Photocurable composition for lithium ion secondary battery sealing materials

Abstract

A photocurable composition for lithium ion secondary battery sealing materials according to the present invention contains, at a specific ratio, (A) a compound which has a skeleton of a polybutadiene and / or a hydrogenated polybutadiene, while having two (meth)acryloyl groups that have a number average molecular weight of 1,000 or more, (B-1) a monofunctional (meth)acrylate which has an alkenyl group or an alkyl group with an ester residue having 10 to 30 carbon atoms, (B-2) a monofunctional (meth)acrylate which has an alicyclic hydrocarbon group and / or an aromatic hydrocarbon group with an ester residue having 5 to 30 carbon atoms, and (C) a radical photopolymerization initiator.

Description

Photocurable composition for lithium-ion secondary battery sealant

[0001] The present invention relates to a photocurable composition for a sealing material for lithium ion secondary batteries, which can be preferably used in the production of lithium ion secondary batteries. In this specification, acrylate and / or methacrylate will be referred to as (meth)acrylate, acryloyl group and / or methacryloyl group will be referred to as (meth)acryloyl group, and acrylic acid and / or methacrylic acid will be referred to as (meth)acrylic acid.

[0002] In recent years, the widespread use of electric vehicles is expected to help solve various problems, including environmental issues. The widespread use of electric vehicles requires not only low prices but also horsepower and driving range comparable to those of gasoline-powered vehicles, and the development of secondary batteries has been actively pursued. Among these, lithium-ion secondary batteries, which are lightweight and have high energy density, are preferred as high-output power sources for driving vehicles such as electric vehicles (EVs), plug-in hybrid vehicles (PHVs), and hybrid vehicles (HVs), and demand for them is expected to continue to expand in the future.

[0003] In light of this situation, various studies have been conducted to improve the performance of lithium-ion secondary batteries. One of these studies is a so-called bipolar battery, in which one side of the current collector is a positive electrode and the other side is a negative electrode (Non-Patent Document 1). Stacking bipolar batteries allows for the production of a compact, high-voltage battery. The single cell of such a bipolar battery has a planar structure, and sealants are required at its edges to seal in the electrolyte.

[0004] Various studies have been conducted on sealing materials for sealing the ends of bipolar lithium-ion secondary batteries. For example, Patent Document 1 illustrates the configuration of a bipolar lithium-ion secondary battery, and describes that the sealing material is not particularly limited as long as it has adhesion to the positive and negative electrode current collectors and durability against the electrolyte, but that polymer materials, particularly thermosetting resins, are preferred (Patent Document 1:

[0047] ).

[0005] Patent Document 2 illustrates the structure of a bipolar lithium-ion secondary battery, shows a heat-sealable film as a sealing member, and shows that wrinkles in the resin current collector caused by heat fusion can be eliminated by using a reinforcing member.

[0006] Patent Document 3 discloses a photocurable composition that can be suitably used as a material for fixing and sealing the side surfaces of an all-solid-state battery having a laminated electrode body.

[0007] Patent Document 4 discloses an active energy ray-curable coating agent composition that can also be suitably used as an electrode protectant for lithium ion batteries.

[0008] Nikkei Electronics September 2017 issue, pages 13 to 15 JP 2017-103219 A JP 2017-16825 A JP 2022-15477 A International Publication No. 2013 / 157624 Pamphlet

[0009] However, conventional sealing materials for bipolar lithium ion secondary batteries have had various problems.

[0010] The thermosetting resins exemplified as preferred materials in Patent Document 1 require at least a few minutes, usually several tens of minutes to several hours, to harden, posing a problem in terms of mass production. The heat-sealable film described in Patent Document 2 has the advantage of short-time adhesion, but suffers from the problem of wrinkles occurring when heated to high temperatures. This document solves this problem by using a reinforcing member, but this creates another problem of complicated product configurations and manufacturing processes.

[0011] Patent Document 3 discloses a photocurable composition suitable for fixing and sealing the side surfaces of an all-solid-state battery having a laminated electrode body. The use of the photocurable composition enables rapid curing without the application of heat, improving mass productivity. However, because the all-solid-state battery exemplified therein does not contain an electrolyte solution, it is unclear whether the photocurable composition disclosed therein can be used as a sealant for a lithium-ion secondary battery containing an electrolyte solution.

[0012] Patent Document 4 discloses a photocurable coating composition that has excellent adhesion to aluminum foil (positive electrode foil) and does not show deterioration in appearance or adhesion even after immersion in a solvent used in an electrolyte, but the performance required for a sealing material is unclear. That is, there is no mention of the peel adhesion strength with the electrode substrate, the peel adhesion strength with the electrode substrate after immersion in an electrolyte, or the swelling rate of the cured product due to immersion in an electrolyte. Therefore, the present inventors evaluated the composition disclosed in Patent Document 4 and found that the peel adhesion strength with aluminum foil (positive electrode foil) and / or copper foil (negative electrode foil) after immersion in a solvent was not necessarily sufficient for use as a sealing material.

[0013] The present inventors have conducted extensive research to find a photocurable composition for a sealing material for lithium ion secondary batteries that can be applied at room temperature and cured in a short time, that has good peel adhesion strength to an electrode substrate before and after immersion in an electrolyte solution, and that has a small swelling rate due to immersion in an electrolyte solution.

[0014]

[0006] The present inventors conducted extensive research to solve the above-mentioned problems and discovered that a composition containing a compound having a polybutadiene and / or hydrogenated polybutadiene skeleton, two (meth)acryloyl groups, and a specific molecular weight, a compound having one (meth)acryloyl group per molecule containing two specific compounds (hereinafter referred to as a "monofunctional (meth)acrylate"), and a photoradical polymerization initiator in specific proportions can be applied at room temperature and cured in a short time, has good peel adhesion strength to an electrode substrate before and after immersion in an electrolyte solution, and exhibits a small swelling ratio due to immersion in an electrolyte solution, thereby completing the present invention. The present invention will be described in detail below.

