KR102047339B1 - Porous membrane composition for lithium ion secondary battery, separator for lithium ion secondary battery, electrode for lithium ion secondary battery, lithium ion secondary battery, method for producing separator for lithium ion secondary battery, and method for producing electrode for lithium ion secondary battery - Google Patents

Abstract

As said porous film composition for lithium ion secondary batteries containing a nonelectroconductive particle, the water-soluble thickener (A) containing a hydroxyl group or / and a carboxyl group, a carbodiimide compound crosslinking agent (B), and a particulate-form polymer (C), it is a said particulate form. Polymer (C) has a functional group which reacts with the said carbodiimide compound crosslinking agent (B).

Description

A method for producing a porous membrane composition for a lithium ion secondary battery, a separator for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, a method for manufacturing a separator for a lithium ion secondary battery, a lithium ion secondary battery, and a method for manufacturing an electrode for a lithium ion secondary battery {POROUS MEMBRANE COMPOSITION FOR LITHIUM ION SECONDARY BATTERY, SEPARATOR FOR LITHIUM ION SECONDARY BATTERY, ELECTRODE FOR LITHIUM ION SECONDARY BATTERY, LITHIUM ION SECONDARY BATTERY, METHOD FOR PRODUCING SEPARATOR FOR LITHIUM

The present invention provides a method for producing a porous membrane composition for a lithium ion secondary battery, a separator for a lithium ion secondary battery, an electrode for a lithium ion secondary battery, a lithium ion secondary battery, a separator for a lithium ion secondary battery, and the production of an electrode for a lithium ion secondary battery. It is about a method.

Secondary batteries, such as lithium ion secondary batteries, which are compact, lightweight, and have high energy density and are capable of repeatedly charging and discharging, are expected to expand their demand in the future. Lithium ion secondary batteries have a high energy density and are used in fields such as mobile phones and notebook personal computers. In addition, with the expansion of power generation and the development of secondary batteries, secondary batteries are further improved, such as low resistance, large capacity, long life (improved cycle characteristics), and improved retention rate (rate characteristics) of charge and discharge capacity at high rates. Performance improvements are required.

The composition for secondary batteries containing an aqueous binder is used as a binder at the time of forming components, such as an electrode and a separator, of a lithium ion secondary battery for the purpose of the improvement of cycling characteristics. The aqueous binder does not cover the entirety of the surface of the active material and is suitably covered, and does not inhibit the insertion / desorption reaction of lithium ions. Therefore, in a lithium ion secondary battery, internal resistance of a battery reduces and cycling characteristics improve.

For example, Patent Literature 1 describes that an aqueous negative electrode binder having a large amount of acid is used when an alloy is used for a negative electrode active material. In Patent Literature 2, a fluorine-based binder is used in order to increase adhesion to the current collector. The use of is described.

Here, as a separator used for a lithium ion secondary battery normally, the microporous film which consists of polyolefin resin is used, for example. When the temperature inside the battery reaches around 130 ° C., the separator is melted to block the micropores, thereby preventing the movement of lithium ions and shutting down the current, thereby maintaining safety of the lithium ion secondary battery. It plays a role. However, when a battery temperature exceeds 150 degreeC by instantaneous heat_generation | fever, for example, a separator may shrink rapidly, the point where a positive electrode and a negative electrode contact directly and a short circuit may expand. In this case, battery temperature may reach the state overheated to several hundred degreeC or more.

For this reason, the non-aqueous separator etc. which laminated | stacked the porous film layer with heat resistance on the surface of separators, such as a polyethylene microporous film, are examined. The porous membrane layer is a membrane having a plurality of connected microporous structures therein and contains a binder for binding the non-conductive particles, the non-conductive particles, the non-conductive particles, the separator or the current collector. The porous membrane layer may be laminated on the electrode or used as the separator itself.

International Publication No. 2011/037142 Japanese Unexamined Patent Publication No. 2010-146870

Here, from the viewpoint of further improving the performance of the lithium ion secondary battery, suppressing the gas generation in the lithium ion secondary battery, suppressing the expansion of the cell, and the separator or electrode in which the porous membrane layer is laminated It is required to improve the adhesive strength of the sclera layer.

An object of the present invention is to provide a porous membrane composition for a lithium ion secondary battery capable of obtaining a porous membrane layer having a low moisture content and excellent adhesion strength, a separator for a lithium ion secondary battery obtained by using the porous membrane composition for a lithium ion secondary battery, Providing a lithium ion secondary battery electrode and a lithium ion secondary battery, and furthermore, a method for producing a separator for a lithium ion secondary battery using the porous membrane composition for a lithium ion secondary battery and a method for producing an electrode for a lithium ion secondary battery. To provide.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining, it discovered that the said objective can be achieved by using the composition containing a specific water-soluble thickener and a carbodiimide compound in addition to a binder, and came to complete this invention.

In other words, according to the present invention,

(1) A porous membrane composition for lithium ion secondary batteries containing non-conductive particles, a water-soluble thickener (A) containing a hydroxyl group or / and a carboxyl group, a carbodiimide compound crosslinking agent (B), and a particulate polymer (C). , The particulate polymer (C) is a porous membrane composition for lithium ion secondary batteries having a functional group reacting with the carbodiimide compound crosslinking agent (B),

(2) The above water-soluble thickener (A) is at least one member selected from the group consisting of carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, polyvinyl alcohol, polyacrylic acid or salts thereof (1) The porous membrane composition for lithium ion secondary batteries of description,

(3) The functional group reacting with the carbodiimide compound crosslinking agent (B) in the particulate polymer (C) is (1) or (1) selected from the group consisting of a carboxyl group, a hydroxyl group, a glycidyl ether group, and a thiol group The porous film composition for lithium ion secondary batteries of 2),

(4) 0.2-15 weight part of said water-soluble thickeners (A), 0.01-10 weight part of said carbodiimide compound crosslinking agents (B), and said particulate-form polymer (C) with respect to 100 weight part of said nonelectroconductive particles. The porous film composition for lithium ion secondary batteries in any one of (1)-(3) containing -15 weight part each,

(5) The separator for lithium ion secondary batteries obtained by apply | coating the porous film composition for lithium ion secondary batteries in any one of (1)-(4) on a board | substrate, and drying it,

(6) The electrode for lithium ion secondary batteries obtained by apply | coating the porous film composition for lithium ion secondary batteries in any one of (1)-(4) on a pole plate, and drying it,

(7) A lithium ion secondary battery comprising a positive electrode, a negative electrode, an electrolyte solution, and a separator, wherein the separator is a lithium ion secondary battery separator according to (5),

(8) A lithium ion secondary battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator, wherein the positive electrode and / or the negative electrode is an electrode for a lithium ion secondary battery according to (6),

(9) A method for producing a separator for a lithium ion secondary battery obtained by applying the porous membrane composition for a lithium ion secondary battery according to any one of (1) to (4) onto a substrate and drying it. The manufacturing method of the separator for lithium ion secondary batteries which has a process of apply | coating the porous film composition for batteries on a board | substrate, and the process of drying at 50-200 degreeC,

(10) A method for producing an electrode for a lithium ion secondary battery obtained by applying the porous membrane composition for a lithium ion secondary battery according to any one of (1) to (4) onto a pole plate and drying the composition. The manufacturing method of the electrode for lithium ion secondary batteries which has a process of apply | coating a porous film composition for batteries on a pole plate, and the process of drying at 50-200 degreeC is provided.

According to the porous membrane composition for lithium ion secondary batteries which concerns on this invention, the porous film layer which is low in moisture content and excellent in adhesive strength can be obtained. Moreover, according to this invention, the lithium ion secondary battery separator using the porous membrane composition for lithium ion secondary batteries, the electrode for lithium ion secondary batteries, and the lithium ion secondary battery using the porous membrane composition for lithium ion secondary batteries and a lithium ion secondary battery The manufacturing method of a separator for secondary batteries, and the manufacturing method of the electrode for lithium ion secondary batteries can be provided.

Hereinafter, the porous membrane composition for lithium ion secondary batteries which concerns on embodiment of this invention is demonstrated. The porous film composition for lithium ion secondary batteries of this invention contains a nonelectroconductive particle, the water-soluble thickener (A) containing a hydroxyl group or / and a carboxyl group, a carbodiimide compound crosslinking agent (B), and a particulate-form polymer (C) As a porous film composition for lithium ion secondary batteries, the said particulate polymer (C) has a functional group which reacts with the said carbodiimide compound crosslinking agent (B).

(Non-conductive particles)

As a material which comprises the nonelectroconductive particle used for the porous film composition for lithium ion secondary batteries (henceforth a "porous membrane composition") of this invention, it exists stably under the use environment of a lithium ion secondary battery. It is also desired to be electrochemically stable. For example, various nonelectroconductive inorganic particles and organic particles can be used.

As a material of an inorganic particle, the material which is electrochemically stable and suitable for preparing a porous film composition by mixing with another material, for example, a viscosity modifier etc. which are mentioned later is preferable. From such a viewpoint, as the inorganic particles, aluminum oxide (alumina), hydrate of aluminum oxide (boehmite (AlOOH), gibbsite (Al (OH) ₃ ), bakelite, magnesium oxide, magnesium hydroxide, iron oxide, silicon oxide, Oxides such as titanium oxide (titania), calcium oxide, nitrides such as aluminum nitride, silicon nitride, silica, barium sulfate, barium fluoride, calcium fluoride, etc. Among these, oxides may be used in view of stability in the electrolyte solution and potential stability. Among them, titanium oxide, alumina, boehmite, magnesium oxide and magnesium hydroxide are preferable from the viewpoint of low water absorption and excellent heat resistance (for example, resistance to high temperature of 180 ° C or higher), and alumina, boehmite, magnesium oxide and Magnesium hydroxide is particularly preferred.

As the organic particles, particles of a polymer (polymer) are usually used. The organic particle | grains can control affinity with water by adjusting the kind and quantity of the functional group of the surface, and can control the amount of water contained in the porous film of this invention further. As an organic material of a nonelectroconductive particle, various high molecular compounds, such as polystyrene, polyethylene, a polyimide, a melamine resin, a phenol resin, etc. are mentioned, for example. The polymer compound forming the particles may be a homopolymer or a copolymer, and in the case of a copolymer, any of a block copolymer, a random copolymer, a graft copolymer, and an alternating copolymer may be used. Furthermore, at least one part may be modified or a crosslinked product. And a mixture of these may be sufficient. As a crosslinking agent in the case of a crosslinked material, epoxy groups, such as crosslinking bodies which have aromatic rings, such as divinylbenzene, and polyfunctional acrylate crosslinking bodies, such as ethylene glycol dimethacrylate, glycidyl acrylate, and glycidyl methacrylate The crosslinked body which has, etc. are mentioned.

