Method for manufacturing recycled positive electrode active material

Abstract

To provide a method for producing a recycled cathode active material capable of making the rate characteristics of a battery produced using the recycled cathode active material more comparable to those of a battery produced using an unused cathode active material than before. 【Solution means】A method for producing a recycled cathode active material including the following steps. (1) A step of mixing a cathode composite material containing a cathode active material and an activation treatment agent containing one or more alkali metal compounds to obtain a mixture (2) A step of heating the mixture at a temperature of T °C to obtain a heated mixture (3) A step of heating the heated mixture at a temperature of (1.6 × T) °C or higher and recovering the heated cathode active material

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a recycled cathode active material.

Background Art

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

[0003] For example, Patent Document 1 discloses a method of mixing a cathode composite material and an activation treatment agent containing an alkali metal compound, heating the mixture to decompose the binder, and removing the decomposition product and the activation treatment agent with water or the like to recover the cathode active material. This method is excellent in cost in that the cathode active material is directly recovered from battery waste materials without using an organic solvent.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] When recycling the cathode active material, there is still room for further improvement in the rate characteristics of a battery manufactured using the recycled cathode active material.

[0006] Therefore, an object of the present invention is to provide a method for manufacturing a recycled cathode active material capable of making the rate characteristics of a battery manufactured using the recycled cathode active material further equivalent to those of a battery manufactured using an unused cathode active material.

Means for Solving the Problems

[0007] The present invention includes, for example, the following [1] to [6]. [1] A method for producing a recycled cathode active material including the following steps. (1) A step of mixing a cathode composite material containing a cathode active material and an activation treatment agent containing one or more alkali metal compounds to obtain a mixture (2) A step of heating the mixture at a temperature of T °C to obtain a heated mixture (3) A step of heating the heated mixture at a temperature of (1.6 × T) °C or higher and recovering the heated cathode active material [2] A method for producing a recycled cathode active material including the following steps. (1) A step of mixing a cathode composite material containing a cathode active material and an activation treatment agent containing one or more alkali metal compounds to obtain a mixture (2) A step of heating the mixture at a temperature of T °C to obtain a heated mixture (3) A step of heating the heated mixture at a temperature of (T + 300) °C or higher and recovering the heated cathode active material [3] The production method according to [1] or [2], wherein in the step (2), the temperature T is less than the melting start temperature. [4] The production method according to any one of [1] to [3], wherein the cathode active material contains a lithium compound. [5] The production method according to any one of [1] to [4], wherein the cathode active material 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 [6] The production method according to any one of [1] to [5], wherein the activation treatment agent contains at least one compound selected from the group consisting of potassium compounds and sodium compounds.

Advantages of the Invention

[0008] According to the present invention, there can be provided a method for producing a recycled positive electrode active material capable of further making the rate characteristics of a battery produced using the recycled positive electrode active material comparable to those of a battery produced using an unused positive electrode active material.

Embodiments for Carrying Out the Invention

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

[0010] The method for producing a recycled positive electrode active material according to an embodiment of the present invention includes the following steps. Step (1): A step of mixing a positive electrode composite material containing a positive electrode active material and an activation treatment agent containing one or more alkali metal compounds to obtain a mixture Step (2): A step of heating the mixture at a temperature of T °C to obtain a heated mixture Step (3): A step of heating the heated mixture at a temperature of (1.6 × T) °C or higher and recovering the heated positive electrode active material

[0011] The method for producing a recycled positive electrode active material according to an embodiment heats a mixture of a positive electrode composite material and an activation treatment agent, and then heats the heated mixture at a temperature somewhat higher than the temperature at which the mixture of the positive electrode composite material and the activation treatment agent was heated, and recovers the heated positive electrode active material. As a result of investigations by the present inventors, it has been found that by heating the heated mixture at a temperature somewhat higher than the temperature at which the mixture of the positive electrode composite material and the activation treatment agent was heated, the rate characteristics of a battery produced using the recycled positive electrode active material can be made more comparable to those of a battery produced using an unused positive electrode active material. The reason for this is speculated by the present inventors as follows. That is, by heating the mixture of the positive electrode composite material and the activation treatment agent and then heating the heated mixture at a temperature somewhat higher than the temperature at which the mixture of the positive electrode composite material and the activation treatment agent was heated, it becomes possible to sufficiently increase the crystallite size of the positive electrode active material, and the rate characteristics can be improved. However, the mechanism of the present invention is not limited to the above.

[0012] The following will explain each step in detail.

[0013] Previous step (A): Cathode composite material preparation step First, prepare a cathode composite material containing a cathode active material.

[0014] [Cathode active material] Examples of cathode active materials include composite compounds containing one or more of 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. as constituent elements.

[0015] The cathode active material may consist of only a single compound or may be composed of multiple compounds.

[0016] The cathode active material preferably includes 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

[0017] The cathode active material preferably includes a compound represented by the following formula (A).

[0018] 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 1represents 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, -0.4 < a < 1.5, 0 ≤ b < 0.5, 0 ≤ c < 0.5, -0.5 < d < 1.5, and 0 ≤ e < 0.5 are satisfied.

[0019] M T is 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, N, etc.

[0020] The positive electrode active material preferably contains a composite oxide containing at least Li and Ni.

[0021] In the positive electrode active material, the molar fraction of Ni in M 1 is preferably 0.3 to 0.95.

[0022] The crystal structure of the positive electrode active material (for example, the composite oxide) is not particularly limited, but a layered structure is preferred, and a hexagonal or monoclinic crystal structure is more preferred.

[0023] 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 P65 , 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 It belongs to any one space group selected from the group consisting of / mmc.

[0024] The crystal structure of the monoclinic form is P2, P2 1 , C2, Pm, Pc, Cm, Cc, P2 / m, P2 1 / m, C2 / m, P2 / c, P2 1 / c, and C2 / c.

[0025] The crystal structure of the positive electrode active material preferably belongs to the space group R-3m included in the hexagonal crystal structure or C2 / m included in the monoclinic crystal structure.

[0026] The crystal structure of the positive electrode active material can be identified from the powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement using CuKα rays as the radiation source.

[0027] The particle size of the positive electrode active material in the positive electrode composite material is not particularly limited, but may be about 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 measuring device (for example, Master Sizer 2000 manufactured by Malvern). A cumulative particle size distribution curve based on volume can be created from the particle size distribution, and the value of the particle size (D50) at 50% cumulative from the fine particle side can be taken as the average particle size of the positive electrode active material.

[0028] There is no particular limitation on the content of the positive electrode active material in the positive electrode composite material.

[0029] [Binder] The positive electrode composite material may contain a binder. When the positive electrode composite material contains a binder, the particles of the positive electrode active material may be bound to each other by the binder.

