KR102090111B1 - Method for producing porous membrane separator for lithium ion secondary batteries, and method for producing laminate for lithium ion secondary batteries - Google Patents

Abstract

A slurry composition for a porous membrane containing at least one kind of low-molecular-weight compound selected from the group consisting of non-conductive particles, water-soluble polymer compounds, water, and ammonia and amine compounds is applied to at least one side of the separator substrate and dried to form a porous membrane. A process for obtaining a lithium ion secondary battery comprising a step of applying a slurry composition for an adhesive layer containing a particulate polymer and water having a glass transition temperature of 10 ° C or more and 110 ° C or less on the porous membrane and drying it to obtain an adhesive layer. Method for manufacturing a porous membrane separator.

Description

Method for manufacturing a porous membrane separator for a lithium ion secondary battery, and a method for producing a laminate for a lithium ion secondary battery {METHOD FOR PRODUCING POROUS MEMBRANE SEPARATOR FOR LITHIUM ION SECONDARY BATTERIES, AND METHOD FOR PRODUCING LAMINATE FOR LITHIUM ION SECONDARY BATTERIES}

The present invention relates to a method for producing a porous membrane separator for a lithium ion secondary battery, and a method for producing a laminate for a lithium ion secondary battery.

Among the batteries being put into practical use, lithium ion secondary batteries show high energy density, and are particularly used for small electronics. Further, in addition to small-sized applications, development for automobiles is also expected. Such a lithium ion secondary battery generally includes a positive electrode and a negative electrode, and a separator and a non-aqueous electrolyte.

When the battery is operated, heat is generally generated. As a result, a separator made of a stretched resin such as stretched polyethylene resin is also heated. The separator made of the stretched resin is likely to shrink even at a temperature of 150 ° C. or less, and is likely to cause a short circuit in the battery. Therefore, in order to solve such a problem, a separator having a porous membrane containing non-conductive particles such as inorganic fillers (hereinafter sometimes referred to as "porous membrane separator" as appropriate) has been proposed (Patent Document 1). . Normally, since the porous membrane is unlikely to shrink due to heat, the risk of short circuit is much reduced in a battery using a porous membrane separator, and a significant improvement in safety is expected. In addition, since the porous membrane has pores, the electrolyte may penetrate into the porous membrane, and the battery reaction is not inhibited by the porous membrane.

Moreover, it has been proposed to form an adhesive layer on the porous membrane (Patent Document 2). When the adhesive layer is formed on the porous membrane, it is possible to improve the adhesion between the porous membrane and the electrode. For this reason, since the porous film can be stably fixed to the electrode, for example, shrinkage due to heat of the porous film can be further suppressed, and safety can be further improved.

In addition, techniques such as patent documents 3 and 4 are also known.

International Publication No. 2009/096528 Japanese Patent Publication No. 4806735 Japanese Patent Publication No. 4657019 Japanese Patent Application Publication No. 2010-9940

The porous membrane can be produced, for example, by applying a slurry composition containing non-conductive particles and a solvent and, if necessary, an optional component on a separator substrate, and drying the solvent.

In addition, the adhesive layer can be produced, for example, by applying a slurry composition containing a polymer and a solvent and, if necessary, an optional component on a porous membrane, and drying the solvent.

Conventionally, it was common to use an organic solvent as a solvent for the slurry composition for producing the porous membrane and the adhesive layer. However, in the manufacturing method using an organic solvent, there is a problem that the cost of recycling an organic solvent is required, or that safety is required by using an organic solvent. So, in recent years, the manufacturing method using the aqueous slurry composition containing water as a solvent is considered.

However, when both the porous membrane and the adhesive layer were made of an aqueous slurry composition, the porous membrane might be melted by the slurry composition for the adhesive layer. Specifically, the porous membrane formed by applying and drying the aqueous slurry composition contains a water-soluble component. Therefore, in order to form an adhesive layer, when an aqueous slurry composition is applied on the porous membrane, the water-soluble component of the porous membrane elutes into the solvent contained in the applied slurry composition, and as a result, the porous membrane may be melted. . When the porous membrane melts, the adhesion between the porous membrane and the adhesive layer decreases, and thus the adhesiveness of the porous membrane separator to the electrode tends to decrease. Therefore, it has been desired to develop a manufacturing method in which the porous membrane and the adhesive layer can be produced using an aqueous slurry composition, and the porous membrane is not easily dissolved in the slurry composition for the adhesive layer.

Moreover, generally, the separator has a sheet-like shape. Moreover, these sheet-like separators are usually transported or stored in a rolled state. However, when the separator causes blocking, overlapping separators may adhere to each other in the case of being rolled, and handling properties may be impaired. Here, in general, the more the porous membrane separator having excellent adhesion to the electrode tends to be prone to blocking. Therefore, blocking is particularly likely to occur in a porous membrane separator provided with an adhesive layer. Therefore, development of a method for producing a porous membrane separator having both excellent adhesion and blocking resistance has been desired.

The present invention was devised in view of the above problems, and is a method for manufacturing a porous membrane separator for a lithium ion secondary battery having a porous membrane and an adhesive layer, wherein the porous membrane and the adhesive layer are formed using an aqueous slurry composition containing water. It is an object of the present invention to provide a production method in which a porous membrane separator that can be manufactured, is poorly soluble in a slurry composition for an adhesive layer, and is excellent in both adhesion to an electrode and blocking resistance.

Moreover, this invention aims at providing the manufacturing method of the laminated body for lithium ion secondary batteries provided with the porous membrane separator manufactured by the manufacturing method of the porous membrane separator of this invention.

The present inventors, as a result of diligent investigation to solve the above problems, a non-conductive particle, a water-soluble polymer compound, water, and a slurry composition for a porous membrane containing at least one low molecular compound selected from the group consisting of ammonia and amine compounds A step of applying a porous film on at least one side of a separator substrate and drying it to obtain a porous film, and a slurry composition for an adhesive layer containing particulate polymer and water having a glass transition temperature in a predetermined range is coated on the porous film and dried to obtain an adhesive layer The present invention was completed by finding out that a porous membrane separator excellent in both adhesiveness and blocking resistance can be produced while suppressing melting of the porous membrane in the slurry composition for an adhesive layer by a manufacturing method including a step.

That is, the present invention is as follows.

[1] A slurry composition for a porous membrane containing at least one kind of low-molecular compound selected from the group consisting of non-conductive particles, water-soluble polymer compounds, water, and ammonia and amine compounds is applied to at least one side of the separator substrate and dried. To obtain a porous membrane, and

A step of applying a slurry composition for an adhesive layer containing a particulate polymer having a glass transition temperature of 10 ° C or more and 110 ° C or less on the porous film, and drying it to obtain an adhesive layer. Manufacturing method.

[2] The method for producing a porous membrane separator according to [1], wherein the water-soluble polymer compound has an acidic group.

[3] The method for producing a porous membrane separator according to [2], wherein the acidic group is a carboxyl group.

[4] The method for producing a porous membrane separator according to any one of [1] to [3], wherein the concentration of the low-molecular compound in the porous membrane is 1000 ppm or less per unit weight of the porous membrane.

[5] The method for producing a porous membrane separator according to any one of [1] to [4], wherein the low-molecular compound is ammonia.

[6] The water-soluble polymer compound is at least one selected from the group consisting of carboxymethyl cellulose and a maleimide-maleic acid copolymer containing a structural unit represented by the following formula (I), [1] to [5] The manufacturing method of the separator in any one of Claims.

[Formula 1]

(In formula (I), R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group, a phenyl group substituted with an alkyl group having 1 to 6 carbon atoms, an alkyloxy group having 1 to 6 carbon atoms) It is at least one member selected from the group consisting of a substituted phenyl group, a phenyl group substituted with a halogen atom, and a hydroxyphenyl group.)

[7] A method for producing a laminate for a lithium ion secondary battery, comprising pressure-bonding an electrode and a porous membrane separator produced by the production method according to any one of [1] to [6].

According to the manufacturing method of the porous membrane separator of this invention, the porous membrane separator for lithium ion secondary batteries provided with a porous membrane and an adhesive layer can be manufactured. In addition, a porous membrane and an adhesive layer can be produced using a slurry composition containing water, and the porous membrane is hardly soluble in the slurry composition for an adhesive layer. Further, according to the production method of the present invention, a porous membrane separator excellent in both adhesion to an electrode and blocking resistance is obtained.

Moreover, according to the manufacturing method of the laminated body for lithium ion secondary batteries of this invention, the laminated body for lithium ion secondary batteries provided with the porous membrane separator manufactured by the manufacturing method of the porous membrane separator of this invention is obtained.

Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples shown below, and may be arbitrarily changed within the scope not departing from the scope of the claims of the present invention and its equivalents.

In the following description, (meth) acrylic acid means acrylic acid and methacrylic acid. Moreover, (meth) acrylate means acrylate and methacrylate. In addition, (meth) acrylonitrile means acrylonitrile and methacrylonitrile.

In addition, when a substance is water-soluble, it means that when 25 g of the substance is dissolved in 100 g of water, the insoluble content is less than 0.5% by weight. On the other hand, when a substance is water-insoluble, it means that when 25 g of the substance is dissolved in 100 g of water, the insoluble content is 90% by weight or more.

[One. Manufacturing method of porous membrane separator]

The manufacturing method of the porous membrane separator of this invention is the process of apply | coating the slurry composition for porous membranes on at least one side of a separator base material, and drying it, and obtaining a porous membrane, and apply | coating the slurry composition for adhesive layers on the said porous membrane, and drying it, and an adhesive layer It includes the process of obtaining. In the manufacturing method of the porous membrane separator of this invention, what contains water as the slurry composition for porous membranes and the slurry composition for adhesive layers mentioned above is used.

[1.1. Process of obtaining a porous membrane]

In the process of obtaining a porous film, the slurry composition for a porous film is applied to at least one surface of a separator base material, and dried to obtain a porous film. The porous membrane formed using a conventional slurry composition containing water as a solvent was generally easily soluble in water. However, the porous membrane formed using the slurry composition for a porous membrane according to the present invention is hardly soluble in water. Therefore, even if the slurry composition for adhesive layers containing water is applied on this porous membrane, the porous membrane does not melt well.

[1.1.1. Separator description]

As the separator base material, any member capable of preventing a short circuit of the electrode can be used without interfering with charging and discharging of the battery in the lithium ion secondary battery. As the separator substrate, for example, a porous substrate having fine pores can be used. Usually, a porous base material (that is, an organic separator) made of an organic material is used as the separator base material. Specific examples of the separator substrate include microporous membranes or nonwoven fabrics including polyolefin resins such as polyethylene and polypropylene, and aromatic polyamide resins.

The thickness of the separator substrate is usually 0.5 µm or more, preferably 1 µm or more, and is usually 40 µm or less, preferably 30 µm or less, and more preferably 10 µm or less. If it is this range, the resistance by the separator base material in a battery will become small, and workability at the time of battery manufacture is excellent.

[1.1.2. Porous membrane slurry composition]

The slurry composition for a porous membrane may be called at least one kind of low-molecular-weight compound (hereinafter, referred to as "low-molecular-weight compound X") selected from the group consisting of non-conductive particles, water-soluble polymer compounds, water, and ammonia and amine compounds. ). Moreover, it is preferable that the slurry composition for porous films contains a binder.

[1.1.2.1. Non-conductive particles]

As the non-conductive particles, inorganic particles may be used, or organic particles may be used.

The inorganic particles are excellent in dispersion stability in a solvent, and it is difficult to settle in a slurry composition for a porous membrane, and usually, a uniform slurry state can be maintained for a long time. In addition, when inorganic particles are used, the heat resistance of the porous membrane can be usually increased. As the material of the non-conductive particles, an electrochemically stable material is preferable. From this viewpoint, preferred examples of inorganic materials for non-conductive particles include aluminum oxide (alumina), hydrates of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), silicon oxide, magnesium oxide ( Magnesia), magnesium hydroxide, calcium oxide, titanium oxide (titania), BaTiO ₃ , ZrO, oxide particles such as alumina-silica composite oxide; nitride particles such as aluminum nitride and boron nitride; covalent crystal grains such as silicon and diamond ; Poorly soluble ion crystal grains such as barium sulfate, calcium fluoride, barium fluoride; clay fine particles such as talc, montmorillonite, etc. Among these, oxide particles are preferred from the viewpoint of stability and dislocation stability in the electrolytic solution, and Among them, titanium oxide, aluminum oxide, and acid from the viewpoint of low water absorption and excellent heat resistance (for example, resistance to high temperatures of 180 ° C. or higher) Hydrates of aluminum fluoride, magnesium oxide and magnesium hydroxide are more preferred, aluminum oxide, hydrates of aluminum oxide, magnesium oxide and magnesium hydroxide are more preferred, and aluminum oxide is particularly preferred.

As the organic particles, particles of a polymer are usually used. The organic particles can control the affinity for water by adjusting the type and amount of functional groups on the surface of the organic particles, and furthermore, the amount of moisture contained in the porous membrane can be controlled. Moreover, the organic particles are usually excellent in that there is little elution of metal ions. Preferred examples of the organic material of the non-conductive particles include various polymers such as polystyrene, polyethylene, polyimide, melamine resin, and phenol resin. The polymer forming the particles may be a mixture, a modified product, a derivative, a random copolymer, an alternating copolymer, a graft copolymer, a block copolymer, or a crosslinked product. The organic particles may be formed of a mixture of two or more polymers.

When using organic particles as non-conductive particles, it is not necessary to have a glass transition temperature, but when the organic material forming the organic particles has a glass transition temperature, the glass transition temperature is usually 150 ° C. or higher, preferably It is 200 degreeC or more, More preferably, it is 250 degreeC or more, and it is 400 degreeC or less normally.

The non-conductive particles may be subjected to, for example, elemental substitution, surface treatment, solid solution formation, and the like, if necessary. Further, the non-conductive particles may include one type of the above-mentioned material alone, or may include two or more types in any ratio in one particle. Further, the non-conductive particles may be used in combination of two or more kinds of particles formed of different materials.

Examples of the shape of the non-conductive particles include spherical, elliptical spherical, polygonal, tetrapod (registered trademark), plate, and scale. Especially, from the viewpoint of increasing the porosity of the porous membrane and suppressing the decrease in ion conductivity due to the porous membrane separator, tetrapod (registered trademark) phase, plate shape, and scale shape are preferable.

The volume average particle diameter D50 of the non-conductive particles is usually 0.1 µm or more, preferably 0.2 µm or more, and is usually 5 µm or less, preferably 2 µm or less, and more preferably 1 µm or less. By using such non-conductive particles having a volume average particle diameter D50, even if the thickness of the porous membrane is thin, a uniform porous membrane can be obtained, so that the capacity of the battery can be increased. Here, the volume average particle diameter D50 represents a particle diameter in which the cumulative volume calculated on the small diameter side becomes 50% in the particle diameter distribution measured by the laser diffraction method.