As for the said nonelectroconductive particle, element substitution, surface treatment, solid solution, etc. may be given as needed. Moreover, a nonelectroconductive particle may contain one type of said material independently in one particle, and may contain it combining two or more types by arbitrary ratios. In addition, you may use a nonelectroconductive particle combining 2 or more types of particle | grains formed from different materials.

Since the volume average particle diameter D50 of a nonelectroconductive particle can obtain a uniform porous film even if the thickness of a porous film is thin, from a viewpoint which can raise the capacity of a lithium ion secondary battery, Preferably it is 0.1-5 micrometers, More preferably, it is 0.2 micrometer-2 micrometers or less, More preferably, it is 0.2-1 micrometer. Here, the volume average particle diameter D50 represents a particle diameter of 50% in the cumulative volume calculated on the small particle diameter side in the particle size distribution measured by the laser diffraction method.

Moreover, it is preferable that it is 0.9-200 m <2> / g specifically, from the viewpoint of BET specific surface area of these nonelectroconductive particles suppressing aggregation of particle | grains and making the fluidity | liquidity of a porous film composition suitable, 1.5-150 It is more preferable that it is m <2> / g. The BET specific surface area of nonelectroconductive particle is made to adsorb | suck nitrogen gas to nonelectroconductive particle using a specific surface area measuring apparatus (Gemini 2310: Shimadzu Corporation make), and is measured by BET measuring method.

In the present invention, examples of the shape of the non-conductive particles include spherical shape, elliptic spherical shape, polygonal shape, tetrapod (registered trademark) shape, plate shape, and flaky shape. Especially, the tetrapod (trademark) phase, plate shape, and flaky phase are preferable from a viewpoint of raising the porosity of a porous film and suppressing the fall of the ion conductivity by a porous film separator.

(Water soluble thickener (A))

The water-soluble thickener (A) used for the porous film composition for lithium ion secondary batteries of this invention contains a hydroxyl group and / or a carboxyl group. When water-soluble thickener (A) used for this invention melt | dissolves 0.5 g of thickeners in 100 g of water at 25 degreeC, an insoluble content says the thickener of less than 1.0 weight%.

As the water-soluble thickener (A), it is preferable to use carboxymethyl cellulose, methyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, polyvinyl alcohol, polyacrylic acid or salts thereof, and carboxymethyl cellulose and polyacrylic acid are used. It is more preferable to do.

The content ratio of the water-soluble thickener (A) in the porous membrane composition of the present invention is preferably 0.2 to 15 parts by weight, more preferably 0.5 to 10 parts by weight, and even more preferably to 100 parts by weight of non-conductive particles. Is 0.5 to 8 parts by weight. When the content rate of the water-soluble thickener (A) is too large, the drying rate at the time of obtaining a porous film tends to become slow. Moreover, when the content rate of a water-soluble thickener (A) is too small, there exists a tendency for the adhesive strength of a porous film to fall.

(Carbodiimide Compound Crosslinking Agent (B))

The carbodiimide compound crosslinking agent (B) used for the porous membrane composition for lithium ion secondary batteries of this invention reacts with the functional group which the particulate-form polymer (C) mentioned later has.

The carbodiimide compound has a carbodiimide group represented by General Formula (1): -N = C = N -... (1) in the molecule, and is a water-soluble thickener (A), a water-soluble thickener (A) and a particulate polymer ( C) It will not specifically limit, if it is a crosslinkable compound which can form a crosslinked structure between liver and a particulate-form polymer (C). And as such a carbodiimide compound crosslinking agent (B), for example, the compound which has two or more carbodiimide groups, Specifically, General formula (2): -N = C = NR <^1> ... (2) ) In General Formula (2), R ¹ represents a divalent organic group. Preferred examples include polycarbodiimide and / or modified polycarbodiimide having a repeating unit. In addition, in this specification, modified polycarbodiimide means resin obtained by making the reactive compound mentioned later react with respect to polycarbodiimide.

(Synthesis of Polycarbodiimide)

Although the synthesis | combining method of polycarbodiimide is not specifically limited, For example, organic polyisocyanate exists in presence of the catalyst which accelerates the carbodiimide-ized reaction of an isocyanate group (henceforth "carbodiimide-ized catalyst"). By reacting, polycarbodiimide can be synthesized. Moreover, the polycarbodiimide which has a repeating unit represented by General formula (2) can also be synthesize | combined by copolymerizing the oligomer (carbodiimide oligomer) obtained by making organic polyisocyanate react, and the monomer copolymerizable with the said oligomer. Moreover, as organic polyisocyanate used for the synthesis | combination of this polycarbodiimide, organic diisocyanate is preferable.

As organic diisocyanate used for the synthesis | combination of polycarbodiimide, the thing of Unexamined-Japanese-Patent No. 2005-49370 is mentioned, for example. Especially, 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate are especially preferable from a viewpoint of the storage stability of the porous film composition containing polycarbodiimide as a carbodiimide compound crosslinking agent (B). Organic diisocyanate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

Moreover, together with the organic diisocyanate mentioned above, organic polyisocyanate (trifunctional or more than trifunctional organic polyisocyanate) which has three or more isocyanate groups, stoichiometric excess of trifunctional or more than trifunctional organic polyisocyanate, and bifunctional or more than polyfunctional active hydrogen containing The terminal isocyanate prepolymer obtained by reaction of a compound (Hereinafter, said trifunctional or more than trifunctional organic polyisocyanate and said terminal isocyanate prepolymer are also called "trifunctional or more than trifunctional organic polyisocyanate."). As such trifunctional or more than trifunctional organic polyisocyanate, the thing of Unexamined-Japanese-Patent No. 2005-49370 is mentioned, for example. Trifunctional or more than trifunctional organic polyisocyanate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The usage-amount of trifunctional or more than trifunctional organic polyisocyanate in the synthesis reaction of polycarbodiimide is per 100 weight part of organic diisocyanate, Preferably it is 40 weight part or less, More preferably, it is 20 weight part or less.

In addition, in the synthesis | combination of polycarbodiimide, you may add an organic monoisocyanate as needed. By adding organic monoisocyanate, when organic polyisocyanate contains trifunctional or more than trifunctional organic polyisocyanate, the molecular weight of the polycarbodiimide obtained can be appropriately regulated, and it is comparatively made by using organic diisocyanate together with organic monoisocyanate. Polycarbodiimide with a small molecular weight can be obtained. As such organic monoisocyanate, the thing of Unexamined-Japanese-Patent No. 2005-49370 is mentioned, for example. Organic monoisocyanate may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the organic monoisocyanate used in the polycarbodiimide synthesis reaction varies depending on the molecular weight required for the resulting polycarbodiimide, the presence or absence of use of trifunctional or higher organic polyisocyanates, and the like. Isocyanate and trifunctional or more than trifunctional organic polyisocyanate) component, Preferably it is 40 weight part or less, More preferably, it is 20 weight part or less.

Moreover, a phosphorene compound, a metal carbonyl complex, the metal acetylacetone complex, and a phosphate ester are mentioned as a carbodiimide-ized catalyst. Each of these specific examples is shown by Unexamined-Japanese-Patent No. 2005-49370, respectively. Carbodiimide-ized catalyst may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the carbodiimide-ized catalyst used per 100 parts by weight of the total organic isocyanate (organic monoisocyanate, organic diisocyanate, and trifunctional or higher organic polyisocyanates) components, preferably 0.001 to 30 parts by weight, more preferably 0.01 To 10 parts by weight.

Carbodiimidation reaction of organic polyisocyanate can be carried out without solvent or in a suitable solvent. The solvent in the case of carrying out the synthesis reaction in the solvent is not particularly limited as long as it can dissolve the polycarbodiimide or carbodiimide oligomer produced by heating in the synthesis reaction, and is a halogenated hydrocarbon solvent, an ether solvent, Ketone solvents, aromatic hydrocarbon solvents, amide solvents, aprotic polar solvents, and acetate solvents. Each of these specific examples is shown by Unexamined-Japanese-Patent No. 2005-49370, respectively. These solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The amount of the solvent used in the synthesis reaction of the polycarbodiimide is an amount such that the concentration of the total organic isocyanate component is preferably 0.5 to 60% by weight, more preferably 5 to 50% by weight or less. If the concentration of the total organic isocyanate component in the solvent is too high, the resulting polycarbodiimide or carbodiimide oligomer may be gelled during the synthesis reaction. Moreover, when the density | concentration of all the organic isocyanate components in a solvent is too low, reaction rate will become slow and it will become the tendency for productivity to fall.

Although the temperature of the carbodiimide-ized reaction of organic polyisocyanate is suitably selected according to the kind of organic isocyanate component and carbodiimide-ized catalyst, Preferably it is 20-200 degreeC. In the carbodiimide-ized reaction of organic polyisocyanate, the organic isocyanate component may add whole quantity before reaction or part or all of it may be added continuously or stepwise during reaction. Moreover, in this invention, the compound obtained by adding the compound which can react with an isocyanate group in the appropriate reaction step from the initial stage of the carbodiimide-ized reaction of organic polyisocyanate, and sealing the terminal isocyanate group of polycarbodiimide is obtained. The molecular weight of carbodiimide can also be adjusted. Moreover, the molecular weight of the polycarbodiimide obtained by adding in the late stage of the carbodiimide-ized reaction of organic polyisocyanate can also be regulated by predetermined value. As a compound which can react with such an isocyanate group, alcohol, such as methanol, ethanol, i-propanol, cyclohexanol; amines, such as dimethylamine, diethylamine, benzylamine, is mentioned, for example.

Moreover, as a monomer copolymerizable with a carbodiimide oligomer, the oligomer obtained by using a divalent or more alcohol, a divalent or more alcohol as a monomer, and its ester, for example, dihydric alcohols, such as ethylene glycol and propylene glycol, or poly Alkylene oxide, polyethyleneglycol monomethacrylate, polypropyleneglycol monomethacrylate, polyethyleneglycol monoacrylate and polypropyleneglycol monoacrylate are preferable.

For example, a polycarbodiimide group having a polycarbodiimide group and a polycarbodiimide having a monomer unit derived from a divalent alcohol can be synthesized by copolymerizing a dihydric alcohol having hydroxyl groups at both ends of the molecular chain with a carbodiimide oligomer. Can be. Thus, when the polycarbodiimide as a carbodiimide compound crosslinking agent (B) has a monomer unit derived from a bivalent or more alcohol, Preferably, the porous film containing this polycarbodiimide is contained. The wettability with respect to the electrolyte solution of the porous film formed from a composition can improve, and the liquid injection property of electrolyte solution in manufacture of the secondary battery provided with the negative electrode can be improved. In addition, copolymerization of the above-mentioned alcohol can increase the water solubility of the polycarbodiimide, and also cause the polycarbodiimide to self- micellize in water (the hydrophilic ethylene glycol chain is surrounded by the hydrophobic carbodiimide group). The chemical stability can be improved.

