JP7105153B2 - Adhesive sheets for batteries and lithium-ion batteries - Google Patents

Description

TECHNICAL FIELD The present invention relates to a battery pressure-sensitive adhesive sheet and a lithium ion battery manufactured using the battery pressure-sensitive adhesive sheet.

In some batteries, a strip-shaped laminate formed by laminating a positive electrode, a negative electrode, and a separator positioned therebetween is rolled up and housed inside. Electrode extraction tabs made of conductors are connected to the positive electrode and the negative electrode, respectively. Through these electrode extraction tabs, the positive electrode and the negative electrode are electrically connected to the positive electrode terminal and the negative electrode terminal of the battery, respectively. .

An adhesive sheet may be used for winding the laminate and fixing the electrode extraction tab to the electrode. As such an adhesive sheet, one comprising a substrate and an adhesive layer provided on one surface of the substrate is usually used. In addition, from the viewpoint of improving desired performance such as insulation, an insulating material or the like is contained on the surface of the base material opposite to the pressure-sensitive adhesive layer or between the base material and the pressure-sensitive adhesive layer. A pressure-sensitive adhesive sheet provided with an insulating layer is sometimes used.

However, providing the insulating layer as described above separately from the adhesive layer causes an increase in manufacturing cost. Therefore, attempts have been made to improve the insulating properties of the adhesive sheet by including an insulating material or the like in the adhesive layer without providing the insulating layer as described above. For example, Patent Literature 1 discloses a pressure-sensitive adhesive sheet in which the pressure-sensitive adhesive layer contains alumina. Further, Patent Document 2 discloses a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer contains magnesium hydroxide, alumina, magnesium oxide, aluminum hydroxide, silica, boron nitride, titanium oxide, or magnesium carbonate.

WO2017/038010 JP 2017-152372 A

By the way, the adhesive sheet used for winding the laminate and fixing the electrode extraction tab to the electrode inside the battery should exhibit good adhesive strength from the viewpoint of the battery exhibiting the desired performance. is important. In particular, such an adhesive sheet may come into contact with the electrolytic solution filled inside the battery, and even in such cases, it is required to maintain sufficient adhesive strength. However, the pressure-sensitive adhesive sheets provided with a pressure-sensitive adhesive layer containing an insulating material or the like, as disclosed in Patent Documents 1 and 2, could not exhibit sufficient adhesive force.

Further, in recent years, pressure-sensitive adhesive sheets used in batteries are required to have higher insulating properties from the viewpoint of enhancing the safety of the batteries. In particular, even if an internal short circuit occurs due to the inclusion of foreign matter in the battery, etc., there is a demand for high insulation that can suppress heat generation due to the internal short circuit.

The present invention has been made in view of such circumstances, and provides a battery adhesive sheet that can exhibit excellent adhesive strength and has high insulating properties, and a lithium ion battery using such a battery adhesive sheet. intended to

In order to achieve the above object, firstly, the present invention provides a substrate, a first pressure-sensitive adhesive layer containing inorganic fine particles provided on one side of the substrate, and the first pressure-sensitive adhesive Provided is a pressure-sensitive adhesive sheet for a battery, comprising: a second pressure-sensitive adhesive layer that does not contain the inorganic fine particles and is provided on the side of the layer opposite to the base material (Invention 1).

The battery pressure-sensitive adhesive sheet according to the above invention (Invention 1) comprises a first pressure-sensitive adhesive layer containing inorganic fine particles and a second pressure-sensitive adhesive layer containing no inorganic fine particles, The first adhesive layer and the second adhesive layer are arranged so that the adhesive layers are in contact with each other, thereby achieving both good adhesion to the adherend and high insulation. can be done.

In the above invention (Invention 1), the content of the inorganic fine particles in the first pressure-sensitive adhesive layer is 50 parts by mass or more to 1000 parts by mass with respect to 100 parts by mass of the adhesive component contained in the first pressure-sensitive adhesive layer. It is preferably at most parts by mass (Invention 2).

In the above inventions (inventions 1 and 2), the thickness of the first adhesive layer is preferably 1 μm or more and 50 μm or less (invention 3).

In the above inventions (inventions 1 to 3), it is preferable that the thickness of the second adhesive layer is 1 μm or more and 50 μm or less (invention 4).

In the above inventions (inventions 1 to 4), it is preferable that the adhesive force of the battery adhesive sheet to the aluminum plate is 0.5 N/25 mm or more and 50 N/25 mm or less (invention 5).

The second aspect of the present invention is a lithium battery, wherein two or more conductors are fixed in contact with each other using the battery adhesive sheet (inventions 1 to 5) inside the battery. An ion battery is provided (Invention 6).

The pressure-sensitive adhesive sheet for batteries according to the present invention exhibits excellent adhesive strength and has high insulating properties. Therefore, a lithium-ion battery manufactured using the pressure-sensitive adhesive sheet for battery can exhibit excellent performance.

1 is a cross-sectional view of a battery adhesive sheet according to an embodiment of the present invention; FIG. 1 is a partial cross-sectional exploded perspective view of a lithium-ion battery according to one embodiment of the present invention; FIG. 1 is an exploded perspective view of an electrode assembly of a lithium ion battery according to one embodiment of the present invention; FIG.

Embodiments of the present invention will be described below.
[Adhesive sheet for batteries]
As shown in FIG. 1, a battery adhesive sheet 1 according to an embodiment of the present invention includes a substrate 11, a first adhesive layer 12 provided on one side of the substrate 11, and a first The second adhesive layer 13 provided on the surface side opposite to the substrate 11 in the adhesive layer 12, and the release provided on the surface side opposite to the substrate 11 in the second adhesive layer 13 and a seat 14 . Moreover, in the battery adhesive sheet 1 according to this embodiment, the first adhesive layer 12 contains the inorganic fine particles 121 . On the other hand, the second adhesive layer 13 does not contain the inorganic fine particles 121 .

Here, the "battery pressure-sensitive adhesive sheet" in the present specification is a pressure-sensitive adhesive sheet that is used in locations where there is a possibility of contact with the electrolytic solution in the production of the battery, preferably the pressure-sensitive adhesive sheet that is used inside the battery. and may be a pressure-sensitive adhesive sheet for battery interior. The battery is preferably a non-aqueous battery. Therefore, the electrolyte used in the battery is preferably a non-aqueous electrolyte. The battery pressure-sensitive adhesive sheet in the present specification is preferably a pressure-sensitive adhesive sheet that is attached to a portion of the interior of a non-aqueous battery that may be immersed in the electrolytic solution or a portion that may come into contact with the electrolytic solution. Lithium ion batteries are particularly preferred as non-aqueous batteries.

In the battery adhesive sheet 1 according to the present embodiment, the first adhesive layer 12 functions as an insulating layer because the first adhesive layer 12 contains the inorganic fine particles 121 . Therefore, the battery pressure-sensitive adhesive sheet 1 according to the present embodiment has excellent insulating properties under normal conditions. In addition, since the battery pressure-sensitive adhesive sheet 1 according to the present embodiment is provided with the first pressure-sensitive adhesive layer 12, even if an internal short circuit occurs in a battery in which the battery pressure-sensitive adhesive sheet 1 is used, heat is generated. quantity can be kept low. Furthermore, since the battery pressure-sensitive adhesive sheet 1 according to the present embodiment includes the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13, the total thickness of the pressure-sensitive adhesive layer can be increased. It can be excellent in adhesive strength.