The BET specific surface area of the non-conductive particles is, for example, preferably 0.9 m 2 / g or more, and more preferably 1.5 m 2 / g or more. In addition, from the viewpoint of suppressing aggregation of non-conductive particles and improving the fluidity of the slurry composition for porous membranes, the BET specific surface area is preferably not too large, for example, preferably 150 m 2 / g or less.

[1.1.2.2. Water-soluble polymer compound]

The water-soluble polymer compound has a function of binding non-conductive particles in the porous membrane. Therefore, the strength of the porous membrane can be increased by containing the water-soluble polymer compound. Further, it is possible to prevent the non-conductive particles from falling off from the porous membrane.

Moreover, the water-soluble polymer compound has a function of binding non-conductive particles and a separator substrate in a porous membrane separator. Therefore, the binding property of a porous film and a separator base material can be improved by containing a water-soluble polymer compound in a porous film.

In addition, the water-soluble polymer compound can usually function as a viscosity modifier in the porous membrane slurry composition. Therefore, when the slurry composition for a porous membrane contains a water-soluble polymer compound, coating property of the slurry composition for a porous membrane can be improved.

It is preferable that a water-soluble high molecular compound has an acidic group. Since the acidic group has an effect of increasing the hydrophilicity of the water-soluble polymer compound, the water-soluble polymer compound having an acidic group can increase water solubility. Moreover, an acidic group can also exhibit the effect of generally increasing the binding property of the water-soluble polymer compound to the non-conductive particles in the porous film separator and the binding property of the porous film to the separator substrate.

As an acidic group which a water-soluble polymer compound has, a carboxyl group, a sulfo group, a phosphoric acid group, a hydroxyl group, etc. are mentioned, for example, Especially, a carboxyl group is preferable. Here, an acidic group may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Examples of the water-soluble polymer compound include maleimide-maleic acid copolymers containing structural units (a) represented by the following formula (I). By using this maleimide-maleic acid copolymer, since a porous membrane separator excellent in heat shrinkage resistance can be realized, the safety of the lithium ion secondary battery can be improved. Moreover, since a porous film with a small amount of water can be formed, decomposition of the electrolytic solution resulting from residual water can be suppressed. Therefore, the expansion of the lithium ion secondary battery due to decomposition of the electrolyte can be suppressed, so that the cycle characteristics of the lithium ion secondary battery can be improved.

[Formula 2]

In Formula (I), R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group, a phenyl group substituted with an alkyl group having 1 to 6 carbon atoms, or an alkyloxy group having 1 to 6 carbon atoms. It represents at least 1 sort (s) selected from the group which consists of a substituted phenyl group, a phenyl group substituted with the halogen atom, and a hydroxyphenyl group.

The structural unit (a) represented by Formula (I) represents a maleimide unit of the maleimide-maleic acid copolymer. The structural unit (a) represented by the formula (I) can be derived, for example, from maleimides represented by the following formula (I-1).

[Formula 3]

In Formula (I-1), R ² is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group, a phenyl group substituted with an alkyl group having 1 to 6 carbon atoms, or alkyl having 1 to 6 carbon atoms. It represents at least 1 sort (s) selected from the group which consists of a phenyl group substituted with the oxy group, the phenyl group substituted with the halogen atom, and a hydroxyphenyl group.

As specific examples of maleimides represented by formula (I-1), maleimide; N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-butylmaleimide, N-pentylmaleimide, N- Hexylmaleimide; N-phenylmaleimide; N- (2-methylphenyl) maleimide, N- (3-methylphenyl) maleimide, N- (4-methylphenyl) maleimide, N- (2-ethylphenyl) maleimide , N- (3-ethylphenyl) maleimide, N- (2-N-propylphenyl) maleimide, N- (2-i-propylphenyl) maleimide, N- (2-N-butylphenyl) maleimide , N- (2,6-dimethylphenyl) maleimide, N- (2,4,6-trimethylphenyl) maleimide, N- (2,6-diethylphenyl) maleimide, N- (2,4, 6-triethylphenyl) maleimide, N- (2-methoxyphenyl) maleimide, N- (2,6-dimethoxyphenyl) maleimide, N- (2-bromophenyl) maleimide, N- ( 2-chlorophenyl) maleimide, N- (2,6-dibromophenyl) maleimide; N- (4-hydroxyphenyl) maleimide, and the like. . Among these, maleimide is preferable from the viewpoint of reactivity to non-conductive particles. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Moreover, the structural unit (a) represented by Formula (I) is also obtained by imidating the structural unit (b) represented by Formula (II) mentioned later, for example.

The maleimide-maleic acid copolymer containing the structural unit (a) represented by formula (I) includes maleic acid units in addition to the above maleimide units. Therefore, the maleimide-maleic acid copolymer containing the structural unit (a) represented by formula (I) includes the structural unit (b) represented by the following formula (II).

[Formula 4]

In formula (II), X represents a maleic acid unit. Here, the maleic acid unit refers to a structural unit having a structure formed by polymerizing maleic acid. Moreover, the maleic acid unit represented by X may be partially neutralized with ions other than hydrogen ions, partially anhydrous, or partially esterified.

The structural unit (b) represented by the formula (II) can be derived from, for example, maleic acid represented by the following formula (II-1) or maleic anhydride represented by the formula (II-2).

[Formula 5]

[Formula 6]

In Formula (II-1), R ³ and R ⁴ are at least one selected from the group consisting of hydrogen atom, alkyl group, alkali metal ion, alkaline earth metal ion, ammonium ion, alkylammonium ion and alkanolammonium ion. Shows. Here, the alkylammonium ion refers to a cation in which one hydrogen atom is added to the nitrogen atom of the alkylamine. Moreover, an alkanol ammonium ion means a cation in which one hydrogen atom is added to the nitrogen atom of the alkanolamine. At this time, R ³ and R ⁴ may be the same or different. When R ³ or R ⁴ is an alkyl group, formula (II-1) represents a maleic acid ester. Further, when R ³ or R ⁴ is an alkali metal ion, alkaline earth metal ion, ammonium ion, alkylammonium ion, or alkanolammonium ion, formula (II-1) represents maleate.

Maleic acid ester and maleate are mentioned as a specific example of maleic acid represented by Formula (II-1).

Examples of the maleic acid ester include monomethyl maleate, dimethyl maleate, monoethyl maleate, diethyl maleate, monopropyl maleate, and dipropyl maleate.

Examples of the maleic acid salt include alkali metal salts of maleic acid such as monolithic maleate, dilithium maleate, monosodium maleate, disodium maleate, monopotassium maleate, and dipotassium maleate; calcium maleate, magnesium maleate Alkaline earth metal salts of maleic acid such as; ammonium salts of maleic acid such as monoammonium maleate and diammonium maleate; monomethylammonium maleate, bismonomethylammonium maleate, monodimethylammonium maleate, bisdimethylammonium maleate, etc. Alkylamine salt of maleic acid; maleic acid-2-hydroxyethylammonium, maleic acid bis-2-hydroxyethylammonium, maleic acid di (2-hydroxyethyl) ammonium, maleic acid bisdi (2-hydroxyethyl) And alkanolamine salts of maleic acid such as ammonium.

Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Moreover, the maleimide-maleic acid copolymer containing the structural unit (a) represented by Formula (I), besides the structural unit (a) represented by Formula (I) and the structural unit (b) represented by Formula (II), It is preferable to further include the structural unit (c) represented by Formula (III). Since the maleimide-maleic acid copolymer containing the structural unit (a) represented by the formula (I) has the structural unit (c) represented by the formula (III), the water content in the porous membrane can be reduced. The cycle characteristics of the lithium ion secondary battery can be improved.

[Formula 7]

In formula (III), Y represents a hydrocarbon group having 2 to 12 carbon atoms. Moreover, the valence of this hydrocarbon group is usually bivalent.

The structural unit (c) represented by formula (III) is, for example, ethylene, 1-butene, isobutene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, isobutylene, Olefin hydrocarbons such as diisobutylene, 1-nonene, 1-decene, and 1-dodecene; and can be derived from hydrocarbon compounds such as aromatic hydrocarbons such as styrene and α-methylstyrene. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

In the maleimide-maleic acid copolymer containing the structural unit (a) represented by the formula (I), when the amount of the total structural unit is 100 mol%, the content of the structural unit (a) represented by the formula (I) The ratio is preferably 5 mol% or more, more preferably 10 mol% or more, particularly preferably 15 mol% or more, preferably 75 mol% or less, more preferably 60 mol% or less, particularly preferably Is 45 mol% or less. By setting the content ratio of the structural unit (a) in the maleimide-maleic acid copolymer to be at least the lower limit of the above range, the heat shrinkage resistance of the porous membrane can be effectively increased. In addition, the binding property between the non-conductive particles and the water-soluble polymer compound can be improved. Moreover, since the swelling property of the water-soluble high molecular compound with respect to an electrolyte in a lithium ion secondary battery can be reduced by setting it below the upper limit of the said range, cycling characteristics of a lithium ion secondary battery can be made favorable.

In the maleimide-maleic acid copolymer containing the structural unit (a) represented by the formula (I), when the amount of the total structural unit is 100 mol%, the content of the structural unit (b) represented by the formula (II) The ratio is preferably 5 mol% or more, more preferably 10 mol% or more, particularly preferably 15 mol% or more, preferably 75 mol% or less, more preferably 60 mol% or less, particularly preferably Is 45 mol% or less. By setting the content ratio of the structural unit (b) in the maleimide-maleic acid copolymer to be more than the lower limit of the above range, the amount of moisture in the porous membrane can be effectively reduced, so that decomposition of the electrolyte solution caused by residual moisture can be suppressed. have. For this reason, expansion of the lithium ion secondary battery due to decomposition of the electrolytic solution can be suppressed, and cycle characteristics can be improved. Moreover, by setting below an upper limit, the heat resistance of a maleimide-maleic acid copolymer can be improved and the heat shrinkage resistance of a porous membrane can be effectively raised.

In the maleimide-maleic acid copolymer containing the structural unit (a) represented by the formula (I), when the amount of the total structural unit is 100 mol%, the content of the structural unit (c) represented by the formula (III) The ratio is preferably 5 mol% or more, more preferably 10 mol% or more, particularly preferably 15 mol% or more, preferably 75 mol% or less, more preferably 60 mol% or less, particularly preferably Is 45 mol% or less. By setting the content ratio of the structural unit (c) in the maleimide-maleic acid copolymer to be at least the lower limit of the above range, the heat resistance of the maleimide-maleic acid copolymer can be effectively increased. Therefore, it is possible to improve the heat shrinkage resistance of the porous membrane separator. Moreover, by making it below an upper limit, the water content in a porous membrane can further be reduced, and the cycling characteristics of a secondary battery can be improved.

As a manufacturing method of the maleimide-maleic acid copolymer containing the structural unit (a) represented by Formula (I), the following manufacturing method A and manufacturing method B are mentioned, for example.

Production method A: A method of polymerizing maleimides represented by formula (I-1) and maleic acids represented by formula (II-1) or maleic anhydride represented by formula (II-2).

Production method B: After polymerization of maleic anhydride represented by formula (II-1) or maleic anhydride represented by (II-2), a part of the structural unit formed by polymerizing maleic acid or maleic anhydride is represented by formula (I A method of maleic oxidation with a compound having the group R ² in -1), and further cyclizing and dehydrating (imidizing) a part thereof.

As the polymerization method in Production Method A, a known polymerization method can be adopted. Especially, since polymerization in a homogeneous system is preferable, the solution polymerization method is preferable. As a solvent used for the solution polymerization method, for example, methanol, isopropyl alcohol, isobutyl alcohol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, ethyl acetate, butyl acetate, ethyl lactate, tetrahydrofuran , Dioxane, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, benzene, ethylbenzene, toluene, xylene, cyclohexane, ethylcyclohexane, acetonitrile and the like. One of these solvents may be used alone, or two or more of them may be used in combination at any ratio. Moreover, you may use these solvents by dehydrating.

The amount of the solvent used is usually 600 parts by weight or less, preferably 400 parts by weight or less, based on 100 parts by weight of the maleimide-maleic acid copolymer to be produced. Thereby, a maleimide-maleic acid copolymer having a high molecular weight can be obtained. Moreover, the lower limit is not particularly limited as long as it can form a solution.

In Production Method A, polymerization is usually performed by injecting a polymerization raw material into a reaction vessel. In polymerization, it is preferable to remove dissolved oxygen out of the reaction system in advance, for example, by vacuum degassing or nitrogen substitution. In addition, from the viewpoint of efficiently advancing the reaction, the polymerization temperature is preferably -50 ° C or higher, more preferably 50 ° C or higher, preferably 200 ° C or lower, and more preferably 150 ° C or lower. The polymerization time is preferably 1 hour or more, preferably 100 hours or less, and more preferably 50 hours or less. By setting the polymerization temperature and polymerization time within the above range, the ease and productivity of polymerization control can be effectively increased.

In the production method B, examples of the compound having the group R ² in the formula (I-1) include ammonia; a primary amine having a group R ² such as aminophenol or normal butylamine. One of these compounds may be used alone, or two or more of them may be used in combination at any ratio.

As the manufacturing method B, as a manufacturing method using a polymer containing a unit obtained by polymerizing maleic anhydride, for example, the following production method B-1 and production method B using a hydrocarbon group having 2 to 12 carbon atoms and a copolymer of maleic anhydride -2.

Production Method B-1: A copolymer of a hydrocarbon group having 2 to 12 carbon atoms and maleic anhydride and aminophenol, in an organic solvent such as dimethylformaldehyde, usually at a reaction temperature of 40 ° C or higher and 150 ° C or lower, usually 1 hour to React for 20 hours. Thereby, part of the maleic anhydride unit is changed to N- (hydroxyphenyl) maleamic acid unit. Here, the maleic anhydride unit refers to a structural unit having a structure formed by polymerizing maleic anhydride. Moreover, the N- (hydroxyphenyl) maleamic acid unit refers to a structural unit having a structure formed by polymerizing an N- (hydroxyphenyl) maleamic acid unit. Thereafter, an azeotropic solvent is mixed to further remove the water generated from the cyclization dehydration, and is usually subjected to cyclization dehydration at a reaction temperature of 80 ° C or more and 200 ° C or less for 1 hour to 20 hours, and maleimide -Obtain a maleic acid copolymer.

Production Method B-2: A hydrocarbon group having 2 to 12 carbon atoms and a copolymer of maleic anhydride and aminophenol, in an organic solvent such as dimethylformaldehyde, in the presence of an azeotropic solvent, usually at a reaction temperature of 80 ° C or higher and 200 ° C or lower , It is usually reacted for 1 hour to 20 hours. Thereby, a part of the maleic anhydride unit is cyclized and dehydrated through an N- (hydroxyphenyl) maleamic acid unit to obtain a maleimide-maleic acid copolymer.