The polycarbodiimide compound crosslinking agent mentioned above is used for preparation of the porous film composition of this invention as a solution or the solid isolate | separated from the solution. As a method of separating a polycarbodiimide from a solution, for example, a polycarbodiimide solution is added to a non-solvent which is inert to the polycarbodiimide, and the resulting precipitate or oily substance is filtered or decanted. Separation and Collection Method; Separation and Collection Method by Spray Drying; Method for Separation and Collection Using Solubility Change with Temperature to Solvent Used in Synthesis of Polycarbodiimide Obtained, That is, Immediately After Synthesis In the case where the dissolved polycarbodiimide is precipitated by lowering the temperature of the system, a method of separating and extracting from the turbidity by filtration or the like may be mentioned, and these separation and extraction methods may be carried out by combining appropriately. It may be. The polystyrene reduced number average molecular weight (hereinafter referred to as "Mn") determined by gel permeation chromatography (GPC) of the polycarbodiimide in the present invention is a viewpoint of accelerating the crosslinking rate with the water-soluble thickener (A). Preferably, it is 1,000-200,000, More preferably, it is 2,000-100,000 or less.

Synthesis of Modified Polycarbodiimide

Next, the synthesis | combining method of modified polycarbodiimide is demonstrated. The modified polycarbodiimide is reacted with a polycarbodiimide having a repeating unit represented by the general formula (2) at least one of at least one of the reactive compounds at an appropriate temperature in the presence or absence of a suitable catalyst. Hereinafter, it is called "modification reaction."

The reactive compound used for the synthesis | combination of modified polycarbodiimide has the compound which has one group which has reactivity with polycarbodiimide (henceforth simply a "reactive group"), and another functional group in the molecule | numerator. Say This reactive compound may be an aromatic compound, an aliphatic compound or an alicyclic compound, and the ring structure in an aromatic compound and an alicyclic compound may be a carbon ring or a heterocyclic ring. As a reactive group in a reactive compound, what is necessary is just group which has active hydrogen, and a carboxyl group or a primary or secondary amino group is mentioned, for example. And a reactive compound has another functional group further in addition to one reactive group in the molecule | numerator. As another functional group which a reactive compound has, the group which has a function which accelerate | stimulates the crosslinking reaction of polycarbodiimide and / or modified polycarbodiimide, or the 2nd or later (that is, the above-mentioned reactive in 1 molecule of reactive compounds) And other groups having an active hydrogen as described above, and for example, a carboxyl group and a primary or secondary exemplified as a group having active hydrogen, in addition to a carboxylic anhydride group and a tertiary amino group. An amino group etc. are mentioned. As these other functional groups, two or more same or different groups may exist in 1 molecule of a reactive compound.

As a reactive compound, the thing of Unexamined-Japanese-Patent No. 2005-49370 is mentioned, for example. Especially, trimellitic anhydride and nicotinic acid are preferable. A reactive compound may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

The amount of the reactive compound used in the modification reaction for synthesizing the modified polycarbodiimide is appropriately adjusted depending on the kind of the polycarbodiimide or the reactive compound, the physical properties required for the obtained modified polycarbodiimide, and the like. Preferably the ratio of the reactive group in the reactive compound with respect to 1 mol of repeating units represented by General formula (2) is an amount which becomes 0.01 mol or more, More preferably, it is 0.02 mol or more, Preferably it is 1 mol or less, More preferably, it is Is an amount of 0.8 mol or less. When the said ratio is less than 0.01 mol, there exists a possibility that the storage stability of the porous film composition containing modified polycarbodiimide may fall.

On the other hand, when the said ratio exceeds 1 mol, there exists a possibility that the original characteristic of polycarbodiimide may be impaired.

Moreover, in a modification reaction, reaction of the reactive group in a reactive compound and the repeating unit represented by General formula (2) of polycarbodiimide advances quantitatively, and the functional group suitable for the usage-amount of this reactive compound is in a modified polycarbodiimide. Is introduced. The modification reaction can be carried out even without a solvent, but is preferably carried out in a suitable solvent. Such solvents are not particularly limited as long as they are inert to the polycarbodiimide and the reactive compound and can dissolve them, and examples thereof include ether solvents that can be used for the synthesis of the above-described polycarbodiimide, Amide solvents, ketone solvents, aromatic hydrocarbon solvents, aprotic polar solvents, and the like. These solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Moreover, when the solvent used at the time of the synthesis | combination of polycarbodiimide can be used for a modification reaction, the polycarbodiimide solution obtained by the synthesis can also be used as it is. The usage-amount of the solvent in a modification reaction is per 100 weight part of reaction raw materials, Preferably it is 10-10,000 weight part, Preferably it is 50-5,000 weight part.

Although the temperature of a modification reaction is suitably selected according to the kind of polycarbodiimide and a reactive compound, Preferably it is -10-100 degreeC or less, More preferably, it is -10-80 degreeC. Mn of the modified polycarbodiimide in the present invention is preferably 1,000 to 200,000, more preferably 2,000 to 400,000 from the viewpoint of accelerating the crosslinking rate with the water-soluble thickener (A).

Here, the chemical formula (NCN equivalent) per mol of carbodiimide group (-N = C = N-) of a carbodiimide compound becomes like this. Preferably it is 300-600, More preferably, it is 400-500. When the NCN equivalent of a carbodiimide compound is too small, the storage stability of a porous film composition will fall. Moreover, when NCN equivalent of a carbodiimide compound is too large, advancing of a crosslinking reaction will become inadequate.

In addition, NCN equivalent of a carbodiimide compound calculates the polystyrene conversion number average molecular weight of a carbodiimide compound using GPC (gel permeation chromatography), for example, and uses carbodii using IR (infrared spectroscopy). The number of carbodiimide groups per molecule of the mid compound can be quantitatively analyzed and calculated using the following formula.

NCN equivalent = (polystyrene reduced number average molecular weight of carbodiimide compound) / (number of carbodiimide groups per molecule of carbodiimide compound)

(The property of a carbodiimide compound crosslinking agent (B), etc.)

Here, the viscosity of the 1 weight% aqueous solution of the carbodiimide compound crosslinking agent (B) mentioned above is 5000 mPa * s or less from a viewpoint which can make the adhesive strength of a porous film excellent, More preferably, it is 700 mPa * s or less, Especially preferably, it is 150 mPa * s or less. In addition, the viscosity of the 1 weight% aqueous solution of a carbodiimide compound crosslinking agent (B) is a value when it measures by 25 degreeC and rotation amount 60rpm using a Brookfield viscometer.

Moreover, it is preferable that a carbodiimide compound crosslinking agent (B) is water-soluble. When the carbodiimide compound crosslinking agent (B) is water-soluble, it is possible to prevent the carbodiimide compound crosslinking agent (B) from being unevenly distributed in the aqueous porous film composition, and to form a preferable crosslinked structure in the obtained porous film. Therefore, while ensuring the adhesion strength of the porous membrane in the obtained lithium ion secondary battery, the electrical characteristics, such as initial coulomb efficiency, initial resistance, and cycle characteristics, can be improved, and further, the resistance rise after a cycle can be suppressed. . In addition, the water resistance of the porous membrane can be improved.

Here, in this specification, that a carbodiimide compound crosslinking agent (B) is "water-soluble" means that the mixture obtained by adding 1 weight part (solid content equivalent) of a crosslinking agent per 100 weight part of ion-exchange water, and stirring, temperature 20 degreeC When adjusting to at least 1 of the conditions within the range of 70 degreeC or more and the range of pH 3 or more and 12 or less (The pH adjustment uses NaOH aqueous solution and / or HCl aqueous solution), and it passed the screen of 250 mesh, It means that the weight of the solid content of the residue which remains on the screen without passing through the screen does not exceed 50 weight% with respect to the solid content of the added crosslinking agent. Moreover, even if the mixture of a carbodiimide compound crosslinking agent (B) and water is an emulsion state which isolate | separates into two phases when it stands still, if the said definition is satisfied, the carbodiimide compound crosslinking agent (B) is said to be water-soluble. In addition, from the viewpoint of advancing the formation reaction of the crosslinked structure satisfactorily and improving the adhesion strength of the porous membrane and the cycle characteristics of the obtained lithium ion secondary battery, the mixture of the carbodiimide compound crosslinking agent (B) and water is in two phases. As for the thing which is not isolate | separated (in a single phase accommodating state), ie, a carbodiimide compound crosslinking agent (B), it is more preferable that it is one-phase water-soluble.

Moreover, 80 weight% or more is preferable and 90 weight% or more is more preferable for the same reason as the reason why the crosslinking agent mentioned above is water-soluble as the water content of a carbodiimide compound crosslinking agent (B). In addition, with the "water content" of a carbodiimide compound crosslinking agent (B), 1 weight part (solid content equivalency) of 100 weight part of ion-exchange water is added, and the mixture obtained by stirring is adjusted to 25 degreeC, pH7, and is 250 mesh. When passing through the screen, the ratio with respect to the weight of the solid content of the added crosslinking agent of the weight of the solid content of the residue which remains on a screen without passing through a screen is defined by the following formula | equation.

Water content = (100-X) weight%

The content ratio of the carbodiimide compound crosslinking agent (B) in the porous membrane composition of the present invention is preferably 0.01 to 10 parts by weight, more preferably 0.01 to 5 parts by weight, based on 100 parts by weight of the nonelectroconductive particles, More preferably, it is 0.01-1 weight part. When the content rate of a carbodiimide compound crosslinking agent (B) is too big | large, the adhesive strength of a porous film will fall and the cycling characteristics of the lithium ion secondary battery obtained will fall. Moreover, when the content rate of a carbodiimide compound crosslinking agent (B) is too small, there exists a tendency for the adhesive strength of a porous film to fall.

(Particulate polymer (C))

The particulate polymer (C) used in the present invention has a functional group that reacts with the carbodiimide compound crosslinking agent (B). Moreover, it is preferable that a particulate-form polymer (C) contains the polymer unit of a (meth) acrylic acid ester monomer. In addition, in this specification, "(meth) acryl" means "acryl" and "methacryl".

As a polymerization unit of a (meth) acrylic acid ester monomer, For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, pentyl acrylate, Alkyl acrylates such as hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; methyl Methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate , Octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl And methacrylic acid alkyl esters such as methacrylate, n-tetradecyl methacrylate and stearyl methacrylate. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Moreover, as a functional group which reacts with the carbodiimide compound crosslinking agent (B) in a particulate-form polymer (C), a carboxyl group, a hydroxyl group, glycidyl ether group, and a thiol group are preferable, and it uses in combination with a carboxyl group and glycidyl ether group. It is more preferable.

