JP2013206846A - Slurry composition for secondary battery porous membrane - Google Patents

Abstract

Disclosed is a slurry composition for a secondary battery porous membrane used for producing a secondary battery having excellent output characteristics.
A slurry composition for a secondary battery porous membrane includes non-conductive particles, a binder containing a first polymer and a second polymer, and a dispersion medium, wherein the first polymer contains fluorine. It is a polymer, and the second polymer is a polymer comprising a polymer unit having a nitrile group, a polymer unit having a hydrophilic group, and a linear alkylene polymer unit having 4 or more carbon atoms.
[Selection figure] None

Description

  The present invention relates to a slurry composition for a secondary battery porous membrane, and more specifically, a secondary battery that is formed on the surface of an electrode or separator of a lithium ion secondary battery and has high flexibility and can contribute to improvement of battery cycle characteristics. The present invention relates to a slurry composition for a secondary battery porous membrane for producing a porous membrane. The present invention also relates to a secondary battery electrode, a secondary battery separator and a secondary battery provided with such a secondary battery porous membrane.

  Among batteries in practical use, lithium ion secondary batteries exhibit the highest energy density, and are often used particularly for small electronics. In addition to small-sized applications, development for automobiles is also expected. Among them, there is a demand for extending the life of lithium ion secondary batteries and further improving safety.

  A lithium ion secondary battery generally includes a positive electrode and a negative electrode including an electrode active material layer carried on a current collector, a separator, and a non-aqueous electrolyte. The electrode active material layer usually contains an electrode active material having an average particle diameter of about 5 to 50 μm and a binder for the electrode active material layer. The electrode is usually produced by applying an electrode active material layer slurry containing a powdered electrode active material on a current collector to form an electrode active material layer. Moreover, as a separator for isolating a positive electrode and a negative electrode, the very thin separator about 10-50 micrometers in thickness is normally used. A lithium ion secondary battery is manufactured through a lamination process of an electrode and a separator, a cutting process of cutting into a predetermined electrode shape, and the like.

  However, while passing through this series of manufacturing steps, the electrode active material may be detached from the electrode active material layer, and a part of the detached electrode active material may be contained in the battery as foreign matter. Such a foreign substance has a particle diameter of about 5 to 50 μm and is about the same as the thickness of the separator, and thus may penetrate the separator in the assembled battery and cause a short circuit.

  Further, heat is generated when the battery is operated. As a result, the organic separator made of a stretched resin such as a stretched polyethylene resin is also heated. An organic separator made of a stretched resin generally tends to shrink even at a temperature of 150 ° C. or lower, and easily causes a battery short circuit. In addition, when a sharply shaped protrusion such as a nail penetrates the battery (for example, during a nail penetration test), there is a tendency that a short circuit occurs instantaneously, reaction heat is generated, and the short circuit part expands.

  Therefore, in order to solve such problems, it has been proposed to provide a porous film for a secondary battery containing non-conductive particles such as inorganic filler and a binder on the surface of the electrode or organic separator or inside the organic separator. Yes. By providing such a porous film, the strength of the organic separator or electrode is increased, and safety is improved.

  As a technique related to the porous film as described above, for example, techniques described in Patent Document 1 and Patent Document 2 are known. Patent Document 1 describes a porous film using polyvinylidene fluoride (PVDF) and a rubber-based resin (styrene butadiene rubber, acrylic rubber, butadiene rubber) as a binder. Patent Document 2 describes a porous film using PVDF, acrylic rubber particles, and polytetrafluoroethylene (PTFE) as a binder.

JP 2009-54455 A JP 2011-222537 A

The porous film is usually obtained by preparing a slurry composition in which the material of the porous film is dispersed, and applying and drying the slurry composition. However, according to the study of the present inventor, the porous membrane for a secondary battery described in Patent Documents 1 and 2 does not have sufficient strength and flexibility, and therefore is not electrically conductive from the porous membrane in the manufacturing process of the porous membrane. Particles may be detached (powders). As a result, the output characteristics of the secondary battery may be deteriorated.
Then, an object of this invention is to provide the slurry composition for secondary battery porous films used in order to manufacture the secondary battery excellent in the output characteristic.

The gist of the present invention aimed at solving such problems is as follows.
[1] containing non-conductive particles, a binder containing a first polymer and a second polymer, and a dispersion medium,
The first polymer is a fluorine-containing polymer;
For the secondary battery porous membrane, the second polymer is a polymer comprising a polymer unit having a nitrile group, a polymer unit having a hydrophilic group, and a linear alkylene polymer unit having 4 or more carbon atoms. Slurry composition.

[2] The slurry composition for a secondary battery porous film according to [1], wherein the ratio of the first polymer to the second polymer in the binder is 5:95 to 50:50 by mass ratio. object.

[3] The first polymer is selected from polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The slurry composition for a secondary battery porous membrane according to [1] or [2], which is at least one.

[4] The slurry composition for a secondary battery porous film according to any one of [1] to [3], wherein the second polymer includes a (meth) acrylic acid ester polymerization unit.

[5] A secondary battery porous membrane obtained by forming the slurry composition for a secondary battery porous membrane according to any one of [1] to [4] above into a film shape and drying.

[6] A secondary battery electrode, wherein a current collector, an electrode active material layer, and a porous film are laminated in this order, and the porous film is the secondary battery porous film according to [5] .

[7] A secondary battery separator comprising a laminate of an organic separator and a porous film, wherein the porous film is the secondary battery porous film according to [5].

[8] A secondary battery including a positive electrode, a negative electrode, an organic separator, and an electrolyte solution,
A secondary battery in which the secondary battery porous film according to [5] is laminated on any of the positive electrode, the negative electrode, and the organic separator.

  According to the slurry composition for a secondary battery porous membrane of the present invention, since the specific binder is included, a porous membrane excellent in dispersibility of non-conductive particles can be formed. Since the porous film contains a specific binder, there is almost no detachment (powder off) of non-conductive particles from the porous film in the manufacturing process of the porous film, and as a result, the secondary film has excellent output characteristics and reliability. A battery can be obtained.

[Slurry composition for secondary battery porous membrane]
The slurry composition for a secondary battery porous membrane of the present invention (hereinafter sometimes referred to as “porous membrane slurry”) may be described as a secondary battery porous membrane (hereinafter referred to as “porous membrane”). .) Is a slurry composition. The porous film slurry contains non-conductive particles, a binder having a specific composition, and a dispersion medium, and the non-conductive particles, the binder, and optional components are uniformly dispersed in the dispersion medium as a solid content.

(Non-conductive particles)
It is desired that the non-conductive particles used in the present invention exist stably in a use environment of a secondary battery (such as a lithium ion secondary battery or a nickel hydride secondary battery) and are electrochemically stable.

As the non-conductive particles, for example, various inorganic particles, organic particles, and other particles can be used. Among these, inorganic oxide particles or organic particles are preferable.
The inorganic oxide particles can be preferably used from the viewpoint of improving the reliability of the secondary battery separator because they are excellent in stability and potential stability in the electrolytic solution.
Organic particles have less contamination of metal ions and the like in the particles (hereinafter sometimes referred to as “metal foreign matter”). The metal ions in the particles may form a salt in the vicinity of the electrode, which may cause an increase in the internal resistance of the electrode and a decrease in the cycle characteristics of the secondary battery. That is, it is preferable to use organic particles from the viewpoint of improving the cycle characteristics of the secondary battery.
In addition, as other particles, the surface of conductive metal such as carbon black, graphite, SnO ₂ , ITO, metal powder and fine powder of conductive compound or oxide is surface-treated with a non-electrically conductive substance. By doing so, particles having electrical insulation properties can be mentioned. In the present invention, two or more of the above particles may be used in combination as non-conductive particles.

Examples of inorganic particles include inorganic oxide particles such as aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, BaTiO ₂ , ZrO, and alumina-silica composite oxide; inorganic nitride particles such as aluminum nitride and boron nitride; silicone Covalent crystal particles such as diamond, sparingly soluble ionic crystal particles such as barium sulfate, calcium fluoride, and barium fluoride; clay fine particles such as talc and montmorillonite are used. These particles may be subjected to element substitution, surface treatment, solid solution, or the like, if necessary, or may be a single or a combination of two or more. Among these, inorganic oxide particles are preferable from the viewpoints of stability in an electrolytic solution and potential stability.

  The shape of the inorganic particles is not particularly limited, and may be a needle shape, a rod shape, a spindle shape, a plate shape, or the like. From the viewpoint of effectively preventing penetration of the porous film by foreign matter (especially needle-like materials) when foreign matter is mixed in the battery, the plate shape is preferable.

  When the inorganic particles are plate-like, it is preferable to orient the inorganic particles in the porous film so that the flat plate surface is substantially parallel to the surface of the porous film. Thus, occurrence of a short circuit of the battery can be suppressed more favorably. This is because the inorganic particles are oriented as described above so that the inorganic particles overlap with each other on a part of the flat plate surface, so that the voids (through holes) from one side of the porous film to the other side are linear. It is thought that it is formed in a bent shape (that is, the curvature is increased) instead of being able to prevent lithium dendrite from penetrating the porous film, and the occurrence of a short circuit is suppressed better. It is guessed.

Examples of the plate-like inorganic particles preferably used include various commercially available products, for example, “Sun Lovely” (SiO ₂ ) manufactured by Asahi Glass S-Tech, and pulverized products (TiO ₂ ) of “NST-B1” manufactured by Ishihara Sangyo Co., Ltd. Barium sulfate plate “H series” and “HL series” manufactured by Sakai Chemical Industry Co., Ltd. “Micron White” (talc) manufactured by Hayashi Kasei Co., Ltd. “Bengell” (bentonite) manufactured by Hayashi Kasei Co., Ltd. “BMM” manufactured by Kawai Lime Co., Ltd. ”Or“ BMT ”(Boehmite),“ Cerasure BMT-B ”[Alumina (Al ₂ O ₃ )] manufactured by Kawai Lime Co.,“ Seraph ”(alumina) manufactured by Kinsei Matec Co., Ltd.,“ Yodogawa Mica Z- ”manufactured by Yodogawa Mining Co., Ltd. 20 "(sericite) etc. are available. In addition, SiO ₂ , Al ₂ O ₃ , and ZrO can be produced by the method disclosed in Japanese Patent Application Laid-Open No. 2003-206475.

The average particle diameter of the inorganic particles is preferably 0.005 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.3 to 2 μm.
When the average particle diameter of the inorganic particles is within the above range, the dispersion state of the porous film slurry can be easily controlled, and thus the production of a porous film having a uniform predetermined thickness is facilitated. Furthermore, the binding property with the binder is improved, the detachment of the inorganic particles is prevented even when the porous film is wound, and sufficient safety can be achieved even if the porous film is thinned. Moreover, since it can suppress that the particle filling rate in a porous film becomes high, it can suppress that the ionic conductivity in a porous film falls. Furthermore, the porous membrane of the present invention can be formed thin.

  The average particle diameter of the inorganic particles is determined as an average value of the equivalent circle diameter of each particle by arbitrarily selecting 50 primary particles in an arbitrary field of view from an SEM (scanning electron microscope) image and performing image analysis. be able to.

  The particle size distribution (CV value) of the inorganic particles is preferably 0.5 to 40%, more preferably 0.5 to 30%, and particularly preferably 0.5 to 20%. By setting the particle size distribution of the inorganic particles in the above range, it is possible to maintain a predetermined gap between the non-conductive particles, thereby inhibiting the movement of lithium and increasing the resistance in the secondary battery of the present invention. Can be suppressed. The particle size distribution (CV value) of the inorganic particles is obtained by observing the inorganic particles with an electron microscope, measuring the particle size of 200 or more particles, and obtaining the average particle size and the standard deviation of the particle size. Standard deviation) / (average particle diameter). It means that the larger the CV value, the larger the variation in particle diameter.

Further, the BET specific surface area of the inorganic particles used in the present invention is specifically 0.9 to ²⁰⁰ m ² / g from the viewpoint of suppressing the aggregation of the inorganic particles and optimizing the fluidity of the porous membrane slurry described later. It is preferable that it is 1.5 to 150 m ² / g.

As the organic particles, organic particles having a functional group capable of crosslinking with a functional group of a binder described later (for example, a hydrophilic group in a second polymer described later) are preferable. By using such organic particles, the reactivity with the binder can be increased, so that the dispersibility of non-conductive particles (organic particles) in the porous film slurry is improved.

In the organic particles used in the present invention, the functional group that can be crosslinked with the functional group of the binder refers to a functional group that can form a chemical bond with an anion derived from the functional group of the binder. Include an epoxy group, an N-methylolamide group, an oxazoline group, an allyl group, an isocyanate group, an oxetanyl group, and an alkoxysilane group. Above all, the reactivity with the functional group of the binder is high, so it can be easily crosslinked, and the crosslinking density can be easily controlled by changing the temperature and time during crosslinking. Epoxy groups are preferred and most preferred. In addition, the kind of said functional group may be one type, and may be two or more types.
By using a monomer having a functional group capable of crosslinking with the functional group of the binder when producing the organic particles, the polymerized unit having the functional group can be introduced into the organic particles.

Examples of the monomer having an epoxy group include a monomer containing a carbon-carbon double bond and an epoxy group, and a monomer containing a halogen atom and an epoxy group.
Examples of the monomer containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether; butadiene monoepoxide, Diene or polyene monoepoxides such as chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene; -Alkenyl epoxides such as epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate Glycidyl esters of unsaturated carboxylic acids such as glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid, etc. Can be mentioned.
Examples of the monomer containing a halogen atom and an epoxy group include epihalohydrins such as epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, β-methylepichlorohydrin; p-chlorostyrene oxide; Dibromophenyl glycidyl ether; and the like.

  Examples of the monomer having an N-methylolamide group include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide.

  Examples of the monomer having an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline. 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline, and the like.

  Examples of the monomer having an allyl group include allyl acrylate, allyl methacrylate, and allyl glycidyl ether.

  Examples of the monomer having an isocyanate group include vinyl isocyanate, allyl isocyanate, (meth) acrylic isocyanate, 2- (meth) acryloyloxyethyl isocyanate, 2-isocyanatoethyl (meth) acrylate, m-isopropenyl-α, α. -Dimethyl methyl benzyl isocyanate etc. are mentioned.

  Examples of the monomer having an oxetanyl group include 3-((meth) acryloyloxymethyl) oxetane, 3-((meth) acryloyloxymethyl) -2-trifluoromethyloxetane, and 3-((meth) acryloyloxymethyl). -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, 2-((meth) acryloyloxymethyl) -4-trifluoromethyloxetane, and the like.

  Examples of the monomer having an alkoxysilane group include vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropylmethyldimethoxysilane, methacryloxypropyltrimethoxysilane, methacryloxypropylmethyldiethoxysilane, methacryloxypropyltriethoxysilane, 3- And methacryloxytriethoxysilane.

  The content of the functional group in the organic particles is preferably 0.003 to 0.08 mmol / g, more preferably 0.005 to 0.05 mmol / g with respect to the organic particles. By making the amount of functional groups in the organic particles in the above range, the mobility of the functional groups in the organic particles is sufficiently maintained, so that the reactivity with the binder is improved. As a result, the strength of the porous film can be improved.

  It is preferable that the organic particles further include a polyfunctional (meth) acrylate polymer unit. The content ratio of the polyfunctional (meth) acrylate polymer units in the total monomer weight in the organic particles is preferably 50 to 95% by mass, more preferably 60 to 95% by mass, and particularly preferably 70 to 95% by mass. is there. By including polyfunctional (meth) acrylate polymer units in the organic particles, the crosslink density of the organic particles is increased, so that the heat resistance of the organic particles is improved, and the reliability of the resulting secondary battery porous membrane is also improved.

  Polyfunctional (meth) acrylates include polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, neopentyl glycol diacrylate, polypropylene glycol diacrylate, 2,2′-bis ( Diacrylate compounds such as 4-acryloxypropyloxyphenyl) propane and 2,2′-bis (4-acryloxydiethoxyphenyl) propane; trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate, etc. Triacrylate compounds; tetraacrylate compounds such as tetramethylolmethane tetraacrylate; ethylene glycol dimethacrylate, diethylene glycol dimethyl Chrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexane glycol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate Examples include dimethacrylate compounds such as methacrylate, polypropylene glycol dimethacrylate, and 2,2′-bis (4-methacryloxydiethoxyphenyl) propane; and trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate. Among these, it is preferable to use ethylene glycol dimethacrylate or trimethylolpropane trimethacrylate, and it is particularly preferable to use ethylene glycol dimethacrylate. By using ethylene glycol dimethacrylate, the number of crosslinking points increases, so that organic particles having excellent heat resistance can be obtained. As a result, the high-temperature cycle characteristics of the secondary battery are improved. These are preferably used in combination with other crosslinkable monomers such as divinylbenzene and ethylvinylbenzene, and the crosslink density of the organic particles can be further improved by using in combination with the crosslinkable monomer.

  The organic particles may contain an arbitrary polymer unit in addition to the two polymer units. As a monomer (arbitrary monomer) constituting an arbitrary polymerization unit, an aromatic monovinyl compound, a (meth) acrylic acid ester monomer, a conjugated diene monomer, a vinyl ester compound, an α-olefin compound, a cationic monomer Body and a hydroxyl group-containing monomer. Two or more kinds of polymer units derived from these monomers may be contained in the organic particles.

  Examples of the aromatic monovinyl compound include styrene, α-methylstyrene, fluorostyrene, and vinylpyridine.

  Examples of the acrylate monomer include butyl acrylate, 2-ethylhexyl ethyl acrylate, N, N′-dimethylaminoethyl acrylate, and the like.

  Examples of the methacrylic acid ester monomer include butyl methacrylate, 2-ethylhexyl methacrylate, methyl methacrylate, 2-hydroxyethyl methacrylate, N, N′-dimethylaminoethyl methacrylate and the like.

  Examples of the conjugated diene monomer include butadiene and isoprene.

  Examples of the vinyl ester compound include vinyl acetate.

  Examples of the α-olefin compound include 4-methyl-1-pentene.

  Examples of the cationic monomer include dimethylaminoethyl (meth) acrylate and dimethylaminopropyl (meth) acrylate.