[0015] The composition of the present invention can be applied at room temperature and cured in a short time, has good peel adhesion strength to the electrode substrate before and after immersion in an electrolyte, and exhibits a small swelling rate due to immersion in an electrolyte.

[0016] Fig. 1 is a diagram showing an example of a cross-sectional view of a bipolar lithium ion secondary battery. Fig. 2 is a diagram showing an example of a method for producing a lithium ion secondary battery using the composition of the present invention. Fig. 3 is a diagram showing an example of a method for producing a lithium ion secondary battery using the composition of the present invention.

[0017] The present invention is as follows: [1] Component (A): a compound having a polybutadiene and / or hydrogenated polybutadiene skeleton and two (meth)acryloyl groups in one molecule, the compound having a number average molecular weight of 1,000 or more; Component (B): a monofunctional (meth)acrylate containing the following components (B-1) and (B-2) as essential components: Component (B-1): a monofunctional (meth)acrylate having an alkyl or alkenyl group in which the ester residue has 10 to 30 carbon atoms; Component (B-2): a monofunctional (meth)acrylate having an ester residue with 5 to 30 carbon atoms and having an alicyclic hydrocarbon group and / or an aromatic hydrocarbon group; and Component (C): a photoradical polymerization initiator, wherein the curable component contains 10 to 80% by weight of component (A) and 20 to 90% by weight of component (B), based on a total of 100% by weight of the curable components. A photocurable composition for a lithium ion secondary battery sealing material, comprising 15 to 70 wt% of component (B-1) relative to 100 wt% of the total curable components, 5 to 50 wt% of component (B-2) relative to 100 wt% of the total curable components, and 0.1 to 20 wt% of component (C) relative to 100 parts by weight of the total curable components. [2] The photocurable composition for a lithium ion secondary battery sealing material according to [1], wherein component (A) is a urethane (meth)acrylate having a number average molecular weight of 5,000 to 50,000. [3] The photocurable composition for a lithium ion secondary battery sealing material according to [1] or [2], wherein component (B-1) includes an alkyl (meth)acrylate having 17 to 30 carbon atoms and a branched structure. [4] A method for manufacturing a lithium ion secondary battery, comprising applying or injecting the photocurable composition for a lithium ion secondary battery sealant described in any one of [1] to [3] above onto or into a side surface of a constituent material of the lithium ion secondary battery, and then irradiating the applied or injected surface with light. [5] A lithium ion secondary battery, in which the side surface of a constituent material of the lithium ion secondary battery is sealed with a cured product of the photocurable composition for a lithium ion secondary battery sealant described in any one of [1] to [3] above. Components (A) to (C), other components, the composition, and methods of use are described below. Note that the specific compounds listed in the description of components (A) to (C) below may be used alone or in combination of two or more types.

[0018] 1. Component (A) Component (A) is a compound having a polybutadiene skeleton and / or a hydrogenated polybutadiene skeleton in one molecule, and having two or more (meth)acryloyl groups with an Mn of at least 1,000. The (meth)acryloyl groups in component (A) may be present on a side chain or at the terminal, preferably a compound having a (meth)acryloyl group at the terminal, and particularly preferably a compound having a (meth)acryloyl group at both terminals.

[0019] The Mn (number average molecular weight) of component (A) is 1,000 or more, preferably 5,000 to 50,000, and more preferably 10,000 to 30,000. If a compound with an Mn of less than 1,000 is used, the adhesive strength to the aluminum foil will decrease. In the present invention, Mn (number average molecular weight) refers to the molecular weight measured by gel permeation chromatography (hereinafter referred to as "GPC") and converted into polystyrene.

[0020] Examples of component (A) include an oligomer in which a polybutadiene or hydrogenated polybutadiene skeleton and two or more (meth)acryloyl groups are bonded via urethane bonds (hereinafter referred to as "(A1)"), and an oligomer in which a polybutadiene or hydrogenated polybutadiene skeleton and two or more (meth)acryloyl groups are bonded via ester bonds (hereinafter referred to as "(A2)").

[0021] As component (A), (A1) and (A2) are preferred, with (A1) being preferred due to the excellent mechanical properties of the cured product, and a urethane (meth)acrylate oligomer having two (meth)acryloyl groups being more preferred. Furthermore, as the urethane (meth)acrylate oligomer having two (meth)acryloyl groups in (A1), a urethane (meth)acrylate oligomer having two (meth)acryloyl groups obtained by reacting a polybutadiene diol or a hydrogenated polybutadiene diol (a) (hereinafter referred to as "compound (a)"), a diisocyanate compound (b) (hereinafter referred to as "compound (b)"), and a hydroxyl group-containing (meth)acrylate (c) (hereinafter referred to as "compound (c)") is preferred. The Mn of compound (a) is preferably 500 to 10,000, more preferably 1,000 to 10,000.

[0022] In the present invention, in addition to the compound (a), other polyols may be used in combination with the compound (a) as needed, such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, cyclohexanedimethanol, and hydrogenated bisphenol A.

[0023] As the compound (b), various compounds can be used as long as they have two isocyanate groups in one molecule, such as tolylene diisocyanate, hydrogenated tolylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tolidine diisocyanate, naphthalene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, and hydrogenated xylylene diisocyanate.

[0024] As the compound (c), various compounds can be used as long as they are (meth)acrylates having a hydroxyl group. Specific examples include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, caprolactone-modified 2-hydroxyethyl (meth)acrylate, and glycidol di(meth)acrylate. Among these, hydroxyalkyl (meth)acrylates such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate are preferred.

[0025] Specific examples of (A2) include an esterification reaction product of polybutadiene or hydrogenated polybutadiene containing two or more hydroxyl groups with (meth)acrylic acid or (meth)acrylic acid halide, and a transesterification reaction product of polybutadiene or hydrogenated polybutadiene containing two or more hydroxyl groups with (meth)acrylate.

