Method for producing electrode active material, electrode, and lithium ion battery

Abstract

An electrode active material according to the present invention is produced by performing a heat treatment after adding a plurality of metal salts which each contain metal components that are Li, Ni, Co, and Mn or Al to black mass that is obtained by processing used lithium ion batteries, so that the black mass and the metal salts are reacted with each other. It is preferable that the addition amount of the metal salts is 10-25 parts by weight relative to 100 parts by weight of the black mass. This lithium ion battery has a positive electrode 4, a negative electrode 6, and an electrolyte 8. A positive electrode active material 3, which serves as a main body of the positive electrode 4, is formed of an electrode active material that is produced as described above. By directly using the black powder of the black mass as described above, it is possible to achieve an electrode active material, an electrode, and a lithium ion battery, which have high practicality and are capable of ensuring desired battery characteristics without requiring much time and effort such as recovery of metal salts or the like from black mass and purification of the metal salts or the like.

Description

Method for manufacturing electrode active material, electrode, and lithium ion battery

[0001] The present invention relates to a method for producing an electrode active material, an electrode, and a lithium ion battery, and more particularly to a method for producing an electrode active material using black mass, an electrode having the electrode active material produced by this method, and a lithium ion battery in which the positive electrode active material is formed from the electrode active material.

[0002] With the expansion of the market for portable electronic devices such as mobile phones, laptops, and tablet computers, there has been active development of secondary batteries as cordless power sources for these devices. Furthermore, against the backdrop of global warming and the depletion of petroleum resources, there has also been active development of electric vehicles and hybrid vehicles powered by secondary batteries.

[0003] Under these circumstances, secondary batteries have been developed that use alkali metal ions, such as lithium ions, as charge carriers and utilize the electrochemical reactions that accompany the transfer of electric charges. In particular, lithium ion batteries, which have a high energy density, are now widely used.

[0004] Among the components of lithium-ion batteries, electrode active materials are substances that directly contribute to the battery electrode reactions, namely, the charge and discharge reactions. They play a central role in lithium-ion batteries because they are charged and discharged by utilizing the insertion and desorption reactions of lithium ions into and from the electrode active material.

[0005] In the early stages of development of this type of lithium-ion battery, the electrode active material, especially the positive electrode active material, was LiCoO ２ However, due to the high cost of Co and the demand for higher capacity and lower cost associated with the expansion of battery applications, ternary materials in which part of the Co is replaced with Ni or Mn have attracted attention in recent years, and lithium-ion batteries using such ternary materials as the positive electrode active material have been actively researched and developed.

[0006] However, while demand for lithium-ion batteries is expected to continue to increase in the future, Li and the Co, Ni, and Mn that make up the ternary materials are all rare metals, and there is a risk that it will become difficult to secure a supply of raw materials in the future.

[0007] In recent years, attention has been focused on technology that aims to recover and recycle lithium-ion battery materials from the black powder known as "black mass" that is generated by processing used lithium-ion batteries.

[0008] For example, Patent Document 1 proposes a method for recovering and purifying valuable metals, including one or more of Ni, Mn, Co, and Li, from black mass obtained from recycling lithium-ion batteries.

[0009] In Patent Document 1, black mass is subjected to reduction acid leaching to produce an acid leaching slurry containing a pregnant acid leaching solution containing valuable metals (Ni, Mn, Co) and impurities, and insoluble matter; the insoluble matter is separated and removed from the pregnant acid leaching solution, and the pH of the pregnant acid leaching solution is then adjusted to precipitate and remove impurities from the pregnant acid leaching solution. Subsequently, an ion exchange resin is used to remove remaining impurities from the pregnant acid leaching solution, and a Li basic solution is used to regenerate the ion exchange resin and produce a mixed precipitate slurry. The pH of the pregnant acid leaching solution is then adjusted to separate the mixed precipitate containing valuable metals from a Li-containing solution. Metal salts that serve as precursors for a ternary positive electrode active material are recovered from the mixed precipitate. Furthermore, the Li-containing solution is subjected to salt decomposition and crystallization to obtain Li, a Li source. ２ CO ３ are being collected.

[0010] In this way, in Patent Document 1, a precursor of a ternary positive electrode active material containing Li and Li are obtained from black mass by a chemical process. ２ CO ３ We are trying to collect and reuse resources.

[0011] Patent Document 2 also proposes a method for extracting metals from the black mass of lithium ion batteries.

[0012] That is, in Patent Document 2, a fraction of non-metallic materials is separated from the black mass to recover a black mass containing an anode material and a cathode material, then an acid leaching is carried out by adding a gas containing sulfur dioxide and molecular oxygen as an extractant to a sulfuric acid-containing solution to dissolve the cathode material in the black mass and recover a leachate solution containing the cathode material, an initial fraction of metallic materials is separated from the leachate solution, and a main fraction containing at least one of Mn, Co, Ni, and Li is recovered.

[0013] Thus, in Patent Document 2, after removing non-metallic components from black mass by pretreatment, sulfuric acid and an extractant are used to sequentially separate and recover initial fractions of metallic materials from each leaching solution containing cathode material, thereby attempting to reuse resources.

[0014] Furthermore, Patent Document 3 proposes a method for recovering a metal group from waste batteries, waste positive electrode materials, or a mixture thereof containing a metal group consisting of at least two of Co, Ni, and Mn and impurities, the method including removing impurities from the waste batteries, waste positive electrode materials, or a mixture thereof, and then recovering the metal group as a mixture of metal salts.

[0015] In Patent Document 3, waste batteries, waste cathode material, or a mixture thereof is leached with sulfuric acid to produce a leachate, and if impurities such as Fe, Cr, Cu, F, or C are contained, the pH of the leachate is adjusted to precipitate and remove the impurities, or the impurities are separated into the solvent side by solvent extraction, and then the impurities are removed from the leachate by solid-liquid separation, and metal salts of Co, Ni, and Mn are recovered. This makes it possible to recover the waste batteries and waste cathode material as a mixture of metal salts from the leachate without separating them into individual metal salts of Mn, Co, and Ni, thereby eliminating the effort of individual separation and aiming to reduce the cost of recycling the cathode material.

[0016] As described above, all of Patent Documents 1 to 3 aim to remove impurities from black mass (waste batteries, waste cathode materials) by a wet process, and then separate and recover metal salts or mixtures thereof or metal fractions (hereinafter referred to as "metal salts, etc."), recycle the resources, and use them in the production of new batteries.

