Curable adhesive for battery

Abstract

A curable adhesive for a battery according to the present invention comprises: a first agent that contains an organic polymer having a hydrolyzable silyl group and a thermally conductive filler and that is filled in a first container; and a second agent that contains a silanol condensation catalyst and a thermally conductive filler and that is filled in a second container. A cured product obtained by curing a curable adhesive composition for a battery in which are mixed the first agent and the second agent for two weeks in a 25°C, 50% RH environment has a shear adhesive strength of 0.5-2.5 MPa. The stress-time elongation of the cured product at a thickness of 2 mm is 0.3 mm or more, and the thermal conductivity of the cured product is 1.5 W / m∙K or more.　According to the present invention, it is possible to provide a curable adhesive for a battery, a cured product of which has appropriate adhesive force, high thermal conductivity, and excellent ability to follow expansion and contraction of a battery cell.

Description

Curable adhesive for batteries

[0001] The present invention relates to a curable adhesive for batteries.

[0002] Thermally conductive compositions containing thermally conductive fillers are widely known as curable liquid compositions. For example, they are filled between a heat generating element and a heat sink, and then cured to form a cured product, which is used as a thermally conductive member such as a heat dissipating gap filler that transfers heat generated by the heat generating element to the heat sink.

[0003] In recent years, amid a market backdrop of steady growth in the production volume of electric vehicles (EVs), there has been an increasing demand for two-component, room-temperature curing heat-dissipating gap fillers for lithium-ion batteries (LiBs). From the viewpoint of heat dissipation, in lithium-ion batteries, thermally conductive compositions are often filled between components such as battery cells, battery modules, and battery packs to fix the components together and to enhance heat dissipation.

[0004] For example, Patent Document 1 describes an invention relating to a thermally conductive curable composition as a high thermal conductivity thermal interface material, which includes a first part containing a catalyst, a ceramic filler mixture, a low-volatility organic liquid, and water, and a second part containing a silyl-modified reactive polymer, a low-volatility organic liquid, and a ceramic filler mixture. Patent Document 2 also discloses a moisture-curable composition having high thermal conductivity and suitable as a gap filler, sealant, or adhesive for batteries, etc., which contains a reactive silane group-containing organic polymer, a specific filler, a dispersion additive, a curing catalyst, and a plasticizer in specific amounts.

[0005] Special table 2022-521790 publication Special table 2022-520317 publication

[0006] To further popularize EVs in the future, improvements in EV performance, such as increased driving range and shorter charging times, are required. Meanwhile, to achieve sustainable EV development while preserving the global environment, it is important to reduce waste during the EV manufacturing process and recycle used batteries, and battery structure designs that facilitate rework and recycling are needed. To improve driving range, the battery module housing is eliminated, improving the loading efficiency of the battery, thereby improving energy density and reducing weight. This design method, however, makes it difficult to mechanically fix the battery cells due to the elimination of the housing. Therefore, the battery cells must be fixed to a cooling plate or the like using a thermally conductive resin composition, and the adhesive strength of the thermally conductive resin composition needs to be improved.

[0007] On the other hand, when quality defects are found during inspection after assembling battery components during the EV manufacturing process, or in order to recycle battery cells and cooling plates from EVs that have been collected from the market as used, it is necessary for them to be easily peeled from the thermally conductive resin composition filled between the cell and cooling plate. Urethane-based resin compositions are commonly used as thermally conductive resin compositions for LiBs, but urethane-based resin compositions have such high adhesive strength that components such as cooling plates are deformed due to insufficient strength when peeled, making it impossible to recycle the components after peeling.

[0008] Problems related to thermally conductive resin compositions have also been identified regarding the reduction of charging time. Rapid charging in a short period of time tends to increase the temperature of battery cells more easily than conventional methods. Therefore, two quality improvements are required for thermally conductive resin compositions. One is to improve thermal conductivity to improve the cooling efficiency of the battery cells, and the other is to improve compliance with the expansion and contraction of the battery cells. Poor compliance leads to the thermally conductive composition's tendency to peel off from the battery cells, resulting in poor heat dissipation. These two measures are in a trade-off relationship. In other words, improving thermal conductivity requires increasing the filling rate of the thermally conductive filler, but this also reduces deformation resistance and compliance. Conventional thermally conductive compositions for batteries have room for improvement in terms of achieving a balance of physical properties, i.e., high thermal conductivity and compliance with the expansion and contraction of battery cells in their cured products.