[0030] Examples of the binder (binder before activation treatment) contained in the positive electrode composite material include thermoplastic resins, etc. Specifically, polyvinylidene fluoride (hereinafter sometimes referred to as "PVdF"), polytetrafluoroethylene (PTFE), tetrafluoroethylene - hexafluoropropylene - vinylidene fluoride copolymer, hexafluoropropylene - vinylidene fluoride copolymer, tetrafluoroethylene - perfluorovinyl ether copolymer and other fluororesins; polyolefin resins such as polyethylene and polypropylene; styrene - butadiene copolymer (SBR), etc. The binder may be used alone or in combination of two or more.

[0031] The content of the binder in the positive electrode composite material is not particularly limited, but may be in the following range with respect to 100 parts by mass of the positive electrode active material. The content of the binder may be 0.5 part 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 viewpoints, 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.

[0032] [Conductive material] The positive electrode composite material may contain a conductive material and / or an electrolyte. When the positive electrode composite material 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 composite material may contain a fluorine compound derived from a binder and / or an electrolytic solution (for example, an electrolyte in the electrolytic solution).

[0033] Examples of the conductive material include metal - based conductive materials such as metal particles; carbon - based conductive materials made of carbon materials, etc.

[0034] Specific examples of the carbon-based conductive material include graphite powder (graphite), carbon black (e.g., acetylene black), fibrous carbon materials (e.g., graphitized carbon fibers and carbon nanotubes), and the like.

[0035] The carbon-based conductive material may be a single carbon material or may be composed of a plurality of carbon materials.

[0036] The specific surface area of the carbon material used as the carbon-based conductive material may be 0.1 to 500 m 2 / g. In that case, the conductive material can consist only of a carbon-based conductive material with a specific surface area of 30 m 2 / g or more, and may be carbon black with a specific surface area of 30 m 2 / g or more, or may be acetylene black with a specific surface area of 30 m 2 / g or more. When using the activation treatment agent described later containing an alkali metal compound having oxidizing power, the oxidation treatment rate of the carbon-based conductive material can be increased, and there are cases where even a carbon material with a small specific surface area can be oxidized.

[0037] The content of the conductive material in the positive electrode composite material is not particularly limited, but may be in the following range with respect 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 viewpoints, 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.

[0038] [Electrolyte and Solvent] The electrolyte is a component that is derived from the battery electrolyte and impregnates the positive electrode composite material. Examples of the electrolyte include LiPF 6 , LiBF 4 , LiClO 4 , LiN(SO 2 CF 3 ) 2 , LiN(SO 2F) 2 and LiCF 3 SO 3 etc. can be mentioned. The content of the electrolyte contained in the positive electrode composite material is not particularly limited, but may be 0.0005 to 7% by mass.

[0039] The positive electrode composite material may contain a solvent derived from the electrolytic solution. Examples of the solvent include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc.

[0040] [Recovery of positive electrode composite material] The positive electrode composite material can be obtained by separating and recovering the positive electrode composite material layer from the waste positive electrode having a current collector and a positive electrode composite material layer.

[0041] The "waste positive electrode" may be a positive electrode recovered from a discarded battery, and waste of the positive electrode generated during the production process of the positive electrode or the battery. The discarded battery may be a used battery, or a battery that is unused but out-of-specification. The waste of the positive electrode may be the end of the positive electrode generated in the battery manufacturing process, or an out-of-specification positive electrode. As the positive electrode composite material, waste products of the positive electrode composite material not attached to the current collector (waste products generated in the positive electrode composite material manufacturing process) can also be used.

[0042] The waste positive electrode has a current collector that is a metal foil such as aluminum foil or copper foil, and a positive electrode composite material layer provided on the current collector. The positive electrode composite material layer may be provided on one side of the current collector or on both sides.

[0043] Examples of the method for separating the positive electrode composite material layer from the waste positive electrode having a current collector and a positive electrode composite material layer include a method of mechanically peeling the positive electrode composite material layer from the current collector (for example, a method of scraping off the positive electrode composite material layer from the current collector), a method of peeling the positive electrode composite material layer from the current collector by infiltrating a solvent into the interface between the current collector and the positive electrode composite material layer, a method of dissolving the current collector using an alkaline or acidic aqueous solution to separate the positive electrode composite material layer, etc. Preferably, it is a method of mechanically peeling the positive electrode composite material layer from the current collector.

[0044] Previous step (B): Cleaning step of the positive electrode composite material Subsequently, when the positive electrode composite material contains an electrolyte, it is preferable to bring the prepared positive electrode composite material into contact with an electrolyte washing solvent to remove at least a part of the electrolyte from the positive electrode composite material. Specifically, a positive electrode active material and a positive electrode composite material containing an electrolyte are brought into contact with an electrolyte washing solvent to obtain a slurry containing a solid component and a liquid component, and then the slurry is separated into the solid component and the liquid component.

[0045] Solid-liquid separation is an operation of separating a slurry into a solid component and a liquid component. Examples of the method of solid-liquid separation may be conventionally known methods, and include filtration, centrifugation, and the like.

[0046] There is no particular limitation on the electrolyte washing solvent. Examples of the electrolyte washing 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.

[0047] Contacting the positive electrode composite material with the electrolyte washing solvent can be performed using a known contact device for powder and liquid (for example, a stirring tank).

[0048] In the step of bringing the positive electrode composite material into contact with the electrolyte washing solvent, it is preferable to stir the positive electrode composite material and the electrolyte washing solvent to obtain a slurry. The peripheral speed of the tip of the stirring blade may be 0.1 to 1.0 m / s.

[0049] In the washing step of the positive electrode composite material, after solid-liquid separation, rinsing of the solid component may be performed. Rinsing is an operation of bringing the electrolyte washing solvent into contact with the solid component again to obtain a slurry and then separating the slurry into the solid component and the liquid component again. In the washing step of the positive electrode composite material, rinsing may be performed a plurality of times. The slurry concentration in rinsing can be arbitrarily adjusted. Also in rinsing, the slurry can be stirred as described above.

[0050] The electrolyte can be sufficiently removed from the positive electrode composite material by the above washing. For example, if the electrolyte remains, the following reaction may occur, and the structure of the positive electrode active material may change from a layered rock salt structure to a spinel structure. LiPF 6 +16LiMO 2 +2O 2 → 6LiF+Li 3 PO 4 +8LiM 2 O 4

[0051] In addition, when the activation treatment agent contains lithium carbonate, lithium consumption may occur due to the following reaction. LiPF 6 +4Li 2 CO 3 → 6LiF+Li 3 PO 4 +4CO 2

[0052] For the separated solid component, if necessary, the electrolyte washing solvent can be dried by reducing the pressure and / or heating. The heating temperature may be 50 to 200 °C.

