Method for producing active substance

Abstract

The present invention provides a method for producing an active material comprising the following steps: (1) mixing an activation agent containing one or more alkali metal compounds with an electrode composite material comprising an active material and a binder; (2) heating the resulting mixture to a temperature above the melting point of the activation agent in an atmosphere having an oxygen partial pressure of 0.3 atm or greater; and (3) recovering the active material from the heated mixture.

Description

Technical Field

[0001] The present invention relates to a method for producing an active substance. Background Art

[0002] Battery active materials contain rare metal components such as cobalt, nickel, manganese, and lithium. Compounds containing these rare metal components as primary components are particularly used as positive electrode active materials in non-aqueous electrolyte secondary batteries. To conserve rare metal resources, methods are being sought to regenerate these rare metal components from secondary battery waste.

[0003] For example, Patent Document 1 discloses a method in which an electrode composite is mixed with an activation agent containing an alkali metal compound, the mixture is heated to decompose the binder, and the decomposition products or the activation agent are removed using water or the like to recover the active material. This method is cost-effective because it directly recovers the active material from battery waste without using an organic solvent.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2012-186150 Summary of the Invention

[0007] Problems to be solved by the invention

[0008] However, in order to appropriately reuse the regenerated active material, it is necessary to suppress the degradation of the crystal structure of the active material before and after the regeneration process. If the crystal structure of the active material deteriorates, it will lead to a decrease in charge and discharge capacity, which is not preferable.

[0009] The present invention has been made in view of the above-mentioned problems, and provides a method for producing an active material capable of suppressing degradation of the crystal structure.

[0010] Means for solving problems

[0011] The method for producing the active material of the present invention includes the following steps.

[0012] (1) A step of mixing an activation agent containing one or more alkali metal compounds into an electrode composite material containing an active material and a binder;

[0013] (2) heating the obtained mixture to a temperature not lower than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.3 atm or higher;

[0014] (3) A step of recovering the active substance from the heated mixture.

[0015] Here, the active material may be a positive electrode active material or a positive electrode active material of a non-aqueous secondary battery.

[0016] The active material may be a composite oxide containing one or more elements selected from the following element group 1 and one or more elements selected from the following element group 2.

[0017] Element group 1: Ni, Co, Mn, Fe, Al and P

[0018] Element group 2: Li, Na, K, Ca, Sr, Ba and Mg

[0019] The active material can be Li 1+a M 2 b M 1 M T c O 2+d X e The composite oxide represented.

[0020] Among them, M 2 represents at least one element selected from the group consisting of Na, K, Ca, Sr, Ba, and Mg,

[0021] M 1 represents at least one element selected from the group consisting of Ni, Co, Mn, Fe, Al and P,

[0022] M T represents at least one element selected from the group consisting of transition metal elements other than Ni, Co, Mn and Fe,

[0023] X represents at least one element selected from the group consisting of non-metallic elements excluding oxygen O and P,

[0024] It satisfies -0.4<a<1.5, 0≤b<0.5, 0≤c<0.5, -0.5<d<1.5, and 0≤e<0.5.

[0025] In addition, M in the above composite oxide 1 The molar fraction of Ni contained in the MgO may be 0.5 or more.

[0026] Furthermore, the composite oxide may have a hexagonal crystal structure.

[0027] Furthermore, the discharge capacity of the recovered active material can be 150 mAh / g or more.

[0028] Furthermore, at least one alkali metal compound contained in the activation agent may contain the same alkali metal element as the alkali metal element contained in the active material.

[0029] Furthermore, at least one of the alkali metal compounds contained in the activation agent may be an alkali metal compound that exhibits basicity when dissolved in water.

[0030] Furthermore, the alkali metal compound that exhibits basicity when dissolved in water may be one or more selected from the group consisting of hydroxides, carbonates, hydrogen carbonates, oxides, peroxides, and superoxides of alkali metals.

[0031] Furthermore, the activation agent may have a melting start temperature of 700° C. or lower.

[0032] Effects of the Invention

[0033] According to the present invention, it is possible to produce an active material from an electrode composite material while suppressing degradation of the crystal structure. DETAILED DESCRIPTION

[0034] Hereinafter, embodiments of the present invention will be described.

[0035] The method for producing an active material according to an embodiment of the present invention includes the following steps.

[0036] (1) A step of mixing an activation agent containing one or more alkali metal compounds into an electrode composite material containing an active material and a binder;

[0037] (2) heating the obtained mixture to a temperature higher than the melting start temperature of the activation agent in an atmosphere with an oxygen partial pressure of 0.3 atm or higher;

[0038] (3) A step of recovering the active substance from the heated mixture.

[0039] Hereinafter, each step in the method for recovering active material from battery waste of the present invention will be described in detail.

[0040] Step (1): Mixing the activation agent into the electrode composite

[0041] First, prepare the electrode composite material.

[0042] <Electrode composite materials>

[0043] The electrode mixture is a material containing an active material and a binder, wherein the active materials are bound together by the binder. The electrode mixture may further contain a conductive material, in which case the active material and the conductive material are bound together by the binder.

[0044] Active substances

[0045] The active material may be a positive electrode active material or a negative electrode active material.

[0046] Examples of positive electrode active materials include composite compounds containing 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, and the like as constituent elements.

