JPWO2013147006A1 - Porous membrane for secondary battery, porous membrane slurry for secondary battery, non-conductive particle, electrode for secondary battery, separator for secondary battery, and secondary battery - Google Patents

Abstract

To provide a porous membrane for a secondary battery having high uniformity in film thickness, excellent reliability in a high temperature environment, and excellent ion permeability. A porous membrane for a secondary battery containing non-conductive particles and a binder, wherein the non-conductive fine particles have a number average particle size of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m 2 /. A porous film for a secondary battery, characterized in that the polymer particle is g. [Selection figure] None

Description

  The present invention relates to a porous film for a secondary battery, a porous film slurry for a secondary battery, non-conductive particles, an electrode for a secondary battery, a separator for a secondary battery, and a secondary battery.

  Electrochemical elements such as lithium ion secondary batteries that are small and lightweight, have high energy density, and can be repeatedly charged and discharged are rapidly expanding their demands by taking advantage of their characteristics. Lithium ion secondary batteries are used in fields such as mobile phones, notebook personal computers, and electric vehicles because of their relatively high energy density.

  In such a lithium ion secondary battery, a separator is usually used in order to prevent a short circuit between the positive electrode and the negative electrode. As such a separator, a separator made of a polyolefin-based material such as polyethylene or polypropylene and having physical properties that melts at 200 ° C. or lower is generally used. For this reason, when the lithium ion secondary battery becomes hot, the separator may cause a volume change such as shrinkage or melting. When such a volume change occurs, a short circuit between the positive electrode and the negative electrode, It will cause the release of energy.

  In order to solve such a problem, for example, Patent Documents 1 and 2 propose a technique of providing a porous film containing nonconductive particles such as inorganic fine particles on the separator surface or the electrode surface. In these Patent Documents 1 and 2, by using inorganic fine particles, it is possible to form a porous film having excellent heat resistance and high strength. However, the preparation of inorganic fine particles inevitably contains moisture and metal ions, and therefore it is difficult to reduce the contents of moisture and metal ions. In particular, when moisture and metal ions are mixed in the porous film, the battery performance is adversely affected, so that further improvement of the battery performance by the inorganic fine particles is limited.

  On the other hand, Patent Documents 3 and 4 propose using organic fine particles instead of inorganic fine particles. Since the surface of the organic fine particles can be hydrophobized by selecting the monomer species to be used, it is possible to reduce the moisture mixed into the porous film as compared with the inorganic fine particles. In addition, since it is possible to produce metal ions free, the amount of metal ions mixed can be reduced. Therefore, further improvement in battery performance can be expected by using organic fine particles.

  However, a porous film containing organic fine particles has a low strength and a low performance to prevent a short circuit of a battery in a high temperature use environment, and a uniform thickness distribution and strength distribution. There is a problem that it is difficult. In particular, if the distribution of film thickness and strength is not uniform, partial cracks are likely to occur, thereby reducing the performance of the battery. In addition, the porous film containing organic fine particles has a problem that the ion permeability is lowered due to the influence of the organic fine particles.

JP 2007-294437 A JP 2005-327680 A JP 2006-139978 A JP 2009-64566 A

  An object of the present invention is to provide a porous membrane for a secondary battery having high uniformity in film thickness, excellent reliability in a high temperature environment, and excellent ion permeability. The present invention also provides a secondary battery porous membrane slurry and non-conductive particles for producing such a secondary battery porous membrane, and a secondary battery comprising such a secondary battery porous membrane. It is another object of the present invention to provide a battery electrode, a secondary battery separator, and a secondary battery.

As a result of intensive studies to achieve the above object, the present inventors have found that the number average particle diameter is 100 to 1000 nm and the BET specific surface area is 14.4 as non-conductive particles for forming a porous membrane for a secondary battery. The inventors have found that the above object can be achieved by using polymer particles having a molecular weight of 56 to 72.8 m ² / g, and have completed the present invention.

That is, according to the present invention, a porous membrane for a secondary battery containing non-conductive particles and a binder, wherein the non-conductive fine particles have a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to There is provided a porous membrane for a secondary battery, characterized in that the polymer particle is 72.8 m ² / g.
In the porous membrane for a secondary battery of the present invention, the binder is a (meth) acrylic polymer or a polymer containing a nitrile group, and the (meth) acrylic polymer in the porous membrane for a secondary battery. Or it is preferable that the content rate of the polymer containing a nitrile group is 3 to 20 weight%.

Further, according to the present invention, there is provided a porous membrane slurry for a secondary battery containing non-conductive particles, a binder and a dispersion medium, wherein the non-conductive fine particles have a number average particle size of 100 to 1000 nm and a BET specific surface area. A porous membrane slurry for a secondary battery, characterized in that the polymer particles are 14.56 to 72.8 m ² / g.
In the porous membrane slurry for a secondary battery of the present invention, the binder is a (meth) acrylic polymer or a polymer containing a nitrile group, and in the solid content contained in the porous membrane slurry for a secondary battery. The content ratio of the (meth) acrylic polymer or the polymer containing a nitrile group is preferably 3 to 20% by weight.

Alternatively, according to the present invention, the porous membrane for a secondary battery is characterized by comprising polymer particles having a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m ² / g. Of non-conductive particles.

Furthermore, according to the present invention, an electrode for a secondary battery comprising a current collector, an electrode active material layer, and the porous film for a secondary battery according to any one of the above laminated in this order. ,
A separator for a secondary battery, wherein the separator is formed by laminating an organic separator and the porous film for a secondary battery according to any one of the above, and
A secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte solution, wherein at least one of the positive electrode, the negative electrode, and the separator includes the porous membrane for a secondary battery according to any one of the above. Secondary battery,
Is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the porous film for secondary batteries excellent in the uniformity of a film thickness, the high temperature short circuit-proof characteristic (reliability in a high temperature environment), and the ion permeability can be provided. Further, according to the present invention, a secondary battery porous membrane slurry and non-conductive particles for producing such a secondary battery porous membrane, and a secondary battery equipped with such a secondary battery porous membrane are provided. A battery electrode, a secondary battery separator, and a secondary battery can be provided.

The porous membrane for a secondary battery of the present invention includes nonconductive particles and a binder, and the nonconductive fine particles have a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m ² / g. It is characterized by comprising polymer particles that are

(Non-conductive particles)
The non-conductive particles used in the present invention are composed of polymer particles having a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m ² / g.

  According to the present invention, the non-conductive particles constituting the porous film are those having a number average particle diameter and a BET specific surface area in the above ranges, whereby the secondary battery porous film has a uniform film thickness. It is high and can be excellent in high temperature short circuit resistance (reliability in a high temperature environment) and ion permeability. In particular, according to the present invention, by setting the number average particle diameter of the non-conductive particles in the above range, the non-conductive particles have such a degree that the conductive particles have contact portions and the movement of ions is not inhibited. A gap between each other can be formed, thereby improving the high temperature short circuit resistance (reliability in a high temperature environment) while keeping the strength of the porous film high. In addition, according to the present invention, by setting the BET specific surface area of the non-conductive particles in the above range, the water permeability of the non-conductive particles is reduced and the ion permeability in the case of the porous film is improved. Can be made. The reason why the ion permeability can be improved by setting the BET specific surface area of the non-conductive particles in the above range is not necessarily clear, but by setting the BET specific surface area in the above range, the non-conductive particle is non-conductive. The particles have a hollow structure and a structure having a large number of pores connecting the surface of the particles to the hollow portions formed in the particles. It is considered that it is possible to enter through the hollow portion and further through the pore. That is, when ions pass through the pores and hollow portions formed in the non-conductive particles, ion conduction is also performed in the non-conductive particles, thereby improving the ion permeability. Therefore, in the present invention, the BET specific surface area of the non-conductive particles includes not only the surface area of the non-conductive particles but also the surface area caused by the pores and hollow portions formed in the non-conductive particles. Will be included.

  The number average particle diameter of the non-conductive particles is 100 to 1000 nm, preferably 300 to 900 nm, more preferably 500 to 900 nm. If the number average particle diameter of the nonconductive particles is too small, the contact portions between the nonconductive particles may be reduced, and the thickness of the porous film may be nonuniform. For this reason, the strength of the porous film is insufficient, and a short circuit of the battery is likely to occur. As a result, the high temperature short circuit resistance (reliability in a high temperature environment) is deteriorated. On the other hand, if the number average particle size is too large, the gaps between the non-conductive particles are reduced, the ion permeability is lowered, and the rate characteristics are lowered when used in a secondary battery. The number average particle diameter of the non-conductive particles is determined by, for example, observing 100 non-conductive particles with a scanning electron microscope, the longest side of the particle image is a, the shortest side is b, and (a + b ) / 2 is calculated for each particle to determine the particle diameter of each particle, and is calculated as an arithmetic average value of the determined particle diameters.

The non-conductive particles used in the present invention have a BET specific surface area of 14.56 to 72.8 m ² / g, preferably 14.56 to 36.4 m ² / g, and more preferably 14.56 to 29.12 m ² / g. If the BET specific surface area is too large, the non-conductive particles become highly hygroscopic, the water content of the non-conductive particles increases, and the cycle characteristics deteriorate when used in a secondary battery. End up. On the other hand, if the BET specific surface area is too small, formation of hollow portions and pores for ions to pass through becomes insufficient, ion permeability decreases, and rate characteristics decrease when used for secondary batteries. .

  The non-conductive particles used in the present invention may have a number average particle diameter and a BET specific surface area in the above ranges, but the average circularity and the coefficient of variation in particle diameter are preferably in the following ranges.

  That is, the average circularity is preferably 1.05 to 1.60, more preferably 1.07 to 1.45, and still more preferably 1.09 to 1.35. The variation coefficient of the particle size is preferably 26% or less, more preferably 23% or less, and still more preferably 20% or less.

The average circularity is an index indicating how close the observed particle shape is to a circular shape. For the average circularity, an image obtained by enlarging the non-conductive particles with an electron microscope is taken for the non-conductive particles, 100 particles are arbitrarily selected from the taken images, and the same projected area as the particle image is obtained. When the perimeter of the circle is L ₀ and the perimeter of the particle image is L, L ₀ / L is circularity, and the average circularity can be calculated from the average of the circularity of 100 particles. Moreover, the variation coefficient of the particle diameter can be obtained from, for example, the number average particle diameter of the nonconductive particles and the standard deviation thereof.

  In the present invention, by setting the average circularity and the coefficient of variation of the particle size of the non-conductive particles in the above ranges, the non-conductive particles have a relatively uniform particle size and are more spherical. It is possible to maintain a non-spherical shape, thereby ensuring a contact area between the particles while making the shape of the non-conductive particles relatively uniform. In this case, the film thickness uniformity, strength, and ion permeability can be further improved.

  As a method for preparing the non-conductive particles used in the present invention, a method in which polymer particles having a number average particle diameter and a BET specific surface area within the above ranges may be employed. The monomer mixture containing the above polymerizable monomer is polymerized to obtain seed particles, and the obtained seed particles are used to form hollow portions and pores (between the particle surface and the hollow portion). Can be produced by carrying out a hollow portion forming process for forming the pores.