Further, in the battery adhesive sheet 1 according to the present embodiment, the second adhesive layer 13 that does not contain the inorganic fine particles 121 is located at a position where the second adhesive layer 13 is in contact with the adherend when the battery adhesive sheet 1 is attached to the adherend. By being arranged in, excellent adhesive strength can be exhibited. In particular, since the second adhesive layer 13 does not contain the inorganic fine particles 121, there is no decrease in adhesive strength due to the presence of the inorganic fine particles 121, so that the battery adhesive sheet 1 has excellent adhesive strength. will be demonstrated. Therefore, according to the battery pressure-sensitive adhesive sheet 1 according to the present embodiment, it is possible to suppress the occurrence of battery problems caused by the peeling of the pressure-sensitive adhesive sheet inside the battery.

As described above, the battery pressure-sensitive adhesive sheet 1 according to the present embodiment includes the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13, thereby achieving excellent adhesive strength, which has been difficult to achieve in the past. and high insulation can be satisfactorily compatible. Therefore, by using the battery adhesive sheet 1 according to the present embodiment, a highly safe battery can be manufactured.

1. Each component 1-1. Substrate In the battery adhesive sheet 1 according to the present embodiment, the substrate 11 preferably has a high minimum voltage at which dielectric breakdown occurs. It is preferably 5 kV or higher. When the voltage is 1 kV or more, dielectric breakdown of the base material 11 is less likely to occur, and the reliability of the battery adhesive sheet 1 becomes higher.

Further, it is preferable that the base material 11 has flame retardancy that satisfies the flame retardancy level V-0 of the UL94 standard. Since the base material 11 has such flame retardancy, the base material 11 is prevented from being degenerated or deformed even when the base material 11 generates heat due to normal use of the battery. Moreover, even if a problem occurs in the battery and excessive heat is generated, ignition and combustion of the base material 11 are suppressed, and a serious accident is prevented.

The material of the base material 11 can be appropriately selected from the viewpoint of insulation, flame resistance, heat resistance, reactivity with the electrolyte, permeability of the electrolyte, and the like. In particular, it is preferable to use a resin film as the substrate 11 . Examples of resin films include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin films such as polyethylene films and polypropylene films; Coalescent film, cellophane, diacetylcellulose film, triacetylcellulose film, acetylcellulose butyrate film, polyvinyl chloride film, polyvinylidene chloride film, polyvinyl alcohol film, ethylene-vinyl acetate copolymer film, polystyrene film, polycarbonate film , polymethylpentene film, polysulfone film, polyetheretherketone film, polyethersulfone film, polyetherimide film, fluorine resin film, acrylic resin film, polyurethane resin film, norbornene polymer film, cyclic olefin polymer film , a cyclic conjugated diene polymer film, a vinyl alicyclic hydrocarbon polymer film, or a laminate film thereof. In particular, from the viewpoint of insulation and flame retardancy, a film of a polymer containing nitrogen in the main chain (which may contain components other than the polymer; the same shall apply in this specification) is preferable, particularly the main chain. A polymer film having a nitrogen-containing ring structure in the main chain is preferable, and a polymer film having a nitrogen-containing ring structure and an aromatic ring structure in the main chain is more preferable. Specifically, for example, a polyimide film, a polyetherimide film or a polyetheretherketone film is preferable, and among these, a polyimide film which is particularly excellent in insulating properties and flame retardancy is preferable.

The lower limit of the thickness of the base material 11 is preferably 5 μm or more, particularly preferably 10 μm or more, further preferably 15 μm or more. Since the lower limit value of the thickness of the base material 11 is the above, for example, an electrode body having an electrode extraction tab fixed by the battery adhesive sheet 1 is wound up, and a winding pressure is applied to the battery adhesive sheet 1. Even in this case, breakage of the base material 11 can be effectively suppressed. The upper limit of the thickness of the base material 11 is preferably 200 μm or less, particularly preferably 100 μm or less, further preferably 40 μm or less. By setting the upper limit of the thickness of the base material 11 to the above range, the pressure-sensitive adhesive sheet for battery 1 has an appropriate degree of flexibility, and can be applied to a surface having a step as in the case of fixing an electrode and an electrode extraction tab. Even when the adhesive sheet for battery 1 is attached, it can follow the steps satisfactorily.

1-2. First Adhesive Layer (1) Inorganic Fine Particles The first adhesive layer 12 contains an adhesive component and inorganic fine particles 121 . The inorganic fine particles 121 are not limited as long as they can impart desired insulating properties to the first adhesive layer 12, and examples thereof include alumina, titania, calcium carbonate, silica, boehmite, talc, iron oxide, and silicon carbide. , powders of boron nitride, barium sulfate, zirconium oxide, etc., beads obtained by spheroidizing these powders, single crystal fibers, glass fibers, and the like can be used. These may be used alone or in combination of two or more. Among these, it is preferable to use at least one of alumina, titania and calcium carbonate from the viewpoint of easily achieving high insulation.

The average particle diameter of the inorganic fine particles 121 is preferably 0.01 μm or more, particularly preferably 0.1 μm or more, and further preferably 0.2 μm or more. When the average particle size of the inorganic fine particles 121 is 0.01 μm or more, the battery pressure-sensitive adhesive sheet 1 according to the present embodiment can easily exhibit high insulating properties. Also, the average particle size of the inorganic fine particles 121 is preferably 10 μm or less, particularly preferably 5 μm or less, and further preferably 1.4 μm or less. When the average particle size of the inorganic fine particles 121 is 10 μm or less, the dispersibility of the inorganic fine particles 121 becomes more excellent, and when the first adhesive layer 12 is formed on the base material 11, the first adhesive It is possible to effectively prevent unevenness from occurring on the surface of the agent layer 12 opposite to the substrate 11 . Furthermore, by forming the second pressure-sensitive adhesive layer 13 on the surface, the surface of the second pressure-sensitive adhesive layer 13 opposite to the first pressure-sensitive adhesive layer 12 can have very high smoothness. can. As a result, the second pressure-sensitive adhesive layer 13 exhibits excellent adhesion to the adherend. Note that the average particle size of the inorganic fine particles 121 is measured by a laser diffraction/scattering method.

The content of the inorganic fine particles 121 in the first adhesive layer 12 is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, with respect to 100 parts by mass of the adhesive component contained in the first adhesive layer 12. It is more preferably 150 parts by mass or more, and more preferably 200 parts by mass or more. When the content is 50 parts by mass or more, the battery pressure-sensitive adhesive sheet 1 according to the present embodiment can easily exhibit high insulating properties. In addition, the content of the inorganic fine particles 121 in the first adhesive layer 12 is preferably 1000 parts by mass or less, particularly 600 parts by mass, with respect to 100 parts by mass of the adhesive component contained in the first adhesive layer 12. It is preferably not more than 400 parts by mass, more preferably not more than 400 parts by mass. When the content is 1000 parts by mass or less, excellent adhesion between the substrate 11 and the first pressure-sensitive adhesive layer 12 and between the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 It becomes easy to achieve the properties, and delamination can be effectively suppressed.

