Production method for recycled positive electrode active material

Abstract

This production method for a recycled positive electrode active material includes the following steps: (1) a step in which a positive electrode mixture containing a positive electrode active material and a carbon-containing material and an activation treatment agent containing one or more alkali metal compounds are mixed to obtain a mixture; (2) a step in which the mixture is heated at a temperature lower than the melting onset temperature of the activation treatment agent and a heated mixture is obtained; and (3) a step in which the heated positive electrode active material is recovered from the heated mixture.

Description

Method for manufacturing recycled positive electrode active material

[0001] The present disclosure relates to a method for producing recycled positive electrode active materials.

[0002] The positive electrode active material of a battery contains rare metal components such as cobalt, nickel, manganese, and lithium, and in particular, compounds containing the above rare metal components as main components are used as the positive electrode active material of non-aqueous electrolyte secondary batteries. In order to conserve the resources of rare metal components, a method for reproducing rare metal components from waste battery materials of secondary batteries is desired.

[0003] For example, Patent Document 1 discloses a method for recovering a positive electrode active material by mixing a positive electrode mixture with an activation treatment agent containing an alkali metal compound, heating the mixture to a temperature equal to or higher than the melting point of the activation treatment agent, and removing decomposition products and the activation treatment agent with water or the like. This method is cost-effective in that it recovers a positive electrode active material directly from battery waste without using an organic solvent.

[0004] JP 2012-186150 A

[0005] The positive electrode mixture includes the positive electrode mixture in the positive electrode recovered from discarded batteries and the positive electrode mixture in the positive electrode waste generated in the process of manufacturing the positive electrode or the battery. In recent years, not only has recycling of the positive electrode active material from the positive electrode mixture in the positive electrode recovered from discarded batteries been studied, but also recycling of the positive electrode active material from the positive electrode mixture in the positive electrode waste generated in the process of manufacturing the positive electrode or the battery has been studied.

[0006] Therefore, an object of the present disclosure is to provide a method for producing a recycled positive electrode active material that can make the charge / discharge characteristics of a battery produced using a recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery produced using an unused positive electrode active material.

[0007] The present disclosure includes, for example, the following [1] to [5]. [1] A method for producing a recycled cathode active material, comprising the following steps: (1) mixing a cathode composite containing a cathode active material with an activation treatment agent containing one or more alkali metal compounds to obtain a mixture; (2) heating the mixture to a temperature below the melting start temperature of the activation treatment agent to obtain a heated mixture; and (3) recovering a heated cathode active material from the heated mixture. [2] The production method according to [1], wherein in step (3), the heated mixture is heated at a temperature higher than that in step (2), and the heated cathode active material is recovered. [3] The production method according to [1] or [2], wherein the cathode active material contains a lithium compound. [4] The production method according to any one of [1] to [3], wherein the cathode active material contains a composite oxide containing at least one element selected from element group 1 below and at least one element selected from element group 2 below. Element group 1: Ni, Co, Mn, Fe, Al, and P Element group 2: Li, Na, K, Ca, Sr, Ba, and Mg [5] The manufacturing method according to any one of [1] to [4], wherein the activation treatment agent contains at least one compound selected from the group consisting of potassium compounds and sodium compounds.

[0008] According to the present disclosure, it is possible to provide a method for producing a recycled positive electrode active material that can make the charge / discharge characteristics of a battery produced using a recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery produced using an unused positive electrode active material.

[0009] (Method for Producing Recycled Positive Electrode Active Material) Hereinafter, a method for producing a recycled positive electrode active material will be described.

[0010] A method for producing a recycled cathode active material according to an embodiment of the present disclosure includes the following steps: Step (1): A step of mixing a cathode composite containing a cathode active material with an activation treatment agent containing one or more alkali metal compounds to obtain a mixture; Step (2): A step of heating the mixture to a temperature below the melting start temperature of the activation treatment agent to obtain a heated mixture; and Step (3): A step of recovering a heated cathode active material from the heated mixture.

[0011] In one embodiment, a method for producing a recycled cathode active material involves heating a mixture of a cathode composite and an activation agent to a temperature below the melting point of the activation agent, and then recovering the heated cathode active material from the mixture. The inventors have found that it is possible to produce a recycled cathode active material without heating the mixture above the melting point of the activation agent, as in the conventional method. They have also found that the charge-discharge characteristics of a battery produced using the recycled cathode active material can be made more comparable to those of a battery produced using virgin cathode active material. The inventors speculate that the reasons for this are as follows.

[0012] That is, the cathode composite in the cathode waste generated during the manufacturing process of a cathode or battery (e.g., the end of a cathode, a non-standard cathode) is hardly degraded. Furthermore, even in the cathode composite in the cathode recovered from a discarded battery, there is a relatively small degree of degradation. Therefore, when these relatively degraded cathode composites are mixed with an activation treatment agent and the resulting mixture is heated, it is possible to sufficiently activate the cathode active material even at a low heating temperature. In addition, the low heating temperature suppresses the elution of metals in the cathode active material into the molten salt reaction field of the activation treatment agent, thereby achieving charge / discharge characteristics comparable to those of a battery manufactured using unused cathode active material. Furthermore, after heating the mixture of the cathode composite and the activation treatment agent, the mixture is heated at a temperature higher than that in the step of heating the mixture of the cathode composite and the activation treatment agent, thereby sufficiently increasing the crystallite size of the cathode active material, thereby improving the charge / discharge characteristics. For these reasons, according to the present disclosure, the charge-discharge characteristics of a battery manufactured using a recycled cathode active material can be made more comparable to those of a battery manufactured using a virgin cathode active material. However, the mechanism of the present disclosure is not limited to the above.

[0013] Each step will be described in detail below.

[0014] Pre-process (A): Positive Electrode Composite Preparation Process First, a positive electrode composite containing a positive electrode active material is prepared.

[0015] [Positive Electrode Active Material] Examples of the positive electrode active material include composite compounds containing one or more of the following elements as constituent elements: lithium, oxygen, fluorine, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, potassium, calcium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, yttrium, niobium, molybdenum, silver, indium, tungsten, etc. The positive electrode active material may contain a lithium compound.

[0016] The positive electrode active material may be composed of only a single compound, or may be composed of multiple compounds.

[0017] The positive electrode active material preferably contains a composite oxide containing at least one element selected from the following element group 1 and at least one element selected from the following element group 2: Element group 1: Ni, Co, Mn, Fe, Al, and P Element group 2: Li, Na, K, Ca, Sr, Ba, and Mg

[0018] The positive electrode active material preferably contains a compound represented by the following formula (A).

[0019] Li １＋ａ M ２ ｂ M １ M Ｔ ｃ O ２＋ｄ X ｅ (A) However, M ２ represents at least one element selected from the group consisting of Na, K, Ca, Sr, Ba, and Mg; M １ represents at least one element selected from the group consisting of Ni, Co, Mn, Fe, Al, and P; M Ｔ represents at least one element selected from the group consisting of transition metal elements excluding Ni, Co, Mn, and Fe, X represents at least one element selected from the group consisting of non-metal elements excluding O and P, and the following conditions are satisfied: -0.4<a<1.5, 0≦b<0.5, 0≦c<0.5, -0.5<d<1.5, and 0≦e<0.5.