[0047] Examples of negative electrode active materials include composite compounds containing 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, and tungsten as constituent elements.

[0048] It should be noted that the active substance may contain only a single compound or may be composed of a plurality of compounds.

[0049] Preferred examples of the positive electrode active material include complex compounds containing lithium, oxygen, sodium, potassium, calcium, magnesium, aluminum, phosphorus, sulfur, vanadium, manganese, iron, nickel, copper, cobalt, gallium, molybdenum, indium, tungsten, and the like as constituent elements.

[0050] Furthermore, the active material of the present invention is preferably a positive electrode active material for a non-aqueous secondary battery. Examples of positive electrode active materials for non-aqueous secondary batteries include composite oxides containing one or more elements selected from the following element group 1 and one or more metals selected from the following element group 2.

[0051] Element group 1: Ni, Co, Mn, Fe, Al and P

[0052] Element group 2: Li, Na, K, Ca, Sr, Ba and Mg

[0053] Among them, preferred are lithium transition metal composite oxides in which element group 1 is one or more selected from Ni, Co, Mn, Fe and P and element group 2 is Li, or sodium transition metal composite oxides in which element group 2 is Na. Lithium transition metal composite oxides are particularly preferred.

[0054] Specifically, as lithium transition metal composite oxides, there can be listed LiCoO2, LiNiO2, Li(Ni, Co)O2, Li(Ni, Co, Al)O2, Li(Ni, Mn)O2, Li(Ni, Mn, Co)O2, LiMn2O4, Li(Mn, Fe)2O4, Li2MnO3, Li2NiO3, Li2(Ni, Mn)O3, LiFePO4, LiMnPO4, etc., and they can be used alone or in combination of two or more.

[0055] Specific examples of sodium transition metal composite oxides include NaCoO2, NaNiO2, Na(Ni, Co)O2, Na(Ni, Mn)O2, Na(Ni, Mn, Co)O2, Na(Fe, Ni, Mn)O2, NaMn2O4, Na(Mn, Fe)2O4, NaFePO4, and NaMnPO4. These can be used alone or in combination of two or more.

[0056] Especially preferred is the composite oxide with Li 1+a M 2 b M 1 M T c O 2+d X e (Formula A) represents.

[0057] Among them, M 2 represents at least one element selected from the group consisting of Na, Ca, Sr, Ba, and Mg, and M 1 represents at least one element selected from the group consisting of Ni, Co, Mn, Fe, Al, and P, and M T represents at least one element selected from the group consisting of transition metal elements other than Ni, Co, Mn and Fe, X represents at least one element selected from the group consisting of non-metallic elements other than oxygen O and P, and satisfies -0.4<a<1.5, 0≤b<0.5, 0≤c<0.5, -0.5<d<1.5, and 0≤e<0.5.

[0058] Examples of X include F, Cl, Br, I, S, Se, Te, and N.

[0059] M in composite oxides 1 The molar fraction of Ni contained in the quartz crystal may be 0.5 or more, or 0.6 or more, 0.7 or more, or 0.8 or more.

[0060] The crystal structure of the composite oxide as the active material is not particularly limited, but a layered structure is a preferred crystal structure, and a hexagonal or monoclinic crystal structure is more preferred.

[0061] The hexagonal crystal structure belongs to the group consisting of P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65 , any space group in the group consisting of P62, P64, P63, P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mm, P6 / mcc, P63 / mcm and P63 / mmc.

[0062] The above-mentioned monoclinic crystal structure belongs to any space group selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c and C2 / c.

[0063] Furthermore, it is preferable to belong to the space group of R-3m included in the hexagonal crystal structure or C2 / m included in the monoclinic crystal structure.

[0064] The crystal structure of the active material was identified from a powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement using CuKα rays as a radiation source.

[0065] There is no particular restriction on the particle size of the active material in the electrode composite. It is usually around 0.001 to 100 μm. It should be noted that the particle size distribution of the active material can be measured using a laser diffraction scattering particle size distribution measuring device (e.g., Mastersizer 2000 manufactured by Malvern). A volume-based cumulative particle size distribution curve is prepared from the obtained particle size distribution, and the value of the particle size (D50) at 50% accumulation from the microparticle side can be set as the average particle size of the powder. In addition, the particle size of the primary particles of the active material can be measured as the arithmetic mean of the equivalent circle diameter in an electron microscope photograph.

[0066] <Conductive materials>

[0067] Examples of the conductive material include metal-based conductive materials such as metal particles and carbon-based conductive materials formed of carbon materials.

[0068] Specific examples of carbon-based conductive materials include graphite powder, carbon black (eg, acetylene black), and fibrous carbon materials (eg, graphitized carbon fibers, carbon nanotubes).

[0069] The carbon-based conductive material may be a single carbon material or may be composed of a plurality of carbon materials.

[0070] In addition, the specific surface area of ​​the carbon material used as the carbon-based conductive material can generally be 0.1 to 500 m 2 / g.

[0071] In this case, the conductive material can be only 30m 2 / g or more carbon-based conductive material, can be 30m 2 / g or more carbon black, or 30m 2 / g or more acetylene black.

[0072] When an activation agent containing an alkali metal compound having oxidizing power, which will be described later, is used, the oxidation rate of the carbon-based conductive material can be increased, and even a carbon material having a small specific surface area may be oxidized.

