Recycling method and electrode active material

Abstract

To provide a recycling method capable of recycling a battery or / and a battery material containing an oxide electrode active material, and the electrode active material.SOLUTION: According to one embodiment, there is provided a recycling method including a first step of obtaining a first material containing an oxide electrode active material from a battery and / or a battery material containing the oxide electrode active material, a second step of obtaining a slurry by dispersing the first material in a solvent, a third step of obtaining a second material containing the oxide electrode active material by adding an organic substance to the slurry, and a fourth step of obtaining a third material containing the oxide electrode active material from the second material by heat treatment.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to a recycling method and an electrode active material. [Background technology]

[0002] Lithium-ion secondary batteries use lithium-containing metal oxides as the positive electrode active material and carbon as the negative electrode. Demand for lithium-ion secondary batteries is expected to continue to grow, and recycling of each component used in lithium-ion secondary batteries will be necessary. However, there has been little research into recycling the negative electrode, and research and development is primarily focused on recycling the positive electrode.

[0003] In recent years, development of lithium-ion secondary batteries with anodes containing lithium titanate or niobium titanium oxide, which use oxide electrode active materials, has been progressing. In order to increase the recycling rate of these lithium-ion secondary batteries, it is necessary to realize the recycling of anodes containing oxide electrode active materials that use titanium or niobium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-130474 Summary of the Invention [Problem to be solved by the invention]

[0005] The problem to be solved by the present invention is to provide a recycling method and electrode active material that can recycle batteries and / or battery materials that include an oxide electrode active material. [Means for solving the problem]

[0006] According to an embodiment, a recycling method is provided, which includes: a first step of obtaining a first material containing an oxide electrode active material from a battery and / or battery material containing the oxide electrode active material; a second step of obtaining a slurry by dispersing the first material in a solvent; a third step of obtaining a second material containing the oxide electrode active material by adding an organic substance to the slurry; and a fourth step of obtaining a third material containing the oxide electrode active material from the second material by heat treatment. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a flowchart showing an example of a recycling method according to an embodiment. [Figure 2] 10 is a flowchart showing a modified example of the recycling method according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the following description, components that perform the same or similar functions are designated by the same reference numerals throughout the drawings, and redundant description will be omitted. Each drawing is a schematic diagram for explaining and facilitating understanding of the embodiments, and the shapes, dimensions, ratios, etc. may differ from those of an actual device. However, these may be appropriately modified in design, taking into consideration the following description and known techniques.

[0009] The battery used in this specification is, for example, a secondary battery, such as a nickel-metal hydride battery, a sodium ion battery, a lithium ion battery, etc. Hereinafter, the battery will be described as a lithium ion secondary battery.

[0010] When a lithium-ion secondary battery is charged and discharged, lithium ions are inserted into and extracted from the electrode active material in the lithium-ion secondary battery. Repeated cycles of this process cause the electrode active material to deteriorate due to dissolution or changes in its crystalline structure, resulting in a decline in the performance of the lithium-ion secondary battery. As the deterioration of a lithium-ion secondary battery progresses, the electrode active material cannot be reused as is, and the lithium-ion secondary battery must be discarded. Furthermore, during the battery manufacturing process, materials that do not meet specifications, such as defective products and surplus materials, that do not make it into finished products are discarded because it is difficult to obtain electrode active material from the processed state. The present invention focuses on this issue and devise a recycling method for recovering electrode active material from lithium-ion secondary batteries or battery materials and making it reusable.

[0011] (First embodiment) A recycling method according to a first embodiment will be described with reference to FIG. 1. FIG. 1 is a flowchart showing an example of the flow of the recycling method according to the embodiment. Note that this flowchart is merely an example, and the order of processing is not limited as long as the required processing results can be obtained. The same applies to the subsequent flowcharts. The recycling method according to the embodiment includes a first step of obtaining a first material containing an oxide electrode active material from a battery and / or battery material containing the oxide electrode active material, a second step of dispersing the first material in a solvent to obtain a slurry, a third step of adding an organic substance to the slurry to obtain a second material containing the oxide electrode active material, and a fourth step of obtaining a third material containing the oxide electrode active material from the second material by heat treatment. The recycling method according to the embodiment can be divided into, for example, a step (S1) of preparing a battery and / or battery materials, a step (S2) of obtaining a residue from the battery by heat treatment or the like, a step (S3) of obtaining a first material (mixed powder) by classification, a step (S4) of dispersing the first material in water to obtain a slurry, a step (S5-1) of adding an organic substance to obtain a second material containing an oxide electrode active material, and a step (S6-1) of heat treating the second material to obtain a third material (oxide electrode active material) having a carbon coating.