[0009] Therefore, the present invention aims to provide a curable adhesive for batteries that can achieve the following: the cured product has ``moderate adhesive strength'' that allows the components that form the battery structure to be fixed with appropriate adhesive strength, thereby maintaining a certain level of strength while also being easily peelable; and the cured product has high thermal conductivity and the ability to follow the expansion and contraction of the battery cell.

[0010] After extensive research, the present inventors discovered that the above-mentioned problems can be solved by a curable adhesive for batteries that is composed of a first part containing a silanol condensation catalyst and a thermally conductive filler, and a second part containing an organic polymer having a hydrolyzable silyl group and a thermally conductive filler, and that the cured product has a shear adhesive strength, elongation at maximum stress, and thermal conductivity within specific ranges, and thus completed the present invention. The present invention provides the following [1] to

[15] .

[0011] [1] A curable adhesive for batteries, comprising a first part containing a silanol condensation catalyst and a thermally conductive filler and filled in a first container, and a second part containing an organic polymer having a hydrolyzable silyl group and a thermally conductive filler and filled in a second container, wherein the first and second parts are mixed to form a curable adhesive composition for batteries, and the cured product is cured for two weeks at 25°C and 50% RH, and the cured product has a shear adhesive strength of 0.5 to 2.5 MPa in a tensile shear test, an elongation at maximum stress of 0.3 mm or more in a tensile shear test with a thickness of 2 mm, and a thermal conductivity of 1.5 W / m K or more. [2] The curable adhesive for batteries according to [1] above, wherein the content of the thermally conductive filler in the curable adhesive composition for batteries is 60 to 85% by volume, and the thermally conductive filler contains a thermally conductive filler having hydroxyl groups on its surface. [3] The content of the thermally conductive filler in the curable adhesive composition for a battery is 60 to 85% by volume, the thermally conductive filler contains a metal hydroxide, and the sum of the surface areas of the metal hydroxides per 100 g of an organic polymer having a hydrolyzable silyl group in the curable adhesive composition for a battery is 200 to 1500 m ２The curable adhesive for batteries according to [1] or [2] above, wherein the first part further comprises an organic polymer having a hydrolyzable silyl group. [4] The curable adhesive for batteries according to any one of [1] to [3] above, wherein the first part further comprises an organic polymer having a hydrolyzable silyl group. [5] The curable adhesive for batteries according to any one of [1] to [4] above, wherein the second part further comprises water. [6] The curable adhesive for batteries according to any one of [3] to [5] above, wherein the content of the metal hydroxide in the curable adhesive composition for batteries is 10 to 80 volume %. [7] The curable adhesive for batteries according to any one of [3] to [6] above, wherein the metal hydroxide is aluminum hydroxide. [8] The curable adhesive for batteries according to any one of [3] to [7] above, wherein the metal hydroxide is aluminum hydroxide that has not been surface-treated. [9] The curable adhesive for batteries according to any one of [1] to [8] above, wherein the thermally conductive filler comprises small-particle aluminum hydroxide having an average particle size of 20 μm or less.

[10] The curable adhesive for batteries according to any one of [1] to [9] above, wherein the organic polymer having a hydrolyzable silyl group is a polyalkylene oxide having a hydrolyzable silyl group.

[11] The curable adhesive for batteries according to any one of [1] to

[10] above, wherein the organic polymer having a hydrolyzable silyl group has a hydrolyzable silyl group at the end of a linear main chain.

[12] The curable adhesive for batteries according to any one of [1] to

[11] above, wherein the organic polymer having a hydrolyzable silyl group has a number average molecular weight (Mn) of 1,000 to 40,000.

[13] The curable adhesive for batteries according to any one of [1] to

[12] above, wherein at least one of the first and second parts further contains a plasticizer.

[14] The viscosity η1 (25°C, shear rate 1 (1 / sec)) of the first agent is 100 to 1000 Pa s, the viscosity η2 (25°C, shear rate 1 (1 / sec)) of the second agent is 100 to 1000 Pa s, and the absolute value of the difference between the viscosity η1 and the viscosity η2 is 400 Pa s or less. [1] to

[13] The curable adhesive for batteries described in any one of the above.

[15] A battery structure comprising a structure and a plurality of cells arranged on the structure, wherein an adhesive layer is arranged at least either between the structure and the cells or between the plurality of cells, the adhesive layer being a cured product of a curable adhesive composition for batteries comprising an organic polymer having a hydrolyzable silyl group and a thermally conductive filler, the cured product having a shear adhesive strength of 0.5 to 2.5 MPa in a tensile shear test, an elongation at maximum stress of 0.3 mm or more in a tensile shear test with a thickness of 2 mm, and a thermal conductivity of 1.5 W / m K or more.