[0073] <Binder>

[0074] Examples of the binder contained in the electrode composite (binder before activation treatment) are thermoplastic resins, specifically fluororesins such as polyvinylidene fluoride (hereinafter sometimes referred to as PVdF), polytetrafluoroethylene (hereinafter sometimes referred to as PTFE), tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride copolymers, hexafluoropropylene-vinylidene fluoride copolymers and tetrafluoroethylene-perfluorovinyl ether copolymers; polyolefin resins such as polyethylene and polypropylene; styrene-butadiene copolymers (hereinafter sometimes referred to as SBR), and mixtures of two or more of these are also possible.

[0075] There are no specific restrictions on the amounts of active material, conductive material, and binder in the electrode mix. The binder can be present in an amount of 0.5 to 30 parts by weight, or 1 to 5 parts by weight, relative to 100 parts by weight of the positive electrode active material. The conductive agent can be present in an amount of 0, but can also be present in an amount of 0 to 50 parts by weight, or 1 to 10 parts by weight, relative to 100 parts by weight of the positive electrode active material.

[0076] Such an electrode composite can be obtained by separating and recovering the electrode composite from a waste electrode having a current collector and an electrode composite layer.

[0077] The so-called "waste electrodes" can be electrodes recovered from discarded batteries and electrode waste generated during the manufacturing process of electrodes and batteries. Waste batteries can be used batteries or unused but non-standard batteries. In addition, electrode waste can include the ends of electrodes and non-standard electrodes generated during the battery manufacturing process. In addition, waste electrode composites generated during the electrode composite manufacturing process that are not attached to the current collector can also be used.

[0078] The electrode comprises a current collector made of a metal foil such as aluminum foil or copper foil and an electrode mixture layer provided on the current collector. The electrode mixture layer may be provided on one side or both sides of the current collector.

[0079] Methods for separating the electrode composite material from an electrode having an electrode composite material layer and a current collector include a method of mechanically peeling the electrode composite material layer from the current collector (e.g., a method of scraping the electrode composite material from the current collector), a method of peeling the electrode composite material layer from the current collector by allowing a solvent to penetrate the interface between the electrode composite material layer and the current collector, a method of separating the electrode composite material layer by dissolving the current collector using an alkaline or acidic aqueous solution, etc. A method of mechanically peeling the electrode composite material layer from the current collector is preferred.

[0080] The electrode can be either a positive electrode or a negative electrode. The positive electrode mixture can be recovered from the positive electrode, and the negative electrode mixture can be recovered from the negative electrode. If a positive electrode mixture is used, the positive electrode active material can be recovered, and if a negative electrode mixture is used, the negative electrode active material can be recovered. The method for producing the active material of the present invention is suitable for recovering the positive electrode active material from the positive electrode mixture, and is suitable for use as a positive electrode active material for a non-aqueous secondary battery.

[0081] Next, an activation agent containing one or two or more alkali metal compounds is mixed with the prepared electrode composite material.

[0082] The electrode material and the activation agent may be mixed by dry mixing or wet mixing, or by a combination of these mixing methods. The order of mixing is not particularly limited.

[0083] During mixing, it is preferred to perform a pulverization and mixing step using a mixing device equipped with a mixing medium such as balls, thereby improving mixing efficiency.

[0084] Dry mixing is preferred from the viewpoint of easier 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.

[0085] Specific examples of a powder mixer including a stirring blade therein as a preferred powder mixing device include a Rocky mixer (manufactured by MATSUBO CO., LTD.).

[0086] Hereinafter, the activation agent used in this step will be described in detail.

[0087] <Activation treatment agent>

[0088] The activation agent contains one or more alkali metal compounds. When the alkali metal compound comes into contact with the active material, the active material can be activated. When the alkali metal compound in the activation agent contains a molten portion, the molten portion improves contact with the active material, further promoting activation of the active material.

[0089] In addition, the electrode composite material sometimes contains a fluorine-containing compound derived from the binder and / or the electrolyte. By contacting the fluorine-containing compound with the activation agent, the fluorine component is stabilized as an alkali metal fluoride, thereby suppressing the generation of corrosive gases such as hydrogen fluoride. It should be noted that it is also preferable to prevent the generation of hydrogen fluoride from reducing the activity of the active material.

[0090] The proportion of the alkali metal compound in the activation agent is appropriately set in consideration of the type of alkali metal compound, the type of active material to be used, etc., and is generally 50% by weight or more, preferably 70% by weight or more (including 100% by weight) relative to the total weight of the activation agent.

[0091] Examples of the alkali metal compound serving as a component of the activation agent include hydroxides, borates, carbonates, oxides, peroxides, superoxides, nitrates, phosphates, sulfates, chlorides, vanadates, bromates, molybdates, and tungstates of alkali metals. These can be used alone or in combination.

[0092] The alkali metal element constituting the alkali metal compound may be any alkali metal element, and is preferably at least one selected from the group consisting of lithium, sodium, and potassium. It should be noted that when the activation agent comprises two or more alkali metal compounds, the alkali metal compounds may comprise different alkali metal elements.