  The polymerizable monomer used for producing the seed particles is not particularly limited, but contains at least a polar group from the viewpoint that the adhesion with the binder and the strength of the obtained porous film can be improved. It is preferable to use a monomer. The polar group-containing monomer is not particularly limited as long as it contains a polar group in the molecular structure and can be polymerized alone or can be copolymerized with other monomers. Examples of the polar group-containing monomer include a monomer containing a carboxyl group, a monomer containing a sulfonic acid group, a monomer containing a hydroxyl group, a monomer containing an amide group, and a cationic monomer. Monomer, monomer containing cyano group, monomer containing epoxy group and salts thereof (for example, alkali metal salts such as sodium salt and potassium salt, alkaline earth metal salts such as calcium salt and magnesium salt) And organic amine salts such as ammonium salt, monoethanolamine salt, and triethanolamine salt).

Examples of the monomer containing a carboxyl group include monocarboxylic acid, dicarboxylic acid, dicarboxylic acid anhydride, and dicarboxylic acid monoester.
As monocarboxylic acids, acrylic acid, methacrylic acid, crotonic acid, 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid , Β-diaminoacrylic acid and the like.
Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid, methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, and fluoromaleic acid.
Examples of the acid anhydride of dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
Dicarboxylic acid monoesters include fumaric acid such as monomethyl maleate, monoethyl maleate, monopropyl maleate, mono n-butyl maleate, monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, mono n-butyl fumarate Examples thereof include monoalkyl esters, monomethyl citraconic acid, monoethyl citraconic acid, monopropyl citraconic acid, mono n-butyl citraconic acid, monomethyl itaconate, monoethyl itaconate, monopropyl itaconate, mono n-butyl itaconate and the like.

  Examples of the monomer containing 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-acrylamide-2- Examples include methylpropane sulfonic acid and 3-allyloxy-2-hydroxypropane sulfonic acid.

Examples of the monomer containing 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- Ethylene such as 2-hydroxypropyl, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, di-2-hydroxyethyl maleate, di-4-hydroxybutyl maleate, di-2-hydroxypropyl itaconate alkanol esters of sexual unsaturated carboxylic acids; formula ^{_{CH 2 = CR 1 -COO- (C}} n H 2n O) m -H (m is 2-9 integer, n represents an integer from 2 to 4, ^{R 1} is Ester of polyalkylene glycol represented by (representing hydrogen or methyl group) and (meth) acrylic acid; 2-hydroxyethyl Mono (meth) acrylates of dihydroxy esters of dicarboxylic acids such as -2 '-(meth) acryloyloxyphthalate, 2-hydroxyethyl-2'-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl ether, 2 -Vinyl ethers such as hydroxypropyl vinyl ether; (meth) allyl-2-hydroxyethyl ether, (meth) allyl-2-hydroxypropyl ether, (meth) allyl-3-hydroxypropyl ether, (meth) allyl-2-hydroxy Mono (meth) allyl ethers of alkylene glycols such as butyl ether, (meth) allyl-3-hydroxybutyl ether, (meth) allyl-4-hydroxybutyl ether, (meth) allyl-6-hydroxyhexyl ether; Polyoxyalkylene glycol (meth) monoallyl ethers such as ethylene 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 halogen and hydroxy-substituted products of (poly) alkylene glycol, such as hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; polyhydric phenols such as eugenol, isoeugenol (Meth) allyl thioether of alkylene glycol such as (meth) allyl-2-hydroxyethyl thioether and (meth) allyl-2-hydroxypropyl thioether Le acids; and the like.

  Examples of the monomer containing an amide group include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide and the like.

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

  Examples of the monomer containing a cyano group include vinyl cyanide compounds such as acrylonitrile and methacrylonitrile.

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

  Among these polar group-containing monomers, a monomer containing a carboxyl group, a monomer containing an amide group, a monomer containing a cyano group, and a monomer containing an epoxy group are preferable.

  The blending ratio of the polar group-containing monomer in the monomer mixture used for producing seed particles is preferably 0.05 to 20% by weight, more preferably 0.05 to 15% by weight, Preferably it is 0.05 to 10 weight%. By setting the blending ratio of the polar group-containing monomer in such a range, the resulting porous film can have excellent strength while making the adhesiveness with the binder good.

  The blending ratio of the monomer containing a carboxyl group as the polar group-containing monomer is preferably 0 to 10% by weight, more preferably 0.1 to 5% by weight, and the monomer containing an amide group. The blending ratio of the monomer is preferably 0 to 5% by weight, more preferably 0.05 to 5% by weight, and the blending ratio of the monomer containing a cyano group is preferably 0 to 10% by weight. More preferably, the blending ratio of the monomer containing an epoxy group is preferably 0 to 10% by weight, and more preferably 0.01 to 5% by weight. By setting the blending ratio of these monomers in such a range, the adhesiveness with the binder and the strength of the obtained porous film can be further increased.

  In addition to the polar group-containing monomer described above, other monomers that can be copolymerized with the polar group-containing monomer may be used as the polymerizable monomer used for producing the seed particles. preferable. Although it does not specifically limit as another monomer, The non-crosslinkable monomer which does not have crosslinkability can be used preferably.

Examples of such non-crosslinkable monomers include aromatic monovinyl compounds such as styrene, α-methylstyrene, fluorostyrene, and vinylpyridine; methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, Acrylic acid ester monomers such as n-dodecyl acrylate, methoxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate; methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacryl Methacrylic acid ester monomers such as n-dodecyl acid, methoxyethyl methacrylate and 2-hydroxyethyl methacrylate; conjugated double bond compounds such as butadiene and isoprene; vinyl ester compounds such as vinyl acetate; 4-methyl-1 Such as α- olefin compounds such as pentene.
Among these, acrylic ester monomers and methacrylic ester monomers are preferable, and acrylic ester monomers are more preferable.

  The blending ratio of the non-crosslinkable monomer in the monomer mixture used for producing seed particles is preferably 80 to 99.95% by weight, more preferably 85 to 99.95% by weight, More preferably, it is 90-99.95 weight%. By setting the blending ratio of the non-crosslinkable monomer in such a range, it is possible to make the obtained porous film have excellent strength while improving the adhesiveness with the binder.

  The seed particles can be produced by polymerizing a monomer mixture containing the above-described polymerizable monomer by emulsion polymerization. In this case, the seed particles can be obtained as a water dispersion. . In emulsion polymerization, commonly used polymerization auxiliary materials such as emulsifiers, polymerization initiators, molecular weight regulators and the like can be used. The conditions for the emulsion polymerization are not particularly limited, but may be set such that the number average particle diameter after the hollow portion forming treatment described later is in the above-described range.

  And about a seed particle obtained in this way, a nonelectroconductive particle can be obtained by performing a hollow part formation process so that a BET specific surface area may become the said range. A method for performing the hollow portion forming treatment is not particularly limited. For example, (1) a seed monomer is prepared by adding a crosslinkable monomer and an organic solvent together with a crosslinking agent to an aqueous dispersion of seed particles. (2) A method of removing a non-crosslinked component and an organic solvent with steam or the like after absorbing a crosslinkable monomer, an organic solvent and a crosslinking agent, A mixed solution containing a body, a crosslinking agent and water is prepared, seed particles are added to the prepared mixed solution, then a crosslinking reaction is performed, and after alkali swelling using an alkaline aqueous solution, heating is performed. Examples thereof include a method for removing uncrosslinked components.

  In the method of (1) above, by controlling the reaction conditions, the resulting particles after the cross-linking reaction have many cross-linked components on the surface, while there are uncross-linked components inside the particles. A core-shell structure in which many remain can be obtained. Then, by removing the uncrosslinked component and the organic solvent, the core portion is removed in the core portion, and a hollow structure is formed in the particles. On the other hand, in the shell portion, pores are formed by removing the organic solvent swollen in the shell portion.

  Also in the method (2), as in the method (1), by controlling the reaction conditions, the resulting particles after the cross-linking reaction have many components cross-linked on the surface, In addition, a core-shell structure in which many uncrosslinked components remain in the interior of the particle can be obtained. And by removing an uncrosslinked component with an alkali, in a core part, a core part is removed and a hollow structure will be formed in particle | grains. On the other hand, in the shell part, pores are formed by removing the component swollen in the shell part.

Although it does not specifically limit as a crosslinkable monomer used in the method of said (1), For example, a diacrylate compound, a triacrylate compound, a tetraacrylate compound, a dimethacrylate compound, a trimethacrylate compound etc. are mentioned.
Diacrylate compounds include polyethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,6-hexane glycol diacrylate, neopentyl glycol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acrylic). Roxypropyloxyphenyl) propane, 2,2′-bis (4-acryloxydiethoxyphenyl) propane and the like.
Examples of the triacrylate compound include trimethylolpropane triacrylate, trimethylolethane triacrylate, and tetramethylolmethane triacrylate.
Examples of the tetraacrylate compound include tetramethylolmethane tetraacrylate.
Dimethacrylate compounds include ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexane glycol. Examples include dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, and 2,2′-bis (4-methacryloxydiethoxyphenyl) propane.
Examples of the trimethacrylate compound include trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate.

  The blending amount of the crosslinkable monomer is preferably 100 to 10,000 parts by weight, more preferably 500 to 8,000 parts by weight with respect to 100 parts by weight of the seed particles. By setting the blending amount of the crosslinkable monomer in such a range, the size of the hollow portion formed in the obtained polymer particles can be made appropriate.

  The organic solvent used in the method (1) is not particularly limited as long as it can sufficiently swell the seed particles. For example, aliphatic hydrocarbons such as hexane; ethylbenzene, xylene, toluene, benzene Aromatic hydrocarbons such as carbon tetrachloride, halogenated hydrocarbons such as trichloroethylene and dichloromethane; Alcohols such as amyl alcohol, butyl alcohol, cyclohexyl alcohol and benzyl alcohol; Phenols such as cresol; Ethers such as diethyl ether; Ketones such as diisobutyl ketone, methyl isobutyl ketone, methyl isopropyl ketone, methyl ethyl ketone, cyclohexanone; amyl acetate, butyl acetate, propyl acetate, ethyl acetate, methyl acetate, Saturated carboxylic acid esters such as chill propionate; and the like.

  The blending amount of the organic solvent is preferably 13 to 40 parts by weight, more preferably 14 to 40 parts by weight with respect to 100 parts by weight of the crosslinkable monomer. By setting the blending amount of the organic solvent in such a range, the size and amount of the pores formed in the obtained polymer particles can be made appropriate.

  Moreover, as a crosslinking agent used in the method (1), persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis ( 2-methyl-N- (2-hydroxyethyl) propionamide), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), and 2 Azo compounds such as 2,2'-azobisisobutyronitrile; di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-hexylperoxy-2-ethylbuta Noate, diisopropyl peroxydicarbonate, di-t-butylperoxyisophthalate, t-butylperoxyisobutylate Organic peroxides such as bets and the like.

