WO2012066911A1 - Electrochemical device electrode binder, method for producing same, and method for preserving electrochemical device electrode binder - Google Patents

Abstract

Provided is an electrochemical device electrode binder that can be used as a material for forming an electrode for configuring an electrochemical device that has a high safety level and a very low occurrence rate of faults such as separator damage. The electrochemical device electrode binder is obtained by polymerizing a polymerizable monomer, and when measured using a particle counter, the number of particles in 1mL having a particle diameter greater than or equal to 20μm is zero.

Description

Binder for electrochemical device electrode, method for producing the same, and storage method for binder for electrochemical device electrode

The present invention relates to a binder for an electrochemical device electrode, a method for producing the binder, a method for storing the binder for an electrochemical device electrode, a slurry for an electrochemical device electrode, and an electrochemical device electrode. In more detail, the binder for an electrochemical device electrode, which is a material for obtaining an electrochemical device electrode that has a very low occurrence rate and a high safety such that the separator separating the positive electrode and the negative electrode is damaged, its manufacturing method, electrochemical The present invention relates to a method for storing a binder for device electrodes, a slurry for electrochemical device electrodes, and an electrochemical device electrode.

In recent years, advances in miniaturization and weight reduction of electronic devices are remarkable. Accordingly, there is a growing demand for miniaturization and high energy density in electrochemical devices such as secondary batteries used as power sources for driving the electronic devices. And in order to satisfy such a request | requirement, a nickel-hydrogen secondary battery, a lithium ion secondary battery, etc. are used instead of a nickel cadmium secondary battery as an electrochemical device.

As a method for producing an electrode constituting these electrochemical devices, an electrode active material such as a hydrogen storage alloy or graphite (hereinafter sometimes simply referred to as “active material”), and a thickener such as carboxymethylcellulose, The electrode layer is formed by applying a paste or slurry in which a binder made of latex containing polymer particles is dispersed in water to the surface of the current collector and drying it, and pressing the resulting coating film. A forming method is known.

Here, in addition to the function of binding the active material, the binder has a function of improving the adhesion between the electrode layer containing the active material and the current collector. Examples of such a binder include conjugated dienes. And a latex obtained by emulsion polymerization of a monomer containing an aromatic vinyl compound, a (meth) acrylate compound and an ethylenically unsaturated carboxylic acid is known (see Patent Document 1 and Patent Document 2).

Japanese Patent Laid-Open No. 10-241692 Japanese Patent Laid-Open No. 11-25989

The binder contains polymer particles that are difficult to swell in the electrolyte solution, have good dispersibility and storage stability when mixed with an active material, and are formed with an electrode layer and a current collector. Performance such as high adhesiveness is required. In particular, a binder used for a secondary battery used as a vehicle drive source of a hybrid vehicle or an electric vehicle is required to have higher productivity and safety.

However, since the compositions (binders) described in Patent Documents 1 and 2 are in a state where organic particles are dispersed in a dispersion medium, aggregates (foreign substances) can be easily formed by processing after production and changes in storage environment. appear. Aggregates thus generated cause a short circuit of the electrode. Specifically, an electrochemical device manufactured using a composition (binder) in which aggregates are generated may cause a problem such as ignition due to an extremely rare defect in the electrode. Therefore, the development of a new binder with reduced foreign matter that can produce an electrode with the least possible occurrence of the above problems has been desired. Furthermore, there has been a demand for the development of a storage method that hardly generates foreign matter.

The present invention has been made to solve the above-described problems of the prior art, and has a high safety electrochemical device, specifically, the occurrence rate of defects such as breakage of the separator is extremely small. Provided are a binder for an electrochemical device electrode that can be used as a material for forming an electrode of an electrochemical device that hardly causes a problem such as ignition, a method for producing the binder, a slurry for an electrochemical device electrode, and an electrochemical device electrode. For the purpose. Furthermore, it is an object of the present invention to provide a storage method that does not generate foreign matters when storing the binder for electrochemical device electrodes, and to improve the yield of the manufactured electrodes.

As a result of intensive investigations to achieve the above-mentioned problems, the present inventors have found that the binder is removed from the particles having a particle size larger than the thickness of the separator, resulting in the occurrence of defects such as damage to the separator due to the particles. Focusing on the fact that the rate is extremely small, the present inventors have found that the above problem can be achieved by a binder from which particles having a particle size larger than the thickness of the separator are removed, and have completed the present invention.

The present invention provides the following binder for an electrochemical device electrode, a method for producing the binder, a method for storing the binder for an electrochemical device electrode, a slurry for an electrochemical device electrode, and an electrochemical device electrode.

[1] A binder for an electrochemical device electrode obtained by polymerizing a polymerizable monomer, wherein the number of particles having a particle diameter of 20 μm or more per mL is 0 when measured with a particle counter.

[2] The binder for an electrochemical device electrode according to [1], wherein the number of particles having a particle diameter of 15 μm or more and less than 20 μm per mL is 0 to 35000 as measured with a particle counter.

[3] The binder for an electrochemical device electrode according to the above [1] or [2], wherein the number of particles having a particle diameter of more than 10 μm and less than 15 μm per mL is 0 to 500,000 as measured by a particle counter .

[4] An electrochemical device comprising the binder for an electrochemical device electrode according to any one of the above [1] to [3] (hereinafter sometimes simply referred to as “binder for electrode”) and an electrode active material. Device electrode slurry.

[5] A plate-like current collector and the electrochemical device electrode slurry according to [4], which are disposed on one surface side of the current collector, are applied to the one surface of the current collector. And an electrode layer obtained by the method.

[6] An electrochemical device electrode having a filtration step of polymerizing a polymerizable monomer to obtain a reaction solution containing a polymer and then filtering the obtained reaction solution with a depth-type or pleat-type filter Method for manufacturing binder.

[7] The electrochemical device electrode binder according to [6], wherein a filtrate having 0 particles having a particle diameter of 20 μm or more per mL when measured with a particle counter is obtained by the filtration step. Production method.

[8] Electrochemical device electrode binder containing polymer particles and water stored at a temperature of 2 ° C. or higher and 30 ° C. or lower and filled with the electrochemical device electrode binder for storage The method for preserving a binder for an electrochemical device electrode, wherein a ratio (%) of the volume of the void portion excluding the volume occupied by the binder for an electrochemical device electrode to the internal volume of the container is 1 to 20%.

[9] The method for storing an electrochemical device electrode binder according to [8], wherein the void portion has an oxygen concentration of 1% or less.

[10] The electrochemical device electrode binder according to [8] or [9], wherein the electrochemical device electrode binder is the electrochemical device electrode binder according to any one of [1] to [3]. Binder storage method.

In the binder for an electrochemical device electrode of the present invention, the number of particles having a particle diameter of 20 μm or more per mL when measured with a particle counter is 0, and therefore the separator is damaged by the particles contained in the binder (that is, The separator can be used as a material for forming an electrode constituting an electrochemical device that has a very low defect occurrence rate and high safety.

In the method for producing a binder for an electrochemical device electrode according to the present invention, a polymerizable monomer is polymerized to obtain a reaction solution containing a polymer, and then the obtained reaction solution is subjected to a depth type or pleat type filter. The electrode constituting the electrochemical device having a very low safety rate with a very low occurrence rate of defects in which the separator is broken by the particles contained in the binder (that is, the separator is penetrated by the particles). There exists an effect that the binder for electrochemical device electrodes for forming can be manufactured.

According to the method for storing the binder for electrochemical device electrodes of the present invention, foreign substances such as aggregates are hardly generated during storage of the binder for electrochemical device electrodes, and the yield of the fabricated electrodes can be improved.