(2) Adhesive Component The adhesive component contained in the first adhesive layer 12 is not particularly limited, and can be appropriately selected from the viewpoint of elution into the electrolyte, flame resistance, heat resistance, insulation, and the like. In particular, as the adhesive component, it is preferable to use at least one of an acrylic adhesive component, a silicone adhesive component, a rubber adhesive component and a urethane adhesive component. The adhesive component contained in the first adhesive layer 12 may be emulsion type, solvent type or non-solvent type, and may be crosslinked or non-crosslinked. Among the above, an acrylic adhesive component is preferable from the viewpoint of adhesion to the base material 11 and the second adhesive layer 13, ease of delicate adjustment of adhesive force, etc., and a cross-linking type acrylic adhesive component is particularly preferable. Preferred are solvent-based cross-linking acrylic pressure-sensitive adhesive components.

It is preferable that the acrylic adhesive component described above comprises the (meth)acrylic acid ester polymer (A) and the cross-linking agent (B). In this case, the first adhesive layer 12 contains an acrylic adhesive component composed of the (meth)acrylic acid ester polymer (A) and the cross-linking agent (B), and the inorganic fine particles 121 . Such a first pressure-sensitive adhesive layer 12 is a first pressure-sensitive adhesive layer adhesive composition (hereinafter " It may be referred to as "adhesive composition P1".).

In addition, in this specification, (meth)acrylic acid ester means both acrylic acid ester and methacrylic acid ester. The same applies to other similar terms. In addition, the concept of "copolymer" is also included in "polymer".

(2-1) (Meth) acrylic acid ester polymer (A)
The (meth)acrylic acid ester polymer (A) is used from the viewpoint that the first adhesive layer 12 tends to have high adhesion to both the base material 11 and the second adhesive layer 13. , As a monomer unit constituting the polymer, it is preferable to contain a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 10 carbon atoms. Examples of such (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, and (meth)acrylic acid. Examples include n-pentyl, n-hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate and n-decyl (meth)acrylate. Among these, alkyl acrylates having 3 to 9 carbon atoms in the alkyl group are preferred, and alkyl acrylates having 5 to 8 carbon atoms in the alkyl group are particularly preferred. These may be used alone or in combination of two or more.

The (meth)acrylic acid ester polymer (A) preferably contains 50% by mass or more of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 10 carbon atoms as a monomer unit constituting the polymer. , In particular, it is preferably contained in an amount of 60% by mass or more, more preferably 70% by mass or more. By containing 50% by mass or more of the (meth)acrylic acid alkyl ester, the adhesion between the base material 11 and the first adhesive layer 12 and the adhesion between the first adhesive layer 12 and the second adhesive layer 13 The adhesion of is further improved. In addition, the (meth)acrylic acid ester polymer (A) contains 99% by mass or less of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 10 carbon atoms as a monomer unit constituting the polymer. is preferred, particularly preferably 95% by mass or less, and more preferably 90% by mass or less. By controlling the (meth)acrylic acid alkyl ester to 99% by mass or less, a suitable amount of other monomer components can be introduced into the (meth)acrylic acid ester polymer (A).

In addition, the (meth)acrylic acid ester polymer (A) has an alkyl It preferably contains a (meth)acrylic acid alkyl ester having a group having 11 to 20 carbon atoms. Examples of such (meth)acrylic acid alkyl esters include n-lauryl (meth)acrylate, myristyl (meth)acrylate, palmityl (meth)acrylate, and stearyl (meth)acrylate. Among these, (meth)acrylic acid alkyl esters in which the alkyl group has 12 to 18 carbon atoms are preferred. These may be used alone or in combination of two or more.

The (meth)acrylic acid ester polymer (A) preferably contains 1% by mass or more of a (meth)acrylic acid alkyl ester having an alkyl group having 11 to 20 carbon atoms as a monomer unit constituting the polymer. , more preferably 5% by mass or more, and particularly preferably 10% by mass or more. By containing 1% by mass or more, the first pressure-sensitive adhesive layer 12 to be obtained has higher hydrophobicity, thereby making it easier to achieve excellent electrolytic solution resistance. On the other hand, the (meth)acrylic acid ester polymer (A) contains 40% by mass or less of a (meth)acrylic acid alkyl ester having an alkyl group having 11 to 20 carbon atoms as a monomer unit constituting the polymer. is preferable, it is more preferable to contain 30% by mass or less, and it is particularly preferable to contain 20% by mass or less. By containing 40% by mass or less of the (meth)acrylic acid alkyl ester, it becomes easy to introduce a suitable amount of other monomer components into the (meth)acrylic acid ester polymer (A).

The (meth)acrylic acid ester polymer (A) may optionally contain monomers other than those described above as monomer units constituting the polymer. The monomer may be a monomer containing a reactive functional group or a monomer containing no reactive functional group.

Examples of monomers containing reactive functional groups (monomers containing reactive functional groups) include monomers having a carboxy group in the molecule (carboxy group-containing monomers), monomers having a hydroxyl group in the molecule (hydroxyl group-containing monomers), intramolecular and a monomer having an amino group (amino group-containing monomer). Among these, the (meth)acrylic acid ester polymer (A) preferably contains a hydroxyl group-containing monomer or a carboxy group-containing monomer as a monomer unit constituting the polymer, and particularly preferably contains a carboxy group-containing monomer. preferable. By containing the carboxy group-containing monomer, the polarity of the formed first pressure-sensitive adhesive layer 12 increases, and the elution resistance to the electrolytic solution becomes more excellent.

Carboxy group-containing monomers include, for example, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid, and citraconic acid. Among these, acrylic acid is preferred. According to acrylic acid, the above effects are more excellent. The above carboxy group-containing monomers may be used alone, or two or more of them may be used in combination.

Examples of hydroxyl group-containing monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, (meth) ) hydroxyalkyl (meth)acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth)acrylate; These may be used alone or in combination of two or more.

Examples of amino group-containing monomers include aminoethyl (meth)acrylate and n-butylaminoethyl (meth)acrylate. These may be used alone or in combination of two or more.

The (meth)acrylic acid ester polymer (A) preferably contains 0.5% by mass or more, particularly 1% by mass or more, of a reactive functional group-containing monomer as a monomer unit constituting the polymer. is preferable, and more preferably 3% by mass or more. Further, the (meth)acrylic acid ester polymer (A) preferably contains 30% by mass or less, particularly 20% by mass or less, of a reactive functional group-containing monomer as a monomer unit constituting the polymer. is preferred, and it is more preferred to contain 9% by mass or less. When the (meth)acrylic acid ester polymer (A) contains the reactive functional group-containing monomer in the above amount as a monomer unit, a crosslinked structure is favorably formed by the reaction with the crosslinking agent (B). The cohesive force of the first pressure-sensitive adhesive layer 12 is moderately increased, and thereby the elution resistance to the electrolytic solution is further improved.

On the other hand, examples of monomers not containing a reactive functional group include (meth)acrylate alkoxyalkyl esters such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate, (meth)acrylic acid N, N-dimethylaminoethyl, N,N-dimethylaminopropyl (meth)acrylate, (meth)acrylic acid ester having a non-crosslinkable tertiary amino group such as (meth)acryloylmorpholine, (meth)acrylamide, dimethylacrylamide , vinyl acetate, styrene, and the like. These may be used alone or in combination of two or more.

The (meth)acrylate polymer (A) may be solution-polymerized, solvent-free, or emulsion-polymerized. Among them, a solution polymer obtained by a solution polymerization method is preferable. By being a solution polymer, it is easy to obtain a linear high-molecular-weight polymer, and it is easy to make the first pressure-sensitive adhesive layer 12 more excellent in electrolyte resistance.