Examples of the hydroxyl group-containing monomer include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-buten-1-ol, and 5-hexen-1-ol; acrylate-2-hydroxyethyl, acrylate-2- Ethylenic solvents such as hydroxypropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate and di-2-hydroxypropyl itaconate alkanol esters of saturated carboxylic acids; formula ^{_{CH 2 = CR 1 -COO- (C}} n H 2n O) m -H (m is 2 to 9 integer, n represents 2 to 4 integer, ^{R 1} is hydrogen or An ester of a polyalkylene glycol represented by a methyl group) and (meth) acrylic acid; Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as lu-2 ′-(meth) acryloyloxyphthalate, 2-hydroxyethyl-2 ′-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl ether; Vinyl ethers such as 2-hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2- Mono (meth) allyl ethers of alkylene glycols such as hydroxybutyl ether, (meth) allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, (meth) allyl-6-hydroxyhexyl ether Polyoxyalkylene glycol (meth) monoallyl ethers such as diethylene glycol mono (meth) allyl ether and dipropylene glycol mono (meth) allyl ether; glycerin mono (meth) allyl ether, (meth) allyl-2-chloro-3- Mono (meth) allyl ethers of halogens and hydroxy-substituted products of (poly) alkylene glycol, such as hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; polyphenols such as eugenol, isoeugenol Mono (meth) allyl ether and its halogen-substituted product; (meth) allylthioe of alkylene glycol such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether Ethers; and the like.

  Any one of the above monomers can be used alone or in combination of two or more. Among the above optional monomers, styrene, methyl methacrylate, or a combination thereof is particularly preferable from the viewpoint of reactivity with a crosslinkable monomer such as divinylbenzene or ethylvinylbenzene.

  The content ratio of arbitrary polymerization units in the total monomer weight in the organic particles is preferably 3 to 80% by mass, more preferably 4 to 70% by mass, and particularly preferably 5 to 60% by mass. In particular, when styrene and / or methyl methacrylate is included as an optional monomer, the preferable content ratio is 4.5 to 76.5% by mass based on the total amount of monomers constituting the organic particles. In the case where both styrene and methyl methacrylate are contained, it is preferable that the sum thereof is within this range. By setting the content ratio of styrene and / or methyl methacrylate to 76.5% by mass or less, it is possible to prevent the dispersibility of the organic particles from being lowered, increase the strength of the porous film, and obtain film uniformity. be able to. On the other hand, by setting the content ratio of styrene and / or methyl methacrylate to 4.5% by mass or more, the heat resistance of the organic particles can be improved, so that the heat resistance of the porous film can be improved, and thus at a high temperature. Generation | occurrence | production of the short circuit of a battery can be reduced.

(Method for producing organic particles)
The method for producing the organic particles is not particularly limited, and the above-described monomers constituting the organic particles and other optional components as necessary are dissolved or dispersed in a dispersion medium, and an emulsion polymerization method or a soap-free polymerization method. The method of superposing | polymerizing in this dispersion liquid is mentioned.

  In emulsion polymerization, it is preferable to carry out the polymerization in a plurality of stages in order to obtain a desired particle diameter and average circularity. For example, a seed polymer particle is formed by first polymerizing a part of the monomer constituting the organic particle, and then the other polymer is absorbed by the seed polymer particle and polymerization is performed in that state. Organic particles can be produced (seed polymerization method). Furthermore, when forming the seed polymer particles, the polymerization can be further divided into a plurality of stages.

  More specifically, for example, the seed polymer particle A is formed using a part of the monomer constituting the organic particle, and the seed polymer particle A and another monomer constituting the organic particle are used. A seed polymer particle B having a larger particle size, and further using the seed polymer particle B and the remaining monomer constituting the organic particle and other optional components as necessary, Organic particles having a large particle size can be formed. Thus, there is an advantage that a desired particle diameter and average circularity can be stably obtained by forming seed polymer particles by a two-step reaction and further forming organic particles. In this case, a part or all (preferably all) of monomers having functional groups capable of crosslinking with the functional groups of the binder among the monomers constituting the organic particles are converted into seed polymer particles A and seed polymer particles B. It is preferable to use it in forming the particles in order to ensure the stability of the particles.

  Since the case where the polymerization is performed in a plurality of stages as described above is also included, the monomers constituting the organic particles may not be in a state where all the monomers are mixed in the polymerization. . When the polymerization is performed in a plurality of stages, in the finally obtained organic particles, the composition of the monomer derived from the polymerization unit constituting the organic particle is the composition of the monomer constituting the organic particle described above. The ratio is preferably satisfied.

  Examples of the dispersion medium that can be used for the polymerization of monomers constituting the organic particles include water, organic solvents, and mixtures thereof. As the organic solvent, those which are inert to radical polymerization and do not inhibit the polymerization of monomers can be used. Examples of the organic solvent include alcohols such as methanol, ethanol, propanol, cyclohexanol and octanol, esters such as dibutyl phthalate and dioctyl phthalate, ketones such as cyclohexanone, and mixtures thereof. Preferably, an aqueous medium such as water is used as a dispersion medium, and emulsion polymerization can be performed as polymerization.

  These amount ratios when the seed polymer particles and the monomer are reacted are preferably 2 to 19 parts by mass, more preferably 3 to 16 parts by mass as the amount of the monomer used with respect to 1 part by mass of the seed polymer particles. Even more preferably, it is 4 to 12 parts by mass. By making the usage-amount of a monomer 2 mass parts or more with respect to 1 mass part of seed polymer particles, the mechanical strength and heat resistance of the organic particle obtained can be improved. Moreover, since the monomer can be efficiently absorbed into the seed polymer particle by setting the amount of the monomer used to 19 parts by mass or less with respect to 1 part by mass of the seed polymer particle, a single amount that is not absorbed by the seed polymer particle. The body weight can be kept in a small range. In addition, since the particle size of the organic particles can be controlled well, the generation of coarse particles having a wide particle size distribution and a large amount of fine particles can be prevented.

Specific operations for the polymerization include a method in which a monomer is added to an aqueous dispersion of seed polymer particles at a time, and a method in which the monomer is divided or continuously added while performing polymerization. It is preferred that the monomer be absorbed by the seed polymer particles before polymerization is initiated and substantial crosslinking occurs in the seed polymer particles.
If the monomer is added after the middle of the polymerization, the monomer is not absorbed by the seed polymer particles, so that a large amount of fine particles are generated, the polymerization stability is deteriorated, and the polymerization reaction may not be maintained. Therefore, it is preferable to add all the monomers to the seed polymer particles before the start of polymerization, or to finish adding all the monomers before the polymerization conversion rate reaches about 30%. In particular, it is preferable to start the polymerization after the monomer is added to the aqueous dispersion of seed polymer particles and stirred before the polymerization starts, and the seed polymer particles absorb this.

An optional component can be added to the polymerization reaction system in addition to the monomer constituting the organic particles and the dispersion medium. Specifically, components such as a polymerization initiator, a surfactant, and a suspension protective agent can be added. As the polymerization initiator, a general water-soluble radical polymerization initiator or oil-soluble radical polymerization initiator can be used, but a monomer that is not absorbed by the seed polymer particles rarely initiates polymerization in the aqueous phase. In view of this, it is preferable to use a water-soluble radical polymerization initiator. Examples of the water-soluble radical polymerization initiator include potassium persulfate, sodium persulfate, cumene hydroperoxide, hydrogen peroxide, or a water-soluble initiator or a reducing agent such as an oil-soluble initiator and sodium bisulfite described later. Redox initiators in combination are mentioned. Examples of the oil-soluble radical polymerization initiator include benzoyl peroxide, α, α′-azobisisobutyronitrile, t-butylperoxy-2-ethylhexanoate, 3,5,5-trimethylhexanoyl A peroxide etc. can be mentioned. Of the oil-soluble radical polymerization initiators, α, α′-azobisisobutyronitrile can be preferably used. In the polymerization reaction, it is preferable to add a small amount of a water-soluble polymerization inhibitor such as potassium dichromate, ferric chloride, or hydroquinone because generation of fine particles can be suppressed.
As the surfactant, a normal one can be used, and examples thereof include anionic emulsifiers such as sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium dialkylsulfosuccinate, and a formalin condensate of naphthalenesulfonic acid. Furthermore, nonionic surfactants such as polyoxyethylene nonylphenyl ether, polyethylene glycol monostearate, sorbitan monostearate can be used in combination. Preferred examples of the suspension protective agent include polyvinyl alcohol, carboxymethyl cellulose, sodium polyacrylate, and a fine powder inorganic compound.

  In the present invention, the most preferable combination of a polymerization initiator and a stabilizer for obtaining organic particles having a target particle size and a narrow particle size distribution with good reproducibility while ensuring the stability of the system during polymerization, A water-soluble radical polymerization initiator is used as the polymerization initiator, and C.I. M.M. C. A surfactant having a concentration equal to or lower than the concentration (critical micelle concentration) and in the vicinity thereof (specifically, 0.3 to 1.0 times the CMC concentration) is used.

(Properties of organic particles)
The shape of the organic particles used in the present invention is not particularly limited to a spherical shape, a needle shape, a rod shape, a spindle shape, a plate shape, or the like, but a spherical shape, a needle shape, or a spindle shape is preferable. It is preferable that the organic particles have high heat resistance from the viewpoint of imparting heat resistance to the porous membrane and improving the reliability of the secondary battery electrode and the secondary battery separator described later. Specifically, the temperature at which the weight loss rate of the organic particles reaches 10% by mass when heated at a heating rate of 10 ° C./min in a nitrogen atmosphere by thermobalance analysis is preferably 250 ° C. or more, more preferably 300 ° C. As described above, it is particularly preferably 360 ° C. or higher. On the other hand, the upper limit of the temperature is not particularly limited, but can be, for example, 450 ° C. or less.

  The average particle diameter of the organic particles is preferably 0.005 to 10 μm, more preferably 0.1 to 5 μm, and particularly preferably 0.3 to 2 μm. By controlling the average particle diameter of the organic particles in the above range, it becomes easy to control the dispersion state of the porous film slurry, so that it is easy to produce a porous film having a uniform predetermined thickness. Moreover, since it can suppress that the particle filling rate in a porous film becomes high, it can suppress that the ionic conductivity in a porous film falls, and can implement | achieve the outstanding cycling characteristics. It is particularly preferable that the average particle diameter of the organic particles be in the range of 0.3 to 2 μm because it is excellent in dispersion, ease of application, and control of voids. The average particle diameter can be obtained from an average value obtained by observing an electron microscope and calculating (a + b) / 2 by taking the longest side of the particle image as a and the shortest side as b for 100 or more particles. .

  The average circularity of the organic particles is preferably 0.900 to 0.995, more preferably 0.91 to 0.98, and particularly preferably 0.92 to 0.97. By setting the average circularity of the organic particles in the above range, the contact area between the organic particles can be maintained moderately, so that the strength and heat resistance of the porous film can be improved. As a result, the reliability of the secondary battery using the porous film can be improved.

Further, the BET specific surface area of the organic particles used in the present invention is specifically 0.9 to ²⁰⁰ m ² / g from the viewpoint of suppressing the aggregation of the organic particles and optimizing the fluidity of the porous membrane slurry. Is preferable, and it is more preferable that it is 1.5-150 m < ² > / g.

  The particle size distribution of the organic particles is preferably 1.00 to 1.4, more preferably 1.00 to 1.3, and particularly preferably 1.00 to 1.2. By setting the particle size distribution of the organic particles within the above range, it is possible to maintain a predetermined gap between the organic particles, thereby inhibiting lithium migration and increasing resistance in the secondary battery of the present invention. be able to. The particle size distribution of the organic particles is obtained by measuring the particle size with a laser diffraction scattering particle size distribution measuring device (LS230) manufactured by Beckman Co., Ltd., and then obtaining the volume average particle size V and the number average particle size N. The ratio V / N can be obtained.

  Moreover, in the organic particle used for this invention, it is preferable to use the organic particle whose content of a metal foreign material is 100 ppm or less from a viewpoint of reducing the metal foreign material which has a bad influence on the performance of a battery. When organic particles containing a large amount of metal foreign matter or metal ions are used, the metal foreign matter (metal ions) is eluted in the porous membrane slurry, which causes ionic crosslinking with the polymer in the porous membrane slurry, and the porous membrane slurry aggregates. As a result, the porosity of the porous film is lowered. Therefore, there is a possibility that the rate characteristic (output characteristic) of the secondary battery using the porous film is deteriorated. As the metal, it is most preferable to contain Ca, Co, Cu, Fe, Mg, Ni, Zn, Cr and the like. Therefore, the metal content in the organic particles is preferably a total amount of these metal ions, preferably 100 ppm or less, more preferably 50 ppm or less. The smaller the content, the less likely the battery characteristics will deteriorate. The term “metal foreign matter” as used herein means a simple metal other than organic particles. The content of the metal foreign matter in the organic particles can be measured using ICP (Inductively Coupled Plasma).

  The content of non-conductive particles with respect to 100 parts by mass of the total solid content of the porous membrane slurry is preferably 70 to 99 parts by mass, more preferably 75 to 98 parts by mass, and particularly preferably 80 to 98 parts by mass. By setting the content of non-conductive particles in the above range, a porous film exhibiting high thermal stability can be obtained. Moreover, desorption (powder off) of non-conductive particles from the porous film in the manufacturing process of the porous film can be suppressed, and a porous film having high strength can be obtained, and cycle characteristics, output characteristics, etc. It is possible to prevent deterioration of battery characteristics.

(binder)
The binder used for this invention comprises the 1st polymer and 2nd polymer which are mentioned later. In the present invention, by using a binder containing the first polymer and the second polymer, a secondary battery porous film having high flexibility and binding property and high strength can be formed.

The first polymer in the first polymer binder contains a fluorine-containing polymer. By containing the fluorine-containing polymer, swelling of the binder with respect to the electrolytic solution can be suppressed, and as a result, desorption (powder off) of the nonconductive particles from the porous film in the manufacturing process of the porous film can be suppressed. Therefore, a porous film having high strength can be obtained, and the output characteristics of the secondary battery can be improved.

  The fluorine-containing polymer used in the present invention is a polymer containing polymer units of fluorine-containing monomers. Specifically, a homopolymer of a fluorine-containing monomer, a copolymer of a fluorine-containing monomer and another fluorine-containing monomer copolymerizable therewith, a copolymer of a fluorine-containing monomer and a monomer copolymerizable therewith And a copolymer of a fluorine-containing monomer, another fluorine-containing monomer copolymerizable therewith, and a monomer copolymerizable therewith.

Examples of the fluorine-containing monomer include vinylidene fluoride, tetrafluoroethylene, hexafluoropropylene, vinyl trifluoride chloride, vinyl fluoride, and perfluoroalkyl vinyl ether, and vinylidene fluoride is preferable.
The proportion of polymer units of the fluorine-containing monomer in the fluorine-containing polymer is usually 70% by mass or more, preferably 80% by mass or more.

Monomers copolymerizable with fluorine-containing monomers include 1-olefins such as ethylene, propylene, and 1-butene; aromatic vinyl compounds such as styrene, α-methylstyrene, pt-butylstyrene, vinyltoluene, and chlorostyrene. Unsaturated nitrile compounds such as (meth) acrylonitrile (abbreviations for acrylonitrile and methacrylonitrile; hereinafter the same); methyl (meth) acrylate, butyl (meth) acrylate, (meth) acrylate 2-ethylhexyl ( (Meth) acrylic acid ester compounds; (meth) acrylamide compounds such as (meth) acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl (meth) acrylamide; (meth) acrylic acid, itaconic acid, fumaric acid, crotonic acid , Maleic acid, etc. Voxyl group-containing vinyl compounds; epoxy group-containing unsaturated compounds such as allyl glycidyl ether and glycidyl (meth) acrylate; amino group-containing unsaturated compounds such as (meth) acryldimethylaminoethyl and diethylaminoethyl (meth) acrylate; styrene Sulfonic acid group-containing unsaturated compounds such as sulfonic acid, vinyl sulfonic acid and (meth) allylsulfonic acid; Sulfuric acid group-containing unsaturated compounds such as 3-allyloxy-2-hydroxypropanesulfuric acid; (meth) acrylic acid-3-chloro And phosphoric acid group-containing unsaturated compounds such as propyl-2-phosphate and 3-allyloxy-2-hydroxypropanephosphoric acid.
In the fluorine-containing polymer, the ratio of the polymerization unit of the monomer copolymerizable with the fluorine-containing monomer is usually 30% by mass or less, preferably 20% by mass or less.
Among the fluorine-containing polymers, a polymer containing vinylidene fluoride as a fluorine-containing monomer, specifically, a homopolymer of vinylidene fluoride, a copolymer of vinylidene fluoride and another fluorine-containing monomer copolymerizable therewith. A polymer, a copolymer of vinylidene fluoride, another fluorine-containing monomer copolymerizable therewith, and a monomer copolymerizable therewith are preferred.

  Among the fluorine-containing polymers as described above, the first polymer used in the present invention includes polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, polyvinyl fluoride, tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymers are preferred, and polyvinylidene fluoride is more preferred.

  The weight average molecular weight in terms of polystyrene by gel permeation chromatography of the first polymer used in the present invention is preferably 100,000 to 2,000,000, more preferably 200,000 to 1,500,000. Especially preferably, it is 400,000-1,000,000. By setting the weight average molecular weight of the first polymer within the above range, desorption (powder off) of the non-conductive particles from the porous film is suppressed, and it is easy to apply the porous film slurry during the production of the porous film slurry. It is easy to adjust the viscosity.

  The glass transition temperature (Tg) of the first polymer used in the present invention is preferably 0 ° C. or lower, more preferably −20 ° C. or lower, particularly preferably −30 ° C. or lower. Although the minimum of Tg of a 1st polymer is not specifically limited, Preferably it is -50 degreeC or more, More preferably, it is -40 degreeC or more. When Tg of the first polymer is in the above range, detachment (powder falling) of the nonconductive particles from the porous film can be suppressed. The Tg of the first polymer can be prepared by combining various monomers. Tg can be measured based on JIS K 7121; 1987 using a differential scanning calorimeter.

  The melting point (Tm) of the first polymer used in the present invention is preferably 190 ° C. or lower, more preferably 150 to 180 ° C., and further preferably 160 to 170 ° C. When Tm of the first polymer is in the above range, an electrode excellent in flexibility and adhesion strength can be obtained. The Tm of the first polymer can be prepared by combining various monomers or controlling the polymerization temperature. Tm can be measured based on JIS K 7121; 1987 using a differential scanning calorimeter.

  The method for producing the first polymer used in the present invention is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. Among these, the suspension polymerization method and the emulsion polymerization method are preferable, and the emulsion polymerization method is more preferable. By producing the first polymer by the emulsion polymerization method, the productivity of the first polymer can be improved, and a first polymer having a desired average particle diameter can be obtained. As the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used. Examples of the polymerization initiator used for polymerization include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Organic peroxides, azo compounds such as α, α′-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like.