As a functional group which reacts with a carbodiimide compound crosslinking agent (B), an ethylenic unsaturated carboxylic monomer is mentioned as a monomer which can be used for manufacture of the particulate-form polymer (C) which has a carboxylic acid group. Specific examples of the ethylenic unsaturated carboxylic monomers include monocarboxylic acids and dicarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid, and anhydrides thereof. Especially, acrylic acid, methacrylic acid, and itaconic acid are preferable as an ethylenic unsaturated carboxylic monomer from a viewpoint of the stability of a porous film composition. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As a functional group which reacts with a carbodiimide compound crosslinking agent (B), as a monomer which can be used for manufacture of the particulate-form polymer (C) which has a hydroxyl group, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacryl, for example. Latex, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate, Di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate, and the like. Especially, 2-hydroxyethyl acrylate is preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As an unsaturated monomer which has a glycidyl ether group which can be used for manufacture of the particulate-form polymer (C) which has a glycidyl ether group as a functional group which reacts with a carbodiimide compound crosslinking agent (B), For example, glycidyl acrylate, Glycidyl methacrylate, and the like. Especially, glycidyl methacrylate is preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As a monomer unit which has a thiol group which can be used for manufacture of the particulate-form polymer (C) which has a thiol group as a functional group which reacts with a carbodiimide compound crosslinking agent (B), for example, pentaerythritol tetrakis (3-mercapto butyrate) ), Trimethylol propane tris (3-mercapto butyrate), trimethylol ethane tris (3- mercapto butyrate) and the like. Especially, pentaerythritol tetrakis (3-mercapto butyrate) is preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Although the functional group reacting with a carbodiimide compound crosslinking agent (B) in a particulate-form polymer (C) may be introduce | transduced by using the monomer containing the functional group reacting with the carbodiimide compound crosslinking agent (B) mentioned above for superposition | polymerization, For example, after superposing | polymerizing the particulate polymer which does not have a functional group which reacts with a carbodiimide compound crosslinking agent (B), the functional group in this particulate polymer is substituted part or all by the functional group which reacts with a carbodiimide compound crosslinking agent (B). You may introduce | transduce by making it and prepare a particulate-form polymer (C). Moreover, also about the repeating unit in the particulate-form polymer (C) which has the "functional group reacting with a carbodiimide compound crosslinking agent (B)" introduced in this way, the monomer containing the functional group reacting with a "carbodiimide compound crosslinking agent (B) Unit ".

And although the content rate of the monomeric unit containing the functional group reacting with the carbodiimide compound crosslinking agent (B) in a particulate-form polymer (C) is not specifically limited, It is excellent in the mechanical stability and chemical stability of the particulate-form polymer (C) obtained. From a viewpoint, 0.5-10 weight% is preferable, 1.0-8 weight% is more preferable, 1.5-5 weight% is further more preferable.

Moreover, the particulate-form polymer (C) may contain arbitrary repeating units other than what was mentioned above, unless the effect of this invention is remarkably impaired. As a monomer corresponding to said arbitrary repeating unit, a vinyl cyanide monomer, an unsaturated carboxylic acid alkyl ester monomer, an unsaturated carboxylic amide monomer, etc. are mentioned, for example. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Although the content rate of the monomer corresponding to the arbitrary repeating units in a particulate-form polymer (C) is not specifically limited, 0.5-10 weight% is preferable in total amount, 1.0-8 weight% is more preferable, 1.5-5 weight % Is more preferable.

As a vinyl cyanide monomer, an acrylonitrile, methacrylonitrile, the (alpha)-chloro acrylonitrile, the (alpha)-ethyl acrylonitrile, etc. are mentioned, for example. Especially, acrylonitrile and methacrylonitrile are preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As the unsaturated carboxylic acid alkyl ester monomer, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl Maleate, dimethyl itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate, and the like. Especially, methyl methacrylate is preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As an unsaturated carboxylic amide monomer, acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N- dimethyl acrylamide, etc. are mentioned, for example. Especially, acrylamide and methacrylamide are preferable. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

In addition, you may manufacture a particulate-form polymer (C) using the monomer used in normal emulsion polymerization, such as ethylene, propylene, vinyl acetate, a vinyl propionate, a vinyl chloride, vinylidene chloride, for example. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Although the content rate of other monomeric units other than the monomeric unit containing the functional group reacting with an aliphatic conjugated diene monomeric unit, an aromatic vinyl monomeric unit, and a crosslinking agent (B) in a particulate-form polymer (C) is not specifically limited, It is 0.5 in total amount. -10 weight% is preferable, 1.0-8 weight% is more preferable, 1.5-5 weight% is further more preferable.

And the particulate-form polymer (C) which consists of a copolymer etc. which have an aliphatic conjugated diene monomeric unit, an aromatic vinyl monomeric unit, etc. is manufactured by superposing | polymerizing the monomer composition containing the monomer mentioned above in an aqueous solvent, for example.

Here, the content rate of each monomer in a monomer composition is made to be the same as the content rate of the repeating unit in a desired particulate polymer (C) normally.

The aqueous solvent is not particularly limited as long as the particulate polymer (C) can be dispersed in a particulate state, and the boiling point at atmospheric pressure is preferably selected from an aqueous solvent of 80 to 350 ° C, more preferably 100 to 300 ° C. .

Specifically, examples of the aqueous solvent include water; ketones such as diacetone alcohol and γ-butyrolactone; alcohols such as ethyl alcohol, isopropyl alcohol, and normal propyl alcohol; propylene glycol monomethyl ether and methyl cell; Low solver, ethyl cellosolve, ethylene glycol tertiary butyl ether, butyl cellosolve, 3-methoxy-3methyl-1-butanol, ethylene glycol monopropyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl Glycol ethers such as ether and dipropylene glycol monomethyl ether; ethers such as 1,3-dioxolane, 1,4-dioxolane and tetrahydrofuran; and the like. Among them, water is not particularly flammable, and is particularly preferable from the viewpoint of easily obtaining a dispersion of particles of the particulate polymer (C). Moreover, you may use water as a main solvent and mix and use aqueous solvents other than said water in the range which can ensure the dispersion | distribution state of the particle | grains of a particulate-form polymer (C).

A polymerization method is not specifically limited, For example, any method, such as a solution polymerization method, suspension polymerization method, block polymerization method, and emulsion polymerization method, can also be used. As a polymerization method, any method, such as ionic polymerization, radical polymerization, a living radical polymerization, can be used, for example. Moreover, since a high molecular weight body is easy to obtain, and since a polymer is obtained in the state disperse | distributed to water as it is, the process of re-dispersion is unnecessary and can be used for manufacture of the porous film composition of this invention as it is, From a viewpoint, emulsion polymerization method is especially preferable.

In addition, emulsion polymerization can be performed according to a conventional method.

And what is generally used can be used for the emulsifier, a dispersing agent, a polymerization initiator, a polymerization assistant, etc. which are used for superposition | polymerization, The usage-amount shall also be used normally. Moreover, in superposition | polymerization, seed particle | grains may be employ | adopted and seed polymerization may be performed. Moreover, polymerization conditions can also be selected arbitrarily according to the kind of polymerization method, a polymerization initiator, etc.

Here, the aqueous dispersion of the particles of the particulate polymer (C) obtained by the polymerization method described above is, for example, hydroxides of alkali metals (eg, Li, Na, K, Rb, Cs), ammonia, inorganic ammonium The pH is preferably 5 to 10, more preferably 5, using a basic aqueous solution containing a compound (e.g., NH ₄ Cl, etc.), an organic amine compound (e.g., ethanolamine, diethylamine, etc.). You may adjust so that it may become a range of -9. Especially, since pH adjustment by alkali metal hydroxide improves the adhesive strength of a porous film, it is preferable.

(The property of the particulate polymer (C))

Usually, the particulate polymer (C) is water-insoluble. Therefore, a particulate-form polymer (C) is a particulate form in the aqueous porous film composition normally, and is contained in a porous film, maintaining the particle shape.

Moreover, the number average particle diameter of a particulate-form polymer (C) becomes like this. Preferably it is 50-500 nm, More preferably, it is 70-400 nm. In addition, a number average particle diameter can be easily measured by a transmission electron microscope method, a Coulter counter, a laser diffraction scattering method, etc.

The content ratio of the particulate polymer (C) in the porous membrane composition of the present invention is preferably 1 to 15 parts by weight, more preferably 2 to 15 parts by weight, still more preferably based on 100 parts by weight of non-conductive particles. Is 2-10 weight part. When the content ratio of the particulate polymer (C) is too large, the adhesion strength of the porous membrane decreases, and the cycle characteristics of the obtained lithium ion secondary battery tend to decrease. Moreover, when the content rate of a particulate-form polymer (C) is too small, there exists a tendency for the adhesive strength of a porous film to fall.

(Porous membrane composition)

The porous membrane composition of this invention contains a nonelectroconductive particle, the water-soluble thickener (A) containing a hydroxyl group and / or a carboxyl group, a carbodiimide compound crosslinking agent (B), and a particulate-form polymer (C), These components, It is obtained by mixing a dispersion medium.

Although the mixing method is not specifically limited, For example, the method of using mixing apparatuses, such as stirring, agitation, and rotation, is mentioned. Moreover, the method using the dispersion kneading apparatuses, such as a homogenizer, a ball mill, a sand mill, a roll mill, a planetary mixer, and a planetary kneader, is mentioned.

In the porous film composition of this invention, it is preferable to use water as a dispersion medium. In addition, in this invention, you may use what mixed the hydrophilic solvent with water as a dispersion medium as long as it is a range which does not inhibit the dispersion stability of a porous film composition. Examples of the hydrophilic solvent include methanol, ethanol, N-methylpyrrolidone and the like, and are preferably 5% by weight or less with respect to water.

Moreover, it is preferable that solid content concentration of a porous film composition is 10 to 65 weight%. When solid content concentration is too high, there exists a tendency for the applicability | paintability of a porous film composition to fall. Moreover, when solid content concentration is too low, since water will become difficult to fall out from a porous film, it will become difficult to reduce moisture content.

Moreover, it is preferable that the viscosity of a porous film composition is 15-500 mPa * s. In addition, the viscosity of a porous film composition is the value measured at the temperature of 25 degreeC, and rotation speed 60rpm using a Brookfield viscometer.

(Polymer for Secondary Battery)

By apply | coating the above-mentioned porous film composition on a base material, and drying, a porous film for secondary batteries (henceforth a "porous film" may be called.) Can be obtained.

A porous film may be laminated | stacked on an organic separator and an electrode, and may be used as an organic separator itself. In addition, the porous film formed of the binder resin composition for secondary battery separator porous films may be laminated | stacked on an organic separator, and may be used as an organic separator itself. Moreover, the porous film formed of the binder resin composition for secondary battery electrode porous films can be laminated | stacked on an electrode, and can be used.