Since the slurry for an electrochemical device electrode of the present invention contains the binder for an electrochemical device electrode of the present invention, the separator is damaged by the particles contained in the binder (that is, the separator is penetrated by the particles). ) It has an effect that it can be used as a material for forming an electrode constituting an electrochemical device having an extremely low defect occurrence rate and high safety.

Since the electrochemical device electrode of the present invention includes an electrode layer obtained by applying the slurry for an electrochemical device electrode of the present invention to one surface of a current collector, a separator is formed by particles contained in the binder. This produces an effect of constituting an electrochemical device having a very low occurrence rate of defects that are damaged (that is, the separator is penetrated by particles) and that is highly safe.

It is explanatory drawing which shows typically the filtration apparatus used in one Embodiment of the manufacturing method of the binder for electrochemical device electrodes of this invention.

Hereinafter, although the form for implementing this invention is demonstrated, this invention is not limited to the following embodiment. That is, it is understood that modifications and improvements as appropriate to the following embodiments are also within the scope of the present invention based on ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. Should be.

[1] Electrochemical device electrode binder:
The binder for an electrochemical device electrode of the present invention is obtained by polymerizing a polymerizable monomer. When measured with a particle counter, the number of particles having a particle diameter of 20 μm or more per mL is 0. Is. In such a binder for an electrochemical device electrode, since the number of particles having a particle diameter of 20 μm or more per mL when measured with a particle counter is 0, the separator is damaged by the particles contained in the binder (that is, The separator can be used as a material for forming an electrode that constitutes an electrochemical device that has a very low incidence of defects and is highly safe.

Since the conventional binder is not operated to remove particles larger than the predetermined particle size, it is considered that particles larger than the predetermined particle size are included. Therefore, if the large particles are charged when an electric current flows, the large particles may be drawn to the electrode side across the separator and may penetrate the separator or cause a crack to penetrate the separator. was there. As described above, the conventional binder may cause a failure in which the separator is damaged (specifically, a failure in which the large particles penetrate the separator or cause a crack to penetrate the separator). It was. When the separator is damaged, the electrochemical device is energized, and thus the electrochemical device may cause a hard short circuit. When the hard short circuit occurs, there is a problem that the electrochemical device ignites in rare cases, for example. On the other hand, according to the binder for an electrochemical device electrode of the present invention, since it does not contain particles (particles larger than a predetermined particle size) that penetrate the separator or cause cracks to penetrate the separator, There is no such problem, and an electrode of an electrochemical device with high safety can be produced. Here, the particles larger than the predetermined particle diameter are specifically particles having a particle diameter of the same size as the thickness of the separator separating the positive electrode and the negative electrode. The thickness of the separator is usually 10 to 30 μm. If the thickness of the separator is less than 10 μm, the separator is easily damaged and may cause a failure of the electrochemical device.

The binder for an electrochemical device electrode of the present invention is not particularly limited as long as the above conditions are satisfied. In addition to the above conditions, the number of particles having a particle diameter of 15 μm or more and less than 20 μm per mL when measured with a particle counter. Is preferably 0 to 35000, more preferably 0 to 4000. Further, the number of particles having a particle diameter of more than 10 μm and less than 15 μm per mL when measured with a particle counter is more preferably 0 to 500,000, and still more preferably 0 to 200000. Thus, when the particle | grains of a predetermined | prescribed particle diameter are in the said range, possibility that a separator will be damaged by these particles can be made still lower. In addition, the binder tends to be a resistance component, and when this binder is localized, there is a problem that the resistance is likely to increase. However, by setting the particles having a predetermined particle diameter within the above range, the binder is not easily localized. Therefore, there is an advantage that the resistance is hardly increased.

In the present invention, the number of particles per mL is measured with a particle counter, and the number of particles is defined for each predetermined particle diameter. That is, the binder for an electrochemical device electrode of the present invention does not contain any particles having a particle diameter of 20 μm or more per mL.

As described above, the binder for an electrochemical device electrode of the present invention is obtained by polymerizing a polymerizable monomer. In other words, it includes a polymer having a structural unit derived from the polymerizable monomer, and this polymer exhibits a function as a binder.

In the binder for an electrochemical device electrode of the present invention, the solid content concentration of the polymer is preferably 20 to 56% by mass, more preferably 23 to 55% by mass, and 25 to 54% by mass. It is particularly preferred. When the solid content concentration is within the above range, the polymer particles are stabilized in the binder (exist in a well dispersed state), so that there is an advantage that a binder having excellent long-term stability can be obtained. When the solid content concentration is less than 20% by mass, there is a problem that productivity is lowered. That is, when the reaction solution obtained by polymerization is used as a binder as it is, it is necessary to lower the concentration of the polymer obtained by polymerization. Therefore, productivity becomes low. On the other hand, if it exceeds 56% by mass, the viscosity of the binder increases excessively, so that long-term stability may not be sufficiently obtained. The solid content concentration differs depending on whether it is for the negative electrode or the positive electrode. For example, the solid content concentration of SBR (styrene-butadiene copolymer) which is a negative electrode binder is 40 to 55% by mass. The solid content concentration of the fluoroacrylic emulsion as a binder is 20 to 50% by mass, preferably 27 to 33% by mass.

The binder for an electrochemical device electrode of the present invention is not particularly limited as long as it is obtained by polymerizing a polymerizable monomer, and can be used as a binder for a positive electrode or a negative electrode.

As the positive electrode binder, for example, the binder described in Japanese Patent No. 3999927 can be exemplified. Specifically, a polymer obtained by polymerizing a polymerizable monomer composed of vinylidene fluoride, a fluorine-containing monomer copolymerizable with vinylidene fluoride, or a hydrocarbon monomer such as ethylene or propylene. Can be included.

Examples of the fluorine-containing monomer copolymerizable with vinylidene fluoride include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether.

And examples of monomers other than the above-mentioned monomers include unsaturated dibasic acid monoesters, vinylene carbonate, and the like. Specific examples of unsaturated dibasic acid monoesters include maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, and citraconic acid monoethyl ester.

Examples of the binder for the negative electrode include those described in JP 2010-129186 A. Specific examples include those containing a polymer obtained by polymerizing a polymerizable monomer comprising a conjugated diene, an aromatic vinyl compound, a (meth) acrylate compound, an ethylenically unsaturated carboxylic acid, or the like. .

Examples of the conjugated diene include 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene, chloroprene and the like. Of these, 1,3-butadiene is preferred. The proportion of the conjugated diene used in the total amount of the polymerizable monomer is preferably 33 to 48.5% by mass, and more preferably 35 to 45% by mass. When the use ratio is less than 33% by mass, the obtained polymer has a high glass transition temperature, and the flexibility of the obtained electrode layer and the adhesion to the current collector tend to be lowered. On the other hand, when the content exceeds 48.5% by mass, the surface of the obtained electrode layer tends to be sticky, and therefore the workability of the electrode layer sticking to a roll during press working may be inferior. There is.

Examples of the aromatic vinyl compound include styrene, α-methylstyrene, p-methylstyrene, vinyltoluene, chlorostyrene, divinylbenzene and the like. Among these, styrene is preferable. The use ratio of the aromatic vinyl compound in the total amount of the polymerizable monomer is preferably 40 to 50% by mass, and more preferably 43 to 48% by mass. When the use ratio is less than 40% by mass, the interaction with the graphite used as the active material is reduced, and as a result, the obtained electrode layer tends to easily lose the active material. On the other hand, when it is more than 50% by mass, the obtained polymer is hard and brittle, and the flexibility of the obtained electrode layer and the adhesion to the current collector tend to be lowered.