The polymerization mode of the (meth)acrylic acid ester polymer (A) may be a random copolymer or a block copolymer.

The weight-average molecular weight of the (meth)acrylate polymer (A) is preferably 50,000 or more, more preferably 100,000 or more, particularly preferably 200,000 or more, as a lower limit. is preferably 500,000 or more. When the lower limit of the weight-average molecular weight of the (meth)acrylic acid ester polymer (A) is above, the elution resistance of the formed first pressure-sensitive adhesive layer 12 to the electrolytic solution is more excellent.

The upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is preferably 2,500,000 or less, more preferably 2,000,000 or less, and particularly preferably 1,200,000 or less. , and more preferably 950,000 or less. When the upper limit of the weight average molecular weight of the (meth)acrylic acid ester polymer (A) is the above, the adhesion between the first adhesive layer 12 and the base material 11 and the first adhesive layer 12 and the second adhesive layer 12 The adhesiveness with the pressure-sensitive adhesive layer 13 is more excellent. In addition, the weight average molecular weight in this specification is the value of standard polystyrene conversion measured by the gel permeation chromatography (GPC) method.

In addition, in the adhesive composition P1, the (meth)acrylic acid ester polymer (A) may be used alone or in combination of two or more.

(2-2) Crosslinking agent (B)
The cross-linking agent (B) may be any one that reacts with the reactive functional group of the (meth)acrylic acid ester polymer (A), such as isocyanate cross-linking agents, epoxy cross-linking agents, and amine cross-linking agents. , melamine cross-linking agent, aziridine cross-linking agent, hydrazine cross-linking agent, aldehyde cross-linking agent, oxazoline cross-linking agent, metal alkoxide cross-linking agent, metal chelate cross-linking agent, metal salt cross-linking agent, ammonium salt cross-linking agent, etc. is mentioned. The cross-linking agent (B) may be used alone or in combination of two or more.

Among the above, the reactive functional groups possessed by the (meth)acrylic acid ester polymer (A), particularly the reactivity with the carboxy group derived from the carboxy group-containing monomer, and the viewpoint of electrolyte resistance after the reaction, insulation performance, etc. Therefore, it is preferable to use an isocyanate-based cross-linking agent.

The isocyanate-based cross-linking agent contains at least a polyisocyanate compound. Examples of polyisocyanate compounds include aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate and xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, and alicyclic polyisocyanates such as isophorone diisocyanate and hydrogenated diphenylmethane diisocyanate. , and their biuret, isocyanurate, and adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Among them, trimethylolpropane-modified aromatic polyisocyanate, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate, are preferable from the viewpoint of reactivity with carboxy groups.

The content of the cross-linking agent (B) in the adhesive composition P1 is preferably 0.1 parts by mass or more as a lower limit with respect to 100 parts by mass of the (meth)acrylic acid ester polymer (A). In particular, it is preferably at least 0.5 parts by mass, more preferably at least 1 part by mass. The upper limit of the content is preferably 20 parts by mass or less, particularly preferably 15 parts by mass or less, and further preferably 10 parts by mass or less. When the content of the cross-linking agent (B) is within the above range, the cross-linking structure is well formed, and the cohesive force of the formed first pressure-sensitive adhesive layer 12 is moderately high, thereby allowing the electrolyte to The elution resistance of is more excellent.

(2-3) Various Additives The adhesive composition P1 optionally contains various additives commonly used in acrylic pressure-sensitive adhesives, such as tackifiers, antioxidants, softeners, fillers, and the like. be able to. A polymerization solvent and a dilution solvent, which will be described later, are not included in the additives constituting the adhesive composition P1.

(3) Production of adhesive composition P1 The adhesive composition P1 is produced by producing a (meth)acrylic acid ester polymer (A), and adding inorganic fine particles to the obtained (meth)acrylic acid ester polymer (A). 121, and if desired, a cross-linking agent (B), an additive, and the like can be added.

The (meth)acrylic acid ester polymer (A) can be produced by polymerizing a mixture of monomers constituting the polymer by a conventional radical polymerization method. Polymerization of the (meth)acrylic acid ester polymer (A) is preferably carried out by a solution polymerization method, optionally using a polymerization initiator. However, the present invention is not limited to this, and may be polymerized without a solvent. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, and methyl ethyl ketone, and two or more of them may be used in combination.

Examples of polymerization initiators include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of azo compounds include 2,2′-azobisisobutyronitrile, 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane 1-carbonitrile), 2 ,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis(2-methylpropionate) , 4,4′-azobis(4-cyanovaleric acid), 2,2′-azobis(2-hydroxymethylpropionitrile), 2,2′-azobis[2-(2-imidazolin-2-yl) propane] and the like.

Examples of organic peroxides include benzoyl peroxide, t-butylperbenzoate, cumene hydroperoxide, diisopropylperoxydicarbonate, di-n-propylperoxydicarbonate, di(2-ethoxyethyl)peroxy dicarbonate, t-butylperoxyneodecanoate, t-butylperoxybivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionylperoxide, diacetylperoxide and the like.

The weight average molecular weight of the resulting polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol in the polymerization step.

After the (meth)acrylic acid ester polymer (A) is obtained, the inorganic fine particles 121 and optionally the cross-linking agent (B) and additives are added to the solution of the (meth)acrylic acid ester polymer (A). and thoroughly mixed to obtain an adhesive composition P1.

In addition, in order to adjust the viscosity of the adhesive composition P1 to be suitable for coating and to adjust the thickness of the first adhesive layer 12 to a desired film thickness, the adhesive composition P1 is appropriately added to the above-described polymerization solvent and diluted with a solvent or the like. It may be diluted and used as a coating liquid to be described later. Examples of the diluent solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone and the like, and two or more of them may be used in combination.

(4) Crosslinking of adhesive composition P1 When the adhesive composition P1 contains a crosslinking agent (B), the first adhesive layer 12 can be formed by crosslinking the adhesive composition P1. . Crosslinking of the adhesive composition P1 can usually be performed by heat treatment. This heat treatment can also serve as a drying treatment for volatilizing the diluent solvent and the like from the coating film of the adhesive composition P1 applied to the desired object.

The heating temperature of the heat treatment is preferably 50 to 150°C, particularly preferably 70 to 120°C. The heating time is preferably 30 seconds to 10 minutes, more preferably 50 seconds to 5 minutes.

After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (eg, 23° C., 50% RH). If this curing period is required, the first adhesive layer 12 is formed after the curing period has elapsed, and if the curing period is not required, after the heat treatment is completed.

(5) Thickness of First Adhesive Layer The lower limit of the thickness of the first adhesive layer 12 (value measured according to JIS K7130) is preferably 1 μm or more, particularly 3 μm or more. It is preferably 5 μm or more, more preferably 5 μm or more. By setting the lower limit of the thickness of the first adhesive layer 12 to the above range, the battery adhesive sheet 1 can easily exhibit high insulating properties. The upper limit of the thickness of the first pressure-sensitive adhesive layer 12 is preferably 50 μm or less, particularly preferably 13 μm or less, further preferably 9 μm or less. By setting the upper limit of the thickness of the first pressure-sensitive adhesive layer 12 to the above range, the amount of the electrolytic solution that enters from the end of the first pressure-sensitive adhesive layer 12 can be effectively reduced.