[0012] Regarding the step (S1) of preparing a battery or / and battery material S1 is the process of preparing batteries and / or battery materials to be recycled. The use status of the batteries does not matter. The batteries are not limited to those discarded after use, but may also be those stored or discarded unused due to reasons such as non-conformity. They may also include semi-finished battery materials in the intermediate stages of the battery manufacturing process or battery materials discarded during the manufacturing process. The battery materials described here are materials containing an oxide electrode active material and at least one other material. Batteries to be recycled need only contain an oxide electrode active material. They may be pre-processed by removing the exterior materials, disassembling the battery, or separating only the electrodes from the battery. Furthermore, the electrodes may be separated into positive and negative electrodes, resulting in only the positive electrode or only the negative electrode. Separating the oxide electrode active material from components other than the oxide electrode active material, such as exterior materials, in S1 can shorten the time required for each step from S2 onward.

[0013] The battery includes a negative electrode, a positive electrode, and an electrolyte. The battery may further include a separator disposed between the positive electrode and the negative electrode. The negative electrode, the positive electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly. The electrode active material according to the embodiment is preferably a negative electrode active material.

[0014] The negative electrode includes a negative electrode active material-containing layer and a current collector. The negative electrode active material-containing layer can be laminated or formed on one or both sides of the current collector. The negative electrode active material-containing layer can include a negative electrode active material and, optionally, a conductive agent and a binder.

[0015] The negative electrode active material includes an oxide electrode active material. Hereinafter, a negative electrode active material including an oxide electrode active material will be referred to as an oxide electrode active material. The oxide electrode active material includes titanium or niobium, such as a titanium-containing oxide. Examples of titanium-containing oxides include lithium titanium oxide, monoclinic (brookite) titanium dioxide (TiO2(B)), anatase titanium dioxide, rutile titanium dioxide, niobium pentoxide (Nb2O5), hollandite titanium composite oxide, orthorhombic titanium-containing composite oxide, niobium titanium oxide, and niobium-containing composite oxide. The oxide electrode active material is preferably an oxide electrode active material that is substantially free of lithium, such as niobium titanium oxide or a niobium-containing composite oxide. Niobium titanium oxide and niobium-containing composite oxides do not change in properties even when immersed in water for a long period of time, and have excellent process adaptability. Furthermore, oxide electrode active materials that are substantially free of lithium do not require re-firing for activation, simplifying the process and allowing the carbon coating formed in the process described below to be maintained. Hereinafter, the oxide electrode active material will be described as an oxide electrode active material that does not substantially contain lithium.

[0016] Here, an oxide electrode active material that is substantially free of lithium refers to an oxide electrode active material that does not contain lithium in its composition. For example, in a lithium-ion secondary battery, lithium ions may not be completely released from the oxide electrode active material even in a fully discharged state. Therefore, in an oxide electrode active material obtained by dismantling a used lithium-ion secondary battery, lithium can be detected even if it is not included in the composition. Therefore, an oxide electrode active material that is substantially free of lithium is an oxide electrode active material that does not contain lithium or a lithium compound in its composition. Therefore, if lithium is detected in an oxide electrode active material that is free of lithium and obtained from a used lithium-ion secondary battery, it is acceptable and is considered to be an oxide electrode active material that is substantially free of lithium.

[0017] The composition of the oxide electrode active material can be analyzed using, for example, ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). An oxide electrode active material that is substantially free of lithium refers to an oxide electrode active material in a fully discharged state (SOC 0%) in which the molar ratio of lithium to any metal element other than lithium is 1 / 20 or less.

[0018] The oxide electrode active material may be one or more types. The oxide electrode active material may be in the form of particles.

[0019] Examples of lithium titanium oxides include lithium titanate having a ramsdellite structure (e.g., Li 2+y Ti3O7, 0≦y≦3), lithium titanates with spinel structure (e.g., Li 4+x Ti5O1, 0≦x≦3).

[0020] Examples of niobium titanium oxide include monoclinic niobium titanium oxide, orthorhombic niobium titanium oxide, and tetragonal niobium titanium oxide. Monoclinic niobium titanium oxide has the characteristics of a highly stable crystal structure, excellent resistance to water, acid, and alkali, and high density. Examples of monoclinic niobium titanium oxide include Li x Ti 1-y M1 y Nb 2-z M2 z O 7+δ Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3. Specific examples of monoclinic niobium titanium oxides include Li x Examples include Nb2TiO7 (0≦x≦5). x The density of Nb2TiO7 is 4.34g / cm 3 is.

[0021] Another example of monoclinic niobium titanium oxide is Li x Ti 1-y M3 y+z Nb 2-z O 7-δ Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. The subscripts in the composition formula are 0≦x≦5, 0≦y<1, 0≦z<2, and −0.3≦δ≦0.3.