  The blending amount of the crosslinking agent is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 7 parts by weight with respect to 100 parts by weight of the crosslinkable monomer. By making the compounding quantity of a crosslinking agent into such a range, the magnitude | size of the hollow part formed in the polymer particle obtained can be made appropriate.

  In the method (1), first, a treatment for allowing the seed particles to absorb the crosslinkable monomer, the organic solvent, and the crosslinking agent is performed. The method for absorbing the crosslinkable monomer, the organic solvent and the crosslinking agent in the seed particles is not particularly limited, but the crosslinkable monomer and the organic solvent are mixed with the crosslinking agent in the aqueous dispersion of the seed particles. A method of adding them, preferably stirring them at 50 to 90 ° C. under the conditions of 1 to 10 hours, and the like can be mentioned. In this case, a known emulsifier (surfactant) may be added.

  Next, in the method (1), the crosslinking reaction is performed after the crosslinkable monomer, the organic solvent, and the crosslinking agent are absorbed by the seed particles. The conditions for the crosslinking reaction are not particularly limited, and may be appropriately set according to the type and amount of the crosslinking agent to be used. The crosslinking temperature is preferably 50 to 90 ° C., and the crosslinking time is preferably 1 to 5 hours. It is.

  In the method (1), non-conductive particles can be obtained by removing uncrosslinked components and organic solvent from the particles after the crosslinking reaction. Examples of the method for removing the uncrosslinked component and the organic solvent include a method in which steam is passed through an aqueous dispersion of non-conductive particles in a tank (steam aeration method), and an aqueous system in which non-conductive particles are used in a multistage tower. Examples include a so-called steam stripping method in which the dispersion and steam are brought into countercurrent contact. In particular, the multistage stripper method in which the aqueous dispersion is allowed to flow down from the top of the multistage tower and steam is blown from the bottom of the tower can efficiently remove uncrosslinked components and organic solvents. In the present invention, in addition to these methods, for example, uncrosslinked components and organic solvents can be removed by distillation under reduced pressure.

  Further, as the crosslinkable monomer used in the method (2), the same monomer as in the above (1) can be used, and the blending amount thereof is preferably 100 with respect to 100 parts by weight of the seed particles. -10,000 parts by weight, more preferably 500-8,000 parts by weight. By setting the blending amount of the crosslinkable monomer in such a range, the size of the hollow portion formed in the obtained polymer particles can be made appropriate.

  Similarly, as the crosslinking agent used in the method (2), the same as the above (1) can be used, and the blending amount thereof is preferably 100 parts by weight of the crosslinkable monomer. 0.1 to 10 parts by weight, more preferably 0.2 to 7 parts by weight. By making the compounding quantity of a crosslinking agent into such a range, the magnitude | size of the hollow part formed in the polymer particle obtained can be made appropriate.

  In the method (2), first, a mixed solution containing a crosslinkable monomer, a crosslinking agent, and water is prepared, seed particles are added to the prepared mixed solution, and a crosslinking reaction is performed. The conditions for the crosslinking reaction are not particularly limited, and may be appropriately set according to the type and amount of the crosslinking agent to be used. The crosslinking temperature is preferably 50 to 90 ° C., and the crosslinking time is preferably 1 to 10 hours. It is. In this case, a known emulsifier (surfactant) may be added.

  Next, in the method (2), the particles after the crosslinking reaction are subjected to an alkali swelling treatment using an alkaline aqueous solution. Specifically, the particles after the cross-linking reaction are alkali swollen by dispersing them in an alkali solution so that the solid content is preferably 5 to 40% by weight. In addition, as aqueous alkali solution, sodium hydroxide aqueous solution etc. can be used, for example. Then, after the alkali is swollen, the uncrosslinked components are removed from the particles after the crosslinking reaction by heating preferably at 25 to 90 ° C. for 1 to 5 hours, and then cooled to room temperature. Thus, non-conductive particles can be obtained.

  The content ratio of the nonconductive particles in the porous membrane for a secondary battery of the present invention is preferably 70 to 97% by weight, more preferably 80 to 95% by weight. By making the content rate of a nonelectroconductive particle into such a range, the obtained porous film can have high intensity | strength, preventing the short circuit between electrodes.

(Binder)
As the binder used in the present invention, various binders can be used as long as they have binding properties. However, in the present invention, the obtained porous film has excellent non-conductive particle retention and flexibility. In addition, a (meth) acrylic polymer or a polymer containing a nitrile group is preferable because it is easy to obtain a battery that is stable in redox and has excellent life characteristics.

  The (meth) acrylic polymer used in the present invention is a polymer containing polymerized units of an acrylate ester and / or a methacrylate ester monomer. “(Meth) acrylic polymer” means “acrylic polymer and / or methacrylic polymer”, and the same applies to (meth) acrylic acid ester monomers and the like.

  Examples of acrylic acid ester and / or methacrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2 -Acrylic acid alkyl esters such as 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 methacrylate Over DOO, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n- tetradecyl methacrylate, methacrylic acid alkyl esters such as stearyl methacrylate. Among these, non-carbonyl oxygen is shown because it exhibits lithium ion conductivity by moderate swelling into the electrolyte without eluting into the electrolyte, and in addition, it is difficult to cause bridging aggregation by the polymer in the dispersion of the active material. Preferred are heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, and lauryl acrylate, which are alkyl acrylates having 7 to 13 carbon atoms in the alkyl group bonded to the atom, and bonded to a non-carbonyl oxygen atom. More preferred are octyl acrylate, 2-ethylhexyl acrylate, and nonyl acrylate having 8 to 10 carbon atoms in the alkyl group.

  The content ratio of the polymer units of the (meth) acrylic acid ester monomer in the (meth) acrylic polymer is preferably 50 to 98% by weight, more preferably 60 to 97.5% by weight, particularly preferably 70 to 95% by weight. is there.

Moreover, it is preferable that the (meth) acrylic polymer used by this invention contains the polymerization unit of another arbitrary monomer in addition to the polymerization unit of a (meth) acrylic acid ester monomer.
Examples of the polymerization unit of an arbitrary monomer include a polymerization unit of a vinyl monomer having an acidic group, a polymerization unit of a monomer having a crosslinkable group, and the like.

Examples of the vinyl monomer having an acidic group include a monomer having a carboxylic acid group, a monomer having a hydroxyl group, a monomer having a sulfonic acid group, a monomer having a —PO ₃ H ₂ group, and —PO (OH ) (OR) group (R represents a hydrocarbon group) and a monomer having a lower polyoxyalkylene group. Moreover, the acid anhydride which produces | generates a carboxylic acid group by a hydrolysis can be used similarly.

Examples of the monomer having a carboxylic acid group include monocarboxylic acid, dicarboxylic acid, dicarboxylic acid anhydride, and derivatives thereof. As monocarboxylic acids, acrylic acid, methacrylic acid, crotonic acid, 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid , Β-diaminoacrylic acid and the like. Dicarboxylic acids include maleic acid, fumaric acid, itaconic acid, methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, methylallyl maleate, diphenyl maleate, nonyl maleate, And maleate esters such as decyl maleate, dodecyl maleate, octadecyl maleate and fluoroalkyl maleate. Examples of the acid anhydride of dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
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- (CnH}} 2 nO) m-H (m is 2 to 9 integer, n represents 2 to 4 integer, ^{R 1} is hydrogen or methyl An ester of a polyalkylene glycol represented by a group and (meth) acrylic acid; Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as til-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 ether of alkylene glycol 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 halogen and hydroxy-substituted products of (poly) alkylene glycol, such as hydroxypropyl ether, (meth) allyl-2-hydroxy-3-chloropropyl ether; polyhydric phenols 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 -Tels; and the like.

  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.

As a monomer having a —PO ₃ H ₂ group and / or —PO (OH) (OR) group (R represents a hydrocarbon group), 2- (meth) acryloyloxyethyl phosphate, methyl phosphate -2- (meth) acryloyloxyethyl, ethyl phosphate- (meth) acryloyloxyethyl, and the like.

  Examples of the monomer having a lower polyoxyalkylene group include poly (alkylene oxide) such as poly (ethylene oxide).

  Among these, a monomer having a carboxylic acid group is preferable from the viewpoint that the binding force can be further increased, and among them, a monocarboxylic acid having 5 or less carbon atoms having a carboxylic acid group such as acrylic acid and methacrylic acid, and the like. Dicarboxylic acids having 5 or less carbon atoms having two carboxylic acid groups per molecule such as maleic acid and itaconic acid are preferred.

  The content ratio of the polymer units of the vinyl monomer having an acidic group in the (meth) acrylic polymer is preferably 1.0 to 3.0% by weight, more preferably 1.5 to 2.5% by weight.

Monomers having a crosslinkable group include a crosslinkable group, a monofunctional monomer having one olefinic double bond per molecule, and a polyfunctional having two or more olefinic double bonds per molecule. Monomer.
The crosslinkable group contained in the monofunctional monomer having a crosslinkable group and one olefinic double bond per molecule is selected from the group consisting of an epoxy group, an N-methylolamide group, an oxetanyl group, and an oxazoline group. At least one selected from the above is preferable, and an epoxy group is more preferable in terms of easy crosslinking and adjustment of the crosslinking density.

Examples of the monomer containing an epoxy group contained in the monomer having a crosslinkable 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. It is done.
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 Glycidyl esters of unsaturated carboxylic acids such as rubetate, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid; It is done.
Examples of the monomer having a halogen atom and an epoxy group include epihalohydrin such as epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, β-methylepichlorohydrin; p-chlorostyrene oxide; dibromo Phenyl glycidyl ether;

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

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

  Polyfunctional monomers having two or more olefinic double bonds per molecule include allyl acrylate or allyl methacrylate, trimethylolpropane-triacrylate, trimethylolpropane-methacrylate, dipropylene glycol diallyl ether, polyglycol diallyl Ethers, triethylene glycol divinyl ether, hydroquinone diallyl ether, tetraallyloxyethane, or other allyl or vinyl ethers of polyfunctional alcohols, tetraethylene glycol diacrylate, triallylamine, trimethylolpropane-diallyl ether, methylenebisacrylamide and / or Or divinylbenzene is preferable. In particular, allyl acrylate, allyl methacrylate, trimethylolpropane-triacrylate and / or trimethylolpropane-methacrylate and the like can be mentioned.

  Among these, since the crosslinking density is easily improved, a polyfunctional monomer having two or more olefinic double bonds per molecule is preferable, and further, the crosslinking density is improved and the copolymerization property is high. For this reason, acrylates or methacrylates having an allyl group such as allyl acrylate or allyl methacrylate are preferred.

  In the (meth) acrylic polymer used in the present invention, the content of the polymer units of the monomer having a crosslinkable group is preferably 0.01 to 2.0% by weight, more preferably 0.05 to 1.5% by weight. %, Particularly preferably in the range of 0.1 to 1.0% by weight. By making the content ratio of the polymerized units of the monomer having a crosslinkable group in such a range, the cycle characteristics in the case of being used for a secondary battery can be improved while improving the strength of the obtained porous film. it can.