[0017] JP 2023-174586 A (Claim 11, paragraphs

[0028] to

[0029] , Figure 1, etc.) JP 2024-516955 A (Claim 1, paragraphs

[0063] to

[0066] , Figures 2a, 2b, etc.) JP 2014-156649 A (Claim 1 to 3, paragraphs

[0029] ,

[0050] )

[0018] However, the methods disclosed in Patent Documents 1 to 3 involve complicated processing steps for extracting battery materials from black mass, separating them, and recycling them, and the cost of the equipment is high, which leads to high costs and makes them less practical.

[0019] The present invention has been made in view of the above circumstances, and aims to provide a method for producing an electrode active material that can recycle resources and obtain a highly practical electrode active material that can ensure desired battery characteristics without the need for the time and effort of recovering and purifying metal salts and the like from black mass; an electrode having the electrode active material produced by this production method; and a lithium ion battery that uses this electrode active material as the positive electrode active material.

[0020] The present inventors have conducted extensive research to achieve the above object, and have discovered that by adding small amounts of metal salts containing Li, Co, Ni, and Mn or Al, which can constitute an electrode active material, to black mass and then performing a heat treatment, the black mass and the metal salt react to bond the metal component to the black mass, thereby making it possible to obtain a highly practical electrode active material that can ensure the desired battery characteristics.

[0021] The present invention has been made based on this finding, and the method for producing an electrode active material according to the present invention is characterized in that a plurality of metal salts containing Li, Ni, Co, and either Mn or Al, respectively, are added to black mass obtained by treating used lithium-ion batteries, followed by heat treatment, and the black mass and the metal salts are reacted to produce an electrode active material.

[0022] This eliminates the need for the laborious process of recovering metal salts and metal components from the black mass, allows for the effective use of used lithium-ion batteries, and makes it possible to obtain an electrode active material that is highly practical and has the desired battery performance at low cost.

[0023] In the method for producing an electrode active material of the present invention, the amount of the metal salt added is more preferably 10 to 25 parts by weight per 100 parts by weight of the black mass.

[0024] This makes it possible to obtain an electrode active material having the desired battery performance and of practical value simply by adding a small amount of a predetermined metal salt to the black mass.

[0025] In the method for producing an electrode active material of the present invention, the heat treatment is preferably carried out at a temperature of 700 to 900° C., and the heat treatment is preferably carried out for 1 to 2 hours.

[0026] By appropriately adjusting the heat treatment temperature and heat treatment time in this way, an electrode active material having the desired battery performance can be easily produced.

[0027] Furthermore, in the method for producing an electrode active material of the present invention, when the plurality of metal salts are mixed and synthesized, LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ (hereinafter also referred to as "NMC111"), LiNi 0.4 Mn 0.3 Co 0.3 O ２ (hereinafter also referred to as "NMC433"), LiNi 0.5 Mn 0.2 Co 0.3 O ２ (hereinafter also referred to as "NMC523"), LiNi 0.5 Mn 0.3 Co 0.2 O ２ (hereinafter also referred to as "NMC532"), LiNi 0.6 Mn 0.2 Co 0.2 O ２ (hereinafter also referred to as "NMC622"), LiNi 0.8 Mn 0.1 Co 0.1 O ２ (hereinafter also referred to as "NMC811"), LiNi 0.8 Co 0.15 Al 0.05 O ２ (hereinafter also referred to as "NCA"), and the general formula Li1＋ｘ Ni 2 / （3+3ｙ） Mn 2x / （3+3ｙ） Co 2 / （3+3ｙ） O ２ It is preferable to add the compounding ratio to the black mass so as to be able to form one oxide selected from the group of lithium-rich compositions (hereinafter also referred to as "lithium-rich NMC composition") represented by the formula (where x>0, y is a positive integer).

[0028] When a plurality of metal salts are mixed and synthesized in this manner, by appropriately blending the metal components Ni, Co, and Mn or Al in a predetermined ratio, it becomes possible to produce electrode active materials having the desired battery performance for various applications at low cost.

[0029] The electrode according to the present invention is characterized by having an electrode active material produced by the above-mentioned production method.

[0030] This allows the electrode active material to be produced directly from black mass, which allows for efficient resource recycling and makes it possible to obtain new and useful battery electrodes at low cost.

[0031] Furthermore, the electrode of the present invention is characterized in that the crystalline structure of the electrode active material is a layered rock salt type.

[0032] As a result, the electrode active material has a crystalline structure in which Li is arranged between multiple metal oxide layers containing Ni, Co, and Mn or Al, and the two-dimensional diffusion of Li facilitates the battery reaction due to the insertion and desorption of Li ions, thereby making it possible to obtain the desired lithium-ion battery.

[0033] The lithium ion battery according to the present invention has a positive electrode, a negative electrode, and an electrolyte, and repeats charge and discharge reactions through a battery electrode reaction using lithium ions as a charge carrier, and is characterized in that the positive electrode active material that constitutes the main component of the positive electrode is formed from an electrode active material produced by the above-described production method.

[0034] Since the positive electrode active material is formed from the electrode active material produced by the above-mentioned production method, it is possible to obtain a new and useful lithium ion battery that contributes to resource circulation by effectively utilizing used lithium ion batteries, without the need for the effort of recovering and purifying metal salts from black mass.

[0035] In the lithium ion battery of the present invention, the negative electrode active material that is the main component of the negative electrode is preferably formed of lithium metal.

[0036] By forming the negative electrode active material from lithium metal in this way, it is possible to obtain a lithium ion battery with a higher energy density than when a carbon-based material or the like is used.

[0037] According to the electrode active material of the present invention, a plurality of metal salts each containing a metal component of Li, Ni, Co, Mn, or Al are added to black mass obtained by treating used lithium-ion batteries, followed by heat treatment, and the black mass and the metal salts are reacted to produce an electrode active material. This eliminates the need for the conventional effort of recovering and purifying metal salts, etc. from black mass, and makes it possible to effectively utilize the resources contained in used lithium-ion batteries, thereby enabling the production of a novel, useful electrode active material that has the desired battery performance and is highly practical, at low cost.

[0038] Furthermore, since the amount of the metal salt added is 10 to 25 parts by weight per 100 parts by weight of the black mass, the desired electrode active material can be obtained by simply adding a small amount of the specified metal salt to the black mass and then performing a heat treatment at a temperature of 700 to 900°C for 1 to 2 hours.

[0039] Furthermore, the plurality of metal salts are added to the black mass at an adjusted blending ratio so that when these plurality of metal salts are mixed together to synthesize, one oxide selected from the group consisting of NMC111, NMC433, NMC523, NMC532, NMC622, NMC811, NCA, and lithium-excess NMC compositions can be formed. This makes it possible to obtain novel and useful electrode active materials suitable for a variety of applications at low cost.