[16] Use of the curable adhesive for batteries according to any of [1] to

[13] above as at least one of a gap material between battery cells, a gap material between a battery cell and a module housing, a gap material between a battery module and a battery pack housing, and a gap material between a battery cell and a battery pack housing.

[0012] According to the present invention, it is possible to provide a curable adhesive for batteries that has "moderate adhesive strength" that allows the components that form the battery structure to be fixed with appropriate adhesive strength while maintaining a certain level of strength, has easy peelability, has high thermal conductivity, and is excellent at following the expansion and contraction of battery cells.

[0013] FIG. 1 is a schematic diagram showing a container set according to one embodiment; FIG. 2 is a schematic diagram showing a container set according to one embodiment; FIG. 3 is a cross-sectional view schematically showing one embodiment of a battery structure; FIG. 4 is a perspective view showing a representative configuration of a battery cell; FIG. 5 is a cross-sectional view schematically showing another embodiment of a battery structure; FIG. 6 is a cross-sectional view schematically showing another embodiment of a battery structure; FIG. 7 is a cross-sectional view schematically showing another embodiment of a battery structure;

[0014] [Curable Adhesive for Batteries] The curable adhesive for batteries of the present invention comprises a first part containing a silanol condensation catalyst and a thermally conductive filler, and filled in a first container, and a second part containing an organic polymer having a hydrolyzable silyl group and a thermally conductive filler, and filled in a second container. The first and second parts are mixed to form a curable adhesive composition for batteries. The cured adhesive composition is then cured for two weeks at 25°C and 50% RH. The cured product has a shear adhesive strength of 0.5 to 2.5 MPa in a tensile shear test, an elongation at maximum stress of 0.3 mm or more in a tensile shear test with a thickness of 2 mm, and a thermal conductivity of 1.5 W / m·K or more.

[0015] The curable adhesive for batteries of the present invention is stored separately as a first part filled in a first container and a second part filled in a second container. By storing the first and second parts separately, polymerization and hardening of the organic polymer having a hydrolyzable silyl group during storage can be suppressed, thereby improving storage stability. At the time of use, the first and second parts are mixed to form a curable adhesive composition for batteries containing the organic polymer having a hydrolyzable silyl group, a thermally conductive filler, and a silanol condensation catalyst, and the composition is cured to be used as a cured product.

[0016] <Shear Adhesion Strength> The battery curable adhesive of the present invention has a shear adhesive strength of 0.5 to 2.5 MPa when the battery curable adhesive composition, comprising a first and second parts, is cured for two weeks at 25°C and 50% RH. RH refers to relative humidity. If the shear adhesive strength is less than 0.5 MPa, it becomes difficult for the cured product formed by the battery curable adhesive to secure the components forming the battery structure with appropriate adhesive strength. On the other hand, if the shear adhesive strength exceeds 2.5 MPa, the releasability of the cured product formed by the battery curable adhesive from various components decreases, making recycling difficult. The shear adhesive strength of the cured product is preferably 0.6 to 1.8 MPa, more preferably 0.8 to 1.4 MPa. In the present invention, the shear adhesive strength can be adjusted to a desired range by adjusting the type of organic polymer having a hydrolyzable silyl group, the type and amount of thermally conductive filler used, and other factors. Even when a high amount of thermally conductive filler is loaded to achieve high thermal conductivity, a certain level of shear adhesive strength can be more easily ensured by using a thermally conductive filler having hydroxyl groups on its surface, as described below.

[0017] The shear adhesive strength is measured by a tensile shear test. Specifically, the tensile shear strength is measured on a 2 mm thick cured product (test piece) obtained by applying the battery curable adhesive composition between two substrates and curing it for two weeks at 23°C and 50% RH. That is, it is the maximum stress on the stress curve measured until the cured product, which is the adhesive joint, breaks due to a load (shear stress) that tends to shift the substrates in opposite directions. The substrate is made of cold-rolled steel plate (SPCC) that has been subjected to cathodic electrodeposition coating. Details of the shear adhesive strength measurement method are as described in the Examples.