Examples of the (meth) acrylate compound include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl ( (Meth) acrylate, n-amyl (meth) acrylate, i-amyl (meth) acrylate, hexyl (meth) acrylate, 2-hexyl (meth) acrylate, octyl (meth) acrylate, i-nonyl (meth) acrylate, decyl ( Examples include meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate, and ethylene glycol (meth) acrylate. Among these, methyl (meth) acrylate, n-butyl (meth) acrylate and i-butyl (meth) acrylate are preferable, and methyl (meth) acrylate is particularly preferable.

The proportion of the (meth) acrylate compound used in the total amount of the polymerizable monomer is preferably 8 to 12.5% by mass, and more preferably 9 to 12% by mass. When the use ratio is less than 8% by mass, the obtained polymer has low affinity with the electrolytic solution, and the binder tends to be an electric resistance component in the electrochemical device. Therefore, the device internal resistance tends to increase. On the other hand, when the content is 12.5% by mass, the obtained polymer has excessive absorption of the electrolytic solution, and the binding property is easily lost in the electrochemical device. For this reason, the battery is likely to be deteriorated during high-temperature storage.

Examples of the ethylenically unsaturated carboxylic acid include (meth) acrylic acid and itaconic acid. The use ratio of the ethylenically unsaturated carboxylic acid in the total amount of the polymerizable monomer is preferably 0.1 to 20% by mass, and more preferably 0.2 to 15% by mass. When the use ratio is less than 0.1% by mass, the dispersion stability of the polymer particles is insufficient when the slurry for an electrochemical device electrode is prepared, and aggregates are easily generated. Therefore, there is a tendency that problems such as a decrease in the adhesion of the resulting electrode layer to the current collector tend to occur. On the other hand, if it exceeds 20% by mass, the slurry viscosity increases with time in the storage process after the preparation of the slurry for electrochemical device electrodes, and the slurry tends to be inferior in coatability.

Examples of polymerizable monomers include, in addition to the above monomers, alkyl amides of ethylenically unsaturated carboxylic acids such as (meth) acrylamide and N-methylol acrylamide; vinyl carboxylates such as vinyl acetate and vinyl propionate. Esters; acid anhydrides, monoalkyl esters, monoamides of ethylenically unsaturated dicarboxylic acids; aminoalkyl amides of ethylenically unsaturated carboxylic acids such as aminoethyl acrylamide, dimethylaminomethyl methacrylamide, methylaminopropyl methacrylamide; ) Vinyl cyanide compounds such as acrylonitrile and α-chloroacrylonitrile.

In addition, the binder for electrochemical device electrodes of the present invention may contain an emulsifier, a polymerization initiator, a molecular weight regulator, etc. used in the polymerization step described later, in addition to the polymer.

[2] Method for producing binder for electrochemical device electrode:
The method for producing a binder for an electrochemical device electrode of the present invention is a method for producing the above-described binder for an electrochemical device electrode of the present invention, and a reaction liquid containing a polymer is obtained by polymerizing a polymerizable monomer. Then, the obtained reaction solution is filtered using a depth type or pleat type filter. Since it has such a process, the separator is damaged by the particles contained in the binder (that is, the separator is penetrated by the particles), and the electrode forming the electrochemical device that has a very low incidence of defects and high safety is formed. Thus, a binder for an electrochemical device electrode can be produced. The electrode binder is usually manufactured in a place that is not in a maintained environment such as a clean room.

[2-1] Polymerization step:
In the method for producing a binder for an electrochemical device electrode of the present invention, a conventionally known method can be adopted as a method for obtaining a reaction solution containing a polymer by polymerizing a polymerizable monomer (polymerization step). . For example, methods described in JP 2010-129186 A, JP 3999927 A, and the like can be mentioned.

Specifically, when producing a binder for a positive electrode, a reaction liquid containing a polymer is obtained by polymerizing a polymerizable monomer such as vinylidene fluoride by a method such as suspension polymerization, emulsion polymerization, or solution polymerization. The method of obtaining can be mentioned. Among these, aqueous suspension polymerization and emulsion polymerization are preferable from the viewpoint of ease of post-treatment and the like, and aqueous suspension polymerization is particularly preferable.

In suspension polymerization, for example, methyl cellulose, methoxylated methyl cellulose, propoxylated methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, gelatin and the like can be used as a suspending agent. The suspending agent is preferably added in the range of 0.005 to 1.0% by mass, and preferably in the range of 0.01 to 0.4% by mass with respect to the dispersion medium (eg water). Is more preferable.

Examples of the polymerization initiator include diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, and di (perfluoro). Acyl) peroxide and the like can be used. The amount of the polymerization initiator used is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the total amount of polymerizable monomers. .

In suspension polymerization, a chain transfer agent may be added. Examples of the chain transfer agent include ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, tetra Examples thereof include carbon chloride. Usually, the amount of the chain transfer agent used is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the total amount of polymerizable monomers. preferable.

The total charged amount of the polymerizable monomers is preferably 1: 1 to 1:10, and preferably 1: 2 to 1: 5 in terms of the total amount of polymerizable monomers: dispersion medium. Is more preferable. The polymerization conditions can be 10 to 50 ° C. and 10 to 100 hours.

Further, when preparing a binder for a negative electrode, a method for obtaining a reaction liquid containing a polymer by emulsion polymerization of a polymerizable monomer in an aqueous medium in the presence of an emulsifier, a polymerization initiator, and a molecular weight regulator. Can be mentioned.

As the emulsifier, anionic surfactants, nonionic surfactants, amphoteric surfactants and the like can be used alone or in combination of two or more. As the anionic surfactant, sulfates of higher alcohols, alkylbenzene sulfonates, aliphatic sulfonates, sulfates of polyethylene glycol alkyl ethers, and the like can be used. As the nonionic surfactant, an alkyl ester type of polyethylene glycol, an alkyl ether type, an alkylphenyl ether type, or the like can be used. Specific examples of amphoteric surfactants include those in which the anion moiety is a carboxylate salt, sulfate ester salt, sulfonate salt, or phosphate ester salt, and the cation moiety is an amine salt or a quaternary ammonium salt. Can do. More specifically, examples include amino acids such as bentines such as lauryl betaine and stearyl betaine, lauryl-β-alanine, lauryl di (aminoethyl) glycine, and octyldi (aminoethyl) glycine. The amount of the emulsifier used is preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the total amount of polymerizable monomers used.

Examples of the polymerization initiator include water-soluble polymerization initiators such as sodium persulfate, potassium persulfate, and ammonium persulfate, and oil-soluble polymerization initiators such as benzoyl peroxide, lauryl peroxide, and 2,2′-azobisisobutyronitrile. Redox polymerization initiators in combination with a reducing agent such as sodium bisulfite can be used alone or in combination of two or more. The amount of the polymerization initiator used is preferably 0.3 to 3 parts by mass with respect to 100 parts by mass of the total amount of polymerizable monomers.

Examples of molecular weight modifiers include halogenated hydrocarbons such as chloroform and carbon tetrachloride, mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, n-todecyl mercaptan, t-dotezyl mercaptan and thioglycolic acid, dimethyl Those used in usual emulsion polymerization such as xanthogens such as xanthogen disulfide and diisopropylxanthogen disulfide, terpinolene and α-methylstyrene dimer can be used. The usage-amount of a molecular weight regulator is 5 mass parts or less normally with respect to 100 mass parts of whole quantity of a polymerizable monomer.

The emulsion polymerization may be one-stage, but is preferably a two-stage emulsion polymerization. In the case of the two-stage emulsion polymerization, the first stage emulsion polymerization preferably has a polymerization temperature of, for example, 40 to 80 ° C., a polymerization time of, for example, 2 to 4 hours, and a polymerization conversion rate of 50% or more. It is preferable that it is 60% or more. In the second stage emulsion polymerization, it is preferable that the polymerization temperature is, for example, 40 to 80 ° C., and the polymerization time is, for example, 2 to 6 hours.

