JP2023093984A - Method for producing resin composition for secondary battery - Google Patents

Abstract

To produce a resin composition for a secondary battery which can achieve excellent battery characteristics without lowering battery performance due to short circuit even when a metal foreign matter such as copper is mixed therein.SOLUTION: A method for producing a resin composition for a secondary battery containing a polymer and a dispersion medium includes a step of oxidizing a metal component contained in the resin composition for the secondary battery. The step of oxidizing the metal component is a step of bringing oxygen gas into contact with the resin composition for the secondary battery.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a resin composition for secondary batteries.

Lithium ion secondary batteries are widely used as batteries for electric vehicles, mobile devices, and the like. 2. Description of the Related Art As electric vehicles, portable devices, and the like become more sophisticated, demands for lithium-ion secondary batteries to achieve high capacity, high output, and reduction in size and weight are increasing year by year.

The electrode of the lithium ion secondary battery consists of a positive electrode in which an electrode mixture consisting of a positive electrode active material containing lithium ions, a conductive material, a binder, etc. is adhered to the surface of a metal foil current collector, and a lithium ion desorption electrode. A negative electrode is used in which an electrode mixture composed of an insertable negative electrode active material, a conductive material, a binder, and the like is adhered to the surface of a current collector made of metal foil.
The capacity of a lithium ion secondary battery depends on the positive electrode active material and the negative electrode active material, which are the main materials, and the capacity can be increased by increasing the filling amount of the electrode active material in the electrode film. Therefore, attempts have been made to increase the capacity of the battery by increasing the filling of the active material while ensuring the conductivity and binding properties.

On the other hand, in lithium ion secondary batteries, deterioration in battery performance due to reduction/precipitation of metal components on the negative electrode, and excessive heat generation and ignition due to occurrence of short circuits are also important problems. Factors that cause performance deterioration and short circuits due to metal components include (1) contamination of metal impurities derived from the manufacturing process (for example, those derived from stainless steel used in transportation piping, etc.), conductive materials, resins (dispersants, binders, etc.). In addition, (2) metal ions contained in the positive electrode, current collector, battery container, etc. are eluted into the electrolyte, and then reduced and deposited on the negative electrode. and (3) metal ions are eluted from the positive electrode active material due to deterioration of the positive electrode, and are reduced and deposited on the negative electrode. In particular, in applications involving large-sized batteries, such as automobile applications, serious accidents may occur, so there is an increasing need to prevent or eliminate the contamination of fine metal particles more strictly.

Patent Literature 1 proposes a method of removing particulate metal components in a resin composition for secondary batteries by magnetic force, although the purpose is different. However, according to the method of the present invention, a magnetic metal such as iron can be recovered by magnetic force even if mixed, while a non-magnetic metal such as copper can be removed after mixing. is difficult.

Various additives have been investigated in order to suppress the elution of metal ions into the electrolytic solution and the deposition of foreign substances on the negative electrode when metal impurities such as copper that do not have magnetism are mixed. Patent Document 2 proposes an alkaline battery in which a chelating agent such as EDTA is added to the positive electrode mixture of the alkaline battery. In this invention, by adding a chelating agent to the positive electrode mixture, even if copper, which is a metal impurity in the positive electrode mixture, is ionized, copper ions are complexed to prevent elution. is done. However, since the chelating agent diffuses through the electrolytic solution and captures the ionized active material by chelate formation, there are problems such as a decrease in the capacity of the active material and a corresponding decrease in discharge capacity, and the present invention is insufficient.

WO2010/032784 JP 2008-21497 A

In view of the above circumstances, the present invention provides a secondary battery resin composition that can achieve excellent battery characteristics without deterioration of battery performance due to short circuit or the like even if metal foreign matter such as copper is mixed. is the issue.

As a result of intensive studies to solve the above problems, the present inventors have found that by oxidizing the metallic foreign matter in the resin composition for secondary batteries, the performance of the battery does not deteriorate due to short circuit or the like even if the metallic foreign matter is mixed. The inventors have found that a battery with excellent performance can be realized, and have completed the present invention.

The present invention relates to a method for producing a resin composition for a secondary battery containing a polymer and a dispersion medium,
The present invention relates to a method for producing a resin composition for secondary batteries, including a step of oxidizing a metal component contained in the resin composition for secondary batteries.

The present invention relates to a method for producing a secondary battery resin composition, wherein the step of oxidizing the metal component is a step of contacting the secondary battery resin composition with oxygen gas.

The present invention relates to a method for producing the resin composition for secondary batteries, wherein the flow rate of the oxygen gas blown is 20 NL/h or more per 1 m ³ of the resin composition for secondary batteries.

The present invention also relates to a method for producing the resin composition for a secondary battery, which further contains a conductive material.

The present invention also relates to a method for producing the resin composition for secondary batteries, which further contains an inorganic acid and/or an inorganic base.

The present invention relates to a method for producing a secondary battery electrode slurry composition containing the secondary battery resin composition obtained by the above production method and an electrode active material.

The present invention relates to a method for producing an electrode film, in which the slurry composition for a secondary battery electrode obtained by the above production method is applied.

The present invention relates to a method for producing a battery electrode, which comprises forming an electrode film obtained by the above production method on an electrode substrate.

The present invention relates to a method for manufacturing a lithium ion secondary battery using the battery electrode obtained by the manufacturing method.

ADVANTAGE OF THE INVENTION According to this invention, the resin composition for secondary batteries which can achieve the outstanding battery characteristic can be provided without deteriorating battery performance by a short circuit etc. even if metal foreign substances, such as copper, mix.

FIG. 1 shows an embodiment of a manufacturing line (manufacturing line (A)) of a binder composition for secondary batteries. FIG. 2 shows an embodiment of a manufacturing line (manufacturing line (B)) of a binder composition for secondary batteries. FIG. 3 shows one implementation of a manufacturing line (manufacturing line (C)) of a binder composition for secondary batteries.

The details of the present invention are described below. In this specification, "N-methyl-2-pyrrolidone" is referred to as "NMP", "positive electrode active material or negative electrode active material" is referred to as "electrode active material" or "active material", and "battery containing active material and resin composition for battery" may be abbreviated as "battery mixture slurry", "mixture slurry" or "mixture composition".

<Resin composition for secondary battery>
The resin composition for secondary batteries in the present invention contains a polymer and a dispersion medium (solvent). That is, the resin composition for a secondary battery contains at least a polymer and a dispersion medium (solvent), and further contains optional components such as a conductive material, a base, and an acid that can be blended in a secondary battery electrode. good too.

<Polymer>
The polymer in the present invention is not particularly limited, and regardless of whether it is a commercial product or a synthetic product, it can be used alone or in combination of two or more. It is preferable that the polymer is mainly contained as a dispersant for suitably dispersing the conductive material and the electrode active material.
Although not particularly limited, examples of the polymer that functions well in N-methyl-2-pyrrolidone (NMP) solvent include polyvinylpyrrolidone, polyvinyl acetal, polyvinyl alcohol, and hydrogenated nitrile rubber. . Moreover, carboxymethyl cellulose, acrylic acid, etc. can be used as a polymer that functions favorably in water.

When dispersing the carbon-based conductive material using a polymer, it is possible to uniformly disperse the carbon-based conductive material in the dispersion medium (solvent) by adding a sufficient amount of the polymer to the carbon-based conductive material. Become. When the amount of the carbon-based conductive material contained in the secondary battery resin composition is 100% by mass, the total amount of the polymer used for the dispersion treatment of the carbon-based conductive material is 1% by mass or more and 200% by mass or less. Preferably. By blending the polymer in this amount ratio, it becomes possible to express good conductivity as a resin composition for a secondary battery. Polymers are non-conductive components and generally have low electrochemical stability and resistance to non-aqueous electrolytes when used in lithium-ion secondary batteries. Therefore, when the blending ratio of the polymer is 200% by mass or more, even if the initial properties are good, the properties may deteriorate over time. The blending ratio of the polymer is desirably as small as possible within a range in which the carbon-based conductive material can be suitably dispersed.