  The (meth) acrylic polymer used in the present invention may contain polymer units based on monomers copolymerizable therewith in addition to the above-described polymer units based on the monomers. Monomers copolymerizable with these include halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate; methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether Vinyl ethers such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, isopropenyl vinyl ketone and the like; heterocycle-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; acrylamide; Is mentioned.

  The (meth) acrylic polymer used in the present invention can be produced by polymerizing the above monomers. As the polymerization method, 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 polymer containing a nitrile group used in the present invention is not particularly limited as long as it contains a nitrile group. For example, in addition to a homopolymer of an unsaturated nitrile monomer, an unsaturated nitrile monomer And copolymers with other monomers copolymerizable with the polymer.

  The unsaturated nitrile monomer is not limited as long as it is an unsaturated compound having a nitrile group, such as acrylonitrile; α-halogenoacrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; methacrylonitrile, ethacrylonitrile and the like. α-alkylacrylonitrile; and the like. Among these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is particularly preferable.

  The content ratio of the unit of the unsaturated nitrile monomer in the polymer containing a nitrile group used in the present invention is preferably 1 to 100% by weight, more preferably 1 to 50% by weight.

  Examples of other copolymerizable monomers include conjugated diene monomers, unsaturated monocarboxylic acid monomers, unsaturated carboxylic acid ester monomers, unsaturated dicarboxylic acid monoester monomers, Examples include unsaturated polyvalent carboxylic acid monomers and aromatic vinyl monomers.

Examples of the conjugated diene monomer include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and the like.
Examples of the unsaturated monocarboxylic acid monomer include acrylic acid, methacrylic acid, and crotonic acid.
Examples of unsaturated carboxylic acid ester monomers include methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, n-pentyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, propyl methacrylate, and the like. Can be mentioned.

As unsaturated dicarboxylic acid monoester monomers, monomethyl maleate, monoethyl maleate, monopropyl maleate, mono n-butyl maleate, monomethyl fumarate, monoethyl fumarate, monopropyl fumarate, mono n-fumarate Examples include butyl.
Examples of the unsaturated polyvalent carboxylic acid monomer include itaconic acid, fumaric acid and maleic acid.
Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, vinyl pyridine and the like.

  The nitrile group-containing polymer used in the present invention is produced by polymerizing an unsaturated nitrile monomer alone or with another monomer copolymerizable with the unsaturated nitrile monomer. be able to. As the polymerization method, 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. As a polymerization initiator used for superposition | polymerization, the thing similar to the (meth) acrylic polymer mentioned above can be used, for example.

  Further, when the polymer containing a nitrile group used in the present invention is a nitrile rubber containing at least a unit of an unsaturated nitrile monomer and a unit of a conjugated diene monomer, an aliphatic carbon-carbon Hydrogenated nitrile rubber may be obtained by hydrogenating unsaturated bonds.

  The binder content in the porous membrane for a secondary battery of the present invention is preferably 3 to 20% by weight, more preferably 3 to 15% by weight. By making the content rate of a binder into such a range, the obtained porous film can have high intensity | strength, preventing the short circuit between electrodes.

  Further, in the porous membrane for a secondary battery of the present invention, the ratio of the content of non-conductive particles and the content of the binder is a weight ratio of “non-conductive particle weight / binder weight for porous membrane”. It is preferably in the range of 2 to 100, and more preferably in the range of 10 to 100. By setting these weight ratios within such a range, it is possible to maintain both high-temperature short-circuit resistance and excellent cycle characteristics.

  The binder used in the present invention is usually prepared and stored as a dispersion in the form of particles dispersed in a dispersion medium. As the dispersion medium, it is preferable to use water from the viewpoint of low environmental load and high drying speed. Alternatively, when an organic solvent is used as the dispersion medium, an organic solvent such as N-methylpyrrolidone (NMP) can be used.

  When the binder is dispersed in the dispersion medium in the form of particles, the number average particle diameter (dispersion particle diameter) of the binder is preferably 50 to 500 nm, more preferably 70 to 400 nm, and still more preferably 100 to 250 nm. is there. When the number average particle diameter of the binder is in such a range, the strength and flexibility of the obtained porous film are good.

  The content ratio of the binder in the dispersion is preferably 15 to 70% by weight, more preferably 20 to 65% by weight. When the content ratio of the binder is within such a range, workability in manufacturing a porous membrane slurry for a secondary battery, which will be described later, can be improved.

  The glass transition temperature (Tg) of the binder used in the present invention is preferably −50 to 25 ° C., more preferably −45 to 15 ° C., and particularly preferably −40 to 5 ° C. When the Tg of the binder is in such a range, the resulting porous film can have excellent strength and flexibility.

(Other ingredients)
In addition to the nonconductive particles and the binder, the porous membrane for a secondary battery of the present invention may contain a heavy metal capturing compound. By containing the heavy metal capturing compound, when the porous membrane for a secondary battery of the present invention is used for a secondary battery, it is possible to capture transition metal ions that elute in the electrolyte during charge / discharge of the secondary battery. Therefore, it is possible to prevent a decrease in cycle characteristics and safety of the secondary battery due to the transition metal ions.

  The heavy metal scavenging compound is not particularly limited as long as it has a heavy metal scavenging function, but preferably from the group consisting of an aminocarboxylic acid chelate compound, a phosphonic acid chelate compound, gluconic acid, citric acid, malic acid and tartaric acid. Selected. Among these, chelate compounds that can selectively capture transition metal ions without capturing lithium ions are used, and aminocarboxylic acid chelate compounds and phosphonic acid chelate compounds are particularly preferably used.

  Examples of aminocarboxylic acid-based chelate compounds include ethylenediaminetetraacetic acid (hereinafter sometimes referred to as “EDTA”), nitrilotriacetic acid (hereinafter sometimes referred to as “NTA”), trans-1,2-diamino. Cyclohexanetetraacetic acid (hereinafter sometimes referred to as “DCTA”), diethylene-triaminepentaacetic acid (hereinafter sometimes referred to as “DTPA”), bis- (aminoethyl) glycol ether-N, N, N ', N'-tetraacetic acid (hereinafter sometimes referred to as “EGTA”), N- (2-hydroxyethyl) ethylenediamine-N, N ′, N′-triacetic acid (hereinafter referred to as “HEDTA”) Selected from the group consisting of dihydroxyethylglycine (hereinafter sometimes referred to as “DHEG”). It is preferred that the.

  As the phosphonic acid-based chelate compound, 1-hydroxyethane-1,1-diphosphonic acid (hereinafter sometimes referred to as “HEDP”) is preferable.

  The compounding amount of the heavy metal capturing compound is preferably 0.001 to 1.0 part by weight, more preferably 0.005 to 0.5 part by weight, and particularly preferably 0.01 to 0.00 part by weight with respect to 100 parts by weight of the binder. 3 parts by weight. By setting the blending amount of the heavy metal capturing compound within such a range, the heavy metal capturing function can be sufficiently exhibited without impairing other characteristics.

  Moreover, in addition to each said component, arbitrary components may be contained in the porous film for secondary batteries of this invention. Examples of such optional components include dispersants, leveling agents, antioxidants, binders other than the binders described above, thickeners, antifoaming agents, and electrolytic solution additives having functions such as suppression of electrolytic solution decomposition. And the like.

  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 dispersing agent in the porous film is preferably within a range that does not affect the battery characteristics, and specifically 10% by weight or less.

  Examples of leveling agents include surfactants such as alkyl surfactants, silicon surfactants, fluorosurfactants, and metal surfactants. By mixing such surfactants, coating is possible. It is possible to prevent repelling that sometimes occurs and to improve the smoothness of the porous membrane.

  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.

  As a binder other than the above-mentioned binder, polytetrafluoroethylene (PTFE), polyacrylic acid derivatives, polyacrylonitrile derivatives, soft polymers, and the like can be used.

  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, phosphoric acid starch, casein, various modified starches, acrylonitrile-butadiene copolymer hydride, and the like.

  The content ratio of these optional components in the porous membrane for a secondary battery of the present invention is preferably in a range that does not affect the battery characteristics, specifically, preferably 10% by weight or less, When a plurality of arbitrary components are blended, the total content of the arbitrary components to be blended is preferably 40% by weight or less, more preferably 20% by weight or less.

  The porous membrane for a secondary battery of the present invention is obtained by, for example, (1) obtaining a porous membrane slurry for a secondary battery containing non-conductive particles, a binder and a dispersion medium, A method of forming a slurry layer by coating on a base material of the substrate, and then drying the slurry layer; (2) obtaining a porous membrane slurry for a secondary battery containing non-conductive particles, a binder and a dispersion medium, And a method of drying the substrate after immersing the substrate in the porous membrane slurry.

  The porous membrane slurry for a secondary battery is a composition containing the above-described non-conductive particles, the above-described binder, the dispersion medium, and the above-described optional components added as necessary.

The dispersion medium is not particularly limited as long as it can disperse non-conductive particles, a binder, and optional components uniformly, and an organic solvent can be used in addition to water.
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; Ethers such as ethylene glycol diethyl ether: alcohols such as methanol, ethanol, isopropanol, ethylene glycol, ethylene glycol monomethyl ether; N-methyl And amides such as lupyrrolidone 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 medium. Among these, those having particularly excellent dispersibility of non-conductive particles, low boiling point and high volatility are preferable. Specifically, acetone, toluene, cyclohexanone, cyclopentane, tetrahydrofuran, cyclohexane, xylene, water, N- Methyl pyrrolidone and the like are preferable.

  The solid content concentration in the porous membrane slurry for a secondary battery can be appropriately adjusted to such a concentration that the viscosity of the slurry composition can be applied and immersed and has fluidity. However, it is generally about 10 to 50% by weight. The component other than the solid component is a component that volatilizes in the drying process, and includes, in addition to the dispersion medium, for example, a medium in which these are dissolved or dispersed during the preparation of the non-conductive particles and the binder. It is.

  The method for preparing the porous membrane slurry for the secondary battery is not particularly limited, and by mixing the above-described non-conductive particles, the above-mentioned binder, the dispersion medium, and any of the above-described optional components added as necessary. Can be obtained. The mixing method and mixing order in mixing these are not particularly limited. The mixing device is not particularly limited as long as it can uniformly mix the above-described components, and includes a homomixer, ball mill, sand mill, pigment disperser, crusher, ultrasonic disperser, homogenizer, planetary mixer, etc. However, it is particularly preferable to use a homomixer from the viewpoint that an appropriate dispersion share can be added.

  The viscosity of the porous membrane slurry for a secondary battery is preferably 10 mPa · S to 10,000 mPa · S, more preferably 50 to 500 mPa · s, from the viewpoints of uniform coatability and slurry aging stability. The viscosity can be measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.

  The porous membrane for a secondary battery of the present invention may be, for example, one that can maintain the shape as a membrane independently of the one that maintains the shape as a membrane while being supported by a substrate. It is preferable that the substrate is supported by the substrate, that is, is formed into a film on the substrate to form a composite.