[0020] M Ｔis preferably at least one element selected from the group consisting of Cu, Ti, Mg, Al, W, Mo, Nb, Zn, Sn, Zr, Ga, V, B, Si, Ca, Sr, Ba, Ge, Cr, Sc, Y, La, Ta, Tc, Ru, Rh, Pd, Ag, Cd, and In. Examples of X include F, S, Cl, Br, I, Se, Te, and N.

[0021] The positive electrode active material preferably contains a composite oxide containing at least Li and Ni.

[0022] In the positive electrode active material, M １ The mole fraction of Ni in the alloy is preferably 0.3 to 0.95.

[0023] The crystal structure of the positive electrode active material (for example, composite oxide) is not particularly limited, but a layered structure is preferred, and a hexagonal or monoclinic crystal structure is more preferred.

[0024] The hexagonal crystal structure is P3, P3 １ , P3 ２ , R3, P-3, R-3, P312, P321, P3 １ 12. P3 １ 21, P3 ２ 12. P3 ２ 21, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P6 １ , P6 ５ , P6 ２ , P6 ４ , P6 ３ , P-6, P6 / m, P6 ３ / m, P622, P6 １ 22, P6 ５ 22, P6 ２ 22, P6 ４ 22, P6 ３ 22, P6mm, P6cc, P6 ３ cm, P6 ３ mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P6 ３ / mcm, and P6 ３ / mmc.

[0025] The monoclinic crystal structure is P2, P2 １ , C2, Pm, Pc, Cm, Cc, P2 / m, P2 １ / m, C2 / m, P2 / c, P2 １ It belongs to any one space group selected from the group consisting of C1 / c, C2 / c, and C3 / c.

[0026] The crystal structure of the positive electrode active material preferably belongs to the space group R-3m included in the hexagonal crystal structure or the space group C2 / m included in the monoclinic crystal structure.

[0027] The crystal structure of the positive electrode active material can be identified from a powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement using CuKα radiation as a radiation source.

[0028] The particle size of the positive electrode active material in the positive electrode mixture is not particularly limited, but may be 0.001 to 100 μm. The particle size distribution of the positive electrode active material can be measured using a laser diffraction / scattering particle size distribution analyzer (e.g., Mastersizer 2000, manufactured by Malvern Instruments). A volume-based cumulative particle size distribution curve is created from the particle size distribution, and the particle size (D50) value at 50% accumulation from the fine particle side can be used as the average particle size of the positive electrode active material.

[0029] There is no particular limitation on the content of the positive electrode active material in the positive electrode mixture.

[0030] [Binder] The positive electrode mixture may contain a binder. When the positive electrode mixture contains a binder, particles of the positive electrode active material may be bound to one another by the binder.

[0031] Examples of the binder (pre-activation binder) contained in the positive electrode mixture include thermoplastic resins, and specific examples include fluororesins such as polyvinylidene fluoride (hereinafter sometimes referred to as "PVdF"), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers, hexafluoropropylene-vinylidene fluoride copolymers, and tetrafluoroethylene-perfluorovinyl ether copolymers; polyolefin resins such as polyethylene and polypropylene; and styrene-butadiene copolymers (SBR). One type of binder may be used alone, or two or more types may be used in combination.

[0032] The content of the binder in the positive electrode mixture is not particularly limited, but may be within the following ranges relative to 100 parts by mass of the positive electrode active material. The content of the binder may be 0.5 parts by mass or more, 1 part by mass or more, or 2 parts by mass or more. The content of the binder may be 30 parts by mass or less, 10 parts by mass or less, or 5 parts by mass or less. From these perspectives, the content of the binder may be 0.5 to 30 parts by mass, 1 to 10 parts by mass, 1 to 5 parts by mass, or 2 to 5 parts by mass.

[0033] [Conductive Material] The positive electrode mixture may contain a conductive material and / or an electrolyte. When the positive electrode mixture contains a binder and a conductive material, the particles of the positive electrode active material and the conductive material may be bound to each other by the binder. The positive electrode mixture may contain a fluorine compound derived from the binder and / or the electrolytic solution (e.g., the electrolyte in the electrolytic solution).

[0034] Examples of the conductive material include metal-based conductive materials such as metal particles; and carbon-based conductive materials made of carbon materials.

[0035] Specific examples of carbon-based conductive materials include graphite powder, carbon black (for example, acetylene black), and fibrous carbon materials (for example, graphitized carbon fibers and carbon nanotubes).

[0036] The carbonaceous conductive material may be a single carbon material or may be made up of multiple carbon materials.

[0037] The specific surface area of ​​the carbon material used as the carbon-based conductive material is 0.1 to 500 m ２ In this case, the conductive material may have a specific surface area of ​​30 m ２ / g or more, and ２ / g or more, and may be carbon black having a specific surface area of ​​30 m ２ When an activation treatment agent containing an alkali metal compound having oxidizing power, which will be described later, is used, the rate of oxidation treatment of the carbon-based conductive material can be increased, and even a carbon material having a small specific surface area can be oxidized in some cases.

[0038] The content of the conductive material in the positive electrode mixture is not particularly limited, but may be within the following ranges relative to 100 parts by mass of the positive electrode active material. The content of the conductive material may be 0 parts by mass or more, more than 0 parts by mass, 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more. The content of the conductive material may be 50 parts by mass or less, 40 parts by mass or less, 30 parts by mass or less, 20 parts by mass or less, or 10 parts by mass or less. From these perspectives, the content of the conductive material may be 0 to 50 parts by mass, more than 0 parts by mass and 40 parts by mass or less, 1 to 30 parts by mass, 1 to 10 parts by mass, 3 to 20 parts by mass, or 5 to 10 parts by mass.

[0039] [Electrolyte and Solvent] The electrolyte is a component derived from the electrolyte solution of the battery and impregnated into the positive electrode mixture. Examples of the electrolyte include LiPF ６ , LiBF ４ , LiClO ４ , LiN(SO ２ CF ３ ) ２ , LiN(SO ２ F) ２ , LiCF ３ SO ３ The content of the electrolyte contained in the positive electrode mixture is not particularly limited, but may be 0.0005 to 7 mass %.

[0040] The positive electrode mixture may contain a solvent derived from the electrolyte solution, such as dimethyl carbonate, diethyl carbonate, or ethyl methyl carbonate.

[0041] [Recovery of Positive Electrode Mixture] The positive electrode mix can be obtained by separating and recovering the positive electrode mix layer from a waste positive electrode having a current collector and a positive electrode mix layer.

[0042] "Waste positive electrodes" may refer to positive electrodes recovered from discarded batteries and waste positive electrodes generated during the manufacturing process of positive electrodes or batteries. Discarded batteries may be used batteries or unused, non-standard batteries. Waste positive electrodes may be the ends of positive electrodes generated during the battery manufacturing process or non-standard positive electrodes. As the positive electrode composite, waste positive electrode composite not attached to a current collector (waste generated during the positive electrode composite manufacturing process) may also be used.

[0043] The waste positive electrode has a current collector made of a metal foil such as aluminum foil or copper foil, and a positive electrode composite layer provided on the current collector. The positive electrode composite layer may be provided on one side or both sides of the current collector.