[0040] The electrode of the present invention contains the electrode active material produced by the above-described production method, and therefore resources can be recycled efficiently, making it possible to obtain a novel and useful battery electrode at low cost.

[0041] Furthermore, since this electrode active material has a layered rock salt type crystalline structure, the battery reaction due to the insertion and desorption of Li ions proceeds easily due to the two-dimensional diffusion of Li, and the desired lithium ion battery can be obtained.

[0042] The lithium ion battery of the present invention has a positive electrode, a negative electrode, and an electrolyte, and repeats charge and discharge reactions through a battery electrode reaction using lithium ions as a charge carrier. The positive electrode active material that forms the main part of the positive electrode is formed from the electrode active material produced by the above-mentioned production method. Therefore, it is possible to easily obtain, at low cost, a novel and useful lithium ion battery that contributes to the effective recycling of used lithium ion batteries.

[0043] Furthermore, since the negative electrode active material, which is the main component of the negative electrode, is formed from lithium metal, it is possible to obtain a lithium ion battery with a higher energy density than when the negative electrode is formed from a carbon-based material.

[0044] 1 is a schematic cross-sectional view showing one embodiment of a lithium ion battery according to the present invention. It shows secondary electron images of sample number 1 (an example of the present invention), with (a) a magnification of 1000x and (b) a magnification of 5000x. It shows secondary electron images of sample number 2 (black mass), with (a) a magnification of 1000x and (b) a magnification of 5000x. It shows secondary electron images of sample number 4 (reference example sample), with (a) a magnification of 1000x and (b) a magnification of 5000x. It is a profile showing elemental mapping analysis of sample number 1. It is a profile showing elemental mapping analysis of sample number 2. It is a profile showing elemental mapping analysis of sample number 4. It is a profile showing X-ray diffraction spectra of sample numbers 1, 2, and 4. It is a diagram showing an example of temperature dependence of cycle characteristics.

[0045] Next, an embodiment of the present invention will be described in detail.

[0046] An electrode active material according to one embodiment of the present invention is produced by adding a plurality of metal salts containing Li, Ni, Co, and either Mn or Al to black mass obtained by treating used lithium-ion batteries, followed by heat treatment, and then reacting the black mass with the metal salts.

[0047] In this way, electrode active materials can be produced simply by adding a plurality of metal salts, which serve as metal sources for the electrode active material, to black mass and then heat-treating the black mass. This eliminates the need for the laborious process of recovering metal salts, etc. from black mass, and allows for the effective use of used lithium-ion batteries, thereby enabling the production of practical, high-capacity, high-performance electrode active materials at low cost.

[0048] That is, as mentioned in the section on the background art, the materials constituting lithium-ion batteries, particularly the Li, Ni, Co, and Mn constituting the electrode active materials, are all rare metals, and there is a concern that it will become difficult to secure a supply of these metals in the future. Therefore, in recent years, attempts have been made to utilize the "black mass" obtained by processing used lithium-ion batteries, recover useful resources, and use them in the production of new batteries.

[0049] This black mass is a black powder obtained by discharging used lithium-ion batteries, heating and drying them to evaporate the electrolyte, crushing and pulverizing them, extracting and removing unnecessary impurities, and then sieving the resulting material.

[0050] However, although this black mass can be recycled and reused in the production of new batteries by separating and recovering metal salts, which serve as precursors to electrode active materials, processing steps such as extraction and separation are required before the raw materials can be recycled. Because the processing steps are complicated, recycling costs are high, and the efficiency is low, making it less practical.

[0051] Therefore, in this embodiment, although trace amounts of impurities such as C, F, Si, and Al derived from lithium ion batteries are inevitably mixed into the black mass, it also contains large amounts of oxides of Ni, Co, and Mn that constitute the electrode active material. Therefore, a plurality of metal salts containing each of the metal components Li, Ni, Co, and Mn or Al are added to the black mass and heat-treated, thereby causing the black mass to react with the metal salts, thereby producing a new and useful electrode active material.

[0052] The amount of metal salt added is not particularly limited as long as it is small enough to meet the objectives of the invention, namely, cost reduction and resource reuse; for example, 10 to 25 parts by weight per 100 parts by weight of black mass is preferred. That is, if the amount of metal salt added is less than 10 parts by weight per 100 parts by weight of black mass, the black mass content becomes relatively high, and sufficient battery performance, such as cycle characteristics, may not be obtained. On the other hand, if the amount of metal salt added is more than 25 parts by weight per 100 parts by weight of black mass, the amount of metal salt containing rare metals such as Co and Ni added increases, which may lead to increased costs and, as shown in the examples described below, may actually lead to deterioration of cycle characteristics, which is undesirable.

[0053] Furthermore, the compounding ratio of the plurality of metal salts is not particularly limited as long as the metal salts contain Li, Ni, Co, and Mn or Al, but the compounding ratio can be adjusted and added so that a specific lithium-containing metal oxide can be formed when the metal salts are mixed together and heat-treated to synthesize them.

[0054] That is, the metal salts can be added to the black mass in an adjusted blending ratio so that when the metal salts are mixed together and heat-treated to synthesize them, for example, NMC111, NMC433, NMC523, NMC532, NMC622, NMC811, NCA, or a lithium-excess NMC composition can be formed.

[0055] Here, the lithium-excess NMC composition specifically includes Li 1.2 Ni 0.13 Mn 0.54 Co 0.13 O ２, Li 1.06 Ni 0.22 Mn 0.45 Co 0.22 O ２ , Li 1.11 Ni 0.17 Mn 0.50 Co 0.17 O ２ , Li 1.14 Ni 0.13 Mn 0.54 Co 0.13 O ２ , Li 1.17 Ni 0.095 Mn 0.57 Co 0.095 O ２ The following can be mentioned:

[0056] The type of each metal salt is not particularly limited as long as it contains Li, Ni, Co, and Mn or Al. For example, if the Li source is Li, ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, Mn source (CH ３ COO) ２ Mn 4H ２ O, Co source is Co(NO ３ ) ２ ・6H ２ O, AlCl if Al source ３ ・6H ２ Each powder of O can be used.

[0057] The heat treatment temperature is not particularly limited, but is usually preferably in the range of 700°C to 900°C. If the heat treatment temperature is low, below 700°C, sufficient crystallization may not occur, making it difficult to obtain the desired capacity density. On the other hand, if the heat treatment temperature is high, above 900°C, crystallization may proceed excessively, inhibiting the movement of Li ions and resulting in deterioration of cycle characteristics.