  In the present invention, as a base material for forming a porous film for a secondary battery, it is particularly preferable to use a constituent element in the secondary battery, specifically, an electrode (positive electrode or negative electrode) or an organic separator as the base material. preferable. That is, it is particularly preferable to use an electrode or an organic separator as a base material, and form the porous membrane for a secondary battery of the present invention thereon.

  Alternatively, when the secondary battery porous membrane of the present invention is formed on a substrate other than an electrode or an organic separator, the secondary battery porous membrane is peeled off from the substrate and assembled into a secondary battery. It can be used by stacking on top or on an organic separator. In addition, a well-known peeling film etc. can be used as base materials other than an electrode and an organic separator.

  The method for forming a slurry layer by applying a porous membrane slurry for a secondary battery onto a substrate is not particularly limited. For example, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method. And methods such as brushing and brushing. Among these, the dipping method and the gravure method are preferable from the viewpoint that a uniform porous film for a secondary battery can be obtained.

  Examples of the method for drying the slurry layer obtained by coating include drying by warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. What is necessary is just to set drying temperature according to the kind of dispersion medium to be used, for example, when using dispersion media with low volatility, such as N-methylpyrrolidone, with a high temperature of 120 degreeC or more with a ventilation type dryer. It is preferable to dry. Alternatively, when a highly volatile dispersion medium is used, it can be dried at a low temperature of 100 ° C. or lower. In addition, when forming the porous film for secondary batteries on an organic separator, since it is necessary to dry without causing shrinkage of an organic separator, drying at a low temperature of 100 ° C. or less is preferable.

  In addition, when forming a porous membrane for a secondary battery on an electrode, in order to improve the adhesion with the electrode active material layer, a press using a die press or a roll press is used as necessary. Processing may be performed.

  Although the film thickness of the porous film for secondary batteries of this invention is not specifically limited, Preferably it is 1-10 micrometers, More preferably, it is 2-7 micrometers. By setting the film thickness in such a range, the effect of forming the porous film for the secondary battery of the present invention can be appropriately obtained while keeping the capacity per volume (weight) of the obtained secondary battery high. .

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

  The secondary battery electrode of the present invention is, for example, made of an electrode composed of a current collector and an electrode active material layer as a base material, and the secondary battery porous film slurry is used thereon, and the secondary battery electrode of the present invention is used. It can be manufactured by forming a porous film. Alternatively, the porous membrane for a secondary battery of the present invention is formed on a substrate other than an electrode, and the obtained porous membrane for a secondary battery is peeled from the substrate, and this is used as a current collector and an electrode active material layer. The secondary battery electrode of the present invention can also be obtained by laminating the electrodes on the electrode.

  The current collector is not particularly limited as long as it is an electrically conductive and electrochemically durable material. From the viewpoint of heat resistance, for example, iron, copper, aluminum, nickel, stainless steel, and the like. Metal materials such as titanium, tantalum, gold, and platinum can be preferably used. 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.

  The electrode active material layer usually contains an electrode active material and a binder for the electrode active material layer, and may contain a conductivity imparting material, a reinforcing material, or the like as necessary.

  The electrode active material for forming the electrode active material layer is not particularly limited, but when the secondary battery electrode of the present invention is used for a positive electrode of a lithium ion secondary battery, the following inorganic compound A positive electrode active material made of or a positive electrode active material made of an organic compound can be used.

That is, 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.
Moreover, as a positive electrode active material consisting of an organic compound, for example, a conductive polymer compound such as polyacetylene or poly-p-phenylene can be used.

  Alternatively, when the secondary battery electrode of the present invention is used for a negative electrode of a lithium ion secondary battery, examples of the electrode active material for forming the electrode active material layer include amorphous carbon, graphite, and natural graphite. Carbonaceous materials such as mesocarbon microbeads and pitch-based carbon fibers, and conductive polymer compounds such as polyacene can be used. In addition to these, metals such as silicon, tin, zinc, manganese, iron and nickel, alloys thereof, oxides and sulfates of the metals or alloys, metal lithium, Li-Al, Li-Bi-Cd Lithium alloys such as Li—Sn—Cd, lithium transition metal nitrides, silicon, and the like can also be used.

  Further, when the secondary battery electrode of the present invention is used for a positive electrode of a nickel-hydrogen secondary battery, nickel hydroxide particles or the like are used as an electrode active material for forming an electrode active material layer. Can do. The nickel hydroxide particles may be solid-solved with cobalt, zinc, cadmium, or the like, or may be coated with a cobalt compound whose surface is subjected to an alkali heat treatment. In addition to yttrium oxide, nickel hydroxide particles include cobalt compounds such as cobalt oxide, metal cobalt and cobalt hydroxide, zinc compounds such as metal zinc, zinc oxide and zinc hydroxide, and rare earth compounds such as erbium oxide. The additive may be contained.

When the secondary battery electrode of the present invention is used for a negative electrode of a nickel-hydrogen secondary battery, hydrogen storage alloy particles are used as the electrode active material for forming the electrode active material layer. it can. The hydrogen storage alloy particles are not particularly limited as long as they can store hydrogen generated electrochemically in an alkaline electrolyte during battery charging and can easily release the stored hydrogen during discharge. , AB ₅ type system, preferably particles made of TiNi system and TiFe system hydrogen absorbing alloy. Specifically, LaNi ₅ , MmNi ₅ (Mm is a misch metal), LmNi ₅ (Lm is at least one selected from rare earth elements), and a part of Ni of these alloys are Al, Mn, Co, Ti, Cu, Multi-element hydrogen storage alloy particles substituted with one or more elements selected from Zn, Zr, Cr, and B can be used. In particular, hydrogen storage having a composition represented by the general formula: L _m Ni _w Co _x Mn _y Al _z (the total value of the atomic ratios w, x, y, z is 4.80 ≦ w + x + y + z ≦ 5.40) The alloy particles are suitable because the pulverization accompanying the progress of the charge / discharge cycle is suppressed and the charge / discharge cycle life is improved.

  Various resin components can be used as the binder for the electrode active material layer for forming the electrode active material layer. For example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives, and the like can be used.

Moreover, as a binder for electrode active material layers, in addition to the above-mentioned resin component, the soft polymer illustrated below can also be used.
That is, polybutyl acrylate, polybutyl methacrylate, polyhydroxyethyl methacrylate, polyacrylamide, polyacrylonitrile, butyl acrylate / styrene copolymer, butyl acrylate / acrylonitrile copolymer, butyl acrylate / acrylonitrile / glycidyl methacrylate copolymer, etc. An acrylic soft polymer, which is a homopolymer of acrylic acid or a methacrylic acid derivative, or a copolymer of monomers 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;
Other soft polymers such as natural rubber, polypeptide, protein, polyester-based thermoplastic elastomer, vinyl chloride-based thermoplastic elastomer, polyamide-based thermoplastic elastomer, and the like can also be used.

  Moreover, you may make an electrode active material layer contain a electroconductivity imparting material and a reinforcing material as needed. Examples of the conductivity imparting material include graphite, acetylene black, ketjen black, carbon black, graphite, vapor grown carbon fiber, and conductive carbon such as carbon nanotube. Examples of the reinforcing material include various inorganic and organic spherical, plate-like, rod-like, or fibrous fillers.

  The electrode active material layer is usually an electrode slurry obtained by dispersing an electrode active material, a binder for the electrode active material layer, and a conductivity-imparting material and a reinforcing material added as necessary in a dispersion medium. Can be formed on the current collector and dried as necessary.

  As a dispersion medium to be contained in the electrode slurry, an organic solvent can be used in addition to water. Examples of the organic solvent include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, γ-butyrolactone, ε -Esters such as caprolactone; Acylonitriles such as acetonitrile and propionitrile; Ethers such as tetrahydrofuran and ethylene glycol diethyl ether: Alcohols such as methanol, ethanol, isopropanol, ethylene glycol and ethylene glycol monomethyl ether; N-methyl Amides such as pyrrolidone and N, N-dimethylformamide may be mentioned. These media can be used alone or in combination of two or more, and can be appropriately selected from the viewpoint of drying speed and environment.

  The electrode slurry is prepared by mixing the electrode active material, the binder for the electrode active material layer, and the conductivity-imparting material and reinforcing material added as necessary, and the dispersion medium using a mixer. can get. 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.

(Separator for secondary battery)
The separator for a secondary battery of the present invention is formed by laminating the organic separator and the above-described porous film for a secondary battery of the present invention.

  The separator for a secondary battery of the present invention is produced, for example, by forming the porous film for a secondary battery of the present invention on the organic separator as a base material and using the porous film slurry for the secondary battery thereon. be able to. Alternatively, the porous membrane for a secondary battery of the present invention is formed on a substrate other than the organic separator, the obtained porous membrane for a secondary battery is peeled from the substrate, and this is laminated on the organic separator. The separator for a secondary battery of the present invention can also be obtained. In addition, as a separator for secondary batteries of this invention, the porous film for secondary batteries may be formed only in the single side | surface of the organic separator, or the porous film for secondary batteries was formed in both surfaces It may be a thing.

  As the organic separator, a known separator comprising a polyolefin resin such as polyethylene or polypropylene, or an aromatic polyamide resin can be used. However, in the present invention, there is no electron conductivity and there is ionic conductivity. A porous membrane having high resistance and a fine pore diameter can be preferably used. Examples of such organic separators include microporous membranes made of polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride), and mixtures or copolymers thereof, polyethylene terephthalate, polycycloolefins, polyethers, and the like. Microporous membrane made of resin such as sulfone, polyamide, polyimide, polyimide amide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene or the like, or non-woven fabric, aggregate of insulating substance particles Etc. Among these, the coating property of the porous membrane slurry for the secondary battery is excellent, and the film thickness of the entire separator can be reduced, thereby increasing the active material ratio in the secondary battery and increasing the capacity per volume. A microporous film made of a polyolefin-based resin is preferable because it can be used.

  The thickness of the organic separator is preferably 0.5 to 40 μm, more preferably 1 to 35 μm, and still more preferably 5 to 30 μm. When the thickness is in such a range, the resistance due to the organic separator in the secondary battery can be reduced while the coating property to the organic separator is good.

  In the present invention, examples of the polyolefin resin used as a 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 used in combination of two or more 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. The viscosity average molecular weight of polyethylene used as the material for the organic separator is preferably 100,000 to 12 million, more preferably 200,000 to 3 million, from the viewpoint of achieving both mechanical strength and high permeability.

  Moreover, as a polypropylene, a homopolymer, a random copolymer, and a block copolymer are mentioned, 1 type or 2 or more types can be mixed and 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.

  As a method for producing a polyolefin-based organic separator, a known method can be employed. For example, after forming a melt-extruded film of polypropylene and polyethylene, annealing at low temperature to grow a crystal domain, stretching in this state, and extending the amorphous region to form a microporous film; hydrocarbon After mixing a solvent or other low molecular weight material with polypropylene or polyethylene, a film is formed, and then a film in which the solvent or low molecular weight has gathered in the amorphous phase and has started to form an island phase is used. And a wet method in which a microporous film is formed by removing using a solvent that easily volatilizes.