The polymer in the resulting reaction solution is not particularly limited as long as the electrochemical device electrode binder of the present invention exhibits a function as a binder, but the number average particle diameter is preferably 50 to 400 nm, More preferably, it is 100 to 300 nm. Here, the “number average particle size” in the present specification is a value measured by a concentrated particle size analyzer “FPAR-1000” (trade name) (manufactured by Otsuka Electronics Co., Ltd.).

The polymer preferably has a glass transition temperature of −50 to + 25 ° C., more preferably −30 to + 5 ° C. Here, in the present specification, “glass transition temperature” means that a polymer film is formed by applying a binder to a glass plate and drying at 120 ° C. for 1 hour. It is a glass transition temperature (Tg) measured using a meter (for example, “differential scanning calorimeter” manufactured by Seiko Denshi Kogyo Co., Ltd.).

[2-2] Filtration step:
In the method for producing the binder for an electrochemical device electrode of the present invention, the reaction solution obtained as described above is filtered with a depth type or pleat type filter and measured with a particle counter per mL. A filtrate in which the number of particles having a particle diameter of 20 μm or more is 0 is obtained.

Here, in this specification, the depth type filter is a high-precision filtration filter also referred to as a depth filtration or volume filtration type filter. Such depth type filters include those having a laminated structure in which filtration membranes having a large number of pores are laminated, and those in which fiber bundles are wound up. Specific examples of depth type filters include Profile II, Nexis NXA, Nexis NXT, Polyfine XLD, Ultiplez Profile, etc. (all manufactured by Nippon Pole), depth cartridge filters, wind cartridge filters, etc. (all, Advantech) Co., Ltd.), CP filter, BM filter, etc. (all manufactured by Chisso Corporation), slope pure, diamond, micro-Syria, etc. (all manufactured by Loki Techno Co.), and the like.

As the depth type filter, it is preferable to use a filter having a rated filtration accuracy of 1.0 to 20 μm, and more preferably 5.0 to 10 μm. By using a filter having a rated filtration accuracy within the above range, it is possible to efficiently obtain a filtrate in which the number of particles having a particle diameter of 20 μm or more per mL when measured with a particle counter is zero. Also, the usable period of the filter is extended because the number of coarse particles trapped in the filter is minimized.

In addition, the pleated type filter is formed by fold-folding a microfiltration membrane sheet made of non-woven fabric, filter paper, metal mesh, etc., and then forming into a cylindrical shape and sealing the crease seam of the sheet in a liquid-tight manner, and It is a cylindrical high-precision filtration filter obtained by sealing both ends of a cylinder liquid-tightly.

As the pleated type filter, a filter having a rated filtration accuracy of 1.0 to 20 μm is preferably used, and a filter having a rating of 5.0 to 10 μm is more preferable. By using a filter having a rated filtration accuracy within the above range, it is possible to efficiently obtain a filtrate in which the number of particles having a particle diameter of 20 μm or more per mL when measured with a particle counter is zero. Also, the usable period of the filter is extended because the number of coarse particles trapped in the filter is minimized.

Specific examples of pleat type filters include HDCII, Polyfine II, etc. (all manufactured by Nippon Pole), PP pleated cartridge filter (manufactured by Advantech), Porous Fine (manufactured by Chisso), Sirton Pore, Micropure, etc (All manufactured by Loki Techno Co., Ltd.).

The filtration conditions (pressure difference before and after the filter (differential pressure), liquid temperature, etc.) are as follows. When measuring with a particle counter, a filtrate with 0 particles having a particle diameter of 20 μm or more per mL is obtained. There is no particular limitation as long as it can. For example, the differential pressure may be set as appropriate within a range that does not exceed the maximum differential pressure resistance of the filter to be used. Specifically, the differential pressure is preferably 0.2 to 0.4 MPaG. The liquid temperature is preferably 10 to 50 ° C.

The filtration step can be performed using, for example, a filtration device 100 as shown in FIG. The filtration device 100 includes a supply tank 1 for storing and supplying an electrochemical device electrode binder before foreign matter removal, a metering pump 2 for flowing the electrochemical device electrode binder before foreign matter removal at a constant flow rate, and a cartridge filter. (Not shown) and a filter 4 having a housing in which the cartridge filter is housed (mounted), a pulsation preventer 3 located in the middle of the metering pump 2 and the filter 4, a pulsation preventer 3 and a filter 4 The 1st pressure gauge 7a arrange | positioned between these, and the 2nd pressure gauge 7b arrange | positioned downstream of the filter 4 are provided. The filtration device 100 includes a return conduit 6 that returns the binder from the filter 4 to the supply tank 1, and a discharge conduit 5 that discharges the binder for an electrochemical device electrode filtered by the filter 4.

In the filtration device 100, the reaction solution obtained in the polymerization step is supplied from the supply tank 1 to the pulsation preventer 3 that has been pressurized by the metering pump 2. When there is a pulsation by the metering pump 2, the pulsation is reduced by the pulsation preventer 3. The reaction liquid discharged from the pulsation preventer 3 is supplied to the filter 4 and removed through the discharge conduit 5 after removing foreign substances. The recovered liquid recovered is an electrochemical device electrode binder. Here, in this specification, “foreign matter” means particles having a particle diameter of 20 μm or more. The material of the particles is not particularly limited as long as the particle diameter is 20 μm or more, and is a metal, a resin, a mixture thereof, or the like.

If the removal of foreign substances in the liquid collected through the discharge conduit 5 is not sufficient, the recovered liquid is returned to the supply tank 1 through the return conduit 6 without returning to the electrochemical device electrode binder, and the filter 4 again. It can also be filtered. Moreover, when the pulsation by the metering pump 2 does not occur, the pulsation preventer 3 may not be disposed. Furthermore, when the viscosity of the reaction solution is high, the viscosity of the reaction solution can be lowered by heating the supply tank, the conduit, or both of them. That is, you may further provide the heating means which can heat a supply tank, a conduit | pipe, or both. In this way, productivity can be improved when the viscosity of the reaction solution is high.

In addition, although the filtration apparatus 100 is provided with the 1st pressure gauge 7a and the 2nd pressure gauge 7b, you may use the filtration apparatus which is not provided with a pressure gauge. However, by providing the first pressure gauge 7a and the second pressure gauge 7b, the differential pressure generated in the filter can be managed so that the filter functions normally. Moreover, it may replace with the supply tank 1 and may supply the binder for electrochemical device electrodes before foreign material removal directly from the container for conveyance. And although the filtration apparatus 100 is an example using the single filter 4, a several filter can also be used. When using a some filter, a some filter may be connected in series and you may arrange | position in parallel.

[3] Storage method of binder for electrochemical device electrode:
The method for storing a binder for an electrochemical device electrode of the present invention can store the binder for an electrochemical device electrode containing polymer particles and water well (that is, in a state where no foreign matter is generated) for a long period of time. And the preservation | save method of this invention can be suitably employ | adopted as a preservation | save method of the binder for electrochemical device electrodes which is produced by the above-mentioned method, and the number of particles with a particle diameter of 20 micrometers or more per mL is zero. . In particular, when the polymer contained in the binder for an electrochemical device electrode contains a polymer that easily aggregates (for example, a fluorine-based polymer), the preservation method of the present invention exhibits a better effect.

In the storage method of the present invention, it is essential to store the electrochemical device electrode binder at a temperature of 2 to 30 ° C., preferably 10 to 25 ° C. When the upper limit of the above range is exceeded, polymer particles aggregate at the portion of the interface between the void and the electrochemical device electrode binder that contacts the wall surface of the container during long-term storage, and foreign matter is generated. Therefore, it cannot be stored stably for a long time. When it is less than the lower limit of the above range, polymer particles aggregate in the binder for an electrochemical device electrode, and a gel or foreign matter is generated. Therefore, it cannot be stored stably for a long time.