[0018] <Elongation at Maximum Stress> The curable adhesive for batteries of the present invention is a curable adhesive composition for batteries obtained by mixing the first and second parts and curing the composition at 25°C and 50% RH for two weeks. The cured product has an elongation at maximum stress of 0.3 mm or more in a tensile shear test. If the elongation at maximum stress of the cured product is less than 0.3 mm, the cured product will have poor compliance with the expansion and contraction of the battery cell. As a result, the cured product will be more likely to peel from the battery cell, heat dissipation will be reduced, and rapid charging will be difficult. From the viewpoint of improving compliance, the elongation at maximum stress of the cured product is preferably 0.4 mm or more, more preferably 0.5 mm or more. The upper limit of the elongation at maximum stress of the cured product is not particularly limited, but is, for example, 3 mm. In the present invention, the elongation at maximum stress can be adjusted to a desired range by changing the type of organic polymer having a hydrolyzable silyl group, the type and amount of the thermally conductive filler used, and the like. As described below, by adjusting the sum of the surface areas of the metal hydroxides relative to 100 g of the organic polymer having a hydrolyzable silyl group within a predetermined range, the elongation at maximum stress can be easily adjusted within a desired range. The elongation at maximum stress was measured by subjecting a 2 mm thick cured product to a test (shear tensile strength test) similar to the method described above for shear adhesive strength, and the displacement at which the tensile stress reached its maximum value (maximum value) was taken as the elongation at maximum stress. The displacement refers to the amount of longitudinal deformation (length: mm) of the sample from the start of measurement until the tensile stress reached its maximum value (maximum value).

[0019] <Thermal Conductivity> The curable adhesive for batteries of the present invention has a thermal conductivity of 1.5 W / m·K or more when the battery curable adhesive composition, comprising a first and second parts, is cured for two weeks at 25°C and 50% RH. A thermal conductivity of less than 1.5 W / m·K makes it difficult to dissipate heat generated by the battery cell, making rapid charging difficult. The thermal conductivity is preferably 2 W / m·K or more, and more preferably 2.5 W / m·K or more. The higher the thermal conductivity, the better, but in practice, the upper limit is, for example, 5 W / m·K or less. Furthermore, achieving both the maximum stress elongation and thermal conductivity improves heat dissipation during rapid charging, resulting in a curable adhesive for batteries suitable for rapid charging. Thermal conductivity is measured in accordance with ASTM D5470.

[0020] <Organic Polymer Having Hydrolyzable Silyl Groups> The second part of the battery curable adhesive of the present invention, and the battery curable adhesive composition obtained by mixing the first and second parts, contain an organic polymer having a hydrolyzable silyl group. It is also preferable that the first part also contains an organic polymer having a hydrolyzable silyl group. By including an organic polymer having a hydrolyzable silyl group in the first part, the compositions of the first and second parts become similar, reducing the difference in viscosity between the two, making it easier to achieve a uniform composition during mixing and improving handleability. The hydrolyzable silyl groups in the organic polymer are hydrolyzed by moisture such as humidity to form silanol groups, which can then form siloxane bonds by condensation polymerization between the silanol groups or between the silanol groups and the hydrolyzable silyl groups. This allows the organic polymer to form a crosslinked structure and harden, resulting in a rubber-like elastomer. Note that a silanol group refers to a hydroxy group (Si—OH) directly bonded to a silicon atom.

[0021] A hydrolyzable silyl group is a group in which 1 to 3 hydrolyzable groups are bonded to a silicon atom. The hydrolyzable groups of the hydrolyzable silyl group are not particularly limited, and examples thereof include a hydrogen atom, a halogen atom, an alkoxy group, an acyloxy group, a ketoximate group, an amino group, an amide group, an acid amide group, an aminooxy group, a mercapto group, and an alkenyloxy group. Among these, an alkoxysilyl group is preferred as the hydrolyzable silyl group because of its mild hydrolysis reaction. Examples of the alkoxysilyl group include trialkoxysilyl groups such as trimethoxysilyl, triethoxysilyl, triisopropoxysilyl, and triphenoxysilyl groups; dialkoxysilyl groups such as dimethoxymethylsilyl and diethoxymethylsilyl groups; and monoalkoxysilyl groups such as methoxydimethylsilyl and ethoxydimethylsilyl groups. Of these, dialkoxysilyl groups are more preferred, and dimethoxymethylsilyl groups are particularly preferred.

[0022] The organic polymer having a hydrolyzable silyl group may have a linear or branched main chain, but preferably has a linear main chain. That is, the organic polymer having a hydrolyzable silyl group of the present invention preferably has a hydrolyzable silyl group at the end of a linear main chain. When an organic polymer having a hydrolyzable silyl group at the end is used, the cured product becomes more easily elongated and has improved conformability.

