JP2016004758A - Binder composition for nonaqueous secondary battery porous membrane, composition for nonaqueous secondary battery porous membrane, porous membrane for nonaqueous secondary battery, and nonaqueous secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a binder composition for a nonaqueous secondary battery porous membrane, excellent in durability in an electrolyte, capable of forming a porous membrane low in moisture content, and also capable of increasing stability when a porous membrane composition is sheared.SOLUTION: A binder composition for a nonaqueous secondary battery porous membrane contains a particulate polymer including 0.05 mass% or more and 5 mass% or less of a monomer unit having two or more hydroxyl groups.

Description

  The present invention relates to a binder composition for a nonaqueous secondary battery porous film, a composition for a nonaqueous secondary battery porous film, a porous film for a nonaqueous secondary battery, and a nonaqueous secondary battery.

  Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes abbreviated as “secondary batteries”) have the characteristics of being small and lightweight, having high energy density, and capable of repeated charge and discharge. It is used for a wide range of purposes. The secondary battery generally includes a battery member such as a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode and prevents a short circuit between the positive electrode and the negative electrode. In secondary batteries, a porous film may be provided as a protective layer on electrodes (positive electrode and negative electrode) and separators for the purpose of improving their heat resistance and strength.

  Here, examples of the porous film include those formed by binding non-conductive particles such as organic particles and inorganic particles with a binder. Such a porous film is usually referred to as a slurry composition in which a porous film material such as non-conductive particles or a binder is dissolved or dispersed in a dispersion medium such as water (hereinafter referred to as “a composition for a porous film”). ), And this porous film composition is applied and dried on a substrate such as an electrode or a separator.

  In recent years, for the purpose of further improving the performance of secondary batteries, improvement of the porous film, more specifically, the binder used for the porous film has been actively performed. For example, Patent Document 1 uses a copolymer containing a (meth) acrylate monomer unit and a crosslinkable monomer unit as a binder, and additionally containing an unsaturated carboxylic acid monomer unit at a specific ratio or more. A technique for forming a porous film on the surface of a polyolefin resin separator has been proposed. And the separator provided with the porous film of patent document 1 is reported that heat shrinkage | contraction is suppressed and when using it for a secondary battery, a possibility that a positive electrode and a negative electrode may short-circuit can be reduced.

JP 2011-8966 A

Here, the porous film used in the secondary battery has the electrical characteristics (self-discharge) excellent in the secondary battery in addition to the function of ensuring the heat resistance and strength of the battery member and preventing the short circuit as described above. Characteristics and low temperature output characteristics).
However, in the above conventional technique, no attention is paid to moisture brought into the porous film by the binder, particularly in the case where the copolymer as the binder contains many unsaturated carboxylic acid monomer units. There is a possibility that the amount of moisture brought into the porous film increases due to the functional carboxyl group, and the electrical characteristics of the secondary battery are impaired.

In addition, in order to further improve the electrical characteristics of secondary batteries, the binder for porous membranes is used severely, for example, when it is installed in an electric vehicle that is continuously subjected to large vibrations during use. Even under the conditions, it is required that the components in the porous film are sufficiently prevented from desorbing in the electrolytic solution, that is, that the porous film has sufficient durability in the electrolytic solution.
In addition, the porous film composition containing a binder used for forming the porous film is formed by rotating the gravure roll when it is applied with a gravure coating device, for example, when the porous film is formed on the substrate. Receives shearing force. Due to this shearing force, when a porous film is formed over a long period of time, or when the rotational speed of the gravure roll is increased for high-speed molding, the components in the composition for the porous film are aggregated to form a porous film with a uniform thickness. There was also a problem that it was difficult to obtain a film.

Therefore, the present invention is capable of forming a porous film that is excellent in durability in an electrolytic solution, has a low water content, and can enhance the stability of the composition for porous film under shear. It aims at providing the binder composition for water based secondary battery porous membranes.
In addition, the present invention provides a composition for a porous membrane of a non-aqueous secondary battery that is excellent in durability in an electrolytic solution, can form a porous membrane with a low water content, and is excellent in stability under shear. The purpose is to provide.
An object of the present invention is to provide a porous film for a non-aqueous secondary battery that is excellent in durability in an electrolytic solution and has a low water content, and a non-aqueous secondary battery that is excellent in electrical characteristics.

  The present inventor has intensively studied for the purpose of solving the above problems. Then, the present inventor uses a binder composition containing a particulate polymer containing a monomer unit having at least two hydroxyl groups in a specific ratio for the preparation of a porous membrane composition, It is found that the stability of the membrane composition under shear is ensured, and the porous membrane formed from the porous membrane composition has a low water content and is excellent in durability in an electrolyte solution, The present invention has been completed.

  That is, this invention aims to solve the above-mentioned problem advantageously, and the binder composition for a nonaqueous secondary battery porous membrane of the present invention comprises monomer units having two or more hydroxyl groups. A particulate polymer containing 0.05% by mass or more and 5% by mass or less is contained. Thus, by using a binder composition containing a particulate polymer containing a monomer unit having a plurality of hydroxyl groups at a specific ratio, a composition for a porous membrane having excellent stability under shear can be prepared. Can do. Moreover, the porous film formed using the said binder composition has little moisture content, and is excellent in durability in electrolyte solution.

  Here, in the binder composition for a nonaqueous secondary battery porous membrane according to the present invention, the monomer unit having two or more hydroxyl groups has two or more hydroxyl groups and two or more radical polymerizable unsaturated bonds. It is preferable that it is a monomer unit derived from the monomer to have. A particulate polymer containing monomer units having two or more radically polymerizable unsaturated bonds in addition to two or more hydroxyl groups has high strength in the electrolyte and suppresses elution into the electrolyte. This is because the durability of the porous membrane in the electrolytic solution can be further improved.

  Furthermore, in the binder composition for a nonaqueous secondary battery porous membrane of the present invention, the particulate polymer preferably further contains 50% by mass to 95% by mass of a (meth) acrylic acid ester monomer unit. A particulate polymer containing a monomer unit derived from a (meth) acrylic acid ester within the above-mentioned range ensures a good balance between flexibility and adhesiveness, and further improves the durability of the porous membrane in the electrolytic solution. Because it can.

  In the binder composition for a nonaqueous secondary battery porous membrane of the present invention, the degree of swelling of the electrolytic solution of the particulate polymer is preferably greater than 1 and 3 times or less. If the degree of swelling of the electrolytic solution of the particulate polymer is within the above range, the durability of the porous membrane in the electrolytic solution is further improved, and lithium ion conductivity is ensured. This is because the electrical characteristics such as the low temperature output characteristics can be further improved.