(Method for Producing Porous Membrane for Secondary Battery)

As a method of manufacturing the porous film for secondary batteries, the porous membrane composition containing (I) said nonelectroconductive particle, a water-soluble thickener (A), a carbodiimide compound crosslinking agent (B), a particulate polymer (C), and a dispersion medium is prescribed | regulated. The method of apply | coating on a base material (pole plate for positive electrodes, pole plate for negative electrodes, or organic separator), and then drying; (II) Said nonelectroconductive particle, water-soluble thickener (A), carbodiimide compound crosslinking agent (B), particulate form Method of drying this after immersing the porous film composition containing a polymer (C), a dispersion medium, and arbitrary components in a base material (pole plate for positive electrodes, pole plate for negative electrodes, or organic separator); (III) said nonelectroconductive particle, The porous membrane obtained by apply | coating and film-forming the porous film composition containing a water-soluble thickener (A), a carbodiimide compound crosslinking agent (B), a particulate-form polymer (C), a dispersion medium, and arbitrary components on a peeling film, The method of transferring on a predetermined base material (pole plate for positive electrodes, pole plate for negative electrodes, or organic separator) is mentioned. Among these, the method of apply | coating a porous film composition (I) to a base material (pole plate for positive electrodes, a pole plate for negative electrodes, or an organic separator), and then drying is most preferable at the point which is easy to control the film thickness of a porous film.

Although the porous film of this invention is manufactured by the method of above-mentioned (I)-(III), the detailed manufacturing method is demonstrated below.

In the method of (I), the porous film of this invention is manufactured by apply | coating a porous film composition on a predetermined base material (pole plate for positive electrodes, pole plate for negative electrodes, or organic separator), and drying.

The method of apply | coating a porous film composition on a base material is not restrict | limited, For example, methods, such as the doctor blade method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, the brush coating method, are mentioned. Especially, the gravure method is preferable at the point from which a uniform porous film is obtained.

As a drying method, the drying method by irradiation with warm air, hot air, low humidity wind, vacuum drying, (far) infrared rays, an electron beam, etc. are mentioned, for example. It is preferable that drying temperature is 50-200 degreeC.

In the method of (II), the porous film of this invention is manufactured by immersing a porous film composition in a base material (pole plate for positive electrodes, pole plate for negative electrodes, or organic separator), and drying. The method of immersing this porous membrane composition in a base material is not restrict | limited, For example, it can be immersed by dip-coating with a dip coater etc.

As a drying method, the method similar to the drying method in the method of above-mentioned (I) is mentioned.

In the method of (III), a porous film composition is apply | coated and film-formed on a peeling film, and the porous film formed on the peeling film is manufactured. Next, the obtained porous film is transferred onto a substrate (pole plate for positive electrode, pole plate for negative electrode, or organic separator).

As a coating method, the method similar to the coating method in the method of above-mentioned (I) is mentioned. The transfer method is not particularly limited.

The porous membrane obtained by the method of (I)-(III) is then a base material (pole plate for positive electrodes, pole plate for negative electrodes, or organic separator) by a pressurization process using a metal mold | die press, a roll press, etc. as needed. And adhesiveness of the porous membrane can also be improved. However, at this time, if excessively pressurized, the porosity of the porous membrane may be damaged, so that the pressure and the pressurization time are appropriately controlled.

The thickness of the porous membrane is not particularly limited and is appropriately set according to the use or application of the porous membrane. However, if the thickness is too thin, a uniform membrane cannot be formed. On the contrary, the thickness per volume (weight) in the battery is too thick. 0.5-50 micrometers is preferable and 0.5-10 micrometers is more preferable at the point (capacity) decreasing.

The porous film of this invention is formed into a film on the surface of a base material (pole plate for positive electrodes, pole plate for negative electrodes, or an organic separator), and is used especially suitably as a protective film or separator of the electrode active material layer mentioned later. The porous film of the present invention may be formed on any surface of a secondary battery positive electrode, a secondary battery negative electrode, or an organic separator, or may be formed on all of a positive electrode, a negative electrode, and an organic separator.

(materials)

(Pole plate for positive electrode)

The positive electrode plate for the positive electrode is obtained by applying a composition for the positive electrode containing a positive electrode active material, a binder for the positive electrode, a solvent used for the production of the positive electrode, a conductive agent, a thickener, and the like, as necessary, to the surface of the current collector and drying it. Lose. That is, it can obtain by forming a positive electrode active material layer on the surface of an electrical power collector.

As a positive electrode active material, the metal oxide which can dope and dedope lithium ion reversibly is mentioned. As such a metal oxide, lithium cobalt acid, lithium nickelate, lithium manganate, lithium iron phosphate, etc. are mentioned, for example. In addition, the positive electrode active material illustrated above may be used individually according to a use, may be used individually, and may be used in mixture of multiple types.

As the binder for the positive electrode, for example, polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, poly Resins such as acrylonitrile derivatives; soft polymers such as acrylic soft polymers, diene soft polymers, olefin soft polymers, and vinyl soft polymers. In addition, a binder may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

As a solvent used for preparation of an electrode plate, you may use any of water and an organic solvent. Examples of the organic solvent include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate and γ- Esters such as butyrolactone and ε-caprolactone; acylonitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether: methanol, ethanol, isopropanol, ethylene glycol, ethylene Alcohols, such as glycol monomethyl ether; Amides, such as N-methylpyrrolidone and N, N- dimethylformamide, etc. are mentioned, Especially, N-methylpyrrolidone (NMP) is preferable. In addition, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. Especially, it is preferable to use water as a solvent.

What is necessary is just to adjust the quantity of a solvent so that the viscosity of the composition for positive electrodes may become a viscosity suitable for application | coating. Specifically, the concentration of the solid content of the composition for the positive electrode is preferably 30 to 90% by weight, more preferably 40 to 80% by weight, and preferably adjusted to an amount that is more preferably used.

Specific examples of the conductive agent include conductive carbon blacks such as furnace black, acetylene black, and Ketjen black (registered trademark of Akzo Nobel Chemicals Vesrotene Pennote Shop). Among these, acetylene black and furnace black are more preferable. These electrically conductive agents can be used individually or in combination of 2 or more types.

Examples of the thickener include cellulose-based polymers such as carboxymethyl cellulose, methyl cellulose and hydroxypropyl cellulose and their ammonium salts and alkali metal salts; (modified) poly (meth) acrylic acid and their ammonium salts and alkali metal salts; (modified) polyvinyl alcohol, Polyvinyl alcohols such as copolymers of acrylic acid or acrylate and vinyl alcohol, maleic anhydride or copolymers of maleic acid or fumaric acid and vinyl alcohol; polyethylene glycol, polyethylene oxide, polyvinylpyrrolidone, modified polyacrylic acid, starch oxide Starch phosphate, casein, various modified starches, acrylonitrile-butadiene copolymer hydride and the like. In addition, in this invention, "(modified) poly" means "unmodified poly" or "modified poly".

The current collector is not particularly limited as long as it is an electrically conductive material and is electrochemically durable. Since the current collector has heat resistance, a metal material is preferable, and examples thereof include iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, Gold, platinum, etc. are mentioned. Especially, aluminum is preferable. The shape of the current collector is not particularly limited, but a sheet-like one having a thickness of about 0.001 to 0.5 mm is preferable. In order that an electrical power collector may raise adhesive strength with a positive electrode active material layer, it is preferable to use it, roughening previously. As a roughening method, a mechanical polishing method, an electrolytic polishing method, a chemical polishing method, etc. are mentioned. In the mechanical polishing method, a abrasive cloth having a fixed abrasive particle, a grindstone, an emery buff, a wire brush provided with a steel wire, or the like is used. Moreover, in order to improve the adhesive strength and electroconductivity of a positive electrode active material layer, you may form intermediate | middle layers, such as a conductive adhesive layer, on the surface of an electrical power collector.

The method of apply | coating the composition for positive electrodes to the surface of an electrical power collector is not specifically limited. For example, methods, such as a doctor blade method, a dip method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, and the brush coating method, are mentioned.

As a drying method, the drying method by irradiation with warm air, hot air, low humidity wind, vacuum drying, irradiation with (far) infrared rays, an electron beam, etc. are mentioned, for example. The drying time is preferably 5 minutes to 30 minutes, and the drying temperature is preferably 40 ° C to 180 ° C.

Moreover, after apply | coating and drying the composition for positive electrodes on the surface of an electrical power collector, it is preferable to pressurize a positive electrode active material layer using a metal mold | die press, a roll press, etc. as needed. By a pressurizing process, the porosity of a positive electrode active material layer can be made low. The porosity is preferably 5 to 30%, more preferably 7% to 20%. If the porosity is too low, a high volume capacity is hard to be obtained, and the positive electrode active material layer tends to be easily peeled from the current collector. Moreover, when porosity is too high, it will become difficult to obtain sufficient charge efficiency and discharge efficiency.

In addition, when a positive electrode active material layer contains a curable polymer, it is preferable to harden a polymer after formation of a positive electrode active material layer.

(Pole plate for the negative electrode)

The negative electrode plate for negative electrode is coated with a negative electrode composition containing the negative electrode active material, the binder for negative electrode, the solvent used for the production of the electrode plate, a thickener, a conductive agent, etc. used as necessary, on the surface of the current collector described above. It can obtain by drying. That is, it can obtain by forming a negative electrode active material layer on the surface of an electrical power collector.

Examples of the negative electrode active material include low crystalline carbon (amorphous carbon) such as digraphitizable carbon, non-graphitizable carbon, pyrolytic carbon, graphite (natural graphite, artificial graphite), alloy materials such as tin and silicon, and silicon Oxides, such as an oxide, tin oxide, and a lithium titanate, etc. are mentioned. In addition, the negative electrode active material illustrated above may be used individually suitably according to a use, and may be used in mixture of multiple types.

As a binder for negative electrodes, it does not restrict | limit especially A well-known thing can be used. For example, numbers of polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives and the like In addition, soft polymers such as an acrylic soft polymer, a diene soft polymer, an olefin soft polymer, and a vinyl soft polymer can be used. These may be used independently or may use 2 or more types together.

Moreover, the solvent, the thickener, and the electrically conductive agent used for preparation of a pole plate can use the same thing as what can be used for the pole plate for positive electrodes mentioned above.

Moreover, the thing similar to what can be used for the electrode plate for positive electrodes mentioned above also about an electrical power collector can be used.

The negative electrode plate for negative electrode can be manufactured by the same method as the positive electrode plate for positive electrode.

(Organic separator)

As an organic separator, a well-known thing, such as a porous resin coat containing the microporous film or nonwoven fabric made from polyolefins, such as polyethylene and a polypropylene, and aromatic polyamide resin, an inorganic ceramic powder, can be used. For example, a microporous membrane made of resin such as polyolefin-based (polyethylene, polypropylene, polybutene, polyvinyl chloride), and mixtures or copolymers thereof, polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, Woven microporous membranes or polyolefin-based fibers made of resins such as polyimide, polyimideamide, polyaramid, polycycloolefin, nylon, polytetrafluoroethylene, or the like, or a nonwoven fabric or an aggregate of insulating material particles. have.