The thickness of the first adhesive layer 12 is preferably 1.1 times or more, more preferably 5 times or more, and preferably 10 times or more the average particle size of the inorganic fine particles 121. It is particularly preferable, and more preferably 15 times or more. When the thickness of the first adhesive layer 12 is 1.1 times or more the average particle diameter of the inorganic fine particles 121, the smoothness of the surface of the first adhesive layer 12 becomes more excellent, thereby The smoothness of the surface of the second pressure-sensitive adhesive layer 13 laminated on the first pressure-sensitive adhesive layer 12 opposite to the first pressure-sensitive adhesive layer 12 is improved, and high adhesive strength can be effectively obtained. can. The upper limit of the ratio of the thickness of the first adhesive layer 12 based on the average particle size of the inorganic fine particles 121 is not particularly limited, but it is preferably 100 times or less, more preferably 60 times or less. 30 times or less is particularly preferable.

1-3. Second Adhesive Layer The second adhesive layer 13 contains an adhesive component. The adhesive component contained in the second adhesive layer 13 can be appropriately selected from the viewpoints of adhesiveness, elution into the electrolytic solution, flame retardancy, heat resistance, insulation, and the like. As the adhesive component contained in the second adhesive layer 13, the one described above as the adhesive component contained in the first adhesive layer 12 can be used. The adhesive component contained in the second adhesive layer 13 may be the same as or different from the adhesive component contained in the first adhesive layer 12 . However, from the viewpoint that the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 tend to have good adhesion, the pressure-sensitive adhesive component contained in the second pressure-sensitive adhesive layer 13 is the first It is preferably of the same type as the adhesive component contained in the adhesive layer 12 of . In addition, the second adhesive layer 13 does not contain the inorganic fine particles 121 described above.

When an acrylic adhesive component is used as the adhesive component contained in the second adhesive layer 13, the acrylic adhesive component includes the above-described (meth)acrylic acid ester polymer (A) and the above-described crosslinking agent (B ). The second adhesive layer 13 is a second adhesive containing the above-described (meth)acrylic acid ester polymer (A), the above-described crosslinking agent (B), and, if desired, the various additives described above. It is preferably obtained from an adhesive composition for an agent layer (hereinafter sometimes referred to as "adhesive composition P2"). The adhesive composition P2 can be produced in the same manner as the adhesive composition P1. Moreover, when the adhesive composition P2 contains a crosslinking agent (B), the adhesive composition P2 can be crosslinked similarly to the adhesive composition P1.

The lower limit of the thickness of the second pressure-sensitive adhesive layer 13 (value measured according to JIS K7130) is preferably 1 μm or more, particularly preferably 3 μm or more, and further preferably 5 μm or more. is preferred. When the lower limit value of the thickness of the second pressure-sensitive adhesive layer 13 is as above, the pressure-sensitive adhesive sheet 1 for battery easily exhibits excellent adhesive strength. The upper limit of the thickness of the second pressure-sensitive adhesive layer 13 is preferably 50 μm or less, particularly preferably 13 μm or less, further preferably 9 μm or less. By setting the upper limit of the thickness of the second pressure-sensitive adhesive layer 13 to the above range, the amount of the electrolytic solution that enters from the end of the second pressure-sensitive adhesive layer 13 can be effectively reduced.

1-4. Release Sheet The release sheet 14 protects the second adhesive layer 13 until the battery adhesive sheet 1 is used, and is peeled off when the battery adhesive sheet 1 is used. In the battery adhesive sheet 1 according to this embodiment, the release sheet 14 is not necessarily required.

Examples of the release sheet 14 include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene naphthalate film, and polybutylene terephthalate film. , polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene/(meth)acrylic acid copolymer film, ethylene/(meth)acrylic acid ester copolymer film, polystyrene film, polycarbonate film, polyimide film, fluorine resin film , a liquid crystal polymer film, and the like are used. Crosslinked films of these are also used. Furthermore, a laminated film of these may be used.

The release surface of the release sheet 14 (the surface in contact with the second adhesive layer 13) is preferably subjected to a release treatment. Examples of release agents used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

Although the thickness of the release sheet 14 is not particularly limited, it is usually about 20 to 150 μm.

2. Physical Properties of Adhesive Sheet for Battery (1) Adhesive Strength The adhesive strength of the adhesive sheet for battery 1 according to the present embodiment to an aluminum plate is preferably 0.5 N/25 mm or more as a lower limit, and is preferably 1.0 N/25 mm. It is more preferably 2.0 N/25 mm or more, and more preferably 2.5 N/25 mm or more. Since the lower limit value of the adhesive strength of the adhesive sheet 1 for batteries is within the above range, the problem of peeling of the adhesive sheet 1 for batteries from an adherend (especially a metal member) is less likely to occur. Although the upper limit of the adhesive strength is not particularly limited, it is usually preferably 50 N/25 mm or less, particularly preferably 40 N/25 mm or less, and further preferably 30 N/25 mm or less. The adhesive strength in this specification basically refers to the adhesive strength measured by the 180° peeling method according to JIS Z0237:2009, and the detailed measuring method is as shown in the test examples described later.

(2) Insulation (Temperature rise due to forced internal short circuit test)
Regarding the battery adhesive sheet 1 (excluding the release sheet 14), the temperature rise on the side surface of the battery when a battery forced internal short circuit test was performed in accordance with JIS C8714: 2007 was the standard size (height 0.2 mm, width When a nickel piece of 0.1 mm, 1 mm on a side (L-shaped, angle of 90°) is used, the temperature is preferably 30°C or less, particularly preferably 20°C or less, and further preferably 15°C or less. preferable. Also, when nickel pieces of a size larger than the standard size (height 0.5, width 0.2 mm, side 3 mm L-shape, angle 90°) are used, the temperature is preferably 100°C or less, particularly 50°C or less. and more preferably 30° C. or lower. The details of this forced internal short-circuit test are as shown in test examples to be described later.

Since the temperature rise in the forced internal short-circuit test is the above, it can be said that the battery adhesive sheet 1 has high insulating properties, and the battery using the battery adhesive sheet 1 is highly safe. Since the battery adhesive sheet 1 according to the present embodiment includes the first adhesive layer 12 containing the inorganic fine particles 121, the temperature rise due to the forced internal short-circuit test can be suppressed as described above.

(3) Thickness of Battery Adhesive Sheet The thickness of the battery adhesive sheet 1 (excluding the thickness of the release sheet 14) is preferably 10 μm or more, particularly preferably 15 μm or more, and further preferably 20 μm. It is preferable that it is above. Moreover, the thickness of the battery adhesive sheet 1 is preferably 250 μm or less, particularly preferably 110 μm or less, further preferably 45 μm or less. When the thickness of the adhesive sheet for battery 1 is within the above range, it becomes easy to achieve both excellent adhesive strength and high insulation.

3. Method for Producing Battery Adhesive Sheet As a method for producing the battery adhesive sheet 1 according to the present embodiment, the first adhesive layer 12 and the second adhesive layer 13 are formed in this order on one side of the substrate 11. It is not particularly limited as long as it can be done. As an example, after producing a first laminate comprising the substrate 11 and the first adhesive layer 12 and a second laminate comprising the second adhesive layer 13 and the release sheet 14, By laminating these laminates so that the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13 are in contact with each other, the battery pressure-sensitive adhesive sheet 1 can be manufactured.