[0093] Specific examples of preferred alkali metal compounds include hydroxides such as LiOH, NaOH, KOH, RbOH, and CsOH;

[0094] Boron oxides such as LiBO2, NaBO2, KBO2, RbBO2, CsBO2;

[0095] Carbonates such as Li2CO3, Na2CO3, K2CO3, RbCO3, and CsCO3;

[0096] Oxides such as Li2O, Na2O, K2O, Rb2O, and Cs2O;

[0097] Peroxides such as Li2O2, Na2O2, K2O2, Rb2O2, and Cs2O2;

[0098] Superoxides such as LiO2, NaO2, KO2, RbO2, CsO2, etc.;

[0099] Nitrates such as LiNO3, NaNO3, KNO3, RbNO3, CsNO3;

[0100] Phosphates such as Li3PO4, Na3PO4, K3PO4, Rb3PO4, and Cs3PO4;

[0101] Sulfates such as Li2SO4, Na2SO4, K2SO4, Rb2SO4, Cs2SO4, etc.;

[0102] Chlorides such as LiCl, NaCl, KCl, RbCl, and CsCl;

[0103] Bromides such as LiBr, NaBr, KBr, RbBr, and CsBr;

[0104] Vanadates such as LiVO3, NaVO3, KVO3, RbVO3, and CsVO3;

[0105] Molybdates such as Li2MoO4, Na2MoO4, K2MoO4, Rb2MoO4, and CsMoO4;

[0106] Tungstates such as Li2WO4, Na2WO4, K2WO4, Rb2WO4, CsWO4, etc.

[0107] Here, in order to further enhance the activation effect of the active material, at least one alkali metal compound contained in the activation agent may contain the same alkali metal element as that contained in the active material in the electrode composite.

[0108] That is, when the active material in the electrode composite is a lithium composite oxide, the alkali metal compound in the activation agent (at least one of which when there are two or more) may be a lithium compound. Preferred lithium compounds include LiOH, LiBO2, Li2CO3, Li2O, Li2O2, LiO2, LiNO3, Li3PO4, Li2SO4, LiCl, LiVO3, LiBr, Li2MoO4, and Li2WO4.

[0109] Furthermore, when the active material in the electrode composite is a sodium composite oxide, the alkali metal compound (at least one of which, when there are two or more) in the activation agent may be a sodium compound. Preferred sodium compounds include NaOH, NaBO2, Na2CO3, Na2O, Na2O2, NaO2, NaNO3, Na3PO4, Na2SO4, NaCl, NaVO3, NaBr, Na2MoO4, and Na2WO4.

[0110] The activation agent may contain compounds other than alkali metal compounds 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 agent together with the alkali metal compound for the purpose of controlling the melting start temperature of the activation agent.

[0111] The content of compounds other than the alkali metal compound in the activation agent is selected within a range that does not significantly inhibit the effect derived from the molten alkali metal compound and is less than 50% by weight of the total weight of the activation agent.

[0112] The amount of the activation agent added to the mixture of the electrode composite and the activation agent is preferably 0.001 to 100 times, more preferably 0.05 to 1 times, the weight of the active material contained in the electrode composite.

[0113] The molar amount of the alkali compound in the activating agent in the mixture of the electrode composite and the activating agent may be 0.001 to 200 times the molar amount of the alkali atom when the molar amount of the active material (e.g., Formula A) contained in the electrode composite is set to 1.

[0114] By appropriately controlling the ratio of the activation agent in the mixture, the cost of recovering the active material from the electrode composite can be reduced, and the oxidative decomposition rate of the carbon-based conductive material or binder can be increased. Furthermore, the effect of preventing the generation of corrosive gases during the activation process can be enhanced, further increasing the discharge capacity of batteries manufactured using the resulting active material.

[0115] Furthermore, at least one of the alkali metal compounds contained in the activation agent is preferably an alkali metal compound that exhibits alkalinity when dissolved in water. When an activation 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 agent may be referred to as a "basic activation agent."

[0116] In the present invention, the use of an alkaline activation agent further suppresses the generation of corrosive gases during the heating process, thereby further increasing the discharge capacity of batteries produced using the recovered active material. Furthermore, the use of an alkaline activation agent can increase the processing speed of the carbon-based conductive material or binder.

[0117] Examples of alkali metal compounds that exhibit alkalinity when dissolved in water and are contained in the alkaline activation agent include hydroxides, carbonates, bicarbonates, oxides, peroxides, and superoxides of alkali metals. Specific examples include LiOH, NaOH, KOH, RbOH, and CsOH; Li2CO3, Na2CO3, K2CO3, RbCO3, and CsCO3; LiHCO3, NaHCO3, KHCO3, RbHCO3, and CsHCO3; Li2O, Na2O, K2O, Rb2O, and Cs2O; Li2O2, Na2O2, K2O2, Rb2O2, and Cs2O2; and LiO2, NaO2, KO2, RbO2, and CsO2. The activation agent may contain one or more of these compounds.

[0118] Furthermore, when the conductive material contained in the electrode composite is a carbon-based conductive material, at least one of the alkali metal compounds contained in the activation agent may be an alkali metal compound having an oxidizing power capable of oxidatively decomposing the carbon-based conductive material at the temperature of the activation step. It should be noted that an activation agent containing such an alkali metal compound may be hereinafter referred to as an "activation agent having oxidizing power."