[0058] The heat treatment time is not particularly limited, but is preferably about 1 to 2 hours. A heat treatment time of less than 1 hour may result in insufficient crystallization, making it difficult to obtain the desired capacity density. On the other hand, a heat treatment time of more than 2 hours may result in excessive crystallization, inhibiting the movement of Li ions and potentially deteriorating cycle characteristics.

[0059] As will be apparent from the examples described later, this electrode active material has a layered rock-salt crystal structure. That is, metal oxide layers containing Ni, Co, and Mn or Al are formed at regular intervals, and lithium layers are interposed between the metal oxide layers. Li ions in the lithium layers diffuse two-dimensionally, causing insertion and desorption reactions, thereby carrying out charge and discharge.

[0060] Furthermore, Black Mass has Li ２ CO ３ Simply adding a lithium salt such as Ni, Co, and Mn or Al and then heat-treating the material is undesirable because it leads to a significant deterioration in cycle characteristics compared to the case of using black mass alone. In other words, in order to obtain a desired electrode active material, it is considered essential to add a metal salt containing Ni, Co, and Mn or Al and then heat-treat the material to form a metal oxide layer with an appropriately improved crystallinity.

[0061] As described above, according to the method for producing an electrode active material in this embodiment, a plurality of metal salts containing each of the metal components Li, Ni, Co, and Mn or Al are added to black mass obtained by treating used lithium ion batteries, followed by heat treatment, and the black mass and the metal salts are reacted to produce an electrode active material. Therefore, there is no need to recover metal salts or metal components from the black mass as in the conventional method, and used lithium ion batteries can be effectively utilized, and an electrode active material having battery performance sufficient for practical use can be obtained at low cost.

[0062] Next, a lithium ion battery using the electrode active material will be described.

[0063] FIG. 1 is a schematic cross-sectional view showing a lithium ion battery according to the present invention, in which the present electrode active material is used as a positive electrode active material.

[0064] This lithium-ion battery includes a lid-shaped positive electrode current collector 1 made of aluminum or the like and serving as a positive electrode case, and a cylindrical negative electrode current collector 2 made of copper or the like and serving as a negative electrode case. A positive electrode active material layer 3 is formed on one main surface of the positive electrode current collector 1, and the positive electrode current collector 1 and the positive electrode active material layer 3 together constitute a positive electrode 4. A negative electrode active material layer 5 is formed in the center of the bottom of the negative electrode current collector 2, and the negative electrode current collector 2 and the negative electrode active material layer 5 together constitute a negative electrode 6. A separator 7 made of a porous sheet or film such as a microporous membrane, woven fabric, or nonwoven fabric is disposed between the positive electrode active material layer 3 and the negative electrode active material layer 5, and the internal space is filled with an electrolyte 8. The positive electrode current collector 1 and the negative electrode current collector 2 are sealed via a gasket 9.

[0065] The negative electrode active material used in the negative electrode active material layer 5 is not particularly limited, and lithium metal, carbon-based materials such as graphite and graphene, lithium titanate, etc. can be used. However, from the viewpoint of obtaining a high energy density, it is preferable to use lithium metal.

[0066] Next, an example of a method for manufacturing the lithium ion battery will be described in detail.

[0067] First, the positive electrode active material is formed into an electrode shape. For example, the positive electrode active material is mixed with a conductive additive and a binder, and a solvent is added to form a slurry. The slurry is then applied to the positive electrode current collector 1 by any coating method and dried to form the positive electrode active material layer 3 on one main surface of the positive electrode current collector 1, thereby obtaining the positive electrode 4.

[0068] The conductive additive is not particularly limited, and examples thereof include conductive carbon such as graphite, carbon black, and acetylene black, carbon fibers such as carbon nanotubes and carbon nanohorns, and conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene. Two or more types of conductive additives can also be mixed and used.

[0069] The binder is not particularly limited, and various resins such as polyvinylidene fluoride, polyethylene, polyhexafluoropropylene, polytetrafluoroethylene, polyethylene oxide, and carboxymethyl cellulose can be used.

[0070] Furthermore, the solvent is not particularly limited, and examples thereof include basic solvents such as N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylformamide, propylene carbonate, diethyl carbonate, dimethyl carbonate, and γ-butyrolactone; non-aqueous solvents such as acetonitrile, tetrahydrofuran, nitrobenzene, and acetone; protic solvents such as methanol and ethanol; and water.

[0071] The type of organic solvent, the blending ratio of the organic compound to the organic solvent, the type and amount of additives, etc. can be set as desired.

[0072] Next, a negative electrode active material layer 5 is placed at the center of the bottom of a cylindrical negative electrode current collector 2 with a bottom to form a negative electrode 6, and the negative electrode 6 is impregnated with an electrolyte 8 to soak the negative electrode 6 with the electrolyte 8. Further, the positive electrode 4 is impregnated with the electrolyte 8. Furthermore, the separator 7 impregnated with the electrolyte 8 is placed in a negative electrode case, and the electrolyte 8 is then poured into the internal space. Then, a gasket 9 is placed around the periphery, and the negative electrode current collector 2 and the positive electrode current collector 1 are fixed together with a crimping machine or the like to seal the exterior, thereby completing the production of a lithium-ion battery.

[0073] The electrolyte 8 is interposed between the positive electrode 4 and the negative electrode 6, which is the counter electrode, and transports charge carriers between the two electrodes. Examples of such electrolyte 8 that can be used include an electrolyte solution in which an electrolyte salt is dissolved in an organic solvent, a polymer-based electrolyte solution in which a polymer such as polyethylene oxide is added to this, and an ionic liquid-based electrolyte solution in which an electrolyte salt is dissolved in an ionic liquid such as 1-ethyl-3-methylimidazolium tetrafluoroborate.

[0074] Here, the electrolyte salt is, for example, LiPF ６ , LiClO ４ , LiBF ４ , F ２ LiNO４ 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 P.O. ４ , LiCl, (CH ３ CO) ２ Various lithium salts such as Li can be used.

[0075] As the organic solvent, ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, fluoroethylene carbonate, dimethoxyethane, and mixed solvents thereof can be used.

[0076] In addition, a solid electrolyte may be used as the electrolyte. Either an inorganic solid electrolyte or a polymer solid electrolyte may be used. Examples of inorganic solid electrolytes include 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 the polymer-based solid electrolyte include various copolymers such as polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride-ethylene copolymer.