As a specific example of the copolymer of a hydrocarbon group having 2 to 12 carbon atoms and maleic anhydride described in Production Method B-1 and Production Method B-2, a copolymer of isobutylene and maleic anhydride (hereinafter referred to as "isobutylene-anhydrous" as appropriate). It may be called a maleic acid copolymer.).

In any of the above-mentioned production methods B-1 and B-2, the water may be removed without using an azeotropic solvent during the cyclization dehydration reaction. For example, water can be removed at a temperature of 100 ° C or higher and 200 ° C or lower. Moreover, dehydration reaction can be effectively performed by the flow of nitrogen gas.

Examples of the azeotropic solvent used for removing water generated in the cyclization dehydration reaction include benzene, toluene, and xylene. These may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

In the cyclization dehydration reaction, 1 mole of water is produced from 1 mole of N- (hydroxyphenyl) maleamic acid unit produced by the reaction of an aminophenol with a maleic anhydride unit in an isobutylene-maleic anhydride copolymer. The amount of the azeotropic solvent used can be set to an amount sufficient to remove the azeotropic water.

When the reaction of a hydrocarbon group having 2 to 12 carbon atoms with a maleic anhydride copolymer and aminophenol is performed in two stages as in the above Production Method B-1, the reaction temperature of the first stage reaction is usually 40 ° C. Above, it is preferably 50 ° C or higher, and usually 150 ° C or lower, preferably 100 ° C or lower. Moreover, the reaction temperature of the reaction in the second stage is usually 80 ° C or higher, preferably 100 ° C or higher, and is usually 200 ° C or lower, preferably 150 ° C or lower. Here, the reaction in the first stage means a reaction for producing a copolymer of N- (hydroxyphenyl) maleamic acid by reacting a hydrocarbon group having 2 to 12 carbon atoms with a maleic anhydride copolymer and an aminophenol. Moreover, the reaction in the second stage means a reaction in which the copolymer of N- (hydroxyphenyl) maleamic acid is cyclized and dehydrated.

In addition, when the reaction of a hydrocarbon group having 2 to 12 carbon atoms with a maleic anhydride copolymer and aminophenol is performed in one step in the presence of an azeotropic solvent for dehydration, the reaction temperature is , It is usually 80 ° C or higher, preferably 100 ° C or higher, and is usually 200 ° C or lower, preferably 150 ° C or lower.

In the said production method B-1 and production method B-2, the reaction time of a C2-C12 hydrocarbon group, a maleic anhydride copolymer, and aminophenol depends on reaction temperature, the amount of aminophenol used, and the desired reaction rate. Different. Here, as said reaction rate, the denaturation rate of the maleic anhydride unit to N- (hydroxyphenyl) maleimide unit in isobutylene-maleic anhydride copolymer is mentioned, for example. Usually, in the manufacturing method B-1, both the 1st stage and the 2nd stage reaction can be made into 1 hour-20 hours. Moreover, reaction time in the manufacturing method B-2 can be 1 hour-20 hours.

In the above-mentioned manufacturing method, control of the content rate of the structural unit (a) represented by Formula (I) in the target maleimide-maleic acid copolymer is, for example, the amount of aminophenol used, the reaction temperature, and the reaction time. It can be carried out easily by adjusting.

After completion of the reaction, recovery of the maleimide-maleic acid copolymer from the reaction solution can be easily carried out by, for example, precipitation of the maleimide-maleic acid copolymer using an inert solvent such as water and ethers. You can.

The maleimide-maleic acid copolymer obtained as described above can be soluble in water by, for example, hydrolyzing or neutralizing the maleic acid unit in the maleimide-maleic acid copolymer. As a specific example, (1) a method of hydrolyzing a maleic anhydride unit in a maleimide-maleic acid copolymer at a high temperature (80 ° C to 100 ° C); (2) a maleic acid unit in a maleimide-maleic acid copolymer neutralizing agent And neutralizing the furnace. Moreover, in method (1), it is preferable to mix a neutralizing agent at the time of hydrolysis. Moreover, in the method of (2), the temperature at the time of mixing a neutralizing agent is not specifically limited, For example, it can be set to room temperature.

Examples of the neutralizing agent include alkali metal hydroxides such as lithium hydroxide, sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide, magnesium hydroxide and barium hydroxide; hydroxides of metals belonging to IIIA in the long periodic table, such as aluminum hydroxide; Hydroxides such as sodium carbonate; alkali metal carbonates such as sodium carbonate and potassium carbonate; carbonates such as alkaline earth metal carbonates such as magnesium carbonate; and organic amines. Examples of the organic amine include alkylamines such as ethylamine, diethylamine and propylamine; alcoholamines such as monomethanolamine, monoethanolamine and monopropanolamine; and ammonias such as ammonia. Among these, it is preferable that sodium ions, lithium ions, and ammonium ions can be produced from the viewpoint of high solubilization effect on water. Moreover, as a neutralizing agent, you may use individually by 1 type and may use it combining 2 or more types by arbitrary ratios.

Further, other examples of the water-soluble polymer compound include cellulose derivatives such as carboxymethyl cellulose, carboxymethyl ethyl cellulose, methyl cellulose, ethyl cellulose, ethyl hydroxyethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose; poly (meth) ) Acrylic acid polymers and the like. Moreover, as a water-soluble high molecular compound, salts, such as these ammonium salts and alkali metal salts, are mentioned, for example. Especially, the salt of carboxymethylcellulose is preferable, and the ammonium salt of carboxymethylcellulose is especially preferable.

As the ammonium salt of carboxymethylcellulose, commercially available ones can be used. Moreover, ammonia used for neutralization may remain in the ammonium salt of a commercially available carboxymethylcellulose, and in this case, the residual ammonia is treated as a low molecular compound X.

The degree of etherification of the cellulose derivative is preferably 0.5 or more, preferably 2 or less, and more preferably 1.5 or less. In addition, here, the degree of etherification is a value which shows how many hydroxyl groups contained per three glucose units of cellulose are etherified on average. When the degree of etherification is within the above range, stability of the slurry composition is high, and sedimentation and aggregation of solid content can be difficult to occur. Moreover, the coating property and fluidity | liquidity of a coating material are improved by using a cellulose derivative.

Among the above-mentioned water-soluble polymer compounds, a maleimide-maleic acid copolymer containing carboxymethyl cellulose and a structural unit (a) represented by formula (I) is preferable.

Moreover, one type of water-soluble polymer compound may be used alone, or two or more types may be used in combination at any ratio.

The weight average molecular weight of the water-soluble polymer compound is preferably 1000 or more, more preferably 1500 or more, particularly preferably 2000 or more, and preferably 500000 or less, more preferably 250000 or less, particularly preferably 150000 or less. . Moreover, the weight average molecular weight of the maleimide-maleic acid copolymer containing the structural unit (a) represented by Formula (I) is preferably 50000 or more and 100000 or less. By setting the weight average molecular weight of the water-soluble polymer compound to be more than the lower limit of the above range, the strength of the water-soluble polymer compound can be increased to form a stable porous film, thereby improving durability such as cycle characteristics and high temperature storage characteristics of the lithium ion secondary battery. have. Moreover, since the water-soluble polymer compound can be made flexible by setting it to the upper limit or less of the above-mentioned range, for example, it is possible to improve the binding property of the porous membrane to the separator substrate. Here, the weight average molecular weight of the water-soluble polymer compound is converted into polystyrene by GPC (gel permeation chromatography) and gel permeation chromatography (GPC) using the developing solution as N, N-dimethylformamide (DMF). It can be measured as a value.

The amount of the water-soluble polymer compound is an amount in the porous membrane, and is usually 0.1% by weight or more, and usually 30% by weight or less. Especially, when using an inorganic particle as non-conductive particle, Preferably it is 10 weight% or less, More preferably, it is 5 weight% or less. Moreover, when using an organic particle as non-conductive particle, it is preferably 3 weight% or more, Preferably it is 10 weight% or less. Moreover, the amount of the water-soluble polymer compound is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, particularly preferably 0.5 parts by weight or more, and preferably 20 parts by weight with respect to 100 parts by weight of the non-conductive particles. Hereinafter, it is more preferably 15 parts by weight or less, and particularly preferably 10 parts by weight or less. By making the amount of the water-soluble polymer compound more than the lower limit of the above range, the strength and binding property of the porous membrane can be improved, and the coating property of the slurry composition for a porous membrane can be improved. Moreover, since both the strength and porosity of a porous membrane can be made high by setting it below an upper limit, both short circuit resistance by a porous membrane separator and battery characteristics of a lithium ion secondary battery can be made favorable.

[1.1.2.3. Low molecular compound]

The slurry composition for porous membranes has at least one kind of low molecular compound X selected from the group consisting of ammonia and amine compounds. The low-molecular compound X is usually vaporized when the membrane of the slurry composition for a porous membrane is dried, and therefore, the porous membrane hardly remains. However, it is considered that the action of the low-molecular compound X is removed during drying to improve the water resistance of the porous membrane, so that the porous membrane becomes less soluble in water.

Examples of the low-molecular compound X include ammonia; secondary amines such as dimethylamine, diethylamine, and dibutylamine; tertiary amines such as trimethylamine, triethylamine, tributylamine, and thiazabicyclononene. Can be mentioned. Among them, ammonia is preferred. These may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The molecular weight of the low molecular compound X is preferably 17 or more, preferably less than 1000, more preferably 200 or less, and particularly preferably 150 or less. By setting the molecular weight of the low-molecular-weight compound X to be equal to or less than the upper limit of the above range, the low-molecular-weight compound X can be stably vaporized when the membrane of the slurry composition for a porous membrane is dried and removed from the porous membrane.

The boiling point of the low-molecular compound X is usually 100 ° C or lower, preferably 90 ° C or lower, and more preferably 80 ° C or lower. By having such a low boiling point, when drying the membrane of the slurry composition for porous membranes, the low molecular compound X can be stably vaporized and removed from the porous membrane. The lower limit is not limited, but is usually -33 ° C or higher.

In the slurry composition for a porous membrane, the amount of the low-molecular compound X is preferably 0.01 parts by weight or more, more preferably 0.05 parts by weight or more, particularly preferably 0.1 parts by weight or more, with respect to 100 parts by weight of the water-soluble polymer compound, It is preferably 50 parts by weight or less, more preferably 40 parts by weight or less, and particularly preferably 30 parts by weight or less. When the amount of the low-molecular compound X becomes more than the lower limit of the above range, the water-soluble polymer compound can be neutralized and dissolved. Moreover, when it becomes below the upper limit of the said range, when drying the membrane of the slurry composition for porous membranes, the low molecular compound X can be vaporized stably.

[1.1.2.4. water]

It is preferable to adjust the amount of water in the slurry composition for a porous membrane so that the viscosity of the slurry composition for a porous membrane becomes a preferable range for application | coating according to the kind of non-conductive particle, water-soluble high molecular compound, and low molecular compound X. Specifically, the concentration of the solid content of the non-conductive particles, the water-soluble polymer compound and the low-molecular compound X, and the binder and optional components used as necessary, is preferably 20% by weight or more, and more preferably 30% by weight. % Or more, preferably 60% by weight or less, more preferably 50% by weight or less.

[1.1.2.5. bookbinder]

It is preferable that the slurry composition for porous membranes contains a binder. By containing a binder, the binding property of the porous membrane is improved, and strength against mechanical force exerted on the porous membrane separator during handling such as during winding and transportation can be improved.

Various polymer components can be used as the binder. For example, styrene-butadiene copolymer (SBR), acrylonitrile-butadiene copolymer (NBR), hydrogenated SBR, hydrogenated NBR, styrene-isoprene-styrene block copolymer (SIS), acrylic polymer and the like. Especially, an acrylic polymer is preferable as a binder, and the copolymer of a (meth) acrylic acid ester monomer and a (meth) acrylonitrile monomer is especially preferable.

(Meth) acrylic acid ester monomer, for example, there may be mentioned a compound represented by CH ₂ = CR ⁵ -COOR ^6. Here, R ⁵ represents a hydrogen atom or a methyl group, and R ⁶ represents an alkyl group or a cycloalkyl group.

Examples of the (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-amyl acrylate, isoamyl acrylate, Acrylates such as n-hexyl acrylate, 2-ethylhexyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, hexyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, and benzyl acrylate; Methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-amyl methacrylate, and methacrylic acid Soap wheat, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, benzyl methacrylate Back Acrylate. Among these, acrylate is preferable, and n-butyl acrylate and 2-ethylhexyl acrylate are particularly preferable from the viewpoint of improving the strength of the porous membrane. Moreover, these monomers may be used individually by 1 type, or may be used combining two or more types by arbitrary ratios.

(Meth) acrylonitrile monomer and (meth) acrylonitrile monomer unit may be used individually by 1 type, or may be used in combination of 2 or more type by arbitrary ratios.

The polymerization ratio of the (meth) acrylic acid ester monomer to the (meth) acrylonitrile monomer ((meth) acrylonitrile monomer / (meth) acrylic acid ester monomer) is preferably 1/99 or more, more preferably 5/95 It is the above, Preferably it is 30/70 or less, More preferably, it is 25/75 or less. By setting the polymerization ratio of the (meth) acrylic acid ester monomer to the (meth) acrylonitrile monomer to be at least the lower limit of the above range, the swelling property of the binder with respect to the electrolytic solution can be suppressed, and a decrease in ion conductivity can be prevented. Moreover, by making it below an upper limit, the strength of a binder can be made high and the strength of a porous membrane separator can be made high.

Moreover, the copolymer of the said (meth) acrylic acid ester monomer and a (meth) acrylonitrile monomer further copolymerized copolymerization components other than a (meth) acrylic acid ester monomer and a (meth) acrylonitrile monomer as needed. May be As a structural unit corresponding to these copolymerization components, for example, a structural unit having a structure formed by polymerizing a vinyl monomer having an acidic group, a crosslinkable monomer unit, and the like.

As the vinyl monomer having an acidic group, for example, a monomer having a -COOH group (carboxyl group. Also referred to as a "carboxylic acid group"), a monomer having a -OH group (hydroxyl group), a -SO ₃ H group (sulfo group. " Sulfonic acid group.), A monomer having a -PO ₃ H ₂ group, a monomer having a -PO (OH) (OR) group (R represents a hydrocarbon group), and a monomer having a lower polyoxyalkylene group. Can be lifted. Moreover, the acid anhydride which produces a carboxylic acid group by hydrolysis can also be used similarly.