[0119] If an activation agent with such oxidizing power is used, it will be particularly effective in promoting the oxidation of the conductive material of the carbon material into carbon dioxide and the oxidation of the binding material of the hydrocarbon material into carbon dioxide and water vapor. Sometimes, the discharge capacity of the battery made using the obtained active material can be further improved, and the effect of preventing the generation of corrosive gases in the activation treatment process can be improved.

[0120] Examples of alkali metal compounds having the oxidizing power required to oxidize carbon-based conductive materials and hydrocarbons into carbon dioxide and water vapor include peroxides, superoxides, nitrates, sulfates, vanadates, and molybdates of alkali metals, which can be used alone or in combination of two or more.

[0121] Specific examples include Li2O2, Na2O2, K2O2, Rb2O2, Cs2O2; LiO2, NaO2, KO2, RbO2, CsO2; LiNO3, NaNO3, KNO3, RbNO3, CsNO3; Li2SO4, Na2SO4, K2SO4, Rb2SO4, Cs2SO4; LiVO3, NaVO3, KVO3, RbVO3, CsVO3; Li2MoO4, Na2MoO4, K2MoO4, Rb2MoO4, CsMoO4.

[0122] The details of the oxidizing power of these alkali metal compounds are described in Japanese Patent Application Laid-Open No. 2012-186150.

[0123] Step (2): <Step of heating the mixture>

[0124] The heating step is a step of heating the mixture obtained in step (1) (hereinafter sometimes referred to as "pre-heated mixture") to a temperature not lower than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.3 atm or higher.

[0125] In addition, "the melting start temperature (Tmp) of the activation agent" means the lowest temperature at which a part of the activation agent appears in a liquid phase.

[0126] In the present invention, the melting onset temperature (Tmp) of the activation agent is a value determined by differential thermal analysis (DTA). Specifically, the melting onset temperature (Tmp) is determined by measuring 5 mg of the above mixture using differential thermal analysis (DTA, measurement conditions: heating rate: 10°C / min) at which the DTA signal shows an endothermic peak.

[0127] The melting start temperature (Tmp) of the activation agent is preferably 700° C. or lower, and may be 600° C. or lower. There is no lower limit for the melting start temperature (Tmp) of the activation agent, and it may be 150° C., for example.

[0128] The melting point of the activation agent refers to the lowest temperature at which a portion of the activation agent appears in a liquid phase when the activation agent is heated alone. By mixing the electrode composite with the activation agent, the melting start temperature of the activation agent becomes lower than the melting point of the activation agent.

[0129] In the present invention, the melting point of the activation agent is determined by differential thermal analysis (DTA). Specifically, the melting point of the activation agent is determined by measuring 5 mg of the activation agent using differential thermal analysis (DTA, measurement conditions: heating rate: 10°C / min) at the temperature at which the DTA signal shows an endothermic peak.

[0130] The atmosphere during heating can have an oxygen partial pressure of 0.3 atm or more, and can be 0.4 atm or more, 0.5 atm or more, 0.6 atm or more, 0.7 atm or more, 0.8 atm or more, 0.9 atm or more, or 1.0 atm or more. It should be noted that 1 atm is 101325 Pa. The total pressure of the atmosphere is not particularly limited, but can be set to atmospheric pressure, a reduced pressure atmosphere, or a pressurized atmosphere.

[0131] Examples of gases other than oxygen in the atmosphere include nitrogen, argon, and carbon dioxide.

[0132] In step (2), by heating the mixture to a temperature equal to or higher than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.3 atm or higher as described above, the following effects occur.

[0133] By bringing the molten activation agent into contact with the active material in an atmosphere with a high oxygen partial pressure, degradation of the active material's crystal structure can be suppressed and, depending on the circumstances, the crystal structure can be repaired.

[0134] In addition, by bringing the molten activation agent into contact with the carbon-based conductive material or the binder, the rate of oxidative decomposition of the conductive material and the binder is increased. Furthermore, by bringing the molten activation agent into contact with the fluorine compound derived from the binder and the electrolyte, the fluorine component is stabilized as an alkali metal fluoride, thereby preventing the generation of hydrogen fluoride as a corrosive gas and suppressing the degradation of the crystal structure of the active material.

[0135] Furthermore, when the activation agent contains the same alkali metal as the active material, it is also possible to supply the alkali metal that is insufficient relative to the active material.

[0136] The temperature of the heating process and the holding time at that temperature can be appropriately adjusted by the type or combination of the active material, conductive material, binder, and alkali metal compound or other compound contained in the activation agent that constitutes the electrode composite. Typically, the temperature is in the range of 100 to 1500°C, and the holding time is about 10 minutes to 24 hours.

[0137] The above temperature is preferably a temperature higher than the melting point of the alkali metal compound contained in the activation agent. It should be noted that the melting point of the alkali metal compound may be lower than the melting point of each compound alone by mixing multiple compounds. When the activation agent contains two or more alkali metal compounds, the eutectic point is set to the melting point of the alkali metal compound.

[0138] After the heating step, the mixture may be cooled to any temperature, for example, around room temperature, as needed.

[0139] Step (3): <Step of recovering the active material>

[0140] Step (3): The step of recovering the active material is a step of recovering the active material from the mixture after the heating step in step (2).