[0026] Component (A) is commercially available, and specific examples of (A1) include "TEA-1000" (polybutadiene-based urethane acrylate oligomer, Mn: approximately 3,000) manufactured by Nippon Soda Co., Ltd., "TEAI-1000" (hydrogenated polybutadiene-based urethane acrylate oligomer, Mn: approximately 3,000) manufactured by Nippon Soda Co., Ltd., "TE-2000" (polybutadiene-based urethane methacrylate oligomer) manufactured by Nippon Soda Co., Ltd., "CN9014" (polybutadiene-based urethane acrylate) manufactured by Sartomer, "CN301" (polybutadiene-based dimethacrylate) manufactured by Sartomer, "CN303" (polybutadiene-based dimethacrylate) manufactured by Sartomer, and "CN307" (polybutadiene-based diacrylate) manufactured by Sartomer. Specific examples of (A2) include "BAC-45" (polybutadiene diacrylate, Mn: 5,000) manufactured by Osaka Organic Chemical Industry Ltd. Among these compounds, "TEAI-1000," "TEA-1000," "CN9014," "CN307," and "BAC-45," which have an acryloyl group, are preferred because of their good photocurability.

[0027] As the component (A), a (meth)acrylate oligomer having a skeleton formed by hydrogenating polybutadiene is preferred, and a urethane (meth)acrylate having a skeleton formed by hydrogenating polybutadiene is more preferred.

[0028] When the (D) component described below is included in a 100% by weight total of the (A) and (B) components, the content of the (A) component should be 10 to 80% by weight, preferably 10 to 60% by weight, and particularly preferably 15 to 50% by weight, based on the total 100% by weight total of the (A) and (B) components. Hereinafter, the (A) and (B) components, or the (A), (B), and (D) components when the (D) component described below is included, are referred to as the "curable components." If the (A) component content is less than 10% by weight, the swelling ratio of the cured product after immersion in an electrolyte solution increases, resulting in a decrease in adhesive strength with the electrode foil after immersion in an electrolyte solution. On the other hand, if the (A) component content exceeds 80% by weight, the adhesive strength of the cured product decreases.

[0029] 2. Component (B) Component (B) is a monofunctional (meth)acrylate containing the following components (B-1) and (B-2) as essential components: Component (B-1): a monofunctional (meth)acrylate having an alkyl or alkenyl group in the ester residue with 10 to 30 carbon atoms Component (B-2): a monofunctional (meth)acrylate having an alicyclic hydrocarbon group and / or aromatic hydrocarbon group in the ester residue with 5 to 30 carbon atoms Here, the term "ester residue" refers to the group represented by R obtained by removing the ester bond from the structural moiety represented by -CO-O-R contained in the monofunctional (meth)acrylate.

[0030] Component (B-1) is a compound having an alkyl or alkenyl group (hereinafter, these groups are collectively referred to as "alkyl group, etc.") having 10 to 30 carbon atoms and one (meth)acryloyl group. In component (B), examples of the ester residue having an alkyl group, etc. having 10 to 30 carbon atoms include alkyl and alkenyl groups, and (poly)alkylene oxide groups having an alkyl or alkenyl group. The term "(poly)alkylene oxide group" refers to a group having one or more alkylene oxide units. In component (B-1), compounds having 9 or fewer carbon atoms, such as alkyl groups, have the problem of increasing the swelling rate of the cured product after immersion in an electrolyte solution. On the other hand, compounds having 31 or more carbon atoms, such as alkyl groups, have the problem of decreasing the adhesive strength to the electrode foil.

[0031] In the component (B-1), examples of compounds having an alkyl group include alkyl (meth)acrylates having an alkyl group having 10 to 30 carbon atoms, such as decyl (meth)acrylate, lauryl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, n-stearyl (meth)acrylate, isostearyl (meth)acrylate, and behenyl (meth)acrylate. Examples of compounds having an alkenyl group include 8-dodecenyl (meth)acrylate and 9-octadecenyl (meth)acrylate. Examples of (poly)alkylene oxide groups having an alkyl group include alkyl group-containing (poly)alkylene oxide groups. Examples of compounds having an alkyl group-containing (poly)alkylene oxide group include alkyl carbitol (meth)acrylates such as octadecyl carbitol (meth)acrylate. In this case, the number of repeating alkylene oxide units is preferably 1 to 8.

[0032] As the component (B-1), alkyl (meth)acrylates having a branched structure and 17 to 30 carbon atoms, such as isostearyl (meth)acrylate, are preferred.

[0033] Component (B-2) is a compound in which the ester residue has 5 to 30 carbon atoms, has an alicyclic hydrocarbon group and / or an aromatic hydrocarbon group, and has one (meth)acryloyl group. In component (B-2), the alicyclic hydrocarbon group having 5 to 30 carbon atoms includes a cyclic alkyl group and a cyclic alkenyl group. Examples of the alicyclic hydrocarbon group and aromatic hydrocarbon group include a (poly)alkylene oxide group having an alicyclic hydrocarbon group and a (poly)alkylene oxide group having an aromatic hydrocarbon group. The alicyclic hydrocarbon group and aromatic hydrocarbon group may be a functional group further having an alkyl group as part of the cyclic skeleton. Among the compounds having an alicyclic hydrocarbon group of component (B-2), examples of compounds having a cyclic alkyl group include (meth)acrylates having a cyclic alkyl group having 5 to 30 carbon atoms, such as cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and t-butylcyclohexyl (meth)acrylate. Examples of compounds having a cyclic alkenyl group include cyclohexenyl (meth)acrylate and dicyclopentenyl (meth)acrylate, etc. Examples of compounds having a cyclic alkyl group-containing (poly)alkylene oxide group include dicyclopentenyloxyethyl (meth)acrylate, etc.

[0034] Examples of the monofunctional (meth)acrylate having an aromatic hydrocarbon group of component (B-2) include aromatic monofunctional (meth)acrylates such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, o-phenylphenoxy (meth)acrylate, and p-cumylphenol ethylene (meth)acrylate. Examples of compounds having a (poly)alkylene oxide group with an alkyl group-containing aromatic group include (meth)acrylates of alkylphenol alkylene oxide adducts having an alkyl group having 4 to 20 carbon atoms, such as (meth)acrylate of nonylphenol ethylene oxide adduct and (meth)acrylate of nonylphenol propylene oxide adduct. In this case, the number of repeating alkylene oxide units is preferably 1 to 8.