As a monomer which has a carboxylic acid group, monocarboxylic acid, dicarboxylic acid, anhydride of dicarboxylic acid, derivatives thereof, etc. are mentioned, for example. As a monocarboxylic acid, acrylic acid, methacrylic acid, crotonic acid, 2-ethylacrylic acid, isocrotonic acid, etc. are mentioned, for example. As dicarboxylic acid, maleic acid, fumaric acid, itaconic acid, methyl maleic acid, etc. are mentioned, for example. Examples of the acid anhydride of the dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, dimethyl maleic anhydride and the like.

Examples of the monomer having a hydroxyl group include ethylenically unsaturated alcohols such as (meth) allyl alcohol, 3-butene-1-ol, and 5-hexene-1-ol; acrylic acid-2-hydroxyethyl and acrylic acid-2- Alkanol esters of ethylenically unsaturated carboxylic acids such as hydroxypropyl and methacrylic acid-2-hydroxyethyl; general formula CH ₂ = CR ⁷ -COO- (C _n H _2n O) _m -H (m silver Esters of polyalkylene glycol and (meth) acrylic acid represented by an integer of 2 to 9, n represents an integer of 2 to 4, and R ⁷ represents hydrogen or a methyl group; 2-hydroxyethyl-2 '-(meth) Mono (meth) acrylic acid esters of dihydroxy esters of dicarboxylic acids such as acryloyloxyphthalate and 2-hydroxyethyl-2 '-(meth) acryloyloxysuccinate; 2-hydroxyethyl vinyl Vinyl ethers such as ether and 2-hydroxypropyl vinyl ether; to (meth) allyl-2-hydroxyethyl Mono (meth) allyl ethers of alkylene glycols such as ter, (meth) allyl-2-hydroxypropyl ether, and (meth) allyl-3-hydroxypropyl ether; diethylene glycol mono (meth) allyl ether, di Polyoxyalkylene glycol (meth) monoallyl ethers such as propylene glycol mono (meth) allyl ether; glycerin mono (meth) allyl ether, (meth) allyl-2-chloro-3-hydroxypropyl ether, (meth) Mono (meth) allyl ether of halogen and hydroxy substituents of (poly) alkylene glycols such as allyl-2-hydroxy-3-chloropropyl ether; mono monovalent polyhydric phenols such as eugenol and isooigenol ( Meth) allyl ether and its halogen substituents; (meth) allyl-2-hydroxyethylthioether, (meth) allyl-2-hydroxypropylthioether, and alkylene glycol (meth) allylthioethers. You can.

As the monomer having a sulfonic acid group, for example, vinylsulfonic acid, methylvinylsulfonic acid, (meth) allyl sulfonic acid, styrenesulfonic acid, (meth) acrylic acid-2-sulfonic acid ethyl, 2-acrylamide-2-methylpropanesulfonic acid, 3-aryl And oxy-2-hydroxypropanesulfonic acid.

As a monomer which has a -PO ₃ H ₂ group and / or a -PO (OH) (OR) group (R represents a hydrocarbon group), for example, phosphoric acid-2- (meth) acryloyloxyethyl, methyl phosphate- 2- (meth) acryloyloxyethyl, ethyl phosphate- (meth) acryloyloxyethyl, and the like.

As a monomer which has a lower polyoxyalkylene group, poly (alkylene oxide), such as poly (ethylene oxide), etc. are mentioned, for example.

As the vinyl monomer having an acidic group, among these, a monomer having a carboxylic acid group is preferable because it has excellent adhesion to an organic separator, and because it effectively captures transition metal ions eluted from the positive electrode active material, and among them, acrylic acid, Monocarboxylic acids having 5 or less carbon atoms having carboxylic acid groups such as methacrylic acid, and dicarboxylic acids having 5 or less carbon atoms having two carboxylic acid groups such as maleic acid and itaconic acid are preferred. Furthermore, acrylic acid, methacrylic acid, and itaconic acid are preferred from the viewpoint of high storage stability of the prepared slurry composition.

The content ratio of the structural unit having a structure formed by polymerizing a vinyl monomer having an acidic group in the copolymer of the (meth) acrylic acid ester monomer and the (meth) acrylonitrile monomer is preferably 1.0% by weight or more , More preferably, it is 1.5% by weight or more, preferably 3.0% by weight or less, and more preferably 2.5% by weight or less.

The crosslinkable monomer unit is a structural unit obtained by polymerizing a crosslinkable monomer. The crosslinkable monomer is a monomer capable of forming a crosslinked structure during or after polymerization by heating or energy ray irradiation. As an example of a crosslinkable monomer, the monomer which has thermal crosslinkability is mentioned normally. More specifically, a monofunctional crosslinkable monomer having a heat crosslinkable crosslinkable group and one olefinic double bond per molecule; a polyfunctional crosslinkable monomer having two or more olefinic double bonds per molecule is mentioned. have.

Examples of the heat crosslinkable crosslinkable group include an epoxy group, an N-methylolamide group, an oxetanyl group, an oxazoline group, and combinations thereof. Among these, the epoxy group is more preferable from the viewpoint of easy control of crosslinking and crosslinking density.

Examples of the crosslinkable monomer having an epoxy group as a heat crosslinkable crosslinkable group and having an olefinic double bond are vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether. Unsaturated glycidyl ethers such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9- Monoepoxides of dienes such as cyclododecadiene or polyene; alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; And glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl -3-pentenoate, glycidyl ester of 3-cyclohexenecarboxylic acid, 4-methyl-3-cyclohexenecarboxylic acid Glycidyl of unsaturated carboxylic acids such as receiving dill ester may be mentioned pyridyl ester.

Examples of the crosslinkable monomer having an N-methylolamide group as a heat crosslinkable crosslinkable group and having an olefinic double bond include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide. You can.

Examples of the crosslinkable monomer having an oxetanyl group as a heat crosslinkable crosslinkable group and having an olefinic double bond include 3-((meth) acryloyloxymethyl) oxetane and 3-((meth) acryloyloxy Methyl) -2-trifluoromethyloxetane, 3-((meth) acryloyloxymethyl) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, and 2- ( (Meth) acryloyloxymethyl) -4-trifluoromethyl oxetane.

Examples of the crosslinkable monomer having an oxazoline group as a heat crosslinkable crosslinkable group and having an olefinic double bond, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl- 5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, And 2-isopropenyl-5-ethyl-2-oxazoline.

Examples of the crosslinkable monomer having two or more olefinic double bonds per molecule include allyl (meth) acrylate, ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth). Acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane-tri (meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyle ether, Tetraallyloxyethane, trimethylolpropane-diallyl ether, allyl or vinyl ether of polyfunctional alcohols other than the above, triallylamine, methylenebisacrylamide, and divinylbenzene.

Among these, ethylene dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are particularly preferred as the crosslinkable monomer.

Moreover, as a crosslinkable monomer, you may use individually by 1 type and may use it combining 2 or more types by arbitrary ratios.

The content ratio of the crosslinkable monomer unit in the copolymer of the (meth) acrylic acid ester monomer and the (meth) acrylonitrile monomer is preferably 0.1% by weight or more, preferably 10% by weight or less, and more preferably It is 5% by weight or less. By setting the content ratio of the crosslinkable monomer unit within the above range, deformation of the heat-resistant layer due to elution of the polymer into the electrolytic solution can be suppressed, and cycle characteristics of the secondary battery can be improved.

One type of binder may be used alone, or two or more types may be used in combination at any ratio.

The weight average molecular weight of the polymer forming the binder is preferably 10,000 or more, more preferably 20,000 or more, and preferably 1,000,000 or less, and more preferably 500,000 or less. When the weight average molecular weight of the polymer forming the binder is in the above range, it is easy to improve the strength of the porous membrane separator and the dispersibility of the non-conductive particles.

The glass transition temperature of the binder is preferably -60 ° C or higher, more preferably -55 ° C or higher, particularly preferably -50 ° C or higher, usually 20 ° C or lower, preferably 15 ° C or lower, and more preferably Is 5 ° C or less. By setting the glass transition temperature of the binder to the lower limit of the above range, the strength of the binder can be increased and the strength of the porous membrane can be improved. Moreover, the flexibility of a porous membrane separator can be made high by setting below an upper limit.

Moreover, it is preferable to use a particulate-form binder as a binder. By using a particulate binder, the binder can bind to the non-conductive particles in dots rather than in cotton. For this reason, the voids between non-conductive particles can be enlarged, and the porosity of the porous membrane can be increased. In this case, usually, the binder becomes particles of the water-insoluble polymer.

When the binder is particulate, the volume average particle diameter D50 of the particulate binder is preferably 50 nm or more, more preferably 70 nm or more, preferably 500 nm or less, and more preferably 400 nm or less. When the volume average particle diameter D50 of the particulate binder is in the above range, the strength and flexibility of the resulting porous membrane separator can be improved.

The amount of the binder in the slurry composition for a porous membrane is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, particularly preferably 0.5 parts by weight or more, preferably 100 parts by weight of non-conductive particles Is 20 parts by weight or less, more preferably 15 parts by weight or less, particularly preferably 10 parts by weight or less. By setting the amount of the binder to be more than the lower limit of the above range, the binding property between the separator base material and the porous membrane can be increased. Moreover, the fall of ion conductivity by a porous membrane separator can be prevented by setting below an upper limit.

The manufacturing method of a binder is not specifically limited, For example, you may use any method, such as solution polymerization method, suspension polymerization method, and emulsion polymerization method. Especially, since it can superpose | polymerize in water and can be used as a material of the slurry composition for porous films as it is, an emulsion polymerization method and suspension polymerization method are preferable. Moreover, when manufacturing a binder, it is preferable to contain a dispersing agent in the reaction system. Dispersants may be used in conventional synthesis. The amount of the dispersant can be arbitrarily set, and is usually about 0.01 part by weight or more and 10 parts by weight or less with respect to 100 parts by weight of the total monomer. By using a dispersant, sedimentation and aggregation of solids in the slurry can be suppressed.

[1.1.2.6. Other ingredients]

The slurry composition for porous membranes may contain arbitrary components other than the above-mentioned thing as needed. As such a component, one that does not affect the battery reaction can be used. Examples of these components include isothiazoline-based compounds, chelating compounds, pyrithione compounds, dispersants, leveling agents, antioxidants, thickeners, antifoaming agents, and surfactants. Moreover, the electrolyte solution additive which has functions, such as suppressing electrolyte decomposition, is also mentioned. Moreover, these components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[1.1.2.7. Condition and production method of slurry composition for porous membranes]

The slurry composition for porous membranes is usually in a fluid phase. In the slurry composition for a porous membrane, the non-conductive particles are dispersed in water, and the water-soluble high molecular compound and the low molecular compound X are dissolved in water. Moreover, in the slurry composition for porous membranes, a part of the water-soluble polymer compound is usually free in water, but the other part adsorbs on the surface of the non-conductive particle, so that the non-conductive particle becomes a stable layer of the water-soluble polymer compound. Covered, the dispersibility of the non-conductive particles in water is improved. For this reason, the coating composition at the time of apply | coating the slurry composition for porous films to a separator base material is favorable. Moreover, when the slurry composition for porous films contains a binder, the said binder may be dissolved in water or may be dispersed. When using a particulate binder as a binder, normally, the binder is dispersed in water.

The slurry composition for a porous membrane is obtained by mixing non-conductive particles, a water-soluble polymer compound, water, and a low-molecular compound X, and a binder and optional components as necessary. Mixing may be performed by supplying the above components to the mixer in a batch. Moreover, you may divide and mix in multiple processes in arbitrary order. Moreover, when the water-soluble polymer compound has an acidic group, the water-soluble polymer compound may form a salt with the low-molecular compound X. In that case, as a result, if a slurry composition for a porous membrane containing a water-soluble polymer compound and a low-molecular compound X is obtained, instead of separately mixing the water-soluble polymer compound and the low-molecular compound X, salts of the water-soluble polymer compound and the low-molecular compound X are mixed. You may do it.

As the mixer, for example, a ball mill, sand mill, pigment disperser, thresher, ultrasonic disperser, homogenizer, planetary mixer, hobart mixer, or the like may be used.

[1.1.3. apply]

After preparing the slurry composition for a porous membrane, the slurry composition for a porous membrane is apply | coated on a separator base material. Thereby, the film of the slurry composition for porous films is formed on a separator base material.

There is no limitation as a method of applying the slurry composition for a porous membrane. Examples of the coating method include doctor blade method, dip method, die coating method, reverse roll method, direct roll method, gravure method, extrusion method, brush coating method and the like.

The coating amount of the slurry composition for a porous membrane is generally set to a range in which a porous membrane having a desired thickness is obtained.

[1.1.4. dry]

After forming the membrane of the slurry composition for porous membranes on a separator base material, the membrane is dried. Water is removed from the membrane of the slurry composition for porous membranes by drying, and a porous membrane is obtained. Moreover, during drying, most of the low molecular weight compound X is vaporized and removed from the membrane of the slurry composition for porous membranes. Thereby, the water resistance of the porous membrane is remarkably improved, and the porous membrane is hardly soluble in water.

As a drying method, drying by wind, such as warm air, hot air, and low-humidity air, vacuum drying, the drying method by irradiation with energy rays, such as infrared rays, far infrared rays, and electron beams, etc. are mentioned, for example.

The temperature during drying is preferably 40 ° C or higher, more preferably 45 ° C or higher, particularly preferably 50 ° C or higher, preferably 90 ° C or lower, more preferably 80 ° C or lower, particularly preferably 70 It is below ℃. By setting the drying temperature to be at least the lower limit of the above range, moisture and the low molecular compound X from the slurry composition for a porous membrane can be efficiently removed. Moreover, it can coat by suppressing shrinkage by heat of a separator base material by setting it below an upper limit.

The drying time is preferably 5 seconds or more, more preferably 10 seconds or more, particularly preferably 15 seconds or more, preferably 3 minutes or less, more preferably 2 minutes or less, particularly preferably 1 minute or less to be. By setting the drying time to the lower limit of the above range, water can be sufficiently removed from the porous membrane, so that the output characteristics of the battery can be improved. Moreover, manufacturing efficiency can be improved by making it below an upper limit.

[1.1.5. Other operations]

In the process of obtaining a porous membrane, you may perform arbitrary operations other than what was mentioned above. For example, the porous membrane may be pressurized by a press method such as a mold press or a roll press. By performing pressure treatment, the binding property of a separator base material and a porous film can be improved. However, if the pressure treatment is performed excessively, the porosity of the porous membrane may be impaired, so it is preferable to appropriately control the pressure and the pressing time. In addition, it is preferable to dry in a vacuum drying or dry room to remove residual moisture. It is also preferable to heat-treat, whereby the thermal crosslinkable group in the binder is crosslinked, and the binding force is further improved.

[1.1.6. Porous membrane]

A porous film is formed on the separator substrate by going through the steps described above. This porous membrane contains non-conductive particles, a water-soluble polymer compound, and a binder and optional components as necessary. The amount of the non-conductive particles, the water-soluble polymer compound, and the binder is usually the same as the amount contained in the slurry composition for a porous membrane.