[0022] Examples of monoclinic or orthorhombic niobium titanium oxides include Li a Ti b Nb2W c O 2b+3c+5+δ The subscripts in the composition formula are 0≦a≦b+3c+4, 0 <b<2、0<c<2、1.9b+2.85c+4.75≦δ≦2.1b+3.15c+5.25である。

[0023] An example of tetragonal niobium titanium oxide is Li a Ti b Nb 2-2d M c+2d O 2b+5+3c Examples of the compound include compounds represented by the formula: M is any one selected from the group consisting of W and Mo. The subscripts in the composition formula are 0≦a≦b+4+3c, 0 <b<2-2d、0<c<2-4dである。

[0024] The niobium titanium oxide may contain unavoidable impurities, such as K, Na, Si, and P. The niobium titanium oxide may contain lithium ions.

[0025] An example of a niobium-containing composite oxide is Zn2Nb 34 O 87 and Cu2Nb 34 O 87 or compounds in which Zn or Cu is substituted with, for example, Cr, Ti, Fe, Al, etc. a M2 2-a M3b Nb 34-b O 87-c-d Q d Examples of compounds include compounds represented by the formula: where M1 is at least one selected from Mg, Ca, Sr, Y, La, Ce, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, and mixtures thereof. M2 is different from M1 and is Zn or Cu. M3 is at least one selected from Mg, Ca, Sr, Y, La, Ce, Ti, Zr, Hf, V, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Zn, Cd, B, Al, Ga, In, Si, Ge, Sn, Pb, P, Sb, Bi, and mixtures thereof. Q is at least one selected from F, Cl, Br, I, N, S, Se, and mixtures thereof. The subscripts in the formula are 0≦a<1.0, 0≦b≦3.4, −0.5≦c≦4.35, and 0≦d≦4.35. When one or more of a, b, c, and d is not equal to 0, and a, b, and d are 0, then c is greater than 0.

[0026] Another example of a niobium-containing complex oxide is M1 x M2 1-x Nb y O z Also included are compounds represented by the formula: where M1 is at least one selected from Ti, Mg, V, Cr, W, Zr, Mo, Cu, Fe, Ga, Ge, Ca, K, Ni, Co, Al, Sn, Mn, Ce, Te, Se, Si, Sb, Y, La, Hf, Ta, Re, Zn, In, and Cd. M2 is different from M1 and is at least one selected from Mg, V, Cr, W, Zr, Mo, Cu, Ga, Ge, Ca, K, Ni, Co, Al, Sn, Mn, Ce, Sb, Y, La, Hf, Ta, Zn, In, and Cd. Each subscript in the composition formula is 0. <x<0.5、0.5≦y≦49、4≦z≦124である。

[0027] Other examples of niobium-containing composite oxides include compounds containing Mo, Nb, and at least one element M selected from the group consisting of Ti, V, Ta, Fe, Co, Mn, Ni, Bi, Sb, As, P, Cr, W, B, Na, K, Mg, Al, Ca, Y, and Si.

[0028] The conductive agent is blended to improve current collection performance and reduce contact resistance between the negative electrode active material and the current collector. Examples of conductive agents include vapor-grown carbon fiber (VGCF), carbon nanotubes, carbon black such as acetylene black, and carbonaceous materials such as graphite. One of these may be used as the conductive agent, or two or more may be used in combination. Alternatively, instead of using a conductive agent, the surface of the negative electrode active material particles may be coated with carbon or an electronically conductive inorganic material.

[0029] The binder fills the gaps in the negative electrode active material and can bind the negative electrode active material and the current collector. The binder is preferably a hydrophilic binder that is water-soluble or water-dispersible, such as an emulsion. Examples of hydrophilic binders include polyacrylic acid compounds, styrene butadiene rubber, carboxymethyl cellulose (CMC), and salts of CMC. One of these may be used as the binder, or two or more may be used in combination as the binder.

[0030] The mixing ratios of the negative electrode active material, the conductive agent, and the binder in the negative electrode active material-containing layer can be, for example, 68% by mass or more and 96% by mass or less, 2% by mass or more and 30% by mass or less, and 2% by mass or more and 30% by mass or less, respectively.

[0031] The current collector is made of a material that is electrochemically stable at the potential at which lithium is inserted into and extracted from the negative electrode active material. Examples of the current collector include copper, nickel, stainless steel, aluminum, and aluminum alloys. The thickness of the current collector is, for example, 5 μm to 20 μm.

[0032] The current collector can include a portion on its surface where the negative electrode active material-containing layer is not formed. This portion functions as a current collecting tab.

[0033] The positive electrode includes a positive electrode active material-containing layer and a current collector. The positive electrode active material-containing layer can be laminated or formed on one or both sides of the current collector. The positive electrode active material-containing layer can include a positive electrode active material, and optionally a conductive agent and a binder. The current collector, the conductive agent, and the binder can be the same as those used for the negative electrode.

