 1 to 4, and Table 2 shows the initial capacity density and the capacity density (mAh / g) after each cycle for samples 1 to 4.

[0205]

[0206]

[0207] As is clear from the comparison between samples 1-3 and sample 4, the initial capacity density of sample 4 was 129.5 mAh / g, while that of samples 1-3 was 132.6-145.9 mAh / g. It was found that by fabricating the positive electrode using a dry process, the initial capacity density improved, and even after 50 cycles, a better capacity density was obtained compared to sample 4. In particular, samples 1 and 2, which had a carbon black content equal to or greater than that of PVDF, were found to have a better capacity density than sample 4 even after 100 cycles. This is likely because, since the positive electrode was fabricated using a dry process, no pores were generated within the positive electrode as would occur when the positive electrode was fabricated using a wet process, resulting in improved electrode density and better conductivity, which in turn led to even better cycle characteristics.

[0208] Furthermore, after 100 cycles, sample number 3 showed a decreasing tendency in capacity density compared to sample number 4. This is likely because sample number 3 contains less carbon black than PVDF, resulting in a slight decrease in conductivity and consequently a decrease in capacity density.

[0209] In any case, in addition to the effective utilization of resources using black mass, it was confirmed that by manufacturing the cathode using a dry process, cycle characteristics that are roughly equivalent to or better than those obtained when manufactured using a wet process can be obtained, resulting in advantages in various aspects such as reduced energy consumption, reduced costs for equipment and materials, and reduced environmental impact.

[0210] In Example 1, black mass was used as the recycled material to evaluate the cycle characteristics, while in Example 2, waste cathode material was used as the recycled material to evaluate the cycle characteristics.

[0211] [Sample preparation] (Sample number 11) First, the composition formula LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ Lithium-ion batteries containing a positive electrode active material layer primarily composed of (NMC111) were procured from Fujifilm Wako Pure Chemical Industries and prepared.

[0212] Then, this lithium-ion battery was subjected to more than 3,000 charge-discharge cycles to deactivate its capacity, and it was designated as a used lithium-ion battery. Next, this lithium-ion battery was disassembled, and the used waste positive electrode material, waste separator, and waste negative electrode material were removed from the negative electrode case. Furthermore, a utility knife was inserted between the waste positive electrode material and the waste separator to peel and separate them, and the waste positive electrode material was crushed into a black powder to produce a recycled material.

[0213] Subsequently, using the same method and procedure as for sample number 1 in Example 1, the metal salt was prepared to a predetermined mixing ratio. The waste cathode material and the metal salt were then mixed so that the total content of the metal salt was 350 parts by weight per 100 parts by weight of the recycled waste cathode material. The cathode active material was then synthesized by heat treatment.

[0214] Next, the positive electrode active material, carbon black, and PVDF were placed into a vortex mixer in a composition of 80 wt%, 15 wt%, and 5 wt%, respectively. The vortex mixer was then driven and vibrated for 1 minute to uniformly or nearly uniformly disperse the carbon black and PVDF within the positive electrode active material, thereby obtaining a powder mixture.

[0215] Next, using the same method and procedure as for sample number 1, a pressed sample was prepared by the hot press method, and then a positive electrode was obtained by sheet formation using a roll press machine.

[0216] Furthermore, a negative electrode was prepared using the same method and procedure as for sample number 1, and a flat cell for sample number 11 was prepared using this positive and negative electrode.

[0217] When this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, the capacity density (initial value) was 148.4mAh / g.

[0218] (Sample No. 12) A flat cell for sample No. 12 was prepared using the same method and procedure as for sample No. 11, except that the carbon black content in the powder mixture was 10 wt% and the PVDF content was 10 wt%.

[0219] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 143.5mAh / g.

[0220] (Sample No. 13) A flat cell for sample No. 13 was prepared using the same method and procedure as for sample No. 11, except that the carbon black content in the powder mixture was 5 wt% and the PVDF content was 15 wt%.

[0221] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 135.6mAh / g.

[0222] (Sample No. 14) The positive electrode was prepared using the same method and procedure as for Sample No. 11.

[0223] Next, the negative electrode was prepared using a dry process. Specifically, graphite, carbon black, and PVDF were mixed in a ratio of 80 wt% graphite, 15 wt% carbon black, and 5% PVDF. These were placed in a vortex mixer, and the vortex mixer was driven to vibrate and stir for one minute to disperse the mixture uniformly or nearly uniformly, thereby obtaining a powder mixture.