[0053] Step (1): Activation treatment agent mixing step Next, the prepared positive electrode composite material and an activation treatment agent containing one or more alkali compounds are mixed to obtain a mixture.

[0054] The mixing method of the positive electrode composite material and the activation treatment agent may be either dry mixing or wet mixing, or a combination of these mixing methods. The mixing order of the positive electrode composite material and the activation treatment agent is not particularly limited.

[0055] When mixing, it is preferable to go through a step of pulverizing and mixing using a mixing device equipped with a mixing medium such as balls, thereby improving the mixing efficiency.

[0056] As a mixing method, dry mixing is preferred in that mixing can be performed more simply. In dry mixing, a V-type mixer, a W-type mixer, a ribbon mixer, a drum mixer, a powder mixer equipped with stirring blades inside, a ball mill, a vibration mill, or a combination of these devices can be used.

[0057] As a mixing device used for dry mixing, a powder mixer equipped with stirring blades inside is preferred, and specifically, a Lodige mixer (manufactured by Matsubo Corporation) can be mentioned.

[0058] Hereinafter, the activating agent used in this step will be described in detail.

[0059] <Activating agent> The activating agent contains one or more alkali metal compounds. The activating 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 an alkali metal element X. The activating agent may contain an alkali metal compound containing another alkali metal such as Li in addition to the potassium compound and / or the sodium compound.

[0060] When the activating 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 activating agent particularly contains a molten part, the contact property between the molten part and the positive electrode active material is improved, so that the activation of the positive electrode active material is further promoted.

[0061] In addition, the positive electrode composite material may contain a compound containing fluorine derived from a binder and / or an electrolytic solution. By bringing the compound containing fluorine into contact with the activating agent, the fluorine component is stabilized as an alkali metal fluoride, so that the generation of corrosive gases such as hydrogen fluoride can be suppressed. Since hydrogen fluoride reduces the activity of the positive electrode active material, it is also desirable to prevent its generation.

[0062] The proportion of the total alkali metal compound in the activation treatment agent is appropriately set in consideration of the type of the alkali metal compound, the type of the target positive electrode active material, etc. Usually, it is 50% by mass or more, preferably 70% by mass or more, based on the total mass of the activation treatment agent, and may be 100% by mass (in the case where the activation treatment agent consists of an alkali metal compound in practice).

[0063] The concentration of at least one alkali metal selected from the group consisting of potassium and sodium in the alkali metal contained in the alkali metal compound can be arbitrarily adjusted within 0 to 100 mol%, preferably 10 mol% or more, more preferably 20 mol% or more, preferably 90 mol% or less, and more preferably 80 mol% or less.

[0064] Examples of the alkali metal compound that becomes a component 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 alone or in combination as components of the activation treatment agent.

[0065] 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 and other borates; Li 2 CO 3 、Na 2 CO 3 、K 2 CO 3 、RbCO 3 、CsCO 3 and other carbonates; Li 2 O、Na 2 O、K 2 O、Rb 2 O、Cs 2 O and other oxides; Li2 O 2 、 Na 2 O 2 、 K 2 O 2 、 Rb 2 O 2 、 Cs 2 O 2 and other peroxides; LiO 2 、 NaO 2 、 KO 2 、 RbO 2 、 CsO 2 and other superoxides; LiNO 3 、 NaNO 3 、 KNO 3 、 RbNO 3 、 CsNO 3 and other nitrates; Li 3 PO 4 、 Na 3 PO 4 、 K 3 PO 4 、 Rb 3 PO 4 、 Cs 3 PO 4 and other phosphates; Li 2 SO 4 、 Na 2 SO 4 、 K 2 SO 4 、 Rb 2 SO 4 、 Cs 2 SO 4 and other sulfates; Chlorides such as LiCl, NaCl, KCl, RbCl, CsCl; Bromides such as LiBr, NaBr, KBr, RbBr, CsBr; LiVO 3 、 NaVO 3 、 KVO 3 、 RbVO 3 、 CsVO 3 and other vanadates; Li 2 MoO 4 、 Na 2 MoO 4 、 K 2 MoO4 , Rb 2 MoO 4 , CsMoO 4 and other molybdates; and Li 2 WO 4 , Na 2 WO 4 , K 2 WO 4 , Rb 2 WO 4 , CsWO 4 and other tungstates; may be mentioned.

[0066] Here, in order to enhance the activation effect of the positive electrode active material, in addition to at least one compound selected from the group consisting of potassium compounds and sodium compounds, the activation treatment agent may contain the same alkali metal element as the alkali metal element contained in the positive electrode active material in the positive electrode composite material.

[0067] That is, when the positive electrode active material in the positive electrode composite material is a lithium composite oxide, it is preferable that the activation treatment agent 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 PO 4 , Li 2 SO 4 , LiCl, LiVO 3 , LiBr, Li 2 MoO 4 , and Li 2 WO 4 may be mentioned.

[0068] The activating agent may contain a compound other than an alkali metal compound, if necessary. Examples of the compound other than the alkali metal compound 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 activating agent together with the alkali metal compound for the purpose of controlling the melting start temperature of the activating agent.

[0069] In addition, the content of the compound other than the alkali metal compound in the activating 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% by mass based on the total mass of the activating agent.

[0070] The addition amount of the activating agent in the mixture of the positive electrode composite material and the activating agent is preferably 0.001 to 100 times, more preferably 0.05 to 1 times, based on the mass of the positive electrode active material contained in the positive electrode composite material.

[0071] When the activating agent contains a potassium compound and a lithium compound, the ratio of the lithium content (mol basis) to the potassium content (mol basis) (lithium content / potassium content) is 0.01 to 100, 0.1 to 10, or 0.2 to 4 from the viewpoint of making the charge and discharge characteristics of the battery manufactured using the recycled positive electrode active material closer to those of the battery manufactured using the unused positive electrode active material.

[0072] When the activating agent contains a sodium compound and a lithium compound, the ratio of the lithium content (mol basis) to the sodium content (mol basis) (lithium content / sodium content) is 0.01 to 100, 0.1 to 10, or 0.2 to 4 from the viewpoint of making the charge and discharge characteristics of the battery manufactured using the recycled positive electrode active material closer to those of the battery manufactured using the unused positive electrode active material.

[0073] When the activating agent contains a potassium compound, the content of potassium contained in the activating agent (in terms of moles) is 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% with respect to the content of fluorine contained in the positive electrode composite material (in terms of moles), from the viewpoint of making the charge-discharge characteristics of the battery manufactured using the recycled positive electrode active material closer to the charge-discharge characteristics of the battery manufactured using the unused positive electrode active material.