The content of the polymer contained in the secondary battery resin composition is 0.05 mass based on the mass of the secondary battery resin composition (assuming the mass of the secondary battery resin composition is 100% by mass). % or more is preferable, and 0.1 mass % or more is more preferable. Moreover, 30 mass % or less is preferable and 20 mass % or less is more preferable. By setting the content of the polymer contained in the resin composition for a secondary battery within the above range, sedimentation and gelation can be prevented, which is useful from the viewpoint of storage stability. In addition, the content of the polymer is appropriately adjusted so as to obtain a resin composition for a secondary battery exhibiting an appropriate viscosity, taking into consideration the affinity for the dispersion medium and the workability of the process of dispersing the conductive material. is preferred.

The viscosity of the resin composition for secondary batteries is not particularly limited, but the viscosity at 60 rpm in a Brookfield viscometer is preferably in the range of 5 to 10000 mPa·s. By setting the viscosity of the resin composition for a secondary battery within the above range, workability in production is improved. In addition, clogging of the production line can be prevented.

Moreover, the polymer may further contain a component other than the above-described dispersant, and examples thereof include a component that mainly functions as a binder. Binders are resins that can bind substances such as electrode active materials and conductive materials in the electrode film. Examples include ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, and acrylic acid. , acrylic ester, methacrylic acid, methacrylic ester, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc. as structural units; polyurethane resin, polyester resin, phenol resin, epoxy resin, phenoxy Resins such as resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicon resins, fluorine resins; cellulose resins such as carboxymethyl cellulose; rubbers such as styrene-butadiene rubbers and fluorine rubbers; conductive resin such as Modified products, mixtures or copolymers thereof may also be used. Among these, polymers or copolymers having fluorine atoms in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene, are preferred from the standpoint of durability when used as a binder for a positive electrode film. When used as a binder for the negative electrode film, styrene-butadiene rubber, polyacrylic acid, etc., which have good adhesion, are preferable.

The weight average molecular weight of the binder is preferably from 10,000 to 2,000,000, more preferably from 100,000 to 1,000,000, even more preferably from 200,000 to 1,000,000.

<Dispersion medium (solvent)>
The dispersion medium (solvent) in the present invention is not particularly limited, but examples include alcohols, glycols, cellosolves, aminoalcohols, amines, ketones, carboxylic acid amides, phosphoric acid amides, sulfoxides, carboxylic acid acid esters, phosphate esters, ethers, nitriles, water and the like. A mixed solvent consisting of two or more of these may also be used. Among them, N-methyl-2-pyrrolidone (NMP) and water are often used for producing electrodes of lithium ion secondary batteries.

<Metal component (metallic foreign matter)>
The metal component (metallic foreign matter) in the present invention will be described. The state of existence of the metal component is not particularly limited, and may be a metal, its oxide, or an alloy such as brass or bronze. Copper is mentioned as a representative metal component. Also, the route of mixing the metal component is not particularly limited. For example, contamination derived from raw materials (conductive materials and polymers) constituting the resin composition for secondary batteries, and contamination during composition preparation processes such as charging and mixing can be mentioned. Carbon black and carbon-based conductive materials such as carbon nanotubes often contain a large amount of metal components derived from their manufacturing processes (as manufacturing equipment and catalysts). The present invention can be preferably applied when the resin composition for a secondary battery contains 10 ppb or more of metal component based on the mass. The effect of the present invention can be obtained regardless of the content of the metal component, although there is a difference in the effect.

<Step of oxidizing metal component>
The present invention includes a step of oxidizing the metal component contained in the resin composition for secondary batteries. The step of oxidizing the metal component is not particularly limited. Examples thereof include electrochemical methods and chemical treatment methods using additives such as acids and bases. Among them, a method of contacting with oxygen gas is preferable, and a method of blowing oxygen gas while stirring the resin composition for a secondary battery to mix gas and liquid is preferable.

A method for stirring the resin composition for a secondary battery is not particularly limited, but generally a disper (stirring blade) or the like is used. Although there are various types such as a propeller type and a turbine type as the shape, there is no particular limitation as long as the resin composition for a secondary battery can be uniformly stirred. The stirring speed is preferably 0.5 m/s or more, and is determined by appropriately adjusting the size and rotation speed of the stirring blade. A stirring speed of 0.5 m/s or more is preferable because the resin composition for a secondary battery and oxygen gas can be sufficiently gas-liquid mixed. The upper limit of the stirring speed is not particularly limited, and may be appropriately set within a range allowed in the process of actual operation. The conditions under which the secondary battery resin composition and oxygen gas are sufficiently gas-liquid mixed cannot be uniquely determined, but the viscosity of the secondary battery resin composition, the production scale, and the tank content In addition, the size and number of revolutions of the stirring blade, the shape of the stirring blade, the distance from the bottom of the tank, etc. are appropriately adjusted, and are set so as to achieve the object of the present invention.

Although the method of blowing oxygen (air) gas is not particularly limited, for example, production lines as shown in FIGS. 1 to 3 are conceivable. FIG. 1 shows a case where oxygen (air) gas is directly blown from the top of a tank containing a resin composition for secondary batteries. FIG. 2 shows a case where a static mixer is attached to the tank via a pipe, and oxygen (air) gas is blown directly into the composition while circulating the secondary battery resin composition in the tank with a pump. ing. FIG. 3 shows a case where a bubbler is installed in the lower part of the tank and oxygen (air) gas is blown directly into the resin composition for secondary batteries in the tank. The size, length, diameter, and the like of the gas introduction pipe may be set so as to achieve the object of the present invention, taking into account the production scale of the resin composition for secondary batteries and the internal capacity of the tank.

A static mixer is a stationary mixer that does not have a driving means, and has 6 to 10 guides (obstruction plates) called elements arranged in a spiral inside. A turbulent flow is generated by flowing along the twisted surface of the oxygen (air) gas, and the oxygen (air) gas is dispersed at high speed to form small bubbles, promoting dispersion and dissolution in the dispersion medium. For example, Noritake Co., Ltd. sells a variety of gas-liquid mixture types, which can be selected and used according to the pipe diameter, circulating gas flow rate, scale, and the like.

In the present invention, the blowing flow rate of oxygen gas is preferably 20 NL/hour (hereinafter referred to as h) or more per 1 m ³ of the resin composition for secondary batteries. It is preferably 100 NL/h or more, more preferably 300 NL/h or more. When compressed air is used as a substitute for oxygen gas, it is preferably 100 NL/h or more per 1 m ³ calculated from the ratio of oxygen in air (approximately 20%). A preferable range is similarly 500 NL/h or more, more preferably 1500 NL/h or more.

NL (Normal Liters) represents the scientific gas volume measured under the conditions of atmospheric pressure 0.1013 MPa (1 atm), temperature 0° C., and relative humidity 0%. When calculating the volume under actual use (production) conditions, it is possible to approximate the calculation from the ideal gas equation of state. For example, the volume of gas at atmospheric pressure of 0.1013 MPa (1 atm) and temperature of 25° C. is approximately 1.080 L.

<Conductive material (carbon-based conductive material)>
The resin composition for secondary batteries may further contain a conductive material. The conductive material in the present invention is a carbon-based conductive material. The carbon-based conductive material is not particularly limited as long as it is a conductive carbon material, and graphite, carbon black, carbon nanotubes, carbon nanofibers, carbon fibers, fullerenes, etc. may be used singly or in combination of two or more. Can be used together. The conductive material is a substance (material) different from the electrode active material described later.