[0035] The component (B) may contain, but preferably does not contain, a monofunctional (meth)acrylate other than the components (B-1) and (B-2) [hereinafter referred to as "component (B-3)"]. Examples of the component (B-3) include monofunctional (meth)acrylates having an alkyl group with 9 or less carbon atoms in the ester residue, such as n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, and n-octyl (meth)acrylate; monofunctional (meth)acrylates having an alkenyl group with 9 or less carbon atoms in the ester residue, such as pentenyl (meth)acrylate, butenyl (meth)acrylate, and hexenyl (meth)acrylate; monofunctional (meth)acrylates having a heterocyclic ring, such as tetrahydrofurfuryl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and the like. Examples of suitable (meth)acrylates include monofunctional (meth)acrylates having a hydroxyl group, such as 4-hydroxybutyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate; epoxy group-containing (meth)acrylates, such as glycidyl (meth)acrylate; monofunctional (meth)acrylates having a maleimide group, such as (meth)acrylolyloxyethylhexahydrophthalimide; and alkoxy group-containing monofunctional (meth)acrylates, such as 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, and 3-(meth)acryloxypropyltriethoxysilane.

[0036] The content of component (B) should be 20 to 90 wt%, preferably 40 to 90 wt%, and more preferably 50 to 85 wt%, based on 100 wt% of the total curable components. Furthermore, the content of component (B-1) should be 15 to 70 wt%, preferably 30 to 70 wt%, based on 100 wt% of the total curable components. If the content of component (B-1) is less than 15 wt%, the swelling ratio of the cured product after immersion in the electrolyte solution increases, resulting in a decrease in adhesive strength with the electrode foil after immersion in the electrolyte solution. On the other hand, if the content exceeds 70 wt%, the adhesive strength of the cured product decreases. Furthermore, the content of component (B-2) should be 5 to 50 wt%, preferably 10 to 40 wt%, based on 100 wt% of the total curable components. If the content of component (B-2) is less than 5 wt%, the swelling rate of the cured product after immersion in an electrolyte solution increases, resulting in a decrease in adhesive strength with the electrode foil after immersion in an electrolyte solution. On the other hand, if the content exceeds 70 wt%, the adhesive strength of the cured product decreases. It is preferable that component (B-3) is not included, and if it is included, it is preferably 8 wt% or less based on a total curable component amount of 100 wt%. By setting the content to 8 wt% or less, the swelling rate of the cured product after immersion in an electrolyte solution can be reduced.

[0037] 3. Component (C) The component (C) is a photoradical polymerization initiator that generates radicals upon irradiation with active energy rays and initiates polymerization of a compound having an ethylenically unsaturated group.

[0038] Specific examples of component (C) include benzil dimethyl ketal, benzil, benzoin, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, oligo[2-hydroxy-2-methyl-1-[4-1-(methylvinyl)phenyl]propanone, 2-hydroxy-1-[4 -[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl]-2-methylpropan-1-one, 2-methyl-1-[4-(methylthio)]phenyl]-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)butan-1-one, 2-dimethylamino-2-(4-methylbenzyl)-1-(4-morpholin-4-yl-phenyl)butan-1-one, 3,6-bis(2-methyl-2-morpholinopropionyl)-9-n-octylcarbazole, phenyl group aromatic ketone compounds such as methyl benzoate, ethyl anthraquinone, and phenanthrenequinone; benzophenone, 2-methylbenzophenone, 3-methylbenzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 4-(methylphenylthio)phenylphenylmethane, methyl-2-benzophenone, 1-[4-(4-benzoylphenylsulfanyl)phenyl]-2-methyl-2-(4-methylphenylsulfonyl)propan-1-one, 4,4'-bis(dimethylamino)phenyl; benzophenone compounds such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, ethyl(2,4,6-trimethylbenzoyl)phenylphosphinate and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide;Thioxanthone compounds such as thioxanthone, 2-chlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 1-chloro-4-propylthioxanthone, 3-[3,4-dimethyl-9-oxo-9H-thioxanthone-2-yl-oxy]-2-hydroxypropyl-N,N,N-trimethylammonium chloride, and fluorothioxanthone are also included;

[0039] The content of component (C) is 0.1 to 20 parts by weight, preferably 0.2 to 10 parts by weight, and more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the total curable components. If the content of component (C) is less than 0.1 part by weight, the photocurability of the composition will be reduced, and if it exceeds 20 parts by weight, the solvent resistance of the cured product after immersion in an electrolyte solution will be reduced.

[0040] 4. Other Components The composition of the present invention essentially contains the above components (A), (B), and (C), but can also contain various components commonly used in sealing materials. Examples include a compound having an ethylenically unsaturated group other than components (A) and (B) [hereinafter referred to as "component (D)"], a filler [hereinafter referred to as "component (E)"], a photoacid generator, a silane coupling agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a tackifier, a thiol compound, a plasticizer, a fluorescent agent, a coloring matter, a pigment, a dispersant, and / or an antistatic agent.

[0041] 1) Component (D) Component (D) is a compound having an ethylenically unsaturated group and is a compound other than components (A) and (B). Examples of the ethylenically unsaturated group in component (D) include a (meth)acryloyl group, a (meth)acrylamide group, a vinyl group, and an allyl group. Among these, a (meth)acryloyl group is preferred because of its excellent copolymerizability with other components.

[0042] As the component (D), various compounds can be used as long as they have an ethylenically unsaturated group, and examples thereof include compounds having two (meth)acryloyl groups in one molecule (hereinafter referred to as "bifunctional (meth)acrylates") and compounds having three or more (meth)acryloyl groups (hereinafter referred to as "trifunctional or higher functional (meth)acrylates").