[0034] For the positive electrode active material, for example, an oxide or a sulfide can be used. The positive electrode may contain one type of compound alone or a combination of two or more types of compounds as the positive electrode active material. Examples of the oxide and the sulfide include compounds into which lithium or lithium ions can be inserted and desorbed. The type of the positive electrode active material may include one type or two or more types. Note that, depending on the battery in question, the aforementioned negative electrode active material may be included in the positive electrode active material.

[0035] Examples of such compounds include, for example, manganese dioxide (MnO2), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li x Mn2O4 or Li x MnO2; 0 < x ≦ 1), lithium nickel composite oxide (for example, Li x NiO2; 0 < x ≦ 1), lithium cobalt composite oxide (for example, Li x CoO2; 0 < x ≦ 1), lithium nickel cobalt composite oxide (for example, Li x Ni 1-y Co y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese cobalt composite oxide (for example, Li x Mn y Co 1-y O2; 0 < x ≦ 1, 0 < y < 1), lithium manganese nickel composite oxide having a spinel structure (for example, Li x Mn 2-y Ni yO4; where 0 < x ≤ 1 and 0 < y < 2), a lithium phosphate oxide having an olivine structure (e.g., Li x FePO4; where 0 < x ≤ 1, Li x Fe 1-y Mn y PO4; where 0 < x ≤ 1 and 0 < y ≤ 1, Li x CoPO4; where 0 < x ≤ 1), iron sulfate (Fe2(SO4)3), vanadium oxide (e.g., V2O5), and lithium nickel cobalt manganese composite oxide (Li x Ni 1-y-z Co y Mn z O2; where 0 < x ≤ 1, 0 < y < 1, 0 < z < 1, and y + z < 1) is included.

[0036] The electrolyte can use, for example, a liquid non-aqueous electrolyte or a gel non-aqueous electrolyte. The liquid non-aqueous electrolyte is prepared by dissolving an electrolyte salt as a solute in an organic solvent.

[0037] The separator is formed from, for example, a porous film containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), or a synthetic resin non-woven fabric. From the perspective of safety, it is preferable to use a porous film formed from polyethylene or polypropylene. This is because these porous films can melt at a certain temperature and block the current.

[0038] The battery may further include an exterior member that houses the electrode group and the electrolyte. The exterior member may be, for example, a container made of a laminate film or a metal container. The thickness of the laminate film is, for example, 0.5 mm or less, preferably 0.2 mm or less. The laminate film may be a multilayer film containing multiple resin layers and metal layers interposed between the resin layers. The resin layers may include, for example, polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET). The metal layers are preferably made of aluminum foil or aluminum alloy foil to reduce weight. The laminate film may be molded into the shape of the exterior member by sealing it by heat fusion.

[0039] The thickness of the wall of the metal container is, for example, 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less.

[0040] The metal container is made of, for example, aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. If the aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 1% by mass or less.

[0041] The shape of the exterior member is not particularly limited. The shape of the exterior member may be, for example, flat (thin), rectangular, cylindrical, coin-shaped, or button-shaped. The exterior member can be appropriately selected depending on the battery dimensions and the intended use of the battery.

[0042] The battery may further include a negative electrode terminal electrically connected to the negative electrode and a positive electrode terminal electrically connected to the positive electrode. The negative electrode terminal may be formed from a material that is electrochemically stable at the lithium insertion / extraction potential of the negative electrode active material and has electrical conductivity. Specific examples of the material for the negative electrode terminal include copper, nickel, stainless steel, aluminum, and aluminum alloys containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0043] The positive electrode terminal can be formed from a material that is electrically stable and conductive in a potential range of 3 V to 4.5 V relative to the redox potential of lithium (vs. lithium / lithium ions). Examples of materials for the positive electrode terminal include aluminum and aluminum alloys containing at least one element selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0044] Regarding the process (S2) of obtaining residue by heat treatment of the battery S2 is a step in which the battery prepared in S1 is subjected to a heat treatment or the like to obtain a residue. The heat treatment is carried out in an apparatus such as a batch furnace, an atmospheric furnace, a carbonization furnace, a tunnel kiln, a shuttle kiln, or a rotary kiln. The heat treatment can remove organic substances such as electrolytes from the battery. Examples of organic substances include organic solvents, carbon materials such as conductive agents, and binders. If the current collectors can be separated without the heat treatment, the heat treatment is not essential. However, the heat treatment is preferable because it can avoid environmental pollution and danger caused by the organic substances and facilitate the separation of the current collectors from the positive and negative electrodes.