As carbon black, various kinds of commercially available acetylene black, furnace black, hollow carbon black, channel black, thermal black, ketjen black, etc. can be used. Further, carbon black may be neutral, acidic or basic, and oxidized carbon black or graphitized carbon black may be used.

Carbon nanotubes (CNT) include flat graphite rolled into a cylindrical shape, single-walled carbon nanotubes, and multi-walled carbon nanotubes, and these may be mixed. A single-walled carbon nanotube has a structure in which a single layer of graphite is wound. Multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wound. Also, the side wall of the carbon nanotube need not have a graphite structure. Carbon nanotubes with sidewalls having, for example, an amorphous structure are also carbon nanotubes herein.

The shape of carbon nanotubes is not limited. Such shapes include a variety of shapes including needles, cylindrical tubes, fish bones (fish bones or cup stacks), tramp (platelets) and coils. In the present embodiment, the shape of the carbon nanotube is preferably needle-like or cylindrical tube-like. Carbon nanotubes may be of a single shape or a combination of two or more shapes.

Examples of forms of carbon nanotubes include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. The carbon nanotubes may have a single form or a form in which two or more of these forms are combined.

The carbon purity of the carbon-based conductive material can be determined by general CHN elemental analysis, and is expressed by the content of carbon atoms (% by mass) in the carbon-based conductive material. The carbon purity is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the mass of the carbon-based conductive material (the mass of the carbon-based conductive material is 100% by mass). By setting the carbon purity within the above range, it is possible to prevent problems such as short circuits caused by the formation of dendrites due to impurities when used in secondary batteries.

The amount of metal contained in the carbon-based conductive material is preferably less than 10% by mass, more preferably less than 5% by mass, and even more preferably less than 2% by mass with respect to 100% by mass of the carbon-based conductive material. In particular, metals contained in carbon nanotubes include metals and metal oxides used as catalysts when synthesizing carbon nanotubes. Specific examples include metals such as iron, cobalt, nickel, aluminum, magnesium, silica, manganese and molybdenum, metal oxides, and composite oxides thereof.

In addition, the carbon-based conductive material may contain an iron metal element content of 50 ppm or less, more specifically, 20 ppm or less in the catalyst used in the manufacturing process. Thus, by significantly reducing the iron content as an impurity remaining in the carbon-based conductive material, it is possible to exhibit better conductivity without fear of side reactions in the electrode. The content of metal impurities remaining in the conductive material can be analyzed using high frequency inductively coupled plasma (ICP). Moreover, the carbon-based conductive material may not contain an iron metal element.

The BET specific surface area of the carbon-based conductive material is preferably 20 to 1,000 m ² /g, more preferably 30 to 500 m ² /g.

The content of the carbon-based conductive material contained in the secondary battery resin composition is 0.00% based on the mass of the secondary battery resin composition (assuming the mass of the secondary battery resin composition is 100% by mass). 1% by mass or more is preferable, and 0.5% by mass or more is more preferable. Moreover, 30 mass % or less is preferable and 25 mass % or less is more preferable. By setting the content of the conductive material contained in the resin composition for a secondary battery within the above range, the conductive material can be favorably and stably present without causing sedimentation or gelation. In addition, it is preferable that the content of the conductive material is appropriately adjusted in consideration of the specific surface area of the conductive material, the affinity to the dispersion medium, and the like so that a resin composition for a secondary battery exhibiting an appropriate viscosity is obtained.

The method of dispersing the carbon-based conductive material is not particularly limited, but disperser, homogenizer, Silverson mixer, kneader, two-roll mill, three-roll mill, ball mill, horizontal sand mill, vertical sand mill, annular bead mill, attritor, planetary mixer. , or a method using various dispersing means such as a high-pressure homogenizer.

<Inorganic acid and inorganic base>
The resin composition for secondary batteries may further contain an inorganic acid and/or an inorganic base. The inorganic acid in the present invention refers to an acid derived from an inorganic compound, and is not particularly limited. Examples include oxoacids such as nitric acid, phosphoric acid, sulfuric acid, and boric acid, and hydrogen acids such as hydrochloric acid, hydrocyanic acid, and hexafluorophosphoric acid. mentioned. Inorganic bases include, for example, alkali metal or alkaline earth metal chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates. , or borate; and ammonium hydroxide. The metal contained in the inorganic base may be a transition metal.

The amount of inorganic acid and inorganic base used is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, based on the mass of the resin composition for a secondary battery. The amount of inorganic acid and inorganic base used is preferably 20% by mass or less, more preferably 15% by mass or less, based on the mass of the resin composition for a secondary battery.

<Slurry composition for secondary battery electrode>
The secondary battery electrode slurry composition contains at least the secondary battery resin composition and an electrode active material. In other words, the secondary battery electrode slurry composition contains at least a polymer, a dispersion medium, and an electrode active material, and further contains optional components such as a conductive material, a base, an acid, and a binder. good too. In this specification, the "slurry composition for secondary battery electrode" may be referred to as "mixture slurry" or "slurry for electrode film".

An electrode active material is a material that serves as a basis for battery reactions. Electrode active materials are classified into positive electrode active materials and negative electrode active materials according to the electromotive force.

The positive electrode active material is not particularly limited, but a material capable of reversibly doping or intercalating lithium ions can be used. Examples include metal compounds such as metal oxides and metal sulfides. Specific examples include oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specifically, transition metal oxide powders such as MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ ; Composite oxide powders of lithium and transition metals; lithium iron phosphate-based materials, which are phosphate compounds having an olivine structure; transition metal sulfide powders such as TiS ₂ and FeS. The positive electrode active material is preferably a material containing at least Ni. A positive electrode active material can also be used 1 type or in combination of more than one.

As the negative electrode active material, a material capable of reversibly doping or intercalating lithium ions can be used. For example _, metal Li, alloys such _as tin _{alloys thereof ,} silicon alloys _, and _lead alloys _; ), metal oxides such as lithium titanate, lithium vanadate, lithium silicate; conductive polymers such as polyacetylene and poly-p-phenylene; artificial graphite such as highly graphitized carbon materials, natural graphite carbonaceous powder such as; carbonaceous materials such as resin baked carbon materials. A negative electrode active material can also be used 1 type or in combination of more than one.

The content of the polymer in the slurry composition for a secondary battery electrode is preferably 0.01 to 10% by mass based on the mass of the electrode active material (assuming the mass of the electrode active material is 100% by mass). , more preferably 0.05 to 5% by mass.

The content of the conductive material in the secondary battery electrode slurry composition is based on the mass of the electrode active material (the mass of the electrode active material is 100% by mass), and is preferably 0.01 to 10% by mass. , more preferably 0.02 to 5% by mass, more preferably 0.03 to 3% by mass.

When the secondary battery electrode slurry composition contains a binder, the content of the binder in the secondary battery electrode slurry composition is based on the mass of the electrode active material (the mass of the electrode active material is 100% by mass), preferably 0.1 to 30% by mass, more preferably 0.5 to 20% by mass, even more preferably 1 to 10% by mass.

The solid content in the slurry composition for a secondary battery electrode of the present invention is based on the mass of the slurry composition for a secondary battery electrode (assuming the mass of the slurry composition for a secondary battery electrode is 100% by mass), 30 to It is preferably 90% by mass, more preferably 30 to 80% by mass, even more preferably 40 to 75% by mass.

The slurry composition for secondary battery electrodes can be produced by various conventionally known methods. For example, a method of adding an electrode active material to a resin composition for a secondary battery (since the polymer also functions as a binder, a slurry composition for a secondary battery electrode can be prepared without adding a binder). method of adding a binder to a secondary battery resin composition and then adding an electrode active material; after adding an electrode active material to a secondary battery resin composition, For example, a method of adding a binder to prepare the film.