[0023] The terminal silylation rate of the organic polymer having a hydrolyzable silyl group is preferably 70% or more, more preferably 80% or more, and even more preferably 90% or more. When the terminal silylation rate is a certain level or more, it becomes easier to appropriately adjust the curability and elongation of the curable adhesive for batteries. The terminal silylation rate means the ratio of silylated terminals to all terminals of the organic polymer having a hydrolyzable silyl group. There is no particular upper limit to the terminal silylation rate, but it is, for example, 100% or less, and in practical use, can be 99% or less. The terminal silylation rate of the organic polymer having a hydrolyzable silyl group is １ It is determined by H-NMR.

[0024] The average number of hydrolyzable silyl groups in one molecule of an organic polymer having a hydrolyzable silyl group is preferably 1 to 3. When the number of hydrolyzable silyl groups in the polymer is within this range, the curing property and elongation property of the curable adhesive for batteries are improved. The average number of hydrolyzable silyl groups in one molecule of an organic polymer having a hydrolyzable silyl group can be measured by the following method: １ It can be calculated based on the concentration of hydrolyzable silyl groups in the organic polymer determined by H-NMR and the number average molecular weight of the polymer determined by GPC.

[0025] The method for introducing a hydrolyzable silyl group into an organic polymer is not particularly limited, and examples thereof include (1) a method in which an organic polymer modified with an unsaturated group in the molecule is subjected to hydrosilylation by the action of a hydrosilane having a hydrolyzable silyl group, (2) a method in which an organic polymer modified with an unsaturated group in the molecule is reacted with a compound having a mercapto group and a hydrolyzable silyl group, and (3) a method in which an organic polymer having a functional group in the molecule is reacted with a compound having a hydrolyzable silyl group and a functional group reactive with the functional group.Specific examples of the reaction that can be used include a reaction between an isocyanate group and a hydroxyl group, a reaction between an isocyanate group and an amino group, and a reaction between an isocyanate group and a mercapto group.

[0026] The organic polymer containing a hydrolyzable silyl group is not particularly limited, and examples thereof include polyalkylene oxides such as polyethylene oxide, polypropylene oxide, polybutylene oxide, polytetramethylene oxide, polyethylene oxide-polypropylene oxide copolymers, and polypropylene oxide-polybutylene oxide copolymers; saturated hydrocarbon polymers; polyurethanes; polychloroprene; polyisoprene; copolymers of isoprene or butadiene with acrylonitrile and / or styrene; polybutadiene; copolymers of isoprene or butadiene with acrylonitrile and styrene; (meth)acrylate polymers obtained by radical polymerization of monomers such as ethyl (meth)acrylate and butyl (meth)acrylate. Examples of such polymers include vinyl polymers obtained by radical polymerization of monomers such as vinyl acetate, acrylonitrile, and styrene, graft polymers obtained by polymerizing vinyl monomers into the above polymers, polysulfide polymers, nylon 6 obtained by ring-opening polymerization of ε-caprolactam, nylon 6,6 obtained by condensation polymerization of hexamethylenediamine and adipic acid, nylon 6,10 obtained by condensation polymerization of hexamethylenediamine and sebacic acid, nylon 11 obtained by condensation polymerization of ε-aminoundecanoic acid, nylon 12 obtained by ring-opening polymerization of ε-aminolaurolactam, polyamide polymers such as copolymer nylons containing two or more of the above nylon components, polycarbonate polymers produced by condensation polymerization of bisphenol A and carbonyl chloride, and diallyl phthalate polymers. In this specification, (meth)acrylate means methacrylate or acrylate.

[0027] Among these, polyalkylene oxides are preferred as organic polymers from the viewpoint of achieving desired ranges of shear adhesive strength and elongation at maximum stress after curing. That is, polyalkylene oxides having hydrolyzable silyl groups are preferred as organic polymers having hydrolyzable silyl groups. Among polyalkylene oxides, polypropylene oxide is particularly preferred.

[0028] The number average molecular weight (Mn) of the organic polymer containing hydrolyzable silyl groups is preferably 1,000 to 70,000, more preferably 1,000 to 40,000, even more preferably 1,500 to 30,000, even more preferably 2,000 to 30,000, even more preferably 4,000 to 30,000, and even more preferably 4,000 to 20,000. When the number average molecular weight of the organic polymer containing hydrolyzable silyl groups is below these upper limits, the viscosity of the resulting adhesive composition is reduced, improving the coatability of the curable adhesive composition for batteries. Furthermore, when the number average molecular weight of the organic polymer containing hydrolyzable silyl groups is above these lower limits, the cured product of the curable adhesive for batteries is prevented from becoming brittle, improving the hardness and elongation of the cured product. Note that when the adhesive composition contains multiple organic polymers containing hydrolyzable silyl groups, the number average molecular weight (Mn) refers to the number average molecular weight (Mn) of the entire adhesive composition.