[0043] Specific examples of the bifunctional (meth)acrylate include di(meth)acrylates having a divalent alkyl group, such as ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, tetramethylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, and nonanediol di(meth)acrylate; polyalkylene glycol di(meth)acrylates, such as polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, and polytetramethylene glycol di(meth)acrylate; di(meth)acrylates having an alicyclic group, such as tricyclodecanedimethylol di(meth)acrylate; di(meth)acrylates of alkylene oxide adducts of bisphenol A; and urethane di(meth)acrylate. Examples of the urethane di(meth)acrylate include urethane (meth)acrylates that do not have a polybutadiene and / or hydrogenated polybutadiene skeleton.

[0044] Specific examples of trifunctional or higher functional (meth)acrylates include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and tris(2-(meth)acryloyloxyethyl)isocyanurate.

[0045] The content of component (D) is preferably 8% by weight or less, and more preferably 0 to 5% by weight, based on 100% by weight of the curable component.

[0046] 2) Component (E) Component (E) is a filler. Preferred examples of component (E) include metal oxides such as silica and alumina, and polymer fine particles such as polyethylene fine particles, polypropylene fine particles, crosslinked acrylic fine particles, and crosslinked polystyrene fine particles. The particle size of the fine particles is preferably 0.1 to 200 μm, more preferably 1 to 100 μm. The incorporation of component (E) can reduce the moisture permeability and electrolyte permeability of the cured product. It can also improve screen printability. However, since too much filler can degrade printability, it is preferable to include it in a preferred content ratio. On the other hand, when applying by inkjet or spray, it is preferable to either not include component (E) or to limit its content to a very small amount. Based on the above, the preferred content ratio of component (E) is 0 to 60 wt% per 100 wt% of the composition.

[0047] 5. Photocurable Composition for Lithium-Ion Secondary Battery Sealing Material The present invention relates to a photocurable composition for lithium-ion secondary battery sealing material, containing the aforementioned components (A) to (C) in the aforementioned proportions. The content of the curable component in the composition is preferably 40 to 99.9 wt %, more preferably 50 to 99.5 wt %, based on 100 wt % of the composition. Furthermore, when component (E) is contained, the total content of the curable component and component (E) is preferably 80 to 99.9 wt %, more preferably 90 to 99.9 wt %, and even more preferably 95 to 99.9 wt % based on 100 wt % of the composition. The composition can be prepared by stirring and mixing the aforementioned components (A) to (C) and, if necessary, other components, according to conventional methods. Heating may be performed if necessary. The heating temperature may be appropriately set depending on the components used, the substrate, the purpose, etc., but is preferably 30 to 80°C. The viscosity of the composition may be adjusted depending on the coating method, but is preferably 10 to 100,000 mPa·s at 25°C, and more preferably 100 to 10,000 mPa·s.

[0048] 6. Method of Use The method of using the composition of the present invention may be a conventional method, and an example thereof includes a step of applying or injecting the composition of the present invention into a material constituting a lithium ion secondary battery, and a step of irradiating the applied or injected composition with light to cure it.

[0049] Materials constituting a lithium ion secondary battery include a current collector foil, a positive electrode active material, a negative electrode active material, a separator, and an electrolyte solution.

[0050] Examples of the current collector foil include aluminum and copper.

[0051] The active material may be appropriately selected depending on the type of battery. For example, examples of positive electrode active materials include lithium-transition metal composite oxides, lithium-transition metal phosphate compounds, and lithium-transition metal sulfate compounds. Examples of negative electrode active materials include metals such as Si and Sn; metal oxides such as TiO, TiO, TiO, SiO, SiO, and SnO; composite oxides of lithium and transition metals; Li-Pb alloys, Li-Al alloys; and carbon materials such as graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon.

[0052] Examples of the separator include microporous membrane films made of polyolefins such as polyethylene and polypropylene, multilayer films of porous polyethylene films and polypropylene, nonwoven fabrics made of polyester fibers, aramid fibers, glass fibers, etc., and those having ceramic fine particles such as silica, alumina, titania, etc. attached to the surface thereof.

[0053] Examples of the electrolyte include ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate, and a mixture of these may also be used.

[0054] The application and injection methods may be any conventionally known method, and examples thereof include methods using a dispenser, jet dispenser, screen printing, natural coater, knife belt coater, floating knife, knife over roll, knife on blanket, spray, dip, kiss roll, squeeze roll, reverse roll, air blade, curtain flow coater, comma coater, gravure coater, microgravure coater, die coater, and curtain coater.

[0055] Examples of light include visible light and ultraviolet light, but ultraviolet light is preferred because inexpensive equipment can be used. When curing with ultraviolet light, various light sources can be used, including pressurized or high-pressure mercury lamps, metal halide lamps, xenon lamps, electrodeless discharge lamps, carbon arc lamps, and LEDs. Among these, high-pressure mercury lamps, metal halide lamps, and LEDs are preferred. The irradiation dose of ultraviolet light is 50 to 5,000 mJ / cm in the UV-A region (near 365 nm). 2 It is preferable that the intensity is 100 to 3,000 mJ / cm 2 The illuminance of ultraviolet light is more preferably 10 to 5,000 mW / cm in the UV-A region (near 365 nm). 2 It is preferable that the intensity is 100 to 2,000 mW / cm 2 is more preferred.

[0056] Specific examples of how the composition of the present invention can be used are described below with reference to FIGS. 1 to 3. FIG. 1 is an example of a cross-sectional view of a bipolar lithium-ion secondary battery. In the configuration of FIG. 1, a positive electrode active material 12, a separator 13, and a negative electrode active material 14 are disposed in a space sandwiched between current collector foils 11. An electrolyte solution is present in the space between the positive electrode active material 12, the separator 13, and the negative electrode active material 14. To prevent leakage of this electrolyte solution, the outer periphery is sealed with a sealing member 15, which is a cured product of the composition. The composition of the present invention is particularly suitable as a sealing material for lithium-ion secondary batteries of this type. While FIG. 1 shows an example of two layers for ease of understanding, a structure with several tens of layers may actually be used.