The first polymer used in the present invention is used in the state of a dispersion liquid or a dissolved solution dispersed in a dispersion medium (hereinafter, sometimes referred to as “first polymer dispersion liquid”). The dispersion medium is not particularly limited as long as it can uniformly disperse or dissolve the first polymer, and water or an organic solvent can be used. Examples of organic solvents include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, ethylmethylketone, diisopropylketone, cyclohexanone, methylcyclohexane, and ethylcyclohexane. Chlorinated aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; Esters such as ethyl acetate, butyl acetate, γ-butyrolactone and ε-caprolactone; Acylonitriles such as acetonitrile and propionitrile; Tetrahydrofuran and ethylene glycol Ethers such as diethyl ether: alcohols such as methanol, ethanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether; Examples include amides such as loridone and N, N-dimethylformamide.
These dispersion media may be used alone, or two or more of these dispersion media may be mixed and used as a mixed solvent. Among these, in particular, it is used industrially at the time of porous film slurry preparation, it is difficult to volatilize in production, and as a result, volatilization of the porous film slurry can be suppressed, and the smoothness of the resulting porous film is improved. Water, N-methylpyrrolidone, cyclohexanone, toluene and the like are preferable.

  When the first polymer is dispersed in the dispersion medium in the form of particles, the average particle diameter (dispersion particle diameter) of the first polymer dispersed in the form of particles is a volume average particle diameter, preferably The thickness is 10 to 2000 nm, more preferably 50 to 1500 nm, and particularly preferably 100 to 1000 nm. When the average particle size of the first polymer is in the above range, the dispersibility of the porous membrane slurry is improved, and the strength and flexibility of the obtained porous membrane are improved. As a result, the reliability of the secondary battery electrode and secondary battery separator of the present invention is improved.

  In the case where the first polymer is dispersed in the dispersion medium in the form of particles, the solid content concentration of the first polymer dispersion is usually 1 to 25% by mass, preferably 3 to 20% by mass, 15 mass% is further more preferable. When the solid content concentration of the first polymer dispersion is in the above range, workability in producing the porous membrane slurry is good.

  The viscosity when the first polymer is dissolved in NMP so as to be an 8% solution is preferably 10 to 5000 mPa · s, more preferably 100 to 2000 mPa · s. By setting the viscosity of the 8% NMP solution of the first polymer in the above range, it is easy to adjust the viscosity so that the porous film slurry can be easily applied during the production of the porous film slurry. The 8% NMP solution viscosity of the first polymer was obtained by dissolving the first polymer in NMP so as to be an 8% solution, and against this, a B-type viscometer (RB made by Toki Sangyo Co., Ltd.) -80L), and can be measured based on JIS K 7117-1;

The second polymer in the second polymer binder contains a polymer unit having a nitrile group, a polymer unit having a hydrophilic group, and a linear alkylene polymer unit having 4 or more carbon atoms. .

  By including a polymer unit having a nitrile group in the second polymer, the dispersibility of the nonconductive particles in the porous membrane slurry is improved, and the porous membrane slurry can be stored in a stable state for a long period of time. As a result, it becomes easy to produce a porous film in which non-conductive particles are uniformly dispersed. Moreover, since the lithium ion conductivity is good, the internal resistance in the battery can be reduced, and the output characteristics of the battery can be improved.

  The content ratio of the polymer unit having the nitrile group is preferably 2 to 50% by mass, more preferably 10 to 30% by mass, and particularly preferably 10 to 25% by mass. By including a polymer unit having a nitrile group in the second polymer in the above range, the dispersibility of non-conductive particles is improved, and a highly stable porous film slurry can be obtained. As a result, non-conductive A porous film in which particles are uniformly dispersed can be obtained.

By including a polymer unit having a hydrophilic group in the second polymer, non-conductive particles can be stably dispersed in the porous membrane slurry, so that the slurry stability of the porous membrane slurry is improved. Thus, gelation of the porous membrane slurry can be prevented.
The second polymer preferably has a polymer unit having a hydrophilic group in an amount of 0.05 to 20% by mass, more preferably 1 to 10% by mass, still more preferably 1 to 8% by mass, and particularly preferably 1 to Including 6% by mass. By setting the content ratio of the polymer units having a hydrophilic group in the second polymer within the above range, the binding property between the non-conductive particles and between the non-conductive particles and the base material described later is improved. In addition, it is possible to reduce detachment (powder off) of non-conductive particles from the porous film in the manufacturing process of the porous film.

  The hydrophilic group in the present invention refers to a functional group that liberates protons in an aqueous solvent or a salt in which a proton in the functional group is substituted with a cation, specifically, a carboxylic acid group, a sulfonic acid group, Examples include phosphoric acid groups, hydroxyl groups, and salts thereof.

  By containing a linear alkylene polymer unit having 4 or more carbon atoms in the second polymer, the dispersibility of the non-conductive particles in the porous film slurry is improved, and the porous film slurry is stored in a stable state for a long period of time. can do. Therefore, a uniform porous film can be produced even after the porous film slurry has been stored for a long time. Further, by introducing the linear alkylene polymer unit, the stability of the second polymer with respect to the electrolytic solution can be increased, and as a result, a porous film having excellent resistance to the electrolytic solution can be obtained. The battery characteristics can be improved.

  The linear alkylene polymer unit has 4 or more carbon atoms, preferably 4 to 16, more preferably 4 to 12.

  The content ratio of the linear alkylene polymer unit is preferably 20 to 70% by mass, more preferably 30 to 60% by mass, and particularly preferably 40 to 60% by mass.

Moreover, it is preferable that said 2nd polymer contains a (meth) acrylic acid ester polymerization unit. By including the (meth) acrylic acid ester polymerization unit in the second polymer, the second polymer is dissolved in the porous film slurry, and a highly stable porous film slurry can be obtained. Furthermore, since the porous film which has high stability with respect to electrolyte solution and was excellent in electrolyte solution resistance is obtained, it is excellent in the cycling characteristics of a secondary battery.
The second polymer preferably contains (meth) acrylic acid ester polymerized units in an amount of 5 to 50% by mass, more preferably 10 to 40% by mass, and particularly preferably 20 to 35% by mass.
By setting the content ratio of the (meth) acrylic acid ester polymerized unit in the second polymer within the above range, a dispersion medium in the second polymer described later and a dispersion medium in the porous film slurry (for example, N-methylpyrrolidone, Hereinafter, it may be referred to as “NMP.”) The second polymer is dissolved therein and a highly stable porous membrane slurry can be obtained. Furthermore, since the stability to the electrolyte is increased, the secondary battery is particularly excellent in high-temperature cycle characteristics.
Moreover, carbon number of the alkyl group couple | bonded with the non-carbonyl-type oxygen atom of the said (meth) acrylic acid ester polymerization unit becomes like this. Preferably it is the range of 4-10, More preferably, it is the range of 4-8. By setting the number of carbon atoms of the alkyl group bonded to the non-carbonyl oxygen atom of the (meth) acrylic acid ester polymerized unit within the above range, the second polymer is difficult to elute from the electrolytic solution, and the resulting porous membrane The slurry exhibits high slurry stability. Furthermore, the obtained porous film has high uniformity and excellent flexibility.

  As described above, the second polymer constituting the binder used in the present invention has a polymer unit having a nitrile group, a polymer unit having a hydrophilic group, and a linear alkylene polymer unit having 4 or more carbon atoms, It preferably has a (meth) acrylic acid ester polymer unit. Such a second polymer forms a monomer capable of forming a polymer unit having a nitrile group, a monomer capable of forming a polymer unit having a hydrophilic group, and a (meth) acrylate polymer unit. And a monomer capable of forming a linear alkylene polymer unit having 4 or more carbon atoms. A linear alkylene polymer unit having 4 or more carbon atoms is obtained by obtaining a polymer having a structural unit having an unsaturated bond (a polymer unit capable of forming a conjugated diene monomer having 4 or more carbon atoms), and then hydrogenating the polymer. It can be formed by reaction.

Hereinafter, the manufacturing method of the 2nd polymer used for this invention is demonstrated.
Examples of the monomer that can form a polymer unit having a nitrile group include an α, β-ethylenically unsaturated nitrile monomer. The α, β-ethylenically unsaturated nitrile monomer is not particularly limited as long as it is an α, β-ethylenically unsaturated compound having a nitrile group. For example, acrylonitrile; α-chloroacrylonitrile, α-bromoacrylonitrile, etc. [Alpha] -halogenoacrylonitrile; [alpha] -alkylacrylonitrile such as methacrylonitrile; and the like. Among these, acrylonitrile and methacrylonitrile are preferable. These can be used individually by 1 type or in combination of multiple types.

  Introduction of the hydrophilic group into the second polymer is carried out by polymerizing monomers having a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a hydroxyl group, and a salt thereof.

Examples of the monomer having a carboxylic acid group include monocarboxylic acids and derivatives thereof, dicarboxylic acids, and derivatives thereof.
Examples of monocarboxylic acids include acrylic acid, methacrylic acid, and crotonic acid.
Examples of monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, β-diaminoacrylic acid, and the like. Can be mentioned.
Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like.
Dicarboxylic acid derivatives include methyl maleic acid, dimethyl maleic acid, phenyl maleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid and the like methyl allyl maleate, diphenyl maleate, nonyl maleate, decyl maleate, dodecyl maleate, And maleate esters such as octadecyl maleate and fluoroalkyl maleate.
Moreover, the acid anhydride which produces | generates a carboxyl group by hydrolysis can also be used.
Examples of the acid anhydride of dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
In addition, monoethyl maleate, diethyl maleate, monobutyl maleate, dibutyl maleate, monoethyl fumarate, diethyl fumarate, monobutyl fumarate, dibutyl fumarate, monocyclohexyl fumarate, dicyclohexyl fumarate, monoethyl itaconate, diethyl itaconate Also included are monoesters and diesters of α, β-ethylenically unsaturated polyvalent carboxylic acids such as monobutyl itaconate and dibutyl itaconate.

  Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methyl. Examples thereof include propanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid.

  Examples of the monomer having a phosphate group include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, and ethyl phosphate- (meth) acryloyloxyethyl phosphate. .

Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-buten-1-ol, 5-hexen-1-ol; 2-hydroxyethyl acrylate, acrylic acid-2 -Ethylene such as hydroxypropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, di-2-hydroxypropyl itaconate alkanol esters of unsaturated carboxylic acids; formula ^{_{CH 2 = CR 1 -COO- (C}} n H 2n O) m -H (m is 2 to 9 integer, n represents 2 to 4 integer, ^{R 1} is hydrogen Or an ester of polyalkylene glycol represented by (meth) acrylic acid represented by 2-hydro; Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as cyethyl-2 ′-(meth) acryloyloxyphthalate, 2-hydroxyethyl-2 ′-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl ether; Vinyl ethers such as 2-hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2- Mono (meth) allyl ethers of alkylene glycols such as hydroxybutyl ether, (meth) allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, (meth) allyl-6-hydroxyhexyl ether Polyoxyalkylene glycol (meth) monoallyl ethers such as diethylene glycol mono (meth) allyl ether and dipropylene glycol mono (meth) allyl ether; glycerin mono (meth) allyl ether, (meth) allyl-2-chloro Mono (meth) allyl ethers of halogen and hydroxy-substituted products of (poly) alkylene glycols such as -3-hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; eugenol, isoeugenol Mono (meth) allyl ether of monohydric phenol and its halogen-substituted product; (meth) allyl of alkylene glycol such as (meth) allyl-2-hydroxyethylthioether and (meth) allyl-2-hydroxypropylthioether Thioether compounds; and the like.

  Among these, the hydrophilic group is preferably a carboxylic acid group or a sulfonic acid group because it is excellent in binding properties to an electrode active material layer or an organic separator, which will be described later. A carboxylic acid group is particularly preferred because it efficiently captures certain transition metal ions. Therefore, as the monomer having a hydrophilic group, among the above, monocarboxylic acids having 5 or less carbon atoms having carboxylic acid groups such as acrylic acid and methacrylic acid, and carboxylic acid groups such as maleic acid and itaconic acid are used. Two dicarboxylic acids having 5 or less carbon atoms are preferred. Furthermore, acrylic acid and methacrylic acid are particularly preferable from the viewpoint of high storage stability of the produced porous membrane slurry.

  The method for introducing the linear alkylene polymer unit into the second polymer is not particularly limited, but a method in which a polymer unit capable of forming a conjugated diene monomer is introduced and then subjected to a hydrogenation reaction is simple and preferable.

  The conjugated diene monomer is preferably a conjugated diene having 4 or more carbon atoms, and examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene and the like. Of these, 1,3-butadiene is preferred. These can be used individually by 1 type or in combination of multiple types.

  As a monomer capable of forming a polymer unit having a (meth) acrylic acid ester, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, Acrylic acid alkyl esters such as heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n -Butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl meta Relate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n- tetradecyl methacrylate, methacrylic acid alkyl esters such as stearyl methacrylate; and the like.

  Among these, the solubility in NMP, which is preferably used as a dispersion medium for the porous membrane slurry, does not elute into the electrolyte solution, and the flexibility and binding properties of the porous membrane are improved. Since the secondary battery has excellent characteristics (cycle characteristics, output characteristics, etc.), an alkyl acrylate ester having 4 to 10 carbon atoms in the alkyl group bonded to the non-carbonyl oxygen atom is preferable. Preferred are butyl acrylate, 2-ethylhexyl acrylate and lauryl acrylate, more preferred is butyl acrylate, 2-ethylhexyl acrylate, and still more preferred is butyl acrylate.

  Moreover, the 2nd polymer used for this invention may contain the polymerization unit of the other monomer copolymerizable with the monomer which forms these polymerization units other than the said polymerization unit. The content ratio of the polymerization units of such other monomers is preferably 30% by mass or less, more preferably 20% by mass or less, and still more preferably 10% by mass or less with respect to the total monomer units.

  Examples of such other copolymerizable monomers include aromatic vinyl compounds such as styrene, α-methylstyrene, and vinyl toluene; 1,4-pentadiene, 1,4-hexadiene, vinylnorbornene, and dicyclohexane. Non-conjugated diene compounds such as pentadiene; α-olefin compounds such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene and 1-octene; methoxyethyl (meth) acrylate, (meth) acrylic Alkoxyalkyl esters of α, β-ethylenically unsaturated carboxylic acids such as methoxypropyl acid and butoxyethyl (meth) acrylate; divinyl compounds such as divinylbenzene; ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, ethylene glycol Di (meth) acryle In addition to polyfunctional ethylenically unsaturated monomers such as di (meth) acrylic acid esters such as trimethylolpropane tri (meth) acrylate; N-methylol (meth) acrylamide, And self-crosslinking compounds such as N, N′-dimethylol (meth) acrylamide;

  Among them, when NMP is used as a dispersion medium for the porous membrane slurry without eluting into the electrolyte solution, it exhibits solubility in NMP, and in addition, it has excellent dispersibility of non-conductive particles and a uniform porous membrane is obtained. Therefore, aromatic vinyl compounds such as styrene and α-methylstyrene are preferable.

  Furthermore, the 2nd polymer used for this invention may contain the monomer copolymerizable with these other than the monomer component mentioned above. Monomers copolymerizable with these include vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl biether; methyl vinyl ketone, ethyl vinyl ketone and butyl And vinyl ketones such as vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole. By graft-copolymerizing these monomers by an appropriate technique, the second polymer having the above-described configuration can be obtained.

  The second polymer used in the present invention is used in the state of a dispersion or dissolved solution dispersed in a dispersion medium (water or organic solvent) (hereinafter referred to as “second polymer dispersion”). Sometimes.). The dispersion medium is not particularly limited as long as it can uniformly disperse or dissolve the second polymer. In the present invention, the dispersion medium exemplified in the first polymer can be used.

  When the second polymer is dispersed in the dispersion medium in the form of particles, the average particle diameter (dispersion particle diameter) of the second polymer dispersed in the form of particles is a volume average particle diameter, preferably The thickness is 50 to 500 nm, more preferably 70 to 400 nm, and particularly preferably 100 to 250 nm. When the average particle diameter of the second polymer is in the above range, the binding property of the non-conductive particles is improved, so that the flexibility of the obtained porous film is improved and the non-conductive property is improved from the porous film. It is possible to prevent the particles from detaching (powder falling). As a result, the secondary battery using the porous film exhibits excellent safety and cycle characteristics.

  When the second polymer is dispersed in the dispersion medium in the form of particles, the solid content concentration of the second polymer dispersion is usually 15 to 70% by mass, preferably 20 to 65% by mass, and preferably 30 to 60 mass% is more preferable. When the solid content concentration is within this range, workability in producing the porous membrane slurry is good.

  The glass transition temperature (Tg) of the second polymer used in the present invention is preferably 25 ° C. or less, more preferably 15 ° C. or less, and particularly preferably 0 ° C. or less. Although the minimum of Tg of a 2nd polymer is not specifically limited, Preferably it is -50 degreeC or more, More preferably, it is -45 degreeC or more, Most preferably, it is -40 degreeC or more. When the Tg of the second polymer is in the above range, the porous film of the present invention has excellent strength and flexibility. The cycle characteristics and output characteristics of the secondary battery can be improved. The glass transition temperature of the second polymer can be adjusted by combining various monomers.

Moreover, the swelling degree of the second polymer with respect to the electrolytic solution described later is preferably 100 to 500%, more preferably 110 to 400%, and still more preferably 120 to 300%. By setting the degree of swelling of the second polymer within the above range, dissolution of the second polymer in the electrolytic solution can be suppressed, and a second polymer excellent in electrolytic solution resistance and binding properties can be obtained. The cycle characteristics and output characteristics of the secondary battery can be improved.
Here, as an index of the degree of swelling, LiPF _{6 is} added to a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) so that the volume ratio at 20 ° C. becomes EC: DEC = 1: 2. The degree of swelling with respect to a solution in which is dissolved at a concentration of 1.0 mol / L is employed.

  The degree of swelling of the second polymer with respect to the electrolytic solution can be adjusted to the above range by adjusting the type and ratio of all the polymer units constituting the second polymer. For example, in the case of a (meth) acrylic acid ester polymerized unit, a method of adjusting the length of an alkyl chain bonded to a non-carbonyl oxygen atom in the polymerized unit can be mentioned.