In the porous membrane, the pores between the non-conductive particles form pores, so the porous membrane has a porous structure. For this reason, since the porous membrane has liquid permeability, the movement of ions is not impeded by the porous membrane. Therefore, in the lithium ion secondary battery, the porous membrane does not inhibit the battery reaction. In addition, since the non-conductive particles do not have conductivity, insulating properties can be exhibited in the porous film. In addition, since the rigidity of the porous membrane can be increased by containing the non-conductive particles, the rigidity of the porous membrane separator can also be increased, and a short circuit can be stably prevented.

This porous membrane is excellent in water resistance, and is poorly soluble in water. That is, the water-soluble polymer compound contained in the porous membrane does not readily dissolve in water. Therefore, the porous membrane has a high binding property to the separator substrate.

Moreover, since the water is removed by drying the porous membrane, the moisture content is small. Therefore, since gas generation by water can be suppressed, a decrease in discharge capacity due to charging and discharging can be suppressed. For this reason, it is possible to improve the cycle characteristics of a lithium ion secondary battery.

Moreover, since the low-molecular-weight compound X is removed from the slurry composition for a porous membrane at the time of drying, the concentration of the low-molecular-weight compound X remaining in the porous membrane becomes small. Specifically, the concentration of the low-molecular compound X in the porous membrane is usually 1,000 ppm or less, preferably 500 ppm or less, more preferably 200 ppm or less per weight of the porous membrane. The lower limit is ideally 0 ppm, but is usually 1 ppm or more.

The thickness of the porous membrane is preferably 0.1 µm or more, more preferably 0.2 µm or more, particularly preferably 0.3 µm or more, preferably 20 µm or less, more preferably 15 µm or less, particularly preferably 10 Or less. By making the thickness of the porous membrane more than the lower limit of the above range, the heat resistance of the porous membrane can be increased. Moreover, the fall of the ion conductivity by a porous membrane can be suppressed by setting below an upper limit.

[1.2. Step of obtaining an adhesive layer]

In the process of obtaining an adhesive layer, a slurry composition for an adhesive layer is applied onto the porous film and dried to obtain an adhesive layer. At this time, since the porous membrane has high water resistance, even if the slurry composition for an adhesive layer containing water is applied, the porous membrane does not readily dissolve.

[1.2.1. Slurry composition for adhesive layer]

The slurry composition for an adhesive layer contains particulate polymer and water. Moreover, the slurry composition for adhesive layers may contain a binder.

[1.2.1.1. Particulate polymer]

As a particulate polymer, glass transition of 10 degrees C or more, preferably 30 degrees C or more, more preferably 40 degrees C or more, and usually 110 degrees C or less, preferably 100 degrees C or less, more preferably 90 degrees C or less Particle polymers having temperature are used. When the glass transition temperature of the particulate polymer is equal to or more than the lower limit of the above range, softening of the particulate polymer can be suppressed during storage, transportation, and handling of the porous membrane separator, thereby preventing blocking. Moreover, the heat resistance of an adhesive layer improves by using a particulate polymer with a high glass transition temperature. Therefore, even when the battery becomes hot at the time of use of the lithium ion secondary battery, peeling of the porous membrane separator can be prevented, and the safety of the battery can be enhanced. Moreover, when it is below an upper limit, when a porous membrane separator is bonded to an electrode, a particulate polymer can be softened easily by heat. Moreover, it is possible to heat-seal the adhesive layer at a low temperature that does not impair the elements constituting the battery, such as a separator substrate. Therefore, it becomes possible to easily bond the porous membrane separator and the electrode by hot pressing.

As the particulate polymer, various polymers having a glass transition temperature in the above range can be used.

Especially, as a particulate polymer, the polymer containing the structural unit which has a structure formed by superposing | polymerizing an acrylic acid ester monomer (it may be hereafter referred to as "acrylic acid ester monomer unit" suitably) is preferable.

Examples of the acrylic acid ester monomers include methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, and heptyl acrylic And acrylic acid alkyl esters such as acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, and stearyl acrylate. These may use only 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the acrylic acid ester monomer in the total amount of monomers in the particulate polymer is usually 1% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more, and usually 95% by weight or less, preferably It is 90% by weight or less, and more preferably 85% by weight or less. When the ratio of the acrylic acid ester monomer is equal to or more than the lower limit of the above range, the adhesiveness between the adhesive layer and the porous membrane can be enhanced. Moreover, by setting below an upper limit, the swelling property of the adhesive layer with respect to the electrolytic solution can be suppressed and the ion conductivity of the porous membrane separator can be increased. Here, the ratio of the acrylic acid ester monomer in the total amount of the monomers of the particulate polymer is generally the same as the ratio of the acrylic acid ester monomer units in the particulate polymer.

Moreover, the particulate polymer is preferably a polymer containing a structural unit having a structure formed by polymerizing an ethylenically unsaturated carboxylic acid monomer (hereinafter, sometimes referred to as “ethylenically unsaturated carboxylic acid monomer unit”). Do.

Examples of the ethylenically unsaturated carboxylic acid monomer include ethylenically unsaturated monocarboxylic acid, ethylenically unsaturated dicarboxylic acid, and an acid anhydride thereof. Acrylic acid, methacrylic acid, crotonic acid, etc. are mentioned as an example of ethylenically unsaturated monocarboxylic acid. Maleic acid, fumaric acid, itaconic acid, etc. are mentioned as an example of ethylenically unsaturated dicarboxylic acid. Examples of the acid anhydride of the ethylenically unsaturated dicarboxylic acid include maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride. Among these, ethylenically unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid are preferred. This is because the dispersibility of the particulate polymer in water can be further improved. These may use only 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the ethylenically unsaturated carboxylic acid monomer in the total amount of the monomers of the particulate polymer is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, and usually 95% by weight Hereinafter, it is preferably 90% by weight or less, and more preferably 85% by weight or less. By making the ratio of the ethylenically unsaturated carboxylic acid monomer more than the lower limit of the above range, the blocking resistance of the porous membrane separator can be enhanced. Moreover, the adhesive strength of a porous membrane separator and an electrode can be raised by setting below an upper limit. Here, the ratio of the ethylenically unsaturated carboxylic acid monomer in the total amount of the monomers of the particulate polymer is generally the same as the ratio of the ethylenically unsaturated carboxylic acid monomer units in the particulate polymer.

Moreover, as a particulate polymer, the polymer containing the structural unit which has a structure formed by superposing | polymerizing an aromatic vinyl monomer (Hereinafter, it may be called an "aromatic vinyl monomer unit" as appropriate.) Is preferable.

Examples of the aromatic vinyl monomers include styrene, α-methylstyrene, vinyltoluene, and divinylbenzene. Among them, styrene is preferred. These may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The proportion of the aromatic vinyl monomer in the total amount of the monomers of the particulate polymer is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, and usually 95% by weight or less, preferably Is 90% by weight or less, and more preferably 85% by weight or less. The blocking resistance of the porous membrane separator can be improved by setting the proportion of the aromatic vinyl monomer to be at least the lower limit of the above range. Moreover, the adhesive strength of a porous membrane separator and an electrode can be raised by setting below an upper limit. Here, the ratio of the aromatic vinyl monomer in the total amount of the monomers of the particulate polymer is generally the same as the ratio of the aromatic vinyl monomer units in the particulate polymer.

Moreover, as a particulate polymer, the polymer containing the structural unit which has a structure formed by superposing | polymerizing a (meth) acrylonitrile monomer (Hereinafter, it may be called a "(meth) acrylonitrile monomer unit" as appropriate.) Is preferable. Do.

As a (meth) acrylonitrile monomer, acrylonitrile and methacrylonitrile are mentioned, for example. As the (meth) acrylonitrile monomer, only acrylonitrile may be used, only methacrylonitrile may be used, or both acrylonitrile and methacrylonitrile may be used in combination at any ratio.

The proportion of the (meth) acrylonitrile monomer in the total amount of the monomers of the particulate polymer is usually 0.1% by weight or more, preferably 0.5% by weight or more, more preferably 1% by weight or more, and usually 95% by weight Hereinafter, it is preferably 90% by weight or less, and more preferably 85% by weight or less. By setting the ratio of the (meth) acrylonitrile monomer to the lower limit of the above range, the adhesive strength between the porous membrane separator and the electrode can be increased. Moreover, binding property of an adhesive layer and a porous film can be improved by setting below an upper limit. Here, the ratio of the (meth) acrylonitrile monomer in the total amount of the monomers of the particulate polymer is generally the same as the ratio of the (meth) acrylonitrile monomer units in the particulate polymer.

Moreover, it is preferable to use what has a crosslinkable group as a particulate polymer. Therefore, it is preferable to use a crosslinkable monomer as a monomer of the particulate polymer. Here, the crosslinkable monomer refers to a monomer capable of forming a crosslinked structure during polymerization or after polymerization by heating.

As a crosslinkable monomer, the monomer which has thermal crosslinkability is mentioned, for example. More specifically, for example, a monofunctional monomer having a heat crosslinkable crosslinkable group and one olefinic double bond per molecule; a polyfunctional monomer having two or more olefinic double bonds per molecule is exemplified.

Examples of the heat crosslinkable crosslinkable group include an epoxy group, an N-methylolamide group, an oxetanyl group, an oxazoline group, and combinations thereof. Among these, the epoxy group is more preferable from the viewpoint of easy control of crosslinking and crosslinking density.

Examples of the crosslinkable monomer having an epoxy group as a heat crosslinkable crosslinkable group and having an olefinic double bond are vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, and o-allylphenyl glycidyl ether. Unsaturated glycidyl ethers such as butadiene monoepoxide, chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9- Monoepoxides of dienes such as cyclododecadiene or polyene; alkenyl epoxides such as 3,4-epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; And glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sorbate, glycidyl linoleate, glycidyl-4-methyl -3-pentenoate, glycidyl ester of 3-cyclohexenecarboxylic acid, 4-methyl-3-cyclohexenecarboxylic acid Glycidyl of unsaturated carboxylic acids such as receiving dill ester may be mentioned pyridyl ester.

Examples of the crosslinkable monomer having an N-methylolamide group as a heat crosslinkable crosslinkable group and having an olefinic double bond include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide. You can.

Examples of the crosslinkable monomer having an oxetanyl group as a heat crosslinkable crosslinkable group and having an olefinic double bond include 3-((meth) acryloyloxymethyl) oxetane and 3-((meth) acryloyloxy Methyl) -2-trifluoromethyloxetane, 3-((meth) acryloyloxymethyl) -2-phenyloxetane, 2-((meth) acryloyloxymethyl) oxetane, and 2- ( (Meth) acryloyloxymethyl) -4-trifluoromethyl oxetane.

Examples of the crosslinkable monomer having an oxazoline group as a heat crosslinkable crosslinkable group and having an olefinic double bond, 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl- 5-methyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, And 2-isopropenyl-5-ethyl-2-oxazoline.

Examples of the crosslinkable monomer having two or more olefinic double bonds per molecule include allyl (meth) acrylate, ethylene di (meth) acrylate, diethylene glycol di (meth) acrylate, and triethylene glycol di (meth). Acrylate, tetraethylene glycol di (meth) acrylate, trimethylolpropane-tri (meth) acrylate, dipropylene glycol diallyl ether, polyglycol diallyl ether, triethylene glycol divinyl ether, hydroquinone diallyle ether, Tetraallyloxyethane, trimethylolpropane-diallyl ether, allyl or vinyl ether of polyfunctional alcohols other than the above, triallylamine, methylenebisacrylamide, and divinylbenzene.

Among these examples, ethylene dimethacrylate, allyl glycidyl ether, and glycidyl methacrylate are particularly preferred as the crosslinkable monomer.

Moreover, as a crosslinkable monomer, you may use individually by 1 type and may use it combining 2 or more types by arbitrary ratios.

The proportion of the crosslinkable monomer in the total amount of the monomers of the particulate polymer is usually 0.01% by weight or more, preferably 0.05% by weight or more, and usually 5% by weight or less, preferably 3% by weight or less, more preferably Is 2% by weight or less. The strength of the porous membrane can be increased by setting the ratio of the crosslinkable monomer to the lower limit of the above range. Moreover, swelling by the electrolyte solution of a porous membrane can be suppressed. Moreover, the flexibility of a porous membrane can be made high by setting below an upper limit. Here, the ratio of the crosslinkable monomer in the total amount of the monomers of the particulate polymer is generally the same as the ratio of the crosslinkable monomer units in the particulate polymer.

The volume average particle diameter D50 of the particulate polymer is preferably 10 nm or more, more preferably 50 nm or more, particularly preferably 100 nm or more, preferably 1000 nm or less, more preferably 800 nm or less, particularly preferably It is 500 nm or less. When the volume average particle diameter D50 of the particulate polymer is greater than or equal to the lower limit of the above range, it is possible to suppress an increase in the particle filling rate in the porous membrane, so that the ionic conductivity in the porous membrane can be suppressed, and excellent cycle characteristics can be realized. . Moreover, since it becomes easy to control the dispersion state of a slurry by being below an upper limit, manufacture of a porous film of uniform predetermined thickness becomes easy.

[1.2.1.2. bookbinder]

The slurry composition for an adhesive layer may contain a binder. By containing a binder, the adhesiveness of the adhesive layer to the porous film can be enhanced.

As a binder, the thing similar to the binder demonstrated in the term of the slurry composition for porous films can be used, for example. However, it is assumed that the particulate polymer whose glass transition temperature falls within the temperature range described in the section of the particulate polymer is treated as a particulate polymer, not a binder.

The amount of the binder in the slurry composition for an adhesive layer is preferably 0.1 parts by weight or more, more preferably 0.5 parts by weight or more, particularly preferably 1 part by weight or more, and preferably 20 parts by weight or more with respect to 100 parts by weight of the particulate polymer. It is less than or equal to 15 parts by weight, more preferably less than or equal to 15 parts by weight, particularly preferably less than or equal to 10 parts by weight. By setting the amount of the binder to be more than the lower limit of the above range, the binding force between the particulate polymers can be improved, and peeling of the particulate polymers can be prevented. Moreover, by setting it below an upper limit, it can suppress that the ionic conductivity of an adhesive layer falls, and it can realize excellent cycling characteristics.

[1.2.1.3. water]

It is preferable that the amount of water in the slurry composition for an adhesive layer is adjusted so that the viscosity of the slurry composition for an adhesive layer is within a preferred range for application, depending on the type of the particulate polymer and the binder used if necessary. Specifically, the concentration of the solid content of the above-mentioned particulate polymer and the binder and optional components used as required is preferably 10% by weight or more, more preferably 20% by weight or more, and preferably 60% by weight. % Or less, more preferably 50% by weight or less of water is used.