[0077] As described above, the lithium ion battery has the positive electrode 4, the negative electrode 6, and the electrolyte 8, and repeats charge and discharge reactions through a battery electrode reaction using lithium ions as a charge carrier. The positive electrode active material 3, which is the main component of the positive electrode 4, is formed from the electrode active material produced by the above-mentioned production method. Therefore, it is possible to easily obtain, at low cost, a novel and useful lithium ion battery that contributes to the effective recycling of used lithium ion batteries.

[0078] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and scope of the present invention. For example, although a cylindrical lithium-ion battery has been described in this embodiment, the battery shape is not particularly limited, and it can be applied to rectangular, sheet, coin, and other types. Furthermore, the packaging method is not particularly limited, and a metal case, molded resin, aluminum laminate film, and the like may be used.

[0079] Next, examples of the present invention will be described in detail.

[0080] [Sample Preparation] (Sample No. 1) First, black mass manufactured by Kawashima Co., Ltd. was procured. Li was used as a Li source. ２ CO ３ , Ni(NO) as Ni source ３ ) ２ ・6H ２ O, as a Mn source (CH ３ COO) ２ Mn 4H ２ O, Co(NO) as a Co source ３ ) ２ ・6H ２ Each powder of O was prepared.

[0081] The compounding ratio of Li, Ni, Mn, and Co is Li:Ni:Mn:Co=3:1:1:1 in terms of molar ratio when the metal salts are mixed and synthesized. ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, (CH ３ COO) ２ Mn 4H ２ O, and Co(NO３ ) ２ ・6H ２ Each of the metal salts was weighed and mixed in a mortar to obtain a mixture of metal salts.

[0082] Next, 25 parts by weight of the mixture was added to 100 parts by weight of black mass, and the mixture was heat-treated at 800°C for 1 hour, and then allowed to cool to room temperature. The mixture was then sieved using a stainless steel mesh with 75 µm openings, thereby producing a powder sample (electrode active material) of Sample No. 1.

[0083] Next, 2.7 g of the sample was mixed with 6 g of N-methyl-2-pyrrolidone (hereinafter referred to as "NMP") and stirred for 120 seconds using a stirring and defoaming apparatus (Mazerustar, manufactured by Kurabo Industries Ltd.), after which 0.15 g of conductive carbon (EC-600-JD, manufactured by Lion Corporation) as a conductive additive was added thereto, and the mixture was further stirred for 360 seconds using the stirring and defoaming apparatus to obtain a mixed product.

[0084] Next, an NMP solution was prepared by dissolving 5 wt % polyvinylidene fluoride in NMP. 3.0 g of the MNP solution was added to the stirred mixture, and the mixture was stirred for 360 seconds using the stirring and degassing device, followed by 180 seconds, another 360 seconds, and then degassed for 90 seconds to obtain a coating solution.

[0085] Next, the coating solution was applied onto an Al substrate using a doctor blade method to form a coating film with a thickness of 300 μm, and then dried at a temperature of 100° C. for 8 hours. In this way, a positive electrode was produced in which the Al substrate was used as a positive electrode current collector and the above sample was used as a positive electrode active material.

[0086] Next, lithium metal was placed on a Cu substrate, and the Cu substrate was used as a negative electrode current collector, and a negative electrode was fabricated using lithium metal as the main negative electrode active material. A separator made of polypropylene was then interposed between the positive electrode and the negative electrode, and a carbonate-based electrolyte solution was further injected between the positive electrode and the negative electrode, thereby fabricating a flat cell (simple experimental cell) of Sample No. 1.

[0087] This flat cell was charged at a C rate of 0.1 C up to 4.6 V and then discharged down to 2.0 V, and the battery capacity (initial value) was found to be 124.1 mAh / g.

[0088] (Sample No. 2) The black mass manufactured by Kawashima Co., Ltd. used in Sample No. 1 was used as a powder sample for Sample No. 2, and a flat cell for Sample No. 2 was prepared using this powder sample in the same manner and procedure as Sample No. 1.

[0089] When this flat cell was charged and discharged in the same manner and procedure as for sample number 1, the battery capacity (initial value) was 93.7 mAh / g.

[0090] (Sample No. 3) 25 parts by weight of Li per 100 parts by weight of black mass ２ CO ３ A powder sample of sample number 3 was prepared in the same manner and procedure as sample number 1, except that only 1 was added to the black mass.

[0091] Then, using this powder sample, a flat cell of sample number 3 was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 115.8 mAh / g.

[0092] (Sample No. 4) NMC111 (LiNi) manufactured by MTI 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ ) was procured and designated as sample number 4, a powder sample (reference sample).

[0093] Then, using this powder sample, a flat cell of sample number 4 was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 101.2 mAh / g.

[0094] [Sample Evaluation] For each of the powder samples of sample numbers 1, 2, and 4, an SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray Spectrometry) (FlexSEM 1000 II, manufactured by Hitachi High-Technologies Corporation) was used to perform imaging of the sample and elemental mapping analysis, and further, the sample was irradiated with characteristic X-rays (Kα) to measure the X-ray diffraction spectrum.

[0095] 2A and 2B are secondary electron images of sample No. 1 taken at an accelerating voltage of 5.0 kV, with (a) being taken at a magnification of 1000 times and (b) being taken at a magnification of 5000 times.

[0096] FIG. 3 is a secondary electron image of sample No. 2 (black mass) taken using the same method and procedure as sample No. 1, and FIG. 4 is a secondary electron image of sample No. 4 (NMC111) taken using the same method and procedure as sample No. 1.

[0097] That is, as is clear from FIG. 4, sample No. 4 is dispersed almost uniformly as spherical to approximately rectangular aggregates with a particle size of about 1 μm.

[0098] On the other hand, as is clear from FIG. 3, in sample No. 2, fine particles of several μm and aggregates of submicron particles are irregularly dispersed.

[0099] In contrast, sample No. 1 contained a small amount of metal salt mixture, 25 parts by weight, relative to 100 parts by weight of black mass. As shown in FIG. 2, sample No. 1 was found to be in a state closer to sample No. 2 (FIG. 3) than to sample No. 4 (FIG. 4).

[0100] Fig. 5 shows the profile of elemental mapping analysis of sample No. 1, with the horizontal axis representing the accelerating voltage (keV) and the vertical axis representing the count number (a.u.). Table 1 shows the mass fraction (mass%), standard deviation σ (%), and molar concentration (mol%) of each metal component in sample No. 1. In Table 1, element C in Fig. 5 is excluded from the composition elements because it includes the carbon tape used to fix the sample.