The degree of swelling of the second polymer with respect to the electrolytic solution can be adjusted to the above range by adjusting the type and ratio of all the polymer units constituting the second polymer. A parameter (hereinafter referred to as “SP value”) can also be used as the index. For example, the solubility parameter (hereinafter referred to as “SP value”) is preferably 9.0 (cal / cm ³ ) ^1/2 or more and less than 11 (cal / cm ³ ) ^1/2 , more preferably 9 to 10.5 ( cal ^/ cm ^{3) 1/2,} more preferably, such a method is to use a 9.5~10 (cal ^/ cm ³⁾ is ^1/2 or copolymer as the second polymer. By adjusting the SP value within the above range, the second polymer is moderately dissolved in the electrolyte while maintaining the solubility of the second polymer described later in the dispersion medium and the dispersion medium in the porous membrane slurry. Can have a good swelling property. Thereby, the dispersibility of the nonconductive particles and the binder in the obtained porous film is further improved, and the cycle characteristics and output characteristics of the secondary battery using the same can be improved.

Here, the SP value is J.P. Brandrup, E .; H. Immergut and E.M. A. It can be determined according to the method described in Grulk edition “Polymer Handbook” VII Solidity Parameter Values, p675-714 (John Wiley & Sons, 4th edition, 1999). Those not described in this publication can be determined according to the “molecular attraction constant method” proposed by Small. This method is a method for obtaining the SP value (δ) according to the following equation from the characteristic value of the functional group (atomic group) constituting the compound molecule, that is, the statistics of the molecular attractive constant (G) and the molecular volume.
δ = ΣG / V = dΣG / M
ΣG: Sum of molecular attraction constant G V: Specific volume M: Molecular weight d: Specific gravity

  The iodine value of the second polymer is preferably 3 to 60 mg / 100 mg, more preferably 3 to 20 mg / 100 mg, and still more preferably 8 to 10 mg / 100 mg. When the iodine value exceeds 60 mg / 100 mg, the stability at the oxidation potential is low due to the unsaturated bond contained in the second polymer, and the high-temperature cycle characteristics of the secondary battery may be inferior. Moreover, when the iodine value is less than 3 mg / 100 mg, the flexibility of the binder may decrease due to the decrease in flexibility of the second polymer. As a result, part of the non-conductive particles may be detached due to chipping of the porous film, powder falling, or the like when the electrode is wound or pressed. When powder falling or the like occurs, the detached lump (non-conductive particles) may cause damage to the separator, a short circuit between the positive electrode and the negative electrode, and the safety and long-term characteristics may be deteriorated. When the iodine value of the second polymer is included in the above range, the second polymer is chemically structurally stable against a high potential, and the electrode structure can be maintained even in a long-term cycle. Excellent secondary battery cycle characteristics. The iodine value is determined according to JIS K 6235;

  The weight average molecular weight in terms of polystyrene by gel permeation chromatography of the second polymer used in the present invention is preferably 10,000 to 700,000, more preferably 50,000 to 500,000, particularly preferably. 100,000 to 300,000. By setting the weight average molecular weight of the second polymer within the above range, a binder having excellent binding force can be obtained, so that non-conductive particles are prevented from falling off from the porous film, and the cycle of the secondary battery The deterioration of characteristics can be suppressed. Further, the porous membrane can be made flexible, and the viscosity can be easily adjusted to be easily applied during the production of the porous membrane slurry.

  The method for producing the second polymer used in the present invention is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used. As the polymerization reaction, any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used. Examples of the polymerization initiator used for polymerization include lauroyl peroxide, diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, t-butyl peroxypivalate, 3,3,5-trimethylhexanoyl peroxide, and the like. Organic peroxides, azo compounds such as α, α′-azobisisobutyronitrile, ammonium persulfate, potassium persulfate, and the like.

  The linear alkylene polymer unit is formed by introducing a polymer unit capable of forming a conjugated diene monomer having 4 or more carbon atoms and then hydrogenating it. The method for hydrogenation reaction is not particularly limited. In the unsaturated polymer (polymer comprising a nitrile group-containing polymer unit, a hydrophilic group-containing polymer unit and a polymer unit capable of forming a conjugated diene monomer) obtained by the above polymerization method by hydrogenation reaction. Only the carbon-carbon unsaturated bond derived from the polymerized unit capable of forming the conjugated diene monomer can be selectively hydrogenated to obtain the second polymer used in the present invention. Moreover, the iodine value of the 2nd polymer used for this invention can be made into the range mentioned above by hydrogenation reaction. The second polymer used in the present invention is preferably a hydrogenated acrylonitrile-butadiene copolymer (hereinafter sometimes referred to as “hydrogenated NBR”) containing a polymer unit having a hydrophilic group.

  As a selective hydrogenation method for selectively hydrogenating only carbon-carbon unsaturated bonds derived from polymerized units capable of forming a conjugated diene monomer in an unsaturated polymer, a publicly known method may be used. Either the hydration method or the aqueous layer hydrogenation method is possible, but since the content of impurities (for example, a coagulant or metal described later) is small in the obtained second polymer, the aqueous layer hydrogenation method Is preferred.

  When the production of the second polymer used in the present invention is carried out by the oil layer hydrogenation method, it is preferably carried out by the following method. That is, first, a dispersion of an unsaturated polymer prepared by emulsion polymerization is coagulated by salting out, dissolved in an organic solvent through filtration and drying. Subsequently, the unsaturated polymer dissolved in the organic solvent is subjected to a hydrogenation reaction (oil layer hydrogenation method) to obtain a hydride, and the obtained hydride solution is coagulated, filtered and dried. The second polymer used is obtained.

  In addition, when using an alkali metal caprate as an emulsifier, in each step of coagulation, filtration and drying by salting out of the dispersion of the unsaturated polymer, in the second polymer finally obtained It is preferable to prepare such that the amount of caprate is 0.01 to 0.4% by mass. For example, a known coagulant such as magnesium sulfate, sodium chloride, calcium chloride, or aluminum sulfate can be used in coagulation by salting out of the dispersion, but preferably an alkali such as magnesium sulfate, magnesium chloride, or magnesium nitrate. By using an earth metal salt; or a Group 13 metal salt such as aluminum sulfate; the amount of caprate contained in the unsaturated polymer can be reduced. Therefore, it is preferable to use an alkaline earth metal salt or a Group 13 metal salt as the coagulant, more preferably an alkaline earth metal salt, and finally by controlling the amount of use and the solidification temperature, The amount of caprate in the second polymer obtained can be within the above range. The amount of the coagulant used is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, and particularly preferably 10 to 50 parts by mass, when the amount of unsaturated polymer to be hydrogenated is 100 parts by mass. It is. The coagulation temperature is preferably 10 to 80 ° C.

  The solvent for the oil layer hydrogenation method is not particularly limited as long as it is a liquid organic compound that dissolves the unsaturated polymer, but benzene, toluene, xylene, hexane, cyclohexane, tetrahydrofuran, methyl ethyl ketone, ethyl acetate, cyclohexanone, and acetone are preferable. used.

  As a catalyst for the oil layer hydrogenation method, any known selective hydrogenation catalyst can be used without limitation, and a palladium-based catalyst and a rhodium-based catalyst are preferable, and a palladium-based catalyst (such as palladium acetate, palladium chloride, and palladium hydroxide) is used. More preferred. Two or more of these may be used in combination, but when a rhodium catalyst and a palladium catalyst are used in combination, it is preferable to use a palladium catalyst as the main active ingredient. These catalysts are usually used by being supported on a carrier. Examples of the carrier include silica, silica-alumina, alumina, diatomaceous earth, activated carbon and the like. The amount of the catalyst used is preferably 10 to 5000 ppm, more preferably 100 to 3000 ppm, in terms of the amount of metal of the hydrogenation catalyst, relative to the amount of the unsaturated polymer to be hydrogenated.

  The hydrogenation reaction temperature in the oil layer hydrogenation method is preferably 0 to 200 ° C., more preferably 10 to 100 ° C., and the hydrogen pressure is preferably 0.1 to 30 MPa, more preferably 0.2 to 20 MPa. The reaction time is preferably 1 to 50 hours, more preferably 2 to 25 hours.

Alternatively, when the production of the second polymer used in the present invention is carried out by the aqueous layer hydrogenation method, the dispersion of the unsaturated polymer prepared by emulsion polymerization is diluted by adding water as necessary, It is preferable to perform a hydrogenation reaction.
Here, in the aqueous layer hydrogenation method, hydrogen is supplied to a reaction system in the presence of a hydrogenation catalyst to hydrogenate (I) an aqueous layer direct hydrogenation method, and in the presence of an oxidizing agent, a reducing agent and an activator. There are (II) water layer indirect hydrogenation methods in which hydrogenation is carried out by reduction.

(I) In the aqueous layer direct hydrogenation method, the concentration of the unsaturated polymer in the aqueous layer (concentration in the dispersion state) is preferably 40% by mass or less in order to prevent aggregation.
The hydrogenation catalyst used is not particularly limited as long as it is a compound that is difficult to decompose with water. As specific examples of hydrogenation catalysts, palladium catalysts include palladium salts of carboxylic acids such as formic acid, propionic acid, lauric acid, succinic acid, oleic acid and phthalic acid; palladium chloride, dichloro (cyclooctadiene) palladium, dichloro (norbornadiene) ) Palladium chloride such as palladium and ammonium hexachloropalladium (IV); Iodide such as palladium iodide; Palladium sulfate dihydrate and the like. Of these, palladium salts of carboxylic acids, dichloro (norbornadiene) palladium and ammonium hexachloropalladium (IV) are particularly preferred. The amount of the hydrogenation catalyst used may be determined as appropriate, but is preferably 5 to 6000 ppm, more preferably 10 to 4000 ppm in terms of the amount of metal of the hydrogenation catalyst with respect to the amount of the unsaturated polymer to be hydrogenated. is there.

  The reaction temperature in the aqueous layer direct hydrogenation method is preferably 0 to 300 ° C, more preferably 20 to 150 ° C, and particularly preferably 30 to 100 ° C. If the reaction temperature is too low, the reaction rate may decrease. Conversely, if the reaction temperature is too high, side reactions such as a hydrogenation reaction of a nitrile group may occur. The hydrogen pressure is preferably 0.1 to 30 MPa, more preferably 0.5 to 20 MPa. The reaction time is selected in consideration of the reaction temperature, hydrogen pressure, target hydrogenation rate, and the like.

  On the other hand, in the (II) aqueous layer indirect hydrogenation method, the concentration of the unsaturated polymer in the aqueous layer (concentration in the dispersion state) is preferably 1 to 50% by mass, more preferably 1 to 40% by mass. .

  Examples of the oxidizing agent used in the water layer indirect hydrogenation method include oxygen, air, and hydrogen peroxide. The amount of these oxidizing agents used is a molar ratio to the carbon-carbon double bond (oxidant: carbon-carbon double bond), preferably 0.1: 1 to 100: 1, more preferably 0.8: 1. It is in the range of -5: 1.

  As the reducing agent used in the aqueous layer indirect hydrogenation method, hydrazines such as hydrazine, hydrazine hydrate, hydrazine acetate, hydrazine sulfate, and hydrazine hydrochloride, or compounds that liberate hydrazine are used. The amount of these reducing agents used is a molar ratio to the carbon-carbon double bond (reducing agent: carbon-carbon double bond), preferably 0.1: 1 to 100: 1, more preferably 0.8: It is in the range of 1-5: 1.

  As the activator used in the water layer indirect hydrogenation method, ions of metals such as copper, iron, cobalt, lead, nickel, iron, tin and the like are used. These activators are used in a molar ratio to the carbon-carbon double bond (activator: carbon-carbon double bond), preferably 1: 1000 to 10: 1, more preferably 1:50 to 1: 2.

  The reaction in the aqueous layer indirect hydrogenation method is carried out by heating within the range from 0 ° C. to the reflux temperature, whereby the hydrogenation reaction is carried out. The heating range at this time is preferably 0 to 250 ° C, more preferably 20 to 100 ° C, and particularly preferably 40 to 80 ° C.

  In both the direct hydrogenation method and the indirect hydrogenation method in the aqueous layer, it is preferable to carry out solidification by salting out, filtration and drying after the hydrogenation. The salting out is carried out in order to control the amount of caprate in the second polymer after the hydrogenation reaction, similarly to the salting out of the unsaturated polymer dispersion in the oil layer hydrogenation method. It is preferable to use an earth metal salt or a Group 13 metal salt, and it is particularly preferable to use an alkaline earth metal salt. Further, the filtration and drying steps subsequent to coagulation can be performed by known methods.

  Moreover, the method for producing the second polymer used in the present invention is particularly preferably a method in which the hydrogenation reaction is carried out in two or more stages. Even when the same amount of hydrogenation catalyst is used, the hydrogenation reaction efficiency can be increased by carrying out the hydrogenation reaction in two or more stages. That is, when the polymer unit capable of forming a conjugated diene monomer is converted into a linear alkylene structural unit, the iodine value of the second polymer can be further reduced.

  When the hydrogenation reaction is performed in two or more stages, the hydrogenation reaction rate (hydrogenation ratio) (%) in the first stage should be 50% or more, more preferably 70% or more. Is preferred. That is, when the value obtained by the following formula is the hydrogenation reaction rate (%), this value is preferably 50% or more, and more preferably 70% or more.

Hydrogenation reaction rate (hydrogenation rate) (%)
= 100 × (carbon-carbon double bond amount before hydrogenation reaction−carbon-carbon double bond amount after hydrogenation reaction) / (carbon-carbon double bond amount before hydrogenation reaction)
In addition, the amount of carbon-carbon double bonds can be analyzed using NMR.

  After completion of the hydrogenation reaction, the hydrogenation reaction catalyst in the dispersion is removed. As the method, for example, an adsorbent such as activated carbon or ion exchange resin can be added to adsorb the hydrogenation reaction catalyst with stirring, and then the dispersion can be filtered or centrifuged. It is also possible to leave the hydrogenation reaction catalyst in the dispersion without removing it.

  The second polymer used in the present invention has a polymer unit having a hydrophilic group. The method for introducing a polymer unit having a hydrophilic group into the second polymer is not particularly limited, and in the above-described production process of the second polymer, the polymer constituting the second polymer is hydrophilic. Unsaturated group comprising a method of introducing a functional group (a method of copolymerizing a monomer having a hydrophilic group), a polymer unit having the above-mentioned nitrile group, and a polymer unit capable of forming the above-mentioned conjugated diene monomer A polymer obtained by hydrogenation of the polymer and subjected to a hydrogenation reaction (hereinafter sometimes referred to as “hydrogenated polymer”) is obtained, and then the hydrogenated polymer and the ethylenically unsaturated carboxylic acid or its And a method of mixing with an anhydride (method of acid-modifying a hydrogenated polymer). Among these, a method of copolymerizing a monomer having a hydrophilic group is preferable because it is simple in the process.

  In the following, the second polymer (hereinafter referred to as “acid-modified”) used in the present invention by mixing ethylenically unsaturated carboxylic acid or its anhydride with the polymer after the hydrogenation reaction (hydrogenated polymer) is mixed. The method for producing (second polymer) may be described in detail (method for acid-modifying a hydrogenated polymer).

  The ethylenically unsaturated carboxylic acid or anhydride thereof used for producing the acid-modified second polymer is not particularly limited, but the ethylenically unsaturated dicarboxylic acid having 4 to 10 carbon atoms or anhydride thereof is not limited. Products, in particular maleic anhydride, are preferred.

Examples of the ethylenically unsaturated carboxylic acid include ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid:
Ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid:
Ethylenically unsaturated dicarboxylic acid anhydrides such as maleic anhydride, itaconic anhydride and citraconic anhydride:
Monomethyl maleate, monoethyl maleate, monopropyl maleate, mono-n-butyl maleate, monoisobutyl maleate, mono-n-pentyl maleate, mono-n-hexyl maleate, mono-2-ethylhexyl maleate, Monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, mono-n-butyl fumarate, monoisobutyl fumarate, mono-n-pentyl fumarate, mono-n-hexyl fumarate, mono-2-ethylhexyl fumarate, Monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, mono-n-butyl itaconate, monoisobutyl itaconate, mono-n-pentyl itaconate, mono-n-hexyl itaconate, mono-2-ethylhexyl itaconate, Citraconate monomethyl, cyto Conethyl monoethyl, citraconic acid monopropyl, citraconic acid mono-n-butyl, citraconic acid monoisobutyl, citraconic acid mono-n-pentyl, citraconic acid mono-n-hexyl, citraconic acid mono-2-ethylhexyl, mesaconic acid monomethyl, Mesaconic acid monoethyl, mesaconic acid monopropyl, mesaconic acid mono-n-butyl, mesaconic acid monoisobutyl, mesaconic acid mono-n-pentyl, mesaconic acid mono-n-hexyl, mesaconic acid mono-2-ethylhexyl, glutaconic acid monomethyl, Monoethyl glutaconate, monopropyl glutaconate, mono-n-butyl glutaconate, monoisobutyl glutaconate, monoisobutyl glutaconate, mono-n-pentyl glutaconate, mono-n-hexyl glutaconate, mono-glutaconic acid mono- -Ethylhexyl, monomethyl allylmalonate, monoethyl allylmalonate, monopropyl allylmalonate, mono-n-butyl allylmalonate, monoisobutyl allylmalonate, mono-n-pentyl allylmalonate, mono-n-hexyl allylmalonate, mono-2 allylmalonate -Ethylhexyl, monomethyl teraconic acid, monoethyl teraconic acid, monopropyl teraconic acid, mono-n-butyl teraconic acid, monoisobutyl teraconic acid, mono-n-pentyl teraconic acid, mono-n-hexyl teraconic acid, mono-2 teraconic acid -Unsaturated dicarboxylic acid monoalkyl ester such as ethylhexyl.

  The acid-modified second polymer can be obtained, for example, by subjecting a hydrogenated polymer and an ethylenically unsaturated carboxylic acid or anhydride thereof to an ene type addition reaction.

  The ene type addition reaction usually occurs by kneading a hydrogenated polymer and an ethylenically unsaturated carboxylic acid or an anhydride thereof at a high temperature without using a radical generator. When a radical generator is used, in addition to the generation of a gel, an ethylenically unsaturated carboxylic acid or anhydride thereof and a hydrogenated polymer cause a radical type addition reaction, so that an ene type addition reaction cannot be performed.

  The amount of the ethylenically unsaturated carboxylic acid or anhydride thereof is not particularly limited, but is usually 0.05 to 10 parts by mass of the ethylenically unsaturated carboxylic acid or anhydride thereof with respect to 100 parts by mass of the hydrogenated polymer. Preferably, it is 0.2-6 mass parts.

  In an ene type addition reaction, for example, when an open type kneader such as a roll type kneader is used, molten ethylenically unsaturated carboxylic acid such as maleic anhydride or its anhydride is scattered, It may not be possible to carry out a simple addition reaction. In addition, when a continuous kneader such as a single-screw extruder, a same-direction twin-screw extruder, or a different-direction rotary twin-screw extruder is used, the second polymer staying at the outlet of the extruder is gelled. As a result, the addition reaction may not be performed efficiently, such as clogging of the die head. Further, a large amount of unreacted ethylenically unsaturated carboxylic acid or anhydride thereof may remain in the second polymer.