[1.2.1.4. Other ingredients]

The slurry composition for an adhesive layer may contain arbitrary components other than the above-mentioned thing as needed. As such a component, one that does not affect the battery reaction can be used. Examples of these components include viscosity adjustment, water-soluble polymers for preventing sedimentation, and wetting agents for improving wettability to organic separators. Moreover, these components may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

[1.2.1.5. Condition and manufacturing method of slurry composition for adhesive layer]

The slurry composition for an adhesive layer is usually in a fluid phase. In the slurry composition for an adhesive layer, the particulate polymer is dispersed in water. Moreover, the binder may be dispersed in water or dissolved. When using a particulate binder as a binder, normally, the binder is dispersed in water.

The manufacturing method of the slurry composition for adhesive layers is not specifically limited. Usually, it is obtained by mixing the above-mentioned particulate polymer and water, and the binder and optional components used as needed. The mixing order is not particularly limited. Further, the mixing method is not particularly limited.

[1.2.2. apply]

After preparing the slurry composition for an adhesive layer, the slurry composition for an adhesive layer is applied on a porous membrane. Thereby, a film of the slurry composition for an adhesive layer is formed on the porous film.

There is no limitation as a method of applying the slurry composition for an adhesive layer. Examples of the coating method include doctor blade method, dip method, die coating method, reverse roll method, direct roll method, gravure method, extrusion method, brush coating method and the like.

The coating amount of the slurry composition for an adhesive layer is usually within a range in which an adhesive layer having a desired thickness is obtained.

[1.2.3. dry]

After forming a film of the slurry composition for an adhesive layer on a porous film, the film is dried. Water is removed from the film of the slurry composition for an adhesive layer by drying, and an adhesive layer is obtained.

As a drying method, drying by wind, such as warm air, hot air, and low-humidity air, vacuum drying, the drying method by irradiation with energy rays, such as infrared rays, far infrared rays, and electron beams, etc. are mentioned, for example.

The temperature during drying is preferably 40 ° C or higher, more preferably 45 ° C or higher, particularly preferably 50 ° C or higher, preferably 80 ° C or lower, more preferably 75 ° C or lower, particularly preferably 70 It is below ℃. By setting the drying temperature to the lower limit of the above range, moisture from the slurry composition for an adhesive layer can be efficiently removed. Moreover, it can coat by suppressing shrinkage by heat of a separator base material by setting it below an upper limit.

The drying time is preferably 5 seconds or more, more preferably 10 seconds or more, particularly preferably 15 seconds or more, preferably 3 minutes or less, more preferably 2 minutes or less, particularly preferably 1 minute or less to be. By setting the drying time to the lower limit of the above range, moisture from the slurry composition for an adhesive layer can be sufficiently removed. Moreover, shrinkage by the heat of a separator base material can be suppressed by using below an upper limit.

[1.2.4. Other operations]

In the process of obtaining an adhesive layer, you may perform arbitrary operations other than what was mentioned above. For example, in order to remove residual moisture, a drying treatment may be performed in a vacuum drying or a dry room, or a heating treatment may be performed.

[1.2.5. Adhesive layer]

By passing through the above-described process, an adhesive layer is formed on the porous film to obtain a porous film separator. This adhesive layer contains a particulate polymer and, if necessary, a binder and optional components. The amount of the particulate polymer and the binder is usually the same as the amount contained in the slurry composition for an adhesive layer.

Since the pores between the particulate polymers in the adhesive layer form pores, the adhesive layer has a porous structure. For this reason, since the adhesive layer has liquid permeability, the movement of ions is not prevented by the adhesive layer. Therefore, in the lithium ion secondary battery, the battery reaction is not inhibited by the adhesive layer. Moreover, since the particulate polymer does not have conductivity, insulating properties can be exhibited in the adhesive layer.

In such an adhesive layer, the particulate polymer can be softened by heating. Therefore, the adhesive layer can be favorably adhered to other members such as an electrode by being press-bonded while heating. Therefore, the porous membrane separator provided with the adhesive layer can adhere to the electrode with high adhesive strength. Moreover, since the particulate polymer has a high glass transition temperature, the adhesive layer has high heat resistance. Therefore, even when the lithium ion secondary battery has a high temperature due to charging and discharging, the porous membrane separator is unlikely to peel from the electrode. Therefore, the short circuit can be prevented more stably, so that it is possible to improve the safety.

The thickness of the adhesive layer is preferably 0.1 µm or more, more preferably 0.2 µm or more, particularly preferably 0.3 µm or more, preferably 8.0 µm or less, more preferably 5.0 µm or less, particularly preferably 3.0 µm. Is below. The adhesive strength of the porous membrane separator and the electrode can be increased by making the thickness of the adhesive layer more than the lower limit of the above range. Moreover, the ion conductivity of a porous membrane separator can be made high by setting below an upper limit.

[1.3. Other processes]

In the method for producing a porous membrane separator of the present invention, as long as a desired porous membrane separator is obtained, steps other than those described above may be performed. For example, in order to remove residual moisture, a drying treatment may be performed in a vacuum drying or a dry room, or a heating treatment may be performed.

[2. Porous membrane separator]

The porous membrane separator manufactured by the method for producing a porous membrane separator of the present invention includes a separator substrate, a porous membrane, and an adhesive layer in this order. Since the electrolyte can penetrate the separator base material, the porous film, and the adhesive layer, the porous film separator does not adversely affect the battery characteristics. Moreover, since the porous film is difficult to elute into the slurry composition for an adhesive layer, the strength and binding property of the porous film are good. Therefore, since the adhesive strength of the porous membrane separator to the electrode can be increased, the safety of the lithium ion secondary battery can be improved. In addition, the particulate polymer contained in the adhesive layer is unlikely to soften in the normal use environment of the porous membrane separator. Therefore, the porous membrane separator has excellent blocking resistance.

The porous membrane separator may include components other than the separator substrate, the porous membrane, and the adhesive layer.

Moreover, the porous film and the adhesive layer may be formed only on one side of the separator substrate or on both sides.

[3. Manufacturing method of the laminate]

The method for producing a laminate for a lithium ion secondary battery of the present invention includes pressure bonding the electrode and the porous film separator produced by the method for producing the porous film separator of the present invention.

[3.1. electrode]

The electrode usually includes a current collector and an electrode active material layer formed on the current collector.

[3.1.1. Current collector]

For the current collector, a material having electrical conductivity and also being electrochemically durable can be used. Among them, from the viewpoint of having heat resistance, metal materials such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, and platinum are preferred. Among them, aluminum is particularly preferred for the positive electrode, and copper is particularly preferred for the negative electrode.

The shape of the current collector is not particularly limited, but, for example, a sheet having a thickness of 0.001 mm or more and 0.5 mm or less is preferable.

It is preferable to use the current collector by roughening in advance in order to increase the adhesive strength with the electrode active material layer. As a roughening method, a mechanical polishing method, an electrolytic polishing method, a chemical polishing method, etc. are mentioned, for example. In the mechanical polishing method, for example, abrasive paper to which abrasive particles are adhered, a grindstone, an emery buff, a wire brush with a steel wire, or the like can be used.

Moreover, in order to improve the adhesive strength and conductivity with the electrode active material layer, an intermediate layer may be formed on the surface of the current collector.

[3.1.2. Electrode active material layer]

The electrode active material layer contains an electrode active material. In the following description, among the electrode active materials, the electrode active material for a positive electrode is sometimes referred to as a “positive electrode active material”, and the electrode active material for a negative electrode is sometimes referred to as a “negative electrode active material”.

As the electrode active material, one capable of reversibly inserting and releasing lithium ions by applying a potential in the electrolyte can be used. As the electrode active material, an inorganic compound may be used, or an organic compound may be used.

The positive electrode active material is largely classified into an inorganic compound and an organic compound. As a positive electrode active material which consists of an inorganic compound, transition metal oxide, a complex oxide of lithium and transition metal, transition metal sulfide, etc. are mentioned, for example. As said transition metal, Fe, Co, Ni, Mn, etc. are used, for example. Specific examples of the inorganic compound used in the positive electrode active material include lithium-containing composite metal oxides such as LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , and LiFeVO ₄ ; transitions such as TiS ₂ , TiS ₃ , and amorphous MoS ₂ Metal sulfides; transition metal oxides such as Cu ₂ V ₂ O ₃ , amorphous V ₂ OP ₂ O ₅ , MoO ₃ , V ₂ O ₅ , and V ₆ O ₁₃ . On the other hand, as a positive electrode active material which consists of organic compounds, conductive polymers, such as polyacetylene and poly-p-phenylene, are mentioned, for example.

Moreover, you may use the positive electrode active material which consists of a composite material combining an inorganic compound and an organic compound.

Moreover, a composite material covered with a carbon material may be produced, for example, by subjecting the iron-based oxide to reduction firing in the presence of a carbon source material, and use the composite material as a positive electrode active material. Although the iron-based oxide tends to have insufficient electrical conductivity, it can be used as a high-performance positive electrode active material by using such a composite material.

Moreover, you may use what partially substituted the said compound as a positive electrode active material.

As for these positive electrode active materials, only 1 type may be used and 2 or more types may be used in combination in arbitrary ratios.

The particle diameter of the positive electrode active material is appropriately selected in balance with other constituent requirements of the battery. From the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics, the volume average particle diameter D50 of the positive electrode active material is usually 0.1 µm or more, preferably 1 µm or more, and usually 50 µm or less, preferably 20 µm or less to be. When the volume average particle diameter D50 of the positive electrode active material is within this range, a battery with a large charge / discharge capacity can be obtained, and the slurry composition for an active material layer and an electrode are easily handled in manufacturing.

Examples of the negative electrode active material include carbonaceous materials such as amorphous carbon, graphite, natural graphite, mesocarbon microbeads, and pitch-based carbon fibers; conductive polymers such as polyacene, and the like. Further, metals such as silicon, tin, zinc, manganese, iron and nickel, and alloys thereof; oxides of the metals or alloys; sulfates of the metals or alloys, and the like. Moreover, you may use metal lithium; lithium alloys, such as Li-Al, Li-Bi-Cd, and Li-Sn-Cd; lithium transition metal nitride; silicon, etc. may be used. Moreover, you may use the electrode active material which attached the electrically conductive material to the surface by a mechanical modification method. As for these negative electrode active materials, only 1 type may be used and 2 or more types may be used in combination in arbitrary ratios.

The particle diameter of the negative electrode active material is appropriately selected in balance with other constituent requirements of the battery. From the viewpoint of improving battery characteristics such as initial efficiency, load characteristics, and cycle characteristics, the volume average particle diameter D50 of the negative electrode active material is usually 1 μm or more, preferably 15 μm or more, and usually 50 μm or less, preferably 30 µm or less.

It is preferable that the electrode active material layer contains a binder in addition to the electrode active material. By containing a binder, the binding property of the electrode active material layer in the electrode is improved, and the strength against the mechanical force exerted in a process such as winding of the electrode increases. In addition, since the electrode active material layer in the electrode is less likely to be detached, the risk of short circuit due to the detached material is reduced.

Various polymer components can be used as the binder for the electrode active material layer. For example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives, etc. are used. May be Moreover, you may use the same binder as what was demonstrated in the term of the porous membrane or the adhesive layer of a porous membrane separator. Moreover, one type of binder may be used alone, or two or more types may be used in combination at any ratio.

The amount of the binder in the electrode active material layer is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, particularly preferably 0.5 parts by weight or more, and preferably 5 parts by weight with respect to 100 parts by weight of the electrode active material. Parts or less, more preferably 4 parts by weight or less, particularly preferably 3 parts by weight or less. When the amount of the binder is within the above range, it is possible to prevent the electrode active material from falling off from the electrode without inhibiting the battery reaction.

The electrode active material layer may contain optional components other than the electrode active material and the binder, as long as the effects of the present invention are not significantly impaired. Examples thereof include a conductive material and a reinforcing material. Moreover, as an arbitrary component, 1 type may be used individually and 2 or more types may be used combining it in arbitrary ratios.

Examples of the conductive material include acetylene black, Ketjen black, carbon black, graphite, vapor-grown carbon fibers, conductive carbon such as carbon nanotubes; carbon powders such as graphite; fibers and foils of various metals, and the like. By using a conductive material, electrical contact between the electrode active materials can be improved, and in particular, when used in a lithium secondary battery, discharge characteristics can be improved.

As the reinforcing material, for example, various inorganic and organic spherical, plate, rod, or fibrous fillers can be used.

The amount of the conductive material and the reinforcing material used is usually 0 parts by weight or more, preferably 1 part by weight or more, and usually 20 parts by weight or less, preferably 10 parts by weight or less, with respect to 100 parts by weight of the electrode active material.

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

The method for manufacturing the electrode active material layer is not particularly limited. The electrode active material layer can be produced, for example, by applying a slurry containing an electrode active material and a solvent and, if necessary, a binder and optional components on a current collector and drying it. As the solvent, both water and organic solvents can be used.

[3.2. Pressure bonding]

A laminate for a lithium secondary battery is obtained by pressure-bonding the electrode and the porous membrane separator. When the electrode is provided with an electrode active material layer, the electrode and the porous membrane separator are usually overlapped so that the electrode active material layer of the electrode and the adhesive layer of the porous membrane separator face each other.

The size of the pressure applied at the time of adhesion is usually 0.01 MPa or more, preferably 0.05 MPa or more, more preferably 0.1 MPa or more, and usually 2 MPa or less, preferably 1.5 MPa or less, more preferably 1 MPa Is below. When the pressure is set to the lower limit of the above range, the electrode plate and the adhesive layer can be sufficiently adhered. Moreover, the rupture of a porous membrane separator at the time of adhesion can be prevented by setting it below an upper limit.

Moreover, at the time of adhesion, the porous membrane separator is usually heated. The specific temperature at this time is usually at least the glass transition temperature of the particulate polymer contained in the adhesive layer of the porous membrane separator, preferably at least 40 ° C, more preferably at least 50 ° C, particularly preferably at least 60 ° C, Moreover, it is 100 degrees C or less preferably, More preferably, it is 95 degrees C or less, Especially preferably, it is 90 degrees C or less. The electrode and the porous membrane separator can be firmly adhered by setting the temperature to the lower limit of the above range. Moreover, deterioration by the heat of the element which comprises a battery can be prevented by setting below an upper limit.

The time for applying pressure and heat, as described above, is preferably 0.5 seconds or more, more preferably 1 second or more, particularly preferably 2 seconds or more, preferably 30 seconds or less, more preferably 20 seconds or less, It is particularly preferably 10 seconds or less. The electrode and the porous membrane separator can be firmly bonded by setting the pressure and the time for applying the heat to the lower limit of the above range. Moreover, by setting it as an upper limit or less, the rupture of the porous membrane separator at the time of adhesion can be prevented.