[0057] Next, an example of a method for producing a lithium-ion secondary battery using the composition of the present invention will be described with reference to FIG. 2. FIG. 2 illustrates an example in which battery constituent materials are stacked, and then the composition of the present invention is applied from the side to fill the battery, followed by light irradiation from the side. FIG. 2(1) illustrates an example of a process in which battery constituent materials are stacked (21 in FIG. 2) and then the composition of the present invention is applied from the side to fill the battery. Specific examples of application methods include a dispenser, jet dispenser, inkjet, and spray. FIG. 2(1) illustrates an example using a dispenser 22. FIG. 2(2) illustrates a process in which the composition is applied and then cured by irradiating ultraviolet (UV) light from an ultraviolet irradiation device 23 from the side. In the above process, the electrolyte can be injected into the battery using a syringe or the like after the composition has hardened. The injection hole created when the syringe is inserted can be filled with the composition of the present invention again from above the hole using a dispenser or the like and then light-cured. This seals the injection hole. Alternatively, the composition may be applied to three of the four side surfaces and cured, leaving one side open, and the electrolyte may be poured through the open side. After pouring a predetermined amount of electrolyte, the composition may be applied to the last side and cured, thereby sealing all four sides.

[0058] Another example of a method for producing a lithium ion secondary battery using the composition of the present invention, but by a different method from the above, will be described with reference to FIG. 3 . FIG. 3 shows an example of a method for producing a lithium ion secondary battery by applying and curing a composition during the process of stacking battery constituent materials. First, as shown in 31, a current collector foil is prepared, with active material (positive electrode active material 12 or negative electrode active material 14) applied to the center portion of both sides. Next, as shown in 32, the composition (15') of the present invention is applied to its outer periphery. Screen printing or a dispenser is preferred as the application method. Next, as shown in 33, a separator 13 is placed over the foil, and as shown in 34, ultraviolet (UV) light is irradiated from above using an ultraviolet irradiation device 23. Separator 13 is often made of a polyolefin-based material, which is preferred because it transmits ultraviolet light. Next, as shown in 35, the composition (15') of the present invention is applied to the outer periphery, and as shown in 36, ultraviolet light is irradiated from above using an ultraviolet irradiation device 23 to cure the composition. Finally, as shown in 37, a current collector foil coated with an active material (positive electrode active material 12 or negative electrode active material 14) is laminated on the center of both sides. If the composition is adhesive, it can be bonded by applying pressure at room temperature. If it is not adhesive, it can be bonded by applying pressure using a press at approximately 60 to 100°C. Because the temperature is lower than that of heat-sealing sealants, wrinkles and warping due to thermal expansion can be suppressed. By repeating the above steps (31 to 37), a laminate such as that shown in FIG. 1 can be manufactured. The electrolyte can be injected in the same manner as described with reference to FIG. 2. Alternatively, ultraviolet light may be irradiated between 32 and 33, and the electrolyte may be injected before laminating separator 13 and before laminating electrode foil 37.

[0059] The present invention will be described in more detail below with reference to examples and comparative examples. In the following examples, "parts" means parts by weight and "%" means % by weight.

[0060] 1. Production Examples (Production of Urethane Acrylate) 1) Production Example 1 [Production of Bifunctional Urethane Acrylate Having a Hydrogenated Polybutadiene Skeleton] A 3-L four-neck separable flask was charged with 962 g (0.48 mol of hydroxyl groups) of GI-3000 (hydroxyl value 28.0 mg KOH / g, Mn approximately 4,000) hydrogenated polybutadiene having hydroxyl groups at both ends (manufactured by Nippon Soda Co., Ltd.), 0.75 g of 2,6-di-t-butyl-p-cresol, and 448 g of isobornyl acrylate (hereinafter referred to as "IBXA"), and the contents were dissolved by stirring using a stirrer. A thermometer, gas inlet tube, dropping funnel, and reflux condenser were attached to the flask, and the contents were stirred while bubbling a mixed gas of oxygen and nitrogen (5% oxygen) through the flask, and the temperature was then raised to 50°C. After adding 0.03 g of ferric acetylacetonate as a catalyst and dissolving it in this solution, 66.6 g of isophorone diisocyanate (0.60 mol as isocyanate groups) was added via a dropping funnel. After stirring and mixing at 80°C for 2 hours, 17.3 g of 4-hydroxybutyl acrylate (hereinafter referred to as "HBA") (0.12 mol as hydroxyl groups) was added and the reaction was allowed to proceed for 5 hours. The disappearance of the isocyanate groups was confirmed by IR spectroscopy, and the synthesis was terminated. The resulting product was a mixture containing 70% urethane acrylate having a hydrogenated polybutadiene skeleton (hereinafter referred to as "PUA-1") and 30% IBXA as a diluent monomer. GPC analysis of the resulting product confirmed that the peak of the PUA-1 component was distinct from the monomer components. The polystyrene-equivalent molecular weight of the PUA-1 component was 19,000 in Mn and 34,500 in Mw.

[0061] 2) Production Example 2 [Production of bifunctional urethane acrylate having a hydrogenated polybutadiene skeleton] Production Example 1 was repeated except that IBXA in Production Example 1 was replaced with isostearyl acrylate (hereinafter referred to as "ISTA"), to obtain a mixture containing 70% of PUA-1 and 30% of ISTA.