  In the ene type addition reaction, it is preferable to use a heated closed kneader. The heat-sealed kneader can be arbitrarily selected from batch-type heat-sealed kneaders such as a pressure kneader, Banbury mixer, Brabender, etc. Among them, a pressure kneader is preferable.

  In the above production method, first, before adding the ethylenically unsaturated carboxylic acid or its anhydride to the hydrogenated polymer by the ene-type addition reaction, a specific process is performed at a temperature at which the ene-type addition reaction does not substantially occur. Specifically, at 60 to 170 ° C., preferably 100 to 150 ° C., an ethylenically unsaturated carboxylic acid or anhydride thereof and a hydrogenated polymer are pre-kneaded, and the ethylenically unsaturated carboxylic acid or anhydride thereof is washed with water. Disperse uniformly in the addition polymer. If the pre-kneading temperature is excessively low, the hydrogenated polymer may slip in the kneader and the ethylenically unsaturated carboxylic acid or its anhydride and the hydrogenated polymer may not be sufficiently mixed. On the other hand, if the pre-kneading temperature is excessively high, the ethylenically unsaturated carboxylic acid or anhydride thereof thrown into the kneader may be scattered in a large amount, and the ene type addition reaction rate may be lowered.

  Next, in order to carry out the ene type addition reaction, the temperature of the mixture of the hydrogenated polymer and the ethylenically unsaturated carboxylic acid or its anhydride during kneading is usually kept at 200 to 280 ° C, preferably 220 to 260 ° C. The method for maintaining the temperature is not particularly limited, but is usually achieved by flowing warm water or steam through the jacket of the kneader, or using shear heat generation.

When flowing warm water or steam through the jacket of the heat-sealed kneader, the jacket temperature is usually maintained at 70 to 250 ° C, preferably 130 to 200 ° C. Moreover, when utilizing shear heat_generation | fever, it is preferable to continue kneading | mixing with a kneading machine with the shear rate of 30-1000S < ^-1 >, Preferably it is 300-700S- ¹ . In particular, the use of shear heat generation is preferable because the temperature of the mixture can be easily controlled. The kneading time in the heat-sealed kneader is not particularly limited, but is usually 120 seconds to 120 minutes, preferably 180 seconds to 60 minutes.

  If the temperature of the mixture during kneading is excessively low, the ene type addition reaction may not proceed sufficiently. Moreover, when too high, generation | occurrence | production of gelation or a burnt thing etc. will occur, and as a result, gel may mix in a product. In addition, if the shear rate is excessively high, it is difficult to control the temperature of the mixture by shearing heat generation, the temperature of the mixture becomes too high, and generation of gels and burned products occurs, which is not preferable as an industrial production method. . On the other hand, if the shear rate is excessively low, the temperature of the mixture becomes too low, so that a sufficient ene-type addition reaction cannot be expected.

  In the ene type addition reaction, an increase in gelation of the second polymer can be prevented by adding an anti-aging agent during kneading. Although the kind of anti-aging agent is not particularly limited, amine type, amine ketone type, phenol type, benzimidazole type and other anti-aging agents for binders can be used.

  Examples of amine-based antioxidants include phenyl-1-naphthylamine, alkylated diphenylamine, octylated diphenylamine, 4,4-bis (α, α-dimethylbenzyl) diphenylamine, p- (p-toluenesulfonylamide) diphenylamine, N, N-di-2-naphthyl-p-phenylenediamine, N, N-diphenyl-p-phenylenediamine, N-phenyl-N-isopropyl-p-phenylenediamine, N-phenyl-N- (1,3- And dimethylbutyl) -p-phenylenediamine and N-phenyl-N- (3-methacryloyloxy-2-hydroxypropyl) -p-phenylenediamine.

  Examples of amine ketone antioxidants include 2,2,4-trimethyl-1,2-dihydroquinoline, 6-ethoxy-1,2-dihydro-2,2,4-trimethylquinoline, and the like.

  Examples of phenolic antioxidants include 2,6-di-tert-butyl-4-methylphenol, 2,6-di-tert-butyl-4-ethylphenol, 2,2-methylenebis (4-ethyl- 6-tert-butylphenol), 2,2-methylenebis (4-methyl-6-tert-butylphenol), 4,4-butylidenebis (3-methyl-6-tert-butylphenol), 4,4-thiobis (3-methyl) -6-tert-butylphenol), 2,5-di-tert-butylhydroquinone, 2,5-di-tert-amylhydroquinone, and the like.

  Examples of the benzimidazole anti-aging agent include 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazole, metal salt of 2-mercaptomethylbenzimidazole, and the like.

  The usage-amount of these anti-aging agents is 0.01-5 mass parts normally with respect to 100 mass parts of 2nd polymers, Preferably it is 0.1-2 mass parts.

  According to the production method described above, the second amount used in the present invention is usually used by adding 80% or more of the charged amount of the ethylenically unsaturated carboxylic acid or anhydride used in the ene type addition reaction to the hydrogenated polymer. A polymer can be obtained, and unreacted ethylenically unsaturated carboxylic acid or anhydride thereof remaining in the second polymer can be reduced to 5% or less of the charged amount. Therefore, this method is extremely useful for industrially stable production. In this invention, the 2nd polymer containing 1-20 mass% of polymer units which have a hydrophilic group can be obtained with the manufacturing method mentioned above.

  The second polymer used in the present invention is obtained through a particulate metal removal step of removing particulate metal contained in the second polymer dispersion in the production step of the second polymer. It is preferable. When the content of the particulate metal component contained in the second polymer is 10 ppm or less, it is possible to prevent metal ion cross-linking over time between polymers in the porous membrane slurry described later, and to prevent an increase in viscosity. . Furthermore, there is little concern about self-discharge increase due to internal short circuit of the secondary battery or dissolution / precipitation during charging, and the cycle characteristics and safety of the battery are improved.

  The method for removing the particulate metal component from the second polymer dispersion in the particulate metal removal step is not particularly limited. For example, the removal method by filtration using a filtration filter, the removal method using a vibrating screen, or centrifugation. Examples thereof include a removal method and a removal method using magnetic force. Especially, since the removal object is a metal component, the method of removing by magnetic force is preferable. The method for removing by magnetic force is not particularly limited as long as the metal component can be removed. However, in consideration of productivity and removal efficiency, a magnetic filter is preferably arranged in the second polymer production line. Done in

  The dispersant used in the polymerization method of the first polymer and the second polymer may be one used in ordinary synthesis. Specific examples include sodium dodecylbenzenesulfonate, sodium dodecylphenylethersulfonate, and the like. Benzene sulfonates; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecyl sulfate; sulfosuccinates such as sodium dioctyl sulfosuccinate and sodium dihexyl sulfosuccinate; fatty acid salts such as sodium laurate; polyoxyethylene lauryl ether sulfate sodium Salts, ethoxy sulfate salts such as polyoxyethylene nonylphenyl ether sulfate sodium salt; alkane sulfonate salt; alkyl ether phosphate sodium salt; polyoxyethylene noni salt Nonionic emulsifiers such as phenyl ether, polyoxyethylene sorbitan lauryl ester, polyoxyethylene-polyoxypropylene block copolymer; gelatin, maleic anhydride-styrene copolymer, polyvinyl pyrrolidone, sodium polyacrylate, degree of polymerization 700 Examples thereof include water-soluble polymers such as polyvinyl alcohol having a saponification degree of 75% or more, and these may be used alone or in combination of two or more. Among these, benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecylsulfate are preferable, and oxidation resistance is more preferable. From this point, it is a benzenesulfonate such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate. The addition amount of a dispersing agent can be set arbitrarily, and is about 0.01-10 mass parts normally with respect to 100 mass parts of monomer total amounts.

  The pH when the first polymer and the second polymer are dispersed in the dispersion medium is preferably 5 to 13, more preferably 5 to 12, and most preferably 10 to 12. When the pH of the first polymer and the second polymer is in the above range, the storage stability of the binder is improved, and further, the mechanical stability is improved.

  The pH adjuster for adjusting the pH of the first polymer and the second polymer is an alkali metal hydroxide such as lithium hydroxide, sodium hydroxide or potassium hydroxide, calcium hydroxide, magnesium hydroxide, hydroxide. Alkali earth metal oxides such as barium, hydroxides such as metal hydroxides belonging to group IIIA in the long periodic table such as aluminum hydroxide; alkali metal carbonates such as sodium carbonate and potassium carbonate, magnesium carbonate, etc. Examples of organic amines include alkyl amines such as ethylamine, diethylamine, and propylamine; alcohol amines such as monomethanolamine, monoethanolamine, and monopropanolamine Ammonia such as aqueous ammonia; and the like. Among these, alkali metal hydroxides are preferable from the viewpoints of binding properties and operability, and sodium hydroxide, potassium hydroxide, and lithium hydroxide are particularly preferable.

  The binder used in the present invention comprises the first polymer and the second polymer. In the present invention, a porous film having high flexibility and binding properties can be formed by using a binder containing the first polymer and the second polymer.

  The binder is preferably contained in an amount of 0.5 to 20 parts by mass, more preferably 1 to 18 parts by mass, and particularly preferably 1.5 to 15 parts by mass with respect to 100 parts by mass of the total solid content of the porous membrane slurry. By making the content ratio of the binder within the above range, the above-mentioned non-conductive particles are prevented from detaching (powder falling) from the porous film produced using the porous film slurry of the present invention, and flexibility An excellent porous film can be obtained, and the cycle characteristics of a secondary battery using the porous film can be improved.

  The ratio of the first polymer to the second polymer in the binder is a mass ratio, preferably 5:95 to 50:50, more preferably 10:90 to 40:60, and still more preferably 10:90. ~ 30: 70. By setting the ratio of the second polymer to the first polymer within the above range, a porous film having high flexibility and binding properties can be obtained.

  The manufacturing method of the binder used for this invention is not specifically limited, It manufactures by mixing the 1st polymer dispersion liquid and 2nd polymer dispersion liquid which were mentioned above. The mixing device is not particularly limited as long as it is a device that can uniformly mix the first polymer dispersion and the second polymer dispersion. For example, a mixing device such as a stirring type, a shaking type, and a rotary type was used. A method is mentioned. In addition, a method using a dispersion kneader such as a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer, and a planetary kneader can be used.

(Dispersion medium)
As the dispersion medium used for the porous membrane slurry, either water or an organic solvent can be used. In the present invention, the dispersion medium exemplified in the first polymer can be used. These dispersion media may be used alone, or two or more of these dispersion media may be mixed and used as a mixed solvent. Among these, a dispersion medium having excellent dispersibility of non-conductive particles and having a low boiling point and high volatility is preferable because it can be removed at a low temperature in a short time. Specifically, acetone, toluene, cyclohexanone, cyclopentane, tetrahydrofuran, cyclohexane, xylene, water, N-methylpyrrolidone, or a mixed solvent thereof is preferable.

(Optional ingredients)
In addition to the above components (nonconductive particles, binder and dispersion medium), the porous membrane slurry may further contain optional components. Examples of such optional components include dispersants, leveling agents, antioxidants, binders other than the above binders, thickeners, antifoaming agents, electrolytic solution additives and reaction aids having functions such as electrolytic solution decomposition inhibition. And the like. These are not particularly limited as long as they do not affect the battery reaction.

  Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. A dispersing agent is selected according to the nonelectroconductive particle to be used. The content ratio of the dispersant per 100 parts by mass of the total solid content of the porous membrane slurry is preferably within a range that does not affect the battery characteristics, and specifically 10 parts by mass or less. When the content ratio of the dispersant is in the above range, the coating property of the porous membrane slurry of the present invention is good, and a uniform porous membrane can be obtained.

  Examples of the leveling agent include surfactants such as alkyl surfactants, silicone surfactants, fluorine surfactants, and metal surfactants. The content ratio of the surfactant per 100 parts by mass of the total solid content of the porous membrane slurry is preferably within a range that does not affect the battery characteristics, and specifically 10 parts by mass or less. By mixing the surfactant, repelling that occurs when the porous membrane slurry of the present invention is applied to a predetermined substrate can be prevented, and the smoothness of the porous membrane can be improved.

  Examples of the antioxidant include a phenol compound, a hydroquinone compound, an organic phosphorus compound, a sulfur compound, a phenylenediamine compound, and a polymer type phenol compound. The polymer type phenol compound is a polymer having a phenol structure in the molecule, and a polymer type phenol compound having a weight average molecular weight of 200 to 1000, preferably 600 to 700 is preferably used. The content ratio of the antioxidant per 100 parts by mass of the total solid content of the porous membrane slurry is preferably within a range that does not affect the battery characteristics, and specifically 10 parts by mass or less. When the content ratio of the antioxidant is within the above range, the cycle life of the battery is excellent.

  As the binder other than the binder, polyacrylic acid derivatives, polyacrylonitrile derivatives, soft polymers, and the like used for binders (electrode binders) used in electrodes described later can be used. The content ratio of the binder other than the binder per 100 parts by mass of the total solid content of the porous membrane slurry is 10 parts by mass or less. When the content ratio of the binder is within the above range, the adhesion between the porous film of the present invention and the electrode active material layer and organic separator described later is good. Moreover, it can suppress that resistance increases by inhibiting the movement of lithium ion, maintaining the softness | flexibility of a porous film.

  Examples of thickeners include cellulosic polymers such as carboxymethylcellulose, methylcellulose, hydroxypropylcellulose, and ammonium salts and alkali metal salts thereof; (modified) poly (meth) acrylic acid and ammonium salts and alkali metal salts thereof; ) Polyvinyl alcohols such as polyvinyl alcohol, copolymers of acrylic acid or acrylate and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinyl pyrrolidone, modified Examples include polyacrylic acid, oxidized starch, phosphate starch, casein, and various modified starches. The content ratio of the thickening agent per 100 parts by mass of the total solid content of the porous membrane slurry is preferably within a range that does not affect the battery characteristics, and specifically 10 parts by mass or less. When the content of the thickener is in the above range, the coating property of the porous membrane slurry of the present invention and the adhesion between the porous membrane of the present invention and the electrode active material layer and organic separator described later are good. In the present invention, “(modified) poly” means “unmodified poly” or “modified poly”, and “(meth) acryl” means “acryl” or “methacryl”.

  As the antifoaming agent, metal soaps, polysiloxanes, polyethers, higher alcohols, perfluoroalkyls and the like are used. The content ratio of the antifoaming agent per 100 parts by mass of the total solid content of the porous membrane slurry is preferably within a range that does not affect the battery characteristics, and specifically 10 parts by mass or less. By mixing an antifoaming agent, the defoaming step of the binder can be shortened.

  As the electrolytic solution additive, vinylene carbonate used in an electrode slurry and an electrolytic solution described later can be used. The content ratio of the electrolytic solution additive per 100 parts by mass of the total solid content of the porous membrane slurry is preferably within a range that does not affect the battery characteristics, and specifically 10 parts by mass or less. By mixing the electrolyte additive, the cycle life of the battery is excellent.

  Other examples include nanoparticles such as fumed silica and fumed alumina, isothiazoline compounds, chelate compounds and pyrithione compounds. By mixing nanoparticles with the porous membrane slurry, the thixotropy of the porous membrane slurry can be controlled, and the leveling property of the porous membrane obtained thereby can be improved. In addition, by containing an isothiazoline-based compound in the porous membrane slurry, it is possible to suppress the growth of fungi, thus preventing the generation of off-flavors in the porous membrane slurry for forming the porous membrane and the thickening of the slurry. And excellent long-term storage stability. In addition, by adding a chelate compound to the porous membrane slurry, transition metal ions that elute in the electrolyte during the charge / discharge of the secondary battery using the porous membrane formed by the slurry can be captured. It is possible to prevent a decrease in cycle characteristics and safety of the secondary battery due to metal ions. In addition, by including a pyrithione compound in the porous membrane slurry, the pyrithione compound is stable even if alkaline, so when used in combination with an isothiazoline-based compound, the antiseptic performance effect can be extended even under alkaline conditions, and the synergistic effect is higher. An antibacterial effect can be obtained.

  The total content of the above-mentioned optional components per 100 parts by mass of the total solid content of the porous membrane slurry is preferably 40 parts by mass or less, more preferably 20 parts by mass or less. However, when the total of the non-conductive particles, the binder, and optional components (excluding the binder) is less than 100 parts by mass, the content ratio of the binder as the optional component may be appropriately increased. .

  The solid content concentration of the porous membrane slurry is not particularly limited as long as the slurry can be applied and immersed, and has a fluid viscosity, but is generally about 10 to 50% by mass.

  Components other than the solid content are components that volatilize in the drying step, and include, in addition to the dispersion medium, for example, a medium in which these are dissolved or dispersed during preparation and addition of non-conductive particles and a binder.

  The method for producing the secondary battery porous membrane slurry is not particularly limited, and is produced by mixing the non-conductive particles, the binder, the dispersion medium, and any components added as necessary. In the present invention, the non-conductive particles are highly dispersed regardless of the mixing method and mixing order by using the above components (non-conductive particles, binder, dispersion medium and optional components added as necessary). A porous membrane slurry can be obtained. The mixing apparatus is not particularly limited as long as it can uniformly mix the above components, and includes a ball mill, a bead mill, a roll mill, a sand mill, a fill mix, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, and the like. Can be used. Among them, it is particularly preferable to use a high dispersion apparatus such as a bead mill, a roll mill, or a fill mix that can add a high dispersion share.

  The viscosity of the porous membrane slurry is preferably 10 to 10,000 mPa · s, more preferably 50 to 500 mPa · s, from the viewpoint of uniform coating properties and slurry aging stability. The viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.

[Secondary battery porous membrane]
The secondary battery porous membrane of the present invention (hereinafter sometimes referred to as “porous membrane”) is formed by forming the above-mentioned slurry composition for a secondary battery porous membrane into a film and drying it. The porous film is used by being laminated on an organic separator or an electrode, or used as an organic separator itself.

  As a method for producing the porous membrane of the present invention, (I) a porous membrane slurry containing the above non-conductive particles, a binder, the optional components and a dispersion medium is applied on a predetermined substrate (positive electrode, negative electrode or organic separator). (II) A method in which the porous film slurry is immersed in a substrate (positive electrode, negative electrode or organic separator) and then dried; (III) The porous film slurry is removed from the release film. And a method of transferring the resulting porous film onto a predetermined substrate (positive electrode, negative electrode or organic separator). Among these, (I) The method of applying the porous film slurry to the substrate (positive electrode, negative electrode or organic separator) and then drying is most preferable because the film thickness of the porous film can be easily controlled.