[0045] The heat treatment can be performed, for example, in air. The heat treatment temperature can be in the range of 300°C to 900°C. The heat treatment temperature range is preferably 350°C to 600°C, more preferably 350°C to 450°C. By performing the heat treatment at a temperature below the melting point of the aluminum used as the current collector, the aluminum pieces are included in the residue without changing in size. This has the advantage of facilitating separation of the aluminum pieces from other residue in subsequent processes. The treatment time can be, for example, in the range of 15 minutes to 10 hours. If the heat treatment temperature is low or the heat treatment time is short, organic matter may remain in the battery without being removed. On the other hand, if the heat treatment temperature is high or the heat treatment time is long, the metal material, such as the current collector, may melt, making it difficult to separate the metal material from the active material-containing layer. After the heat treatment, the battery may be cooled as needed. Cooling can be performed by, for example, air cooling or water cooling. After this, the residue may be obtained by, for example, crushing or cutting. The residue is mainly inorganic and is composed of a mixture of an exterior member such as aluminum, a current collector such as copper or aluminum foil, and powders of the positive electrode active material and the negative electrode active material. When the exterior member is large, it is preferable to coarsely crush it and then classify it. For example, it can be crushed using a shredder, a cutting machine, a cutter, or the like.

[0046] Regarding the step (S3) of obtaining the first material (mixed powder) by classification S3 is a step in which the residue obtained in S2 is classified to obtain a first material (mixed powder) containing an oxide electrode active material. Classification can be performed using, for example, a sieve or an air sorter. Upon completion of this step, a mixed powder is obtained. The mixed powder mainly contains a positive electrode active material and a negative electrode active material. Depending on the firing temperature and conditions, the mixed powder may contain carbon as a conductive agent.

[0047] Regarding the step (S4) of dispersing the first material in water to obtain a slurry S4 is a step in which the mixed powder obtained in S3 is dispersed in a solvent to obtain a slurry. The solvent is, for example, water. Hereinafter, the description will be made assuming that the solvent is water. The mixed powder can be dispersed in water, for example, using a mixer equipped with stirring blades. The amount of mixed powder mixed in water is, for example, 10 g to 1000 g / L. By dispersing the mixed powder in water, water-soluble impurities (e.g., electrolyte) mixed in the mixed powder can be removed, and the active material / foil can be separated by utilizing the difference in sedimentation rate. In addition to dispersing the mixed powder in water, an organic substance, which will be described later, can also be added to the water.

[0048] If necessary, the pH of the water may be adjusted. For example, if the water is acidic, the positive electrode active material becomes hydrophilic. This facilitates separation from the oxide electrode active material. After this process is completed, a slurry is obtained.

[0049] Regarding the step (S5-1) of obtaining a second material containing an oxide electrode active material by adding an organic substance S5-1 is a step in which the oxide electrode active material is separated from the slurry obtained in S4 to obtain a second material containing the oxide electrode active material. This separation is performed using an organic substance and can be carried out by flotation or coagulation sedimentation.

[0050] The organic substance added here is, for example, an organic coating component, which can adhere to the surface of the oxide electrode active material. Hereinafter, the organic substance will be described as the organic coating component. The organic coating component is used for purposes such as particle dispersion, aggregation, and cleaning, and contributes to improving the purity and recovery rate of the active material. Examples include separation of the active material by flotation, recovery of particles by coagulation precipitation, and removal of impurities on the surface of the active material using a surfactant. The organic coating component is, for example, a surfactant or oil used as a flotation agent in the flotation method described below, or a coagulating polymer in the coagulation precipitation method.

[0051] During the flotation process, a flotation agent is added to water to coat the surface of the active material. During the flotation process, the flotation agent adsorbs to the surface of the oxide electrode active material to adjust its hydrophilicity / hydrophobicity, or adheres to the surface of the oxide electrode active material along with air bubbles in the water, causing it to float to the water surface. This allows the oxide electrode active material to be separated from other substances. Examples of flotation agents include starch, polyvinyl alcohol, aromatic alcohols, aliphatic alcohols, sesquiterpene alcohols, terpineol, cresylic acid, ethyl xanthate, amyl xanthate, kerosene, creosote, coal tar, anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants. The concentration of the flotation agent added is, for example, 0.5 mg to 1000 mg / kg of the mixed powder. Apparatuses for implementing the flotation process include, for example, Agitair-type flotation separators and Denver-A-type flotation separators. Although it depends on the combination of the negative electrode active material and the positive electrode active material and the flotation agent used, the negative electrode active material containing the oxide electrode active material can be recovered at the top of the device together with the bubbles, or can settle and be recovered from the bottom of the device. In order to carbonize the flotation agent attached to the surface of the active material in the subsequent process, it is preferable to use a flotation agent that makes the surface hydrophobic and recovers it at the top together with the bubbles, as this increases the amount of carbon on the surface of the active material.