[0101]

[0102] 6 is a profile showing the elemental mapping analysis of sample No. 2, where the horizontal axis represents the accelerating voltage (keV) and the vertical axis represents the number of counts (a.u.). Table 2 shows the mass fraction (mass%), standard deviation σ (%), and molar concentration (mol%) of each metal component in sample No. 2. As in Table 1, element C is excluded from the composition elements.

[0103]

[0104] 7 is a profile showing the elemental mapping analysis of sample No. 4, where the horizontal axis represents the accelerating voltage (keV) and the vertical axis represents the number of counts (a.u.). Table 3 shows the mass fraction (mass%), standard deviation σ (%), and molar concentration (mol%) of each metal component in sample No. 4. As in Table 1, element C is excluded from the composition elements.

[0105]

[0106] As shown in Fig. 6 and Table 2, sample No. 2 contains Ni, Mn, and Co as its main components, similar to the electrode active material of the present invention, but it was found that among these components, Ni was the most abundant, followed by Mn, and Co was the least abundant. Furthermore, the standard deviation σ of each detected component was 0.09% or less, and the variation was small, indicating that the electrode active material of the present invention contained F, which is unnecessary for the electrode active material of the present invention, and also contained a small amount of Al.

[0107] On the other hand, as shown in FIG. 7 and Table 3, sample No. 4 contains small amounts of Al and Si components, but the Ni, Mn, and Co components are approximately equal in amount, and the composition formula is generally (LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ ) and found to be blended in the molar ratio shown in Table 1.

[0108] In contrast, as shown in Fig. 5 and Table 1, sample No. 1, like sample No. 2, was found to be composed mainly of Ni, Mn, and Co, with Ni being the most abundant, followed by Mn, and Co being the least abundant. Furthermore, the F component, which was detected in sample No. 2, was not detected.

[0109] That is, since the amount of metal salt mixture added to sample No. 1 was only 25 parts by weight relative to 100 parts by weight of black mass, the results of elemental analysis also showed that it was closer to sample No. 2 (Table 2) than to sample No. 4 (Table 3).

[0110] Since Li is a light element, it could not be detected by SEM-EDX. However, since the purpose of elemental analysis is to confirm the compounding state of the metal oxides, this does not have any particular effect on the sample evaluation.

[0111] FIG. 8 shows the X-ray diffraction spectrum profiles of the powder samples Nos. 1, 2, and 4, with the horizontal axis representing the diffraction angle 2θ (°) and the vertical axis representing the diffraction intensity (a.u.).

[0112] Sample No. 4 is known to have a layered rock salt type crystal structure, and since the profiles of Sample Nos. 1 and 2 are similar to that of Sample No. 4, it is believed that Sample Nos. 1, 2, and 4 all have a layered rock salt type crystal structure, and it has been confirmed that they have a crystal structure suitable for an electrode active material for a lithium ion battery.

[0113] Next, each of the samples Nos. 1 to 4 was charged and discharged 100 times in the voltage range of 2.0 V to 4.6 V to evaluate the cycle characteristics.

[0114] Table 4 shows the measurement results.

[0115]

[0116] Sample No. 2 had a low initial capacity density of 93.7 mAh / g, and after 100 cycles, the capacity density decreased to 23.2 mAh / g. In other words, after 100 charge / discharge cycles, the capacity density decreased to about 25% of the initial value, indicating that sufficient cycle characteristics could not be obtained.

[0117] Sample No. 3 had an initial capacity density of 115.8 mAh / g, which was higher than that of Sample No. 4. However, since the black mass was simply treated with Li added, the deterioration of cycle characteristics became significant after 25 cycles, and the capacity density after 100 cycles was 3.9 mAh / g, which was approximately 3% of the initial value.

[0118] In contrast, sample No. 1 had a high initial capacity density of 124.1 mAh / g, and after 50 cycles the capacity density was 64.7 mAh / g, which was 52% of the initial value. Even after 100 cycles the capacity density was 44.6 mAh / g, which was 36% of the initial value. It was therefore found that sample No. 1 had better cycle characteristics than samples Nos. 2 and 3.

[0119] In Example 2, a plurality of samples were prepared with different amounts of metal salt added, and the properties of each sample were evaluated.

[0120] [Preparation of Samples] (Sample No. 1a) A powder sample of Sample No. 1a was prepared in the same manner and procedure as Sample No. 1, except that 10 parts by weight of the metal salt mixture was added to 100 parts by weight of the black mass.

[0121] Then, using this powder sample, a flat cell of sample number 1a was fabricated in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 121.8 mAh / g.

[0122] (Sample No. 1b) A powder sample of Sample No. 1b was prepared in the same manner and procedure as Sample No. 1, except that 50 parts by weight of the metal salt mixture was added to 100 parts by weight of the black mass.

[0123] Then, using this powder sample, a flat cell of sample number 1b was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 106.4 mAh / g.

[0124] (Sample No. 1c) A powder sample of Sample No. 1c was prepared in the same manner and procedure as Sample No. 1, except that 75 parts by weight of the metal salt mixture was added to 100 parts by weight of the black mass.

[0125] Then, using this powder sample, a flat cell of sample number 1c was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 88.5 mAh / g.

[0126] [Evaluation of Samples] Each of Samples 1a to 1c was charged and discharged 100 times in the voltage range of 2.0 V to 4.6 V, and the cycle characteristics were evaluated.

[0127] The measurement results are shown in Table 5. In addition, Table 5 also lists the cycle characteristics of sample No. 1.

[0128]

[0129] In sample No. 1b, the amount of metal salt mixture added was as high as 50 parts by weight relative to 100 parts by weight of black mass, which not only increased the cost but also showed a capacity density of 29.7 mAh / g after 100 cycles, which was found to be less than 30% of the initial value.

[0130] In sample No. 1c, the amount of metal salt mixture added was 75 parts by weight relative to 100 parts by weight of black mass, which was an even greater excess. As with sample No. 1b, this not only resulted in higher costs, but also in a low initial capacity density of 88.5 mAh / g, and a capacity density of 11.7 mAh / g after 100 cycles, which was found to be 15% or less of the initial value.

[0131] In contrast, sample No. 1a had an added amount of 10 parts by weight of the metal salt mixture relative to 100 parts by weight of the black mass, and therefore had a high initial capacity density of 121.8 mAh / g, and even after 100 cycles the capacity density was 41.8 mAh / g, which was approximately 34% of the initial value, and it was found that good cycle characteristics similar to those of sample No. 1 could be obtained.

[0132] From the above, it was found that the amount of metal salt to be added is not particularly limited, but is preferably 10 to 25 parts by weight per 100 parts by weight of black mass.