  The porous film of the present invention is manufactured by the above-described methods (I) to (III), and the detailed manufacturing method will be described below.

  In the method (I), the porous membrane slurry of the present invention is produced by applying a porous membrane slurry onto a predetermined substrate (positive electrode, negative electrode or organic separator) and drying.

  The method for applying the slurry onto the substrate is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. Among these, the gravure method is preferable in that a uniform porous film can be obtained.

  Examples of the drying method include drying by warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying temperature can be changed depending on the type of dispersion medium used. In order to completely remove the dispersion medium, for example, when a low-volatile solvent such as N-methylpyrrolidone is used, it is preferable to dry it at a high temperature of 80 ° C. or higher with a blower dryer. Conversely, when a highly volatile solvent is used, it can be dried at a low temperature of 80 ° C. or lower. When the porous film is formed on the organic separator described later, it is necessary to dry the organic separator without causing shrinkage. Therefore, drying at a low temperature of 80 ° C. or lower is preferable.

In the method (II), the porous membrane of the present invention is produced by immersing the porous membrane slurry in a substrate (positive electrode, negative electrode or organic separator) and drying. The method for immersing the slurry in the substrate is not particularly limited, and for example, the slurry can be immersed by dip coating with a dip coater or the like.
Examples of the drying method include the same methods as the drying method in the method (I) described above.

In the method (III), a porous film slurry is applied on a release film and formed into a film, thereby producing a porous film formed on the release film. Next, the obtained porous film is transferred onto a substrate (positive electrode, negative electrode or organic separator).
As the coating method, the same method as the coating method in the above-mentioned method (I) can be mentioned. The transfer method is not particularly limited.

  The porous film obtained by the methods (I) to (III) is then subjected to pressure treatment using a die press or a roll press, if necessary, and a substrate (positive electrode, negative electrode or organic separator) and porous film. It is also possible to improve the adhesion. However, at this time, if the pressure treatment is excessively performed, the porosity of the porous film may be impaired, so the pressure and the pressure time are controlled appropriately.

  The film thickness of the porous film is not particularly limited and is appropriately set according to the use or application field of the porous film. However, if the film is too thin, a uniform film cannot be formed. Since the capacity per volume (weight) decreases, 0.5 to 50 μm is preferable, and 0.5 to 10 μm is more preferable.

  The porous film of the present invention is formed on the surface of a substrate (positive electrode, negative electrode or organic separator) and is particularly preferably used as a protective film or separator for an electrode active material layer described later. The porous film of the present invention may be formed on any surface of the positive electrode, negative electrode or organic separator of the secondary battery, or may be formed on all of the positive electrode, negative electrode and organic separator.

[Secondary battery electrode]
Examples of the secondary battery of the present invention include a lithium ion secondary battery and a nickel hydride secondary battery. Among these, the lithium ion secondary battery is preferable because safety improvement is most demanded and the effect of introducing a porous film is the highest, and in addition, improvement of cycle characteristics is cited as a problem. The case where it uses for a battery is demonstrated.

  The secondary battery electrode of the present invention is formed by laminating a current collector, an electrode active material layer, and a porous film in this order, and the porous film is the above-described secondary battery porous film. The electrode active material layer includes an electrode active material and an electrode binder.

(Electrode active material)
The electrode active material used for the electrode for the lithium ion secondary battery is not particularly limited as long as it can reversibly insert and release lithium ions by applying a potential in the electrolyte, and can be an inorganic compound or an organic compound.

Electrode active materials (positive electrode active materials) for lithium ion secondary battery positive electrodes are broadly classified into those made of inorganic compounds and those made of organic compounds. Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, composite oxides of lithium and transition metals, and transition metal sulfides. As the transition metal, Fe, Co, Ni, Mn and the like are used. Specific examples of the inorganic compound used for the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LiFeVO _4, and other lithium-containing composite metal oxides; TiS ₂ , TiS ₃ , non- Transition metal sulfides such as crystalline MoS ₂ ; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O ₁₃ It is done. These compounds may be partially element-substituted. As the positive electrode active material made of an organic compound, for example, a conductive polymer such as polyacetylene or poly-p-phenylene can be used. An iron-based oxide having poor electrical conductivity may be used as an electrode active material covered with a carbon material by allowing a carbon source material to be present during reduction firing. These compounds may be partially element-substituted.

  The positive electrode active material for a lithium ion secondary battery may be a mixture of the above inorganic compound and organic compound. The particle diameter of the positive electrode active material is appropriately selected in consideration of the arbitrary constituent requirements of the battery. From the viewpoint of improving battery characteristics such as rate characteristics and cycle characteristics, the 50% volume cumulative diameter is usually 0.1. -50 μm, preferably 1-20 μm. When the 50% volume cumulative diameter is within this range, a secondary battery having a large charge / discharge capacity can be obtained, and handling of the slurry for electrodes and the electrodes is easy. The 50% volume cumulative diameter can be determined by measuring the particle size distribution by laser diffraction.

  Examples of electrode active materials (negative electrode active materials) for negative electrodes of lithium ion secondary batteries include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, pitch-based carbon fibers, and high conductivity such as polyacene. Examples include molecular compounds. In addition, as the negative electrode active material, metals such as silicon, tin, zinc, manganese, iron, nickel, alloys thereof, oxides or sulfates of the metals or alloys are used. In addition, lithium alloys such as lithium metal, Li—Al, Li—Bi—Cd, and Li—Sn—Cd, lithium transition metal nitride, silicone, and the like can be used. As the electrode active material, a material obtained by attaching a conductivity imparting material to the surface by a mechanical modification method can also be used. The particle size of the negative electrode active material is appropriately selected in consideration of the other structural requirements of the battery. From the viewpoint of improving battery characteristics such as initial efficiency, rate characteristics, and cycle characteristics, a 50% volume cumulative diameter is usually The thickness is 1 to 50 μm, preferably 15 to 30 μm.

(Binder for electrode)
In the present invention, the electrode active material layer includes a binder (hereinafter sometimes referred to as “electrode binder”) in addition to the electrode active material. By including a binder for the electrode, the binding property of the electrode active material layer in the electrode is improved, the strength against the mechanical force applied during the process of winding the electrode is increased, and the electrode active material in the electrode is increased. Since the material layer is less likely to be detached, the risk of a short circuit due to the desorbed material is reduced.

  Various resin components can be used as the electrode binder. For example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives, and the like can be used. These may be used alone or in combination of two or more. Moreover, the binder used for the porous film of this invention can also be used as a binder for electrodes.

Furthermore, the soft polymer illustrated below can also be used as a binder for electrodes.
Acrylic acid such as polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer Or an acrylic soft polymer, which is a homopolymer of a methacrylic acid derivative or a copolymer with a monomer copolymerizable therewith;
Isobutylene-based soft polymers such as polyisobutylene, isobutylene-isoprene rubber, isobutylene-styrene copolymer;
Polybutadiene, polyisoprene, butadiene / styrene random copolymer, isoprene / styrene random copolymer, acrylonitrile / butadiene copolymer, acrylonitrile / butadiene / styrene copolymer, butadiene / styrene / block copolymer, styrene / butadiene / Diene-based soft polymers such as styrene block copolymer, isoprene / styrene block copolymer, styrene / isoprene / styrene block copolymer;
Silicon-containing soft polymers such as dimethylpolysiloxane, diphenylpolysiloxane, dihydroxypolysiloxane;
Liquid polyethylene, polypropylene, poly-1-butene, ethylene / α-olefin copolymer, propylene / α-olefin copolymer, ethylene / propylene / diene copolymer (EPDM), ethylene / propylene / styrene copolymer, etc. Olefinic soft polymers of
Vinyl-based soft polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl stearate, vinyl acetate / styrene copolymer;
Epoxy-based soft polymers such as polyethylene oxide, polypropylene oxide, epichlorohydrin rubber;
Fluorine-containing soft polymers such as vinylidene fluoride rubber and tetrafluoroethylene-propylene rubber;
Examples thereof include other soft polymers such as natural rubber, polypeptide, protein, polyester-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, and polyamide-based thermoplastic elastomer. These soft polymers may have a cross-linked structure or may have a functional group introduced by modification.

  The amount of the electrode binder in the electrode active material layer is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 4 parts by mass, and particularly preferably 0.00 with respect to 100 parts by mass of the electrode active material. 5 to 3 parts by mass. When the amount of the electrode binder in the electrode active material layer is within the above range, it is possible to prevent the active material from being detached from the electrode without inhibiting the battery reaction.

  The electrode binder is prepared as a solution or a dispersion for producing an electrode. The viscosity at that time is usually in the range of 1 to 300,000 mPa · s, preferably 50 to 10,000 mPa · s. The viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.

(Optional additive)
In the present invention, the electrode active material layer may contain an optional additive such as a conductivity-imparting material or a reinforcing material in addition to the electrode active material and the electrode binder. As the conductivity-imparting material, conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor-grown carbon fiber, and carbon nanotube can be used. Moreover, carbon powders such as graphite, fibers and foils of various metals can be used. As the reinforcing material, various inorganic and organic spherical, plate-like, rod-like or fibrous fillers can be used. By using the conductivity imparting material, the electrical contact between the electrode active materials can be improved, and when used in a lithium ion secondary battery, the discharge rate characteristics can be improved. The usage-amount of an electroconductivity imparting material or a reinforcing material is 0-20 mass parts normally with respect to 100 mass parts of electrode active materials, Preferably it is 1-10 mass parts. Further, an isothiazoline-based compound or a chelate compound may be included in the electrode active material layer.

  The electrode active material layer can be formed by attaching a slurry containing an electrode active material, an electrode binder, and a solvent (hereinafter also referred to as “electrode slurry”) to a current collector.

  Any solvent may be used as long as it dissolves or disperses the electrode binder, but a solvent that dissolves is preferable. When a solvent that dissolves the electrode binder is used, the electrode binder is adsorbed on the surface of the electrode active material or any additive, thereby stabilizing the dispersion of the electrode active material.

  As the solvent used for the electrode slurry, either water or an organic solvent can be used. As the organic solvent, the organic solvent exemplified in the first polymer can be used.

  The electrode slurry may further contain additives that exhibit various functions such as a thickener. As the thickener, a polymer soluble in the solvent used for the electrode slurry is used. Specifically, the thickener exemplified in the porous membrane slurry of the present invention can be used. As for the usage-amount of a thickener, 0.5-1.5 mass parts is preferable with respect to 100 mass parts of electrode active materials. When the use amount of the thickener is within the above range, the coating property of the electrode slurry and the adhesion to the current collector are good.

  Furthermore, in addition to the above components, the electrode slurry contains trifluoropropylene carbonate, vinylene carbonate, catechol carbonate, 1,6-dioxaspiro [4,4] nonane-2,7 in order to increase the stability and life of the battery. -Dione, 12-crown-4-ether, etc. can be used. These may be used by being contained in an electrolyte solution described later.

  The amount of the solvent in the electrode slurry is adjusted so as to have a viscosity suitable for coating depending on the type of the electrode active material, the electrode binder and the like. Specifically, the solid content concentration of the electrode active material, the electrode binder, and the conductive additive in the electrode slurry is preferably 30 to 90% by mass, more preferably Is used by adjusting to an amount of 40 to 80% by mass.

  The electrode slurry is obtained by mixing an electrode active material, an electrode binder, an optional additive such as a conductivity imparting agent added as necessary, and a solvent using a mixer. Mixing may be performed by supplying the above components all at once to a mixer. When using electrode active materials, electrode binders, conductivity-imparting materials and thickeners as constituents of electrode slurries, conductivity is imparted by mixing the conductivity-imparting materials and thickeners in a solvent. It is preferable to disperse the material in the form of fine particles, and then add a binder for the electrode and an electrode active material and further mix, since the dispersibility of the slurry is improved. As the mixer, a ball mill, sand mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, Hobart mixer, etc. can be used. It is preferable because aggregation of the resin can be suppressed.

  The particle size of the electrode slurry is preferably 35 μm or less, more preferably 25 μm or less. When the particle size of the slurry is in the above range, the conductivity imparting material is highly dispersible and a homogeneous electrode can be obtained.

(Current collector)
The current collector is not particularly limited as long as it is an electrically conductive and electrochemically durable material. From the viewpoint of having heat resistance, for example, iron, copper, aluminum, nickel, stainless steel, etc. Metal materials such as titanium, tantalum, gold, and platinum are preferable. Among these, aluminum is particularly preferable for the positive electrode of the lithium ion secondary battery, and copper is particularly preferable for the negative electrode of the lithium ion secondary battery. The shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 to 0.5 mm is preferable. In order to increase the binding strength of the electrode active material layer, the current collector is preferably used after roughening in advance. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, an abrasive cloth paper with a fixed abrasive particle, a grindstone, an emery buff, a wire brush provided with a steel wire or the like is used. Further, an intermediate layer may be formed on the current collector surface in order to increase the binding strength and conductivity of the electrode active material layer.

  The method for producing the electrode active material layer may be any method in which the electrode active material layer is bound in layers on at least one side, preferably both sides of the current collector. For example, the electrode slurry is applied to a current collector and dried, and then heat-treated at 120 ° C. or higher for 1 hour or longer to form an electrode active material layer. The method for applying the electrode slurry to the current collector is not particularly limited. Examples thereof include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. Examples of the drying method include drying by warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams.

  Next, it is preferable to lower the porosity of the electrode active material layer by pressure treatment using a mold press or a roll press. The preferable range of the porosity is 5 to 15%, more preferably 7 to 13%. If the porosity is too high, charging efficiency and discharging efficiency are deteriorated. When the porosity is too low, it is difficult to obtain a high volume capacity, and the electrode active material layer is liable to be peeled off and a defect is likely to occur.

  The thickness of the electrode active material layer is usually 5 to 300 μm, preferably 10 to 250 μm, for both the positive electrode and the negative electrode.

  The secondary battery electrode of the present invention is manufactured by laminating the secondary battery porous film of the present invention on the surface of the electrode active material layer of the current collector in which the electrode active material layer is bound in layers.

  Although the lamination | stacking method is not specifically limited, The method of (I)-(III) demonstrated by the manufacturing method of the above-mentioned porous film is mentioned.

[Secondary battery separator]
The secondary battery separator of the present invention is formed by laminating an organic separator and a porous film, and the porous film is the above-described secondary battery porous film. That is, the secondary battery separator of the present invention is formed by laminating the above-described secondary battery porous film on the surface of the organic separator.

(Organic separator)
As an organic separator for a lithium ion secondary battery, known ones such as a polyolefin resin such as polyethylene and polypropylene and a separator containing an aromatic polyamide resin are used.

  As the organic separator used in the present invention, a porous membrane having a fine pore size, having no electron conductivity and ionic conductivity and high resistance to organic solvents is used. For example, polyolefin-based (polyethylene, polypropylene, polybutene, polychlorinated) Vinyl), and a microporous film made of a resin such as a mixture or a copolymer thereof, polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, polyimide, polyimide amide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene Examples thereof include a microporous membrane made of a resin such as the above, or a woven fabric of polyolefin fibers, a nonwoven fabric thereof, an aggregate of insulating substance particles, or the like. Among these, since the coating property of the porous membrane slurry of the present invention is excellent, the film thickness of the entire separator can be reduced and the active material ratio in the battery can be increased to increase the capacity per volume. A microporous membrane is preferred.

  The thickness of the organic separator is usually 0.5 to 40 μm, preferably 1 to 30 μm, and more preferably 1 to 10 μm. Within this range, the resistance due to the organic separator in the battery is reduced. Moreover, the workability | operativity at the time of coating the porous membrane slurry of this invention to an organic separator is good.

  In the present invention, examples of the polyolefin-based resin used as the material for the organic separator include homopolymers such as polyethylene and polypropylene, copolymers, and mixtures thereof. Examples of the polyethylene include low density, medium density, and high density polyethylene, and high density polyethylene is preferable from the viewpoint of piercing strength and mechanical strength. These polyethylenes may be mixed in two or more types for the purpose of imparting flexibility. The polymerization catalyst used for these polyethylenes is not particularly limited, and examples thereof include Ziegler-Natta catalysts, Phillips catalysts, and metallocene catalysts. From the viewpoint of achieving both mechanical strength and high permeability, the viscosity average molecular weight of polyethylene is preferably 100,000 to 12 million, more preferably 200,000 to 3 million. Examples of polypropylene include homopolymers, random copolymers, and block copolymers, and one kind or a mixture of two or more kinds can be used. The polymerization catalyst is not particularly limited, and examples thereof include Ziegler-Natta catalysts and metallocene catalysts. The stereoregularity is not particularly limited, and isotactic, syndiotactic or atactic can be used. However, it is desirable to use isotactic polypropylene because it is inexpensive. Furthermore, an appropriate amount of a polyolefin other than polyethylene or polypropylene, and an additive such as an antioxidant or a nucleating agent may be added to the polyolefin as long as the effects of the present invention are not impaired.

  As a method for producing a polyolefin-based organic separator, a publicly known one is used. For example, after forming a melt-extruded film of polypropylene and polyethylene, annealing is performed at a low temperature to grow a crystal domain, and in this state, stretching is performed. A dry method of forming a microporous film by extending the amorphous region; mixing a hydrocarbon solvent or other low molecular weight material with polypropylene or polyethylene, forming a film, and then forming a solvent or low molecular weight into the amorphous phase A wet method in which a microporous film is formed by removing the film that has started to form an island phase by using this solvent or low-molecular solvent with another volatile solvent is selected. Among these, a dry method is preferable in that a large void can be easily obtained for the purpose of reducing the resistance.

  The organic separator used in the present invention may contain any filler or fiber compound for the purpose of controlling strength, hardness, and heat shrinkage. In addition, when laminating the porous membrane of the present invention, a low molecular compound or the like may be used in advance for the purpose of improving the adhesion between the organic separator and the porous membrane or improving the liquid impregnation property by lowering the surface tension with respect to the electrolytic solution. A coating treatment with a polymer compound, an electromagnetic radiation treatment such as ultraviolet rays, or a plasma treatment such as corona discharge / plasma gas may be performed in advance. In particular, it is preferable to coat with a polymer compound containing a polar group such as a carboxylic acid group, a hydroxyl group, and a sulfonic acid group in advance from the viewpoint of high impregnation of the electrolytic solution and easy adhesion to the porous film. .

  The secondary battery separator of this invention is manufactured by laminating | stacking the secondary battery porous film of this invention on said organic separator.

  Although the lamination | stacking method is not specifically limited, The method of (I)-(III) demonstrated by the manufacturing method of the above-mentioned porous film is mentioned.