[0029] In the present invention, the number average molecular weight of the organic polymer containing a hydrolyzable silyl group refers to a value measured by gel permeation chromatography (GPC) in terms of polystyrene. Measurement by GPC can be performed, for example, using an ACQUITY APC system manufactured by Waters Corporation, a Shodex KF604 GPC column manufactured by Tosoh Corporation, tetrahydrofuran as the solvent, a column temperature of 40° C., and a flow rate of 0.3 ml / min.

[0030] The polymer containing a hydrolyzable silyl group can be a commercially available product. For example, examples of polyalkylene oxide polymers having a polypropylene oxide main chain skeleton and a dimethoxysilyl group at the end of the main chain skeleton include those manufactured by Asahi Glass Co., Ltd. under the product names "Excestar A2410" and "Excestar S4530," and those manufactured by Kaneka Corporation under the product names "S203," "S327," "SAT350," "SAX010," and "SAX220."

[0031] <Thermally Conductive Filler> The first and second parts of the curable adhesive for batteries of the present invention, and the curable adhesive composition for batteries obtained by mixing the first and second parts, contain a thermally conductive filler.

[0032] The content of the thermally conductive filler in the curable adhesive composition for batteries is preferably 60 to 85% by volume, more preferably 65 to 80% by volume, and even more preferably 70 to 80% by volume. The content of the thermally conductive filler in each of the first and second parts is also preferably within these ranges. When the content of the thermally conductive filler is equal to or greater than these lower limits, the thermal conductivity of the cured product is increased, improving heat dissipation. On the other hand, when the content of the thermally conductive filler is equal to or less than these upper limits, the extensibility of the cured product is increased, making it easier to improve its ability to follow the expansion and contraction of the battery cell.

[0033] The thermally conductive filler preferably contains a thermally conductive filler having hydroxyl groups on its surface. The use of a thermally conductive filler having hydroxyl groups on its surface facilitates the reaction between the organic polymer containing the hydrolyzable silyl groups and the thermally conductive filler, increasing the interfacial strength between the organic polymer and the thermally conductive filler, resulting in improved elongation of the cured product. Examples of thermally conductive fillers having hydroxyl groups on their surface include metal oxides and metal hydroxides. Examples of metal oxides include aluminum oxide (e.g., alumina), magnesium oxide, and zinc oxide, with aluminum oxide being preferred. Examples of metal hydroxides include aluminum hydroxide, magnesium hydroxide, and zinc hydroxide, with aluminum hydroxide being preferred. It is preferable that the metal oxides and metal hydroxides are not surface-treated. This is because surface-treated fillers have fewer hydroxyl groups on their surface, making them less susceptible to reaction with the organic polymer. Therefore, untreated aluminum oxide is preferred as the metal oxide, and untreated aluminum hydroxide is preferred as the metal hydroxide. Note that the present invention does not preclude the use of surface-treated thermally conductive fillers. The surface treatment is carried out, for example, by reacting a surface treatment agent such as a silane coupling agent with the surface of the thermally conductive filler.

[0034] The content of the thermally conductive filler having hydroxyl groups on its surface relative to the total amount of the thermally conductive filler in the curable adhesive composition for batteries is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 95% by mass or more, and even more preferably 100% by mass. Furthermore, the content of the thermally conductive filler having hydroxyl groups relative to the total amount of the thermally conductive filler in each of the first and second parts is also preferably within such a range.

[0035] Among the thermally conductive fillers having a hydroxyl group, it is preferable that the thermally conductive filler contains a metal hydroxide from the viewpoint of increasing the shear adhesive strength and elongation at maximum stress of the cured product. In the curable adhesive composition for batteries, the sum of the surface areas of the metal hydroxides per 100 g of the organic polymer having a hydrolyzable silyl group is 200 to 1500 m ２ The sum of the surface areas of the metal hydroxides is preferably 200 to 1500 m ２ By setting the above-mentioned temperature to 100°C, the shear adhesive strength and elongation at maximum stress of the cured product are likely to be increased. The sum of the surface areas of the metal hydroxides is preferably 300 to 1200 m ２ and more preferably 500 to 1000 m ２ In addition, it is preferable that the sum of the surface areas of the metal hydroxides per 100 g of the organic polymer having a hydrolyzable silyl group in each of the first and second parts is also within the above range. The sum of the surface areas of the metal hydroxides per 100 g of the organic polymer having a hydrolyzable silyl group can be determined by the method described in the Examples.