[0141] The mixture that has undergone the heating process includes, in addition to the active material, components derived from the activation treatment agent (such as alkali metal compounds), undecomposed conductive materials, binders, and undecomposed products of other electrode composite materials. In addition, when the electrode composite contains an electrolyte containing a fluorine component, it sometimes also contains a fluorine component derived from the electrolyte.

[0142] Methods for separating and recovering active substances from a mixture that has undergone a heating step include a slurry-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 the mixture is heated to vaporize and separate components other than the active substance.

[0143] Hereinafter, the slurry solid-liquid separation method, which is a preferred method in the active material recovery step, will be described in detail.

[0144] <Slurry solid-liquid separation method>

[0145] The active material recovery process using the slurry solid-liquid separation method includes: a slurrying process of adding a solvent to the mixture obtained after the activation treatment process to prepare a slurry; a solid-liquid separation process of separating the slurry into a solid phase and a liquid phase; and a drying process of drying the solid phase after the solid-liquid separation.

[0146] This method is particularly suitable for recovering active substances that are insoluble in water.

[0147] The slurrying step is a step of adding a solvent to the mixture after the activation treatment to prepare a slurry.

[0148] The solvent used in the slurrying step is not limited as long as it is a solution that can dissolve the components other than the active substance contained in the mixture. As the solvent, water is preferably inexpensive and easy to use industrially. In order to increase the solubility of the water-soluble component or to increase the processing speed, components other than water can also be added to adjust the pH.

[0149] In the slurrying step, a slurry is prepared that includes a solid phase primarily containing the active material and a liquid phase containing water-soluble components other than the active material. The liquid phase may contain alkali metal components derived from the activation agent and / or fluorine components derived from the binder and electrolyte.

[0150] The amount of the solvent added to the mixture is appropriately determined in consideration of the amounts of the active substance and water-soluble components other than the active substance contained in the mixture.

[0151] The slurry formed in the slurrying step is then subjected to a solid-liquid separation step. The solid-liquid separation step is a step for separating the slurry into a liquid phase and a solid phase. The solid-liquid separation method may be any conventional method, such as filtration or centrifugation.

[0152] The drying step is a step of drying the active material obtained after the solid-liquid separation step to remove the solvent (water).

[0153] The drying temperature is preferably 100°C or higher to remove the solvent (water). Furthermore, it is preferably set to 150°C or higher to fully remove water. A temperature of 250°C or higher is particularly preferred because it further improves the discharge capacity of batteries fabricated using the resulting active material. The temperature during the drying step may be constant, or it may be varied in stages or continuously.

[0154] After drying, the active material may be re-fired in an oxygen-containing atmosphere. The re-fired atmosphere may be, for example, air. Alternatively, the re-fired process may be performed in an atmosphere having an oxygen partial pressure of 0.3 atm or higher, similar to the heating process.

[0155] In addition, the re-firing temperature can be set to 100 to 1500°C.

[0156] Furthermore, the holding time of the re-firing can be set to 1 minute to 24 hours.

[0157] The active material obtained from the battery mixture by using the method for producing an active material of the present invention can be reused in the same manner as unused active material. Methods for producing electrodes and batteries using active materials are well known.

[0158] The discharge capacity of the recovered active material can be 150 mAh / g or more.

[0159] The molar ratio of the alkali metal to the transition metal in the produced active material is preferably equal to or greater than the molar ratio in the active material in the electrode composite. By increasing the ratio of the alkali metal, the discharge capacity of the battery produced using the obtained active material can be increased.

[0160] Example

[0161] Hereinafter, the present invention will be described in more detail with reference to Examples. However, the present invention is not limited to the following Examples unless the gist of the invention is changed.

[0162] The physical properties of the active material (before the production of the electrode composite) were measured, and a charge and discharge test of a battery using the active material as a positive electrode active material was performed as follows.

[0163] (1) Composition analysis

[0164] After dissolving the sample in hydrochloric acid, the composition was analyzed by inductively coupled plasma atomic emission spectrometry (hereinafter sometimes referred to as ICP-AES) (using SPS3000 manufactured by SII Nano Technology Co., Ltd.).

[0165] (2) Powder X-ray diffraction measurement

[0166] For the powder X-ray diffraction measurement of the sample, a Spectris Corporation powder X-ray diffraction measurement device X'PertPRO was used. As the X-ray source, a CuKα ray source was used. The active material was filled into a dedicated holder and the diffraction angle was carried out in the range of 2θ = 10 to 90° to obtain a powder X-ray diffraction pattern. Based on the obtained powder X-ray diffraction pattern, the lattice constant was refined by the least squares method using PDXL2 software manufactured by Rigaku Co., Ltd. to obtain the interplanar spacing of the (110) plane.

[0167] Measuring device: X'PertPRO powder X-ray diffraction measuring device manufactured by Spectris Corporation

[0168] X-ray generator: CuKα ray source voltage 45kV, current 40mA

[0169] Slit: 1°

[0170] Scan step: 0.02deg

[0171] Scanning range: 10-90 degrees

[0172] Scanning speed: 4deg / min

[0173] X-ray detector: one-dimensional semiconductor detector

[0174] Measurement atmosphere: atmospheric atmosphere

[0175] Sample stage: dedicated glass sample plate

[0176] (3) Determination of pH of activation agent

[0177] 3.5 g of an activation agent was added to 70 g of pure water, and the mixture was sufficiently stirred with a stirrer. The pH was measured using a pH meter using a glass electrode.