[0133] In Example 3, a plurality of samples were prepared by varying the heat treatment temperature, and the properties of each sample were evaluated.

[0134] [Preparation of Samples] (Sample No. 1d) A powder sample of Sample No. 1d was prepared in the same manner and procedure as Sample No. 1, except that the heat treatment temperature was 700°C.

[0135] Then, using this powder sample, a flat cell of sample number 1d was fabricated in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 110.7 mAh / g.

[0136] (Sample No. 1e) A powder sample of sample No. 1e was prepared in the same manner and procedure as sample No. 1, except that the heat treatment temperature was 900°C.

[0137] Then, using this powder sample, a flat cell of sample number 1e was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 112.4 mAh / g.

[0138] (Sample No. 1f) A powder sample of sample No. 1e was prepared in the same manner and procedure as sample No. 1, except that the heat treatment temperature was 1000°C.

[0139] Then, using this powder sample, a flat cell of sample number 1f was fabricated in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 82.1 mAh / g.

[0140] (Sample No. 1g) A powder sample of sample No. 1g was prepared in the same manner and procedure as sample No. 1, except that the heat treatment temperature was 1100°C.

[0141] Then, using this powder sample, a flat cell of sample number 1g was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 82.3 mAh / g.

[0142] [Evaluation of Samples] Each of the samples 1d to 1g was charged and discharged 100 times in the voltage range of 2.0 V to 4.6 V, and the cycle characteristics were evaluated.

[0143] 9 shows the temperature dependence of cycle characteristics, with the horizontal axis representing the number of cycles (cycles) and the vertical axis representing capacity density (mAh / g). In the figure, circles represent the cycle characteristics of sample number 1d (heat treatment temperature: 700°C), squares represent the cycle characteristics of sample number 1e (heat treatment temperature: 900°C), squares represent the cycle characteristics of sample number 1f (heat treatment temperature: 1000°C), and crosses represent the cycle characteristics of sample number 1g (heat treatment temperature: 1100°C). In the figure, circles represent the cycle characteristics of sample number 1 (heat treatment temperature: 800°C).

[0144] 9, Samples 1f and 1g had heat treatment temperatures as high as 1000° C. and 1100° C., respectively, which resulted in low initial battery capacity and significantly deteriorated cycle characteristics, with the characteristics dropping drastically after about 20 cycles. This is thought to be because the heat treatment temperatures were too high, causing excessive crystallization and inhibiting the insertion and desorption reactions of Li ions.

[0145] In contrast, samples 1d and 1e were heat treated at temperatures of 700° C. and 900° C., which are suitable for the progression of crystallization, and it was found that, like sample 1, good cycle characteristics were obtained.

[0146] From the above, it was found that the heat treatment temperature is preferably 700 to 900°C.

[0147] In this Example 4, a plurality of samples were prepared with different heat treatment times, and the properties of each were evaluated.

[0148] [Preparation of Samples] (Sample No. 1h) A powder sample of sample No. 1h was prepared in the same manner and procedure as sample No. 1, except that the heat treatment time was set to 0.5 hours.

[0149] Then, using this powder sample, a flat cell of sample number 1h was prepared using the same method and procedure as sample number 1, and when charging and discharging were performed, the battery capacity (initial value) was 117.6 mAh / g.

[0150] (Sample No. 1i) A powder sample of Sample No. 1i was prepared in the same manner and procedure as Sample No. 1, except that the heat treatment time was set to 1 hour.

[0151] Then, using this powder sample, a flat cell of sample number 1i was produced in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 121.3 mAh / g.

[0152] (Sample No. 1j) A powder sample of sample No. 1j was prepared in the same manner and procedure as sample No. 1, except that the heat treatment time was set to 4 hours.

[0153] Then, using this powder sample, a flat cell of sample number 1j was fabricated in the same manner and procedure as sample number 1, and when charge and discharge were carried out, the battery capacity (initial value) was 109.2 mAh / g.

[0154] [Evaluation of Samples] Each of Samples 1h to 1j was charged and discharged 100 times in the voltage range of 2.0 V to 4.6 V, and the cycle characteristics were evaluated.

[0155] The measurement results are shown in Table 6. In addition, Table 6 also lists the cycle characteristics of sample No. 1.

[0156]

[0157] The capacity density of sample 1h after 100 cycles was 37.4 mAh / g, which was about 32% of the initial value. This is thought to be because the heat treatment time was short (0.5 hours), and crystallization did not proceed sufficiently.

[0158] The capacity density of sample number 1j after 100 cycles was 29.3 mAh / g, which was about 27% of the initial value. This is because the heat treatment time was long, 4.0 hours, which caused excessive crystallization and Li ＋ This is thought to be because the insertion and removal reactions of

[0159] In contrast, sample No. 1i had a heat treatment time of 2 hours, and it was found that it had cycle characteristics substantially similar to those of sample No. 1 (heat treatment time: 1 hour).

[0160] From the above, it was found that the heat treatment time was preferably 1 to 2 hours.

[0161] In Example 5, a plurality of samples were prepared with different compounding ratios of the metal sources, and the properties of each were evaluated.

[0162] [Sample Preparation] (Sample No. 11) As with Sample No. 1, Li was used as the Li source. ２ CO ３ , Ni(NO) as Ni source ３ ) ２ ・6H ２ O, as a Mn source (CH ３ COO) ２ Mn 4H ２ O, Co(NO) as a Co source ３ ) ２ ・6H ２ Powders of Li, Ni, Mn, and Co were prepared. When these metal salts were mixed and synthesized, the compounding ratio of Li, Ni, Mn, and Co was Li:Ni:Mn:Co=1:0.4:0.3:0.3 in terms of molar ratio. ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, (CH ３ COO) ２ Mn 4H２ O, and Co(NO ３ ) ２ ・6H ２ The powder sample of sample number 11 was prepared in the same manner and procedure as sample number 1 except for the above.

[0163] Thereafter, using this powder sample, a flat cell of sample number 11 was produced in the same manner and procedure as sample number 1, and charge and discharge were performed. The battery capacity (initial value) was 116.7 mAh / g (sample name: NMC443).

[0164] (Sample No. 12) When a plurality of metal salts are mixed and synthesized, the compounding ratio of Li, Ni, Mn, and Co is Li:Ni:Mn:Co=1:0.5:0.3:0.2 in terms of molar ratio. ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, (CH ３ COO) ２ Mn 4H ２ O, and Co(NO ３ ) ２ ・6H ２ The powder sample of sample number 12 was prepared in the same manner and procedure as sample number 1, except for the above.