[0224] Then, the negative electrode was prepared using the same method and procedure as for sample number 11, except that the Al foil was replaced with Cu foil. Using these positive and negative electrodes, the flat cell of sample number 14 was prepared.

[0225] When this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, the capacity density (initial value) was 149.1mAh / g.

[0226] (Sample No. 15) A flat cell of sample No. 15 was prepared by a wet process using the same method and procedure as sample No. 4, except that black mass was replaced with waste cathode material.

[0227] When this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, the initial capacity density was 139.8mAh / g.

[0228] [Sample Evaluation] For each sample from sample numbers 11 to 15, the cycle characteristics were evaluated by repeating the charge and discharge cycle 100 times within a voltage range of 2.0V to 4.6V.

[0229] Table 3 shows the manufacturing conditions for the positive and negative electrodes in samples 11 to 15, and Table 4 shows the initial capacity density and the capacity density (mAh / g) after each cycle for these samples 11 to 15.

[0230]

[0231]

[0232] As is clear from the comparison between sample numbers 11, 12, and 14 and sample number 15, the initial capacity density of sample number 15 was 139.8 mAh / g, while that of samples 11, 12, and 14 was 143.5 to 149.1 mAh / g. This indicates that by fabricating the positive electrode using a dry process, the initial capacity density is improved, and a good capacity density can be obtained even after 100 cycles. This is thought to be because, since the positive electrode is fabricated using a dry process, no pores are generated within the positive electrode as would occur when the positive electrode is fabricated using a wet process, resulting in improved electrode density and better conductivity, which leads to even better cycle characteristics.

[0233] Furthermore, as is clear from the comparison between sample number 11 and sample number 14, it was found that by fabricating both the positive and negative electrodes using a dry process, even better cycle characteristics can be obtained compared to when only the positive electrode is fabricated using a dry process.

[0234] Furthermore, sample number 13 exhibits slightly lower cycle characteristics compared to sample number 15. This is likely because sample number 13 contains less carbon black than PVDF, resulting in a slight decrease in conductivity and consequently a lower capacity density.

[0235] In any case, in addition to the effective utilization of resources by using waste cathode material, it was found that by manufacturing the cathode, and preferably both the cathode and anode, using a dry process, it is possible to obtain cycle characteristics that are approximately equivalent to or better than those obtained when manufactured using a wet process. In other words, it was confirmed that manufacturing electrodes using a dry process has advantages over the wet process in various respects, such as reduced energy consumption, reduced costs for equipment and materials, and reduced environmental impact.

[0236] In Example 1, black mass was used as the recycled material, and in Example 2, waste cathode material was used as the recycled material. However, in Example 3, the waste cathode active material layer was used as the recycled material, and the cycle characteristics were evaluated.

[0237] [Sample Preparation] (Sample No. 21) Waste cathode material was extracted from a used lithium-ion battery using the same method and procedure as in Example 1.

[0238] Next, the waste cathode material was impregnated with pure water and heated to 80°C to separate the waste cathode active material layer from the waste cathode current collector. The separated waste cathode active material layer was then placed in a drying container and dried at 80°C for 24 hours. After that, the dried waste cathode active material layer was crushed to produce a black powder, which was then used as the recycled material.

[0239] Subsequently, using the same method and procedure as for sample number 1 in Example 1, the metal salt was prepared to a predetermined mixing ratio. The waste cathode material and the metal salt were then mixed so that the total content of the metal salt was 350 parts by weight per 100 parts by weight of the recycled waste cathode material. The cathode active material was then synthesized by heat treatment.

[0240] Next, the positive electrode active material, carbon black, and PVDF were placed into a vortex mixer in a composition of 80 wt% positive electrode active material, 15 wt% carbon black, and 5 wt% PVDF. The vortex mixer was then driven and vibrated and stirred for 1 minute to disperse the carbon black and PVDF uniformly or nearly uniformly within the positive electrode active material, thereby obtaining a powder mixture.

[0241] Subsequently, a pressed sample was prepared using the same method and procedure as for sample number 1 by hot pressing, and then a sheet-formed positive electrode was obtained using a roll press machine.

[0242] Furthermore, a negative electrode was prepared using the same method and procedure as for sample number 1, and a flat cell for sample number 21 was prepared using this positive and negative electrode.

[0243] When this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, the capacity density (initial value) was 149.7mAh / g.