(Lithium ion secondary battery)

The lithium ion secondary battery of this invention contains a positive electrode, a negative electrode, a separator, and electrolyte solution, At least one of a positive electrode, a negative electrode, and a separator is provided with the porous film obtained by a porous film composition.

In addition, when using the positive electrode which does not have the said porous film, the above-mentioned electrode plate for positive electrodes can be used as a positive electrode. Moreover, when using the negative electrode which does not have the said porous film, the above-mentioned pole plate for negative electrodes can be used as a negative electrode. Moreover, when using the separator which does not have the said porous film, the organic separator mentioned above can be used.

(Electrolyte amount)

As electrolyte solution, what melt | dissolved lithium salt in the non-aqueous solvent as a supporting electrolyte can be used, for example. 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 NLi, (CF ₃ SO ₂₎ can be cited lithium salts such as _{2 NLi, (C 2 F 5} SO 2) NLi. LiPF ₆ , LiClO ₄ , CF ₃ SO ₃ Li, which is particularly soluble in a solvent and exhibits high dissociation degree, is 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 preferably 1 to 30% by weight, more preferably 5 to 20% by weight with respect to the electrolyte solution. Even if the amount of the supporting electrolyte is too small or too large, the ionic conductivity is lowered, and the charge characteristics and discharge characteristics of the secondary battery may be lowered.

As a solvent used for electrolyte solution, if a supporting electrolyte is dissolved, it will not specifically limit. 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-containing compounds such as sulfolane and dimethyl sulfoxide and the like. In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable because high ion conductivity is easy to be obtained and the use temperature range is wide. In addition, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Moreover, you may contain an additive in electrolyte solution as needed. As an additive, carbonate type compounds, such as vinylene carbonate (VC), are preferable, for example. In addition, an additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.

Incidentally, as an electrolyte other than the above, for example, polyethylene oxide, a gel polymer electrolyte impregnated with the electrolytic solution in the polymer electrolyte, such as polyacrylonitrile; may include sulfurized lithium, LiI, such as an inorganic solid electrolyte such as Li ₃ N .

(Method for Manufacturing Secondary Battery)

The manufacturing method of the secondary battery of this invention is not specifically limited. For example, the negative electrode and the positive electrode may overlap each other via a separator, and may be wound or bent depending on the shape of the battery and placed in a battery container to inject and seal the electrolyte solution in the battery container. If necessary, an overcurrent prevention element such as an expanded metal, a fuse, a PTC element, a lead plate, or the like may be placed to prevent a pressure increase in the battery and overcharge / discharge. The shape of the battery may be, for example, a laminate cell type, a coin type, a button type, a sheet type, a cylindrical shape, a square shape, or a flat type.

In addition, when forming the above-mentioned porous film on the surface of the electrode active material layer of a positive electrode or a negative electrode, even if a separator is not used at the time of manufacture of a lithium ion secondary battery, a porous film can fulfill the function as a separator, and lithium is low cost. The ion secondary battery can be manufactured. Moreover, even when a separator is used at the time of manufacture of a lithium ion secondary battery, since the hole formed in the separator surface is not filled, higher rate characteristic can be expressed. In addition, by forming the porous membrane on the surface of the electrode active material layer, even if the separator causes shrinkage due to heat, a short circuit between the positive electrode and the negative electrode is not caused, and high safety can be maintained.

According to the porous membrane composition of this invention, the amount of moisture content is small and the porous membrane layer excellent in adhesive strength can be obtained.

Example

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to a following example, It can change arbitrarily in the range which does not deviate from the summary and equal range of this invention. In addition, "%" and "part" which show quantity in the following description are a basis of weight unless there is particular notice.

In Examples and Comparative Examples, evaluation of peel strength, moisture content, low temperature output characteristics, cell expansion, and cycle characteristics were performed as follows.

(Pill strength)

Examples and Comparative Examples, length 100 mm, cut into a rectangular test piece of 10 mm in width, and the electrolytic solution (1.0 mol / ℓ of _{LiPF 6 / EC + DEC (EC} / DEC = 1/2 volume ratio)), a separator prepared according to It was immersed at 60 ° C. for 72 hours and then dried. On the dried test piece, the surface of the porous membrane was faced down, and a cellophane tape was affixed on the surface of the porous membrane. At this time, what is prescribed | regulated to JIS Z1522 was used as a cellophane tape. In addition, the cellophane tape was fixed on a horizontal test bench. Then, the stress at the time of pulling off one end of an electrical power collector at 10 mm / min of tensile velocity vertically upward was measured. This measurement was performed 3 times, the average value of the stress was calculated | required, and the said average value was made into the peeling strength, and it showed in Table 1 and Table 2. The larger the measured peel strength, the greater the binding force between the porous membrane and the organic separator. That is, the larger the measured peel strength, the larger the adhesion strength.

(Water content)

The separator (organic separator with a porous film) manufactured by the Example and the comparative example is cut into the size of width 10cm x length 10cm, and it is set as a test piece. The test piece was left to stand at a temperature of 25 ° C. and a humidity of 50% for 24 hours, and thereafter, the amount of water in the test piece by the Karl Fischer method (JIS K-0068 (2001) water vaporization method, vaporization temperature 150 ° C.) using a total titration moisture meter. (W1) was measured.

Next, the water content (W2) was measured like the above about the test piece which left to stand at the temperature of 25 degreeC, dew point -60 degreeC, and humidity of 0.05% for 24 hours.

From the measured moisture content W1 and W2, ratio (W1 / W2) was computed and evaluated by the following reference | standard. The smaller the difference between W1 and W2, the smaller the moisture content of the porous membrane. When the moisture content of the porous membrane is small, curl of the separator in the dry room where battery production is performed can be suppressed. Moreover, since the less the moisture content of a porous film | membrane does not produce the side reaction in a secondary battery by moisture, and does not reduce battery characteristics, such as high temperature cycling characteristics, it is preferable.

A: W1 / W2 is less than 2.0

B: W1 / W2 is 2.0 or more and less than 2.5

C: W1 / W2 is 2.5 or more and less than 3.0

D ： W1 / W2 is 3.0 or more

(Low temperature output characteristics)

800 mAh wound lithium ion secondary batteries in Examples and Comparative Examples were prepared and allowed to stand for 24 hours in an environment of 25 ° C., followed by 4.2 V, 0.1 C, and 5 hours of charging in an environment of 25 ° C. The operation was performed and the voltage V0 at that time was measured. Thereafter, the discharge was operated at a discharge rate of 1 C in a -10 ° C environment, and the voltage V1 15 seconds after the start of discharge was measured. The low temperature output characteristics are evaluated by the voltage drop represented by ΔV = V0-V1, and the smaller the value, the better the low temperature output characteristics.

(Cell expansion)

After producing the lithium ion secondary battery of the 800 mAh wound type | mold cell in an Example and a comparative example and letting it stand for 24 hours in 25 degreeC environment, it is 4.35V, 0.1C charge, 2.75V in 25 degreeC environment. Charge / discharge operation was performed by discharging at 0.1 C. Thereafter, the wound cell was immersed in flow paraffin, and the volume V0 thereof was measured. Furthermore, in 60 degreeC environment, charging / discharging was repeated, the winding type cell after 1000 cycles was immersed in the liquid paraffin, and the volume V1 was measured. The expansion of the cell was evaluated by the volume change rate of the cell represented by ΔV (%) = (V1-V0) / V0 × 100. Smaller values indicate better gas suppression.

(Cycle characteristics)

After producing the lithium ion secondary battery of the 800 mAh wound type | mold cell in an Example and a comparative example and letting it stand for 24 hours in 25 degreeC environment, it is 4.35V, 0.1C charge, 2.75V in 25 degreeC environment. , Charging and discharging were performed with 0.1 C discharge, and the initial capacity C0 was measured. In addition, charging and discharging were repeated in a 60 degreeC environment, and the capacity C1 after 1000 cycles was measured. The high temperature cycle characteristic was evaluated by the capacity retention rate represented by (DELTA) C = C1 / C0x100 (%). Higher values indicate better life characteristics.

(Example 1)

(1.Separator)

1.1. Production of Alumina Particles]

Aluminum hydroxide having a volume average particle diameter of 2.8 μm obtained by the Bayer method was injected into the box-shaped bundle of pores at an injection density of 0.61 g / cm 3. This box-shaped claw was installed in the furnace of a stationary electric furnace ("Sirikonittoro" by Shirikonitto High Temperature Industrial Co., Ltd.), and baked at the baking temperature of 1180 degreeC for 10 hours. Thereafter, the produced particles of α alumina were taken out of the furnace.

A vibration ball mill (&quot; vibration mill &quot; manufactured by Central Chemical Co., Ltd.) was prepared in which 7.8 kg of alumina balls having a diameter of 15 mm were housed in a 6-liter pot. In the pot, 1.0 kg of the particles of α alumina and 15 g of ethanol were filled and ground for 36 hours to obtain α alumina particles having a volume average particle diameter of 0.6 μm.

1.2. Preparation of Water-Soluble Thickener (A)]

As the water-soluble thickener (A), carboxymethyl cellulose (Dicell 1220 manufactured by Daicel Chemical Industries, Ltd., etherification degree 0.8 to 1.0, 1% aqueous solution viscosity 10 to 20 mPa · s, hereinafter may be referred to as “CMC”). And sodium polyacrylate D1 (weight average molecular weight 25000, 1% aqueous solution viscosity 3000 mPa * s) were used. To 50 parts of water, 1.5 parts and 0.1 parts of solids were added, respectively.

1.3. Carbodiimide compound crosslinking agent (B)]

As a carbodiimide compound crosslinking agent (B), polycarbodiimide (The Nisshinbo Chemical company make, product name: Carbodilite (registered trademark) SV-02, NCN equivalent 429, 1-phase water solubility) was used.

1.4. Production of Particulate Polymer (C)]

The particulate polymer (C) was produced as follows.

To the reactor equipped with a stirrer, 70 parts of ion-exchanged water, 0.15 parts of sodium lauryl sulfate (manufactured by Cao Chemical, product name "Emar 2F") as an emulsifier, and 0.5 parts of ammonium persulfate were respectively supplied, and the gas phase part was replaced with nitrogen gas. It heated up at 60 degreeC.

On the other hand, in another vessel, 50 parts of ion-exchanged water, 0.5 part of sodium dodecylbenzenesulfonate as a dispersant, and butyl acrylate (hereinafter sometimes referred to as "BA") as a polymerizable monomer, 94 parts of acrylonitrile ( Hereinafter, it may be called "AN." 2 parts, acrylamide (Hereinafter, it may be called "AAm.") 1 part, methacrylic acid (Hereinafter, it may be called "MMA.") 2 Part and allylglycidyl ether (hereinafter, may be referred to as "AGE") were mixed to obtain a monomer mixture. This monomer mixture was continuously added to the reactor over 4 hours to conduct polymerization. During addition, reaction was performed at 60 degreeC. After completion of the addition, the mixture was further stirred at 70 ° C for 3 hours to terminate the reaction, to prepare an aqueous dispersion containing a (meth) acryl polymer as a binder for the porous membrane.