A first laminate comprising the substrate 11 and the first pressure-sensitive adhesive layer 12 can be produced, for example, as follows. A coating liquid containing the above-described adhesive composition P1 and optionally a solvent is applied to one side of the substrate 11 and heat-treated to form a coating film. The formed coating film becomes the first adhesive layer 12 as it is when the curing period is unnecessary, and becomes the first adhesive layer 12 after the curing period has passed when the curing period is required. As a result, a first laminate in which the first pressure-sensitive adhesive layer 12 is formed on the substrate 11 can be obtained.

The heat treatment can also serve as a drying treatment for volatilizing the diluting solvent or the like of the coating liquid. When the heat treatment is performed, the heating temperature is preferably 50 to 150°C, particularly preferably 70 to 120°C. The heating time is preferably 30 seconds to 10 minutes, more preferably 50 seconds to 2 minutes. After the heat treatment, if necessary, a curing period of about 1 to 2 weeks may be provided at room temperature (eg, 23° C., 50% RH).

A second laminate comprising a second pressure-sensitive adhesive layer 13 and a release sheet 14 can also be produced in the same manner as the first laminate. However, when producing the second laminate, a coating liquid containing the above-described adhesive composition P2 and optionally a solvent is applied to the release surface of the release sheet 14 to form the above-described coating film. do.

Moreover, after laminating the 1st laminated body and the 2nd laminated body, you may provide a curing period as needed.

As another method for producing the battery adhesive sheet 1 according to the present embodiment, the above-described adhesive composition P1 and adhesive composition P2 are simultaneously coated in multiple layers on the release surface of the release sheet 14, and a second layer is coated on the release sheet 14. 2 adhesive layer 13 and the first adhesive layer 12 are laminated in this order, and then one side of the substrate 11 is attached to the first adhesive layer 12 side of the laminate. By doing so, the battery adhesive sheet 1 may be obtained. Alternatively, the above-described adhesive composition P1 and adhesive composition P2 are simultaneously coated in multiple layers on one side of the substrate 11, and the first adhesive layer 12 and the second adhesive layer 13 are formed on the substrate 11. You may manufacture the adhesive sheet 1 for batteries by forming.

The above-described simultaneous multi-layer coating can be performed by a known technique, such as curtain coating, die coating, slide beat coating, and the like. Moreover, the adhesive composition P1 and the adhesive composition P2 may each be diluted with a desired solvent from the viewpoint of good simultaneous multi-layer coating.

[Lithium-ion battery]
A lithium-ion battery according to an embodiment of the present invention is one in which two or more conductors are fixed in contact with each other using the above-described battery adhesive sheet 1 inside the battery. At least one of the two or more conductors is preferably sheet-like, and at least one is wire-like or tape-like. A lithium ion battery according to a preferred embodiment will be described below.

As shown in FIG. 2, the lithium ion battery 2 according to the present embodiment includes a bottomed cylindrical outer body 21 having a negative electrode terminal 23 at the bottom, and a positive electrode terminal 22 provided at an opening of the outer body 21. , and an electrode body 24 provided inside the exterior body 21 . In addition, an electrolytic solution is sealed inside the lithium ion battery 2 .

The electrode body 24 includes a sheet-shaped (strip-shaped) positive electrode current collector 241 having a positive electrode active material layer 241a laminated thereon, a negative electrode current collector 242 having a negative electrode active material layer 242a laminated thereon, and a negative electrode current collector 242 having a laminated negative electrode active material layer 242a. and an intervening separator 243 . Note that the laminate of the positive electrode current collector 241 and the positive electrode active material layer 241a may be referred to as the positive electrode, and the laminate of the negative electrode current collector 242 and the negative electrode active material layer 242a may be referred to as the negative electrode. It is sometimes called an electrode. The positive electrode, the negative electrode, and the separator 243 are each wound and inserted into the exterior body 21 .

Further, as shown in FIG. 3, a linear or tape-shaped electrode take-out tab 244 is attached to the positive electrode current collector 241 with the above-described battery adhesive sheet 1, whereby the electrode take-out tab 244 is It is electrically connected to the positive current collector 241 . The electrode extraction tab 244 is also electrically connected to the positive electrode terminal 22 . The negative electrode current collector 242 is electrically connected to the negative electrode terminal 23 via an electrode extraction tab (not shown).

In general, the positive electrode current collector 241 and the negative electrode current collector 242 are made of metal such as aluminum, and the electrode extraction tab 244 is made of metal such as aluminum or copper.

The electrolyte used in the lithium ion battery 2 is usually a non-aqueous electrolyte. The non-aqueous electrolytic solution preferably includes, for example, a solution in which a lithium salt as an electrolyte is dissolved in a mixed solvent of a cyclic carbonate and a lower chain carbonate. Examples of lithium salts include fluorine-based complex salts such as lithium hexafluorophosphate (LiPF ₆ ) and lithium borofluoride (LiBF ₄ ), and LiN(SO ₂ Rf) ₂ ·LiC(SO ₂ Rf) ₃ (where Rf=CF ₃ , C ₂ F ₅ ) and the like are used. Ethylene carbonate, propylene carbonate and the like are used as the cyclic carbonate, and dimethyl carbonate, ethylmethyl carbonate, diethyl carbonate and the like are preferably used as the lower chain carbonate.

The lithium ion battery 2 according to the present embodiment can be manufactured by a normal method except for using the above-described battery adhesive sheet 1 for fixing the electrode extraction tab 244 .

In the lithium ion battery 2 according to this embodiment, the battery adhesive sheet 1 is used to attach the electrode extraction tab 244 to the positive electrode current collector 241 . This adhesive sheet for battery 1 includes a first adhesive layer 12 containing inorganic fine particles 121 and a second adhesive layer 13 containing no inorganic fine particles 121, thereby exhibiting excellent adhesive strength and , has high insulation. As a result, in the lithium ion battery 2 according to the present embodiment, problems such as poor contact between the positive electrode current collector 241 and the electrode extraction tab 244 are unlikely to occur, and even if an internal short circuit occurs at the battery adhesive sheet 1 part, it It is possible to suppress the temperature rise due to low temperature, and to exhibit high safety.

The embodiments described above are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments is meant to include all design changes and equivalents that fall within the technical scope of the present invention.

For example, in the battery adhesive sheet 1, the release sheet 14 may be omitted. Further, in the battery pressure-sensitive adhesive sheet 1, another layer is provided between the substrate 11 and the first pressure-sensitive adhesive layer 12 or between the first pressure-sensitive adhesive layer 12 and the second pressure-sensitive adhesive layer 13. may be provided.

EXAMPLES The present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
1. Preparation of adhesive composition coating liquid 80 parts by weight of 2-ethylhexyl acrylate, 15 parts by weight of lauryl methacrylate, and 5 parts by weight of acrylic acid were copolymerized by a solution polymerization method to prepare a (meth)acrylic acid ester polymer. . When the molecular weight of this polymer was measured using gel permeation chromatography (GPC), which will be described later, the weight average molecular weight (Mw) was 750,000.

Next, 100 parts by mass of the obtained (meth)acrylic acid ester polymer (solid content conversion value; the same applies hereinafter) and trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., trade name "BHS8515") as an isocyanate-based cross-linking agent ”) and 3.72 parts by mass, and diluted with ethyl acetate to obtain a coating liquid (solid concentration: 30%) of the adhesive composition for the second adhesive layer. The coating liquid contains the above-mentioned (meth)acrylic acid ester polymer and the above-mentioned isocyanate-based cross-linking agent as adhesive components.