[0062] 3) Production Example 3 [Production of a bifunctional acrylate obtained by directly acrylating hydrogenated polybutadiene having hydroxyl groups at both ends] A 3-L separable flask was charged with 571.9 g (0.70 mol of hydroxyl groups) of GI-1000 (hydroxyl value 68.7 mg KOH / g, Mn approximately 1,600) hydrogenated polybutadiene having hydroxyl groups at both ends (manufactured by Nippon Soda Co., Ltd.), 60.5 g of acrylic acid, 632.4 g of heptane, and 12.6 g of p-toluenesulfonic acid monohydrate. The flask was equipped with a thermometer, a gas inlet tube, a dropping funnel, and a reflux condenser. The mixture was stirred while blowing in a mixed gas of oxygen and nitrogen (5% oxygen), and then refluxed in an oil bath at 120 °C for 2 hours. The solution was transferred to a separatory funnel and washed three times with pure water. 0.012 g of 4-methoxyphenol was added as a polymerization inhibitor, and the mixture was stirred at 80°C while blowing in dry air, followed by gradual distillation under reduced pressure. The oil bath was heated to 85°C, and the mixture was stirred under reduced pressure at 10 Torr until no more bubbles were generated from the solution, synthesizing a bifunctional acrylate (hereinafter referred to as GI-AA) in which hydrogenated polybutadiene having hydroxyl groups at both ends was directly acrylated. The molecular weight of GI-AA was Mn 3,000 and Mw 4,200.

[0063] 2. Examples 1 to 7, Comparative Examples 1 to 101) Production of photocurable compositions for lithium ion secondary battery sealing materials The components shown in Tables 1 and 2 below were blended in the proportions shown in Tables 1 and 2, and the mixture was stirred and mixed in a conventional manner to obtain photocurable compositions for lithium ion secondary battery sealing materials. In producing the compositions, the compositions were heated to about 80°C as necessary.

[0064]

[0065]

[0066] The number of parts of PUA-1 in the table indicates the number of parts of only the urethane acrylate component contained in the product of Production Example 1 or Production Example 2. The number of parts of component (B) includes the component (B) contained in the product of Production Example 1, and indicates the total number of parts of component (B) contained in the product of Production Example 1 and the component (B) added later.

[0067] The numbers in Tables 1 and 2 indicate the number of parts. The abbreviations in Tables 1 and 2 have the following meanings. ◆ Component (A) PUA-1: Bifunctional urethane acrylate having a hydrogenated polybutadiene skeleton. The urethane acrylate component contained in the products of Production Examples 1 and 2. TEAI: Bifunctional urethane acrylate having a hydrogenated polybutadiene skeleton (TEAI-1000 manufactured by Nippon Soda Co., Ltd.) (Mn: 3,200, Mw: 6,100) GI-AA: Bifunctional acrylate obtained by directly acrylate of hydrogenated polybutadiene having hydroxyl groups at both ends. The product of Production Example 3.

[0068] ◆ Component (B-1) LA: Lauryl acrylate (LA manufactured by Osaka Organic Chemical Industry Ltd.) ISTA: Isostearyl acrylate (ISTA manufactured by Osaka Organic Chemical Industry Ltd.) STA: Stearyl acrylate (STA manufactured by Osaka Organic Chemical Industry Ltd.) ◆ Component (B-2) IBXA: Isobornyl acrylate (IBXA manufactured by Osaka Organic Chemical Industry Ltd.) FA-513: Dicyclopentanyl acrylate (Fancryl FA-513AS manufactured by Showa Denko Materials K.K.) M-111: Acrylate of ethylene oxide 1 mole adduct of nonylphenol. Aronix M-111 manufactured by Toagosei Co., Ltd. ◆ Component (B-3) HBA: 4-hydroxybutyl acrylate (HBA manufactured by Osaka Organic Chemical Industry Ltd.)

[0069] ◆Component (C) ONE: α-hydroxyalkylphenone photopolymerization initiator (ESACURE ONE manufactured by IGM Resins) O-184: 1-hydroxycyclohexylphenyl ketone (Omnirad 184 manufactured by IGM Resins) O-651: 2,2-dimethoxy-1,2-diphenylethan-1-one (Omnirad 651 manufactured by IGM Resins)

[0070] ◆Component (D) HX-A: 1,6-hexanediol diacrylate (Light Acrylate HX-A, manufactured by Kyoeisha Chemical Co., Ltd.) NP-A: Neopentyl glycol diacrylate (Light Acrylate NP-A, manufactured by Kyoeisha Chemical Co., Ltd.) UN-9200A: Bifunctional urethane acrylate having a polycarbonate skeleton and not having a polybutadiene or hydrogenated polybutadiene skeleton (Art Resin UN-9200A, manufactured by Negami Chemical Industrial Co., Ltd.) UN-6301: Bifunctional urethane acrylate having a polyether skeleton urethane acrylate and not having a polybutadiene or hydrogenated polybutadiene skeleton (Art Resin UN-6301, manufactured by Negami Chemical Industrial Co., Ltd.) UC-203: Ester of maleic anhydride adduct of polyisoprene and 2-hydroxyethyl acrylate (UC-203, manufactured by Kuraray Co., Ltd.)

[0071] 2) Evaluation of Compositions The compositions obtained above were evaluated for initial peel strength, peel strength after immersion in an electrolyte solvent, and swelling after immersion in an electrolyte solvent according to the following methods. The results are shown in Tables 1 and 2.

[0072] (1) Initial peel strength The composition obtained above was poured into a 0.5 mm thick silicone mold placed on metal foil (25 μm thick aluminum foil manufactured by UACJ Foil Corporation and 35 μm thick low-roughness rolled copper foil manufactured by Fukuda Metal Foil and Powder Co., Ltd.), and then laminated with an easy-to-adhere PET film (Lumirror A4360 manufactured by Toray Industries, Inc.) as a substrate that adheres more strongly than the metal foil, followed by photo-curing. The curing conditions were a 365 nm LED (surface-type LED irradiator manufactured by CCS Corporation) with an illuminance of 1000 mW / cm. 2 The PET film side was irradiated with 1000 kJ / cm² of illuminance (measured with a Hamamatsu Photonics C12684 illuminance meter) for 5 seconds. The cured sample was cut into a 10 mm wide strip, the PET film side attached to a metal plate with double-sided tape, the metal foil was bent 180° and slightly peeled off, and the 180° peel strength was measured using an Instron 5564 (Instron Japan Co., Ltd.). The tensile speed was 60 mm / s. Measurement results of 1 N / cm or less were rated as ×, 1 N / cm to 5 N / cm as ◯, and 5 N / cm or more as ⊚.