The volume average particle diameter D50 of the obtained (meth) acryl polymer was 0.36 µm, and the glass transition temperature was -45 ° C.

1.5. Preparation of Dispersion of Non-Conductive Particles]

100 parts of the alumina particles obtained in the step [1.1] and 1.6 parts of the aqueous solution of the water-soluble thickener (A) obtained in the step [1.3] were mixed, and water having an electrical conductivity of 10 μS / cm was added to obtain a solid content concentration. The dispersion of nonelectroconductive particle was obtained by adjusting to 50 weight%.

1.6. Dispersion of Dispersion of Non-Conductive Particles]

The dispersion of the nonelectroconductive particle obtained at the said process [1.5.] Was disperse | distributed for 1 hour by the energy of 4000 rotation and 5.4 Wh / kg by the medialess dispersing apparatus (In-line grinder MKO by IKA Corporation).

1.7. Production of Porous Membrane Composition]

0.05 part of carbodiimide compound crosslinking agent (B) and 6 parts of particulate-form polymers (C) were added to the dispersion of the nonelectroconductive particle obtained at the said process [1.6.]. Furthermore, 0.2 part of polyethyleneglycol surfactants (Sannofuco SN wet 366) were mixed, solid content concentration 40%, the viscosity 160 mPa * s (value measured by the temperature of 25 degreeC and rotation speed 60rpm using a Brookfield viscometer, below) In the same manner, the porous membrane composition was prepared.

1.8. Manufacture of Separator for Secondary Battery]

The organic separator (16 micrometers in thickness, Gurley value 210s / 100 cc) which consists of a porous base material (PE base material) made from polyethylene was prepared. The porous membrane composition was applied to both surfaces of the prepared organic separator and dried at 50 ° C. for 3 minutes. This obtained the separator provided with the porous film of single-sided thickness of 3 micrometers. About the obtained separator, the peeling strength and water content were measured by the said method.

(2.negative electrode)

2.1. Production of Binder for Negative Electrode]

In a 5 MPa pressure vessel with a stirrer, 33.5 parts of 1,3-butadiene, 3.5 parts of itaconic acid, 62 parts of styrene, 1 part of 2-hydroxyethyl acrylate, 0.4 part of sodium dodecylbenzenesulfonate as an emulsifier, ion-exchanged water 150 parts and 0.5 part of potassium persulfate were added as a polymerization initiator, and after fully stirring, it heated at 50 degreeC and started superposition | polymerization. When the polymerization conversion ratio reached 96%, the mixture was cooled to stop the reaction to obtain a mixture containing a particulate binder (SBR). A 5% aqueous sodium hydroxide solution is added to the mixture containing the particulate binder, and after adjusting to pH 8, the unreacted monomer is removed by distillation under reduced pressure by heating, and then cooled to 30 ° C. or lower to contain the desired particulate binder. An aqueous dispersion was obtained.

2.2. Production of Negative Electrode]

100 parts of artificial graphite (average particle diameter: 15.6 µm) and a 2% aqueous solution of carboxymethylcellulose sodium salt ("MAC350HC" manufactured by Nippon Paper Co., Ltd.) as thickeners were prepared at 1 part by solid content and at a solid content concentration of 68% by ion exchange water. Then, it mixed for 25 degreeC 60 minutes. Furthermore, after preparing to 62% of solid content concentration by ion-exchange water, it mixed again for 25 degreeC 15 minutes. 1.5 parts of said particulate-form binders and ion-exchange water were put into the said liquid mixture in solid content equivalency, it was adjusted so that it might become final solid content concentration 52%, and it mixed again for 10 minutes. This was degassed under reduced pressure to obtain a composition for negative electrode having good fluidity.

2.3. Production of Negative Electrode]

The composition for negative electrodes obtained above was apply | coated so that the film thickness after drying might be about 150 micrometers on the copper foil of thickness 20micrometer which is an electrical power collector by a comma coater, and it dried. This drying was performed by conveying the inside of 60 degreeC oven over 2 minutes for copper foil at a speed | rate of 0.5 m / min. Then, it heat-processed at 120 degreeC for 2 minutes, and obtained the negative electrode disk before press. The negative electrode original fabric before this press was rolled by the roll press, and the negative electrode after the press whose thickness of a negative electrode active material layer is 80 micrometers was obtained.

[3. Positive electrode]

3.1. Production of Positive Electrode Composition]

100 parts of LiCoO ₂ with a volume average particle diameter of 12 μm as a positive electrode active material, ₂ parts of acetylene black (“HS-100” manufactured by Denki Chemical Industries, Ltd.) as a conductive agent, and PVDF (manufactured by Kureha, ＃ 7208) as a binder for the positive electrode ) Was mixed with 2 parts and NMP as solid content, and it was set as the quantity which will make total solid content concentration 70%. These were mixed by the planetary mixer and the composition for positive electrodes was prepared.

3.2. Production of Positive Electrode]

The composition for positive electrodes of said [3.1.] Was apply | coated so that the film thickness after drying might be about 150 micrometers on the aluminum foil of thickness 20micrometer which is an electrical power collector with a comma coater. This drying was performed by conveying the inside of 60 degreeC oven over 2 minutes for copper foil at a speed | rate of 0.5 m / min. Then, it heat-processed at 120 degreeC for 2 minutes, and obtained the positive electrode.

[4. Production of Lithium Ion Secondary Battery]

The positive electrode after press was cut into 49 * 5cm <2>. The separator cut into 55x5.5 cm <2> was arrange | positioned on the positive electrode active material layer of the cut positive electrode. The negative electrode after pressing was cut into a square of 50 x 5.2 cm 2, and the cut negative electrode was arranged on the side opposite to the positive electrode of the separator so that the surface of the negative electrode active material layer side faced the separator. This was wound by a winding machine to obtain a winding body. This wound body was pressed at 60 ° C. and 0.5 MPa to obtain a flat body. The pyeonpyeongche to envelope the outer aluminum wrapper as external of the battery, the electrolytic solution (solvent: EC / DEC / VC = 68.5 / 30 / 1.5 by volume, the electrolyte: LiPF ₆ concentration of 1 M) was fed to eliminate any residual air is. In addition, in order to seal the opening of an aluminum wrapping material, the aluminum exterior was closed by heat-sealing 150 degreeC. This manufactured the 800 mAh wound type lithium ion secondary battery.

About the lithium ion secondary battery obtained in this way, low-temperature output characteristics, cell expansion, and cycling characteristics were evaluated by the method mentioned above.

(Example 2)

Said [1.2. In the manufacture] of the water-soluble thickener (A), the separator is used in the same manner as in Example 1 except that the kind of sodium polyacrylate to be used is sodium polyacrylate D2 (weight average molecular weight 10000, 1% aqueous solution viscosity 1200 mPa · s). And the production of lithium ion secondary batteries were carried out.

(Example 3)

Said [1.2. In the manufacture] of a water-soluble thickener (A), the separator is the same as that of Example 1 except having set the kind of sodium polyacrylate to be sodium polyacrylate D3 (weight average molecular weight 70000, 1% aqueous solution viscosity 8400 mPa * s). And the production of lithium ion secondary batteries were carried out.

(Example 4)

Said [1.1. Instead of manufacture] of alumina particle | grains, the nonelectroconductive fine particle which consists of organic compounds was manufactured.

[Production of Non-Conductive Fine Particles Composed of Organic Compound]

In a reactor equipped with a stirrer, 0.06 parts of sodium dodecyl sulfate, 0.2 parts of ammonium persulfate, and 100 parts of ion-exchanged water were added and mixed to obtain a mixture N1, and the temperature was raised to 80 ° C.

On the other hand, 98 parts of butyl acrylate, 2.0 parts of methacrylic acid, 0.1 part of sodium dodecyl sulfate, and 100 parts of ion-exchange water were mixed as a monomer, and the dispersion of monomer mixture M1 was prepared.

The dispersion of this monomer mixture M1 was continuously added to the mixture N1 and polymerized over 4 hours. During the continuous addition of the dispersion of the monomer mixture M1, the temperature of the reaction system was maintained at 80 ° C. to carry out the reaction. After the completion of the continuous addition, the reaction was continued for 3 hours at 90 ° C.

This obtained the water dispersion of the seed polymer particle S1 of 360 nm of number average particle diameters.

In the reactor equipped with a stirrer, 20 parts of the aqueous dispersion of the seed polymer particles S1 obtained in the above on the basis of solid content (that is, the weight of the seed polymer particles S1) and ethylene glycol dimethacrylate as monomer (Kyoisha Chemical Co., Ltd. Light ester EG "), 1.0 part of acrylic acid, 1.0 part of acrylic acid, sodium dodecylbenzene sulfonate as emulsifier, t-butylperoxy-2-ethylhexanoate as a polymerization initiator (Nichiyu Co., Ltd." perbutyl O "). ) 4.0 parts and 200 parts of ion-exchanged water. By stirring this at 35 degreeC for 12 hours, the monomer and polymerization initiator were fully absorbed by the seed polymer particle S1. Then, this was polymerized at 90 degreeC for 5 hours. Thereafter, steam was introduced to remove unreacted monomers and initiator decomposition products to obtain nonconductive fine particles made of an organic compound.

A separator and a lithium ion secondary battery were produced in the same manner as in Example 1, except that non-conductive fine particles made of the organic compound were used instead of the alumina.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 25%, and the viscosity was 50 mPa * s.

(Example 5)

Said [1.2. Preparation of a separator and lithium ion 2 similarly to Example 1 except having used polyvinyl alcohol (Hereinafter, it may be called "PVOH") instead of carboxymethylcellulose in manufacture of a water-soluble thickener (A). The secondary battery was manufactured.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 42%, and the viscosity was 150 mPa * s.

(Example 6)

Said [1.2. In the production of the water-soluble thickener (A)], except that sodium polyacrylate was used and 1.6 parts of carboxymethyl cellulose was used for 50 parts of water to prepare a water-soluble thickener (A). Manufacture and manufacture of the lithium ion secondary battery were implemented.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 41%, and the viscosity was 140 mPa * s.

(Example 7)

Said [1.2. Production of a water-soluble thickener (A)] The preparation of a separator and lithium in the same manner as in Example 1 except that carboxymethyl cellulose and sodium polyacrylate were added so that the solid content was 0.4 parts and 0.1 parts with respect to 50 parts of water, respectively. The ion secondary battery was produced.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 47%, and the viscosity was 150 mPa * s.