In addition, alumina fine particles as inorganic fine particles (manufactured by Denka Co., Ltd., product name "ASFP -20", average particle size: 0.26 μm) was added and mixed to obtain a coating liquid of the adhesive composition for the first adhesive layer.

2. Formation of the first adhesive layer On one side of a polyimide film (manufactured by Toray DuPont, trade name “Kapton 100H”, thickness 25 μm, UL94 standard flame retardant level V-0) as a base material, the above step 1 The coating liquid of the pressure-sensitive adhesive composition for the first pressure-sensitive adhesive layer obtained in 1 is applied with a knife coater, the resulting coating film is dried at 120 ° C. for 1 minute, and a first pressure-sensitive adhesive layer having a thickness of 5 μm is formed. formed. As a result, a first laminate composed of the substrate and the first pressure-sensitive adhesive layer was obtained.

3. Formation of the second pressure-sensitive adhesive layer The coating solution of the pressure-sensitive adhesive composition for the second pressure-sensitive adhesive layer obtained in the above step 1 is applied to a polyethylene terephthalate film with a silicone-based release agent on one side of the release sheet (Lintec Co., Ltd.). (trade name “SP-PET251130” manufactured by Sanyo Co., Ltd.)) was coated with a knife coater, and the resulting coating film was dried at 120° C. for 1 minute to form a second pressure-sensitive adhesive layer having a thickness of 5 μm. As a result, a second laminate composed of the release sheet and the second pressure-sensitive adhesive layer was obtained.

4. Preparation of battery adhesive sheet The first adhesive layer side of the first laminate obtained in the above step 2 and the second adhesive layer side of the second laminate obtained in the above step 3 Then, by curing for 7 days at 23 ° C. and 50% RH, the base material, the first adhesive layer, the second adhesive layer, and the release sheet are in this order. A laminated pressure-sensitive adhesive sheet for battery was obtained.

Here, the weight average molecular weight (Mw) described above is a weight average molecular weight in terms of standard polystyrene measured under the following conditions using gel permeation chromatography (GPC).
<Measurement conditions>
・ GPC measurement device: HLC-8320 manufactured by Tosoh Corporation
・ GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel super HM-H
TSK gel super H2000
・Measurement solvent: tetrahydrofuran ・Measurement temperature: 40°C

[Examples 2 to 5]
A battery pressure-sensitive adhesive sheet was produced in the same manner as in Example 1, except that the type and amount of inorganic fine particles added were changed as shown in Table 1.

[Comparative Example 1]
The coating liquid of the adhesive composition for the first adhesive layer obtained in step 1 of Example 1 was applied to a polyimide film as a substrate (manufactured by Toray DuPont, trade name “Kapton 100H”, thickness 25 μm, UL94 One side of the standard flame retardant level V-0) was coated with a knife coater, and the resulting coating film was dried at 120° C. for 1 minute to form a first pressure-sensitive adhesive layer with a thickness of 10 μm.

Subsequently, on the surface of the formed first pressure-sensitive adhesive layer opposite to the base material, a release sheet (manufactured by Lintec, trade name "SP-PET251130") obtained by releasing one side of a polyethylene terephthalate film with a silicone-based release agent. ), and then cured at 23 ° C. and 50% RH for 7 days, so that the base material, the first adhesive layer, and the release sheet are laminated in this order. A sticky sheet was obtained.

[Comparative Example 2]
The coating liquid of the adhesive composition for the first adhesive layer obtained in Step 1 of Example 1 was applied to a release sheet (manufactured by Lintec, trade name "SP -PET251130") was coated with a knife coater, and the resulting coating film was dried at 120° C. for 1 minute to form a first pressure-sensitive adhesive layer having a thickness of 10 μm.

Subsequently, a polyimide film (trade name “Kapton 100H” manufactured by Toray DuPont Co., Ltd., thickness 25 μm, UL94 standard flame retardant One surface of level V-0) is laminated, and then cured at 23 ° C. and 50% RH for 7 days, so that the substrate, the first adhesive layer, and the release sheet are laminated in this order. A pressure-sensitive adhesive sheet for a battery was obtained.

[Comparative Example 3]
The coating liquid of the adhesive composition for the second adhesive layer obtained in Step 1 of Example 1 was applied to a release sheet (manufactured by Lintec Corporation, trade name "SP-PET251130") was coated with a knife coater, and the obtained coating film was dried at 120° C. for 1 minute to form a second adhesive layer having a thickness of 10 μm.

Subsequently, on the surface of the formed second adhesive layer opposite to the release sheet, a polyimide film as a substrate (manufactured by Toray DuPont, trade name "Kapton 100H", thickness 25 μm, UL94 standard flame retardant One surface of level V-0) is laminated, and then cured at 23 ° C. and 50% RH for 7 days, so that the base material, the second adhesive layer, and the release sheet are laminated in this order. A pressure-sensitive adhesive sheet for a battery was obtained.

[Test Example 1] (Measurement of adhesive strength)
The adhesive force of the adhesive sheet for batteries according to this test example was measured according to JIS Z0237:2009, except for the operations described below.

After cutting the battery pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples into a width of 25 mm and a length of 250 mm, the release sheet was peeled off to obtain a test piece. The exposed second adhesive layer of this test piece (the first adhesive layer for Comparative Examples 1 and 2) was applied to an aluminum plate as an adherend under an environment of 23 ° C. and 50% RH. It was attached using a rubber roller. Immediately after that, using a universal tensile tester (manufactured by Orientec, product name "Tensilon UTM-4-100"), peel the test piece from the aluminum plate at a peel angle of 180 ° and a peel speed of 300 mm / min. The adhesive strength (N/25 mm) was measured by. Table 1 shows the results.

[Test Example 2] (Evaluation of electrolyte resistance)
The adhesive sheets for batteries obtained in Examples and Comparative Examples were cut to a width of 11 mm and a length of 30 mm, and then the release sheet was peeled off. Then, the exposed second pressure-sensitive adhesive layer (the first pressure-sensitive adhesive layer for Comparative Examples 1 and 2) was applied to an aluminum plate as an adherend under an environment of 23°C and 50% RH with a 2 kg rubber roller. This was used as a test piece. This test piece was used as an electrolytic solution together with a prepared solution prepared by dissolving lithium hexafluorophosphate (LiPF ₆ ) at a concentration of 1 mol/L in a mixture of ethylene carbonate and diethyl carbonate at a volume ratio of 1:1. It was sealed in an aluminum laminate bag and heated at 80° C. for 3 days. After that, the test piece was taken out, and the battery pressure-sensitive adhesive sheet was peeled off from the aluminum plate with tweezers, and the easiness of peeling at that time was confirmed. Then, the electrolytic solution resistance was evaluated based on the following criteria. Table 1 shows the results.
3: Peeled off at the interface between the second pressure-sensitive adhesive layer (the first pressure-sensitive adhesive layer in Comparative Examples 1 and 2) and the adherend.
2 . . . The second adhesive layer (the first adhesive layer in Comparative Examples 1 and 2) swelled and caused cohesive failure or transfer adhesion.
1: Peeled off in an aluminum laminate bag.