[0052] During coagulation precipitation, a coagulating polymer is added to water to coat the surface of the active material. After adhering to the surface of the active material, the coagulating polymer promotes coagulation of the active material, resulting in coarsening and sedimentation, allowing it to be separated from the water. This allows the active material to be separated from components dissolved in the water and other substances that are difficult to coagulate, thereby improving the purity and recovery rate of the active material. Examples of coagulating polymers used in coagulation precipitation include nonionic polymer coagulants, cationic polymer coagulants, and anionic polymer coagulants, such as polyacrylamide, sodium polyacrylate, polymethacrylate, polyacrylic acid ester, sodium polyacrylate, sodium polymethacrylate, and mixtures thereof. The concentration of the coagulant added is, for example, 1 to 100 ppm by mass in water.

[0053] Regarding the step (S6-1) of heat-treating the second material to obtain a third material (oxide electrode active material) having a carbon coating, S6-1 is a step in which the second material obtained in S5-1 is heat-treated to obtain a third material containing an oxide electrode active material having a carbon coating on its surface. The carbon coating can be obtained by heat-treating the organic coating component added in S5-1. The heat treatment can be performed in the same equipment as in S2.

[0054] The carbon coating can be formed, for example, by firing the oxide electrode active material at 350°C to 900°C under pressurized steam or an inert gas atmosphere. Alternatively, the carbon coating can be formed on the surface in air by adjusting the amount of gas and the amount of oxide electrode active material raw material added. Upon completion of this process, a third material containing an oxide electrode active material with a carbon coating can be obtained. The third material is substantially identical to the oxide electrode active material contained in the battery or / and battery material in S1, except for the presence of the carbon coating. "Substantially identical" means that there is essentially no difference. Therefore, the third material obtained in this manner can be used as a recycled electrode active material. The third material can be reused, for example, as an active material for lithium-ion secondary batteries. The conductive carbon coating on the surface of the third material prevents performance degradation and provides excellent recyclability.

[0055] (Second embodiment) In the second embodiment, both the organic coating component and the inorganic coating component are added in step S5-1 of the first embodiment.

[0056] The recycling method according to the embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing a modified example of the flow of the recycling method according to the embodiment. Since the method is the same as Fig. 1 except that an inorganic coating component is newly added in S5-2 and a third material containing an oxide electrode active material having a carbon coating and an inorganic oxide coating is obtained in S6-2, only S5-2 and S6-2 will be described. Since S1 to S4 are the same as those in the first embodiment, their description will be omitted.

[0057] S5-2 is a step in which organic and inorganic coating components are added to obtain a second material containing an oxide electrode active material. The organic coating components can be the same as those described above. Examples of inorganic coating components include aluminum sulfate (aluminum sulfate) and polyaluminum chloride (PAC), which adhere to the active material surface to promote aggregation of the active material and facilitate separation from the water. Aluminum sulfate and polyaluminum chloride can be used simultaneously. It is desirable to use either aluminum sulfate or polyaluminum chloride depending on the optimal pH of each inorganic coating component. The concentration of these inorganic coating components added is, for example, 1 to 1,000 ppm by mass in water. The order of addition of the inorganic and organic coating components is not particularly specified, but it is preferable to add the organic coating component after the inorganic coating component. The inorganic and organic coating components become an inorganic oxide film and a carbon film, respectively, during the heat treatment step S6-2. Applying a conductive carbon film to the outermost layer improves the maintenance of the conductive path.

[0058] S6-2 is a process in which the second material obtained in S5-2 is heat-treated to obtain a third material containing an oxide electrode active material having a carbon coating and an inorganic oxide coating on its surface. The third material is substantially the same as the oxide electrode active material contained in the battery or / and battery material in S1, except that it does not have a carbon coating and has an inorganic oxide coating. Therefore, the third material can be used as a recycled electrode active material. By coating part of the surface of an oxide electrode active material with an inorganic oxide coating, the contact area with the electrolyte is reduced, which has the effect of suppressing side reactions such as decomposition of the electrolyte and suppressing gas generation.

[0059] (Third embodiment) The regenerated electrode active material in the third embodiment is obtained by the recycling method of the first or second embodiment. The electrode active material obtained by the recycling method of the first or second embodiment can also be called a regenerated electrode active material. The electrode active material in this embodiment is the third material in the first and second embodiments. The electrode active material obtained by the recycling method of the first embodiment has a carbon coating on at least a portion thereof. Furthermore, the electrode active material obtained by the recycling method of the second embodiment has an aluminum compound coating on at least a portion thereof.