[0074] When the activating agent contains a sodium compound, the content of sodium contained in the activating agent (in terms of moles) is 1 to 200%, 10 to 200%, 50 to 200%, or 100 to 200%, 1% or more and less than 150%, 10% or more and less than 150%, 50% or more and less than 150%, or 100% or more and less than 150% with respect to the content of fluorine contained in the positive electrode composite material (in terms of moles), from the viewpoint of making the charge-discharge characteristics of the battery manufactured using the recycled positive electrode active material closer to the charge-discharge characteristics of the battery manufactured using the unused positive electrode active material.

[0075] The number of moles of the alkali metal compound in the activating agent in the mixture of the positive electrode composite material and the activating agent can be added so that the number of moles of the alkali metal element is 0.001 to 200 times when the number of moles of the positive electrode active material (for example, formula A) contained in the positive electrode composite material is 1.

[0076] By appropriately controlling the ratio of the activating agent in the mixture, the cost for recovering the positive electrode active material from the positive electrode composite material can be reduced, the oxidation decomposition rate of the carbon-based conductive material and the binder can be increased. Also, the effect of preventing the generation of corrosive gas in the heating process can be improved, and furthermore, the discharge capacity of the battery manufactured using the obtained positive electrode active material can be increased more.

[0077] Further, at least one of the alkali metal compounds contained in the activation treatment agent is preferably an alkali metal compound that exhibits alkalinity when dissolved in water. When the activation treatment agent containing such an alkali metal compound is dissolved in pure water, the pH of the solution becomes greater than 7. Hereinafter, such an activation treatment agent may be referred to as an "alkaline activation treatment agent".

[0078] By using the alkaline activation treatment agent, the generation of corrosive gases in the heating step can be further suppressed, so that the discharge capacity of the battery manufactured using the recovered positive electrode active material can be further increased. In addition, by using the alkaline activation treatment agent, the treatment rate of the carbon-based conductive material and the binder can also be increased.

[0079] Examples of the alkali metal compound that exhibits alkalinity when dissolved in water and is contained in the alkaline activation treatment agent include hydroxides, carbonates, bicarbonates, oxides, peroxides, and superoxides of alkali metals. Specifically, hydroxides such as LiOH, NaOH, KOH, RbOH, CsOH; Li 2 CO 3 、Na 2 CO 3 、K 2 CO 3 、RbCO 3 、CsCO 3 and other carbonates; LiHCO 3 、NaHCO 3 、KHCO 3 、RbHCO 3 、CsHCO 3 and other bicarbonates; Li 2 O、Na 2 O、K 2 O、Rb 2 O、Cs 2 O and other oxides; Li 2 O 2 、Na 2 O 2 、K 2 O 2 、Rb 2 O 2 、Cs 2 O 2 and other peroxides; LiO2 , NaO 2 , KO 2 , RbO 2 , CsO 2 Examples of such superoxides include. These may include one or more of them in the activating agent.

[0080] Further, when the conductive material contained in the positive electrode composite material is a carbon-based conductive material, at least one of the alkali metal compounds contained in the activating agent may be an alkali metal compound having an oxidizing power to oxidize and decompose the carbon-based conductive material at the temperature of the heating step. Hereinafter, an activating agent containing such an alkali metal compound may be referred to as an "activating agent having oxidizing power".

[0081] When using such an activating agent having oxidizing power, it is particularly effective in promoting the oxidation of the carbon-based 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, and can increase the discharge capacity of the battery manufactured using the obtained positive electrode active material, and may further improve the effect of preventing the generation of corrosive gases in the heating step.

[0082] Examples of the alkali metal compound having an oxidizing power necessary for oxidizing the carbon-based conductive material and hydrocarbon to carbon dioxide and water vapor include alkali metal peroxides, superoxides, nitrates, sulfates, vanadates, and molybdates. These may be used alone or in combination of two or more.

[0083] Specifically, superoxides such as Li 2 O 2 , Na 2 O 2 , K 2 O 2 , Rb 2 O 2 , Cs 2 O 2 ; LiO 2 , NaO 2 , KO 2 , RbO 2 , CsO 2 ; LiNO3 , NaNO 3 , KNO 3 , RbNO 3 , CsNO 3 and other nitrates; Li 2 SO 4 , Na 2 SO 4 , K 2 SO 4 , Rb 2 SO 4 , Cs 2 SO 4 and other sulfates; LiVO 3 , NaVO 3 , KVO 3 , RbVO 3 , CsVO 3 and other vanadates; Li 2 MoO 4 , Na 2 MoO 4 , K 2 MoO 4 , Rb 2 MoO 4 , CsMoO 4 and other molybdates; may be mentioned.

[0084] Details of the oxidizing power of these alkali metal compounds are described in Japanese Patent Application Laid-Open No. 2012-186150.

[0085] From the viewpoint that the rate characteristics of a battery manufactured using a recycled positive electrode active material are more likely to be made comparable to those of a battery manufactured using an unused positive electrode active material, the alkali metal compound may be a carbonate or a sulfate, and may be at least one selected from the group consisting of Li 2 CO 3 , Na 2 SO 4 , Na 2 CO 3 , and K 2 CO 3 selected from the group consisting of.

[0086] Step (2): Heating step The heating step is a step of heating the mixture obtained in step (1) (hereinafter sometimes referred to as the "mixture before heating") at a temperature of T °C. The mixture obtained in this heating step may be referred to as the "mixture after heating".

[0087] The temperature T may be less than the melting start temperature (Tmp) of the activating agent, or may be equal to or greater than the melting start temperature (Tmp) of the activating agent. In this specification, the fact that the temperature T is less than the melting start temperature (Tmp) of the activating agent, that is, heating the mixture before heating to a temperature lower than the melting start temperature of the activating agent means heating while maintaining the temperature below the melting start temperature of the activating agent (heating at a holding temperature lower than the melting start temperature of the activating agent). When heating to a temperature lower than the melting start temperature of the activating agent, it means not heating the mixture before heating to a temperature equal to or higher than the melting start temperature of the activating agent. Further, heating the mixture before heating to a temperature equal to or higher than the melting start temperature of the activating agent means heating while maintaining the temperature equal to or higher than the melting start temperature of the activating agent (heating at a holding temperature equal to or higher than the melting start temperature of the activating agent).

[0088] Note that the "melting start temperature (Tmp) of the activating agent" means the lowest temperature at which a part of the activating agent exhibits a liquid phase.

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

[0090] In step (2), by heating the mixture before heating to a temperature lower than the melting start temperature (Tmp) of the activating agent, the following effects occur. Therefore, from the viewpoint that the temperature T makes it easier to achieve rate characteristics comparable to those of a battery manufactured using an unused positive electrode active material by suppressing the elution of metal in the positive electrode active material into the molten salt reaction field of the activating agent, it is preferably less than the melting start temperature (Tmp) of the activating agent.