[0165] Thereafter, a flat cell of sample number 12 was produced using this powder sample in the same manner and procedure as sample number 1, and charge and discharge were performed. The battery capacity (initial value) was 119.4 mAh / g (sample name: NMC523).

[0166] (Sample No. 13) When a plurality of metal salts are mixed and synthesized, the compounding ratio of Li, Ni, Mn, and Co is Li:Ni:Mn:Co=1:0.6:0.2:0.2 in terms of molar ratio. ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, (CH ３ COO) ２ Mn 4H２ O, and Co(NO ３ ) ２ ・6H ２ The powder sample of sample number 13 was prepared in the same manner and procedure as sample number 1, except for the above.

[0167] Thereafter, a flat cell of sample number 13 was produced using this powder sample in the same manner and procedure as sample number 1, and charge / discharge was performed, resulting in a battery capacity (initial value) of 126.8 mAh / g (sample name: NMC622).

[0168] (Sample No. 14) When a plurality of metal salts are mixed and synthesized, the compounding ratio of Li, Ni, Mn, and Co is Li:Ni:Mn:Co=1:0.8:0.1:0.1 in terms of molar ratio. ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, (CH ３ COO) ２ Mn 4H ２ O, and Co(NO ３ ) ２ ・6H ２ The powder sample of sample number 14 was prepared in the same manner and procedure as sample number 1, except for the above.

[0169] Thereafter, a flat cell of sample number 14 was produced using this powder sample in the same manner and procedure as sample number 1, and charge / discharge was performed, resulting in a battery capacity (initial value) of 132.8 mAh / g (sample name: NMC811).

[0170] (Sample No. 15) (CH ３ COO) ２ Mn 4H ２ AlCl as an Al source instead of O ３ ・6H ２ Then, Li, Ni, Co, and Al were mixed in a ratio of Li:Ni:Co:Al=1:0.8:0.15:0.05 in terms of molar ratio when the metal salts were mixed and synthesized. ２CO ３ , Ni(NO ３ ) ２ ・6H ２ O, Co(NO ３ ) ２ ・6H ２ O, and AlCl ３ ・6H ２ Sample No. 15 was prepared in the same manner and procedure as Sample No. 1, except that each of the ingredients O was weighed and mixed in a mortar to prepare a mixture of metal salts.

[0171] Thereafter, a flat cell of sample number 15 was produced using this powder sample in the same manner and procedure as sample number 1, and charge / discharge was performed, resulting in a battery capacity (initial value) of 130.6 mAh / g (sample name: NCA).

[0172] (Sample No. 16) The compounding ratio of Li, Ni, Mn, and Co was adjusted so that when a plurality of metal salts were mixed and synthesized, the molar ratio was Li:Ni:Mn:Co=1.2:0.13:0.54:0.13. ２ CO ３ , Ni(NO ３ ) ２ ・6H ２ O, (CH ３ COO) ２ Mn 4H ２ O, and Co(NO ３ ) ２ ・6H ２ The powder sample of sample number 16 was prepared in the same manner and procedure as sample number 1, except for the above.

[0173] Thereafter, using this powder sample, a flat cell of sample number 16 in which the positive electrode active material was formed of a lithium-excess composition was produced in the same manner and procedure as sample number 1, and charge and discharge were performed. The battery capacity (initial value) was 187.6 mAh / g (sample name: LR-NMC).

[0174] (Evaluation of Samples) Each of Samples 11 to 16 was charged and discharged 100 times in the voltage range of 2.0 V to 4.6 V, and the cycle characteristics were evaluated.

[0175] Table 7 shows the measurement results.

[0176]

[0177] As is clear from Table 7, samples 11 to 16 had a capacity of 55.2 to 88.7 mAh / g even after 50 cycles, which was 44 to 51% of the initial battery capacity.

[0178] From the above, it was found that even if the compounding ratio of each metal component is varied depending on the application, a low-cost and highly practical lithium-ion battery can be obtained.

[0179] By adding a specific metal salt to black mass obtained from used lithium ion batteries, a new and useful electrode active material is produced using black mass without the need for the effort of recovering metal salts or metal materials.

[0180] 3 Positive electrode active material (electrode active material) 4 Positive electrode 5 Negative electrode active material 6 Negative electrode 8 Electrolyte solution (electrolyte)

Claims

1. A method for producing an electrode active material, comprising the steps of: treating used lithium ion batteries to obtain black mass; adding a plurality of metal salts each containing the metal components Li, Ni, Co, and Mn or Al; subjecting the black mass to a heat treatment; and reacting the black mass with the metal salts to produce an electrode active material.

2. The method for producing an electrode active material according to claim 1, wherein the amount of said metal salt added is 10 to 25 parts by weight per 100 parts by weight of said black mass.

3. The method for producing an electrode active material according to claim 1 or 2, characterized in that the heat treatment is carried out at a temperature of 700 to 900°C.

4. The method for producing an electrode active material according to claim 1 or 2, characterized in that the heat treatment is carried out for 1 to 2 hours.

5. The above-mentioned multiple metal salts are mixed together to synthesize LiNi 1 / 3 Mn 1 / 3 Co 1 / 3 O ２ , LiNi 0.4 Mn 0.3 Co 0.3 O ２ , LiNi 0.5 Mn 0.3 Co 0.2 O ２ , LiNi 0.5 Mn 0.2 Co 0.3 O ２ , LiNi 0.6 Mn 0.2 Co 0.2 O ２ , LiNi 0.8 Mn 0.1 Co 0.1 O ２ , LiNi 0.8 Co 0.15 A 0.05 O ２ and the general formula Li 1＋ｘ Ni 2 / （3+3ｙ） Mn 2x / （3+3ｙ） Co 2 / （3+3ｙ） O ２ 3. The method for producing an electrode active material according to claim 1, wherein the compounding ratio is adjusted so that one oxide selected from the group of lithium-rich compositions represented by the formula: (where x>0, y is a positive integer) can be formed by adding the compound to the black mass.

6. An electrode comprising an electrode active material produced by the method according to claim 1 or 2.

7. The electrode according to claim 6, wherein the electrode active material has a layered rock salt type crystal structure.

8. A lithium ion battery having a positive electrode, a negative electrode, and an electrolyte, and repeating charge and discharge reactions through battery electrode reactions using lithium ions as charge carriers, wherein the positive electrode active material that constitutes the main component of the positive electrode is formed from an electrode active material produced by the production method described in claim 1 or 2.

9. The lithium ion battery according to claim 8, wherein the main active material of the negative electrode is formed of lithium metal.

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