[0036] The thermally conductive filler preferably contains small-particle aluminum hydroxide having an average particle size of 20 μm or less. By including small-particle aluminum hydroxide having an average particle size of 20 μm or less, it becomes easier to adjust the sum of the surface areas of the metal hydroxides to the above range, and the elongation of the cured product tends to be improved. The average particle size of the small-particle aluminum hydroxide is preferably 15 μm or less, more preferably 10 μm or less, and preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 5 μm or more. Two or more types of small-particle aluminum hydroxide having different average particle sizes may be used in combination. In this specification, the average particle size is the median diameter (D50) measured using a laser diffraction / scattering particle size distribution analyzer.

[0037] The thermally conductive filler may contain large-particle aluminum hydroxide having an average particle size of more than 20 μm. The proportion (volume %) of the small-particle aluminum hydroxide relative to the total amount of aluminum hydroxide in the curable adhesive composition for batteries is preferably 10 to 100 vol%, more preferably 25 to 100 vol%. It is also preferable that the proportions (volume %) of the small-particle aluminum hydroxide relative to the total amount of aluminum hydroxide in each of the first and second parts be within the same range.

[0038] The content of the metal hydroxide in the curable adhesive composition for batteries is preferably 10 to 80% by volume, more preferably 15 to 75% by volume, from the viewpoint of increasing the shear adhesive strength and elongation at maximum stress of the cured product. The content of the metal hydroxide in each of the first and second parts is also preferably within the same range.

[0039] From the viewpoint of improving the thermal conductivity of the cured product, the thermally conductive filler preferably contains aluminum oxide. Furthermore, it is more preferable that the thermally conductive filler contain both the aluminum hydroxide and aluminum oxide described above. This makes it easier to adjust the sum of the surface areas of the metal hydroxide per 100 g of the organic polymer having a hydrolyzable silyl group within the above range, thereby facilitating a balanced improvement in the thermal conductivity, adhesive strength, and elongation of the cured product. When the curable adhesive composition for batteries contains aluminum oxide, its content is preferably 10 to 70 vol%, more preferably 20 to 60 vol%. Furthermore, when both the first and second parts contain aluminum oxide, it is also preferable that the content of aluminum oxide be within the above range. The average particle size of the aluminum oxide is not particularly limited, but is, for example, 0.1 to 200 μm, preferably 0.5 to 150 μm, and more preferably 1 to 100 μm. Furthermore, aluminum oxides with different average particle sizes may be used in combination.

[0040] <Plasticizer> At least one of the first and second parts in the curable adhesive for batteries of the present invention, and the curable adhesive composition for batteries obtained by mixing the first and second parts, preferably contains a plasticizer. The inclusion of a plasticizer makes it easier to improve the elongation of the adhesive and to reduce the viscosity, thereby improving workability, etc.

[0041] Specific examples of plasticizers include organic ester plasticizers such as monobasic organic acid esters and polybasic organic acid esters, organic phosphoric acid plasticizers such as organic phosphoric acid plasticizers and organic phosphite plasticizers, and epoxy plasticizers such as sulfonamides and epoxidized soybean oil. Furthermore, the plasticizer is preferably an organic ester plasticizer. Examples of the monobasic organic acid ester include glycol esters obtained by reacting glycol with a monobasic organic acid. Examples of the glycol include triethylene glycol, tetraethylene glycol, and tripropylene glycol. Examples of the monobasic organic acid include butyric acid, isobutyric acid, caproic acid, 2-ethylbutyric acid, heptyl acid, n-octylic acid, 2-ethylhexyl acid, n-nonylic acid, decylic acid, and benzoic acid.

[0042] Examples of the polybasic organic acid ester include ester compounds of polybasic organic acids with alcohols having a linear or branched structure and 4 to 8 carbon atoms. Examples of the polybasic organic acids include adipic acid, sebacic acid, and azelaic acid. Examples of the organic ester plasticizer include triethylene glycol di-2-ethylpropanoate, triethylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylhexanoate, triethylene glycol dicaprylate, triethylene glycol di-n-octanoate, triethylene glycol di-n-heptanoate, tetraethylene glycol di-n-heptanoate, dibutyl sebacate, dioctyl azelate, dibutyl carbitol adipate, ethylene glycol di-2-ethylbutyrate, 1,3-propylene glycol di-2-ethylbutyrate, 1,4-butylene glycol di-2-ethylbutyrate, and diethylene glycol di-2-ethylbutylene. Examples of suitable organic ester plasticizers include ethylene glycol di-2-ethylhexanoate, dipropylene glycol di-2-ethylbutyrate, triethylene glycol di-2-ethylpentanoate, tetraethylene glycol di-2-ethylbutyrate, diethylene glycol dicaprylate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, dihexyl adipate, dioctyl adipate, hexylcyclohexyl adipate, a mixture of heptyl adipate and nonyl adipate, diisononyl adipate, diisodecyl adipate, heptylnonyl adipate, dibutyl sebacate, oil-modified alkyd sebacate, and a mixture of a phosphate ester and an adipate. Organic ester plasticizers other than these may also be used. Adipic acid esters other than the above-mentioned adipic acid esters may also be used.