[0091] 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 generated by the decomposition of the binder, conductive material, etc. contained in the positive electrode composite material are rapidly generated, and when these come into contact with the positive electrode active material, the crystal structure of the positive electrode active material is suppressed from deteriorating, and it becomes easier to achieve charge-discharge characteristics comparable to those of a battery manufactured using an unused positive electrode active material. Further, by heating the mixture before heating together with the activation treatment agent, a crystal structure repair effect can also be obtained.

[0092] By heating the mixture before heating to a temperature equal to or higher than the melting start temperature (Tmp) of the activation treatment agent, at least a part of the activation treatment agent melts. When the melted activation treatment agent comes into contact with the positive electrode active material, a crystal structure repair effect of the positive electrode active material can also be obtained.

[0093] When the melted activation treatment agent comes into contact with the carbon-based conductive material and the binder, the rate of oxidative decomposition of the conductive material and the binder is improved. Further, when the melted activation treatment agent comes into contact with a fluorine compound derived from the binder, electrolyte, etc., the fluorine component is stabilized as an alkali metal fluoride, the generation of hydrogen fluoride, which is a corrosive gas, is prevented, and the deterioration of the crystal structure of the positive electrode active material is further suppressed.

[0094] Furthermore, when the activation treatment agent contains the same alkali metal as the positive electrode active material, it becomes possible to supply the alkali metal lacking in the positive electrode active material.

[0095] From the viewpoint of suppressing the rapid generation of hydrogen fluoride and carbon dioxide generated by the decomposition of the binder, conductive material, etc. contained in the positive electrode composite material, and suppressing the deterioration of the crystal structure of the positive electrode active material when these come into contact with the positive electrode active material, and making it easier to achieve rate characteristics comparable to those of a battery manufactured using an unused positive electrode active material, the temperature T may be 700 °C or lower, 650 °C or lower, 600 °C or lower, or 550 °C or lower.

[0096] From the perspective of promoting the decomposition of binders, conductive materials, etc., and making it easier to achieve rate characteristics comparable to those of batteries manufactured using unused positive electrode active materials, the temperature T 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.

[0097] The melting start temperature (Tmp) of the activation treatment agent is preferably 900 °C or lower, more preferably 800 °C or lower, still more preferably 700 °C or lower, and particularly preferably 600 °C or lower. There is no lower limit for the melting start temperature (Tmp) of the activation treatment agent, but for example, it may be 150 °C.

[0098] The melting point of the activation treatment agent means the lowest temperature at which a part of the activation treatment agent exhibits a liquid phase when only the activation treatment agent is heated. By mixing the positive electrode composite material and the activation treatment agent, the melting start temperature (Tmp) of the activation treatment agent becomes lower than the melting point of the activation treatment agent.

[0099] The melting point of the activation treatment agent is a value determined by differential thermal measurement (DTA). Specifically, for 5 mg of the activation treatment agent, the temperature at which the DTA signal shows an endothermic peak in differential thermal measurement (DTA, measurement conditions: heating rate: 10 °C / min) is defined as the melting point of the activation treatment agent.

[0100] There is no particular limitation on the atmosphere during heating, and it may be an oxygen-containing gas such as air, nitrogen, argon, or carbon dioxide. There is no particular limitation on the pressure of the atmosphere, but it can be atmospheric pressure, or it may be a reduced-pressure atmosphere or a pressurized atmosphere.

[0101] The temperature T and the holding time at the temperature T can be appropriately adjusted according to the respective types and combinations of the positive electrode active material, binder, conductive material, and alkali metal compounds and other compounds contained in the activation treatment agent that make up the positive electrode composite material. Usually, the temperature T is in the range of 100 to 1000 °C, and the holding time is about 10 minutes to 24 hours.

[0102] The temperature T is preferably lower than the melting point of the alkali metal compound contained in the activating agent. Note that the melting point of the alkali metal compound may be lower than the melting point of each single compound by mixing a plurality of compounds. When the activating agent contains two or more kinds of alkali metal compounds, the eutectic point is taken as the melting point of the alkali metal compound.

[0103] After the heating step, the mixture can be cooled to an arbitrary temperature (for example, about room temperature) as necessary. In this way, a heated mixture containing the heated positive electrode active material is obtained.

[0104] Step (3): Positive electrode active material recovery step The positive electrode active material recovery step is a step of heating the heated mixture (or the solid component obtained in step (3a), the solid component obtained in step (3b)) at a temperature higher than that in step (2) after the heating step in step (2) to recover the heated positive electrode active material.

[0105] In the heated mixture, in addition to the heated positive electrode active material, components derived from the activating agent (such as alkali metal compounds), unreacted activating agent, undecomposed conductive material and binder, and undecomposed products of other positive electrode composite materials are included. Further, when the positive electrode composite contains an electrolytic solution containing a fluorine component, it may contain a fluorine component derived from the electrolyte. In step (3), from the viewpoint of making it easier to achieve rate characteristics comparable to those of a battery manufactured using the unused positive electrode active material by increasing the purity of the positive electrode active material, it is preferable to remove components derived from the activating agent (such as alkali metal compounds), unreacted activating agent, undecomposed conductive material and binder, and undecomposed products of other positive electrode composite materials.

[0106] As a method for separating and recovering the heated positive electrode active material from the heated mixture, there are a solid-liquid separation method in which a solvent such as water is added to the mixture to form a slurry and then solid-liquid separation is performed, and a vaporization separation method in which components other than the heated positive electrode active material are vaporized and separated by heating the mixture. Hereinafter, the solid-liquid separation method will be described.

[0107] Step (3a): Solid-liquid separation step In step (3a), the mixture after heating is brought into contact with a liquid containing water to obtain a slurry containing a solid component and a liquid component, and then the slurry is separated into the solid component and the liquid component.

[0108] In the mixture after heating, in addition to the positive electrode active material after heating, components derived from the activation treatment agent (such as alkali metal compounds), and undecomposed substances of the positive electrode composite material such as undecomposed conductive materials and binders are included. Further, when the positive electrode composite material contains an electrolyte containing a fluorine component, it may also contain a fluorine component derived from the electrolyte.

[0109] In order to separate and recover the positive electrode active material after heating from the mixture after heating, a liquid containing water (liquid) is added to the mixture to form a slurry, and then solid-liquid separation is performed to separate it into a solid component and a liquid component.

[0110] The liquid used in the slurrying step is not particularly limited as long as it contains water. The amount of water in the liquid may be 50% by mass or more. Components other than water may be added to the liquid to adjust the pH in order to increase the solubility of the water-soluble components or increase the treatment rate.