  Moreover, the composition for non-aqueous secondary battery porous membranes of this invention is characterized by including one of the above-mentioned binder compositions for non-aqueous secondary battery porous membranes and non-conductive particles. The composition for porous membranes containing any of the binder compositions described above is excellent in stability under shear and hardly aggregates during the formation of the porous membrane. And the porous film which is low in water | moisture content and excellent in durability is obtained by using the composition for porous films containing any binder composition mentioned above for formation of a porous film.

  The porous membrane for a non-aqueous secondary battery of the present invention is formed from the above-described composition for a porous membrane of a non-aqueous secondary battery. The porous film has a low moisture content and excellent durability in an electrolytic solution.

  The nonaqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution, and the nonaqueous secondary battery described above is formed on the surface of at least one battery member selected from the group consisting of the positive electrode, the negative electrode, and the separator. A porous membrane for a secondary battery is provided. The non-aqueous secondary battery is excellent in electrical characteristics.

According to the present invention, it is possible to form a porous film having excellent durability in an electrolytic solution and having a low water content, and it is possible to improve the stability of the composition for porous film under shear. A binder composition for an aqueous secondary battery porous membrane can be provided.
Further, according to the present invention, a composition for a porous membrane of a nonaqueous secondary battery that is excellent in durability in an electrolytic solution, can form a porous membrane with a low water content, and has excellent stability under shear. Things can be provided.
According to the present invention, it is possible to provide a porous film for a non-aqueous secondary battery that is excellent in durability in an electrolytic solution and has a low water content, and a non-aqueous secondary battery that is excellent in electrical characteristics.

Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for nonaqueous secondary battery porous membranes of the present invention is used as a material for preparing a nonaqueous secondary battery porous membrane composition. And the composition for non-aqueous secondary battery porous films of this invention is prepared using the binder composition for non-aqueous secondary battery porous films of this invention. Moreover, the porous film for nonaqueous secondary batteries of this invention is formed using the composition for nonaqueous secondary battery porous films of this invention. In addition, the non-aqueous secondary battery of the present invention is provided with the porous membrane for a non-aqueous secondary battery of the present invention on the surface of at least one battery member.

(Binder composition for nonaqueous secondary battery porous membrane)
The binder composition of the present invention is a composition containing a particulate polymer having binding ability and a dispersion medium such as water, and optionally containing other components. And the said particulate polymer is characterized by including 0.05 mass% or more and 5 mass% or less of monomer units which have a 2 or more hydroxyl group.
In the present invention, “comprising a monomer unit” means “a monomer-derived structural unit is contained in a polymer obtained using the monomer”.
And the composition for porous films containing the binder composition of this invention is excellent in stability under shear. Moreover, the porous film formed using the binder composition for porous films of this invention is excellent in durability, and its water content is low. And the said porous film can exhibit the electrical property excellent in the non-aqueous secondary battery.

<Particulate polymer>
The particulate polymer ensures the strength of the obtained porous film and holds the components contained in the porous film so as not to be detached from the porous film.
Here, normally, the particulate polymer is not a water-soluble polymer but is present in the form of particles in an aqueous medium, and is contained in the porous film while maintaining the particle shape.
The particulate polymer contains 0.05% by mass or more and 5% by mass or less of a monomer unit having two or more hydroxyl groups, and optionally a (meth) acrylic acid ester monomer and other monomer units. including.
In the present invention, “(meth) acryl” refers to acryl and / or methacryl.

[Monomer unit having two or more hydroxyl groups]
The monomer having two or more hydroxyl groups that can form a monomer unit having two or more hydroxyl groups has two or more hydroxyl groups in the molecule and can be copolymerized with other monomers. Any monomer having at least one structure is not particularly limited. A particulate polymer containing a monomer unit having two or more hydroxyl groups and containing a monomer unit derived from the monomer is prepared using a larger amount of a monomer having one hydroxyl group. Compared with the particulate polymer, the polymerization is easy, and the stability of the composition for porous membrane under shear and the durability of the porous membrane in the electrolyte can be improved in a balanced manner.
In addition, the monomer which has two or more hydroxyl groups can be used individually by 1 type or in combination of 2 or more types.

Then, from the viewpoint of increasing the strength of the particulate polymer in the electrolytic solution, suppressing the elution of the components into the electrolytic solution, and further improving the durability of the porous membrane, the single polymer having two or more hydroxyl groups. As the monomer, a monomer having two or more hydroxyl groups and two or more radical polymerizable unsaturated bonds (such as a radical polymerizable carbon-carbon double bond) is preferable.
Furthermore, from the viewpoint of ensuring the strength and polymerizability of the obtained particulate polymer in the electrolytic solution, a compound having a plurality of glycidyl groups and an epoxy ester of an ethylenically unsaturated carboxylic acid are preferred, and ethylene glycol diglycidyl ether・ (Meth) acrylic acid adduct, propylene glycol diglycidyl ether ・ (Meth) acrylic acid adduct, tripropylene glycol diglycidyl ether ・ (Meth) acrylic acid adduct, neopentyl glycol diglycidyl ether ・ (meth) acrylic acid More preferred are epoxy esters of alkylene glycol diglycidyl ether and (meth) acrylic acid, such as adducts and 1,6-hexanediol diglycidyl ether / (meth) acrylic acid adducts. From the same viewpoint, among these, ethylene glycol diglycidyl ether / (meth) acrylic acid adduct, propylene glycol diglycidyl ether / (meth) acrylic acid adduct, tripropylene glycol diglycidyl ether / (meth) acrylic acid adduct Is more preferable.

In addition, from the viewpoint of reducing the water content of the porous film obtained using the particulate polymer, the monomer having two or more hydroxyl groups, such as ethylene glycol diglycidyl ether / methacrylic acid adduct, A compound having a plurality of glycidyl groups and an epoxy ester (methacrylic acid adduct) of methacrylic acid are preferred.
The compound having a plurality of glycidyl groups and the above compound such as an epoxy ester of (meth) acrylic acid can be produced by a known method.

  The content ratio of the monomer unit having two or more hydroxyl groups in the particulate polymer needs to be 0.05% by mass or more and 5% by mass or less, preferably 0.1% by mass or more, and more. Preferably it is 0.2 mass% or more, More preferably, it is 0.5 mass% or more, Preferably it is 4 mass% or less, More preferably, it is 3 mass% or less. When the content ratio of the monomer unit having two or more hydroxyl groups is less than 0.05% by mass, the dispersibility of the particulate polymer in the binder composition is impaired, and the composition for a porous membrane containing the binder composition The stability of the object under shear cannot be ensured, and in addition, the strength of the porous film and the electrical characteristics of the secondary battery are reduced. On the other hand, if the content of the monomer unit having two or more hydroxyl groups exceeds 5% by mass, the amount of moisture brought into the porous film increases, and the electrical characteristics such as the self-discharge characteristics of the secondary battery decrease. To do. Furthermore, the stability of the particulate polymer is impaired, and the stability under shearing of the porous membrane composition cannot be ensured.