By performing pressure bonding as described above, a laminate for a lithium ion secondary battery comprising an electrode and a porous membrane separator is obtained. At this time, the electrodes may be adhered to only one side of the porous membrane separator, or the electrodes may be adhered to both sides. For example, when using a porous membrane separator having a porous membrane and an adhesive layer on both sides of a separator substrate, a laminate for a lithium ion secondary battery having a positive electrode, a porous membrane separator, and a negative electrode in this order can be produced. .

[3.3. Other processing]

In the manufacturing method of the laminated body for lithium ion secondary batteries of this invention, in addition to the process mentioned above, you may perform arbitrary processes further.

For example, after winding or laminating an electrode and a separator, you may embed it in a laminate film, inject an electrolyte solution, seal the cell, pressurize the cell, and adhere the electrode to the separator.

[4. Lithium ion secondary battery]

A lithium ion secondary battery can be produced by using the porous membrane separator obtained by the above-described manufacturing method or a laminate for a lithium ion secondary battery. The lithium ion secondary battery is provided with a positive electrode, a porous membrane separator, and a negative electrode in this order, and further includes an electrolyte solution. This lithium ion secondary battery has high safety because the adhesion between the porous membrane separator and the electrode is high, and the heat resistance of the porous membrane separator is usually high.

As the porous membrane separator, one produced by the above-described manufacturing method is used.

Moreover, what was demonstrated by the term of the manufacturing method of the laminated body for lithium ion secondary batteries can be used as an electrode, for example.

As the electrolyte, for example, one in which a lithium salt is dissolved as a supporting electrolyte in a non-aqueous solvent can be used. As the lithium salt, for example, 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 And lithium salts such as NLi, (CF ₃ SO ₂ ) ₂ NLi, and (C ₂ F ₅ SO ₂ ) NLi. In particular, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li, which are easily soluble in a solvent and exhibit high dissociation, are preferably used. These may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The amount of the supporting electrolyte is usually 1% by weight or more, preferably 5% by weight or more, and usually 30% by weight or less, preferably 20% by weight or less, relative to the electrolyte solution. By storing the amount of the supporting electrolyte in this range, the ion conductivity can be increased, and the charging and discharging characteristics of the lithium ion secondary battery can be improved.

As the solvent used for the electrolytic solution, one capable of dissolving the supporting electrolyte can be used. Examples of the solvent include alkyl carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), 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; sulfur compounds such as sulfolane and dimethyl sulfoxide are used. In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferred because of their high ionic conductivity and easy use. One type of solvent may be used alone, or two or more types may be used in combination at any ratio.

Moreover, an additive can be contained in electrolyte solution as needed. As an additive, carbonate type compounds, such as vinylene carbonate (VC), are preferable. As the additive, one type may be used alone, or two or more types may be used in combination at any ratio.

Further, examples of the electrolytes other than the above include, for example, gel polymer electrolytes impregnated with polymer electrolytes such as polyethylene oxide and polyacrylonitrile; inorganic solid electrolytes such as lithium sulfide, LiI and Li ₃ N; .

As a method for producing a lithium ion secondary battery, for example, an electrode, a porous membrane separator, and a laminate for a lithium ion secondary battery are appropriately combined and overlapped as necessary, depending on the shape of the battery, wound or folded to form a battery container. A method of putting it in and sealing it by injecting an electrolytic solution into the battery container is mentioned. In addition, if necessary, an overcurrent preventing element such as a fuse or a PTC element, a lead plate, or an expanded metal may be added to prevent overcharging and discharging and to prevent the pressure inside the battery from rising. The shape of the battery may be, for example, a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, or a flat shape.

Example

Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited to the following examples, and can be carried out by arbitrarily changing within the scope not departing from the scope of the claims of the present invention and its equivalents.

In the following description, "%" and "part" indicating amounts are on a weight basis unless otherwise specified. In addition, the operation demonstrated below was performed on the conditions of normal temperature and normal pressure, unless otherwise specified.

[Assessment Methods]

[Redissolution rate of water-soluble polymer compound film in water]

In Examples 1 to 4, 6 to 9, 11 and 12, and Comparative Examples 1 to 3, aqueous solutions containing carboxymethyl cellulose ammonium salt and ammonia were prepared. As this aqueous solution, one containing carboxymethyl cellulose ammonium salt and ammonia in the same proportion as the slurry composition for a porous membrane according to each Example and Comparative Example is used.

In Examples 5 and 10, aqueous solutions containing the water-soluble polymer compound and the low-molecular compound X used in each example in the same proportion as the slurry composition for a porous membrane according to each example are prepared.

On the copper foil having a thickness of 20 µm, the prepared aqueous solution was applied to a thickness of 2 µm after drying, and dried at 120 ° C. for 10 minutes to form a film of a water-soluble polymer compound. Thereby, the copper foil which has a film of water-soluble high molecular compound on the surface is obtained. This copper foil is cut into 1x1 cm2 and used as a test piece. The weight M1 of this test piece is measured.

Moreover, the copper foil which does not form the film of a water-soluble polymer compound is cut out to the same size as the said test piece, and the weight M0 is measured.

Moreover, the said test piece is immersed in 25 degreeC ion-exchange water for 1 hour. Thereafter, the test piece was taken out from the ion-exchanged water and dried at 120 ° C for 10 minutes. After drying, the weight M2 of the test piece is measured.

From the measured weights M0, M1 and M2, the re-dissolution rate ΔM is calculated by the following formula. It shows that the shape retention property is excellent, so that re-dissolution rate (DELTA) M is small.

ΔM = (M1-M2) / (M1-M0) × 100 (%)

A: Re-dissolution rate ΔM is less than 5%.

B: The re-dissolution rate ΔM is 5% or more and less than 10%.

C: Remelting rate ΔM is 10% or more and less than 15%

D: Re-dissolution rate ΔM is 15% or more

〔Heat shrinking property〕

The porous membrane separator is cut into a square having a width of 5 cm and a length of 5 cm to obtain a test piece. The test piece was placed in a constant temperature bath at 150 ° C and left for 1 hour, and then the square area change was determined as the heat shrinkage. It shows that the thermal contraction property of a porous membrane separator is excellent, so that a thermal contraction rate is small.

A: The heat shrinkage rate is less than 1%.

B: The heat shrinkage ratio is 1% or more and less than 5%.

C: The heat shrinkage rate is 5% or more and less than 10%.

D: The heat shrinkage rate is 10% or more.

(Adhesiveness of the adhesive layer in the electrolytic solution)

The porous membrane separator was cut to a width of 5 cm x a length of 5 cm, and overlapped with a negative electrode (4 cm in width × 4 cm in length) having an electrode active material layer thereon, and pressed under conditions of 90 ° C, 0.5 MPa, and 10 seconds. Then, a laminate having a porous membrane separator and a negative electrode having an electrode active material layer was prepared. The prepared laminate was cut to a width of 10 mm to obtain a sample. This sample was immersed in the same electrolytic solution used for the production of the battery at a temperature of 60 ° C for 3 days. Thereafter, the sample is taken out of the electrolytic solution, and the porous membrane separator is peeled from the negative electrode in a moist state. The adhesiveness at this time is evaluated based on the following criteria. It shows that the retention property of the adhesive force of the adhesive layer in electrolyte solution is so high that the resistance when peeling a porous membrane separator from the electrode active material of a negative electrode is large.

In addition, in the same manner as the laminate having the porous membrane separator and the negative electrode described above, a laminate having the positive electrode having the porous membrane separator and the electrode active material layer is prepared. About this laminated body, adhesiveness is evaluated similarly to the laminated body provided with a porous membrane separator and a negative electrode. Here, when the results of the evaluation of the adhesion between the porous membrane separator and the positive electrode are the same as those of the evaluation of the adhesion between the porous membrane separator and the negative electrode, only the results of the evaluation of the adhesion between the porous membrane separator and the negative electrode are described.

A: When peeled, there is resistance (excellent adhesiveness).

B: When peeled, there is little resistance (adhesiveness is inferior).

C: It has already peeled off when taken out from the electrolytic solution.

〔Blocking resistance〕

The porous membrane separator was cut into squares each of 5 cm wide x 5 cm long and 4 cm wide x 4 cm long to prepare a test piece. These two test pieces are superimposed. The superimposed but unpressurized samples (samples not pressed) and the samples (pressed samples) placed under pressure at a temperature of 40 ° C. and a pressure of 10 g / c m 2 after being superimposed are left for 24 hours, respectively. After leaving for 24 hours, the sample was visually observed to confirm the adhesion state (blocking state) of the superposed porous membrane separator, and evaluated according to the following criteria.

Here, blocking refers to a phenomenon in which overlapping porous membrane separators adhere.

A: The pressurized porous membrane separators do not block.

B: The pressurized porous membrane separators are blocked, but peeled off.

C: The pressurized secondary battery separators are blocked and do not peel off.

D: The porous membrane separators that are not pressurized are blocking.

[Method for Measuring Residual Concentration of Low-Molecular Compound X]

Quantification of at least one low-molecular compound X selected from the group consisting of ammonia and amine compounds contained in the porous membrane was performed by a purge & trap / gas chromatography (P & T / GC) method shown below.

0.1 g of a porous membrane separator comprising a separator substrate, a porous membrane, and an adhesive layer is placed in a purge container. The temperature in the purge vessel is heated at a rate of 10 ° C / minute while flowing helium gas as a carrier gas at 50 ml / minute into the purge vessel. The temperature in the purge container, which was room temperature before heating, rises after heating starts. When the temperature reaches 150 ° C, the temperature of 150 ° C is maintained for 30 minutes. Thereafter, the mixture is heated to 200 ° C at a rate of 10 ° C / min, and the generated volatile components are collected in a trap tube. After collection, the temperature of the purge container is returned to room temperature.

Subsequently, the trap tube in which the volatile components are collected is heated from 130 ° C to 280 ° C at a rate of 50 ° C / min, and gas chromatography is used to quantify the volatile components under the following conditions. The component which volatilizes when heated to a temperature of 150 ° C or more and 200 ° C or less is considered to be the low molecular compound X, so that the residual concentration of the low molecular compound X can be measured by quantifying the volatile component.

The conditions of gas chromatography are as follows.

Measuring device ： Gas chromatograph 9890 manufactured by Agilent (FID method)

Data processing equipment ： C-R7A chromatograph manufactured by Shimadzu

Fuzzy & Trap Sunpla ： TDS manufactured by Agilent

Column: DB-5 manufactured by J & W (L = 30 m, I.D = 0.32 mm, Film = 0.25 μm)

Column temperature: 50 ° C (2 minutes maintenance) to 270 ° C (10 ° C / minute heating)

Sample feeding temperature: 280 ℃

Detection temperature: 280 ℃

Carrier gas ： Helium gas

Flow rate: 1 ml / min

[Example 1]

(1.1. Preparation of meta (acrylic) polymer)

To a reactor equipped with a stirrer, 0.06 parts of sodium dodecyl sulfate, 0.23 parts of ammonium persulfate, and 100 parts of ion-exchanged water were added and mixed to obtain a mixture A1. This mixture A1 was heated to 80 ° C.

On the other hand, among other containers, 83.8 parts of butyl acrylate, 2.0 parts of methacrylic acid, 12.0 parts of acrylonitrile, 1.0 parts of allyl glycidyl ether, 1.2 parts of N-methylolacrylamide, 0.1 parts of sodium dodecyl sulfate, and ion-exchanged water 100 parts were mixed to prepare a dispersion of monomer mixture B1.

The dispersion of this monomer mixture B1 was polymerized by continuously adding it to the mixture A1 described above over 4 hours. During the continuous addition of the dispersion of the monomer mixture B1, the temperature of the reaction system was maintained at 80 ° C, and reaction was performed. After the completion of the continuous addition, the reaction was continued at 90 ° C for 3 hours again. Thereby, an aqueous dispersion containing a binder composed of a (meth) acrylic polymer was obtained.

After the obtained aqueous dispersion containing the binder was cooled to 25 ° C, ammonia water was added thereto to adjust the pH to 7. Thereafter, steam was introduced to remove unreacted monomer. Immediately thereafter, while additionally adjusting the solid content concentration with ion-exchanged water, filtration was performed with a stainless steel mesh of 200 mesh (approximately 77 µm in size) to obtain a binder having an average particle diameter of 370 nm and a solid content concentration of 40%. An aqueous dispersion was obtained.

(1.2. Preparation of slurry composition for porous membrane)

As non-conductive particles, alumina particles ("AKP-3000" manufactured by Sumitomo Chemical, volume average particle diameter D50 = 0.45 µm, particles on tetrapod (registered trademark)) were prepared.

As the viscosity modifier, carboxymethyl cellulose ammonium salt ("DN10L" manufactured by Daicel Finechem) was used. This carboxymethyl cellulose ammonium salt was prepared in the form of an aqueous solution containing carboxymethyl cellulose ammonium salt and ammonia. Moreover, the viscosity of the 1% aqueous solution of this viscosity modifier was 10 mPa · s or more and 50 mPa · s or less.

100 parts of non-conductive particles, the aqueous solution of the carboxymethyl cellulose ammonium salt as a viscosity modifier was mixed with 1.5 parts of the total amount of carboxymethyl cellulose ammonium salt and ammonia, and ion-exchanged water was mixed to a solid content concentration of 40% by weight and stirred. Moreover, 4 parts of the aqueous dispersion liquid containing the (meth) acrylic polymer obtained by the said process (1.1) as a binder was mixed as solid content. Further, 0.2 parts of a polyethylene glycol type surfactant ("SN Wet 366" manufactured by Sanno Fuco) was mixed to prepare a slurry composition for a porous membrane.

Here, the carboxymethyl cellulose ammonium salt used as a viscosity modifier is a neutral salt of carboxymethyl cellulose and ammonia. The slurry composition for porous membranes prepared using this carboxymethylcelluloseammonium salt contains 1.4 parts of carboxymethylcelluloseammonium salt, which is a water-soluble polymer compound, and 100 parts of carboxymethylcelluloseammonium salt, which is a water-soluble polymer compound, per 100 parts of non-conductive particles. About 5 parts of ammonia which is a low molecular compound X.

Using this carboxymethylcellulose ammonium salt, the re-dissolution rate of the water-soluble polymer compound film in water was measured by the above-described method.

(1.3. Preparation of particulate polymer)

In a 5 MPa pressure resistant container with a stirrer, 22.2 parts of butyl acrylate as a (meth) acrylic acid ester monomer, 2 parts of methacrylic acid as an ethylenically unsaturated carboxylic acid monomer, 75 parts of styrene as an aromatic vinyl monomer, and ethylene di as a crosslinkable monomer. 0.8 part of methacrylate, 1 part of sodium dodecylbenzenesulfonate as an emulsifier, 150 parts of ion-exchanged water, and 0.5 part of potassium persulfate as a polymerization initiator were added and stirred sufficiently. Then, it heated to 60 degreeC and polymerization was started. When the polymerization conversion ratio reached 96%, the reaction was stopped by cooling to obtain an aqueous dispersion containing a particulate polymer. The obtained particulate polymer had a volume average particle diameter D50 of 0.15 µm and a glass transition temperature of 76 ° C.