[0111] Preferable examples of the liquid containing water include pure water and alkaline cleaning liquids. Examples of the alkaline cleaning liquid include aqueous solutions of one or more anhydrides and hydrates selected from the group consisting of lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and ammonium carbonate. Further, ammonia can also be used as the alkali.

[0112] 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. Note that the liquid component contains an alkali metal component derived from the activation treatment agent and / or a fluorine component derived from the binder and the electrolyte.

[0113] The amount of the liquid added to the mixture is appropriately determined in consideration of the amount of the positive electrode active material after heating contained in the mixture and the amount of each water-soluble component other than the positive electrode active material.

[0114] In step (3a), it is preferable to stir the mixture after heating and the liquid containing water to obtain a slurry. Thereby, the dissolution of the water-soluble component is promoted. The peripheral speed of the tip of the stirring blade is preferably 0.1 to 0.9 m / s.

[0115] The slurry formed in the slurrying step is then subjected to solid-liquid separation. Solid-liquid separation is a step of separating the slurry into a liquid component and a solid component. As the method of solid-liquid separation, a conventionally known method may be used, and examples thereof include filtration and centrifugation.

[0116] In step (3a), after solid-liquid separation, rinsing of the obtained solid component may be performed. Rinsing is an operation of bringing the obtained solid component into contact with a liquid containing water again to obtain a slurry, and then separating the slurry into a solid component and a liquid component again. In step (3a), rinsing may be performed a plurality of times. The slurry concentration in rinsing can also be the same as described above.

[0117] Step (3b): Drying step Step (3b) is, for example, a step of removing water from the solid component by exposing the solid component obtained in step (3a) to a heating and / or reduced-pressure environment.

[0118] As the heating temperature, 100°C or higher is preferable for removing water. In order to more sufficiently remove water, it is preferable to set the temperature to 150°C or higher. Particularly, at a temperature of 250°C or higher, it is preferable because the discharge capacity of the battery manufactured using the obtained positive electrode active material is further increased. 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 less than 900°C.

[0119] The range of the reduced pressure reached is, for example, 1.0×10 -10 ~1.0×10 3It can be Pa.

[0120] Step (3c): Annealing step Step (3c) is a step of heating the mixture after heating (or the solid component obtained in step (3a), the solid component obtained in step (3b)) at a temperature higher than that in step (2).

[0121] In one embodiment, when the temperature in step (2) is T °C, the temperature for heating the mixture after heating is (1.6 × T) °C or higher. By the temperature for heating the mixture after heating being (1.6 × T) °C or higher, the rate characteristics of the battery manufactured using the recycled positive electrode active material can be made more comparable to the rate characteristics of the battery manufactured using the unused positive electrode active material.

[0122] In another embodiment, when the temperature in step (2) is T °C, the temperature for heating the mixture after heating is (T + 300) °C or higher. Also by the temperature for heating the mixture after heating being (T + 300) °C or higher, the rate characteristics of the battery manufactured using the recycled positive electrode active material can be made more comparable to the rate characteristics of the battery manufactured using the unused positive electrode active material. That is, the method for manufacturing a recycled positive electrode active material according to another embodiment of the present invention includes the following steps. Step (1): A step of mixing a positive electrode composite material containing a positive electrode active material and a binder with an activation treatment agent containing one or more alkali metal compounds to obtain a mixture Step (2): A step of heating the mixture at a temperature of T °C to obtain a mixture after heating Step (3): A step of heating the mixture after heating at a temperature of (T + 300) °C or higher and recovering the positive electrode active material after heating

[0123] The temperature for heating the mixture after heating (e.g., (1.6×T) or (T + 300)) may be above 700 °C, above 750 °C, above 800 °C, above 850 °C, or above 900 °C from the viewpoints of vaporizing components other than the positive electrode active material to remove impurities and making it easier to achieve rate 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.

[0124] The temperature for heating the mixture after heating may be at or above the melting start 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 mixture after heating may be heated at a temperature 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 start temperature of the activation treatment agent.

[0125] The temperature for heating the mixture after heating (e.g., (1.6×T) or (T + 300)) 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 viewpoints of suppressing deterioration of the positive electrode active material due to heat and making it easier to achieve rate characteristics comparable to those of a battery manufactured using an unused positive electrode active material.

[0126] Let the heating temperature in step (2) be T 1 and the heating temperature in step (3) be T 2 When this is the case, T 2 / T 1From the perspective of making it easier to achieve rate characteristics comparable to those of a battery manufactured using unused positive electrode active material, it may be 1.7 or more, 1.8 or more, 1.9 or more, or 2 or more. From the same perspective, it may be 2.5 or less, 2.4 or less, 2.3 or less, or 2.2 or less. That is, when the heating temperature in step (2) is T °C, the heating temperature in step (3) may be (1.7×T) °C or more, (1.8×T) °C or more, (1.9×T) °C or more, or (2×T) °C or more, and may be (2.5×T) °C or less, (2.4×T) °C or less, (2.3×T) °C or less, or (2.2×T) °C or less.

[0127] Let the heating temperature in step (2) be T 1 and the heating temperature in step (3) be T 2 When doing so, T 2 -T 1 From the perspective of making it easier to achieve charge-discharge characteristics comparable to those of a battery manufactured using unused positive electrode active material, it may be 350 °C or more, 400 °C or more, 450 °C or more, or 500 °C or more. From the same perspective, it may be 1000 °C or less, 800 °C or less, 700 °C or less, 600 °C or less, or 500 °C or less. That is, when the heating temperature in step (2) is T °C, the heating temperature in step (3) may be (T + 350) °C or more, (T + 400) °C or more, (T + 450) °C or more, or (T + 500) °C or more, and may be (T + 1000) °C or less, (T + 800) °C or less, (T + 700) °C or less, (T + 600) °C or less, or (T + 500) °C or less.

[0128] The atmosphere of the heat treatment is not limited, but it is preferably an oxygen-containing atmosphere such as air. The holding time of the heat treatment can be 1 minute to 24 hours. In particular, it is preferably heated at a temperature higher than that in step (2) for 0.1 hour or more and 5 hours or less.

[0129] By using the method for manufacturing a recycled positive electrode active material of the present invention, the recycled positive electrode active material obtained from a battery composite material can be used in the same manner as an unused positive electrode active material. The method for manufacturing a positive electrode and a battery using the recycled positive electrode active material is the same as the method for manufacturing a positive electrode and a battery using an unused positive electrode active material, and is well-known.