[0060] Example 1 Niobium titanium oxide was recycled using the recycling method of the first embodiment shown in Figure 1 for negative electrodes generated during the battery manufacturing process. First, in S1, a negative electrode generated during the manufacturing process was prepared. This electrode was a waste negative electrode material without any mixed positive electrodes or electrolyte. The negative electrode was prepared by coating an aluminum current collector foil with a mixture consisting of 80% by mass of niobium titanium oxide (Nb2TiO7), 10% by mass of acetylene black as a conductive agent, and 10% by mass of CMC as a binder, together with an aqueous solvent, followed by drying and pressing. Next, in S2, the resulting foil was cut into several centimeters and placed in an electric furnace at 450°C and fired for 60 minutes in air to remove organic matter contained in the negative electrode, thereby obtaining a residue. In S3, the resulting residue was sieved to separate a mixed powder (first material) containing aluminum foil and oxide electrode active material. In S4, to remove the fine aluminum foil contained in the mixed powder, the mixed powder was dispersed in water at a weight ratio of 10 wt% to obtain a slurry. In S5-1, polyoxyethylene alkyl ether, a nonionic coagulation polymer, was added to the slurry obtained in S4 as an organic coating component to a concentration of 10 mass ppm in water, coating the surface of the niobium titanium oxide in the mixed powder. The niobium titanium oxide then coagulated and settled. At this time, the aluminum foil was removed by utilizing the difference in sedimentation velocity with the aluminum foil, obtaining a second material containing niobium titanium oxide. In S6-1, the second material was fired in an electric furnace in a nitrogen atmosphere at 650°C for 1 hour to obtain niobium titanium oxide powder with carbon attached to the surface.

[0061] Example 2 A slurry containing a first material was obtained from a negative electrode produced during a battery manufacturing process in the same manner as in Example 1 up to step (S4). In S4, a foaming agent primarily composed of terpineol was added to water at 50 mass ppm as an organic coating component, coating the surface of the niobium titanium oxide in the mixed powder. Fine bubbles were then introduced while gently mixing, causing the aluminum foil to rise and separate with the bubbles, yielding a slurry containing niobium titanium oxide. In S5-1, the obtained slurry was allowed to stand, allowing the niobium titanium oxide to settle, yielding a second material containing niobium titanium oxide. In S-1, the obtained second material was fired in an electric furnace in a nitrogen atmosphere at 650°C for 1 hour, yielding a niobium titanium oxide powder with carbon attached to its surface.

[0062] Example 3 Niobium titanium oxide was recycled using the recycling method of the first embodiment shown in Figure 1 for a battery (hereinafter referred to as the treated battery) equipped with a niobium titanium oxide electrode as the negative electrode and using a metal can as the exterior material. The negative electrode had the same configuration as in Example 1. The battery also contained cyclic carbonate and lithium hexafluorophosphate (LiPF6) as the electrolyte. In S1, the treated battery was disassembled, and the negative electrode was removed. The battery was then dried in a draft to remove most of the electrolyte. In S2, the battery was cut into pieces of several centimeters and placed in an electric furnace at 450°C and fired for 60 minutes in air to remove organic matter contained in the negative electrode, thereby obtaining a residue. In S3, the residue was sieved to separate a mixed powder (first material) containing aluminum foil and oxide electrode active material. In S4, to remove fine aluminum foil and fluorine and phosphorus compounds derived from the electrolyte contained in the resulting mixed powder, the mixed powder was dispersed in water at a weight ratio of 10 wt% to obtain a slurry. In S5-1, a nonionic coagulating polymer, polyoxyethylene alkyl ether, was added to the resulting slurry as an organic coating component to a concentration of 10 ppm by mass in water, coating the surface of the niobium titanium oxide in the mixed powder. The niobium titanium oxide then coagulated and settled. The aluminum foil was removed by utilizing the difference in sedimentation velocity with the aluminum foil, and the fluorine and phosphorus compounds dissolved in the water were removed to obtain a second material containing niobium titanium oxide. In S6-1, this second material was fired in an electric furnace in a nitrogen atmosphere at 650°C for 1 hour, yielding niobium titanium oxide powder with carbon attached to its surface.

[0063] Example 4 Niobium titanium oxide was recycled using the recycling method of the second embodiment shown in Figure 2 for negative electrodes produced during the battery manufacturing process. A slurry containing a first material was obtained in the same manner as in Example 1 up to step (S4). In S5-2, aluminum sulfate was added to the resulting slurry as an inorganic coating component to a concentration of 100 ppm by mass in water, and then polyoxyethylene alkyl ether, a nonionic coagulation polymer, was added as an organic coating component to a concentration of 5 ppm by mass in water. This coated the surface of the niobium titanium oxide in the mixed powder, and the niobium titanium oxide then coagulated and settled. The aluminum foil was removed by utilizing the difference in sedimentation velocity between the aluminum foil and the resulting material to obtain a second material containing niobium titanium oxide. In S6-2, the resulting second material was calcined in an electric furnace in a nitrogen atmosphere at 650°C for 1 hour to obtain a niobium titanium oxide powder with carbon attached to the surface. Furthermore, electron microscopy of the resulting oxide powder revealed that aluminum oxide particles were coated on the surface.

[0064] (Comparative Example 1) As a raw material, niobium titanium oxide powder was used before being formed into an electrode material.