(1.4. Preparation of slurry composition for adhesive layer)

The aqueous dispersion of the particulate polymer obtained in the step (1.3) was mixed with 100 parts as a solid content, and the (meth) acrylic polymer obtained in the step (1.1) as a binder with a solid content was mixed 4 parts. Further, ion-exchanged water was mixed to obtain a slurry composition for an adhesive layer with a solid content concentration of 20%.

(1.5. Preparation of porous membrane separator)

A separator substrate (16 µm thick) made of a polyethylene-made porous substrate was prepared. The slurry composition for a porous membrane was applied to both surfaces of the prepared separator substrate, and dried at 50 ° C for 3 minutes. Thus, a porous film having a thickness of 3 µm per layer was formed on the separator substrate.

Subsequently, the slurry composition for an adhesive layer was applied onto each porous film, and dried at 50 ° C. for 1 minute to form an adhesive layer having a thickness of 0.5 μm per layer. Thus, a porous membrane separator comprising an adhesive layer, a porous membrane, a separator substrate, a porous membrane, and an adhesive layer in this order was obtained. About the obtained porous membrane separator, heat shrinkability, the adhesiveness of the adhesive layer in electrolyte solution, and blocking resistance were evaluated.

(1.6. Preparation of positive electrode)

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

(1.7. Preparation of negative electrode)

As a negative electrode active material, 98 parts of graphite having a particle size of 20 µm and a BET specific surface area of 4.2 m 2 / g, and 1 part of the solid content equivalent of SBR (styrene-butadiene rubber, glass transition temperature: -10 ° C) as a binder were mixed and added to this mixture. 1 part of carboxymethylcellulose was mixed, water was added as a solvent, and these were mixed with a planetary mixer to obtain a slurry composition for an active material layer for a negative electrode. The slurry composition for an active material layer for a negative electrode was applied to one side of a copper foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll-pressed to obtain a negative electrode having an electrode active material layer having a total thickness of 60 μm.

(1.8. Preparation of a laminate for secondary batteries)

The positive electrode, the porous membrane separator, and the negative electrode were overlapped. At this time, the positive electrode active material layer of the positive electrode contacted one of the adhesive layers of the porous membrane separator, and the negative electrode active material layer of the negative electrode and the other adhesive layer of the porous membrane separator were brought into contact. Then, it press-pressed at 80 degreeC and pressure 0.5 MPa for 10 second, and pressure-bonded the positive electrode, a porous membrane separator, and a negative electrode. Thus, a laminate for a secondary battery comprising a positive electrode, a porous membrane separator, and a negative electrode was obtained.

(1.9. Preparation of lithium ion secondary battery)

On the inner bottom surface of a stainless steel coin-shaped outer container formed with a polypropylene packing, the above-described secondary battery laminate having a layer structure of a negative electrode / secondary battery separator / positive electrode was provided, and these were stored in a container. The electrolyte is injected into the container so that no air remains, and a 0.2 mm thick stainless steel cap is fixed to the exterior container via a polypropylene packing, the battery can is sealed, and a full cell type having a diameter of 20 mm and a thickness of about 3.2 mm is sealed. A lithium ion secondary battery (Coin Cell CR2032) was prepared. As an electrolytic solution, a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / liter in a mixed solvent obtained by mixing ethylene carbonate (EC) and diethyl carbonate (DEC) at EC: DEC = 1: 2 (volume ratio at 20 ° C) Used.

[Example 2]

In the step (1.2), as the non-conductive particles, instead of alumina particles, boehmite particles ("APYRAL AOH 60" manufactured by Nabaltec, volume average particle diameter D50 = 0.9 µm, plate-like particles) were used. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 3]

In the step (1.2), magnesium oxide particles ("PUREMAG FNM-G" manufactured by Tateho Chemical Co., Ltd., volume average particle diameter D50 = 0.5 µm, ellipsoidal spherical particles and rounded polyhedrons as non-conductive particles) Mixture of shaped particles). A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 4]

(Preparation of polymer particles)

To a reactor equipped with a stirrer, 0.06 parts of sodium dodecyl sulfate, 0.23 parts of ammonium persulfate, and 100 parts of ion-exchanged water were added and mixed to obtain a mixture A4. This mixture A4 was heated to 80 ° C.

On the other hand, among other containers, 93.8 parts of butyl acrylate, 2.0 parts of methacrylic acid, 2.0 parts of acrylonitrile, 1.0 parts of allyl glycidyl ether, 1.2 parts of N-methylolacrylamide, 0.1 parts of sodium dodecyl sulfate, and ion-exchanged water 100 parts were mixed to prepare a dispersion of monomer mixture B4.

The dispersion of this monomer mixture B4 was polymerized by continuously adding it to the mixture A4 described above over 4 hours. During the continuous addition of the dispersion of the monomer mixture B4, the temperature of the reaction system was maintained at 80 ° C, and reaction was performed. After the completion of the continuous addition, the reaction was continued at 90 ° C for 3 hours again. Thus, an aqueous dispersion of seed polymer particles C4 having an average particle diameter of 370 nm was obtained.

Next, in a reactor equipped with a stirrer, the water dispersion of the seed polymer particles C4 is 20 parts by solid content (i.e., the weight of the seed polymer particles C4), and ethylene glycol dimethacrylate as a monomer (Kyoisha Chemicals) 100 parts of "Light Ester EG", 1.0 parts of sodium dodecylbenzenesulfonate, 4.0 parts of t-butylperoxy-2-ethylhexanoate ("Perbutyl O" manufactured by Nichiyu Corporation) as a polymerization initiator, and By adding 200 parts of ion-exchanged water and stirring at 35 ° C. for 12 hours, the monomer and polymerization initiator were completely absorbed into the seed polymer particles C4. Subsequently, it was polymerized at 90 ° C for 5 hours. Thereafter, steam was introduced to remove unreacted monomer and initiator decomposition products. Thus, an aqueous dispersion containing polymer particles as non-conductive particles having a volume average particle diameter D50 of 670 nm was obtained.

In the step (1.2), the polymer particles described above were used instead of alumina particles as non-conductive particles. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 5]

(5.1. Preparation of maleimide-maleic acid copolymer)

In a reactor equipped with a stirrer, 100 parts of isobutylene-maleic anhydride copolymer ("isoban-04" manufactured by Kurare Co., Ltd.) was added. Ammonia gas was blown into the reactor, and the reaction was carried out for about 1 hour until exotherm stopped while cooling with a water bath. Subsequently, ammonia gas was pressurized while heating with an oil bath, and the resulting water was heated to 200 ° C while distilling off the system to carry out an imidization reaction. After completion of the reaction, the reaction product was taken out and dried by heating to obtain a maleimide-maleic acid copolymer. The composition of the obtained maleimide-maleic acid copolymer was 50 mol% of isobutylene units, 18 mol% of maleic anhydride units, 12 mol% of maleic acid units, and 20 mol% of maleimide units.

In addition, 100 parts of the resulting maleimide-maleic acid copolymer was added to 540 parts of ammonia water having a concentration of 25% in a reactor equipped with a stirrer, and stirred at 90 ° C for 5 hours, so that maleimide-maleic acid having a solid content concentration of 20% was airborne. An aqueous solution of the coalescence was obtained. The maleimide-maleic acid copolymer had a weight average molecular weight of 60000.

In the step (1.2), the polymer particles prepared in Example 4 were used instead of alumina particles as the non-conductive particles.

In the step (1.2), 100 parts of the maleimide-maleic acid copolymer obtained in the step (5.1) was used instead of the aqueous solution of the carboxymethylcelluloseammonium salt. At this time, the maleimide-maleic acid copolymer was added in the form of an aqueous solution. The obtained slurry for porous membrane contains 15 parts of ammonia with respect to 100 parts of maleimide-maleic acid copolymer which is a water-soluble polymer compound.

A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 6]

In the step (1.3), the amount of butyl acrylate was changed to 52.2 parts, the amount of styrene was changed to 45 parts, and the glass transition temperature of the particulate polymer of the adhesive layer was adjusted to 15 ° C. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 7]

In the step (1.3), the amount of butyl acrylate was changed to 27.2 parts, the amount of styrene was changed to 70 parts, and the glass transition temperature of the particulate polymer of the adhesive layer was adjusted to 35 ° C. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 8]

In the step (1.3), the amount of butyl acrylate was changed to 7.2 parts, the amount of styrene was changed to 90 parts, and the glass transition temperature of the particulate polymer of the adhesive layer was adjusted to 93 ° C. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 9]

In the step (1.2), the amount of the aqueous solution of the carboxymethylcelluloseammonium salt was changed to 7 parts by the total amount of the carboxymethylcelluloseammonium salt and ammonia. The aqueous solution of this carboxymethylcellulose ammonium salt contains 6.6 parts of carboxymethylcelluloseammonium salt and 0.4 parts of ammonia. Thereby, in the slurry composition for a porous membrane, the amount of ammonia with respect to 100 parts of carboxymethyl cellulose ammonium salt which is a water-soluble polymer compound was added to 5 parts.

A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 10]

An aqueous solution containing carboxymethylcellulose and 2-aminoethanol was prepared. In this aqueous solution, the amount of 2-aminoethanol relative to 100 parts of carboxymethylcellulose was 18 parts. In addition, in this aqueous solution, carboxymethylcellulose and 2-aminoethanol react to form neutralizing salts of carboxymethylcellulose and 2-aminoethanol, which are water-soluble polymer compounds, and some unreacted 2-aminoethanol remains. The aqueous solution thus prepared was used in the step (1.2) in place of the aqueous solution of carboxymethylcelluloseammonium salt. The amount of the aqueous solution at this time was set to an amount containing 1.5 parts of a neutralizing salt of carboxymethylcellulose and 2-aminoethanol and 0.1 part of 2-aminoethanol.

A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 11]

In the step (1.2), by adding an aqueous ammonia solution to the porous membrane slurry composition, the amount of ammonia as the low molecular compound X relative to 100 parts of the carboxymethylcellulose ammonium salt as a water-soluble polymer compound was set to 10 parts.

A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Example 12]

In the step (1.2), by adding an aqueous ammonia solution to the porous membrane slurry composition, the amount of ammonia as the low molecular compound X relative to 100 parts of the carboxymethylcellulose ammonium salt as a water-soluble polymer compound was set to 20 parts.

A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Comparative Example 1]

In the above step (1.5), no adhesive layer was formed. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Comparative Example 2]

In the step (1.3), the amount of butyl acrylate was changed to 4.2 parts, the amount of methacrylic acid was changed to 10 parts, the amount of styrene was changed to 85 parts, and the glass transition temperature of the particulate polymer of the adhesive layer was set to 112 ° C. Adjusted. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Comparative Example 3]

In the above step (1.3), 87.8 parts of ethyl acrylate was used instead of butyl acrylate, the amount of methacrylic acid was changed to 2 parts, and 10 parts of acrylonitrile was used in place of styrene, and the amount of ethylene dimethacrylate was 0.2. It was changed to negative, and the glass transition temperature of the particulate polymer of the adhesive layer was adjusted to 5 ° C. A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Comparative Example 4]

In the step (1.2), an aqueous solution of carboxymethylcelluloseammonium salt was not used.

Moreover, in the said process (1.5), the thickness per layer of the adhesive layer was changed to 10 micrometers.

A porous membrane separator, a laminate for a secondary battery, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except for the above.

[Evaluation results]

The structures of Examples and Comparative Examples are shown in Tables 1 to 4, and the results are shown in Tables 5 to 7. Here, the meaning of the abbreviation in the following table is as follows.

The amount of 100 parts by weight of the water-soluble polymer in the "low molecular compound" column: The amount of the low-molecular compound X in 100 parts by weight of the water-soluble polymer compound in the porous slurry composition

Binder composition: Weight ratio of (meth) acrylonitrile monomer unit / (meth) acrylic acid ester monomer unit in binder

Residual amount of low molecular compound: Residual amount of low molecular compound X in the porous membrane

Monomer I: acrylic ester monomer

Monomer II: ethylenically unsaturated carboxylic monomer

Monomer III: aromatic vinyl monomer

Monomer IV: (meth) acrylonitrile monomer

Monomer V: crosslinker monomer

CMC1: Carboxymethylcellulose ammonium salt

CMC2: neutral salt of carboxymethylcellulose and 2-aminoethanol

ACL ： Acrylic rubber

BA ： Butyl acrylate

EA: ethyl acrylate

MAA ： Methacrylic acid

ST ： Styrene

EDMA: Ethylene dimethacrylate

Isoban ： Maleimide-maleic acid copolymer

[Review]

As can be seen from the table, according to the present invention, by using the slurry composition containing water, the porous film is not easily dissolved in the slurry composition for the adhesive layer, and also excellent in both adhesion to the electrode and blocking resistance. A porous membrane separator can be produced.

Claims (7)

A slurry composition for a porous membrane containing at least one kind of low-molecular-weight compound selected from the group consisting of non-conductive particles, water-soluble polymer compounds, water, and ammonia and amine compounds is applied to at least one side of the separator substrate and dried to form a porous membrane. The process of obtaining, and
A step of applying a slurry composition for an adhesive layer containing a particulate polymer having a glass transition temperature of 10 ° C or more and 110 ° C or less on the porous film, and drying it to obtain an adhesive layer. Manufacturing method. According to claim 1,
A method for producing a porous membrane separator, wherein the water-soluble polymer compound has an acidic group. According to claim 2,
A method for producing a porous membrane separator, wherein the acidic group is a carboxyl group. According to claim 1,
The method for producing a porous membrane separator, wherein the concentration of the low-molecular compound in the porous membrane is 1000 ppm or less per unit weight of the porous membrane. According to claim 1,
A method for producing a porous membrane separator, wherein the low molecular compound is ammonia. According to claim 1,
The method for producing a porous membrane separator, wherein the water-soluble polymer compound is at least one member selected from the group consisting of carboxymethyl cellulose and a maleimide-maleic acid copolymer containing a structural unit represented by the following formula (I).
[Formula 1]

(In formula (I), R ¹ is a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, a phenyl group, a phenyl group substituted with an alkyl group having 1 to 6 carbon atoms, an alkyloxy group having 1 to 6 carbon atoms) It is at least one member selected from the group consisting of a substituted phenyl group, a phenyl group substituted with a halogen atom, and a hydroxyphenyl group.) A method for producing a laminate for a lithium ion secondary battery, comprising pressure-bonding an electrode and a porous membrane separator produced by the production method according to any one of claims 1 to 6.