As a method for preparing the slurry composition for secondary battery electrodes, a method of adding a binder to the resin composition for secondary batteries and then further adding an electrode active material and carrying out a dispersion treatment is preferable. A dispersing device used for dispersing is not particularly limited. A slurry composition for a secondary battery electrode can be obtained by using the dispersing means mentioned in the description of the method for dispersing the carbon-based conductive material. Moreover, without adding a binder to the resin composition for a secondary battery, the electrode active material may be added and the dispersion treatment may be performed.

<Electrode film>
The electrode film includes a film formed using the slurry composition for a secondary battery electrode film, and may further include a current collector. For example, an electrode film can be obtained by coating a current collector with a slurry composition for a secondary battery electrode film and drying, and includes a current collector and a film. In this specification, the "film formed using the slurry composition for secondary battery electrode film" may be referred to as "electrode mixture layer".

The material and shape of the current collector used to form the electrode film are not particularly limited, and can be appropriately selected according to various secondary batteries. For example, the material of the current collector includes metals or alloys such as aluminum, copper, nickel, titanium, and stainless steel. As for the shape, a flat foil is generally used, but a current collector with a roughened surface, a foil-like current collector with holes, or a mesh-like current collector can also be used.

The method for applying the secondary battery electrode slurry composition onto the current collector is not particularly limited, and known methods can be used. Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method, an electrostatic coating method, and the like. Examples of the drying method include drying by standing or drying by using a blower dryer, warm air dryer, infrared heater, far infrared heater, or the like, but are not particularly limited to these.

After coating, a rolling treatment using a lithographic press, calendar rolls, or the like may be performed. The thickness of the formed film is, for example, 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

<Non-aqueous electrolyte secondary battery>
A non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and at least one selected from the group consisting of the positive electrode and the negative electrode includes the electrode film.

As the positive electrode, for example, an electrode film prepared by coating a secondary battery electrode slurry composition containing a positive electrode active material on a current collector and drying it can be used.

As the negative electrode, for example, an electrode film prepared by coating a secondary battery electrode slurry composition containing a negative electrode active material on a current collector and drying the composition can be used.

Various conventionally known electrolytes in which ions can move can be used as the electrolyte. For example, _{LiBF4 , LiClO4} , LiPF6 _{, LiAsF6} , _{LiSbF6 , LiCF3SO3} , _Li ( _{CF3SO2 ) 2N} , _{LiC4F9SO3 ,} Li( _CF3SO2 ) _3C , LiI , LiBr, LiCl, LiAlCl, LiHF ₂ , LiSCN, or LiBPh ₄ (where Ph is a phenyl group) containing lithium salts. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolytic solution.

Examples of non-aqueous solvents include, but are not limited to, carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate; γ-butyrolactone, γ-valerolactone, and γ - lactones such as octanoic lactone; tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1, glymes such as 2-dibutoxyethane; esters such as methylformate, methylacetate and methylpropionate; sulfoxides such as dimethylsulfoxide and sulfolane; and nitriles such as acetonitrile. Each of these solvents may be used alone, or two or more of them may be used in combination.

The non-aqueous electrolyte secondary battery preferably contains a separator. Examples of the separator include polyethylene nonwoven fabric, polypropylene nonwoven fabric, polyamide nonwoven fabric, and nonwoven fabric obtained by subjecting these to hydrophilic treatment, but the separator is not particularly limited to these.

The structure of the non-aqueous electrolyte secondary battery of the present embodiment is not particularly limited, but usually includes a positive electrode, a negative electrode, and a separator provided as necessary, and can be of paper type, cylindrical type, button type, laminated type, etc. It can have various shapes depending on the purpose of use.

EXAMPLES The present invention will be described more specifically with reference to examples below. The present invention is not limited to the following examples as long as the gist thereof is not exceeded. In addition, unless otherwise indicated, "part" represents "mass part" and "%" represents "mass%."

<Conductive material>
Carbon black: Acetylene black HS-100 (manufactured by Denka) Specific surface area of 39 m ² /g determined by S-BET formula from nitrogen adsorption amount, abbreviated as “CB” hereinafter.
Carbon nanotube: multi-wall carbon nanotube 100T (manufactured by Kumho Petrochemical), fiber diameter 10 to 15 μm, hereinafter abbreviated as “CNT”.

<Polymer>
· Polyvinylpyrrolidone: K30 (manufactured by Nippon Shokubai Co., Ltd.). Hereinafter, it is abbreviated as PVP.
- Hydrogenated nitrile rubber: Zpole (R) 2000L (manufactured by Nippon Zeon Co., Ltd.). Hereinafter, it is abbreviated as HNBR.
Carboxymethyl cellulose: Sunrose (R) 0F01MC (manufactured by Nippon Paper Industries Co., Ltd.). Hereinafter, it is abbreviated as CMC.

<Inorganic acid and inorganic base>
- Sodium hydroxide, granular (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). Hereinafter, it is abbreviated as NaOH.
- Hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). Hereinafter, it is abbreviated as HCl.

<Binder>
· Polyvinylidene fluoride: KF Polymer W7300 (manufactured by Kureha Co., Ltd.), weight average molecular weight of about 1,000,000. Hereinafter, it is abbreviated as PVDF.
・ Styrene-butadiene rubber (hereinafter abbreviated as SBR) emulsion solution: TRD2001 (manufactured by JSR Corporation), solid content 48%

<Others>
・Copper powder: Fujifilm Wako Pure Chemical Co., Ltd., D50 75 μm, purity 99.9%
・Copper oxide: Kishida Chemical Co., Ltd., D50 150 μm (100 mesh)

<Electrode active material>
- LiNi1 _/ 3Mn1 _{/ 3Co1/ 3O2} : positive electrode active material, lithium nickel manganese cobaltate. It has an average primary particle diameter of 5.5 μm as determined by observation with an electron microscope, and a specific surface area of 0.62 m ² /g as determined by the S-BET formula from the nitrogen adsorption amount, hereinafter abbreviated as “NCM”.
・Artificial graphite: negative electrode active material, CGB-20 (manufactured by Nippon Graphite Industry Co., Ltd.), average particle size 12 μm, hereinafter abbreviated as “graphite”.

<Method for measuring metal ion/atom content in raw materials>
The conductive materials, polymers, and binders used in the examples were pretreated by an acid decomposition method in accordance with Japanese Industrial Standards JIS K 0116; I made a measurement. It is conceivable that the use of these materials as raw materials may contaminate the composition with foreign metals.
・CB: iron 0 ppm (below detection limit), copper 0 ppm (below detection limit)
・CNT: iron 9976ppm, copper 1.6ppm
・PVP: iron 13 ppm, copper 0 ppm (below detection limit)
・CMC: iron 0.9 ppm, copper 0 ppm (below detection limit)
・HNBR: iron 28ppm, copper 0ppm (below detection limit)
・PVDF: iron 32 ppm, copper 0.9 ppm

An embodiment of the production line for the resin composition for secondary batteries of the present invention will be described below with reference to the drawings.
FIG. 1 shows an example of a production line in which oxygen (air) gas is introduced from the upper part of a tank, and the secondary battery resin composition and oxygen (air) gas in the tank are gas-liquid mixed by disper stirring. ing.
In FIG. 2, a static mixer is attached to the tank via piping, and oxygen (air) gas is directly introduced into the composition while circulating the secondary battery resin composition in the tank with a pump. An example of a production line for gas-liquid mixing is shown.
FIG. 3 shows the case where a bubbler is installed at the bottom of the tank, and gas-liquid mixing is performed by introducing oxygen (air) gas directly into the resin composition for secondary batteries in the tank and disper stirring. shows an example of a production line of
In addition, the sizes of constituent members such as tanks and pipes constituting each production line are adjusted according to the production scale.