[Test Example 3] (Evaluation of battery insulation)
(1) Preparation of positive electrode 100 parts by mass of LiNi _0.82 Co _0.15 Al _0.03 O ₂ as a positive electrode active material, 1.0 parts by mass of acetylene black, and 0.9 parts by mass of polyvinylidene fluoride (binder) and an appropriate amount of NMP were mixed to prepare a positive electrode paste. The obtained positive electrode paste was evenly applied to both sides of a 20 μm thick aluminum foil serving as a positive electrode current collector, dried, and then rolled to prepare a strip-shaped positive electrode having a width of 58 mm. However, a slit-like exposed portion was provided on both surfaces near the center in the longitudinal direction of the positive electrode, from which one end portion to the other end portion in the width direction of the positive electrode current collector was exposed. At this time, the width W of the exposed portion was set to 6.5 mm.

Next, a strip-shaped positive electrode lead made of aluminum having a width of 3.5 mm and a length of 68 mm was superimposed on the exposed portion of the positive electrode current collector so that the length of the drawn portion was 15 mm and the length of the overlapping portion was 53 mm. The overlapping portion was welded to the exposed portion.

After that, the battery pressure-sensitive adhesive sheets obtained in Examples and Comparative Examples were attached to the positive electrode so as to cover the entire surface of the exposed portion and the entire surface of the overlapping portion. At that time, the battery adhesive sheet was made to protrude by 2 mm from both ends of the positive electrode in the width direction so that the exposed portion was reliably covered with the battery adhesive sheet. In addition, the battery pressure-sensitive adhesive sheet was allowed to protrude from the positive electrode active material layer by 2 mm from both ends of the exposed portion in the width direction.

(2) Preparation of Negative Electrode 100 parts by mass of scaly artificial graphite having an average particle size of about 20 μm, which is the negative electrode active material, 1 part by mass of styrene-butadiene rubber (SBR) (binder), and 1 part by mass of carboxyl A negative electrode paste was prepared by mixing methyl cellulose (thickener) and water. The obtained negative electrode paste was evenly applied to both sides of a copper foil having a thickness of 8 μm, which was used as a negative electrode current collector, dried, and then rolled to prepare a strip-shaped negative electrode having a width of 59 mm. However, on both sides of the end portion of the negative electrode on the winding end side, an exposed portion was provided from one end portion to the other end portion in the width direction of the negative electrode current collector.

Next, a strip-shaped nickel negative electrode lead having a width of 3 mm and a length of 40 mm was superimposed on the exposed portion of the negative electrode current collector, aligned in the same manner as the positive electrode, and the overlapping portion was welded to the exposed portion.

(3) Preparation of Electrode Group The positive electrode and the negative electrode obtained above were laminated with a separator interposed therebetween and wound to form an electrode group. At this time, the lead-out portion of the positive electrode lead was projected from one end surface of the electrode group, and the lead-out portion of the negative electrode lead was projected from the other end surface of the electrode group.

(4) Preparation of Nonaqueous Electrolyte LiPF ₆ was dissolved in a mixed solvent of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 1:1:8) to a concentration of 1.4 mol/L. to prepare a non-aqueous electrolyte.

(5) Fabrication of Battery An iron battery case (diameter: 18 mm, height: 65 mm) with a nickel-plated inner surface accommodated an electrode group sandwiched between a lower insulating ring and an upper insulating ring. At this time, the negative electrode lead was interposed between the lower insulating ring and the bottom of the battery case. Also, the positive electrode lead was passed through the central through-hole of the upper insulating ring. Next, the electrode rod was passed through the central hollow portion of the electrode group and the central through hole of the lower insulating ring, and one end of the negative electrode lead was welded to the inner bottom surface of the battery case. Also, one end of the positive electrode lead pulled out from the through-hole of the upper insulating ring was welded to the inner surface of the sealing plate having a gasket on the peripheral edge. After that, grooves were formed in the vicinity of the opening of the battery case, and a non-aqueous electrolyte was injected into the battery case to impregnate the electrode group. Next, the opening of the battery case was closed with a sealing plate, the opening end of the battery case was crimped to the peripheral edge of the sealing plate via a gasket, and a cylindrical non-aqueous electrolyte secondary battery (energy density 700 Wh / L) was obtained. completed.

(6) Implementation of Forced Internal Short Circuit Test Using the non-aqueous electrolyte secondary battery obtained above, a forced internal short circuit test of the battery was performed in accordance with JIS C8714:2007. As nickel pieces, standard size (height 0.2 mm, width 0.1 mm, side 1 mm L shape, angle 90°) and size larger than standard size (height 0.5, width 0.2 mm, An L-shaped one with a side of 3 mm and an angle of 90° was prepared. These nickel small pieces were placed between the battery pressure-sensitive adhesive sheet and the separator so that the nickel small pieces penetrated the battery pressure-sensitive adhesive sheet. Then, a forced internal short-circuit test was performed, and the temperature rise (°C) on the side surface of the battery was measured with a thermocouple. Table 1 shows the results.

Details of abbreviations and the like in Table 1 are as follows.
[Inorganic fine particles]
Alumina: Alumina fine particles (manufactured by Denka, product name “ASFP-20”, average particle size: 0.26 μm)
Titania: titania fine particles (manufactured by Sakai Chemical Industry Co., Ltd., product name “R-310”, average particle size: 0.2 μm)
Calcium carbonate: Calcium carbonate fine particles (manufactured by Kojima Chemical Co., Ltd., product name “light calcium carbonate”, average particle size: 1.1 μm)

As is clear from Table 1, the battery pressure-sensitive adhesive sheets of Examples have good adhesive strength and electrolyte resistance, and have high insulation properties, and are capable of suppressing the temperature rise caused by the forced internal short-circuit test. was made.

The pressure-sensitive adhesive composition and battery pressure-sensitive adhesive sheet according to the present invention are suitable for use inside a lithium ion battery, and particularly suitable for attaching an electrode take-out tab to an electrode.

DESCRIPTION OF SYMBOLS 1... Battery adhesive sheet 11... Base material 12... 1st adhesive layer 121... Inorganic fine particle 13... 2nd adhesive layer 14... Release sheet 2... Lithium ion battery 21... Exterior body 22... Positive electrode terminal 23... Negative electrode Terminal 24... Electrode body 241... Positive electrode current collector 241a... Positive electrode active material layer 242... Negative electrode current collector 242a... Negative electrode active material layer 243... Separator 244... Electrode extraction tab

Claims (5)

a substrate;
A first adhesive layer containing inorganic fine particles provided on one surface side of the base material;
A second adhesive layer that does not contain the inorganic fine particles and is provided on the surface of the first adhesive layer opposite to the base material ,
The content of the inorganic fine particles in the first adhesive layer is 150 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the adhesive component contained in the first adhesive layer.
A battery adhesive sheet characterized by: 2. The battery pressure-sensitive adhesive sheet according to claim 1, wherein the first pressure-sensitive adhesive layer has a thickness of 1 [mu]m or more and 50 [mu]m or less. 3. The battery pressure-sensitive adhesive sheet according to claim 1, wherein the second pressure-sensitive adhesive layer has a thickness of 1 [mu]m or more and 50 [mu]m or less. The pressure-sensitive adhesive sheet for batteries according to any one of claims 1 to 3 , wherein the pressure-sensitive adhesive sheet for batteries has an adhesive force of 0.5 N/25 mm or more and 50 N/25 mm or less to an aluminum plate. Lithium ion characterized in that two or more conductors are fixed in contact with each other by using the battery adhesive sheet according to any one of claims 1 to 4 inside the battery. battery.

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