[0044] Examples of methods for separating a positive electrode composite layer from a waste positive electrode having a current collector and a positive electrode composite layer include a method of mechanically peeling the positive electrode composite layer from the current collector (e.g., a method of scraping the positive electrode composite layer from the current collector), a method of penetrating a solvent into the interface between the current collector and the positive electrode composite layer to peel the positive electrode composite layer from the current collector, a method of dissolving the current collector using an alkaline or acidic aqueous solution to separate the positive electrode composite layer, etc. The method for separating a positive electrode composite layer from a waste positive electrode having a current collector and a positive electrode composite layer is preferably a method of mechanically peeling the positive electrode composite layer from the current collector.

[0045] Pre-process (B): Positive Electrode Composite Washing Process Next, when the positive electrode composite contains an electrolyte, it is preferable to bring the prepared positive electrode composite into contact with an electrolyte washing solvent to remove at least a portion of the electrolyte from the positive electrode composite. Specifically, the positive electrode composite containing the positive electrode active material and the electrolyte is brought into contact with the electrolyte washing solvent to obtain a slurry containing a solid component and a liquid component, and then the slurry is subjected to solid-liquid separation into the solid component and the liquid component.

[0046] Solid-liquid separation is an operation for separating a slurry into a solid component and a liquid component. Examples of the solid-liquid separation method may be conventionally known methods, such as filtration and centrifugation.

[0047] The electrolyte cleaning solvent is not particularly limited, and examples of the electrolyte cleaning solvent include carbonates such as ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, and propylene carbonate; water; ketones such as acetone, methyl ethyl ketone, diethyl ketone, and methyl isobutyl ketone; and alcohols such as ethanol, methanol, propanol, and isopropyl alcohol.

[0048] The cathode mixture can be brought into contact with the electrolyte cleaning solvent in a known powder-liquid contact device (for example, a stirring tank).

[0049] In the step of contacting the positive electrode mixture with the electrolyte washing solvent, the positive electrode mixture and the electrolyte washing solvent are preferably stirred to obtain a slurry. The peripheral speed of the tip of the stirring blade may be 0.1 to 1.0 m / s.

[0050] In the washing step of the positive electrode composite, after solid-liquid separation, the solid component may be rinsed. Rinsing is an operation in which the solid component is again brought into contact with the electrolyte washing solvent to obtain a slurry, and the slurry is then separated again into a solid component and a liquid component. In the washing step of the positive electrode composite, rinsing may be performed multiple times. The slurry concentration in rinsing can be adjusted as desired. During rinsing, the slurry can also be stirred as described above.

[0051] The above-described washing process can sufficiently remove the electrolyte from the positive electrode mixture. For example, if the electrolyte remains, the following reaction occurs, which may cause the structure of the positive electrode active material to change from a layered rock salt structure to a spinel structure. However, by removing the electrolyte from the positive electrode mixture, the following reaction can be suppressed: LiPF ６ +16LiMO ２ +20 ２ → 6 LiF + Li ３ P.O. ４ +8LiM ２ O ４

[0052] Furthermore, when the activation treatment agent contains lithium carbonate, lithium may be consumed by the following reaction, but the following reaction can be suppressed by removing the electrolyte from the positive electrode mixture: LiPF ６ +4Li ２ CO ３ → 6 LiF + Li ３ P.O. ４ +4CO ２

[0053] The separated solid component may be dried to remove the electrolyte washing solvent by reducing pressure and / or heating, if necessary. The heating temperature may be 50 to 200°C.

[0054] Step (1): Activation Treatment Agent Mixing Step Next, the prepared positive electrode mixture and an activation treatment agent containing one or more alkaline compounds are mixed to obtain a mixture.

[0055] The positive electrode mixture and the activation treatment agent may be mixed by either dry mixing or wet mixing, or by a combination of these methods. The order in which the positive electrode mixture and the activation treatment agent are mixed is not particularly limited.

[0056] During mixing, it is preferable to use a mixer equipped with mixing media such as balls and go through a pulverizing and mixing step, which can improve mixing efficiency.

[0057] Dry mixing is preferred as a mixing method because it allows for simpler mixing. For dry mixing, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, a powder mixer equipped with internal stirring blades, a ball mill, a vibration mill, or a combination of these devices can be used.

[0058] The mixing device used for dry mixing is preferably a powder mixer equipped with an internal stirring blade, and specifically, a Lödige mixer (manufactured by Matsubo Co., Ltd.) can be mentioned.

[0059] The activation treatment agent used in this step will be described in detail below.

[0060] <Activation Treatment Agent> The activation treatment agent contains one or more alkali metal compounds. The activation treatment agent preferably contains at least one compound selected from the group consisting of potassium compounds and sodium compounds. Here, potassium and / or sodium may be referred to as alkali metal element X. In addition to the potassium compound and / or sodium compound, the activation treatment agent may also contain an alkali metal compound containing another alkali metal such as Li.

[0061] When the activation treatment agent comes into contact with the positive electrode active material, the positive electrode active material can be activated. When the alkali metal compound in the activation treatment agent contains a molten portion, the contact between the molten portion and the positive electrode active material is improved, thereby further accelerating the activation of the positive electrode active material.

[0062] Furthermore, the positive electrode mixture may contain a fluorine-containing compound derived from the binder and / or the electrolyte, but by contacting the fluorine-containing compound with the activation treatment agent, the fluorine component is stabilized as an alkali metal fluoride, thereby suppressing the generation of corrosive gases such as hydrogen fluoride. Note that it is desirable to prevent the generation of hydrogen fluoride, as it reduces the activity of the positive electrode active material.

[0063] The proportion of all alkali metal compounds in the activation treatment agent is appropriately set in consideration of the type of alkali metal compound, the type of target positive electrode active material, etc., and is usually 50 mass % or more, preferably 70 mass % or more, relative to the total mass of the activation treatment agent, and may be 100 mass % (an embodiment in which the activation treatment agent is essentially composed of alkali metal compounds).

[0064] The concentration of at least one alkali metal selected from the group consisting of potassium and sodium in the alkali metals contained in the alkali metal compound can be adjusted arbitrarily within the range of 0 to 100 mol %, but is preferably 10 mol % or more, more preferably 20 mol % or more, and is preferably 90 mol % or less, more preferably 80 mol % or less.

[0065] Examples of alkali metal compounds that can be used as components of the activation treatment agent include alkali metal hydroxides, borates, carbonates, oxides, peroxides, superoxides, nitrates, phosphates, sulfates, chlorides, vanadates, bromates, molybdates, and tungstates. These can be used as components of the activation treatment agent either alone or in combination.

[0066] Specific examples of suitable alkali metal compounds include hydroxides such as LiOH, NaOH, KOH, RbOH, and CsOH; LiBO ２ , NaBO ２ , KBO ２ , RbBO ２ , CsBO ２ Boric acid compounds such as Li ２ CO ３ , Na ２ CO ３ , K. ２ CO ３ , RbCO ３, CsCO ３ Carbonates such as Li ２ O, Na ２ O.K. ２ O, Rb ２ O, Cs ２ Oxides such as Li ２ O ２ , Na ２ O ２ , K. ２ O ２ , Rb ２ O ２ , Cs ２ O ２ peroxides such as LiO ２ , NaO ２ , K.O. ２ , RbO ２ , CsO ２ superoxides such as LiNO ３ , NaNO ３ , KNO ３ , RbNO ３ , CsNO ３ Nitrates such as Li ３ P.O. ４ , Na ３ P.O. ４ , K. ３ P.O. ４ , Rb ３ P.O. ４ , Cs ３ P.O. ４ phosphates such as Li ２ SO ４ , Na ２ SO ４ , K. ２ SO ４ , Rb ２ SO ４ , Cs ２ SO ４ chlorides such as LiCl, NaCl, KCl, RbCl, and CsCl; bromides such as LiBr, NaBr, KBr, RbBr, and CsBr; LiVO ３ , NaVO ３ , K.V.O. ３ , RbVO ３ , CsVO ３ vanadates such as Li ２ MoO ４ , Na ２ MoO ４, K. ２ MoO ４ , Rb ２ MoO ４ , CsMoO ４ Molybdates such as; and Li ２ WO ４ , Na ２ WO ４ , K. ２ WO ４ , Rb ２ WO ４ , CsWO ４ tungstates such as:

[0067] Here, in order to further enhance the activation effect of the positive electrode active material, the activation treatment agent may contain, in addition to at least one compound selected from the group consisting of potassium compounds and sodium compounds, the same alkali metal element as the alkali metal element contained in the positive electrode active material in the positive electrode mixture.