[(Meth) acrylic acid ester monomer unit]
Examples of the (meth) acrylate monomer that can form a (meth) acrylate monomer unit include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, Alkyl acrylates such as isobutyl acrylate, n-pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; Methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate Relate, t-butyl methacrylate, isobutyl methacrylate, n-pentyl methacrylate, isopentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n-tetradecyl methacrylate, stearyl methacrylate Methacrylic acid alkyl esters such as glycidyl methacrylate; and the like. Among these, 2-ethylhexyl acrylate is preferred from the viewpoint of appropriate swelling of the particulate polymer in the electrolytic solution and improving the durability of the porous film in the electrolytic solution and the electrical characteristics of the secondary battery. Ethyl acrylate and butyl acrylate are preferable, and 2-ethylhexyl acrylate is more preferable from the viewpoint of reducing the water content in the porous film and improving the self-discharge characteristics and low-temperature output characteristics of the lithium ion secondary battery. These can be used alone or in combination of two or more.

  The content ratio of the (meth) acrylic acid ester monomer unit in the particulate polymer is preferably 50% by mass or more, more preferably 55% by mass or more, particularly preferably 60% by mass or more, and preferably 95% by mass. % Or less, more preferably 90% by mass or less, and particularly preferably 85% by mass or less. When the content ratio of the (meth) acrylic acid ester monomer unit is 50% by mass or more, the flexibility of the particulate polymer is improved, and when it is 95% by mass or less, the adhesiveness of the particulate polymer is ensured. can do. Therefore, when the content ratio of the (meth) acrylic acid ester monomer unit is within the above range, the strength of the porous film in the electrolytic solution is further increased, and the electrical characteristics of the lithium ion secondary battery are further improved. be able to.

[Other monomer units]
The particulate polymer may further contain a monomer unit other than the above-described monomer unit having two or more hydroxyl groups and a (meth) acrylate monomer unit. Such other monomer units are not particularly limited, and examples thereof include aromatic vinyl monomer units and aliphatic conjugated diene monomer units.
Examples of the aromatic vinyl monomer that can form an aromatic vinyl monomer unit include styrene, styrene sulfonic acid and salts thereof (for example, sodium styrene sulfonate) and the like.
Examples of the aliphatic conjugated diene monomer that can form an aliphatic conjugated diene monomer unit include isoprene and 1,3-butadiene.
Among these, from the viewpoint of suppressing excessive swelling of the particulate polymer in the electrolytic solution and ensuring the durability of the porous film in the electrolytic solution, an aromatic vinyl monomer is preferable, and styrene, styrene Sodium sulfonate is more preferred.

  Although the content rate of the other monomer unit mentioned above in a particulate polymer is not specifically limited, Preferably it is 50 mass% or less. And when a particulate polymer contains an aromatic vinyl monomer unit as another monomer unit, for example, the content rate of an aromatic vinyl monomer unit becomes like this. Preferably it is 4 mass% or more, More preferably, it is 15 mass % Or more, particularly preferably 18% by mass or more, preferably 50% by mass or less, more preferably 40% by mass or less, and particularly preferably 25% by mass or less. When the content ratio of the aromatic vinyl monomer unit is within the above range, excessive swelling of the particulate polymer in the electrolytic solution is suppressed, and the monomer unit having two or more hydroxyl groups and ( The properties of the particulate polymer derived from the (meth) acrylate monomer unit can be sufficiently exhibited.

  In the particulate polymer, the content ratio of the hydrophilic group-containing monomer units other than the above-described monomer units having two or more hydroxyl groups is preferably less than 5% by mass, more preferably less than 1% by mass. More preferably, it is less than 0.1% by mass, and particularly preferably 0% by mass. If the content ratio of the hydrophilic group-containing monomer unit is less than 5% by mass, the composition for a porous membrane containing the binder composition of the present invention is excellent in stability under shear, and for the porous membrane. The porous film formed using the composition is excellent in durability in the electrolytic solution and has a low water content. Here, examples of the hydrophilic group include a hydroxyl group, a carboxyl group, and a phosphoric acid group.

[Preparation of particulate polymer]
And a particulate polymer is prepared by superposing | polymerizing the monomer composition containing the monomer mentioned above. Here, the content ratio of each monomer in the monomer composition is usually the same as the content ratio of the monomer units in the desired particulate polymer.
The polymerization mode of the particulate polymer is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method may be used. As the polymerization reaction, addition polymerization such as ionic polymerization, radical polymerization, and living radical polymerization can be used. And generally used emulsifiers, dispersants, polymerization initiators, polymerization aids and the like used for the polymerization can be used, and the amount used is also generally used.

[Electrolytic solution swelling degree of particulate polymer]
In the present invention, “the degree of swelling of the electrolytic solution of the particulate polymer” refers to the weight after immersion when a film (binder film) formed from the particulate polymer is immersed in a specific electrolytic solution under predetermined conditions. It can be obtained as a value (times) divided by the previous weight. Specifically, a binder film is formed using the method described in the examples of the present specification, and the measurement method described in the examples is used. To measure.
Here, the degree of swelling of the electrolytic solution of the particulate polymer is preferably more than 1 time, preferably 3 times or less, more preferably 2.5 times or less, and particularly preferably 2 times or less. When the degree of swelling of the electrolytic solution of the particulate polymer is 3 times or less, the elution of the particulate polymer into the electrolytic solution is suppressed, and the durability of the porous membrane in the electrolytic solution can be ensured. By being over twice, lithium ion conductivity in the secondary battery can be secured.
The degree of swelling of the electrolyte solution of the particulate polymer can be adjusted by changing the type and amount of the monomer used, for example, increasing the amount of aromatic vinyl monomer such as styrene, The degree of swelling of the electrolyte solution can be reduced by increasing the polymerization molecular weight by increasing the polymerization temperature or increasing the polymerization reaction time.

<Preparation of binder composition for nonaqueous secondary battery porous membrane>
The method for preparing the binder composition is not particularly limited. For example, when the particulate polymer is prepared in an aqueous medium and the particulate polymer is obtained as an aqueous dispersion, the particulate polymer is dispersed in water. The liquid may be used as it is as the binder composition, or any other component may be added to the aqueous dispersion of the particulate polymer to form the binder composition. Here, as other components, other components described in the section “Composition for non-aqueous secondary battery porous membrane” described later can be given.

(Composition for non-aqueous secondary battery porous membrane)
The composition for a nonaqueous secondary battery porous membrane of the present invention is a slurry composition in which the above-mentioned particulate polymer derived from the binder composition and nonconductive particles are dispersed in a dispersion medium such as water.
And the composition for porous films of this invention is excellent in stability under shear. In addition, the porous film formed using the composition for porous film has a low water content and is excellent in durability in the electrolytic solution.