  Moreover, the organic separator used by this invention may contain arbitrary fillers and fiber compounds in order to control intensity | strength, hardness, and heat shrinkage rate. Alternatively, for the purpose of improving the adhesion to the porous membrane for a secondary battery or improving the liquid impregnation property by lowering the surface tension with the electrolytic solution, the organic separator used in the present invention is preliminarily prepared with a low molecular compound or a high molecular weight compound. Coating treatment with a molecular compound, electromagnetic radiation treatment such as ultraviolet rays, or plasma treatment such as corona discharge / plasma gas may be performed. In particular, it is coated with a polymer compound containing a polar group such as a carboxylic acid group, a hydroxyl group, and a sulfonic acid group because it has a high impregnation property with an electrolytic solution and is easy to obtain adhesion with a porous membrane for a secondary battery. It is preferable.

(Secondary battery)
The secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte, and includes the above-described porous membrane for a secondary battery of the present invention in at least one of the positive electrode, the negative electrode, and the separator. That is, the secondary battery of this invention is comprised using the electrode for secondary batteries or the separator for secondary batteries of this invention mentioned above as at least any one of a positive electrode, a negative electrode, or a separator.

  Examples of the secondary battery of the present invention include a lithium ion secondary battery, a nickel-hydrogen secondary battery, etc., but there is a high demand for improvement in safety and the introduction effect of the porous film for the secondary battery of the present invention is high. To lithium ion secondary batteries are preferred. Hereinafter, the case where it uses for a lithium ion secondary battery is illustrated and demonstrated.

As the electrolytic solution for the lithium ion secondary battery, 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.

  The organic solvent used in the electrolyte for the lithium ion secondary battery is not particularly limited as long as it can dissolve the supporting electrolyte, but dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC). Carbonates such as propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfolane, Sulfur-containing compounds such as dimethyl sulfoxide are preferably used.

  As a specific method for producing a lithium ion secondary battery, a positive electrode and a negative electrode are overlapped via a separator, and this is wound into a battery container according to the shape of the battery. The method of injecting and sealing is mentioned. The shape of the secondary 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. Since the secondary battery of the present invention thus obtained comprises the porous film for a secondary battery of the present invention described above, the excellent characteristics of the porous film for a secondary battery of the present invention, that is, the film thickness High uniformity, high-temperature short-circuit resistance (reliability in high-temperature environments), and excellent ion permeability, high reliability in high-temperature environments, and excellent cycle and rate characteristics is there.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. “Part” and “%” in each example are based on weight unless otherwise specified.
In addition, the definition and evaluation method of each characteristic are as follows.

<Measurement of BET specific surface area of non-conductive particles>
The BET specific surface area of the non-conductive particles was measured by a gas adsorption method using a fully automatic BET specific surface area measuring device (product name “Macsorb HM model-1208”, manufactured by Mountec Co., Ltd.).

<Number average particle size of non-conductive particles, coefficient of variation of particle size>
For non-conductive particles, 100 particles are arbitrarily selected from SEM photographs taken at 25,000 times magnification with an electron microscope, the longest side of the particle image is a, the shortest side is b, and (a + b) / 2 Was calculated for each particle to determine the particle diameter of each particle, and the number average particle diameter was calculated as the arithmetic average value of the determined particle diameters. In addition, the standard deviation was calculated for the number average particle diameter, and the coefficient of variation of the particle diameter was calculated based on the number average particle diameter and the standard deviation.

<Average circularity of non-conductive particles>
For non-conductive particles, 100 particles are arbitrarily selected from SEM photographs taken at a magnification of 25000 times with an electron microscope, and the circumference of a circle having the same projected area as the particle image is L ₀ . When the perimeter was L, L ₀ / L was defined as the circularity, and the average circularity was calculated from the average of 100 pieces.

Ａ：３％未満
Ｂ：３％以上、１０％未満
Ｃ：１０％以上<Uniformity of porous film>
The organic separator with a porous film or the electrode with a porous film was cut into a width of 6 cm and a length of 1 m, and the thickness of the cut-out organic separator with a porous film or the electrode with a porous film was set to 20 points every 3 cm in the width direction and every 5 cm in the length direction. Measurement was made at 60 points, and the dispersion was calculated from the standard deviation and average value of the film thickness based on the following formula, and evaluated according to the following criteria. In the following formula, x represents the average value of the film thickness, and n represents the number of measurements.

A: Less than 3% B: 3% or more, less than 10% C: 10% or more

<Reliability test of organic separator with porous membrane>
The organic separator with a porous film was punched into a circle having a diameter of 19 mm, immersed in a 3% by weight methanol solution of a nonionic surfactant (Emulgen 210P, manufactured by Kao Corporation) and air-dried. Then, this circular organic separator with a porous film is impregnated with an electrolytic solution, and sandwiched between a pair of circular SUS plates (diameter 15.5 mm), and a laminated body of SUS plate / circular organic separator with porous membrane / SUS plate. Got. As the electrolyte, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in (EC:: DEC = 1 2 ( volume ratio at 20 ° C.)), of LiPF ₆ 1 mol / liter concentration The solution dissolved in was used.

Next, the laminate obtained above was sealed in a 2032 type coin cell, a lead wire was taken from the coin cell, and a thermocouple was attached and placed in an 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, as the temperature rises, the resistance value increases due to shutdown, the resistance value becomes at least 1000 Ω / cm ² or more, and then the resistance value rapidly decreases to 10 Ω / cm ² or less. In some cases, a short circuit occurred. This test was performed on 20 samples and evaluated according to the following criteria. The smaller the number of short circuits, the better the reliability.
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 electrode with porous membrane>
An organic separator (single-layer polypropylene separator, porosity 55%, thickness 25 μm) is punched into a 19 mm diameter circle and immersed in a 3% by weight methanol solution of a nonionic surfactant (Emulgen 210P, manufactured by Kao Corporation). And air dried. Separately, the electrode with a porous film to be measured is punched into a circle having a diameter of 19 mm, a circular organic separator and a circular electrode with a porous film are impregnated with an electrolyte, and these are overlapped to form a pair of circles. To obtain a laminate of SUS plate / circular organic separator / circular electrode with porous film / SUS plate. The circular electrode with a porous membrane was arranged so that the surface on the porous membrane side was the organic separator side. As the electrolyte, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in (EC:: DEC = 1 2 ( volume ratio at 20 ° C.)), of LiPF ₆ 1 mol / liter concentration The solution dissolved in was used.

Next, the laminate obtained above is sealed in a 2032 type coin cell, a lead wire is taken from the coin cell, a thermocouple is attached and placed in an oven, and the above-mentioned "reliability test of organic separator with porous film" is described. In the same way as above, the occurrence of short circuit was confirmed. In addition, this test was evaluated on the following criteria about 20 samples. The smaller the number of short circuits, the better the reliability.
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

<Cycle characteristics of secondary battery>
With respect to the full cell coin type lithium ion secondary battery, charging / discharging of charging from 3 V to 4.3 V at 20 ° C. and 0.2 C and then discharging from 4.3 V to 3 V at 0.2 C was repeated 100 cycles. A value obtained by calculating the percentage of the discharge capacity at the 100th cycle relative to the discharge capacity at the second cycle as a percentage was determined as the capacity maintenance rate, and was judged according to the following criteria. It can be judged that the larger the value, the less the discharge capacity is reduced and the cycle characteristics are excellent.
A: 95% or more B: 90% or more, less than 95% C: 85% or more, less than 90% D: 80% or more, less than 85% E: Less than 80%

<Rate characteristics of secondary battery>
A full cell coin type lithium ion 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 discharge capacity of 0.1 C. It was. Subsequently, it charged to 4.2V at 0.1C, discharged to 3.0V at 1C, and calculated | required the discharge capacity of 1C. These measurements are performed on 10 cells of a full-cell coin-type lithium ion secondary battery, and the average value of each measurement value is 0.1 C for the discharge capacity of _{0.1 C} and 1 C for the discharge capacity of ₁ C. And the capacity retention ratio represented by the ratio of the electric capacity between the discharge capacity C _{1C of 1C} and the discharge capacity C _{0.1C of 0.1C} ((C _1C / C _0.1C ) × 100 (%)). This was used as an evaluation standard for rate characteristics. It can be determined that the higher the value, the better the rate characteristic.
A: 90% or more B: 80% or more, less than 90% C: 50% or more, less than 80% D: 30% or more, less than 50% E: Less than 30%

Example 1
<Manufacture of seed polymer particles>
In a reactor equipped with a stirrer, 93.8 parts of butyl acrylate, 2 parts of acrylonitrile, 2 parts of methacrylic acid, 1 part of allyl glycidyl ether, 1 part of N-methylolacrylamide, 122 parts of ion-exchanged water, and 0. Two parts were added and polymerized at 70 ° C. for 6 hours. Thereby, an aqueous dispersion of seed polymer particles (A-1) having an average particle diameter of 400 nm was obtained.

<Manufacture of non-conductive particles>
Next, in a reactor equipped with a stirrer, 10 parts of the aqueous dispersion of the seed polymer particles (A-1) obtained above is based on the solid content (that is, based on the weight of the seed polymer particles (A-1)). , Ethylene glycol dimethacrylate (trade name “Light Ester EG”, manufactured by Kyoeisha Chemical Co., Ltd.) 83.3 parts, toluene 16.7 parts, sodium dodecylbenzenesulfonate 1 part, t-butylperoxy-2-ethyl as a crosslinking agent 5 parts of hexanoate (trade name “Perbutyl O”, manufactured by NOF Corporation) and 200 parts of ion-exchanged water are added and stirred at 35 ° C. for 12 hours, so that the seed polymer particles (A-1) are mixed with ethylene glycol. Dimethacrylate, toluene and crosslinker were completely absorbed. Next, this is polymerized at 90 ° C. for 5 hours, and then water is dispersed in the polymer particles (B-1) having a number average particle diameter of 700 nm by introducing steam to remove unreacted monomers. A liquid was obtained.

  And about the obtained polymer particle (B-1), the BET specific surface area, the variation coefficient of a particle size, and the average circularity were measured. The results are shown in Table 1.

<Binder production>
In a reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.4 part of sodium dodecylbenzenesulfonate and 0.3 part of potassium persulfate were added and mixed to obtain a mixture A, which was obtained at 60 ° C. The temperature was raised to. On the other hand, in a separate container, 50 parts of ion exchanged water, 0.8 part of sodium dodecylbenzenesulfonate, 77.7 parts of 2-ethylhexyl acrylate, 19.85 parts of acrylonitrile, 2 parts of methacrylic acid, and 0.2 parts of allyl methacrylate Parts were mixed to obtain a monomer mixture. And the obtained monomer mixture was polymerized by adding continuously in the mixture A obtained above over 4 hours. When adding the monomer mixture into the mixture A, the polymerization reaction was carried out by maintaining the temperature of the reaction system at 60 ° C. And after completion | finish of addition of a monomer mixture, the aqueous dispersion containing an acrylic polymer binder (C-1) was obtained by continuing reaction at 70 degreeC for 3 hours further.