[0068] That is, when the positive electrode active material in the positive electrode mixture is a lithium composite oxide, the activation treatment agent preferably contains a lithium compound in addition to at least one compound selected from the group consisting of potassium compounds and sodium compounds. Suitable lithium compounds include LiOH, LiBO, ２ , Li ２ CO ３ , Li ２ O, Li ２ O ２ , LiO ２ , LiNO ３ , Li ３ P.O. ４ , Li ２ SO ４ , LiCl, LiVO ３ , LiBr, Li ２ MoO ４ , and Li ２ WO ４ Examples include:

[0069] The activation treatment agent may contain a compound other than an alkali metal compound as needed. Examples of compounds other than alkali metal compounds include alkaline earth metal compounds containing alkaline earth metal elements such as magnesium, calcium, and barium. The alkaline earth metal compound is contained in the activation treatment agent together with the alkali metal compound for the purpose of controlling the melting initiation temperature of the activation treatment agent.

[0070] Furthermore, the content of compounds other than the alkali metal compound in the activation treatment agent is selected within a range that does not significantly suppress the effects derived from the above-mentioned molten alkali metal compound, and can be less than 50 mass% relative to the total mass of the activation treatment agent.

[0071] The amount of activation treatment agent added in the mixture of the positive electrode mixture and the activation treatment agent is preferably 0.001 to 100 times, and more preferably 0.05 to 1 time, the mass of the positive electrode active material contained in the positive electrode mixture.

[0072] When the activation treatment agent contains a potassium compound and a lithium compound, the ratio of the lithium content (molar basis) to the potassium content (molar basis) (lithium content / potassium content) may be 0.01 to 100, 0.1 to 10, or 0.2 to 4, from the viewpoint of making it easier to make the charge / discharge characteristics of a battery produced using a recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery produced using an unused positive electrode active material.

[0073] When the activation treatment agent contains a sodium compound and a lithium compound, the ratio of the lithium content (molar basis) to the sodium content (molar basis) (lithium content / sodium content) may be 0.01 to 100, 0.1 to 10, or 0.2 to 4, from the viewpoint of making it easier to make the charge / discharge characteristics of a battery produced using a recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery produced using an unused positive electrode active material.

[0074] When the activation treatment agent contains a potassium compound, the potassium content (by mol) contained in the activation treatment agent may be 1% or more and less than 500%, 10% or more and less than 400%, 50% or more and less than 300%, 100% or more and less than 250%, or 150% or more and less than 250% of the fluorine content (by mol) contained in the positive electrode composite, from the viewpoint of making it easier to make the charge / discharge characteristics of a battery produced using the recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery produced using an unused positive electrode active material.

[0075] When the activation treatment agent contains a sodium compound, the content (molar basis) of sodium contained in the activation treatment agent relative to the content (molar basis) of fluorine contained in the positive electrode composite may be 1 to 200%, 10 to 200%, 50 to 200%, or 100 to 200%, 1% or more but less than 150%, 10% or more but less than 150%, 50% or more but less than 150%, or 100% or more but less than 150%, from the viewpoint of making it easier to make the charge / discharge characteristics of a battery produced using a recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery produced using an unused positive electrode active material.

[0076] The number of moles of the alkali metal compound in the activation treatment agent in the mixture of the positive electrode composite and the activation treatment agent can be added so that the number of moles of the alkali metal element is 0.001 to 200 times the number of moles of the positive electrode active material (e.g., Formula A) contained in the positive electrode composite, which is taken as 1.

[0077] By appropriately controlling the ratio of the activation treatment agent in the mixture, it is possible to reduce the cost of recovering the positive electrode active material from the positive electrode mixture, increase the oxidative decomposition rate of the carbon-based conductive material and binder, improve the effect of preventing the generation of corrosive gases during the heating process, and further increase the discharge capacity of a battery manufactured using the resulting positive electrode active material.

[0078] Preferably, at least one of the alkali metal compounds contained in the activation treatment agent is an alkali metal compound that exhibits alkalinity when dissolved in water. When an activation treatment agent containing such an alkali metal compound is dissolved in pure water, the resulting solution has a pH greater than 7. Hereinafter, such an activation treatment agent may be referred to as an "alkaline activation treatment agent."

[0079] The use of an alkaline activation treatment agent can further suppress the generation of corrosive gases during the heating process, thereby increasing the discharge capacity of a battery manufactured using the recovered positive electrode active material. In addition, the use of an alkaline activation treatment agent can also increase the treatment speed of the carbon-based conductive material and binder.

[0080] Examples of alkali metal compounds that exhibit alkalinity when dissolved in water and contained in the alkaline activation treatment agent include hydroxides, carbonates, hydrogencarbonates, oxides, peroxides, and superoxides of alkali metals. Specific examples of alkali metal compounds that exhibit alkalinity include hydroxides such as LiOH, NaOH, KOH, RbOH, and CsOH; ２ CO ３ , Na ２ CO ３ , K. ２ CO ３ , RbCO ３ , CsCO ３ Carbonates such as LiHCO ３ , NaHCO ３ , KHCO ３ , RbHCO ３ , CsHCO ３ hydrogen carbonates such as Li ２ O, Na ２ O.K. ２ O, Rb ２ O, Cs ２ Oxides such as Li ２ O ２ , Na ２ O ２ , K. ２ O ２ , Rb ２ O ２ , Cs ２ O ２ peroxides such as LiO２ , NaO ２ , K.O. ２ , RbO ２ , CsO ２ One or more of these may be contained in the activation treatment agent.

[0081] Furthermore, when the conductive material contained in the positive electrode composite is a carbon-based conductive material, at least one of the alkali metal compounds contained in the activation treatment agent may be an alkali metal compound having an oxidizing power that oxidizes and decomposes the carbon-based conductive material at the temperature of the heating step. Hereinafter, an activation treatment agent containing such an alkali metal compound may be referred to as an "activation treatment agent having an oxidizing power."

[0082] Use of an activation treatment agent having such oxidizing power is particularly effective in promoting the oxidation of the conductive material, which is a carbon material, to carbon dioxide, and promoting the oxidation of the binder, which is a hydrocarbon material, to carbon dioxide and water vapor, thereby making it possible to further increase the discharge capacity of a battery manufactured using the obtained positive electrode active material, and furthermore, in some cases to improve the effect of preventing the generation of corrosive gases during the heating process.