<Production line (A) of resin composition for secondary battery>
The manufacturing line (A) of the resin composition for secondary batteries in FIG. 1 will be described in detail.
The production line (A) includes a tank for dissolving/storing/preparing the secondary battery resin composition shown in 1A, and a disper (stirring blade) 2A for stirring the secondary battery resin composition in the tank. It has A pipe 31A for introducing oxygen (air) gas is connected from the upper part of the tank, and by introducing oxygen (air) gas while stirring the resin composition for secondary batteries in the tank, gas-liquid Mixing becomes possible.

<Production line (B) of resin composition for secondary battery>
The manufacturing line (B) of the resin composition for secondary batteries in FIG. 2 will be described in detail.
The production line (B) includes a tank for dissolving/storing/preparing the secondary battery resin composition shown in 1B, and a disper (stirring blade) 2B for stirring the secondary battery resin composition in the tank. , and is connected to a pipe 31B via a valve 5 from the bottom of the tank. The pipe 31B is connected to the circulation pump 6, the pump outlet pipe 32B is connected to the static mixer 8 via the oxygen (air) gas inlet 7, and the pipe 33B at the end of the static mixer 8 is connected to the tank. It is connected to the upper part of 1B. As a result, oxygen (air) gas is introduced directly into the resin composition for secondary batteries, and the resin composition is circulated and stirred to allow gas-liquid mixing.

<Production line (C) of resin composition for secondary battery>
The manufacturing line (C) of the resin composition for secondary batteries in FIG. 3 will be described in detail.
The production line (C) includes a tank for dissolving/storing/preparing the secondary battery resin composition shown in 1C, and a disper (stirring blade) 2C for stirring the secondary battery resin composition in the tank. Also, a bubbler is installed at the bottom of the tank. As a result, gas and liquid can be mixed by circulating and stirring while oxygen (air) gas is introduced directly into the secondary battery resin composition by bubbling.

<Evaluation of Oxidation Effect of Metal Impurities in Resin Composition for Secondary Battery>
Regarding the oxidation effect by introducing oxygen (air) gas into the resin composition for secondary batteries and mixing gas and liquid,
(1) Magnetic deposit amount of secondary battery resin composition (2) Linear sweep voltammetry measurement of secondary battery resin composition to which copper powder was intentionally added (hereinafter, LSV measurement)
(3) Evaluation was made by LSV measurement using the filtration residue of the resin composition for secondary batteries.
In the evaluation of (1), the magnetic substance amount in the composition can be confirmed by filtering the secondary battery resin composition with a magnetic filter, collecting the magnetic substance, and weighing. If the magnetic metal (such as iron) in the composition is oxidized, it loses its magnetism and the amount of magnetized substances is reduced. On the other hand, the effect of oxidation cannot be confirmed for metals such as copper that originally do not have magnetism. In the evaluation of (2), when copper, which is a representative example of a metal that does not have magnetism as described above, was intentionally added to the resin composition for a secondary battery, the effect of oxidation on the added copper was evaluated. confirm. In the evaluation of (3), the effect of oxidation on the conductive material, polymer, and non-magnetic metal derived from the binder in the resin composition for secondary batteries is confirmed.

LSV measurement is a method of sweeping the potential of the electrode in a specific range, measuring the reaction current flowing accordingly and analyzing each electrochemical information. Reaction rates can be confirmed quantitatively. For example, when copper is present in the positive electrode and lithium foil is used as the negative electrode, the oxidation-reduction potential of copper is approximately 3.4 V in terms of the standard electrode potential. This means that at a voltage of about 3.4 V or higher, electron transfer occurs due to the elution reaction of copper. The rise of the reaction current in the LSV measurement represents the reaction initiation potential, and the amount of reaction current and the slope represent the easiness of copper elution. When the surface of the copper particles is chemically changed to copper oxide by oxidation, the elution of copper ions is suppressed, so the reaction initiation potential in LSV measurement shifts to the high voltage side.

<(1) Evaluation of magnetic substance amount in resin composition for secondary battery>
[Example 1]
The production line (A) was used to produce a resin composition for a secondary battery. 540 kg of NMP was put into the tank, and the temperature of the NMP in the tank was heated to 60° C. while stirring the disper. After that, 60 kg of PVP was added as a polymer, and disper stirring was continued until it was completely dissolved to obtain a PVP-NMP solution with a concentration of 10%.
Subsequently, dry air (dry air) containing 20% oxygen is introduced from the pipe at the top of the tank at a flow rate of 1500 NL / h (300 NL / h as oxygen content), and the 10% PVP-NMP solution in the tank is discharged. A resin composition for a secondary battery (composition 1) was obtained by performing gas-liquid mixing by disper stirring for an additional 8 hours.
The obtained resin composition for secondary batteries was filtered through a magnetic filter (manufactured by Tok Engineering Co., Ltd.) under the conditions of room temperature and magnetic flux density of 12,000 gauss. After filtering, the magnetic filter was found to have adhered a small amount of granular metal pieces having magnetism. These metal pieces were collected and weighed to find 3.4 mg.

[Examples 2 to 7]
A resin composition for a secondary battery was produced in the same manner as in Example 1, except that the polymer amount, concentration, solvent amount, dry air flow rate, and tank internal temperature were changed as shown in Table 1. Thereafter, magnetic filter filtration was carried out in the same manner as in Example 1, and the magnetic deposit was collected and weighed. The results are listed in Table 1.

[Example 8]
The production line (B) was used to produce a resin composition for a secondary battery. 540 kg of NMP was put into the tank, and the temperature of the NMP in the tank was heated to 60° C. while stirring the disper. After that, 60 kg of PVP was added as a polymer, and disper stirring was continued until it was completely dissolved to obtain a PVP-NMP solution with a concentration of 10%.
Subsequently, by opening the valve at the bottom of the tank and driving the circulation pump, the solution is circulated in the order of the tank, the pump, the static mixer, and the tank (return). % dry air (dry air) was introduced at a flow rate of 1500 NL/h (300 NL/h as oxygen content). The introduced dry air flows together with the solution, and after the gas-liquid mixture is performed in the static mixer, the gas-liquid mixture is further performed in the tank by disper stirring.
Said circulation stirring was implemented for 8 hours, and the resin composition for secondary batteries (composition 8) was obtained. The obtained resin composition for a secondary battery was filtered through a magnetic filter in the same manner as in Example 1, and the magnetic deposit was recovered and weighed. rice field. The results are listed in Table 1.

[Example 9]
A resin composition for a secondary battery was produced by the production line (C). 540 kg of NMP was put into the tank, and the temperature of the NMP in the tank was heated to 60° C. while stirring the disper. After that, 60 kg of PVP was added as a polymer, and disper stirring was continued until it was completely dissolved to obtain a PVP-NMP solution with a concentration of 10%. Subsequently, dry air containing 20% oxygen (dry air) was introduced from the bubbler at the bottom of the tank at a flow rate of 1500 NL / h (300 NL / h as oxygen content), and disper stirring was further added for 8 hours. By performing gas-liquid mixing, a secondary battery resin composition (composition 9) was obtained.
The obtained resin composition for a secondary battery was filtered through a magnetic filter in the same manner as in Example 1, and the magnetic deposit was collected and weighed. rice field. The results are listed in Table 1.

[Example 10]
A secondary battery resin composition (composition 10) was produced in the same manner as in Example 9, except that HNBR was used as the polymer species. Thereafter, magnetic filter filtration was carried out in the same manner as in Example 1, and the magnetic deposit was collected and weighed, and the amount was 3.1 mg. The results are listed in Table 1.