In the storage method of the present invention, the inner volume of the container is equal to the volume of the void portion excluding the volume occupied by the binder for the electrochemical device electrode from the inner volume of the container filled with the electrochemical device electrode binder. It is essential that the ratio (%) (hereinafter also referred to as “porosity”) is 1 to 20%, preferably 3 to 15%, more preferably 5 to 10%. When the porosity exceeds the upper limit of the above range, the volatilization amount of water increases when the storage temperature changes, and as a result, the amount of vapor is increased at the gas-liquid interface (the interface between the void and the electrochemical device electrode binder). Aggregation of coalesced particles occurs and foreign matter is generated. Therefore, it cannot be stably stored. When the porosity is less than the lower limit of the above range, when the volume of the electrochemical device electrode binder changes due to a change in storage temperature, the container is deformed or the container is ruptured. Therefore, it cannot be stably stored.

In the preservation method of the present invention, the oxygen concentration in the void is preferably 1% or less. When the oxygen concentration in the voids is within the above range, the binder component (the component contained in the binder for electrochemical device electrodes) is not oxidized or deteriorated during long-term storage, thereby suppressing aggregation of the polymer particles. be able to. Therefore, the generation of foreign matters can be effectively suppressed. The oxygen concentration is a value obtained by measuring the concentration in the void immediately before sealing the container using an oxygen concentration meter (model number “OXY-1S” manufactured by Jiko Co., Ltd.).

In the storage method of the present invention, it is preferable that the elution rate of metal ions from the container for storing the binder for an electrochemical device electrode is 50 ppm or less. When the metal ions are eluted in the electrochemical device electrode binder, the zeta potential balance on the particle surface contributing to the dispersion of the polymer particles in the electrochemical device electrode binder is lost. For this reason, aggregation easily occurs. When the polymer particles aggregated in this way are contained, a smooth active material layer cannot be formed, or when producing an electricity storage device, the aggregated polymer particles break through the separator, and the positive electrode and the negative electrode This is not preferable because there is a high possibility of causing a fatal problem such as short-circuiting the circuit.

In addition, as such a container with little elution of metal ions, a container made of glass or resin is preferable. For example, a clean container manufactured according to JP-A-59-035043 can be preferably used.

According to the storage method of the present invention, the quality of the binder for an electrochemical device electrode hardly changes during storage even if the storage period is sequentially extended to June, December, and 18 months. Moreover, a gel-like thing is not produced. For this reason, the same active material layer can be formed on the same conditions as forming an active material layer using the binder for electrochemical device electrodes immediately after manufacture. Moreover, the effect which can improve the productivity of the binder for electrochemical device electrodes becomes so large that a storage period becomes long in June, December, and 18 months.

[4] Slurry for electrochemical device electrode:
The slurry for an electrochemical device electrode of the present invention contains the above-mentioned binder for an electrochemical device electrode of the present invention and an electrode active material. Since such a slurry for an electrochemical device electrode contains the binder for an electrochemical device electrode of the present invention, the separator is damaged by the particles contained in the binder (that is, the separator is penetrated by the particles). ) It can be used as a material for forming an electrode constituting an electrochemical device having a very low defect occurrence rate and high safety. The slurry for an electrochemical device electrode of the present invention can be prepared by mixing the binder for an electrochemical device electrode of the present invention and an electrode active material.

[4-1] Electrode active material:
The electrode active material is not particularly limited. When used for lithium ion secondary battery electrodes, by firing carbon, carbon materials obtained by firing organic polymer compounds such as phenolic resin, polyacrylonitrile, cellulose, etc. The obtained carbon material, artificial graphite, natural graphite and the like can be used. Moreover, when using for an electric double layer capacitor electrode, activated carbon, activated carbon fiber, silica, alumina, etc. can be used. Further, when used for a lithium ion capacitor electrode, a carbon material such as graphite, non-graphitizable carbon, hard carbon, coke, polyacene organic semiconductor (PAS), or the like can be used.

The slurry for electrochemical device electrodes of the present invention includes thickeners, dispersants such as sodium hexametaphosphate, sodium tripolyphosphate, sodium polyacrylate, nonionic or anionic surfactants as latex stabilizers, Additives such as foaming agents may be contained.

In the slurry for an electrochemical device electrode of the present invention, the solid content in the electrode binder is preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the electrode active material. Is more preferably 3 to 3 parts by mass, particularly preferably 0.3 to 3 parts by mass, and most preferably 0.5 to 2 parts by mass. When the ratio of the solid content of the electrode binder is too small, good adhesion tends not to be obtained. On the other hand, when the ratio of the solid content of the binder for electrodes is excessive, the overvoltage tends to increase and affect the battery characteristics. Furthermore, there exists a possibility that the favorable adhesiveness of an electrode layer and a collector may not be acquired as the said content rate is less than 0.1 mass part. On the other hand, if it exceeds 10 parts by mass, it may be difficult to sufficiently improve battery characteristics.

In the preparation of the slurry for electrochemical device electrodes of the present invention, as means for mixing the binder for electrochemical device electrodes, the electrode active material, and the additive used as necessary, a stirrer, a defoamer, a bead mill, A high-pressure homogenizer can be used. In addition, the electrode slurry can be prepared under reduced pressure. By carrying out under reduced pressure, it can prevent that a bubble arises in the electrode layer obtained.

[5] Electrochemical device electrode:
The electrochemical device electrode of the present invention is arranged on a plate-like current collector and one surface side of the current collector, and the above-described slurry for an electrochemical device electrode of the present invention is disposed on one surface of the current collector. An electrode layer obtained by coating. Since such an electrochemical device electrode includes an electrode layer obtained by applying the slurry for an electrochemical device electrode of the present invention to one surface of a current collector, a separator is formed by particles contained in the binder. It is possible to construct an electrochemical device that has a very low occurrence rate of defects that are damaged (that is, the separator is penetrated by particles) and that is highly safe. The method for producing an electrochemical device electrode of the present invention is as follows. First, the above-described slurry for an electrochemical device electrode of the present invention is applied to the surface of a flat plate current collector and dried to form a coating film on the current collector. Form a laminate. Thereafter, the obtained laminate is pressed in the thickness direction. In this way, the electrochemical device electrode of the present invention can be produced. In order to form an active material layer from the electrochemical device electrode binder after storage, for example, after adding an active material to the electrochemical device electrode binder after storage to obtain a composition, The composition may be applied to the current collector.

[5-1] Current collector:
As the current collector, a metal foil, an etching metal foil, an expanded metal, or the like can be used. As a material constituting the current collector, a material selected from metal materials such as aluminum, copper, nickel, tantalum, stainless steel, and titanium can be appropriately selected and used according to the type of the target electrochemical device. The current collector has a thickness of 5 to 30 μm, preferably 8 to 25 μm, for example, when an electrode for a lithium secondary battery is formed. For example, in the case of constituting an electrode for an electric double layer capacitor, the thickness is 5 to 100 μm, preferably 10 to 70 μm, more preferably 15 to 30 μm.

[5-2] Electrode layer:
As described above, the electrode layer is disposed on one surface (for example, the surface) side of the current collector, and is obtained by applying the slurry for an electrochemical device electrode of the present invention to one surface of the current collector. is there. As a method of applying the slurry for an electrochemical device electrode, a conventionally known method can be appropriately employed. For example, a spin coating method (spin coating method), a casting coating method, a roll coating method, a slit & spin coating method, a doctor blade method, a reverse roll method, a comma bar method, a gravure method, an air knife method and the like can be mentioned.