[0083] Examples of alkali metal compounds having the oxidizing power required to oxidize carbonaceous conductive materials and hydrocarbons into carbon dioxide and water vapor include alkali metal peroxides, superoxides, nitrates, sulfates, vanadates, and molybdates, which may be used alone or in combination of two or more.

[0084] Specific examples of alkali metal compounds having oxidizing power include Li ２ O ２ , Na ２ O ２ , K. ２ O ２ , Rb ２ O ２ , Cs ２ O ２ superoxides such as LiO ２ , NaO ２ , K.O. ２ , RbO ２ , CsO ２ ; LiNO ３ , NaNO ３ , KNO３ , RbNO ３ , CsNO ３ Nitrates such as Li ２ SO ４ , Na ２ SO ４ , K. ２ SO ４ , Rb ２ SO ４ , Cs ２ SO ４ Sulfates such as LiVO ３ , NaVO ３ , K.V.O. ３ , RbVO ３ , CsVO ３ vanadates such as Li ２ MoO ４ , Na ２ MoO ４ , K. ２ MoO ４ , Rb ２ MoO ４ , CsMoO ４ and molybdates such as:

[0085] Details of the oxidizing power of these alkali metal compounds are described in JP 2012-186150 A.

[0086] The alkali metal compound may be a carbonate or a sulfate from the viewpoint of making it easier to make the charge / discharge characteristics of a battery manufactured using a recycled positive electrode active material more comparable to the charge / discharge characteristics of a battery manufactured using a virgin positive electrode active material, and Li ２ CO ３ , Na ２ SO ４ , Na ２ CO ３ , and K ２ CO ３ It may be at least one selected from the group consisting of:

[0087] Step (2): Heating Step The heating step is a step in which the mixture obtained in step (1) (hereinafter sometimes referred to as the "mixture before heating") is heated to a temperature below the melting initiation temperature of the activation treatment agent. The mixture obtained in this heating step is sometimes referred to as the "mixture after heating." In this specification, "heating to a temperature below the melting initiation temperature of the activation treatment agent" means heating while maintaining a temperature below the melting initiation temperature of the activation treatment agent (heating at a temperature maintained below the melting initiation temperature of the activation treatment agent). Furthermore, "heating to a temperature below the melting initiation temperature of the activation treatment agent" means not heating at a temperature equal to or higher than the melting initiation temperature of the activation treatment agent.

[0088] The "melting initiation temperature (Tmp) of the activation treatment agent" means the lowest temperature at which a part of the activation treatment agent exhibits a liquid phase.

[0089] The melting initiation temperature (Tmp) of the activation treatment agent is a value determined by differential thermal analysis (DTA). That is, 5 mg of the mixture before heating is subjected to differential thermal analysis (DTA, measurement conditions: temperature rise rate: 10°C / min), and the temperature at which the DTA signal shows an endothermic peak is defined as the melting initiation temperature (Tmp).

[0090] The temperature to which the mixture before heating is heated may be 700°C or lower, 650°C or lower, 600°C or lower, or 550°C or lower, from the viewpoint of suppressing deterioration of the crystal structure of the positive electrode active material due to contact of hydrogen fluoride, carbon dioxide, and water, which are produced by decomposition of the binder, conductive material, and the like contained in the positive electrode mixture, with the positive electrode active material, and making it easier to achieve charge / discharge characteristics comparable to those of a battery produced using unused positive electrode active material.

[0091] The temperature to which the mixture before heating is heated may be 150°C or higher, 200°C or higher, 250°C or higher, 300°C or higher, 350°C or higher, 400°C or higher, or 450°C or higher, from the viewpoint of promoting decomposition of the binder, conductive material, etc., and making it easier to achieve charge / discharge characteristics comparable to those of a battery produced using an unused positive electrode active material.

[0092] The melting initiation temperature (Tmp) of the activation treatment agent is preferably 900° C. or lower, more preferably 800° C. or lower, even more preferably 700° C. or lower, and particularly preferably 600° C. or lower. There is no lower limit to the melting initiation temperature (Tmp) of the activation treatment agent, but it may be, for example, 150° C. or higher, 250° C. or higher, 350° C. or higher, 450° C. or higher, or 500° C. or higher.

[0093] The melting point of the activation treatment agent refers to the lowest temperature at which a part of the activation treatment agent becomes liquid when heated alone. By mixing the positive electrode composite and the activation treatment agent, the melting initiation temperature (Tmp) of the activation treatment agent becomes lower than the melting point of the activation treatment agent.

[0094] The melting point of the activation treatment agent is a value determined by differential thermal analysis (DTA). Specifically, 5 mg of the activation treatment agent is subjected to differential thermal analysis (DTA, measurement conditions: temperature rise rate: 10°C / min), and the melting point of the activation treatment agent is determined as the temperature at which the DTA signal shows an endothermic peak.

[0095] The atmosphere for heating is not particularly limited, and may be an oxygen-containing gas such as air, nitrogen, argon, or carbon dioxide, or may be a mixture of these gases. The pressure of the atmosphere is not particularly limited, and may be atmospheric pressure, a reduced pressure atmosphere, or a pressurized atmosphere.

[0096] In step (2), the mixture before heating is heated to a temperature below the melting initiation temperature (Tmp) of the activation treatment agent as described above, whereby the following effects occur.

[0097] By heating the mixture before heating to a temperature below the melting start temperature (Tmp) of the activation treatment agent, hydrogen fluoride and carbon dioxide produced by decomposition of the binder, conductive material, etc. contained in the positive electrode mixture are rapidly generated, and this prevents deterioration of the crystalline structure of the positive electrode active material due to contact of these with the positive electrode active material, making it easier to achieve charge / discharge characteristics comparable to those of a battery manufactured using unused positive electrode active material. In addition, heating the mixture before heating together with the activation treatment agent can also provide a crystalline structure repair effect.

[0098] The contact of the heated activation treatment agent with the carbon-based conductive material and binder increases the rate of oxidative decomposition of the conductive material and binder. Furthermore, the contact of the heated activation treatment agent with the fluorine compounds derived from the binder, electrolyte, etc. stabilizes the fluorine components as alkali metal fluorides, preventing the generation of hydrogen fluoride, a corrosive gas, and further suppressing deterioration of the crystalline structure of the positive electrode active material.

[0099] Furthermore, when the activation treatment agent contains the same alkali metal as the alkali metal contained in the positive electrode active material, it is possible to supply the alkali metal that is insufficient for the positive electrode active material.

[0100] The temperature of the heating step and the holding time at that temperature can be appropriately adjusted depending on the types and combinations of the positive electrode active material, binder, conductive material, and alkali metal compound and other compounds contained in the activation treatment agent that constitute the positive electrode mixture. Typically, the temperature is in the range of 100 to 1000°C, and the holding time is about 10 minutes to 24 hours.

[0101] The temperature of the heating step is preferably lower than the melting point of the alkali metal compound contained in the activation treatment agent. Note that the melting point of the alkali metal compound may be lower than the melting point of each compound alone when multiple types of compounds are mixed. When the activation treatment agent contains two or more types of alkali metal compounds, the eutectic point is taken as the melting point of the alkali metal compound.

[0102] After the heating step, the mixture can be cooled to any temperature (for example, room temperature (20° C.)) as needed. In this way, a heated mixture containing a heated positive electrode active material is obtained.