[Example 11]
A secondary battery resin composition (composition 10) was prepared in the same manner as in Example 9 except that CMC was used as the polymer species, water was used as the solvent, the polymer concentration was changed to 5%, and the temperature in the tank was changed to 40°C. manufactured. Thereafter, magnetic filter filtration was carried out in the same manner as in Example 1, and the magnetic deposit was collected and weighed, and the amount was 0.7 mg. The results are listed in Table 1.

[Comparative Examples 1 to 3]
A resin composition for a secondary battery was produced as described in Table 1, except that oxygen gas was not introduced. Magnetic filter filtration was then performed, and magnetic deposits were collected and weighed. The results are listed in Table 1.

[Example 12]
A resin composition for a secondary battery was produced by the production line (C). 534 kg of NMP was put into the tank, and the temperature of the NMP in the tank was heated to 60° C. while stirring the disper. Thereafter, 60 kg of HNBR was added as a polymer, and disper stirring was continued until the polymer was completely dissolved to obtain a HNBR-NMP solution with a concentration of 10%. Subsequently, while stirring the disper, 6 kg of NaOH as an inorganic base was slowly added, and then dry air containing 20% oxygen (dry air) was supplied from the bubbler at the bottom of the tank at a flow rate of 1500 NL / h (300 NL / as oxygen content). While introducing in h), disper stirring was performed for an additional 8 hours to perform gas-liquid mixing to obtain a secondary battery resin composition (composition 12) containing an inorganic base.
The obtained resin composition for a secondary battery was filtered through a magnetic filter in the same manner as in Example 1, and the magnetic deposit was collected and weighed. rice field. The results are listed in Table 1.

[Example 13]
A resin composition for a secondary battery was produced by the production line (C). 558 kg of water was put into the tank, and the water in the tank was heated to 40° C. while stirring the disper. After that, 30 kg of CMC was added as a polymer, and disper stirring was continued until it was completely dissolved to obtain an aqueous CMC solution with a concentration of 5%. Subsequently, while stirring the disper, after slowly adding 12 kg of HCl as an inorganic acid, dry air containing 20% oxygen (dry air) was supplied from the bubbler at the bottom of the tank at a flow rate of 1500 NL/h (300 NL/h as the oxygen content). While introducing in h), disper stirring was performed for an additional 8 hours to perform gas-liquid mixing, thereby obtaining a secondary battery resin composition (composition 13) containing an inorganic acid.
The obtained resin composition for a secondary battery was filtered through a magnetic filter in the same manner as in Example 1, and the magnetic deposit was collected and weighed. rice field. The results are listed in Table 1.

[Comparative Examples 4 and 5]
A secondary battery resin composition containing an inorganic acid or an inorganic base was produced as described in Table 1, except that oxygen gas was not introduced. Magnetic filter filtration was then performed, and magnetic deposits were collected and weighed. The results are listed in Table 1.

[Example 14]
According to the composition shown in Table 2, NMP was put into a stainless steel tank, and PVP was added and dissolved with disper stirring to adjust to a predetermined concentration. Subsequently, CNTs were added while dispersing and stirring, and batch-type dispersion treatment was performed using a high-shear mixer (manufactured by SILVERSON) equipped with a square-hole high-shear screen until the particle size with a grind gauge reached 250 μm or less. Next, the liquid to be dispersed was supplied from the stainless steel tank to a high-pressure homogenizer (Starburst 10, manufactured by Sugino Machine) through a pipe for additional dispersion treatment. In the additional dispersion treatment, a single nozzle chamber was used, a nozzle diameter of 0.25 mm, a pressure of 100 MPa, and 45 pass dispersion treatments were performed to obtain 60 kg of a secondary battery resin composition (composition 12) containing a conductive material. rice field.
The resulting secondary battery resin composition (composition 14) was subjected to dry air flow rate of 1500 NL / h (300 NL / h as oxygen content) for 8 hours at a temperature of 40 ° C. in the production line (B). The liquids were mixed. Finally, magnetic filter filtration was carried out, and the magnetic deposit was recovered and weighed, resulting in 15.3 mg.

[Example 15]
A resin composition for a secondary battery was produced according to the composition shown in Table 2. Ion-exchanged water was put into a stainless steel tank, and CMC was added and dissolved with disper stirring to adjust the concentration to a predetermined value. Subsequently, CB was added while dispersing and stirring, and batch-type dispersion treatment was performed using a high-shear mixer (manufactured by SILVERSON) equipped with a square-hole high-shear screen until the particle size with a grind gauge reached 250 μm or less. Next, the liquid to be dispersed was supplied from the stainless steel tank through a pipe to a bead mill (Dyno Mill MULTI LAB, manufactured by Shinmaru Enterprises Co., Ltd.) filled with zirconia beads having a diameter of 1.00 mm for additional dispersion treatment. The additional dispersion treatment is continued until the particle size of the liquid to be dispersed with a grind gauge is 20 μm or less, and the viscosity is lowered and the dispersion is completed after confirming that it has sufficient fluidity. 60 kg of a resin composition (composition 15) was obtained.
rice field.
The secondary battery resin composition (composition 15) containing the obtained conductive material was dried at a dry air flow rate of 1500 NL/h (300 NL/h as an oxygen content) for 8 hours at a temperature of 40 in the production line (B). Vapor-liquid mixing was performed at °C. Finally, magnetic filter filtration was carried out, and the magnetic deposit was recovered and its weight was measured, which was 0.9 mg.

[Example 16]
A resin composition for a secondary battery was produced according to the composition shown in Table 2. NMP was put into a stainless steel tank, and PVP was added and dissolved with disper stirring to adjust to a predetermined concentration. Subsequently, powders of CB and PVDF (mass ratio of PVP:PVDF is 1:5) are added at the same time while being disper-stirred, and ground with a high-shear mixer (manufactured by SILVERSON) equipped with a square-hole high-shear screen. A batch-type dispersion treatment was performed until the particle size measured by a gauge became 20 μm or less to obtain a secondary battery resin composition (composition 16).
60 kg of the resulting resin composition for secondary batteries (composition 16) was subjected to dry air flow rate of 1500 NL/h (300 NL/h as oxygen content) for 8 hours at a temperature of 45°C. - Liquid mixing was carried out. Finally, magnetic filter filtration was carried out, and the magnetic deposit was recovered and its weight was measured, which was 10.4 mg.

[Comparative Example 6]
A resin composition for a secondary battery was produced in the same manner as in Example 14, except that dry air was not introduced. After that, magnetic filter filtration was carried out, and the magnetic deposit was collected and weighed, and the result was 172 mg. The results are listed in Table 2.

[Comparative Example 7]
A resin composition for a secondary battery was produced in the same manner as in Example 15, except that dry air was not introduced. After that, magnetic filter filtration was carried out, and the magnetic deposit was collected and weighed, and the result was 12.8 mg. The results are listed in Table 2.

[Comparative Example 8]
A resin composition for a secondary battery was produced in the same manner as in Example 16, except that dry air was not introduced. After that, magnetic filter filtration was carried out, and the magnetic deposit was collected and weighed, and the result was 90.2 mg. The results are listed in Table 2.