<Non-conductive particles>
Non-conductive particles have non-conductivity and do not dissolve in a dispersion medium such as water used in the composition for porous membranes and the electrolyte of the secondary battery, and the shape is maintained in them. Particles. And since nonelectroconductive particle is electrochemically stable, it exists stably in a porous film under the use environment of a secondary battery. Since the porous membrane composition contains non-conductive particles, the network structure of the obtained porous membrane is moderately clogged, lithium dendrites and the like are prevented from penetrating the porous membrane, and the short circuit of the electrode is suppressed. This is because it can be made even more certain. As non-conductive particles, for example, various inorganic particles and organic particles can be used.

Examples of inorganic particles include oxide particles such as aluminum oxide (alumina), silicon oxide, magnesium oxide, titanium oxide, BaTiO ₂ , ZrO, and alumina-sili force composite oxide, and nitride particles such as aluminum nitride and boron nitride. And covalently bonded crystal particles such as silicon and diamond, sparingly soluble ion crystal particles such as barium sulfate, calcium fluoride and barium fluoride, and clay fine particles such as talc and montmorillonite.
Organic particles include, for example, polyethylene, polystyrene, polydivinylbenzene, styrene-divinylbenzene copolymer cross-linked products, and various cross-linking heights such as polyimide, polyamide, polyamideimide, melamine resin, phenol resin, and benzoguanamine-formaldehyde condensate. Examples thereof include molecular particles and heat-resistant polymer particles such as polysulfone, polyacrylonitrile, polyaramid, polyacetal, and thermoplastic polyimide. Here, the organic particles are different from the above-mentioned particulate polymer in that the particulate polymer has binding ability, whereas the organic particles do not have binding ability.

Among these, from the viewpoint of improving the durability of the porous film and the electrical characteristics of the secondary battery including the porous film, the nonconductive particles are preferably inorganic particles, and aluminum oxide (alumina) is more preferable.
In addition, the particle size of nonelectroconductive particle is not specifically limited, It can be made to be the same as that of the nonelectroconductive particle conventionally used.

<Combination ratio of non-conductive particles and binder composition>
The compounding ratio of the non-conductive particles and the binder composition in the porous film composition is not particularly limited. For example, in the composition for a porous membrane, the amount of the particulate polymer is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, particularly preferably 3 parts by mass, per 100 parts by mass of the non-conductive particles. The binder composition is contained in an amount of 25 parts by mass or less, more preferably 20 parts by mass or less, further preferably 18 parts by mass or less, and particularly preferably 15 parts by mass or less. If the blending amount of the particulate polymer is 0.1 parts by mass or more per 100 parts by mass of the non-conductive particles, the adhesion between the porous membrane and the battery member is ensured, and the durability of the porous membrane in the electrolytic solution is ensured. If it is 25 parts by mass or less, the amount of moisture brought into the secondary battery due to the particulate polymer can be reduced, and the electrical characteristics of the secondary battery can be improved. Moreover, the stability under shear of the composition for porous membranes can also be improved.

<Other ingredients>
The composition for porous films may contain other arbitrary components in addition to the components described above. The optional component is not particularly limited as long as it does not have an excessively unfavorable effect on the battery reaction in the secondary battery using the porous film. Further, the kind of the arbitrary component may be one kind or two or more kinds.
Examples of the optional component include a wetting agent, a leveling agent, an electrolytic solution decomposition inhibitor, and a water-soluble polymer.

[Water-soluble polymer]
Among the other components described above, the porous membrane composition preferably contains a water-soluble polymer. When the porous membrane composition, which is an aqueous slurry composition, contains a water-soluble polymer, the viscosity of the porous membrane composition can be increased and adjusted to be easy to apply. In addition, since the water-soluble polymer has a binding property and an electrolytic solution resistance, in the secondary battery, the components in the porous film are bound to each other by the particulate polymer, and the porous film and the battery member It can play a role of assisting adhesion. Therefore, the durability of the porous membrane in the electrolytic solution can be further improved by using the water-soluble polymer.
Here, a substance in the present invention is “water-soluble” means that an insoluble content is less than 1.0% by mass when 0.5 g of the substance is dissolved in 100 g of water at 25 ° C. Say. A substance whose solubility changes depending on the pH of water is considered to be “water-soluble” if it falls under the above-mentioned “water-soluble” at least at any pH.
Examples of the water-soluble polymer include natural polymers, semi-synthetic polymers, and synthetic polymers.

[Natural polymer]
Examples of natural polymers include plant- or animal-derived polysaccharides and proteins, fermentation-treated products of these microorganisms, and heat-treated products thereof.
These natural polymers can be classified into plant-based natural polymers, animal-based natural polymers, and microorganism-produced natural polymers.
Examples of plant-based natural polymers include gum arabic, gum tragacanth, galactan, guar gum, carob gum, caraya gum, carrageenan, pectin, cannan, quince seed (malmello), arche colloid (gasso extract), starch (rice, corn, potato, wheat) Etc.) and glycyrrhizin. Examples of animal natural polymers include collagen, casein, albumin, and gelatin. Examples of the microorganism-produced natural polymer include xanthan gum, dextran, succinoglucan, and bullulan.

[Semi-synthetic polymer]
Examples of the semisynthetic polymer include cellulose semisynthetic polymers. The cellulose semisynthetic polymer can be classified into nonionic cellulose semisynthetic polymer, anionic cellulose semisynthetic polymer and cationic cellulose semisynthetic polymer.

  Nonionic cellulose-based semisynthetic polymers include, for example, alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, and microcrystalline cellulose; hydroxyethyl cellulose, hydroxybutyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxy Examples thereof include hydroxyalkylcelluloses such as propylmethylcellulose stearoxy ether, carboxymethylhydroxyethylcellulose, alkylhydroxyethylcellulose, and nonoxynylhydroxyethylcellulose.

  Examples of the anionic cellulose semisynthetic polymer include substituted products obtained by substituting the above nonionic cellulose semisynthetic polymer with various derivative groups and salts thereof (sodium salt, ammonium salt, etc.). Specific examples include sodium cellulose sulfate, methyl cellulose, methyl ethyl cellulose, ethyl cellulose, carboxymethyl cellulose (CMC) and salts thereof.

  Examples of the cationic cellulose semisynthetic polymer include low nitrogen hydroxyethylcellulose dimethyl diallylammonium chloride (polyquaternium-4), O- [2-hydroxy-3- (trimethylammonio) propyl] hydroxyethylcellulose (polyquaternium-10). ), O- [2-hydroxy-3- (lauryldimethylammonio) propyl] hydroxyethylcellulose chloride (polyquaternium-24).