[0103] Step (3): Positive Electrode Active Material Recovery Step The positive electrode active material recovery step is a step of recovering the heated positive electrode active material from the heated mixture (or the solid component obtained in step (3a), the solid component obtained in step (3b), or the solid component obtained in step (3c)) after the heating step of step (2).

[0104] The heated mixture contains not only the heated positive electrode active material, but also components derived from the activation treatment agent (such as alkali metal compounds), undecomposed conductive material and binder, and other undecomposed materials of the positive electrode mixture. Furthermore, if the positive electrode mixture contains an electrolyte solution containing a fluorine component, the mixture may also contain a fluorine component derived from the electrolyte. In step (3), it is preferable to remove components derived from the activation treatment agent (such as alkali metal compounds), unreacted activation treatment agent, undecomposed conductive material and binder, and other undecomposed materials of the positive electrode mixture, from the viewpoint of more easily achieving rate characteristics comparable to those of a battery manufactured using unused positive electrode active material by increasing the purity of the positive electrode active material.

[0105] Examples of methods for separating and recovering the heated positive electrode active material from the heated mixture include a solid-liquid separation method in which a solvent such as water is added to the mixture to form a slurry, followed by solid-liquid separation, and a vaporization separation method in which the mixture is heated to vaporize and separate components other than the heated positive electrode active material. The solid-liquid separation method will be described below.

[0106] Step (3a): Solid-Liquid Separation Step Step (3a) is a step of bringing the heated mixture into contact with a liquid containing water to obtain a slurry containing a solid component (the heated mixture or a solid component containing the heated positive electrode active material) and a liquid component, and then separating the slurry into the solid component and the liquid component.

[0107] The mixture after heating contains not only the heated positive electrode active material, but also components derived from the activation treatment agent (such as alkali metal compounds), and undecomposed materials of the positive electrode mixture, such as undecomposed conductive material and binder, etc. Furthermore, if the positive electrode mixture contains an electrolyte solution containing a fluorine component, the mixture may also contain a fluorine component derived from the electrolyte.

[0108] In order to separate and recover the heated positive electrode active material from the heated mixture, a liquid containing water is added to the mixture to form a slurry, which is then subjected to solid-liquid separation to separate the solid component and the liquid component.

[0109] The liquid used in the slurrying step (a step of contacting the heated mixture with a liquid containing water to obtain a slurry containing a solid component and a liquid component) is not particularly limited as long as it contains water. The amount of water in the liquid may be 50% by mass or more. In order to increase the solubility of water-soluble components or to increase the processing speed, components other than water may be added to the liquid to adjust the pH.

[0110] Suitable examples of the water-containing liquid include pure water and alkaline cleaning solutions. Examples of alkaline cleaning solutions include aqueous solutions of one or more anhydrides or hydrates selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and ammonium carbonate. Ammonia can also be used as the alkali.

[0111] The resulting slurry contains a solid component mainly containing the positive electrode active material after heating and a liquid component containing water-soluble components other than the positive electrode active material, including an alkali metal component derived from the activation treatment agent and / or a fluorine component derived from the binder and the electrolyte.

[0112] The amount of liquid to be brought into contact with the mixture is appropriately determined taking into consideration the amounts of the post-heating positive electrode active material and water-soluble components other than the positive electrode active material contained in the mixture.

[0113] In step (3a), it is preferable to obtain a slurry by stirring the heated mixture with a liquid containing water. This promotes dissolution of the water-soluble components. The peripheral speed of the tip of the stirring blade is preferably 0.1 to 0.9 m / s.

[0114] The slurry obtained in the slurrying step is then subjected to solid-liquid separation. Solid-liquid separation is an operation for separating the slurry into a liquid component and a solid component. The solid-liquid separation method may be a conventionally known method, such as filtration or centrifugation.

[0115] In step (3a), after solid-liquid separation, the obtained solid component may be rinsed. Rinsing is an operation in which the obtained solid component is again brought into contact with a liquid containing water to obtain a slurry, and then the slurry is separated again into a solid component and a liquid component. In step (3a), rinsing may be performed multiple times. The slurry concentration in the rinse may also be the same as the slurry concentration in the solid-liquid separation step.

[0116] Step (3b): Drying Step Step (3b) is a step of removing water from the solid component obtained in step (3a) by, for example, heating and / or exposing the solid component to a reduced pressure environment.

[0117] The heating temperature in the drying step is preferably 100°C or higher to remove water. Furthermore, 150°C or higher is preferable to thoroughly remove water. Temperatures of 250°C or higher are particularly preferable because they further increase the discharge capacity of a battery manufactured using the resulting positive electrode active material. The temperature in the drying step may be constant or may be changed stepwise or continuously. The temperature range reached by heating can be, for example, 10°C or higher and lower than 900°C.

[0118] The ultimate pressure range of the reduced pressure is, for example, 1.0 x 10 －１０ ~1.0 x 10 ３ Pa.

[0119] Step (3c): Annealing Step Step (3c) is a step of heating the mixture after heating (or the solid component obtained in step (3a) or the solid component obtained in step (3b)) at a temperature higher than that in step (2).

[0120] The temperature to which the mixture after heating in the annealing step is heated may be greater than 700°C, 750°C or higher, 800°C or higher, 850°C or higher, or 900°C or higher, from the viewpoint of vaporizing components other than the positive electrode active material and removing impurities, and from the viewpoint of making the crystallite size of the positive electrode active material sufficiently large, thereby more easily achieving charge / discharge characteristics comparable to those of a battery produced using unused positive electrode active material.

[0121] The temperature to which the heated mixture is heated in the annealing step may be equal to or higher than the melting temperature of the activation treatment agent, from the viewpoint of making it easier to achieve charge / discharge characteristics comparable to those of a battery manufactured using an unused positive electrode active material by sufficiently increasing the crystallite size of the positive electrode active material. In the annealing step, the heated mixture may be heated at a temperature that is 20°C or higher, 30°C or higher, 40°C or higher, 50°C or higher, 100°C or higher, 150°C or higher, or 200°C or higher than the melting temperature of the activation treatment agent.

[0122] The temperature to which the mixture after heating in the annealing step is heated may be 1500°C or lower, 1400°C or lower, 1300°C or lower, 1200°C or lower, 1000°C or lower, or 950°C or lower, from the viewpoint of suppressing thermal deterioration of the positive electrode active material and making it easier to achieve charge / discharge characteristics comparable to those of a battery produced using an unused positive electrode active material.

[0123] The heating temperature in step (2) is T １ The heating temperature in step (3) is T ２ When T ２ / T １ may be 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, or 2 or more, from the viewpoint of more easily achieving charge / discharge characteristics comparable to those of a battery produced using an unused positive electrode active material; and from the same viewpoint, may be 2.5 or less, 2.4 or less, 2.3 or less, or 2.2 or less.

[0124] The heating temperature in step (2) is T １ The heating temperature in step (3) is T ２ When T ２ -T １ From the viewpoint of more easily achieving charge / discharge characteristics comparable to those of a battery produced using an unused positive electrode active material, the temperature may be 250°C or higher, 300°C or higher, 350°C or higher, 400°C or higher, 450°C or higher, or 500°C or higher; from the same viewpoint, the temperature may be 1000°C or lower, 800°C or lower, 700°C or lower, 600°C or lower, or 500°C or lower.