In addition, as a condition for drying treatment of the coating film made of the slurry for electrochemical device electrodes, the treatment temperature is preferably 20 to 250 ° C., for example, and more preferably 50 to 150 ° C. Further, the treatment time is preferably 1 to 120 minutes, for example, and more preferably 5 to 60 minutes.

Moreover, as a means to press-work, a high pressure super press, a soft calendar, a 1-ton press machine, etc. can be utilized. The press working conditions are appropriately set according to the processing machine to be used. The electrode layer thus formed has, for example, a thickness of 40 to 100 μm and a density of 1.3 to 2.0 g / cm ² .

[6] Electrochemical device:
The electrochemical device electrode obtained as described above can be suitably used as an electrode of an electrochemical device such as a lithium ion secondary battery, an electric double layer capacitor, or a lithium ion capacitor. Electrochemical devices are generally formed on the current collector and the surface of the current collector, and are formed on the surface of the current collector and the current collector. And a separator disposed between the positive electrode and the negative electrode, and the thickness of the separator is usually 10 to 10 as described above. 30 μm. If the thickness of the separator is less than 10 μm, the separator is easily damaged by vibration or the like, which may cause a failure of the electrochemical device. The separator is made of a porous film, and examples of the material thereof include polypropylene and polyethylene.

When a lithium ion secondary battery is configured using the obtained electrochemical device electrode, an electrolytic solution in which an electrolyte composed of a lithium compound is dissolved in a solvent is used.

As the electrolyte, for _{example, LiClO 4, LiBF 4, LiI} , LiPF 6, LiCF 3 SO 3, LiAsF 6, LiSbF 6, LiAlCl 4, LiCl, LiBr, LiB (C 2 H 5) 4, LiCH 3 SO 3, LiC _{4 F 9 SO 3, Li (} C 4 F 3 SO 2) 2 N, Li [(CO 2) 2] such as ₂ B and the like.

Examples of the solvent include carbonates such as propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, lactones such as γ-butyrolactone, trimethoxysilane, 1,2-dimethoxyethane, and diethyl ether. , Ethers such as 2-ethoxyethane, tetrahydrofuran and 2-methyltetrahydrofuran, sulfoxides such as dimethyl sulfoxide, oxolanes such as 1,3-dioxolane and 4-methyl-1,3-dioxolane, nitrogen such as acetonitrile and nitromethane Containing compounds, esters such as methyl formate, methyl acetate, butyl acetate, methyl propionate, ethyl propionate, phosphate triester, diglyme, triglyme, tetrag Glymes such as Im, ketones such as acetone, diethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, sulfones such as sulfolane, oxazolidinones such as 2-methyl-2-oxazolidinone, 1,3-propane sultone, 4-butane sultone, And sultone such as naphtha sultone.

Further, when an electric double layer capacitor is constituted using the electrochemical device electrode of the present invention, an electrolyte such as tetraethylammonium tetrafluoroborate, triethylmethylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate is contained in the solvent. A dissolved electrolytic solution is used.

In the case where a lithium ion capacitor is formed using the electrochemical device electrode of the present invention, the same electrolytic solution as in the case of forming the lithium ion secondary battery can be used.

Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples, but the present invention is not limited to these Examples and Comparative Examples. In the description of Examples, “parts” and “%” are based on mass unless otherwise specified. Moreover, the measuring method of various physical-property values and the evaluation method of various characteristics are shown below.

[Number average particle diameter]:
The binder is measured using a dense particle size analyzer “FPAR1000” (manufactured by Otsuka Electronics Co., Ltd.) with an autosampler. In addition, if the number average particle diameter does not change in the particles before and after removing the foreign matter (filtering step), the electrochemical device electrode binder after removing the foreign matter has no change in various properties as a binder (that is, for the electrochemical device electrode). It can be evaluated that the same function as a conventional binder is maintained as a binder.

[Number of particles per mL]:
The particle counter is measured using a particle count particle size distribution measuring device “Accurizer 780APS” manufactured by Particle Sizing Systems. Specifically, the number of coarse particles to be measured is “4000 particles / mL (0.56 μm)” (that is, “4000 particles having a particle diameter larger than 0.56 μm in 1 mL or less”). Repeat the blank measurement with ultrapure water. Thereafter, 100 mL of a binder (sample) diluted 100 times with ultrapure water is prepared, and this sample is set in the particle size distribution analyzer. After the setting, the sample is automatically diluted to the optimum concentration by the particle size distribution analyzer. Thereafter, the particle size distribution measuring device measures the number of particles per mL of the sample twice, and calculates an average value. This average value is multiplied by 100 to obtain the number of particles per 1 mL of binder.

[Hard short presence]:
First, a positive electrode and a negative electrode are prepared. This will be specifically described below.

(Preparation of negative electrode)
In a biaxial planetary mixer (“TK Hibismix 2P-03” manufactured by PRIMIX Corporation), “CMC2200” manufactured by Daicel Chemical Co., Ltd. as a thickener is 1 part in terms of solid content, and graphite is used as a negative electrode active material. In conversion, 100 parts and 68 parts of water are added, and stirring is performed at 60 rpm for 1 hour. Thereafter, 1 part of the binder for an electrochemical device electrode before or after removing foreign matter is added in terms of solid content of the polymer contained, and further stirred for 1 hour to obtain a paste. After adding 34 parts of water to the resulting paste, using a stirring defoamer (product name “Tentaro Netaro” manufactured by THINKY), 2 minutes at 200 rpm, 5 minutes at 1800 rpm, 1800 rpm under vacuum The slurry for an electrochemical device is prepared by stirring and mixing sequentially for 1.5 minutes.

Next, the prepared slurry for electrochemical devices is uniformly applied to the surface of a copper foil current collector (flat current collector) by a doctor blade method so that the film thickness after drying becomes 100 μm. And a drying treatment at 120 ° C. for 20 minutes to form a dry slurry layer on the surface of the current collector. Thereafter, the current collector on which the dry slurry layer is formed on the surface is pressed with a roll press so that the density of the obtained electrode layer is 1.5 g / cm ³ . In this way, a negative electrode comprising the current collector and the electrode layer formed on the surface (one surface) of the current collector is prepared.

(Preparation of positive electrode)
First, 4 parts of PVdF (polyvinylidene fluoride) (in terms of solid content) is added to a biaxial planetary mixer (TK Hibismix 2P-03: manufactured by Primex), and 100 parts of lithium iron phosphate as the positive electrode active material (solid content) Conversion), 5 parts of acetylene black as a conductive agent (in terms of solid content) and 25 parts of N-methylpyrrolidone (NMP) are added and stirred at 60 rpm for 1 hour. Then, after further adding 10 parts of NMP, using a stirring defoaming machine (Awatori Netaro: manufactured by THINKY), 2 minutes at 200 rpm, 5 minutes at 1800 rpm, 1.5 minutes at 1800 rpm under vacuum. Then, the slurry for positive electrode is prepared by stirring and mixing sequentially.

Next, the prepared slurry for positive electrode is uniformly applied to the surface of a current collector (flat plate current collector) made of aluminum foil by a doctor blade method so that the film thickness after drying becomes 90 μm. Drying is carried out at 20 ° C. for 20 minutes to form a dry slurry layer on the surface of the current collector. Thereafter, the current collector with the dry slurry layer formed on the surface thereof is pressed by a roll press so that the density of the obtained electrode layer is 3.8 g / cm ³ . In this way, a positive electrode comprising the current collector and the electrode layer formed on the surface (one surface) of the current collector is produced.