  And after cooling the aqueous dispersion of the obtained acrylic polymer binder (C-1) to 25 degreeC, ammonia water is added to this and pH is adjusted to 7, Then, steam is introduce | transduced and it is unreacted. The monomer was removed. Immediately thereafter, 0.25 part of ethylenediaminetetraacetic acid was added to 100 parts of the solid content of the binder, and these were mixed and further adjusted to a solid content concentration with ion-exchanged water, and 200 mesh (mesh size of about 77 μm). ) To obtain an aqueous dispersion of an acrylic polymer binder (C-1) having an average particle diameter of 100 nm and a solid content concentration of 40%.

  In addition, the composition of the obtained acrylic polymer binder (C-1) is 2-ethylhexyl acrylate unit 77.9%, acrylonitrile unit 19.9%, methacrylic acid unit 2%, and allyl methacrylate unit 0.2%. there were.

<Preparation of slurry for porous membrane>
An aqueous dispersion of the polymer particles (B-1) obtained above, and an aqueous dispersion of the acrylic polymer binder (C-1) obtained above and carboxymethyl cellulose (trade name “Daicel 1220”, Manufactured by Daicel Chemical Industries, Ltd.) in water so that the weight ratio of solids is “polymer particles (B-1): binder (C-1): carboxymethylcellulose” = 83.1: 12.3: 4.6. By mixing, a slurry for porous membrane was obtained.

<Manufacture of positive electrode>
To 95 parts of lithium manganate having a spinel structure as a positive electrode active material, polyvinylidene fluoride (KF-1100, manufactured by Kureha Chemical Industry Co., Ltd.) as a positive electrode binder is added to 3 parts in terms of solid content, and further 2 parts of acetylene black and 20 parts of N-methylpyrrolidone were added and mixed with a planetary mixer to obtain a slurry for positive electrode. And after apply | coating the obtained slurry for positive electrodes to the single side | surface of 18-micrometer-thick aluminum foil and drying at 120 degreeC for 3 hours, a roll press is performed and the positive electrode which has a positive-electrode active material layer with a total thickness of 100 micrometers is obtained. It was.

<Manufacture of negative electrode>
98 parts of graphite (average particle diameter 20 μm, specific surface area 4.2 m ² / g) as a negative electrode active material, and 1 part of styrene-butadiene rubber (glass transition temperature: −10 ° C.) as a binder for negative electrode in terms of solid content The resulting mixture is mixed with 1.0 part of carboxymethyl cellulose and water as a dispersion medium, and mixed with a planetary mixer to obtain a slurry for a negative electrode. Got. And after apply | coating the obtained slurry for negative electrodes on the single side | surface of 18-micrometer-thick copper foil and drying at 120 degreeC for 3 hours, a roll press is performed and the negative electrode which has a negative electrode active material layer with a total thickness of 60 micrometers is obtained. It was.

<Manufacture of organic separator with porous membrane>
A single-layer polypropylene organic separator (porosity 55%, thickness 25 μm) produced by a dry method was prepared, and the slurry for the porous membrane obtained above was prepared on one surface of the polypropylene organic separator. The slurry layer was formed by apply | coating using a wire bar so that the thickness after drying might be set to 5 micrometers. Next, the formed slurry layer was dried at 50 ° C. for 10 minutes to form a porous film. And the same operation was performed also on the other surface of the organic separator made of polypropylene, whereby a porous film was formed in the same manner, and an organic separator with a porous film having a porous film on both surfaces was obtained.

<Production of secondary battery>
Then, the positive electrode, the negative electrode, and the organic separator with a porous film obtained above were cut into circles with diameters of 13 mm, 14 mm, and 18 mm, respectively, and on the inner bottom surface of a stainless steel coin-type outer container provided with polypropylene packing In addition, a circular positive electrode with a diameter of 13 mm, an organic separator with a porous film with a diameter of 18 mm, and a circular negative electrode with a diameter of 14 mm were laminated in this order, and these were stored in a coin-type outer container. The positive electrode was placed so that the surface on the aluminum foil side faced the bottom surface side of the outer container, and the surface on the positive electrode active material layer side faced the organic separator with a porous film. Further, the negative electrode was placed so that the surface on the negative electrode active material layer side faced toward the organic separator with a porous film and the surface on the copper foil side faced upward.

Next, inject the electrolyte into the container so that no air remains, and fix it with a 0.2 mm thick stainless steel cap on the coin-type outer container via polypropylene packing, and seal the battery can Thus, a full cell coin-type lithium ion secondary battery (coin cell CR2032) having a diameter of 20 mm and a thickness of about 3.2 mm was manufactured. As the electrolyte, a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in (EC:: DEC = 1 2 ( volume ratio at 20 ° C.)), of LiPF ₆ 1 mol / liter concentration The solution dissolved in was used.

  And about the organic separator with a porous film obtained above, evaluation of reliability according to an above-mentioned method, and about the secondary characteristic obtained above, about cycle characteristics and rate characteristics according to an above-mentioned method. Evaluation was performed. The results are shown in Table 1.

(Example 2)
<Manufacture of seed polymer particles>
In the same manner as in Example 1, seed polymer particles (A-1) were obtained.

<Manufacture of precursors of non-conductive fine particles>
In a reactor equipped with a stirrer, 80 parts of ethylene glycol dimethacrylate, 1 part of sodium dodecylbenzenesulfonate, and 2 parts of t-butylperoxy-2-ethylhexanoate were added and dissolved. The precursor solution was obtained by adding 200 parts of water and mixing for 5 minutes under strong stirring.

<Manufacture of non-conductive fine particles>
Next, 20 parts of the seed polymer particles (A-1) obtained above were added to the precursor solution obtained above, and after gently stirring at 50 ° C. for 30 minutes, 4 parts at 60 ° C. Polymerization was carried out for a period of time, and further aged at 90 ° C. for 8 hours to obtain a dispersion of polymer particles. Then, the obtained dispersion of polymer particles is subjected to suction filtration to perform dehydration to obtain a wet cake of polymer particles, and then reconstituted in a 4% NaOH aqueous solution so that the solid content concentration becomes 20%. After dispersion, heating was performed at 90 ° C. for 2 hours. Then, the aqueous dispersion (solid content concentration 20%) of the polymer particle (B-2) whose number average particle diameter is 700 nm was obtained by cooling.
Thus, about the obtained polymer particle (B-2), the BET specific surface area, the variation coefficient of a particle size, and the average circularity were measured. The results are shown in Table 1.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-2) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Example 3)
<Manufacture of non-conductive particles>
Except that the blending amount of ethylene glycol dimethacrylate was changed from 83.3 parts to 85.7 parts and the blending amount of toluene was changed from 16.7 parts to 14.3 parts, An aqueous dispersion of polymer particles (B-3) having an average particle diameter of 700 nm was obtained.
Thus, about the obtained polymer particle (B-3), the BET specific surface area, the variation coefficient of a particle size, and the average circularity were measured. The results are shown in Table 1.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-3) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

Example 4
<Manufacture of non-conductive particles>
The number average particle size was the same as in Example 1 except that the blending amount of ethylene glycol dimethacrylate was changed from 83.3 parts to 75 parts and the blending amount of toluene was changed from 16.7 parts to 25 parts. An aqueous dispersion of polymer particles (B-4) having a diameter of 700 nm was obtained.
Thus, about the obtained polymer particle (B-4), the BET specific surface area, the variation coefficient of a particle size, and the average circularity were measured. The results are shown in Table 1.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-4) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Example 5)
<Manufacture of non-conductive particles>
An aqueous dispersion of polymer particles (B-5) having a number average particle diameter of 950 nm was obtained in the same manner as in Example 1 except that a 3.33% NaOH aqueous solution was used instead of the 4% NaOH aqueous solution. It was.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-5) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Example 6)
<Manufacture of non-conductive particles>
An aqueous dispersion of polymer particles (B-6) having a number average particle diameter of 200 nm was obtained in the same manner as in Example 1 except that a 6.67% NaOH aqueous solution was used instead of the 4% NaOH aqueous solution. It was.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-6) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Example 7)
The aqueous dispersion of the polymer particles (B-1) obtained above, and the aqueous dispersion of the acrylic polymer binder (C-1) obtained above and carboxymethyl cellulose, the solid content weight ratio is “ Polymer particle (B-1): Binder (C-1): Carboxymethylcellulose "= 83.1: Slurry for porous membrane in the same manner as in Example 1 except that it was blended to be 4.6. A porous membrane-attached organic separator and a secondary battery were obtained in the same manner as in Example 1 except that the obtained slurry for a porous membrane was used and evaluated in the same manner. The results are shown in Table 1.

(Example 8)
The aqueous dispersion of the polymer particles (B-1) obtained above, and the aqueous dispersion of the acrylic polymer binder (C-1) obtained above and carboxymethyl cellulose, the solid content weight ratio is “ Polymer particle (B-1): Binder (C-1): Carboxymethyl cellulose "= 83.1: 8: A slurry for a porous membrane in the same manner as in Example 1 except that it was blended to be 4.6. A porous membrane-attached organic separator and a secondary battery were obtained in the same manner as in Example 1 except that the obtained slurry for a porous membrane was used and evaluated in the same manner. The results are shown in Table 1.

Example 9
<Binder production>
The amount of sodium dodecylbenzenesulfonate was changed from 0.8 part to 0.4 part, and as a monomer used for polymerization, 64 parts of 2-ethylhexyl acrylate, 2 parts of methacrylic acid, and 34 parts of styrene were used. In the same manner as in Example 1, an aqueous dispersion of an acrylic polymer binder (C-2) was obtained. In addition, the composition of the obtained acrylic polymer binder (C-2) was 2-ethylhexyl acrylate unit 64%, methacrylic acid unit 2%, and styrene unit 34%.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous films, instead of the acrylic polymer binder (C-1), except that the acrylic polymer binder (C-2) obtained above was used, Example 1 and Similarly, a porous membrane slurry was prepared, and the porous membrane-attached organic separator and the secondary battery were obtained in the same manner as in Example 1 except that the obtained porous membrane slurry was used. went. The results are shown in Table 1.

(Example 10)
In the same manner as in Example 1, an aqueous dispersion of polymer particles (B-1) was obtained, and the obtained aqueous dispersion of polymer particles (B-1) was replaced with N-methyl 2-pyrrolidone. An N-methyl 2-pyrrolidone dispersion of polymer particles (B-1) was obtained.

  And instead of the aqueous dispersion of polymer particles (B-1), N-methyl 2-pyrrolidone dispersion of polymer particles (B-1) is used, and the acrylic polymer binder (C-1) is used. Instead, hydrogenated nitrile rubber (trade name “BM-720H”, manufactured by Nippon Zeon Co., Ltd.) was used, and the solid content weight ratio was “polymer particles (B-1): hydrogenated nitrile rubber: N-methyl 2- Except for blending so that the pyrrolidone was 36.6: 3.4: 60, a porous membrane slurry was prepared in the same manner as in Example 1, and the obtained porous membrane slurry was used. In the same manner as in Example 1, an organic separator with a porous film and a secondary battery were obtained and evaluated in the same manner. The results are shown in Table 1.