In the evaluation results of the magnetic substance amount in Table 1, focusing on the difference depending on the presence or absence of oxygen (air) gas introduction in the same system (for example, Example 1 and Comparative Example 1, Example 10 and Comparative Example 2, etc.), oxygen It can be seen that the introduction of (air) gas significantly reduces the amount of magnetized substances. It is presumed that this is because the introduction of oxygen (air) gas oxidized the magnetic metal components in the system and stopped reacting with the magnetic filter. Focusing on the effect of oxidation, the results of Examples 1 and 2 show that the temperature inside the tank is higher, and the results of Examples 1 and 5 to 7 show that the higher the amount of oxygen (air) gas introduced, the better the oxidation. It can be seen that the effect is high. Moreover, from the results of Example 1 and Examples 8 and 9, it can be seen that a high effect can be obtained by directly introducing oxygen (air) gas into the resin composition for secondary batteries. These are highly effective regardless of the type of solvent, type of polymer, and concentration. Focusing on the effect of the inorganic acid and the inorganic base, it can be confirmed from the results of Examples 10 and 12 and the results of Examples 11 and 13 that the magnetic substance amount is reduced. In addition, based on the results of Comparative Examples 4 and 5, it can be seen that simply treating with an inorganic acid and an inorganic base without introducing oxygen (air) gas has little effect.
From Table 2, it can be seen that a similar oxidation effect is obtained in the secondary battery resin composition containing a conductive material and a binder.

<(2) LSV measurement of secondary battery resin composition intentionally added with copper powder>
[Example 17]
The production line (A) was used to produce a resin composition for a secondary battery. NMP was put into the tank, and the temperature of the NMP in the tank was heated to 60° C. while stirring the disper. After that, PVP was added as a polymer, and disper stirring was continued until it was completely dissolved to obtain a PVP-NMP solution with a concentration of 10%. Subsequently, after adding copper powder to 500 ppm, dry air containing 20% oxygen (dry air) was introduced from the pipe at the top of the tank at a flow rate of 1500 NL / h (300 NL / h as oxygen content). At the same time, the 10% PVP-NMP solution in the tank was additionally disper-stirred for 8 hours to perform gas-liquid mixing, thereby obtaining a secondary battery resin composition (composition 17) containing copper powder.

(LSV measurement of the resin composition for secondary batteries obtained in Example 17)
First, 12 g of a secondary battery resin composition (composition 17) containing 500 ppm of copper powder was weighed into a 300 ml polypropylene cup, and then 164 g of NMP was added. 19.2 g of CB as a conductive material and 4.8 g of PVDF were simultaneously added while stirring with a high shear mixer (manufactured by SILVERSON) equipped with a square hole high shear screen, and the batch process was performed until the particle size with a grind gauge became 20 μm or less. Distributed processing was performed. The prepared conductive paste was applied to an aluminum foil having a thickness of 20 μm using a doctor blade, dried by heating at 120° C. under reduced pressure, and punched into a working electrode having a radius of 9 mm. Using a metallic lithium foil (thickness 0.15 mm) as a counter electrode, a separator made of a porous polypropylene film (thickness 20 μm, porosity 50% by volume) is inserted and laminated between the working electrode and the counter electrode, and a non-aqueous electrolyte ( A non-aqueous electrolyte in which _LiPF6 was dissolved at a concentration of 1 M in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1:1) was filled with a two-electrode closed metal cell (HS flat cell manufactured by Hosen Co., Ltd.). assembled. Assembly of the cell was performed in a glove box that was replaced with argon gas.

LSV measurement was performed under the following conditions.
・Sweep start potential; 3.0 V (vs Li/Li ⁺ )
- Sweep end potential; 4.3 V (vs Li/Li ⁺ )
- Sweep speed; 10mV/min.
・Measurement temperature: 25°C
The oxidation-reduction initiation potential of copper, which is an index of the easiness of copper elution, was defined as the potential at the time when the current density reached 20 μA/cm ² from the start of the potential sweep.
When the test battery constructed under the above conditions was evaluated, no current derived from oxidation-reduction reaction of copper was measured. This is probably because the added copper was oxidized by the oxygen (air) gas introduction. Note that copper contained in CB is not detected in this measurement.

[Comparative Example 9]
A secondary battery resin composition and then a test battery were constructed in the same manner as in Example 17, except that dry air was not introduced, and evaluation was performed by LSV measurement. It was about 3.4V, and a short circuit occurred during the potential sweep. This is probably because the copper particles were eluted by potential sweeping on the positive electrode side and then reduced and formed on the negative electrode side.

[Production Example 1]
A secondary battery resin composition and then a test battery were constructed in the same manner as in Example 17, except that copper oxide was added instead of copper, and evaluation was performed by LSV measurement. No current from the reaction was measured. This result is consistent with the results of Example 17, where no current was also measured due to redox reactions of copper, and indicates that if copper is oxidized, no current is measured.

<(3) Measurement of LSV using filtration residue of resin composition for secondary battery>
[Example 18]
First, according to the composition of Example 14 shown in Table 2, NMP was put into a stainless steel tank, and PVP was added and dissolved with disper stirring to adjust to a predetermined concentration. Subsequently, CNTs were added while dispersing and stirring, and batch-type dispersion treatment was performed using a high-shear mixer (manufactured by SILVERSON) equipped with a square-hole high-shear screen until the particle size with a grind gauge reached 250 μm or less. Next, the liquid to be dispersed was supplied from the stainless steel tank to a high-pressure homogenizer (Starburst 10, manufactured by Sugino Machine) through a pipe for additional dispersion treatment. For the additional dispersion treatment, a single nozzle chamber was used, and a nozzle diameter of 0.25 mm and a pressure of 100 MPa were applied for 45 passes to obtain a secondary battery resin composition (composition 18) containing a conductive material. .
60 kg of the obtained resin composition for secondary batteries (composition 18) was subjected to dry air flow rate of 1500 NL/h (300 NL/h as oxygen content) for 8 hours at a temperature of 40°C. - Liquid mixed. Subsequently, magnetic filter filtration was performed to remove magnetic foreign matter. Subsequently, after diluting 10-fold with NMP, the residue solid matter containing non-magnetic metal foreign matter such as copper was recovered by filtering through a 25 μm mesh. The resulting residue was washed with NMP and dried at 40° C. under reduced pressure to obtain 30 mg of residual solid matter containing non-magnetic metal foreign matters such as copper. The obtained non-magnetic metallic foreign matter is presumed to be non-magnetic metallic foreign matter mixed mainly with CNTs and PVP in the secondary battery resin composition (composition 18), the production line, and the like.

(LSV measurement using the filtration residue of the secondary battery resin composition obtained in Example 18)
CB and PVDF were used as conductive materials, and weighed so that the ratio of CB:PVDF was 8:2. was dispersed in the solvent NMP to prepare a conductive paste. The conductive paste thus prepared was applied to an aluminum foil having a thickness of 20 μm using a doctor blade, dried by heating at 120° C. under reduced pressure, and punched out to a radius of 9 mm to obtain a working electrode. Using a metallic lithium foil (thickness 0.15 mm) as a counter electrode, a separator made of a porous polypropylene film (thickness 20 μm, porosity 50% by volume) is inserted and laminated between the working electrode and the counter electrode, and a non-aqueous electrolyte ( A non-aqueous electrolyte in which _LiPF6 was dissolved at a concentration of 1 M in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1:1) was filled with a two-electrode closed metal cell (HS flat cell manufactured by Hosen Co., Ltd.). assembled. Assembly of the cell was performed in a glove box that was replaced with argon gas. When the constructed test battery was evaluated by LSV measurement in the same manner as in Example 17, no current derived from oxidation-reduction reaction of copper was measured. This is presumably because the added residual solid matter had already been oxidized by introducing oxygen (air) gas.

[Comparative Example 10]
A secondary battery resin composition and then a test battery were constructed in the same manner as in Example 18, except that dry air was not introduced, and evaluation was performed by LSV measurement. It was about 3.4V, and a short circuit occurred during the potential sweep. This is presumably because the copper particles contained in the residual solid matter were eluted by potential sweeping on the positive electrode side and then reduced and generated on the negative electrode side.