(Production of secondary battery)
Next, two exterior aluminum seals made of rectangular aluminum film are laminated, and in the exterior body in which three sides of the four outer peripheries of these exterior aluminum seals are joined to each other and the remaining one side is unjoined, The negative electrode cut out to 50 mm × 25 mm is placed. Next, a separator (trade name “Celguard # 2400” (manufactured by Celgard), thickness 25 μm) made of a polypropylene porous film cut out to 54 mm × 27 mm is placed on the negative electrode so that air does not enter. An electrolyte is injected into the exterior body. Thereafter, the positive electrode cut out to 48 mm × 23 mm is placed on the separator (position opposite to the negative electrode). Then, a secondary battery (electrochemical device) composed of a bipolar single-layer laminate cell is manufactured by joining and sealing one unbonded side of the outer package by thermocompression bonding with a heating sealing device. . The electrolytic solution used was a solution in which LiPF ₆ was dissolved at a concentration of 1 mol / liter in a solvent of ethylene carbonate / ethyl methyl carbonate = 1/1. These operations are performed in the glove box.

Next, 100 secondary batteries are produced according to the production method described above, and a 60 ° C. storage test is performed on the produced secondary batteries. Specifically, charging is performed for 2.5 hours by the constant current (0.2 C) -constant voltage (4.2 V) method, discharging is performed by the constant current (0.2 C) method, and then the constant current (0.2 C) method is repeated 0.2 C) —100 secondary batteries charged for 2.5 hours in a constant voltage (4.2 V) mode are left in a thermostat set at 60 ° C. for 30 days. Then, the open circuit voltage (OCV) of each secondary battery after being left for 30 days is measured and evaluated. In the evaluation, the decreasing tendency of OCV was used as an index of occurrence of hard short. Specifically, if a significant voltage drop does not occur (if no decrease in OCV can be confirmed), it is determined that there is no hard short, and a sudden voltage drop (a momentary voltage drop) occurs. Is judged to have a hard short.

[Good product rate (%)]:
The non-defective product rate (%) of the secondary battery is calculated from the evaluation of [presence or absence of hard short circuit]. Specifically, the formula: non-defective product ratio of secondary battery (%) = [{(number of secondary batteries subjected to hard short test) − (number of secondary batteries with hard short circuit)} / (Number of secondary batteries subjected to a test for the presence or absence of hard short)] × 100. If the non-defective rate (%) is 98% or more, it can be determined as “good”, and if it is 99% or more, the productivity is greatly improved, so that it can be determined as “better”.

Example 1
In a temperature-controlled reactor equipped with a stirrer, 200 parts of water, 0.1 part of sodium dodecylbenzenesulfonate, 1.0 part of potassium persulfate, 0.5 part of sodium bisulfite, α-methylstyrene dimer 0 .2 parts, 0.1 parts of dodecyl mercaptan, 6.0 parts of butadiene as the conjugated diene, 12.5 parts of styrene as the aromatic vinyl compound, 3.5 parts of methyl methacrylate as the (meth) acrylate compound, ethylenically unsaturated carboxylic acid As a batch, 25 parts of a polymerizable monomer (monomer composition (a)) consisting of 0.5 part of acrylic acid and 2.5 parts of itaconic acid was charged at a temperature of 70 ° C. The temperature was raised and the polymerization reaction was carried out for 2 hours (first stage).

Next, after confirming that the polymerization conversion was 80% or more, 31.5 parts of butadiene as a conjugated diene and 34.5 parts of styrene as an aromatic vinyl compound while maintaining the temperature in the reactor at 70 ° C. A polymerizable monomer (monomer composition) comprising 8.0 parts of methyl methacrylate as the (meth) acrylate compound, 0.5 part of acrylic acid as the ethylenically unsaturated carboxylic acid, and 0.5 part of itaconic acid. b)) 75 parts were added to the vessel (reactor) over 6 hours for polymerization. At this time, when 3 hours had elapsed from the start of addition of the monomer composition (b), 0.5 part of α-methylstyrene dimer and 0.1 part of dodecyl mercaptan were added to the container. After the addition of the monomer composition (b) was completed, the temperature in the container was raised to 80 ° C. and reacted for another 2 hours (second stage).

Then, after the polymerization reaction was completed, the pH of the obtained latex was adjusted to 7.5, residual monomers were removed by steam distillation, and concentrated by vacuum treatment. Thereafter, it was subjected to a Sato-type vibrating screen machine “1200D-1S special type” (manufactured by Koei Sangyo Co., Ltd.) equipped with a 250 mesh filter to obtain a binder for an electrochemical device electrode before foreign matter removal. The obtained binder for an electrochemical device electrode before removing foreign matter had a solid concentration of 48.5% by mass, a pH of 7.8, and a viscosity of 119 mPa · s.

Next, the obtained binder for an electrochemical device electrode before removing the foreign matter was filtered with the filtration device 100 shown in FIG. 1 (filtration step). A filtration apparatus 100 shown in FIG. 1 includes a supply tank 1 for storing and supplying an electrochemical device electrode binder before foreign matter removal, and a metering pump 2 for flowing the electrochemical device electrode binder before foreign matter removal at a constant flow rate. A filter 4 having a cartridge filter (not shown) and a housing containing (mounting) the cartridge filter, a pulsation preventer 3 located in the middle of the metering pump 2 and the filter 4, and a pulsation preventer 3 A first pressure gauge 7 a disposed between the filter 4 and a second pressure gauge 7 b disposed downstream of the filter 4 is provided. The filtration device 100 includes a return conduit 6 that returns the binder from the filter 4 to the supply tank 1, and a discharge conduit 5 that discharges the binder for an electrochemical device electrode filtered by the filter 4.

In this embodiment, the filter 4 is one in which a depth type cartridge filter “Profile II” (manufactured by Nippon Pall Co., Ltd., rated filtration accuracy 10 μm, length 1 inch) is mounted in the housing. The metering pump 2 was an air-driven diaphragm pump, and the differential pressure before and after the filter was 0.34 MPaG. In addition, the number average particle diameter in the binder for electrochemical device electrodes after filtration by the filtration apparatus 100 shown in FIG. 1 was 177 nm.

In Examples 1 to 5 and Comparative Examples 1 to 3, the number average particle diameter is a value measured by a concentrated particle size analyzer “FPAR1000” (manufactured by Otsuka Electronics Co., Ltd.) with an autosampler.

Various evaluations were performed on the binder for an electrochemical device electrode after filtration by the filtration apparatus 100 shown in FIG. The evaluation results are shown in Table 1. As shown in Table 1, in this example, the binder for an electrochemical device electrode after filtration by the filtration device 100 is the number of particles having a particle diameter of 20 μm or more per mL when measured with a particle counter, and the particle diameter is 15 μm. The number of particles having a particle diameter of less than 20 μm and the number of particles having a particle diameter of more than 10 μm and less than 15 μm were all zero.

(Comparative Example 1)
In the same manner as in Example 1, the above-described various evaluations were performed on the “binder for electrochemical device electrode before foreign matter removal” before filtration by the filtration apparatus 100 shown in FIG. The evaluation results are shown in Table 1.

(Example 2)
In the same manner as in Example 1, a binder for an electrochemical device electrode before removing foreign matters was obtained. About the obtained binder for electrochemical device electrodes before foreign material removal, it filtered using the filtration apparatus. The filtration device used in this example was replaced with a depth type cartridge filter “Profile II” (manufactured by Nihon Pall Co., Ltd., rated filtration accuracy 10 μm, length 1 inch) of the filtration device 100 shown in FIG. A type cartridge filter “Profile II” (manufactured by Nippon Pole Co., Ltd., rated filtration accuracy 20 μm, length 1 inch) was used. The differential pressure before and after the filter was 0.25 MPaG. Moreover, the number average particle diameter in the binder for electrochemical device electrodes after filtration was 177 nm. Said various evaluation was performed about the binder for electrochemical device electrodes after filtration with a filtration apparatus. The evaluation results are shown in Table 2.