(Example 8)

Said [1.2. Production of a water-soluble thickener (A)] Preparation of a separator and lithium as in Example 1 except that carboxymethylcellulose and sodium polyacrylate were added so that solid content was 1.5 parts and 6.5 parts with respect to 50 parts of water, respectively. The ion secondary battery was produced.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 32%, and the viscosity was 160 mPa * s.

(Example 9)

Said [1.3. Carbodiimide compound crosslinking agent (B)] as a carbodiimide compound crosslinking agent (B), polycarbodiimide (manufactured by Nisshinbo Chemical Co., Ltd., product name: Carbodilite (registered trademark) V-02, NCN equivalent 600, 1 The separator was manufactured and the lithium ion secondary battery was produced similarly to Example 1 except having used phase water solubility).

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 40%, and the viscosity was 160 mPa * s.

(Example 10)

Said [1.3. Carbodiimide compound crosslinking agent (B)] as a carbodiimide compound crosslinking agent (B), polycarbodiimide (manufactured by Nisshinbo Chemical Co., Ltd., product name: Carbodilite (registered trademark) V-04, NCN equivalent 335, 1) The separator was manufactured and the lithium ion secondary battery was produced similarly to Example 1 except having used phase water solubility).

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 39%, and the viscosity was 165 mPa * s.

(Example 11)

Said [1.7. Production of a porous film composition WHEREIN: The separator was produced and the lithium ion secondary battery was produced like Example 1 except having made the quantity of the carbodiimide compound crosslinking agent (B) added into 0.01 part. Solid content concentration of the obtained porous film composition was 40%, and the viscosity was 160 mPa * s.

(Example 12)

Said [1.7. In the production of the porous membrane composition, a separator and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the amount of the carbodiimide compound crosslinking agent (B) to be added was 1 part. Solid content concentration of the obtained porous film composition was 38%, and the viscosity was 160 mPa * s.

(Example 13)

In a 5 MPa pressure vessel equipped with a stirrer, 67.5 parts of ethyl acrylate, 30 parts of methacrylic acid, 2.5 parts of trifluoromethyl methacrylate, 1.0 part of sodium dodecylbenzenesulfonate, 150 parts of ion-exchanged water and 0.5 part of potassium persulfate After the mixture was sufficiently stirred and then heated to 60 ° C., polymerization was initiated. When the polymerization conversion ratio reached 96%, the mixture was cooled to terminate the reaction to obtain an aqueous solution containing a water-soluble polymer. 10% ammonia water was added to the aqueous solution containing the water-soluble polymer obtained in this way, it adjusted to pH 8, and the aqueous solution containing the desired water-soluble polymer was obtained. The weight average molecular weight of this water-soluble polymer was 128000, and the viscosity of 1% aqueous solution was 1500 mPa * s.

Said [1.2. Preparation of water-soluble thickener (A)] Production of a separator in the same manner as in Example 1 except that the water-soluble polymer was added so that the solid content was 1.6 parts with respect to 50 parts of water instead of carboxymethyl cellulose and sodium polyacrylate. And the lithium ion secondary battery was manufactured.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 39%, and the viscosity was 160 mPa * s.

(Example 14)

Said [1.2. Production] of water-soluble thickener (A), in the same manner as in Example 1 except that the solid content of the carboxymethyl cellulose and the water-soluble polymer prepared in Example 13 were added to 0.8 parts and 0.8 parts, respectively, to 50 parts of water. The separator and the lithium ion secondary battery were manufactured.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 40%, and the viscosity was 200 mPa * s.

(Example 15)

Said [1.2. Production] of water-soluble thickener (A), except that 50 parts by weight of water was added so that the solid content of sodium polyacrylate D1 and the water-soluble polymer prepared in Example 13 were 0.1 parts and 1.6 parts, respectively. Similarly, the separator and the lithium ion secondary battery were manufactured.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 38%, and the viscosity was 160 mPa * s.

(Example 16)

Said [1.2. In the preparation of the water-soluble thickener (A)], the solid content of the carboxymethyl cellulose, sodium polyacrylate D1 and the water-soluble polymer prepared in Example 13 is added to 50 parts of water so that 0.8 parts, 0.1 parts, and 0.8 parts are added, respectively. A separator and a lithium ion secondary battery were produced in the same manner as in Example 1.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 39%, and the viscosity was 195 mPa * s.

(Example 17)

Said [1.4. Production of the particulate polymer (C)] as a polymerizable monomer, 95 parts of butyl acrylate, 2 parts of acrylonitrile, 1 part of acrylamide, 2-hydroxyethyl acrylate (hereinafter referred to as "β-HEA") A separator and a lithium ion secondary battery were produced in the same manner as in Example 1 except that 1 part and 1 part of allylglycidyl ether were used.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 39%, and the viscosity was 160 mPa * s.

(Example 18)

Said [1.4. Production of particulate polymer (C)] except that 94 parts of butyl acrylate, 2 parts of acrylonitrile, 1 part of acrylamide, 1 part of methacrylic acid and 2 parts of 2-ethylhexyl acrylate are used as the polymerizable monomer. In the same manner as in Example 1, the separator was manufactured and the lithium ion secondary battery was manufactured.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 39%, and the viscosity was 160 mPa * s.

(Example 19)

Said [1.8. In the manufacture of a secondary battery separator], the separator was manufactured in the same manner as in Example 1 except that an organic separator made of a polypropylene porous substrate (PP substrate) was used instead of the organic separator made of a porous substrate made of polyethylene. And the lithium ion secondary battery was manufactured.

(Example 20)

Said [1.8. In the manufacture of a secondary battery separator], the production of the separator and the production of the lithium ion secondary battery were carried out in the same manner as in Example 1 except that an organic separator based on a nonwoven fabric was used instead of the organic separator made of a porous substrate made of polyethylene. Carried out.

(Example 21)

Said [1.8. Production of a secondary battery separator] was omitted, and the porous membrane composition was applied to the surface of the negative electrode active material layer side of the negative electrode obtained in the above (2. negative electrode), and dried at 50 ° C. for 3 minutes. This obtained the negative electrode provided with the porous film of 3 micrometers in thickness.

Moreover, said [4. Production of a lithium ion secondary battery in the same manner as in Example 1 except that the lithium ion secondary battery was manufactured so as to face the surface where the porous film of the negative electrode was formed and the surface of the positive electrode faced and wound with a winding machine. Carried out.

(Comparative Example 1)

Said [1.7. Separation of the porous membrane composition in the same manner as in Example 1 except that the porous membrane composition was prepared without adding the carbodiimide compound crosslinking agent (B) and the addition amount of the particulate polymer (C) was 5 parts. And the production of lithium ion secondary batteries were carried out.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 40%, and the viscosity was 160 mPa * s.

(Comparative Example 2)

Said [1.2. In the manufacture] of a water-soluble thickener (A), it replaces carboxymethylcellulose and sodium polyacrylate, except having added the said polyethylene oxide (molecular weight 1000) so that solid content may be 1.5 part with respect to 50 parts of water, and Example 1 Similarly, the separator and the lithium ion secondary battery were manufactured.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 40%, and the viscosity was 120 mPa * s.

(Comparative Example 3)

Said [1.4. In the production of the particulate polymer (C), a separator and a lithium ion secondary battery are produced in the same manner as in Example 1 except that 97 parts of butyl acrylate and 3 parts of acrylonitrile are used as the polymerizable monomer. did.

In addition, said [1.7. Solid content concentration of the porous film composition obtained by the manufacture] of a porous film composition was 40%, and the viscosity was 170 mPa * s.

As shown in Table 1 and Table 2, a porous membrane containing non-conductive particles, a water-soluble thickener (A) containing a hydroxyl group and / or a carboxyl group, a carbodiimide compound crosslinking agent (B), and a particulate polymer (C) As a composition, the peeling strength of the porous film obtained using the porous film composition which has a functional group which a particulate-form polymer (C) reacts with a carbodiimide compound crosslinking agent (B) was favorable, and the moisture content was reduced. Moreover, the low temperature output characteristics, the cell expansion, and the cycle characteristics of the lithium ion secondary battery obtained using this porous membrane composition were favorable.

Claims (10)

Non-conductive particles,
A water-soluble thickener (A) containing a hydroxyl group and / or a carboxyl group,
Carbodiimide compound crosslinking agent (B),
Particulate Polymer (C)
As a porous membrane composition for lithium ion secondary batteries containing
The particulate polymer (C) is a porous membrane composition for a lithium ion secondary battery having a functional group reacting with the carbodiimide compound crosslinking agent (B). The method of claim 1,
For lithium ion secondary batteries, wherein the water-soluble thickener (A) is at least one member selected from the group consisting of carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, polyvinyl alcohol, polyacrylic acid or salts thereof. Porous membrane composition. The method of claim 1,
The porous membrane composition for lithium ion secondary batteries whose functional group reacting with the said carbodiimide compound crosslinking agent (B) in the said particulate polymer (C) is at least 1 sort (s) chosen from the group which consists of a carboxyl group, a hydroxyl group, a glycidyl ether group, and a thiol group. . The method of claim 1,
0.2-15 weight part of said water-soluble thickeners (A), 0.01-10 weight part of said carbodiimide compound crosslinking agents (B), and 1-15 weight part of said particulate-form polymers (C) with respect to 100 weight part of said nonelectroconductive particles. The porous membrane composition for lithium ion secondary batteries containing a part, respectively. The separator for lithium ion secondary batteries obtained by apply | coating the porous film composition for lithium ion secondary batteries of any one of Claims 1-4 on a board | substrate, and drying. The electrode for lithium ion secondary batteries obtained by apply | coating the porous film composition for lithium ion secondary batteries of any one of Claims 1-4 on a pole plate, and drying. A lithium ion secondary battery provided with a positive electrode, a negative electrode, electrolyte solution, and a separator, The said lithium ion secondary battery whose separator is the separator for lithium ion secondary batteries of Claim 5. A lithium ion secondary battery comprising a positive electrode, a negative electrode, an electrolyte solution, and a separator, wherein the positive electrode and / or the negative electrode is an electrode for a lithium ion secondary battery according to claim 6. As a manufacturing method of the separator for lithium ion secondary batteries obtained by apply | coating the porous film composition for lithium ion secondary batteries of any one of Claims 1-4 on a board | substrate, and drying it,
Coating said porous film composition for lithium ion secondary batteries onto a substrate;
Process to dry at 50-200 degreeC
The manufacturing method of the separator for lithium ion secondary batteries which has As a manufacturing method of the electrode for lithium ion secondary batteries obtained by apply | coating the porous film composition for lithium ion secondary batteries of any one of Claims 1-4 on a pole plate, and drying it,
Coating said porous film composition for lithium ion secondary batteries on a plate;
Process to dry at 50-200 degreeC
The manufacturing method of the electrode for lithium ion secondary batteries which has