[0178] (4) Determination of the melting start temperature of the activation agent by differential thermal analysis (DTA)

[0179] 5 mg of the mixture of the electrode mixture and the activation agent was subjected to differential thermal analysis (DTA, measurement conditions: heating rate: 10°C / min), and the temperature at which the DTA signal showed an endothermic peak was defined as the melting onset temperature (Tmp).

[0180] Differential thermal analysis (DTA) measurement conditions

[0181] Apparatus: Differential thermal and thermogravimetric simultaneous measuring apparatus (TG / DTA6200) manufactured by Seiko Instruments Co., Ltd.

[0182] Plate: Platinum

[0183] Initial sample volume: 5 mg

[0184] Atmosphere: Air

[0185] Heating rate: 10℃ / min

[0186] (5) Charge and discharge test

[0187] 1. Preparation of electrode (positive electrode)

[0188] In order to measure the discharge capacity of the active material, an electrode (positive electrode) was prepared according to the following procedure.

[0189] The active material, binder (PVdF#1100 (manufactured by KUREHA Co., Ltd.)), and conductive material (acetylene black (manufactured by Denka Kagaku Kogyo Co., Ltd., product number: DENKA BLACK HS100) were mixed so that the weight ratio of active material: binder: conductive material was 92:3:5, respectively, and kneaded in an agate mortar to prepare a positive electrode composite paste.

[0190] The binder solution was an NMP solution in which PVdF as a binder was dissolved, and NMP was added so that the total weight of the active material, the conductive material, and the binder in the positive electrode composite paste would be 50 wt %.

[0191] The positive electrode material paste was prepared so that the electrode material amount became 3 mg / cm 2 After coating on an Al foil current collector (3×5 cm) in a molten-crystal manner, vacuum drying was performed at 150° C. for 8 hours to obtain a positive electrode.

[0192] 2. Battery production

[0193] The positive electrode, electrolyte, separator, and negative electrode were combined to produce a non-aqueous electrolyte secondary battery (coin-shaped battery R2032). The battery was assembled in an argon atmosphere glove box.

[0194] As the electrolyte solution, a solution prepared by dissolving LiPF 6 as an electrolyte in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 30:70 so as to give 1 mol / L was used.

[0195] As the separator, a laminated film separator was used in which a heat-resistant porous layer was laminated on a polyethylene porous film. In addition, metallic lithium was used as the negative electrode.

[0196] 3. Charge and discharge test

[0197] Using the produced coin-shaped battery, a charge and discharge test was performed under the following conditions while maintaining at 25° C. In the charge and discharge test, the discharge current during discharge was changed to measure the discharge capacity.

[0198] Maximum charging voltage: 4.3V

[0199] Charging time: 8 hours

[0200] Charging current: 40mA / g-active material (charging current per 1g of active material is 40mA)

[0201] During discharge, the minimum discharge voltage was kept constant at 2.5 V, and the discharge current was changed in each cycle as follows.

[0202] Discharge of the first cycle (0.2C): discharge current 40 mA / g-active material

[0203] Discharge of the second cycle (0.2C): discharge current 40 mA / g-active material

[0204] Discharge of the 3rd cycle (1C): discharge current 200 mA / g-active material

[0205] Discharge of the 4th cycle (2C): discharge current 400mA / g-active material

[0206] Discharge of the 5th cycle (5C): discharge current 1000mA / g-active material

[0207] Discharge of the 6th cycle (10C): discharge current 2000mA / g-active material

[0208] It should be noted that a larger 0.2C discharge capacity indicates a higher rated capacity, and a larger 5C discharge capacity indicates a higher output characteristic.

[0209] (Examples and Comparative Examples)

[0210] A. Preparation of positive electrode A

[0211] As the active material, a composition of Li 1.06 Ni 0.80 Co 0.11 Mn 0.09 O2, a positive electrode active material having an R-3m crystal structure. In a charge-discharge test of a coin-type battery using this active material (unused active material) as a positive electrode active material, a discharge capacity at 0.2C was measured to be 184 mAh / g.

[0212] In addition, as another active material, a composition of Li 1.04 Ni 0.34 Co0.33 Mn 0.33 O2, a positive electrode active material having an R-3m crystal structure. In a charge-discharge test of a coin-type battery using this active material (unused active material) as a positive electrode active material, a discharge capacity at 0.2C was measured to be 150 mAh / g.

[0213] Acetylene black HS100 (manufactured by Denki Kagaku Kogyo Co., Ltd.) was used as the conductive material.

[0214] As the binder and the solvent, NMP solvent was further added to an NMP solution (manufactured by KUREHA CO., LTD.) containing 12 wt% of PVdF#1100 as a binder to set a predetermined ratio.

[0215] The mass ratio of the active material, binder, and conductive material in the positive electrode mixture was set to 92:3:5. The amount of the solvent blended was set to 50% by mass relative to the total amount of the positive electrode mixture paste.

[0216] The positive electrode composite material paste was applied to a 20 μm thick aluminum foil 1085 (manufactured by Nippon Foil Co., Ltd.) for positive electrode current collectors of lithium ion secondary batteries using a doctor blade coater and dried to obtain a positive electrode A. The amount of electrode composite material on the aluminum foil was 20 mg / cm 2 .