(Comparative Example 2)
The above-mentioned various evaluations were carried out in the same manner as in Example 2 with respect to the “binder for electrochemical device electrode before removing foreign matter” before filtration by the filtration device used in Example 2. The evaluation results are shown in Table 2.

(Example 3)
In the same manner as in Example 1, a binder for an electrochemical device electrode before removing foreign matters was obtained. The obtained binder for an electrochemical device electrode before removing the foreign matter was filtered using the filtration apparatus 100 shown in FIG. In this example, the differential pressure before and after filtration was set to 0.38 MPaG, and the filtrate was sampled 5 minutes after the start of filtration by the filtration device 100, and the various evaluations were performed. The evaluation results are shown in Table 3. In addition, the number average particle diameter in the binder for electrochemical device electrodes after filtration was 177 nm.

Example 4
The filtrate (electrochemical device electrode binder after filtration by a filtration device) was sampled in the same manner as in Example 3 except that the filtrate after 10 minutes from the start of filtration was sampled. Said various evaluation was performed about the obtained filtrate. The evaluation results are shown in Table 3. In addition, the number average particle diameter in the binder for electrochemical device electrodes after filtration was 177 nm.

(Example 5)
The filtrate (electrochemical device electrode binder after filtration by a filtration apparatus) was sampled in the same manner as in Example 3 except that the filtrate 15 minutes after the start of filtration was sampled. Said various evaluation was performed about the obtained filtrate. The evaluation results are shown in Table 3. In addition, the number average particle diameter in the binder for electrochemical device electrodes after filtration was 177 nm.

(Comparative Example 3)
The above-mentioned various evaluations were performed in the same manner as in Example 3 with respect to the “binder for electrochemical device electrode before foreign matter removal” before filtration by the filtration device used in Example 3. The evaluation results are shown in Table 3. In addition, the number average particle diameter in the binder for electrochemical device electrodes after filtration was 177 nm.

As is clear from Tables 1 to 3, the electrochemical device electrode binders of Examples 1 to 5 were more defective than the electrochemical device electrode binders of Comparative Examples 1 to 3 to break the separator. It was confirmed that the material can be used as a material for constituting an electrode of an electrochemical device having a very low rate and high safety.

(Examples 6 to 10, Comparative Examples 4 to 10)
In Examples 6 and 7 and Comparative Examples 4 to 7, JSR TRD2001 (manufactured by JSR) was used as a binder for an electrochemical device electrode. In Examples 8 to 10 and Comparative Examples 8 to 10, Table 5 As shown, each electrochemical device electrode binder produced in Examples 1 to 3 (electrochemical device electrode binder after filtration) was used to evaluate the presence or absence of hard shorts and the yield rate according to the method described above. did. Furthermore, the [six months storage stability] shown below was evaluated.

[Six months shelf life]:
Table 4 shows the storage temperature (° C.), the ratio of the volume of the void to the internal volume of the container (void ratio (%)), and the oxygen concentration in the gas remaining in the void. , 5 conditions. Then, let stand and store for 6 months. After storage for 6 months, the presence or absence of foreign matter in the binder for electrochemical device electrodes and the container mode are visually observed and evaluated. The evaluation results are shown in Tables 4 and 5. The oxygen concentration was adjusted by placing the electrochemical device electrode binder in a storage container and then blowing high-purity nitrogen into the container to replace the nitrogen.

In the evaluation of the presence or absence of foreign matter, the case where the aggregate (foreign matter) was confirmed visually was regarded as defective (indicated as “N” in Tables 4 and 5), and the case where the aggregate was not confirmed was good (Table 4). , 5 indicates “G”). In the evaluation of the container mode, the case where the change in the container appearance could not be confirmed by visual observation was good (indicated as “G” in Tables 4 and 5), and the case where the change in the container appearance was confirmed was poor (Table 4, 5). In Comparative Examples 5, 6, 8, and 9, “N (Liquid Leakage / Deformation)” indicates that deformation was confirmed in the container appearance, and the binder had leaked.

In Tables 4 and 5, “clean bottle” indicates a 20-liter square can type clean bottle commercially available from Aicello. “Washing polycontainer” refers to the inside of a commercially available 20-liter square can-type polypropylene container washed in pure room with pure water. “Metal can” indicates a commercially available metal can.

From the above results, it was confirmed that the storage method of the present invention was effective as a storage method capable of preventing the generation of foreign substances such as aggregates. That is, according to the storage method of the present invention, it was confirmed that foreign substances such as aggregates are hardly generated during the storage of the binder for an electrochemical device electrode, and the yield of the manufactured electrode can be improved.

The binder for an electrochemical device electrode of the present invention is suitable as a material for an electrode constituting an electrochemical device used as a power source for driving electronic equipment, for example. The slurry for an electrochemical device electrode of the present invention is suitable as a material for an electrode constituting an electrochemical device used as a power source for driving an electronic device, for example. The electrochemical device electrode of the present invention is suitable as an electrode constituting an electrochemical device used as a power source for driving electronic equipment, for example. The method for producing an electrochemical device electrode binder is, for example, a method for producing an electrochemical device electrode binder as an electrode material constituting an electrochemical device used as a power source for driving electronic equipment. The method for preserving the binder for an electrochemical device electrode is suitable as a method for preserving the binder for an electrochemical device electrode that is a material of an electrode constituting an electrochemical device used as a power source for driving an electronic device, for example.

1: supply tank, 2: metering pump, 3: anti-pulsation device, 4: filter, 5: discharge conduit, 6: return conduit, 7a: first pressure gauge, 7b: second pressure gauge, 100: filtration device.

Claims (10)

1. It is obtained by polymerizing a polymerizable monomer,
   A binder for an electrochemical device electrode in which the number of particles having a particle diameter of 20 μm or more per mL is 0 when measured with a particle counter.
2. 2. The binder for an electrochemical device electrode according to claim 1, wherein the number of particles having a particle diameter of 15 μm or more and less than 20 μm per mL is 0 to 35000 as measured with a particle counter.
3. 3. The binder for an electrochemical device electrode according to claim 1, wherein the number of particles having a particle diameter of more than 10 μm and less than 15 μm per mL is 0 to 500,000 as measured with a particle counter.
4. An electrochemical device electrode slurry containing the electrochemical device electrode binder according to any one of claims 1 to 3 and an electrode active material.
5. A flat plate current collector,
   An electrochemical device, comprising: an electrode layer disposed on one surface side of the current collector and obtained by applying the slurry for an electrochemical device electrode according to claim 4 to the one surface of the current collector. electrode.
6. An electrochemical device electrode binder having a filtration step of polymerizing a polymerizable monomer to obtain a reaction solution containing a polymer and then filtering the obtained reaction solution with a depth type or pleat type filter. Production method.
7. The method for producing a binder for an electrochemical device electrode according to claim 6, wherein a filtrate having 0 particles having a particle diameter of 20 µm or more per mL when measured with a particle counter is obtained by the filtration step.
8. The electrochemical device electrode binder containing polymer particles and water is stored at a temperature of 2 ° C. or higher and 30 ° C. or lower and filled with the electrochemical device electrode binder for storage of the electricity. A method for preserving a binder for an electrochemical device electrode, wherein a ratio (%) of the volume of the void portion excluding the volume occupied by the binder for a chemical device electrode to the internal volume of the container is 1 to 20%.
9. The method for storing a binder for an electrochemical device electrode according to claim 8, wherein the oxygen concentration in the void is 1% or less.
10. The method for storing an electrochemical device electrode binder according to claim 8 or 9, wherein the electrochemical device electrode binder is the electrochemical device electrode binder according to any one of claims 1 to 3.

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