[0244] (Sample No. 22) A flat cell for sample No. 22 was prepared using the same method and procedure as for sample No. 21, except that the carbon black content in the powder mixture was 10 wt% and the PVDF content was 10 wt%.

[0245] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 142.2mAh / g.

[0246] (Sample No. 23) A flat cell for sample No. 23 was prepared using the same method and procedure as for sample No. 21, except that the carbon black content in the powder mixture was 5 wt% and the PVDF content was 15 wt%.

[0247] Then, this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, resulting in a capacity density (initial value) of 134.5mAh / g.

[0248] (Sample No. 24) A flat cell for sample No. 24 was prepared using a wet process, with the same method and procedure as for sample No. 15, except that the waste cathode material was replaced with a waste cathode active material layer.

[0249] When this flat cell was charged at a C rate of 0.1C until it reached 4.6V, and then discharged to 2.0V, the capacity density (initial value) was 139.5mAh / g.

[0250] [Sample Evaluation] For each sample from sample numbers 21 to 24, the cycle characteristics were evaluated by repeating the charge and discharge cycle 100 times within a voltage range of 2.0V to 4.6V.

[0251] Table 5 shows the manufacturing conditions for the positive and negative electrodes in samples 21-24, and Table 6 shows the initial capacity density and the capacity density (mAh / g) after each cycle for samples 21-24.

[0252]

[0253]

[0254] As is clear from the comparison between sample numbers 21-23 and sample number 24, the volume density after 100 cycles for sample number 24 was 78.4 mAh / g, a significant decrease of 44% from the initial value, while for samples number 21-23 it was 100.2-113.8 mAh / g, a decrease of only about 23-25% from the initial value, indicating an improved volume recovery rate.

[0255] This is because the recycled waste positive electrode active material layer avoids the inclusion of impurities such as Al originating from the positive electrode current collector. It is believed that the combination of this recycled material and the dry process improves the capacity recovery rate and thus the cycle characteristics.

[0256] In any case, in addition to the effective utilization of resources using the waste positive electrode active material layer, by manufacturing the positive electrode, and preferably both the positive and negative electrodes, using a dry process, it is possible to obtain cycle characteristics that are approximately equivalent to or better than those obtained when manufactured using a wet process. Similar to Examples 1 and 2, it was confirmed that this method has advantages in various aspects, such as reduced energy consumption, reduced equipment and material costs, and reduced environmental impact.

[0257] By using black mass, waste electrode material, and waste electrode active material layer obtained from used lithium-ion batteries as recycled materials and adding predetermined amounts of ternary material and Li salt, electrode active material can be synthesized. Electrodes can then be manufactured using this electrode active material in a dry process. This allows for the efficient use of resources while contributing to reduced energy consumption, lower equipment and material costs, and reduced environmental impact, resulting in lithium-ion batteries with excellent battery characteristics.

[0258] 3 Positive electrode (first dry electrode) 5 Negative electrode (second dry electrode) 11 Electrolyte 12 Positive electrode current collector (first metal foil) 13a, 13b Positive electrode active material layer (thin film) 14 Negative electrode current collector (second metal foil) 15a, 15b Negative electrode active material layer (thin film) 23 Waste positive electrode material (waste electrode material)

Claims

1. A method for manufacturing electrodes using recycled lithium-ion batteries, wherein the waste electrode material obtained by disassembling the recycled lithium-ion battery comprises a waste electrode active material layer and a waste electrode current collector bonded to the electrode active material layer, and further comprises: a step of preparing black mass obtained by processing the entire recycled lithium-ion battery, the waste electrode material, and the waste electrode active material layer; a step of preparing a plurality of metal salts containing Ni, Mn, Co, and Li components, and adjusting the mixing ratio of these metal salts; a step of using the black mass, the powdered waste electrode material, and the powdered waste electrode active material layer as recycled material, mixing the recycled material with the plurality of metal salts, and subjecting it to heat treatment to synthesize a first active material; and a step of mixing the first active material with an additive containing at least a conductive additive and a binder, and subjecting it to dry dispersion treatment to obtain a first mixture. A method for manufacturing an electrode, characterized by comprising the step of dry-forming a sheet of the first mixture on at least one main surface of a first metal foil to produce a first dry electrode.