[0073] (2) Peel strength after immersion in electrolyte solvent: A 10 mm wide strip of cured material was prepared using the same method as in (1) and immersed in a sufficient amount of EC / DEC = 3 / 7 (weight ratio). Note that "EC" means ethylene carbonate, and "DEC" means diethyl carbonate. After standing at 23°C for 24 hours, the cured material was removed and the droplets on the surface were removed, and the peel strength was immediately measured in the same manner as in (1). A measurement result of 1 N / cm or less was evaluated as ×, 1 N / cm to 5 N / cm was evaluated as ◯, and 5 N / cm or more was evaluated as ◎.

[0074] (3) Swelling rate after immersion in electrolyte solvent The composition obtained above was poured into a 1 mm thick silicone mold cut to an arbitrary size, and then laminated with a 75 μm thick silicone-treated release PET film (HTA manufactured by Fujimori Kogyo Co., Ltd.) to eliminate polymerization inhibition due to oxygen, followed by photo-curing. The curing conditions were a 365 nm LED (a surface-type LED irradiator manufactured by CCS Corporation) with an illuminance of 1000 mW / cm. 2 (Measured using a Hamamatsu Photonics C12684 illuminance meter) for 5 seconds each from both sides. The PET film was then peeled off to obtain a cured product. The initial weight of the cured product was measured to four decimal places, and then immersed in a sufficient amount of EC / DEC = 3 / 7 (weight ratio). After leaving it at 23°C for 24 hours, the cured product was removed, and the droplets on the surface were removed and immediately weighed. The weight increase after immersion relative to the initial weight was evaluated as the swelling ratio. A swelling ratio of less than 30% was evaluated as ⊚, 30-50% as ◯, and 50% or more as ×.

[0075] 3) Evaluation Results As is clear from the results in Table 1, all of the compositions of the present invention exhibited excellent initial peel strength and peel strength after immersion in an electrolyte solvent against aluminum and copper, and further exhibited small swelling ratios after immersion in an electrolyte solvent. In contrast, as is clear from the results in Table 2, the comparative compositions not containing the (B-1) component exhibited the following results. The composition of Comparative Example 1 exhibited a significant decrease in initial peel strength against aluminum and peel strength after immersion in an electrolyte solvent. The composition of Comparative Example 5 exhibited a significant decrease in initial peel strength against aluminum and copper and peel strength after immersion in an electrolyte solvent. The composition of Comparative Example 6 exhibited no problems with initial peel strength against aluminum and copper, but exhibited a significant decrease in peel strength after immersion in an electrolyte solvent and a large swelling ratio after immersion in an electrolyte solvent. The compositions of Comparative Examples 2 to 4 not containing the (B-2) component exhibited a significant decrease in initial peel strength against aluminum and copper and peel strength after immersion in an electrolyte solvent. The comparative compositions not containing the (A) component exhibited the following results. The compositions of Comparative Examples 7 and 8 exhibited a slight decrease in initial peel strength to aluminum and copper, a significant decrease in peel strength after immersion in an electrolyte solvent, and a large swelling ratio after immersion in an electrolyte solvent. The composition of Comparative Example 9 exhibited a significant decrease in initial peel strength to aluminum and copper and peel strength after immersion in an electrolyte solvent. The composition of Comparative Example 10 exhibited no problems with the initial peel strength to aluminum and copper, but a significant decrease in peel strength after immersion in an electrolyte solvent.

[0076] The present invention relates to a photocurable composition for a sealing material for lithium ion secondary batteries, which can be preferably used in the production of lithium ion secondary batteries.

[0077] REFERENCE SIGNS LIST 11 Current collector foil 12 Positive electrode active material 13 Separator 14 Negative electrode active material 21 Battery constituent material 22 Dispenser 23 Ultraviolet irradiation device

Claims

1. Component (A): A compound having a skeleton of polybutadiene and / or hydrogenated polybutadiene in one molecule and having two (meth)acryloyl groups with a number-average molecular weight of 1000 or more Component (B): A compound having one (meth)acryloyl group in one molecule containing the following component (B-1) and component (B-2) as essential components (hereinafter referred to as "monofunctional (meth)acrylate") - Component (B-1): A monofunctional (meth)acrylate having an alkyl group or alkenyl group with 10 to 30 carbon atoms in the ester residue - Component (B-2): A monofunctional (meth)acrylate having 5 to 30 carbon atoms in the ester residue and having an alicyclic hydrocarbon group and / or an aromatic hydrocarbon group Component (C): A photo radical polymerization initiator containing in a total of 100% by weight of the curable components, component (A) is contained in an amount of 10 to 80% by weight, and component (B) is contained in an amount of 20% by weight to 90% by weight component (B-1) is contained in an amount of 15 to 70% by weight based on 100% by weight of the total curable components, and component (B-2) is contained in an amount of 5 to 50% by weight based on 100% by weight of the total curable components component (C) is contained in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the total curable components A photocurable composition for a lithium-ion secondary battery sealing material

2. The photocurable composition for a lithium-ion secondary battery sealing material according to claim 1, wherein the component (A) is a urethane (meth)acrylate having a number-average molecular weight of 5,000 to 50,000

3. The photocurable composition for a lithium-ion secondary battery sealing material according to claim 1, wherein the component (B-1) contains an alkyl (meth)acrylate having 17 to 30 carbon atoms and having a branched structure

4. A method for manufacturing a lithium-ion secondary battery, wherein the photocurable composition for a lithium-ion secondary battery sealing material according to any one of claims 1 to 3 is applied or injected onto the side surface of a constituent material of the lithium-ion secondary battery, and then the coated surface or the injected surface is irradiated with light

5. A lithium-ion secondary battery, wherein the side surface of a constituent material of the lithium-ion secondary battery is sealed with a cured product of the photocurable composition for a lithium-ion secondary battery sealing material according to any one of claims 1 to 3