[0130] The rate characteristics of a battery manufactured using the positive electrode active material obtained by the method for manufacturing a recycled positive electrode active material according to an embodiment of the present invention are comparable to those of a battery manufactured using an unused positive electrode active material. Specifically, for example, after performing constant current charging up to a maximum charging voltage of 4.3V at a current value of 0.2C in an environment of 25°C for a battery manufactured using the positive electrode active material obtained by the method for manufacturing a recycled positive electrode active material according to an embodiment, when performing constant current discharging up to a minimum discharging voltage of 2.5V at a current value of 0.5C, 1C, 2C, 3C, or 5C, the recyclability of the discharging capacity (discharging capacity of the battery manufactured using the recycled positive electrode active material / discharging capacity of the battery manufactured using the unused positive electrode active material) is 0.9 to 1.1, which is equivalent to the charging capacity of a battery manufactured using an unused positive electrode active material.

[0131] In this specification, the 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 for manufacturing a positive electrode or the like. The method for manufacturing a recycled positive electrode active material can include additional steps before and after steps (1) to (3). In this specification, the 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 the additional steps other than steps (1) to (3) are pre-step (A) and pre-step (B) performed before step (1).

Examples

[0132] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples unless the gist thereof is changed.

[0133] <Manufacture of Positive Electrode> The cathode described below was fabricated through the following procedure. A mixture was obtained by mixing 90 parts by mass of a cathode active material (unused cathode active material or recycled cathode 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 PVdF serving as the binder, a binder solution prepared by dissolving PVdF in NMP in advance was used. The cathode composite paste was prepared by kneading the mixture in an agate mortar. NMP was added and adjusted so that the total mass of the cathode active material, binder, and conductive material in the cathode composite paste was 52% by mass.

[0134] On one surface of an aluminum foil 1085 (manufactured by Nippon Foil Mfg. Co., Ltd.) for a lithium-ion secondary battery cathode current collector with a thickness of 20 μm, the cathode composite paste was applied so that the amount of the cathode active material was 10.0 ± 0.2 mg / cm 2 After that, the cathode was obtained by vacuum drying at 150 °C for 8 hours. The electrode area of this cathode was 1.65 cm 2 was.

[0135] <Manufacture of Battery> The coin-type battery described below was fabricated through the following procedure. The above-mentioned cathode, electrolyte, separator, and anode were combined to manufacture a coin-type battery (non-aqueous electrolyte secondary battery). The battery assembly was performed inside a glove box under an argon atmosphere. As the electrolyte, a solution prepared by dissolving LiPF 6 at a ratio of 1.0 mol / L in a 30:35:35 (volume ratio) mixture of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate was used. As the separator, a laminated film separator in which a heat-resistant porous layer was laminated on a porous film (made of polyethylene) was used. As the anode, metallic lithium was used.

[0136] <Manufacture of Cathode before Recycling> As the cathode active material, the composition was Li 1.05 Ni 0.34 Co 0.33 Mn 0.33 O 2A positive electrode active material NCM111 with 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. Using this positive electrode active material (unused positive electrode active material), the above-mentioned coin-type battery was fabricated. After performing constant current charging up to a maximum charging voltage of 4.3 V at a current value of 0.2C while maintaining at 25°C, constant current discharging was performed at current values of 0.5C, 1C, 2C, 3C, and 5C until a minimum discharging voltage of 2.5 V, and the discharging capacity when performing a rate test was measured. The measurement results are shown in Table 1.

[0137] (Example 1) From the positive electrode of the process end material generated when fabricating the above positive electrode, the electrode composite material was mechanically shaved off to peel the electrode composite material from the current collector. To 30 g of the electrode composite material taken out from the positive electrode, 10 mol of Li 2 CO 3 with respect to 100 mol of the positive electrode active material, and 10 mol of Na 2 SO 4 with respect to 100 mol of the positive electrode active material were mixed to obtain a mixture (mixture before heating). The melting start temperature of the activation treatment agent was 510°C.

[0138] 30 g of the mixture before heating was placed in an electric furnace, and the mixture was heated under an air atmosphere under the conditions of a heating rate of 300°C / h, a heating temperature of 450°C (below the melting start temperature of the activation treatment agent), and a heating time of 360 minutes.

[0139] The mixture after heating was pulverized, distilled water was added and stirred to obtain a slurry. The obtained slurry was filtered to separate it into a solid component and a liquid component. Next, the solid component was recovered and dried under reduced pressure at 100°C for 1 hour.

[0140] The dried solid component was placed in an electric furnace and heated under an air atmosphere at a heating temperature of 900 °C for a heating time of 60 minutes to obtain a recycled cathode active material after heating. Subsequently, the recycled cathode active material after heating was naturally cooled to room temperature, and it was confirmed that the composition, crystal structure, average particle size, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. A coin-type battery as described above was fabricated using the recycled cathode active material, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining a temperature of 25 °C. The measurement results are shown in Table 1.

[0141] (Example 2) A recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature for heating the dried solid component 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 the unused cathode active material. A coin-type battery as described above was fabricated using the recycled cathode active material, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining a temperature of 25 °C. The measurement results are shown in Table 1.

[0142] (Example 3) As an activation treatment agent, 10 mol of Na 2 CO 3 (melting start temperature: 851 °C) was used. A recycled cathode active material was obtained in the same manner as in Example 1, except that 5 g of the electrode mixture taken out from the cathode was mixed with the activation treatment agent to obtain a mixture before heating. The composition, crystal structure, average particle size, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. A coin-type battery as described above was fabricated using the recycled cathode active material, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining a temperature of 25 °C. The measurement results are shown in Table 1.

[0143] (Example 4) A recycled cathode active material was obtained in the same manner as in Example 3, except that the temperature for heating the solid component after drying was changed to 950°C. The composition, crystal structure, average particle diameter, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. Using the recycled cathode active material, the above coin-type battery was fabricated, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining at 25°C. The measurement results are shown in Table 1.

[0144] (Comparative Example 1) A recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature for heating the mixture before heating was changed to 700°C (equal to or higher than the melting start temperature), and the temperature for heating the solid component after drying was changed to 700°C. The composition, crystal structure, average particle diameter, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. Using the recycled cathode active material, the above coin-type battery was fabricated, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining at 25°C. The measurement results are shown in Table 1.

[0145] (Comparative Example 2) A recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature for heating the mixture before heating was changed to 700°C (equal to or higher than the melting start temperature). The composition, crystal structure, average particle diameter, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. Using the recycled cathode active material, the above coin-type battery was fabricated, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining at 25°C. The measurement results are shown in Table 1.

[0146] (Comparative Example 3) The recycled cathode active material was obtained in the same manner as in Example 1, except that the temperature for heating the mixture before heating was changed to 450 °C (below the melting start temperature), and the temperature for heating the solid component after drying was changed to 700 °C. The composition, crystal structure, average particle size, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. Using the recycled cathode active material, the above coin-type battery was fabricated, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining at 25 °C. The measurement results are shown in Table 1.