[Synthetic polymer]
Synthetic polymers include polyacrylates such as sodium polyacrylate, polyvinyl alcohol, polyethylene oxide, polyvinylpyrrolidone, acrylic acid or copolymers of acrylate and vinyl alcohol, maleic anhydride, maleic acid or fumaric acid. Completely or partially saponified copolymer of acid and vinyl acetate, modified polyvinyl alcohol, modified polyacrylic acid, polyethylene glycol, polycarboxylic acid, ethylene-vinyl alcohol copolymer, vinyl acetate polymer, carboxylic acid group introduced Acrylamide polymer prepared.

Among these water-soluble polymers, from the viewpoint of imparting heat resistance to the porous membrane and suppressing heat shrinkage of an organic separator such as polypropylene, carboxymethyl cellulose, its salt, and an acrylamide polymer into which a carboxylic acid group has been introduced are used. preferable. Furthermore, an acrylamide polymer into which a carboxylic acid group is introduced is particularly preferred from the viewpoint of reducing the amount of moisture brought into the secondary battery and improving the electrical characteristics.
The blending amount of the water-soluble polymer in the porous membrane composition is preferably 0.5 parts by mass or more, more preferably 3 parts by mass or more, preferably 15 parts by mass per 100 parts by mass of the non-conductive particles. Part or less, more preferably 10 parts by weight or less. When the blending amount of the water-soluble polymer is within the above range, an appropriate viscosity is imparted to the porous membrane composition, and the durability of the obtained porous membrane can be improved.

<Preparation of composition for nonaqueous secondary battery porous membrane>
The method for preparing the composition for a porous membrane is not particularly limited, but usually, the binder composition for a porous membrane described above, non-conductive particles, water, and any components used as necessary are mixed. Is obtained. The mixing method is not particularly limited, but in order to disperse each component efficiently, mixing is performed using a disperser as a mixing device.
The disperser is preferably an apparatus capable of uniformly dispersing and mixing the above components. Examples include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer. Among them, a high dispersion apparatus such as a bead mill, a roll mill, or a fill mix is particularly preferable because a high dispersion share can be added.

  And normally, what is necessary is just to arbitrarily set the solid content density | concentration of the composition for porous films in the range which the composition for porous films has the viscosity of the range which does not impair workability | operativity, when manufacturing a porous film. Specifically, the solid content concentration of the composition for a porous membrane can usually be 10 to 50% by mass.

(Porous membrane for non-aqueous secondary batteries)
For example, the above-described composition for a secondary battery porous membrane is applied to the surface of an appropriate base material to form a coating film, and the formed coating film is dried to provide a non-aqueous secondary battery on the base material. A porous film can be formed. This porous film has a low water content and is excellent in durability in an electrolytic solution, and the nonaqueous secondary battery including the porous film is excellent in electrical characteristics such as self-discharge characteristics and low-temperature output characteristics. .

Here, the base material which apply | coats the composition for porous films is a member used as the object which forms the coating film of the composition for porous films. There is no limitation on the substrate, for example, a coating film of the composition for porous film is formed on the surface of the release substrate, the coating film is dried to form a porous film, and the release substrate is peeled off from the porous film. It may be. Thus, the porous film peeled off from the mold release substrate can be used for a secondary battery as a self-supporting film.
However, it is preferable to use a battery member as the base material from the viewpoint of improving the production efficiency by omitting the step of peeling the porous film. Specific examples of such battery members include separators and electrodes. The porous film provided on the separator and the electrode can be suitably used as a protective layer for improving the heat resistance and strength.

<Separator>
Although it does not specifically limit as a separator, Well-known separators, such as an organic separator, are mentioned. Here, the organic separator is a porous member made of an organic material. Examples of the organic separator include a microporous film or a nonwoven fabric containing a polyolefin resin such as polyethylene and polypropylene, an aromatic polyamide resin, and the like. A polyethylene microporous film and a nonwoven fabric are preferable. In addition, the thickness of an organic separator can be made into arbitrary thickness, and is 0.5 micrometer or more normally, Preferably it is 5 micrometers or more, and is 40 micrometers or less normally, Preferably it is 30 micrometers or less, More preferably, it is 20 micrometers or less.

<Electrode>
Although it does not specifically limit as an electrode (a positive electrode and a negative electrode), The electrode with which the electrode compound-material layer was formed on the electrical power collector is mentioned.
On current collector, electrode active material (positive electrode active material, negative electrode active material) in electrode mixture layer, binder for electrode mixture layer (binder for positive electrode mixture layer, binder for negative electrode mixture layer), and current collector As the method for forming the electrode mixture layer on the substrate, known methods can be used, and examples thereof include those described in JP2013-145663A.

<Method for forming porous film for non-aqueous secondary battery>
Examples of the method for forming the porous film on the battery member such as the separator and the electrode described above include the following methods.
1) A method of applying a composition for a porous membrane to the surface of a battery member (in the case of an electrode, the surface on the electrode mixture layer side, the same shall apply hereinafter), and then drying;
2) A method of drying a battery member after immersing it in the composition for a porous membrane;
3) A method for producing a porous film by applying the composition for porous film onto a release substrate and drying it, and transferring the obtained porous film to the surface of the battery member;
Among these, the method 1) is particularly preferable because the film thickness of the porous film can be easily controlled. Specifically, the method 1) includes a step of applying the porous membrane composition onto the battery member (application step), and drying the porous membrane composition applied onto the battery member to form a porous membrane. A process (porous film formation process) is provided.

In the coating process, the method for coating the porous membrane composition on the battery member is not particularly limited, and examples thereof include a doctor blade method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method. A method is mentioned. Of these, the gravure method is preferable in that a uniform porous film can be obtained.
In the porous film forming step, the method for drying the composition for the porous film on the battery member is not particularly limited, and a known method can be used, for example, drying with hot air, hot air, low-humidity air, vacuum drying, A drying method by irradiation with infrared rays or electron beams can be mentioned. The drying conditions are not particularly limited, but the drying temperature is preferably 50 to 150 ° C., and the drying time is preferably 5 to 30 minutes.

  In addition, the positive electrode, the negative electrode, and the separator may include components other than these battery members and the above-described porous film of the present invention as long as the effects of the present invention are not significantly impaired. For example, you may provide another layer between a battery member and the porous film of this invention as needed. In this case, the porous film of the present invention is indirectly provided on the surface of the battery member. Further, another layer may be provided on the surface of the porous membrane of the present invention.

  The thickness of the porous film formed on the substrate is preferably 0.01 μm or more, more preferably 0.1 μm or more, particularly preferably 1 μm or more, preferably 20 μm or less, more preferably 10 μm or less, particularly Preferably it is 5 micrometers or less. When the thickness of the porous film is 0.01 μm or more, the strength of the porous film can be sufficiently ensured, and when it is 20 μm or less, the diffusibility of the electrolytic solution is secured and the secondary film using the porous film is used. The low-temperature output characteristics of the battery can be improved.