[0217] B. Recover the electrode mixture from the positive electrode A

[0218] The electrode composite was mechanically scraped off from the positive electrode A to separate the electrode composite from the current collector.

[0219] C. Activation agent mixing process

[0220] An activation agent (one or more alkali metal compounds) was added to the stripped electrode mixture in a predetermined ratio and mixed in a mortar to form a mixture. Table 1 shows the composition of the activation agent, the molar ratio of each alkali metal compound in the electrode mixture relative to one mole of active material, the pH of the activation agent, and the melting onset temperature of the activation agent, which was measured separately in the mixture.

[0221] D. Heating process

[0222] The obtained mixture (mixture before activation treatment) is placed in an alumina sintering container and placed in an electric furnace. Under atmospheric pressure, in an atmosphere containing a predetermined concentration of oxygen concentration, it is heated to a predetermined temperature. The holding time of the temperature is set to 4 hours, the heating rate to the temperature is set to 250°C / hour, and the cooling to room temperature is set to natural cooling. It should be noted that the adjustment of the oxygen concentration in the atmosphere is carried out by adding additional oxygen relative to the air. The heating temperature, total pressure, oxygen concentration, and oxygen partial pressure are shown in Table 1.

[0223] E. Active Substance Recovery Process

[0224] The activated mixture was pulverized, water was added to form a slurry, stirred, and then decanted. The slurry was then filtered to separate the solid phase. The resulting solid phase was vacuum dried at 100°C.

[0225] The (110) interplanar spacing of the recovered active material (active material after treatment) and the active material before manufacturing the positive electrode A (active material before treatment) was measured by powder X-ray diffraction measurement, and the discharge capacity was measured by charge and discharge testing.

[0226] The conditions are shown in Table 1, and Table 2 shows the (110) interplanar spacing and the discharge capacity at 0.2 C of the active material before and after treatment in each of Examples and Comparative Examples.

[0227]

[0228] Table 2

[0229]

[0230] It was confirmed that the Example showed a small change in the (110) interplanar spacing and little degradation of the crystal structure. On the other hand, it was confirmed that the Comparative Example showed a large change in the (110) interplanar spacing and significant degradation of the crystal structure. The discharge capacity also showed a similar trend.

Claims

1. A method for producing an active substance, comprising the following steps: (1) A step of mixing an activation agent containing one or more alkali metal compounds into an electrode composite material containing an active material and a binder; (2) heating the obtained mixture to a temperature not lower than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.3 atm or higher; and (3) a step of recovering the active substance from the heated mixture, The active material is Li 1+a M 2 b M 1 M T c O 2+d X e The composite oxide represented by in, 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 other than Ni, Co, Mn, and Fe, X represents at least one element selected from the group consisting of non-metallic elements excluding oxygen O and P, It satisfies -0.4<a<1.5, 0≤b<0.5, 0≤c<0.5, -0.5<d<1.5, and 0≤e<0.

5.

2. The method for producing an active material according to claim 1, wherein: The active material is a positive electrode active material.

3. The method for producing an active material according to claim 2, wherein: The positive electrode active material is a positive electrode active material of a non-aqueous secondary battery.

4. The method for producing an active material according to any one of claims 1 to 3, wherein The obtained mixture is heated to a temperature equal to or higher than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.5 atm or more.

5. The method for producing an active material according to any one of claims 1 to 3, wherein The obtained mixture is heated to a temperature equal to or higher than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.7 atm or more.

6. The method for producing an active material according to any one of claims 1 to 3, wherein The obtained mixture is heated to a temperature equal to or higher than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 0.9 atm or more.

7. The method for producing an active material according to any one of claims 1 to 3, wherein The obtained mixture is heated to a temperature equal to or higher than the melting start temperature of the activation agent in an atmosphere having an oxygen partial pressure of 1.0 atm or higher.

8. The method for producing an active material according to any one of claims 1 to 3, wherein The amount of the activation agent added to the mixture of the electrode composite and the activation agent is 0.05 to 1 times the weight of the active material contained in the electrode composite.

9. The method for producing an active material according to any one of claims 1 to 3, wherein The M in the composite oxide 1 The molar fraction of Ni contained in the molten metal is 0.5 or more.

10. The method for producing an active material according to any one of claims 1 to 3, wherein The composite oxide has a hexagonal crystal structure.

11. The method for producing an active material according to any one of claims 1 to 3, wherein The discharge capacity of the recovered active material was 150 mAh / g or more.

12. The method for producing an active material according to any one of claims 1 to 3, wherein At least one alkali metal compound contained in the activation agent contains the same alkali metal element as the alkali metal element contained in the active material.

13. The method for producing an active material according to any one of claims 1 to 3, wherein At least one of the alkali metal compounds contained in the activation agent is an alkali metal compound that exhibits basicity when dissolved in water.

14. The method for producing an active material according to claim 13, wherein: The alkali metal compound showing alkalinity when dissolved in water is one or more selected from the group consisting of hydroxides, carbonates, hydrogen carbonates, oxides, peroxides, and superoxides of alkali metals.

15. The method for producing an active material according to any one of claims 1 to 3, wherein The activation agent has a melting start temperature of 700° C. or lower.

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