[0147] <Manufacture of the cathode before recycling> As the cathode active material, a cathode active material NCM111 with a composition of Li 1.18 Ni 0.34 Co 0.33 Mn 0.33 O 2 and a crystal structure of R-3m was prepared. The rated capacity of this cathode active material was 160 mAh / g, and the 1C current was 160 mA / g. Using this cathode active material (unused cathode active material), the above coin-type battery was fabricated. After performing constant current charging up to a maximum charging voltage of 4.3V at a current value of 0.2C while maintaining at 25 °C, the discharge capacity was measured when a rate test was conducted by performing constant current discharge up to a minimum discharge voltage of 2.5V at current values of 0.5C, 1C, 2C, 3C, and 5C. The measurement results are shown in Table 2.

[0148] (Example 5) From the cathode of the process end material generated when fabricating the above cathode, the electrode mixture was mechanically shaved off, and the electrode mixture was peeled off from the current collector. To 5 g of the electrode mixture taken out from the cathode, 10 mol of Li 2 CO 3 per 100 mol of the cathode active material and 10 mol of Na 2 SO 4 per 100 mol of the cathode active material were mixed to obtain a mixture (mixture before heating). The melting start temperature of the activation treatment agent was 510 °C.

[0149] A 40 g mixture before heating was placed in an electric furnace and heated under an air atmosphere at a heating rate of 300 °C / h, a heating temperature of 500 °C (below the melting start temperature of the activating 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.

[0150] The heated mixture was pulverized, distilled water was added and stirred to obtain a slurry. The obtained slurry was filtered and separated into a solid component and a liquid component. Subsequently, the solid component was recovered and dried under reduced pressure at 100 °C for 1 hour.

[0151] The dried solid component was placed in an electric furnace and heated under an air atmosphere at a heating temperature of 900 °C and a heating time of 360 minutes to obtain a recycled positive electrode active material after heating. Subsequently, the recycled positive electrode active material after heating was naturally cooled to room temperature, and it was confirmed that the composition, crystal structure, average particle diameter, 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 as described above was fabricated using the recycled positive electrode active material, and a rate test was conducted at current values of 0.5 C, 1 C, 2 C, 3 C, and 5 C while maintaining at 25 °C. The measurement results are shown in Table 2.

[0152] (Example 6) A recycled positive electrode active material was obtained in the same manner as in Example 5, except that the air flow rate during heating of the mixture before heating was changed to 1 L / min and the gas-powder ratio was changed to 11.5 m 3 / kg. The composition, crystal structure, average particle diameter, 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 as described above was fabricated using the recycled positive electrode active material, and a rate test was conducted at current values of 0.5 C, 1 C, 2 C, 3 C, and 5 C while maintaining at 25 °C. The measurement results are shown in Table 2.

[0153] (Example 7) A recycled cathode active material was obtained in the same manner as in Example 6, except that the temperature at which the mixture before heating was heated was changed to 525°C. The composition, crystal structure, average particle size, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining the temperature at 25°C. The measurement results are shown in Table 2.

[0154] (Example 8) A recycled cathode active material was obtained in the same manner as in Example 5, except that the temperature at which the mixture before heating was heated was changed to 550°C, the flow rate of air was changed to 0.2 L / min, and the gas-powder ratio was changed to 2.4 m 3 / kg. The composition, crystal structure, average particle size, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining the temperature at 25°C. The measurement results are shown in Table 2.

[0155] (Comparative Example 4) A recycled cathode active material was obtained in the same manner as in Example 5, except that the amount of the mixture before heating was changed to 20 g, the temperature at which the mixture before heating was heated was changed to 700°C, the heating time was changed to 360 minutes, the flow rate of air was changed to 0.85 L / min, and the gas-powder ratio was changed to 28.7 m 3 / kg. The composition, crystal structure, average particle size, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. A coin-type battery was fabricated using the recycled cathode active material, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining the temperature at 25°C. The measurement results are shown in Table 2.

[0156] (Comparative Example 5) A recycled cathode active material was obtained in the same manner as in Comparative Example 4, except that the temperature for heating the solid component after drying was changed to 950°C. The composition, crystal structure, average particle diameter, and specific surface area of the obtained recycled cathode active material were comparable to those of the unused cathode active material. Using the recycled cathode active material, the above coin-type battery was fabricated, and a rate test was conducted at current values of 0.5C, 1C, 2C, 3C, and 5C while maintaining the temperature at 25°C. The measurement results are shown in Table 2.

[0157] The heating temperature (T 1 ) of the mixture before heating, the heating temperature (T 2 ) of the solid component after drying, the ratio (T 2 / T 1 ) of the heating temperature of the solid component after drying to the heating temperature of the mixture before heating, the difference (T 2 -T 1 ) between the heating temperature of the mixture before heating and the heating temperature of the solid component after drying, and the measurement results (measured values and recycling degree) of the rate test are shown in Table 1 and Table 2, respectively.

[0158]

Table 1

[0159]

Table 2

Claims

1. A method for producing a recycled positive electrode active material, comprising the steps of: (1) A step of mixing a positive electrode mixture containing a positive electrode 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 at a temperature T° C. to obtain a heated mixture. (3) A step of heating the mixture after heating at a temperature of (1.6×T)° C. or higher and recovering the heated positive electrode active material.

2. A method for producing a recycled positive electrode active material, comprising the steps of: (1) A step of mixing a positive electrode mixture containing a positive electrode 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 at a temperature T° C. to obtain a heated mixture. (3) A step of heating the mixture after heating at a temperature of (T+300)° C. or higher and recovering the heated positive electrode active material.

3. The process (3) (3a) contacting the heated mixture with a liquid containing water to obtain a slurry containing a solid component and a liquid component containing the heated mixture, and then separating the slurry into the solid component and the liquid component; and (3c) A step of recovering the heated positive electrode active material by heating the solid component at a temperature of (1.6×T)° C. or higher. The method of claim 1 , comprising:

4. The process (3) (3a) contacting the heated mixture with a liquid containing water to obtain a slurry containing a solid component and a liquid component containing the heated mixture, and then separating the slurry into the solid component and the liquid component; and (3c) A step of recovering the heated positive electrode active material by heating the solid component at a temperature of (T+300)° C. or higher. The method of claim 2, comprising:

5. The method according to any one of claims 1 to 4, wherein in the step (2), the temperature T is lower than a melting start temperature of the activation treatment agent.

6. The method according to any one of claims 1 to 4, wherein the positive electrode active material comprises a lithium compound.

7. 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. The manufacturing method according to any one of claims 1 to 4. Element group 1: Ni, Co, Mn, Fe, Al, and P Element group 2: Li, Na, K, Ca, Sr, Ba, and Mg

8. The method according to any one of claims 1 to 4, 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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