[0125] In the annealing step, the atmosphere for the heat treatment is not particularly limited, but it is preferably an oxygen-containing atmosphere such as air. The holding time for the heat treatment can be 1 minute to 24 hours. In particular, it is preferable to heat at a temperature higher than that in step (2) for 0.1 to 5 hours.

[0126] The recycled cathode active material obtained from the battery mixture by using the method for producing the recycled cathode active material of the present disclosure can be used in the same way as a virgin cathode active material. The method for producing a cathode and a battery using the recycled cathode active material is similar to the method for producing a cathode and a battery using a virgin cathode active material and is well known.

[0127] The charge / discharge characteristics of a battery manufactured using a cathode active material obtained by the method for producing a recycled cathode active material according to an embodiment of the present disclosure are comparable to those of a battery manufactured using an unused cathode active material. Specifically, for example, when a battery manufactured using a cathode active material obtained by the method for producing a recycled cathode active material according to an embodiment is subjected to constant-current charging at a current value of 0.2 C up to a maximum charging voltage of 4.3 V in an environment of 25° C., the recyclability of the initial charge capacity (initial charge capacity of a battery manufactured using a recycled cathode active material / initial charge capacity of a battery manufactured using an unused cathode active material) is 0.98 to 1.02, which is comparable to the initial charge capacity of a battery manufactured using an unused cathode active material. Furthermore, when a battery manufactured using the positive electrode active material obtained by the manufacturing method for recycled positive electrode active material according to one embodiment is subjected to constant current discharge at a current value of 0.2 C to a minimum discharge voltage of 2.5 V in an environment of 25° C., the recyclability of the initial discharge capacity (initial discharge capacity of battery manufactured using recycled positive electrode active material / initial discharge capacity of battery manufactured using unused positive electrode active material) is 0.9 to 1.1, which is equivalent to the initial charge capacity of a battery manufactured using unused positive electrode active material.

[0128] In this specification, a positive electrode active material that has undergone steps (1) to (3) is referred to as a recycled positive electrode active material. The recycled positive electrode active material that has undergone steps (1) to (3) can be suitably used in the production of a positive electrode or the like. The method for producing a recycled positive electrode active material may include additional steps before and after steps (1) to (3). In this specification, a positive electrode active material that has undergone additional steps other than steps (1) to (3) is also referred to as a recycled positive electrode active material. Examples of additional steps other than steps (1) to (3) are pre-steps (A) and (B) that are performed before step (1).

[0129] The present disclosure will be described in more detail below using examples, but the present disclosure is not limited to the following examples as long as the gist of the disclosure is not changed.

[0130] <Production of Positive Electrode> The positive electrode described below was produced by the following procedure. A mixture was obtained by mixing 90 parts by mass of a positive electrode active material (unused positive electrode active material or recycled positive electrode active material), 3 parts by mass of a binder (manufactured by Kureha Corporation, product number: PVdF #1100), and 7 parts by mass of carbon black (conductive material, manufactured by Denka Co., Ltd., product number: HS100). As the binder PVdF, a binder solution prepared by dissolving PVdF in NMP (N-methyl-2-pyrrolidone) was used. The mixture was kneaded in an agate mortar to prepare a positive electrode composite paste. NMP was added so that the total mass of the positive electrode active material, binder, and conductive material in the positive electrode composite paste was 52% by mass.

[0131] A 20 μm thick aluminum foil 1085 (manufactured by Nippon Foil Co., Ltd.) for a lithium ion secondary battery positive electrode current collector was applied on one side thereof with a positive electrode active material amount of 10.0±0.2 mg / cm ２ The positive electrode composite paste was applied so that the positive electrode composite paste was 1.65 cm2, and then vacuum dried at 150°C for 8 hours to obtain a positive electrode. ２ It was.

[0132] <Battery Manufacturing> The coin-type battery described below was fabricated by the following procedure. The above-mentioned positive electrode, electrolyte, separator, and negative electrode were combined to fabricate a coin-type battery (non-aqueous electrolyte secondary battery). The battery was assembled in a glove box under an argon atmosphere. The electrolyte was a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate, with LiPF ６ A solution of 1.0 mol / L of the above was used. A laminated film separator was used as the separator, in which a heat-resistant porous layer was laminated on a porous film (made of polyethylene). Metallic lithium was used as the negative electrode.

[0133] <Production of Positive Electrode Before Recycling> As a positive electrode active material, １．０５ Ni ０．３４ Co ０．３３ Mn ０．３３ O ２ A positive electrode active material NCM111 having a crystal structure of R-3m was prepared. The rated capacity of this positive electrode active material was 160 mAh / g, and the 1C current was 160 mA / g. The above coin-type battery was produced using this positive electrode active material (unused positive electrode active material), and initial charge / discharge was performed under the following conditions while maintaining the temperature at 25°C. The initial charge capacity was 178.1 mAh / g, and the initial discharge capacity was 163.1 mAh / g. (Conditions) Maximum charge voltage: 4.3 V, charge current: 0.2 C, constant current / constant voltage charge Minimum discharge voltage: 2.5 V, discharge current: 0.2 C, constant current discharge

[0134] (Example 1) The electrode mixture was mechanically scraped off from the cathode of the process waste material generated when the above-mentioned cathode was produced, and the electrode mixture was peeled off from the current collector. 30 g of the electrode mixture removed from the cathode was treated with an activation treatment agent in a ratio of 10 mol of Li per 100 mol of the cathode active material. ２ CO ３ and 10 mol of Na relative to 100 mol of the positive electrode active material. ２ SO ４ The activation treatment agent had a melting point of 510°C.

[0135] 30 g of the mixture before heating was placed in an electric furnace and heated in an air atmosphere at a temperature increase rate of 300°C / h, a heating temperature of 450°C (lower than the melting start temperature of the activation treatment agent), and a heating time of 360 minutes.

[0136] The heated mixture was pulverized, and distilled water was added and stirred to obtain a slurry. The obtained slurry was filtered to separate a solid component and a liquid component. The solid component was then recovered and dried under reduced pressure at 100°C for 1 hour.

[0137] The dried solid component was placed in an electric furnace and heated in an air atmosphere at 700 ° C for 60 minutes to obtain a recycled cathode active material. The heated recycled cathode active material was then allowed to cool naturally to room temperature (20 ° C), and it was confirmed that the composition, crystalline structure, average particle size, and specific surface area of ​​the resulting recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and subjected to initial charge / discharge under the above conditions at 25 ° C. The initial charge capacity was 178.5 mAh / g, and the initial discharge capacity was 160.0 mAh / g.

[0138] Example 2 A recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature at which the dried solid component was heated was changed to 900°C. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. The above-mentioned coin-type battery was produced using the recycled cathode active material, and the initial charge / discharge was performed under the above-mentioned conditions while maintaining the battery at 25°C. The initial charge capacity was 180.5 mAh / g, and the initial discharge capacity was 161.1 mAh / g.

[0139] Example 3 A recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature at which the dried solid component was heated was changed to 950°C. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 180.4 mAh / g, and the initial discharge capacity was 160.8 mAh / g.

[0140] Example 4: 10 mol of Na was used as an activation treatment agent relative to 100 mol of the positive electrode active material. ２ CO ３ A recycled positive electrode active material was obtained in the same manner as in Example 2, except that 10 g of the electrode mixture removed from the positive electrode was mixed with an activation treatment agent using a sintered body (melting initiation temperature: 851°C) to obtain a pre-heated mixture. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled positive electrode active material were comparable to those of unused positive electrode active material. A coin-type battery was fabricated using the recycled positive electrode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 180.4 mAh / g, and the initial discharge capacity was 159.7 mAh / g.