<Example 19: Preparation of positive electrode mixture slurry and positive electrode film>
Examples of producing an electrode mixture slurry using the resin composition for a secondary battery produced according to the present invention and an electrode coated with the slurry are shown below.
In a plastic container with a capacity of 150 mL, 1.08 g of CB as a conductive material and 0.54 g of the secondary battery resin composition (composition 1) produced in Example 1 (PVP solid content: 0.054 g; CB ratio of 5%) and 9 g of 8% by mass PVDF solution (including 0.72 g of PVDF as a solid content) are added, and then a rotation and revolution mixer (Awatori Mixer manufactured by Thinky Co., Ltd., ARE-310) was used to stir at 2,000 rpm for 30 seconds. Next, 34.2 g of NMC was added as an electrode active material and stirred at 2,000 rpm for 20 minutes using a rotation and revolution mixer. After that, 5.18 g of NMP was added, and the mixture was stirred at 2,000 rpm for 30 seconds using a rotation and revolution mixer to obtain a positive electrode mixture slurry having a solid content of about 72%.

The positive electrode mixture slurry was applied onto an aluminum foil having a thickness of 20 μm as a current collector using an applicator and dried in an electric oven at 120° C.±5° C. for 25 minutes to prepare an electrode. At this time, the applicator gap was successively adjusted so that the basis weight per unit area was 20 mg/cm ² . The obtained electrode was further subjected to a rolling process by a roll press (manufactured by Thank Metal Co., Ltd., 3t hydraulic roll press) to prepare a positive electrode film having a positive electrode mixture layer density of 3.1 g/cm ³ .

<Example 20: Production of negative electrode mixture slurry and negative electrode film>
In a plastic container with a capacity of 150 mL, 0.6 g of the secondary battery resin composition prepared in Example 15 (CB; containing 0.12 g of HS-100 as a conductive material), 0.24 g of CMC, and 25.14 g of water. and then stirred at 2,000 rpm for 30 seconds using a rotation and revolution mixer. Furthermore, 23.28 g of artificial graphite was added as a negative electrode active material, and the mixture was stirred at 2,000 rpm for 150 seconds using a rotation and revolution mixer. Subsequently, 0.75 g of SBR emulsion solution (containing 0.36 g of SBR as a solid content) was added and stirred at 2,000 rpm for 30 seconds using a rotation and revolution mixer to obtain a negative electrode with a solid content of about 48%. A mixture slurry was obtained. The solid content ratio of negative electrode active material:conductive material:CMC:SBR in the negative electrode mixture slurry was 97:0.5:1:1.5.

The negative electrode mixture slurry was applied onto a copper foil having a thickness of 20 μm as a current collector using an applicator, and then dried in an electric oven at 80° C.±5° C. for 25 minutes to prepare an electrode. At this time, the applicator gap was successively adjusted so that the basis weight per unit area was 10 mg/cm ² . Further, rolling treatment was performed by a roll press (manufactured by Thank Metal Co., Ltd., 3t hydraulic roll press) to produce a negative electrode having a negative electrode mixture layer with a density of 1.6 g/cm ³ .

<Example 21: Fabrication of non-aqueous electrolyte secondary battery>
The positive electrode film of Example 19 and the negative electrode film of Example 20 were punched out to 50 mm × 45 mm and 45 mm × 40 mm, respectively, and the separator (porous polypropylene film) inserted between them was inserted into an aluminum laminate bag and placed in an electric oven. and dried at 70° C. for 1 hour. Subsequently, 2 mL of the electrolytic solution was injected into the glove box filled with argon gas, and the aluminum laminate bag was sealed to produce a battery. The electrolytic solution is prepared by mixing ethylene carbonate, dimethyl carbonate and diethyl carbonate at a ratio of 1:1:1 (volume ratio), and further adding VC (vinylene carbonate) as an additive to 100 parts of the electrolytic solution. It is a non-aqueous electrolytic solution in which LiPF ₆ is dissolved at a concentration of 1M after adding 1 part of LiPF 6 .

<Evaluation of rate characteristics of non-aqueous electrolyte secondary battery>
The non-aqueous electrolyte secondary battery was placed in a constant temperature room at 25° C., and charge/discharge measurements were performed using a charge/discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). After performing constant current constant voltage charging (cutoff current 1 mA (0.02 C)) at a charging current of 10 mA (0.2 C) and a charging end voltage of 4.3 V, discharge at a discharging current of 10 mA (0.2 C). Constant current discharge was performed at a final voltage of 3V. After repeating this operation three times, constant-current and constant-voltage charging (cutoff current (1 mA (0.02 C)) was performed at a charging current of 10 mA (0.2 C) and a charge cut-off voltage of 4.3 V. The discharge capacity was obtained by performing constant current discharge at 2 C and 3 C until reaching a discharge end voltage of 3.0 V. The rate characteristic is the ratio of the 0.2 C discharge capacity and the 3 C discharge capacity, and can be expressed by the following formula 1. can.

(Formula 1)
Rate characteristics = 3C discharge capacity/3rd 0.2C discharge capacity x 100 (%)

As a result of the above, the rate characteristics of the produced battery were 80% or more, which was an excellent result.

<Method for evaluating cycle characteristics of non-aqueous electrolyte secondary battery>
The non-aqueous electrolyte secondary battery was placed in a constant temperature room at 25° C., and charge/discharge measurements were performed using a charge/discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). After performing constant current constant voltage charging (cutoff current 2.5 mA (0.05 C)) at a charging current of 25 mA (0.5 C) and a charging end voltage of 4.3 V, discharge current of 25 mA (0.5 C) , constant-current discharge was performed at a discharge final voltage of 3V. This operation was repeated 200 times. Cycle characteristics can be expressed by the following formula 2, which is the ratio of the 3rd 0.5C discharge capacity to the 200th 0.5C discharge capacity at 25°C.

(Formula 2)
Cycle characteristics = 3rd 0.5C discharge capacity/200th 0.5C discharge capacity x 100 (%)

As a result of the above, the cycle characteristics of the produced battery were 85% or more, which was an excellent result.

As described above, it was confirmed that a battery having excellent rate characteristics and cycle characteristics can be produced by using the resin composition for a secondary battery obtained by the production method of the present invention.

Although the invention has been described with reference to the embodiments, the invention is not limited by the above. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

1A, 1B, 1C: Tanks 2A, 2B, 2C: Dispers (stirring blades)
5: Valve 6: Circulation pump 7: Oxygen (air) inlet 8: Static mixer 9: Bubbler 31A, 31B, 31C, 32B, 33B: Piping 40: Gas cylinder

Claims (9)

A method for producing a resin composition for a secondary battery containing a polymer and a dispersion medium,
A method for producing a secondary battery resin composition, comprising a step of oxidizing a metal component contained in the secondary battery resin composition. 2. The method for producing a secondary battery resin composition according to claim 1, wherein the step of oxidizing the metal component is a step of bringing oxygen gas into contact with the secondary battery resin composition. 3. The method for producing a secondary battery resin composition according to claim 2, wherein the flow rate of said oxygen gas is 20 NL/h or more per 1 m ^<3> of said secondary battery resin composition. The method for producing a resin composition for secondary batteries according to any one of claims 1 to 3, further comprising a conductive material. 5. The method for producing a secondary battery resin composition according to any one of claims 1 to 4, further comprising an inorganic acid and/or an inorganic base. A method for producing a secondary battery electrode slurry composition containing the secondary battery resin composition obtained by the production method according to any one of claims 1 to 5 and an electrode active material. A method for producing an electrode film, comprising coating the slurry composition for a secondary battery electrode obtained by the production method according to claim 6 . A method for producing a battery electrode, comprising forming an electrode film obtained by the production method according to claim 7 on an electrode substrate. A method for producing a lithium ion secondary battery using the battery electrode obtained by the production method according to claim 8 .

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