(Non-aqueous secondary battery)
The non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolytic solution, and the above non-aqueous secondary battery is formed on the surface of at least one battery member selected from the group consisting of the positive electrode, the negative electrode, and the separator. A porous membrane for a battery is provided.
Since the nonaqueous secondary battery of the present invention includes the porous film for a nonaqueous secondary battery of the present invention, it is excellent in electrical characteristics such as self-discharge characteristics and low-temperature output characteristics.

<Positive electrode, negative electrode, separator, and porous membrane>
As the positive electrode, the negative electrode, the separator, and the porous film, the same materials as those mentioned in the section “Porous film for non-aqueous secondary battery” can be used, and the method of providing the porous film on the surface of the positive electrode, the negative electrode, and the separator Also, the methods mentioned in these sections can be adopted.

<Electrolyte>
As the electrolytic solution, an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used. As the supporting electrolyte, for example, a lithium salt is used in a lithium ion secondary battery. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li are preferable because they are easily dissolved in a solvent and exhibit a high degree of dissociation. In addition, electrolyte may be used individually by 1 type and may be used in combination of 2 or more types. Usually, the lithium ion conductivity tends to increase as the supporting electrolyte having a higher degree of dissociation is used, so that the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. For example, in a lithium ion secondary battery, 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. Moreover, you may use the liquid mixture of these solvents. Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. Usually, the lower the viscosity of the solvent used, the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted depending on the type of solvent.
The concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate. Moreover, you may add a known additive to electrolyte solution.

<Method for producing non-aqueous secondary battery>
A non-aqueous secondary battery, for example, stacks a positive electrode and a negative electrode through a separator, and rolls or folds it as necessary to put it in a battery container, and injects an electrolyte into the battery container and seals it. Can be manufactured. In addition, let at least 1 member be a member with a porous film among a positive electrode, a negative electrode, and a separator. Here, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like may be placed in the battery container as necessary to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.

Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto. In addition, unless otherwise indicated, the part and% in a present Example are a mass reference | standard.
In Examples and Comparative Examples, the degree of electrolyte swelling of particulate polymers was measured using the following method. The stability of the porous membrane composition under shear, the durability of the porous membrane in the electrolyte, the moisture content of the porous membrane, and the self-discharge characteristics and low-temperature output characteristics of the nonaqueous secondary battery are as follows. The method was evaluated.

<Electrolyte swelling degree of particulate polymer>
A binder composition for a nonaqueous secondary battery porous membrane (aqueous dispersion of particulate polymer) was applied to an electrolytic copper foil (Furukawa Electric NC-WS (registered trademark)) using a table coater, and 50 It was dried with a hot air drier at 20 ° C. for 20 minutes and 120 ° C. to prepare a 1 cm × 1 cm binder film (thickness: 500 μm), and the weight M0 was measured. Thereafter, the obtained film was immersed in an electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio), electrolyte: LiPF _{6 having a} concentration of 1 M) at 60 ° C. for 72 hours. The electrolyte solution on the surface of the film after immersion was wiped off, and the weight M1 was measured. And according to the following formula, electrolyte solution swelling degree was computed.
Electrolyte swelling degree = M1 / M0
<Stability of the porous membrane composition under shear>
The composition for porous membrane was applied on a separator (made of polyethylene) using a gravure roll (number of lines: 95) under the conditions of a conveyance speed of 10 m / min and a gravure rotation ratio of 100%, and the separator after application was cut out. The coating amount M0 (mg / cm ² ) per unit area was calculated. Moreover, 1 hour after application | coating, the application quantity M1 (mg / cm < ² >) was computed similarly. Then, a coating amount change rate ΔM (%) was calculated using an equation of ΔM = (| M0−M1 |) / M0 × 100 (%) and evaluated as follows. It shows that stability under the shear of the composition for porous films is so high that this value is small.
A: Application rate change rate ΔM is less than 5% B: Application rate change rate ΔM is 5% or more and less than 10% C: Application rate change rate ΔM is 10% or more and less than 20% D: Application rate change rate ΔM is 20% or more <Durability of porous membrane in electrolyte>
The separator with a porous membrane was cut out to 5 cm × 5 cm, the weight was measured, and the weight M0 of the porous membrane was calculated by subtracting the weight of the separator. Subsequently, the separator with a porous film cut out was immersed in an electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio), electrolyte: LiPF _{6 having a} concentration of 1 M) at 60 ° C. An ultrasonic vibration of 30 kHz was applied for 10 minutes. Thereafter, the separator with the porous film was taken out and dried in an atmosphere at 60 ° C. for 10 hours, and the weight M1 of the porous film after drying was calculated in the same manner as the weight M0. Then, the vibration dropout rate ΔM (%) was calculated using an equation of ΔM = {(M0−M1) / M0} × 100, and evaluated as follows. It shows that a porous film is excellent in durability in electrolyte solution, so that this value is small.
A: Vibration drop rate ΔM is less than 20% B: Vibration drop rate ΔM is 20% or more and less than 40% C: Vibration drop rate ΔM is 40% or more and less than 60% D: Vibration drop rate ΔM is 60% or more Water content>
A separator with a porous membrane was cut into 10 cm × 10 cm to obtain a test piece. This test piece is left for 24 hours at a temperature of 25 ° C. and a humidity of 50%, and then a test piece is obtained by a Karl Fischer method (JIS K-0068 (2001) water vaporization method, vaporization temperature 150 ° C.) using a coulometric titration moisture meter. The water content W (ppm) of was measured. The smaller this value, the smaller the water content in the porous film, and the smaller the amount of water brought into the secondary battery.
A: Water content W is 500 ppm or less B: Water content W is more than 500 ppm and 600 ppm or less C: Water content W is more than 600 ppm and 700 ppm or less D: Water content W is more than 700 ppm <Self-discharge characteristics>
The prepared secondary battery was allowed to stand for 24 hours in a 25 ° C. environment, and then charged and discharged with a 4.35 V, 0.1 C charge and a 2.75 V, 0.1 C discharge in a 25 ° C. environment. Was performed. Thereafter, the battery was charged at 4.35 V and 0.1 C, left as it was for 168 hours (7 days) at 60 ° C., and then the cell voltage V 1 (V) was measured at 25 ° C. The voltage drop ΔV (mV) was calculated using the equation: ΔV = {4.35−V1} × 1000 and evaluated as follows. It shows that it is excellent in the self-discharge characteristic (life characteristic), so that this value is small.
A: Voltage drop ΔV is 200 mV or less B: Voltage drop ΔV is more than 200 mV to 400 mV or less C: Voltage drop ΔV is more than 400 mV to 600 mV or less D: Voltage drop ΔV is more than 600 mV <Low-temperature output characteristics>
The fabricated secondary battery was allowed to stand for 24 hours in an environment of 25 ° C., and then charged with 4.2 V, 0.1 C, and 5 hours in an environment of 25 ° C., and the voltage V0 ( V) was measured. Thereafter, a discharge operation was performed at a discharge rate of 1 C in a −10 ° C. environment, and the voltage V2 (V) 15 seconds after the start of discharge was measured. The voltage change ΔV (mV) was calculated using the equation: ΔV = {V0−V2} × 1000, and evaluated as follows. It shows that it is excellent in low temperature output characteristics, so that this value is small.
A: Voltage change ΔV is 500 mV or less B: Voltage change ΔV is more than 500 mV and 700 mV or less C: Voltage change ΔV is more than 700 mV and 900 mV or less D: Voltage change ΔV is more than 900 mV