[Secondary battery]
The secondary battery of the present invention is a secondary battery including a positive electrode, a negative electrode, an organic separator, and an electrolytic solution, and the above-described secondary battery porous film is laminated on any of the positive electrode, the negative electrode, and the organic separator.

(Electrolyte)
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is used. A lithium salt is used as the supporting electrolyte. The lithium salt is not particularly _{limited, LiPF 6, LiAsF 6, LiBF} 4, LiSbF 6, LiAlCl 4, LiClO 4, CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) ₂ NLi, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable. Two or more of these may be used in combination. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

  The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, but dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate. Carbonates such as (BC) and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; Are preferably used. Moreover, you may use the liquid mixture of these solvents. Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. Since the lithium ion conductivity increases as the viscosity of the solvent used decreases, the lithium ion conductivity can be adjusted depending on the type of the solvent.

  The density | concentration of the supporting electrolyte in electrolyte solution is 1-30 mass% normally, Preferably it is 5-20 mass%. Further, it is usually used at a concentration of 0.5 to 2.5 mol / L depending on the type of the supporting electrolyte. If the concentration of the supporting electrolyte is too low or too high, the ionic conductivity tends to decrease. Since the degree of swelling of the binder increases as the concentration of the electrolytic solution used decreases, the lithium ion conductivity can be adjusted by the concentration of the electrolytic solution.

  As a specific method for producing a secondary battery, a positive electrode and a negative electrode are overlapped with an organic separator, and this is wound into a battery container according to the shape of the battery. And sealing. The porous film of the present invention is laminated on any one of the positive electrode, the negative electrode, and the organic separator. The method of laminating the porous film of the present invention on the positive electrode, the negative electrode, and the organic separator is as described in the method (I) or (II). Moreover, it is also possible to laminate | stack only a porous film on a positive electrode, a negative electrode, or an organic separator independently as the above-mentioned method of (III). If necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like can be inserted to prevent an increase in pressure inside the battery and overcharge / discharge. The shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.

  In the secondary battery of the present invention, the porous film of the present invention is preferably laminated on the surface of the positive electrode or negative electrode active material layer. By laminating the porous film of the present invention on the surface of the electrode active material layer, even if the organic separator is contracted by heat, a short circuit between the positive electrode and the negative electrode is not caused, and high safety is maintained. In addition, by laminating the porous membrane of the present invention on the surface of the electrode active material layer, the porous membrane can function as a separator without an organic separator, and a secondary battery can be produced at low cost. become. Further, even when an organic separator is used, higher rate characteristics can be expressed because the holes formed on the separator surface are not filled.

  Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the part and% in a present Example are a mass reference | standard. In the examples and comparative examples, various physical properties are evaluated as follows.

<8% NMP solution viscosity>
The 8% NMP solution viscosity of the first polymer was obtained by dissolving the first polymer in NMP so as to be an 8% solution, and against this, a B-type viscometer (RB made by Toki Sangyo Co., Ltd.) -80L), and measured based on JIS K 7117-1;

<Melting point>
The melting point of the first polymer was measured based on JIS K 7121; 1987 using a differential scanning calorimeter (DSC6220SII manufactured by Nanotechnology Co., Ltd.).

<Reliability test of secondary battery separator (organic separator with porous membrane)>
A secondary battery separator (organic separator with a porous membrane) was punched into a circle having a diameter of 19 mm, immersed in a 3% by weight methanol solution of a nonionic surfactant (manufactured by Kao Corporation; Emulgen 210P), taken out, and then air-dried. . This circular secondary battery separator is impregnated with an electrolytic solution and sandwiched between a pair of circular SUS plates (diameter 15.5 mm) to form a structure of (SUS plate) / (circular secondary battery separator) / (SUS plate). Superimposed. Here, the electrolytic solution is LiPF ₆ in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C.) at a concentration of 1 mol / liter. The solution dissolved in was used. This was enclosed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. While applying an alternating current with an amplitude of 10 mV and a frequency of 1 kHz, the temperature was raised to 200 ° C. at a rate of temperature rise of 1.6 ° C./min, and the cell resistance during this time was measured to confirm the occurrence of a short circuit. In this test, the resistance value increases due to shutdown with a temperature rise and becomes at least 1000 Ω / cm ² or more. Thereafter, it was assumed that a short circuit occurred when the voltage dropped rapidly to 10 Ω / cm ² or less. In addition, this test was performed 20 times and evaluation was performed according to the following criteria.
(Evaluation criteria)
A: Number of short-circuit occurrences 0 B: Number of short-circuit occurrences 1 C: Number of short-circuit occurrences 2 to 3 D: Number of short-circuit occurrences 4 or more

<Reliability test of secondary battery electrode (electrode with porous film)>
An organic separator (single-layer polypropylene separator, porosity 55%, thickness 25 μm) is punched into a circle with a diameter of 19 mm and immersed in a 3% by weight methanol solution of a nonionic surfactant (manufactured by Kao Corporation; Emulgen 210P). And then air-dried. On the other hand, the secondary battery electrode (electrode with porous film) to be measured was punched into a circle having a diameter of 19 mm. These are impregnated with an electrolytic solution, and these are overlapped and sandwiched between a pair of circular SUS plates (diameter 15.5 mm), and (SUS plate) / (circular organic separator) / (circular secondary battery electrode) / ( SUS plate). The circular secondary battery electrode was arranged such that the surface on the porous membrane side was the organic separator side. Here, the electrolytic solution is LiPF ₆ in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C.) at a concentration of 1 mol / liter. The solution dissolved in was used. This was enclosed in a 2032 type coin cell. I took the lead from the coin cell, put a thermocouple, and put it in the oven. While applying an alternating current with an amplitude of 10 mV and a frequency of 1 kHz, the temperature was raised to 200 ° C. at a rate of temperature rise of 1.6 ° C./min, and the cell resistance during this time was measured to confirm the occurrence of a short circuit. In this test, the resistance value rises due to shutdown with a temperature rise and becomes at least 1000 Ω / cm ² or more. Thereafter, it was assumed that a short circuit occurred when the voltage dropped rapidly to 10 Ω / cm ² or less. In addition, this test was performed 20 times and evaluation was performed according to the following criteria.
(Evaluation criteria)
A: Number of short-circuit occurrences 0 B: Number of short-circuit occurrences 1 to 2 C: Number of short-circuit occurrences 3 or more

<Flexibility and powderability of porous film>
A secondary battery electrode (electrode with a porous film) or a secondary battery separator (organic separator with a porous film) is cut into a rectangle having a width of 1 cm and a length of 5 cm to obtain a test piece. Place the test piece on the desk with the surface opposite the porous membrane side down, and lay a stainless steel rod with a diameter of 1 mm on the opposite side of the center in the length direction (2.5 cm at the end) and the porous membrane side in the short direction. Install. The test piece is bent 180 degrees around the stainless steel bar so that the porous membrane layer is on the outside. Ten test pieces are tested, and the bent portions of the porous film layer of each test piece are observed for cracks or powder fall off, and determined according to the following criteria. It shows that the porous film formed on the electrode active material layer or the organic separator is more excellent in flexibility and powder-off property as the number of cracks and powder-off is smaller.
(Evaluation criteria)
A: Cracks and powder fall are not observed in all 10 sheets.
B: Cracks or powder fall is seen in 1-3 sheets out of 10 sheets.
C: Cracking or powder falling is observed on 4 to 6 of 10 sheets.
D: Cracking or powder falling is observed on 7 to 9 of 10 sheets.
E: Cracking or powder falling is observed in all 10 sheets.

<Output characteristics>
A 10-cell secondary battery is charged to 4.2 V by a constant current method of 0.1 C, and then discharged to 3.0 V at 0.1 C to obtain a 0.1 C discharge capacity. Thereafter, the battery is charged to 4.2 V at 0.1 C and then discharged to 3.0 V at 10 C to obtain a 10 C discharge capacity. The average value of 10 cells is a measured value (0.1C discharge capacity a, 10C discharge capacity b), and is expressed as a ratio of electric capacity between 10C discharge capacity b and 0.1C discharge capacity a (b / a (%)). Capacity retention ratio is obtained, and this is used as an evaluation criterion for output characteristics, and is evaluated according to the following criteria. Higher values indicate better output characteristics, that is, lower internal resistance.
(Evaluation criteria)
A: 50% or more B: 30% or more and less than 50% C: 10% or more and less than 30% D: 1% or more and less than 10% E: Less than 1%

Example 1
[(1) Production of first polymer]
As the first polymer, polyvinylidene fluoride (Kynar 741 manufactured by Arkema Co.) was used to obtain an NMP solution (solid content concentration 8%) of the first polymer.

[(2) Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion exchange water, 2.5 parts of sodium alkylbenzene sulfonate, 20 parts of acrylonitrile, 30 parts of butyl acrylate and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 45 parts of 1,3-butadiene was injected, 0.25 part of ammonium persulfate was added, and the polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a polymer unit having a nitrile group, a (meth) acrylic acid ester polymer unit, and a hydrophilic group. A polymer comprising a polymer unit having a polymer unit and a polymer unit capable of forming a conjugated diene monomer was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  A 400 milliliter (total solid content 48 grams) solution prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was added for 10 minutes. After removing the dissolved oxygen in the polymer by flowing, 75 mg of palladium acetate as a hydrogenation reaction catalyst was dissolved in 180 ml of water to which nitric acid of 4 times moles of Pd had been added and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product, which was analyzed by NMR. 20% by mass of a polymer unit (acrylonitrile monomer unit) having 45% by weight, 45% by mass of a monomer unit derived from 1,3-butadiene, and a polymer unit (methacrylic acid monomer) having a hydrophilic group (carboxylic acid group) Unit) and 5% by mass of (meth) acrylic acid ester polymerized unit (butyl acrylate monomer unit). Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 10 mg / 100 mg.

[(3) Production of binder]
In the NMP solution of the first polymer and the NMP solution of the second polymer, the mass ratio of the first polymer and the second polymer in the binder is 20:80. The mixture was stirred with a primary mixer to prepare a binder NMP solution.

[(4) Production of porous membrane slurry]
Alumina particles as non-conductive particles (Alumina AKP-3000 manufactured by Sumitomo Chemical Co., Ltd., average particle size: 0.5 μm) and the NMP solution of the binder obtained above in a weight ratio corresponding to the solid content are 100: It mixed so that it might become 2.5, and also NMP was mixed so that solid content concentration might be 40%, and it disperse | distributed using the bead mill, and prepared the porous membrane slurry.

[(5) Production of positive electrode]
To 95 parts of lithium manganate having a spinel structure as a positive electrode active material, PVDF (polyvinylidene fluoride, manufactured by Kureha Chemical Co., Ltd., trade name: KF-1100) as an electrode binder is 3 parts in terms of solid content. In addition, 2 parts of acetylene black and 20 parts of N-methylpyrrolidone were added and mixed with a planetary mixer to obtain a slurry-like electrode composition for positive electrode (positive electrode slurry). This positive electrode slurry was applied to one side of an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll pressed to obtain a positive electrode having a positive electrode active material layer having a total thickness of 100 μm.

[(6) Production of negative electrode]
Solid content of 98 parts of graphite having a particle diameter of 20 μm as a negative electrode active material and a specific surface area of 4.2 m ² / g and SBR (styrene-butadiene rubber, glass transition temperature: −10 ° C.) as a binder for electrodes 1 part is mixed, 1.0 part of carboxymethylcellulose is further mixed with this mixture, water is further added as a solvent, and these are mixed with a planetary mixer to form a slurry-like negative electrode composition (for negative electrode) Slurry) was prepared. This negative electrode slurry was applied to one side of a 18 μm thick copper foil, dried at 120 ° C. for 3 hours, and then roll-pressed to obtain a negative electrode having a total thickness of 60 μm and having a negative electrode active material layer.

[(7) Production of secondary battery separator (organic separator with porous membrane)]
A single-layer polypropylene separator (porosity 55%, thickness 25 μm) produced by a dry method was prepared as an organic separator. On one surface of this organic separator, the porous membrane slurry obtained in step (4) is applied using a wire bar so that the thickness of the porous membrane layer after drying is 5 μm to obtain a slurry layer. Was dried at 80 ° C. for 10 minutes to form a porous film. Subsequently, a porous film was similarly formed on the other surface of the organic separator, and an organic separator with a porous film having a porous film on both surfaces was obtained.

[(8) Production of Secondary Battery Having Secondary Battery Separator (Organic Separator with Porous Film)]
The positive electrode obtained in the step (5) was cut into a circle having a diameter of 13 mm to obtain a circular positive electrode. The negative electrode obtained in step (6) was cut into a circle having a diameter of 14 mm to obtain a circular negative electrode. Moreover, the organic separator with a porous membrane obtained in the step (7) was cut out into a circle having a diameter of 18 mm to obtain a circular organic separator with a porous membrane.
A circular positive electrode is placed on the inner bottom of a stainless steel coin-type outer container provided with polypropylene packing, a circular organic separator with a porous film is placed on it, and a circular negative electrode is placed thereon. They were placed and stored in a container. The circular positive electrode was placed so that the surface on the aluminum foil side faced toward the bottom surface side of the outer container and the surface on the positive electrode active material layer side faced upward. The circular negative electrode was placed so that the surface on the negative electrode active material layer side faced toward the organic separator with a circular porous film and the surface on the copper foil side faced upward.
Inject the electrolyte into the container so that no air remains, fix the outer container with a 0.2 mm thick stainless steel cap through a polypropylene packing, seal the battery can, and 20 mm in diameter. A lithium ion secondary battery (coin cell CR2032) having a thickness of about 3.2 mm was manufactured. As an electrolytic solution, LiPF ₆ is mixed at a concentration of 1 mol / liter in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C.). The dissolved solution was used.

[(9) Evaluation]
The reliability of the obtained organic separator with a porous membrane, the flexibility and powder fallenability of the porous membrane, and the output characteristics of the obtained secondary battery were evaluated. The results are shown in Table 1.

(Example 2)
As the first polymer used in step (1) of Example 1, polyvinylidene fluoride (Kynar HSV900 manufactured by Arkema Co., Ltd.) was used to obtain an NMP solution (solid content concentration 8%) of the first polymer. Except for the above, the same operation as in Example 1 was performed to obtain a porous membrane slurry, an organic separator with a porous membrane, and a secondary battery, and evaluated. The results are shown in Table 1.

(Example 3)
As the first polymer used in step (1) of Example 1, polyvinylidene fluoride (KF polymer # 7200 manufactured by Kureha Co., Ltd.) was used to obtain an NMP solution (solid content concentration 8%) of the first polymer. Except that, the same operations as in Example 1 were performed to obtain a porous membrane slurry, an organic separator with a porous membrane, and a secondary battery, and evaluated. The results are shown in Table 1.

Example 4
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 30 parts of acrylonitrile, 40 parts of butyl acrylate and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 25 parts of 1,3-butadiene was injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a polymer unit having a nitrile group, a (meth) acrylate polymer unit, a hydrophilic group. A polymer comprising a polymer unit having a polymer unit and a polymer unit capable of forming a conjugated diene monomer was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  400 ml (total solid content 48 grams) of an aqueous dispersion prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was supplied. After flowing for 10 minutes to remove dissolved oxygen in the polymer, as a hydrogenation reaction catalyst, 75 mg of palladium acetate was dissolved in 180 ml of water added with 4-fold molar nitric acid with respect to Pd and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product and analyzed by NMR. As a result, the second polymer was found to have a nitrile group based on the total amount of the polymer. 30% by mass of a polymer unit (acrylonitrile monomer unit) containing 25% by mass of a monomer unit derived from 1,3-butadiene, and a polymer unit (methacrylic acid monomer) having a hydrophilic group (carboxylic acid group) Unit) and 5% by weight of (meth) acrylic acid ester polymerized unit (butyl acrylate monomer unit). Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 5.6 mg / 100 mg.

(Example 5)
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzene sulfonate, 20 parts of acrylonitrile, 33 parts of butyl acrylate and 2 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 45 parts of 1,3-butadiene was injected, 0.25 part of ammonium persulfate was added, and the polymerization reaction was carried out at a reaction temperature of 40 ° C. to obtain a polymer unit having a nitrile group, a (meth) acrylic acid ester polymer unit, and a hydrophilic group. A polymer comprising a polymer unit having a polymer unit and a polymer unit capable of forming a conjugated diene monomer was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  400 ml (total solid content 48 grams) of an aqueous dispersion prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was supplied. After flowing for 10 minutes to remove dissolved oxygen in the polymer, as a hydrogenation reaction catalyst, 75 mg of palladium acetate was dissolved in 180 ml of water added with 4-fold molar nitric acid with respect to Pd and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product and analyzed by NMR. As a result, the second polymer was found to have a nitrile group based on the total amount of the polymer. 20% by mass of a polymer unit (acrylonitrile monomer unit) having 45% by weight, 45% by mass of a monomer unit derived from 1,3-butadiene, and a polymer unit (methacrylic acid monomer) having a hydrophilic group (carboxylic acid group) Unit) and 2% by mass of (meth) acrylic acid ester polymerized unit (butyl acrylate monomer unit). Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 10 mg / 100 mg.

(Example 6)
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 20 parts of acrylonitrile, 34.5 parts of butyl acrylate and 0.5 part of methacrylic acid are placed in this order, and the bottle is filled with nitrogen. After the substitution, 45 parts of 1,3-butadiene was injected, 0.25 part of ammonium persulfate was added and polymerized at a reaction temperature of 40 ° C., and a polymer unit having a nitrile group, a (meth) acrylic acid ester polymer unit, A polymer comprising a polymer unit having a hydrophilic group and a polymer unit capable of forming a conjugated diene monomer was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  400 ml (total solid content 48 grams) of an aqueous dispersion prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was supplied. After flowing for 10 minutes to remove dissolved oxygen in the polymer, as a hydrogenation reaction catalyst, 75 mg of palladium acetate was dissolved in 180 ml of water added with 4-fold molar nitric acid with respect to Pd and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product and analyzed by NMR. As a result, the second polymer was found to have a nitrile group based on the total amount of the polymer. 20% by mass of a polymer unit (acrylonitrile monomer unit) having 45% by weight, 45% by mass of a monomer unit derived from 1,3-butadiene, and a polymer unit (methacrylic acid monomer) having a hydrophilic group (carboxylic acid group) Unit) and 0.5% by mass of (meth) acrylic acid ester polymerized unit (butyl acrylate monomer unit). Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 10 mg / 100 mg.