[0141] Example 5 A recycled cathode active material was obtained in the same manner as in Example 4, except that the temperature at which the dried solid component was heated was changed to 950°C. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 180.7 mAh / g, and the initial discharge capacity was 159.5 mAh / g.

[0142] Example 6: 10 mol of K was used as an activation treatment agent relative to 100 mol of the positive electrode active material. ２ CO ３ A recycled positive electrode active material was obtained in the same manner as in Example 2, except that 10 g of the electrode mixture removed from the positive electrode was mixed with an activation treatment agent using a sintered body (melting initiation temperature: 891°C) to obtain a pre-heated mixture. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled positive electrode active material were comparable to those of unused positive electrode active material. A coin-type battery was fabricated using the recycled positive electrode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 174.0 mAh / g, and the initial discharge capacity was 157.1 mAh / g.

[0143] Example 7 A recycled cathode active material was obtained in the same manner as in Example 6, except that the temperature at which the dried solid component was heated was changed to 950°C. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 174.4 mAh / g, and the initial discharge capacity was 157.0 mAh / g.

[0144] Comparative Example 1 A recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature at which the mixture was heated before heating was changed to 700°C (above the melting initiation temperature). The composition, crystalline structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 172.2 mAh / g, and the initial discharge capacity was 155.9 mAh / g.

[0145] Comparative Example 2: A recycled cathode active material was obtained in the same manner as in Example 2, except that the temperature at which the mixture was heated before heating was changed to 700°C (above the melting initiation temperature). The composition, crystalline structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and subjected to initial charge / discharge under the above conditions while maintained at 25°C. The initial charge capacity was 172.8 mAh / g, and the initial discharge capacity was 155.9 mAh / g.

[0146] <Production of Positive Electrode Before Recycling> As a positive electrode active material, １．１８ Ni ０．３４ Co ０．３３ Mn ０．３３ O ２A positive electrode active material NCM111 having a crystal structure of R-3m was prepared. The rated capacity of this positive electrode active material was 160 mAh / g, and the 1C current was 160 mA / g. The above coin-type battery was produced using this positive electrode active material (unused positive electrode active material), and initial charge / discharge was performed under the following conditions while maintaining the temperature at 25°C. The initial charge capacity was 168.9 mAh / g, and the initial discharge capacity was 156.0 mAh / g. (Conditions) Maximum charge voltage: 4.3 V, charge current: 0.2 C, constant current / constant voltage charge Minimum discharge voltage: 2.5 V, discharge current: 0.2 C, constant current discharge

[0147] (Example 8) The electrode mixture was mechanically scraped off from the cathode of the process waste material generated when the above cathode was produced, and the electrode mixture was peeled off from the current collector. 5 g of the electrode mixture removed from the cathode was treated with an activation treatment agent in a concentration of 10 mol of Li per 100 mol of the cathode active material. ２ CO ３ and 10 mol of Na relative to 100 mol of the positive electrode active material. ２ SO ４ The activation treatment agent had a melting point of 510°C.

[0148] 40 g of the mixture before heating was placed in an electric furnace and heated in an air atmosphere at a temperature increase rate of 300°C / h, a heating temperature of 500°C (below the melting point of the activation treatment agent), and a heating time of 60 minutes. The air flow rate was 0.5 L / min, and the gas-powder ratio was 5.8 m ３ / kg.

[0149] The heated mixture was pulverized, and distilled water was added and stirred to obtain a slurry. The obtained slurry was filtered to separate a solid component and a liquid component. The solid component was then recovered and dried under reduced pressure at 100°C for 1 hour.

[0150] The dried solid component was placed in an electric furnace and heated in an air atmosphere at a temperature of 900 ° C for 360 minutes to obtain a recycled cathode active material. The heated recycled cathode active material was then allowed to cool naturally to room temperature (20 ° C), and it was confirmed that the composition, crystalline structure, average particle size, and specific surface area of ​​the resulting recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and subjected to initial charge / discharge under the above conditions at 25 ° C. The initial charge capacity was 171.9 mAh / g, and the initial discharge capacity was 153.0 mAh / g.

[0151] (Example 9) When heating the mixture before heating, the air flow rate was 1 L / min and the gas-powder ratio was 11.5 m ３ A recycled positive electrode active material was obtained in the same manner as in Example 8, except that the amount of the recycled positive electrode active material was changed to 1 / kg. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled positive electrode active material were comparable to those of the unused positive electrode active material. A coin-type battery was fabricated using the recycled positive electrode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 170.2 mAh / g and the initial discharge capacity was 151.2 mAh / g.

[0152] (Comparative Example 3) The amount of the mixture before heating was 20 g, the temperature at which the mixture before heating was heated was 700°C, the heating time was 360 minutes, the air flow rate was 0.85 L / min, and the gas-powder ratio was 28.7 m ３ A recycled positive electrode active material was obtained in the same manner as in Example 8, except that the amount of the recycled positive electrode active material was changed to 1 / kg. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled positive electrode active material were comparable to those of the unused positive electrode active material. A coin-type battery was fabricated using the recycled positive electrode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 167.6 mAh / g and the initial discharge capacity was 138.9 mAh / g.

[0153] Comparative Example 4 A recycled cathode active material was obtained in the same manner as in Example 8, except that the temperature at which the dried solid component was heated was changed to 950°C. The composition, crystal structure, average particle size, and specific surface area of ​​the obtained recycled cathode active material were comparable to those of an unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material and initially charged and discharged under the above conditions at 25°C. The initial charge capacity was 170.1 mAh / g, and the initial discharge capacity was 135.7 mAh / g.

[0154] The heating temperature of the mixture before heating in each example and each comparative example (T １ ), the heating temperature of the solid component after drying (T ２ ), the ratio of the heating temperature of the solid component after drying to the heating temperature of the mixture before heating (T ２ / T １ ), the difference between the heating temperature of the mixture before heating and the heating temperature of the solid component after drying (T ２ -T １ ), the measured initial charge capacity and the recycling degree, and the measured initial discharge capacity and the recycling degree are shown in Tables 1 and 2, respectively.

[0155]

[0156]

Claims

1. A method for producing recycled cathode active material, comprising the steps of: (1) A step of mixing a cathode composite containing a cathode active material with an activation treatment agent containing one or more alkali metal compounds to obtain a mixture; (2) A step of heating the mixture to a temperature below the melting start temperature of the activation treatment agent to obtain a heated mixture; and (3) A step of recovering the heated cathode active material from the heated mixture.

2. The method according to claim 1, wherein in step (3), the heated mixture is heated at a temperature higher than that in step (2), and the heated positive electrode active material is recovered.

3. The method of claim 1, wherein the positive electrode active material comprises a lithium compound.

4. The manufacturing method according to claim 1, wherein the positive electrode active material comprises a composite oxide containing at least one element selected from the following element group 1 and at least one element selected from the following element group 2. Element group 1: Ni, Co, Mn, Fe, Al, and P Element group 2: Li, Na, K, Ca, Sr, Ba, and Mg 5. The method of claim 1, wherein the activation treatment agent contains at least one compound selected from the group consisting of potassium compounds and sodium compounds.

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