(Example 1)
<Preparation of binder composition for nonaqueous secondary battery porous membrane>
In a reactor equipped with a stirrer, 70 parts of ion exchange water, 0.15 part of sodium lauryl sulfate (“Emar (registered trademark) 2F” manufactured by Kao Chemical Co., Ltd.) as an emulsifier, and 0.5 part of ammonium persulfate are added. The gas phase portion was replaced with nitrogen gas, and the temperature was raised to 60 ° C.
On the other hand, in a separate container, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersant, and ethylene glycol diglycidyl ether / methacrylic acid of the following formula (I) as a monomer having two or more hydroxyl groups Acid adduct (manufactured by Kyoeisha Chemical Co., Ltd., “epoxy ester 40EM”, epoxy ester 1) 1.5 parts, (meth) acrylic acid ester monomer as 2-ethylhexyl acrylate (2-EHA) 78.5 parts, aromatic As a vinyl monomer, 20 parts of styrene (ST) was mixed to obtain a monomer composition.

This monomer composition was continuously added to the reactor over 4 hours for polymerization. During the addition, the reaction was carried out at 60 ° C. After completion of the addition, the reaction was further terminated by stirring at 70 ° C. for 3 hours to produce an aqueous dispersion (binder composition) containing a particulate polymer.
The electrolyte solution swelling degree of the obtained particulate polymer was measured. The results are shown in Table 1.

<Preparation of composition for nonaqueous secondary battery porous membrane>
6 parts of binder composition containing particulate polymer is introduced into 100 parts of alumina filler (Nippon Light Metal Co., Ltd., “LS256”) as non-conductive particles, and a carboxylic acid group is introduced as a thickener. 6 parts of the obtained acrylamide polymer (Arakawa Chemical Co., Ltd., “Polystron (registered trademark) 117”), polyethylene glycol type surfactant (San Nopco, “San Nopco (registered trademark) SN wet 366”) 0.2 part Were mixed to prepare a porous membrane composition.
Using the obtained porous membrane composition, the stability under shear was evaluated.

<Manufacture of porous membrane and separator with porous membrane>
An organic separator made of a polyethylene porous substrate (manufactured by Celgard, “2500”, thickness 25 μm) was prepared. The porous membrane composition obtained as described above was applied to one side of the prepared organic separator and dried at 60 ° C. for 10 minutes. This obtained the separator (thickness 27 micrometers) with a porous film.
Using the obtained separator with a porous membrane, the durability of the porous membrane in the electrolytic solution and the moisture content of the porous membrane were evaluated.

<Manufacture of negative electrode>
In a 5 MPa pressure vessel equipped with a stirrer, 33 parts of 1,3-butadiene, 3.5 parts of itaconic acid, ST63.5 parts, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and excess as a polymerization initiator. After 0.5 parts of potassium sulfate was added and sufficiently stirred, the polymerization was started by heating to 50 ° C. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain a mixture containing the binder for negative electrode mixture layer (SBR). After adding 5% sodium hydroxide aqueous solution to the mixture containing the binder for the negative electrode mixture layer and adjusting to pH 8, the unreacted monomer is removed by heating under reduced pressure, and then cooled to 30 ° C or lower. An aqueous dispersion containing a desired binder for the negative electrode mixture layer was obtained.
1 part of 2% aqueous solution of artificial graphite (average particle size: 15.6 μm) as a negative electrode active material and 2% aqueous solution of carboxymethyl cellulose sodium salt (manufactured by Nippon Paper Industries Co., Ltd., “MAC350HC”) as a water-soluble polymer And ion-exchanged water were mixed to prepare a solid content concentration of 68%, and further mixed at 25 ° C. for 60 minutes. Further, the solid concentration was adjusted to 62% with ion-exchanged water, and further mixed at 25 ° C. for 15 minutes. In the above mixed solution, 1.5 parts of the binder for the negative electrode mixture layer and ion exchange water are added in an amount corresponding to the solid content, adjusted so that the final solid content concentration is 52%, and further mixed for 10 minutes. . This was defoamed under reduced pressure to obtain a slurry composition for a secondary battery negative electrode having good fluidity.
The obtained negative electrode slurry composition was applied on a copper foil having a thickness of 20 μm, which was a current collector, with a comma coater so that the film thickness after drying was about 150 μm, and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a negative electrode raw material before pressing. The negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode mixture layer thickness of 80 μm (single-sided negative electrode).
Moreover, the same application | coating is implemented on the back surface of the negative electrode original fabric before the said press, a negative electrode compound material layer is formed on both surfaces, it rolls with a roll press, and the negative electrode after the press whose thickness of a negative electrode compound material layer is 80 micrometers each (Double-sided negative electrode) was obtained.

<Production of positive electrode>
100 parts of LiCoO ₂ having a volume average particle diameter of 12 μm as a positive electrode active material, ₂ parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., “HS-100”) as a conductive material, polyfluorination as a binder for a positive electrode mixture layer 2 parts of vinylidene (manufactured by Kureha, “# 7208”) in an amount corresponding to the solid content and N-methylpyrrolidone were mixed to make the total solid content concentration 70%. These were mixed with a planetary mixer to prepare a positive electrode slurry composition.
The obtained positive electrode slurry composition was applied onto a 20 μm-thick aluminum foil as a current collector by a comma coater so that the film thickness after drying was about 150 μm and dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material before pressing. The positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a positive electrode mixture layer thickness of 80 μm (single-sided positive electrode).
In addition, the same application is performed on the back surface of the positive electrode original fabric before pressing, a positive electrode mixture layer is formed on both surfaces, and rolling is performed by a roll press. (Double-sided positive electrode) was obtained.