2. The method for manufacturing an electrode according to claim 1, comprising the steps of: mixing an additive containing at least a conductive additive and a binder with a second active material, and subjecting it to a dry dispersion treatment to obtain a second mixture; and dry forming the second mixture into a sheet on at least one main surface of a second metal foil to produce a second dry electrode which will be a counter electrode to the first dry electrode.

3. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the binder includes one or more selected from the group belonging to the category of thermoplastic materials.

4. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the conductive additive includes at least one selected from the group consisting of conductive carbon, carbon fiber, carbon nanotube, graphene, and conductive polymer.

5. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the mixing ratio of the conductive additive and the binder is 1 / 5 to 5 / 1 on a weight basis.

6. The method for manufacturing an electrode according to claim 1, characterized in that the mixing ratio of the additive to the first active material is 1 / 20 to 1 / 3 in terms of weight ratio.

7. The method for manufacturing an electrode according to claim 2, characterized in that the mixing ratio of the additive to the second active material is 1 / 20 to 1 / 3 by weight.

8. The method for manufacturing an electrode according to claim 2, characterized in that the second active material includes one selected from the group consisting of carbon-based materials, lithium metals, and oxide-based materials including lithium titanate.

9. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the dispersion treatment is carried out by any method selected from vibration stirring, ball milling, kneading, and dry mixing.

10. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the sheet molding is carried out by a molding method selected from the following: hot pressing, polymer fiberization, dry spray deposition, calendering, melt extrusion, 3D printing, vapor deposition, and electrostatic coating.

11. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the content of the plurality of metal salts is 35 to 5000 parts by weight in total with respect to 100 parts by weight of the recycled material.

12. The method for manufacturing an electrode according to claim 11, characterized in that the content of the plurality of metal salts is 35 to 1400 parts by weight in total with respect to 100 parts by weight of the recycled material.

13. The method for manufacturing an electrode according to claim 1 or 2, characterized in that, when the waste electrode active material layer is to be used as the recycled material, the waste electrode material is impregnated in a solvent and heated to separate the waste electrode active material layer from the waste electrode current collector, and the waste electrode active material layer is to be used as the recycled material.

14. A method for manufacturing an electrode according to claim 1 or 2, characterized in that each metal powder containing each component forming the metal salt is dissolved in a solvent to prepare a mixed solution, the mixed solution is treated to produce a precipitate, the metal salt is obtained from the precipitate, and the recycled material and the metal salt are mixed.

15. The method for manufacturing an electrode according to claim 1 or 2, characterized in that the heat treatment is performed at a temperature of 650 to 1100°C for 0.5 to 12 hours.

16. When the plurality of metal salts are synthesized by mixing these plurality of metal salts, the general formula is LiNi ｘ Mn ｙ Co ｚ O ２ (where x > 0, y > 0, z > 0, x + y + z = 1), or the general formula Li(Li ｐ Ni ｑ Mn ｒ Co ｓ )O ２ (where p > 0, q > 0, r > 0, s > 0, p + q + r + s = 1). The manufacturing method of the electrode according to claim 1 or claim 2 is characterized in that the blending ratio is adjusted and mixed with the recycled material so that a metal oxide represented by the formula can be formed.

17. Composition formula LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ A method for manufacturing an electrode according to claim 16, characterized by including the following:

18. A method for manufacturing a lithium-ion battery having a positive electrode, a negative electrode, and an electrolyte, and manufactured by reusing a used lithium-ion battery, characterized in that the lithium-ion battery is manufactured using an electrode manufactured by the manufacturing method described in claim 1 or claim 2.

19. A lithium-ion battery having a positive electrode, a negative electrode, and an electrolyte, formed by reusing a used lithium-ion battery, wherein the first active material contains any of the following: black mass obtained by processing the entire used lithium-ion battery, waste electrode material obtained by disassembling the used lithium-ion battery, and waste electrode active material layer obtained by separating the waste electrode current collector from the waste electrode material, and is formed of a metal oxide whose main components include Ni, Mn, Co, and Li, and the positive electrode is formed of a first dry electrode comprising a first metal foil and a thin film mainly composed of the first active material formed on at least one main surface of the first metal foil.

20. The lithium-ion battery according to claim 19, characterized in that the negative electrode is formed of a second dry electrode comprising a second metal foil and a thin film mainly composed of a second active material formed on at least one main surface of the second metal foil.

21. The lithium-ion battery according to claim 20, characterized in that the second active material includes one selected from the group consisting of carbon-based materials, lithium metal, and oxide-based anode materials including lithium titanate.

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