(Example 7)
In the production of the binder in the step (3) of Example 1, the NMP solution of the first polymer and the NMP solution of the second polymer are combined with the first polymer and the second polymer in the binder. Except that the NMP solution of the binder was adjusted by stirring in the primary mixer so that the ratio was 8:92 in terms of mass ratio, the same operation as in Example 1 was performed, and the porous membrane slurry, porous An organic separator with a membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Example 8)
In the production of the binder in the step (3) of Example 1, the NMP solution of the first polymer and the NMP solution of the second polymer are combined with the first polymer and the second polymer in the binder. Except that the NMP solution of the binder was adjusted by stirring with a primary mixer so that the ratio was 30:70 in terms of mass ratio, the same operation as in Example 1 was performed, and the porous membrane slurry, porous An organic separator with a membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

Example 9
In the production of the binder in the step (3) of Example 1, the NMP solution of the first polymer and the NMP solution of the second polymer are combined with the first polymer and the second polymer in the binder. Except that the NMP solution of the binder was adjusted by stirring in the primary mixer so that the ratio was 40:60 by mass ratio, the same operation as in Example 1 was performed, and the porous membrane slurry, porous An organic separator with a membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Example 10)
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 20 parts of acrylonitrile, 20 parts of butyl acrylate and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. Inject 55 parts of 1,3-butadiene, add 0.25 part of ammonium persulfate, and cause a polymerization reaction at a reaction temperature of 40 ° C. to obtain a polymer unit having a nitrile group, a (meth) acrylate polymer unit, a hydrophilic group. A polymer comprising a polymer unit having a polymer unit and a polymer unit capable of forming a conjugated diene monomer was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  400 ml (total solid content 48 grams) of an aqueous dispersion prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was supplied. After flowing for 10 minutes to remove dissolved oxygen in the polymer, as a hydrogenation reaction catalyst, 75 mg of palladium acetate was dissolved in 180 ml of water added with 4-fold molar nitric acid with respect to Pd and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product, which was analyzed by NMR. 20% by mass of a polymer unit (acrylonitrile monomer unit) having a monomer content, 55% by mass of a monomer unit derived from 1,3-butadiene, and a polymer unit (methacrylic acid monomer) having a hydrophilic group (carboxylic acid group) Unit) and 5% by mass of (meth) acrylic acid ester polymerized unit (butyl acrylate monomer unit). Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 12 mg / 100 mg.

(Example 11)
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzenesulfonate, 15 parts of acrylonitrile, 10 parts of butyl acrylate and 5 parts of methacrylic acid were put in this order, and the inside of the bottle was replaced with nitrogen. 70 parts of 1,3-butadiene was injected, 0.25 part of ammonium persulfate was added, and a polymerization reaction was carried out at a reaction temperature of 40 ° C., and a polymer unit having a nitrile group, a (meth) acrylic acid ester polymer unit, and a hydrophilic group were added. A polymer comprising a polymer unit having a polymer unit and a polymer unit capable of forming a conjugated diene monomer was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  400 ml (total solid content 48 grams) of an aqueous dispersion prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was supplied. After flowing for 10 minutes to remove dissolved oxygen in the polymer, as a hydrogenation reaction catalyst, 75 mg of palladium acetate was dissolved in 180 ml of water added with 4-fold molar nitric acid with respect to Pd and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product, which was analyzed by NMR. 15% by mass of a polymer unit (acrylonitrile monomer unit) having a monomer, 70% by mass of a monomer unit derived from 1,3-butadiene, and a polymer unit (methacrylic acid monomer) having a hydrophilic group (carboxylic acid group) Unit) and 5% by weight of (meth) acrylic acid ester polymerized unit (butyl acrylate monomer unit). Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 15.6 mg / 100 mg.

(Example 12)
In the production of the binder in the step (3) of Example 1, the NMP solution of the first polymer and the NMP solution of the second polymer are combined with the first polymer and the second polymer in the binder. Except that the NMP solution of the binder was adjusted by stirring in the primary mixer so that the ratio was 60:40 in mass ratio, the same operation as in Example 1 was performed, and the porous membrane slurry, porous An organic separator with a membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Example 13)
In the production of the binder in the step (3) of Example 1, the NMP solution of the first polymer and the NMP solution of the second polymer are combined with the first polymer and the second polymer in the binder. Except that the NMP solution of the binder was adjusted by stirring with a primary mixer so that the ratio was 80:20 in terms of mass ratio, the same operation as in Example 1 was performed, and the porous membrane slurry, porous An organic separator with a membrane and a secondary battery were obtained and evaluated. The results are shown in Table 1.

(Example 14)
Instead of the nonconductive particles used in step (4) of Example 1, the following nonconductive particles were used, and instead of the porous film slurry obtained in step (4), the porous film obtained below Except having used the slurry, operation similar to Example 1 was performed, the organic separator with a porous membrane, and a secondary battery were obtained, and evaluation was performed. The results are shown in Table 1.

[Production of non-conductive particles]
In a reactor equipped with a stirrer, 0.06 part of sodium dodecyl sulfate, 0.23 part of ammonium persulfate and 100 parts of ion-exchanged water were added and mixed to obtain a mixture A, which was heated to 80 ° C.
On the other hand, 93.8 parts of butyl acrylate, 2.0 parts of methacrylic acid, 2.0 parts of acrylonitrile, 1.0 part of allyl glycidyl ether, 1.2 parts of N-methylol acrylamide, sodium dodecyl sulfate 0. 1 part and 100 parts of ion-exchanged water were mixed to prepare a dispersion of the monomer mixture B.
The dispersion of the monomer mixture B was continuously added and polymerized in the mixture A obtained above over 4 hours. During the continuous addition of the dispersion of the monomer mixture B, the temperature of the reaction system was maintained at 80 ° C. to carry out the reaction. After completion of the continuous addition, the reaction was further continued at 90 ° C. for 3 hours.
Thereby, an aqueous dispersion of seed polymer particles having an average particle diameter of 370 nm was obtained.

Next, in a reactor equipped with a stirrer, 20 parts of the above-mentioned aqueous dispersion of seed polymer particles based on the solid content (that is, based on the weight of the seed polymer particles) and ethylene glycol dimethacrylate as a monomer (Kyoeisha Chemical Co., Ltd.) Company, product name: 100 parts of light ester EG, 1.0 part of sodium dodecylbenzenesulfonate, t-butylperoxy-2-ethylhexanoate (manufactured by NOF Corporation, trade name: perbutyl) as a polymerization initiator 4.0 parts of O) and 200 parts of ion-exchanged water were added and stirred at 35 ° C. for 12 hours to completely absorb the monomer and the polymerization initiator in the seed polymer particles.
This was polymerized at 90 ° C. for 5 hours. Thereafter, steam was introduced to remove unreacted monomers and initiator decomposition products. Thereby, an aqueous dispersion of non-conductive particles having an average particle diameter of 670 nm was obtained. After adding 80 parts of NMP to 100 parts of an aqueous dispersion of non-conductive particles (solid content concentration is 20%) and mixing well, the water in the system is completely removed under reduced pressure at 90 ° C. to obtain non-conductive particles NMP dispersion (solid content concentration 20%) was obtained.

[Production of porous membrane slurry]
The NMP dispersion of non-conductive particles obtained above and the NMP solution of the binder used in Example 1 were mixed so that the weight ratio corresponding to the solid content was 27: 2.5. NMP was mixed so that the partial concentration was 40%, and dispersed using a bead mill to prepare a porous membrane slurry.

(Example 15)
[Manufacture of negative electrode with porous film]
The porous membrane slurry obtained in Example 14 was completely covered with the porous membrane slurry obtained in Example 14 on the negative electrode active material layer side surface of the negative electrode obtained in Step (6) of Example 1, and the porous membrane after drying The slurry layer was obtained by coating so as to have a thickness of 5 μm. The slurry layer was dried at 110 ° C. for 10 minutes to form a porous film, and a negative electrode with a porous film was obtained. The obtained negative electrode with a porous film had a layer structure of (porous film) / (negative electrode active material layer) / (copper foil). The reliability of the obtained negative electrode with a porous film, and the softness | flexibility and powder fall-off property of the porous film were evaluated. The results are shown in Table 1.

  Instead of the organic separator with a porous film obtained in the step (7) of Example 1, an organic separator (single layer polypropylene separator, porosity 55%, thickness 25 μm, organic in the step (7) of Example 1 The same as that used as a separator) was used.

  Moreover, except having used the said negative electrode with a porous film instead of the negative electrode obtained at the process (6) of Example 1, operation similar to Example 1 was performed, the secondary battery was obtained, and evaluation was carried out. went. The results are shown in Table 1. In placing the negative electrode with a circular porous film in the outer container, the negative electrode was placed so that the porous film side faced to the circular organic separator side and the copper foil side faced to the upper side.

(Example 16)
Instead of the non-conductive particles used in the step (4) of Example 1, plate-like alumina particles (SERATH manufactured by Kinsei Matech, average particle size: 0.6 μm) were used as the non-conductive particles. The same operations as in Example 1 were performed to obtain a porous membrane slurry, an organic separator with a porous membrane, and a secondary battery, and evaluated. The results are shown in Table 1.

(Example 17)
[Manufacture of negative electrode with porous film]
On the negative electrode active material layer side surface of the negative electrode obtained in the step (6) of Example 1, the negative electrode active material layer is completely covered with the porous membrane slurry obtained in the step (4) of Example 1, The slurry was applied so that the porous film thickness after drying was 5 μm. The slurry layer was dried at 110 ° C. for 10 minutes to form a porous film, and a negative electrode with a porous film was obtained. The obtained negative electrode with a porous film had a layer structure of (porous film) / (negative electrode active material layer) / (copper foil). The reliability of the obtained negative electrode with a porous film, and the softness | flexibility and powder fall-off property of the porous film were evaluated. The results are shown in Table 1.

  Instead of the organic separator with a porous film obtained in the step (7) of Example 1, an organic separator (single layer polypropylene separator, porosity 55%, thickness 25 μm, organic in the step (7) of Example 1 The same as that used as a separator) was used.

  Moreover, except having used the said negative electrode with a porous film instead of the negative electrode obtained at the process (6) of Example 1, operation similar to Example 1 was performed, the secondary battery was obtained, and evaluation was carried out. went. The results are shown in Table 1. In placing the negative electrode with a circular porous film in the outer container, the negative electrode was placed so that the porous film side faced to the circular organic separator side and the copper foil side faced to the upper side.

(Comparative Example 1)
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
To polymerization can A, 10 parts of butyl acrylate, 2.5 parts of acrylonitrile, 0.12 part of sodium lauryl sulfate and 79 parts of ion-exchanged water are added, and 0.2 part of ammonium persulfate and 10 parts of ion-exchanged water are added as a polymerization initiator. After heating to 60 ° C. and stirring for 90 minutes, 65 parts of butyl acrylate, 17.5 parts of acrylonitrile, 5 parts of methacrylic acid, 0.7 part of sodium lauryl sulfate, and 46 parts of ion exchange water were added to another polymerization vessel B. The emulsion prepared by stirring was sequentially added from the polymerization vessel B to the polymerization vessel A over about 180 minutes, and then stirred for about 120 minutes to cool the monomer consumption amount to 95% to complete the reaction. The pH was adjusted with a 4% NaOH aqueous solution to obtain an aqueous dispersion of the polymer.

  To 100 parts of this second polymer aqueous dispersion, 320 parts of NMP was added and water was evaporated under reduced pressure, but could not be dissolved in NMP. 100 g of the aqueous dispersion was coagulated with 1 liter of methanol, and then vacuum dried at 60 ° C. overnight to obtain a dried product, which was analyzed by NMR. The second polymer had a total amount of Polymer unit having nitrile group (acrylonitrile monomer unit) 20% by mass, polymer unit having hydrophilic group (carboxylic acid group) (methacrylic acid monomer unit) 5% by mass, (meth) acrylic acid ester polymerization It contained 75% by mass of units (butyl acrylate monomer units). The iodine value of the second polymer was 1 mg / 100 mg or less.

(Comparative Example 2)
Except that the first polymer was not used and the second polymer of Comparative Example 1 was used as a binder, the same operation as in Example 1 was performed to obtain a porous membrane slurry, an organic separator with a porous membrane, and a secondary membrane. A battery was obtained and evaluated. The results are shown in Table 1.

(Comparative Example 3)
Except that the following second polymer was used instead of the second polymer obtained in the step (2) of Example 1, the same operation as in Example 1 was performed to obtain a porous membrane slurry, An organic separator with a porous film and a secondary battery were obtained and evaluated. The results are shown in Table 1.

[Production of second polymer]
In an autoclave equipped with a stirrer, 240 parts of ion-exchanged water, 2.5 parts of sodium alkylbenzene sulfonate, 20 parts of acrylonitrile and 35 parts of butyl acrylate were put in this order, and the inside of the bottle was replaced with nitrogen. 45 parts are injected, 0.25 part of ammonium persulfate is added and polymerized at a reaction temperature of 40 ° C. to form a polymer unit having a nitrile group, a (meth) acrylate polymer unit, and a conjugated diene monomer. A polymer comprising was obtained. The polymerization conversion was 85%, and the iodine value was 280 mg / 100 mg.

  400 ml (total solid content 48 grams) of an aqueous dispersion prepared by adjusting the total solid content of the polymer to 12% by mass with water was charged into a 1 liter autoclave equipped with a stirrer, and nitrogen gas was supplied. After flowing for 10 minutes to remove dissolved oxygen in the polymer, as a hydrogenation reaction catalyst, 75 mg of palladium acetate was dissolved in 180 ml of water added with 4-fold molar nitric acid with respect to Pd and added. After the inside of the system was replaced twice with hydrogen gas, the autoclave contents were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “first-stage hydrogenation reaction”) for 6 hours. ) At this time, the iodine value of the polymer was 35 mg / 100 mg.

  Next, the autoclave was returned to atmospheric pressure, and further, 25 mg of palladium acetate was dissolved in 60 ml of water added with 4 times moles of nitric acid with respect to Pd as a hydrogenation reaction catalyst. After the inside of the system was replaced twice with hydrogen gas, the contents of the autoclave were heated to 50 ° C. while being pressurized with hydrogen gas up to 3 MPa, and the hydrogenation reaction (referred to as “second stage hydrogenation reaction”) was performed for 6 hours. )

  Thereafter, the contents were returned to room temperature, the inside of the system was made into a nitrogen atmosphere, and then concentrated using an evaporator until the solid content concentration became 40% to obtain a second polymer aqueous dispersion. Further, 320 parts of NMP was added to 100 parts of the second aqueous polymer dispersion, and water was evaporated under reduced pressure to obtain an NMP solution of the second polymer. After 100 g of the NMP solution was coagulated with 1 liter of methanol, it was vacuum-dried overnight at 60 ° C. to obtain a dried product and analyzed by NMR. As a result, the second polymer was found to have a nitrile group based on the total amount of the polymer. 20% by mass of polymerized units (acrylonitrile monomer units) having 45% by mass of monomer units derived from 1,3-butadiene, 35% by weight of (meth) acrylate polymerized units (butyl acrylate monomer units) % Included. Further, it was confirmed by the hydrogenation reaction that the monomer unit derived from 1,3-butadiene contains a linear alkylene polymer unit having 4 or more carbon atoms. The iodine value of the second polymer was 10 mg / 100 mg.

(Comparative Example 4)
Except that the second polymer was not used and the first polymer of Example 1 was used as a binder, the same operation as in Example 1 was performed to obtain a porous membrane slurry, an organic separator with a porous membrane, and a secondary membrane. A battery was obtained and evaluated. The results are shown in Table 1.

(Comparative Example 5)
[Manufacture of negative electrode with porous film]
The porous membrane slurry obtained in Comparative Example 3 was completely covered with the porous membrane slurry obtained in Comparative Example 3 on the negative electrode active material layer side surface of the negative electrode obtained in Step (6) of Example 1, and the porous membrane after drying The slurry layer was obtained by coating so as to have a thickness of 5 μm. The slurry layer was dried at 110 ° C. for 10 minutes to form a porous film, and a negative electrode with a porous film was obtained. The obtained negative electrode with a porous film had a layer structure of (porous film) / (negative electrode active material layer) / (copper foil). The reliability of the obtained negative electrode with a porous film, and the softness | flexibility and powder fall-off property of the porous film were evaluated. The results are shown in Table 1.

  Instead of the organic separator with a porous film obtained in the step (7) of Example 1, an organic separator (single layer polypropylene separator, porosity 55%, thickness 25 μm, organic in the step (7) of Example 1 The same as that used as a separator) was used.

  Moreover, except having used the said negative electrode with a porous film instead of the negative electrode obtained at the process (6) of Example 1, operation similar to Example 1 was performed, the secondary battery was obtained, and evaluation was carried out. went. The results are shown in Table 1. In placing the negative electrode with a circular porous film in the outer container, the negative electrode was placed so that the porous film side faced to the circular organic separator side and the copper foil side faced to the upper side.

From the results in Table 1, the following can be said.
The porous membrane slurry of Examples 1 to 17, the porous membrane formed using the porous membrane slurry, the secondary battery electrode and secondary battery separator on which the porous membrane is laminated, and the secondary battery having the porous membrane are as follows: , The balance of each evaluation is excellent.

Claims (8)

A non-conductive particle, a binder comprising a first polymer and a second polymer, and a dispersion medium,
The first polymer is a fluorine-containing polymer;
For the secondary battery porous membrane, the second polymer is a polymer comprising a polymer unit having a nitrile group, a polymer unit having a hydrophilic group, and a linear alkylene polymer unit having 4 or more carbon atoms. Slurry composition.   2. The slurry composition for a secondary battery porous film according to claim 1, wherein the ratio of the first polymer to the second polymer in the binder is 5:95 to 50:50 in mass ratio.   The first polymer is at least one selected from polyvinylidene fluoride, polytetrafluoroethylene, vinylidene fluoride-hexafluoropropylene copolymer, polyvinyl fluoride, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The slurry composition for a secondary battery porous membrane according to claim 1 or 2.   The slurry composition for a secondary battery porous membrane according to any one of claims 1 to 3, wherein the second polymer comprises (meth) acrylic acid ester polymerized units.   The secondary battery porous film formed by forming the slurry composition for secondary battery porous films in any one of Claims 1-4 in the shape of a film, and drying.   A current collector, an electrode active material layer, and a porous film are laminated in this order, and the porous film is the secondary battery porous film according to claim 5.   An organic separator and a porous membrane are laminated, and the porous membrane is the secondary battery porous membrane according to claim 5. A secondary battery including a positive electrode, a negative electrode, an organic separator, and an electrolyte solution,
A secondary battery in which the secondary battery porous film according to claim 5 is laminated on any one of the positive electrode, the negative electrode, and the organic separator.