<Manufacture of lithium ion secondary batteries>
The single-sided positive electrode obtained above was cut out to 5 cm × 15 cm, and a separator with a porous film cut out to 6 cm × 16 cm was disposed thereon (on the side of the composite layer) so that the porous film was opposed to the single-sided positive electrode, and A double-sided negative electrode cut out to 5.5 cm × 15.5 cm was placed on the organic separator of the separator with a porous film, and a laminate A was obtained. On the double-sided negative electrode side of the laminate A, a separator with a porous film cut out to 6 cm × 16 cm was disposed so that the organic separator faces the double-sided negative electrode. And the double-sided positive electrode cut out to 5 cm x 15 cm is piled up on the porous film of the separator with a porous film, and then the separator with the porous film cut out to 6 cm x 16 cm is placed on the double-sided positive electrode. Arranged. Finally, the single-sided negative electrode cut out to 5.5 cm x 5.5 cm was laminated | stacked so that the negative electrode compound material layer might face the organic separator of the separator with a porous film, and the laminated body B was obtained. This laminate B is wrapped in an aluminum wrapping case as a battery case, and an electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 (volume ratio)), electrolyte: LiPF _{6 having a} concentration of 1M. ) Was injected so that no air remained. Furthermore, after heat sealing at 150 ° C. and closing the aluminum packaging outer packaging, the obtained battery outer packaging was flat-pressed at 100 ° C. for 2 minutes at 100 kgf to produce a 1000 mAh stacked lithium ion secondary battery. did.
Using the obtained lithium ion secondary battery, self-discharge characteristics and low-temperature output characteristics were evaluated. The results are shown in Table 1.

(Examples 2 and 3)
A binder composition, a composition for a porous film, and a porous film were prepared in the same manner as in Example 1 except that the amount of epoxy ester 1 and ST used was changed as shown in Table 1 when preparing the binder composition for the porous film. A separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 1.

(Examples 4 and 5)
When preparing a binder composition for a porous membrane, the propylene glycol diglycidyl ether / acrylic acid adduct of the following formula (II) is used instead of the epoxy ester 1 as a monomer having two or more hydroxyl groups (Kyoeisha Chemical Co., Ltd.) Except for using "Epoxy ester 70PA", Epoxy ester 2), Tripropylene glycol diglycidyl ether / acrylic acid adduct (Kyoeisha Chemical Co., "Epoxy ester 200PA", Epoxy ester 3) of the following formula (III) Produced a binder composition, a porous membrane composition, a separator with a porous membrane, a negative electrode, a positive electrode, and a lithium ion secondary battery in the same manner as in Example 1, and evaluated the same items. The results are shown in Table 1.

(Examples 6 and 7)
Except that the amount of 2-EHA and ST used was changed as shown in Table 1 when preparing the binder composition for the porous membrane, the same as in Example 1, the binder composition, the porous membrane composition, and the porous membrane A separator, a negative electrode, a positive electrode, and a lithium ion secondary battery were manufactured, and the same items were evaluated. The results are shown in Table 1.

(Examples 8 and 9)
Example 1 and Example 1 except that butyl acrylate (BA) and ethyl acrylate (EA) were used in place of 2-EHA as the (meth) acrylic acid ester monomer when preparing the binder composition for the porous membrane, respectively. Similarly, a binder composition, a porous membrane composition, a separator with a porous membrane, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced, and the same items were evaluated. The results are shown in Table 1.

(Comparative Examples 1 and 2)
Except having changed the usage-amount of epoxy ester 1, EA, and ST as shown in Table 1 at the time of preparation of the binder composition for porous membranes (the usage-amount of the epoxy ester 1 in the comparative example 1), and Example 9 Similarly, a binder composition, a porous membrane composition, a separator with a porous membrane, a negative electrode, a positive electrode, and a lithium ion secondary battery were produced, and the same items were evaluated. The results are shown in Table 1.

From Examples 1 to 9 in Table 1 and Comparative Examples 1 and 2, Examples 1 to 9 using a particulate polymer containing monomer units having two or more hydroxyl groups at a specific ratio are porous membranes. It can be seen that the composition for use is excellent in stability under shear, and the porous membrane is excellent in durability in the electrolytic solution and has a low water content. In addition, it turns out that Examples 1-9 are excellent in the self-discharge characteristic and low-temperature output characteristic of a lithium ion secondary battery.
Further, from Examples 1 to 5 in Table 1, the moisture content of the porous membrane is reduced by changing the content ratio and type of the monomer unit having two or more hydroxyl groups, and the lithium ion secondary battery It can be seen that the self-discharge characteristics can be improved.
And from Example 1, 6-9 of Table 1, the water content of a porous membrane is reduced by changing the content rate and kind of (meth) acrylic acid ester monomer unit, and the electrolyte solution of a porous membrane It can be seen that the durability in the battery and the self-discharge characteristics and low-temperature output characteristics of the lithium ion secondary battery can be improved.

ADVANTAGE OF THE INVENTION According to this invention, the binder for nonaqueous secondary battery porous membranes which can form the porous membrane which is excellent in durability, and can also improve the stability under the shear of the composition for porous membranes is provided. be able to.
Moreover, according to this invention, the composition for non-aqueous secondary battery porous films which can form the porous film which is excellent in stability under shear and excellent in durability can be provided.
And according to this invention, the nonaqueous secondary battery provided with the porous film for nonaqueous secondary batteries excellent in durability and the said porous film for nonaqueous secondary batteries can be provided.

Claims (7)

  A binder composition for a nonaqueous secondary battery porous membrane, comprising a particulate polymer containing 0.05% by mass or more and 5% by mass or less of a monomer unit having two or more hydroxyl groups.   The monomer unit having the two or more hydroxyl groups is a monomer unit derived from a monomer having two or more hydroxyl groups and two or more radical polymerizable unsaturated bonds. A binder composition for a nonaqueous secondary battery porous membrane.   The binder composition for a nonaqueous secondary battery porous film according to claim 1 or 2, wherein the particulate polymer further contains 50% by mass or more and 95% by mass or less of a (meth) acrylic acid ester monomer unit.   The binder composition for a nonaqueous secondary battery porous membrane according to any one of claims 1 to 3, wherein the degree of swelling of the electrolytic solution of the particulate polymer is greater than 1 and 3 times or less.   The composition for non-aqueous secondary battery porous films containing the binder composition for non-aqueous secondary battery porous films in any one of Claims 1-4, and a nonelectroconductive particle.   A porous film for a non-aqueous secondary battery, formed from the composition for a non-aqueous secondary battery porous film according to claim 5. A positive electrode, a negative electrode, a separator, and an electrolyte solution,
A non-aqueous secondary battery comprising the porous film for a non-aqueous secondary battery according to claim 6 on the surface of at least one battery member selected from the group consisting of the positive electrode, the negative electrode, and the separator.