(Example 11)
Example except that acrylonitrile-methyl methacrylate copolymer (trade name “HB-69”, manufactured by Nippon Zeon Co., Ltd., 97% acrylonitrile unit, 3% methyl methacrylate unit) was used instead of hydrogenated nitrile rubber. In the same manner as in Example 10, except that the porous membrane slurry was prepared and the obtained porous membrane slurry was used, an organic separator with a porous membrane and a secondary battery were obtained in the same manner as in Example 10, and similarly. Evaluation was performed. The results are shown in Table 1.

(Example 12)
In the same manner as in Example 1, an aqueous dispersion of acrylic polymer binder (C-1) was obtained, and the obtained aqueous dispersion of acrylic polymer binder (C-1) was replaced with N-methyl 2-pyrrolidone. An N-methyl 2-pyrrolidone dispersion of acrylic polymer binder (C-1) was obtained.

  Then, in place of the hydrogenated nitrile rubber, a porous membrane was obtained in the same manner as in Example 10 except that the N-methyl 2-pyrrolidone dispersion of the acrylic polymer binder (C-1) obtained above was used. An organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 10 except that the slurry for a porous membrane was prepared and the obtained slurry for a porous membrane was used. The results are shown in Table 1.

(Example 13)
A porous membrane slurry was prepared in the same manner as in Example 10 except that polyvinylidene fluoride (manufactured by Arkema) was used in place of the hydrogenated nitrile rubber, except that the obtained porous membrane slurry was used. In the same manner as in Example 10, an organic separator with a porous film and a secondary battery were obtained and evaluated in the same manner. The results are shown in Table 1.

(Example 14)
<Manufacture of electrode with porous membrane>
A slurry for a porous membrane produced in the same manner as in Example 1 was applied to the negative electrode active material layer side surface of the negative electrode produced in the same manner as in Example 1 so that the thickness of the porous membrane after drying was 5 μm. A slurry layer was obtained. The slurry layer was formed so that the negative electrode active material layer was completely covered. And the formed slurry layer was dried at 110 degreeC for 10 minute (s), and the electrode with a porous film (negative electrode with a porous film) was obtained by making it into a porous film. In addition, the obtained electrode with a porous film had a layer structure of porous film / negative electrode active material layer / copper foil.

  And about the obtained electrode with a porous film, reliability evaluation was performed according to the above-mentioned method. The results are shown in Table 1.

<Manufacture of secondary batteries>
Further, instead of the organic separator with a porous membrane, a single-layered polypropylene organic separator produced by a dry method (porosity 55%, thickness 25 μm, except that no porous membrane was formed) In the same manner as in Example 1, except that the separator with a porous film and the electrode with a porous film obtained above (negative electrode with a porous film) was used as the negative electrode, Evaluation was performed. The results are shown in Table 1.

(Comparative Example 1)
When preparing the slurry for the porous membrane, instead of the polymer particles (B-1), alumina (trade name “HIT-70”, manufactured by Sumitomo Chemical Co., Ltd., number average particle diameter 150 nm, BET specific surface area 20 m ² / g ) And the solid content weight ratio was “alumina: binder (C-1): carboxymethylcellulose” = 94.8: 1.42: 3.78 Similarly, a porous membrane slurry was prepared, and the porous membrane-attached organic separator and the secondary battery were obtained in the same manner as in Example 1 except that the obtained porous membrane slurry was used. went. The results are shown in Table 1.

(Comparative Example 2)
<Manufacture of non-conductive particles>
Except that the blending amount of ethylene glycol dimethacrylate was changed from 83.3 parts to 93.75 parts and the blending amount of toluene was changed from 16.7 parts to 6.25 parts, An aqueous dispersion of polymer particles (B-7) having an average particle diameter of 700 nm was obtained.
The polymer particles (B-7) thus obtained were measured for BET specific surface area, particle size variation coefficient, and average circularity. The results are shown in Table 1.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-7) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Comparative Example 3)
<Manufacture of non-conductive particles>
The number average particle size was the same as in Example 1 except that the blending amount of ethylene glycol dimethacrylate was changed from 83.3 parts to 50 parts and the blending amount of toluene was changed from 16.7 parts to 50 parts. An aqueous dispersion of polymer particles (B-8) of 700 nm was obtained.
The polymer particles (B-8) thus obtained were measured for a BET specific surface area, a particle size variation coefficient, and an average circularity. The results are shown in Table 1.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-8) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Comparative Example 4)
<Manufacture of seed polymer particles>
An aqueous dispersion of seed polymer particles (A-2) having an average particle diameter of 50 nm was obtained in the same manner as in Example 1 except that the polymerization conditions were changed from 70 ° C. for 6 hours to 80 ° C. for 3 hours. .

<Manufacture of non-conductive particles>
The number average particle diameter is 700 nm in the same manner as in Example 1 except that the aqueous dispersion of seed polymer particles (A-2) was used instead of the aqueous dispersion of seed polymer particles (A-1). An aqueous dispersion of polymer particles (B-9) was obtained.
The polymer particles (B-9) thus obtained were measured for BET specific surface area, particle size variation coefficient, and average circularity. The results are shown in Table 1.

<Preparation of slurry for porous membrane, production of secondary battery>
And when preparing the slurry for porous membranes, it carried out similarly to Example 1 except having used the polymer particle (B-9) obtained above instead of the polymer particle (B-1). A porous membrane slurry was prepared, and an organic separator with a porous membrane and a secondary battery were obtained and evaluated in the same manner as in Example 1 except that the obtained porous membrane slurry was used. . The results are shown in Table 1.

(Comparative Example 5)
In the same manner as in Example 1, an aqueous dispersion of acrylic polymer binder (C-1) was obtained, and the obtained aqueous dispersion of acrylic polymer binder (C-1) was replaced with N-methyl 2-pyrrolidone. An N-methyl 2-pyrrolidone dispersion of acrylic polymer binder (C-1) was obtained.

  And instead of the aqueous dispersion of the acrylic polymer binder (C-1), the N-methyl 2-pyrrolidone dispersion of the acrylic polymer binder (C-1) obtained above is used, and carboxymethylcellulose. Is added so that the weight ratio of solid content is “alumina: acrylic polymer binder (C-1)” = 94.8: 5.2, and mixed in N-methyl 2-pyrrolidone. The porous membrane slurry was prepared in the same manner as in Comparative Example 1 except that the porous membrane slurry was prepared and the porous membrane slurry was prepared in the same manner as in Comparative Example 1 except that the obtained porous membrane slurry was used. A secondary battery was obtained and evaluated in the same manner. The results are shown in Table 1.

(Comparative Example 6)
<Manufacture of electrode with porous membrane>
A slurry for a porous membrane produced in the same manner as in Comparative Example 5 was applied to the negative electrode active material layer side surface of the negative electrode produced in the same manner as in Example 1 so that the thickness of the porous membrane after drying was 5 μm. A slurry layer was obtained. The slurry layer was formed so that the negative electrode active material layer was completely covered. And the formed slurry layer was dried at 110 degreeC for 10 minute (s), and the electrode with a porous film (negative electrode with a porous film) was obtained by making it into a porous film. In addition, the obtained electrode with a porous film had a layer structure of porous film / negative electrode active material layer / copper foil.

  And about the obtained electrode with a porous film, reliability evaluation was performed according to the above-mentioned method. The results are shown in Table 1.

<Manufacture of secondary batteries>
Further, instead of the organic separator with a porous membrane, a single-layered polypropylene organic separator produced by a dry method (porosity 55%, thickness 25 μm, except that no porous membrane was formed) In the same manner as in Example 1, except that the separator with a porous film and the electrode with a porous film obtained above (negative electrode with a porous film) was used as the negative electrode, Evaluation was performed. The results are shown in Table 1.

As shown in Table 1, the organic separator with a porous film formed by the organic separator and the porous film for a secondary battery of the present invention has a uniform film thickness and reliability in a high temperature environment (high temperature short circuit characteristics). In addition, when used as a separator for a secondary battery, the obtained secondary battery was excellent in cycle characteristics and rate characteristics (Examples 1 to 13).
In addition, the electrode with the porous film formed by the electrode and the porous film for the secondary battery of the present invention is also excellent in the uniformity of the film thickness and the reliability in the high temperature environment (high temperature short circuit resistance). When used as an electrode for a secondary battery, the obtained secondary battery was excellent in cycle characteristics and rate characteristics (Example 14).

  On the other hand, when using alumina as the inorganic particles as the non-conductive particles for constituting the porous membrane for the secondary battery, the secondary battery obtained when used as a separator for the secondary battery, The cycle characteristics and rate characteristics were inferior (Comparative Example 1). This tendency is the same when N-methyl 2-pyrrolidone is used as a dispersion medium or when an electrode with a porous film is used. In particular, in these cases, the organic film with a porous film to be obtained is used. The separator and the electrode with a porous film were inferior in reliability (high temperature short circuit resistance) in a high temperature environment (Comparative Examples 5 and 6).

  Further, when polymer particles having a BET specific surface area outside the predetermined range of the present invention are used as the non-conductive particles for constituting the porous membrane for the secondary battery, and the number average particle size is within the predetermined range of the present invention. When polymer particles that are outside are used, the obtained organic separator with a porous membrane is inferior in reliability (high temperature short circuit resistance) in a high temperature environment, and when used as a separator for a secondary battery. The obtained secondary batteries were inferior in cycle characteristics and rate characteristics (Comparative Examples 2 to 4).

Claims (8)

A porous membrane for a secondary battery containing non-conductive particles and a binder,
The porous film for a secondary battery, wherein the non-conductive fine particles are polymer particles having a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m ² / g. The binder is a (meth) acrylic polymer or a polymer containing a nitrile group,
2. The secondary battery according to claim 1, wherein a content ratio of the (meth) acrylic polymer or the polymer containing a nitrile group in the porous film for the secondary battery is 3 to 20 wt%. Porous membrane. A porous membrane slurry for a secondary battery containing non-conductive particles, a binder and a dispersion medium,
A porous membrane slurry for a secondary battery, wherein the non-conductive fine particles are polymer particles having a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m ² / g. The binder is a polymer containing a nitrile group or a (meth) acrylic polymer,
The content ratio of the polymer containing the nitrile group or the (meth) acrylic polymer in the solid content contained in the porous membrane slurry for the secondary battery is 3 to 20% by weight. The porous membrane slurry for secondary batteries as described in 2. A non-conductive particle for a porous membrane for a secondary battery, comprising polymer particles having a number average particle diameter of 100 to 1000 nm and a BET specific surface area of 14.56 to 72.8 m ² / g.   An electrode for a secondary battery, comprising a current collector, an electrode active material layer, and a porous film for a secondary battery according to claim 1 or 2 laminated in this order.   A separator for a secondary battery, which is formed by laminating an organic separator and the porous membrane for a secondary battery according to claim 1 or 2.   It is a secondary battery containing a positive electrode, a negative electrode, a separator, and an electrolyte solution, and the porous film for a secondary battery according to claim 1 or 2 is provided in at least one of the positive electrode, the negative electrode, and the separator. Secondary battery characterized.