[0065] (Creating electrodes) To 80% by mass of the niobium titanium oxide obtained in Examples 1 to 4, 10% by mass of acetylene black as a conductive agent and 10% by mass of CMC as a binder were added, and these were kneaded with an aqueous solvent to prepare a slurry. The slurry was applied to aluminum foil, dried, and pressed to prepare an electrode. A coin-shaped cell was produced using the obtained electrode, and the initial capacity of the niobium titanium oxide was confirmed. The results are shown in Table 1, and the capacity was equivalent to that of an electrode produced in the same manner using unused niobium titanium oxide in Comparative Example 1.

[0066] (Creating secondary batteries) This negative electrode was combined with a positive electrode containing nickel-cobalt-manganese oxide to prepare a laminate cell. This laminate cell was subjected to a cycle test at SOC 0-100% and 45°C. The capacity retention rate after 1000 cycles is shown in Table 1.

[0067] [Table 1]

[0068] The secondary batteries of Examples 1 to 4 were confirmed to have a capacity retention rate equal to or greater than that of the secondary battery produced using the unused niobium titanium oxide in Comparative Example 1. Furthermore, the amount of gas generated after 1000 cycles of the secondary battery produced using the niobium titanium oxide obtained in Example 4 was reduced by 20% compared to the secondary battery produced using the niobium titanium oxide obtained in Example 1. This demonstrates that the electrode active material obtained by the recycling method in which an inorganic coating component is further added can suppress gas generation.

[0069] As described above, the recycling method according to the embodiment made it possible to obtain a third material containing an oxide electrode active material from a battery or battery material containing the oxide electrode active material. Furthermore, the obtained third material could be reused as an electrode active material for a battery. Therefore, it is possible to provide a recycling method and electrode active material that can recycle a battery and / or battery material containing an oxide electrode active material.

[0070] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims.

[0071] The following describes the invention in terms of embodiments.

[0072] <1> A first step of obtaining a first material containing an oxide electrode active material from a battery or / and battery material containing the oxide electrode active material; a second step of dispersing the first material in a solvent to obtain a slurry; a third step of adding an organic substance to the slurry to obtain a second material containing the oxide electrode active material; a fourth step of obtaining a third material containing the oxide electrode active material from the second material by heat treatment; Including, How to recycle.

[0073] <2> The organic matter includes one or more of a surfactant, an oil, and a flocculating polymer; <1> The recycling method described in

[0074] <3> The first step includes a heat treatment at 300°C or higher and 450°C or lower. <1> or <2> The recycling method described in

[0075] <4> The third step is a flotation method. <1> from <3> The recycling method according to any one of the above.

[0076] <5> The third step is a coagulation and sedimentation method. <1> from <4> The recycling method according to any one of the above.

[0077] <6> the third material includes the oxide electrode active material having a carbon coating on at least a portion thereof; <1> from <5> The recycling method according to any one of the above.

[0078] <7> In the third step, aluminum sulfate or polyaluminum chloride is used in combination. <1> from <6> The recycling method according to any one of the above.

[0079] <8> the third material includes the oxide electrode active material having an aluminum compound coating on at least a portion thereof; <1> from <7> The recycling method according to any one of the above.

[0080] <9> The oxide electrode active material contains titanium or niobium. <1> from <8> The recycling method according to any one of the above.

[0081] <10> The oxide electrode active material is substantially free of lithium, <1> from <9> The recycling method according to any one of the above.

[0082] <11> <1> from <10> 10. An electrode active material produced by the recycling method according to claim 1.

Claims

1. a first step of obtaining a first material containing an oxide electrode active material from a battery or / and battery material containing the oxide electrode active material; a second step of dispersing the first material in a solvent to obtain a slurry; a third step of adding an organic substance to the slurry to obtain a second material containing the oxide electrode active material; a fourth step of obtaining a third material containing the oxide electrode active material from the second material by heat treatment; Including, How to recycle.

2. The organic matter includes one or more of a surfactant, an oil, and a flocculating polymer; The recycling method according to claim 1.

3. The first step includes a heat treatment at 300°C or higher and 450°C or lower. The recycling method according to claim 1.

4. The third step is a flotation process. The recycling method according to claim 3.

5. The third step is a coagulation and sedimentation method. The recycling method according to claim 1.

6. the third material includes the oxide electrode active material having a carbon coating on at least a portion thereof; The recycling method according to claim 1.

7. In the third step, aluminum sulfate and / or polyaluminum chloride is further added. The recycling method according to claim 1.

8. the third material includes the oxide electrode active material having an aluminum compound coating on at least a portion thereof; The recycling method according to claim 6.

9. The oxide electrode active material contains titanium or niobium. The recycling method according to claim 1.

10. The oxide electrode active material is substantially free of lithium, The recycling method according to claim 9.

11. An electrode active material produced by the recycling method according to claim 6 or 8.

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