[0043] Examples of the organic phosphoric acid plasticizer include tributoxyethyl phosphate, isodecylphenyl phosphate, and triisopropyl phosphate. The plasticizer is preferably a diester plasticizer represented by the following formula (1) or (2): In the above formula (1), R1 and R2 each represent an organic group having 2 to 10 carbon atoms, R3 represents an ethylene group, an isopropylene group, or an n-propylene group, and p represents an integer of 3 to 10. In the above formula (1), R1 and R2 each preferably represent an organic group having 5 to 10 carbon atoms, and more preferably represent an organic group having 6 to 10 carbon atoms. In the above formula (2), R4 and R5 each represent a hydrocarbon group having 3 to 10 carbon atoms, and R6 represents a hydrocarbon group having 2 to 10 carbon atoms. In the above formula (2), R4 and R5 each preferably have 4 to 9 carbon atoms, and more preferably have 6 to 9 carbon atoms. The hydrocarbon groups of R4 and R5 are preferably alkyl groups. The alkyl group may be linear or may have a branched structure. R6 preferably has 4 to 9 carbon atoms, and more preferably has 5 to 8 carbon atoms. The hydrocarbon group of R6 is preferably an aliphatic hydrocarbon group, and among these, an unsaturated aliphatic hydrocarbon group is more preferable. R6 may be linear or may have a branched or cyclic structure, and preferably has a cyclic structure.

[0044] The plasticizer preferably includes triethylene glycol di-2-ethylhexanoate (3GO), diisononyl 1,2-cyclohexanedicarboxylate (DINCH), triethylene glycol di-2-ethylbutyrate (3GH), or triethylene glycol di-2-ethylpropanoate. The plasticizer more preferably includes triethylene glycol di-2-ethylhexanoate (3GO), triethylene glycol di-2-ethylbutyrate (3GH), or diisononyl 1,2-cyclohexanedicarboxylate (DINCH), and even more preferably includes triethylene glycol di-2-ethylhexanoate or diisononyl 1,2-cyclohexanedicarboxylate.

[0045] From the viewpoint of reducing the viscosity of the first agent, the second agent, and the composition obtained by mixing these, the molecular weight of the plasticizer is preferably less than 1,000, more preferably less than 500, and preferably 50 or more, more preferably 100 or more. Furthermore, the molecular weight of the plasticizer is preferably 50 or more and less than 1,000, more preferably 100 or more and less than 500. When the structural formula of the plasticizer is known, the molecular weight is the molecular weight calculated from the structural formula; when the structural formula is unknown, it can be measured using a mass spectrometer (GC-MS or LC-MS).

[0046] The content of the plasticizer in the curable adhesive composition for batteries is preferably 10 to 200 parts by mass, more preferably 100 to 160 parts by mass, per 100 parts by mass of the organic polymer having a hydrolyzable silyl group. When the amount of plasticizer is above these lower limits, the viscosity of the composition decreases, improving workability. When the amount of plasticizer is below these upper limits, the amount of organic polymer can be kept above a certain level, ensuring a certain number of reaction points with the thermally conductive filler, and facilitating increased shear adhesive strength. Furthermore, it is preferable that the content of plasticizer in each of the first and second parts be within the above ranges.

[0047] <Silanol condensation catalyst> The first part of the curable adhesive for batteries of the present invention, and the curable adhesive composition for batteries obtained by mixing the first part and the second part, preferably contain a silanol condensation catalyst. It is preferable that the second part does not contain a silanol condensation catalyst. This is because, as described below, it is preferable to incorporate water into the second part. In this case, if a silanol condensation catalyst is further incorporated, a condensation reaction of the organic polymer having a hydrolyzable silyl group occurs during storage, resulting in a decrease in storage stability.

[0048] Examples of silanol condensation catalysts include organotin compounds such as dibutyltin dilaurate, dibutyltin oxide, dibutyltin diacetate, dibutyltin phthalate, bis(dibutyltin laurate)oxide, dibutyltin bis(acetylacetonate), dibutyltin bis(monoester maleate), tin octoate, dibutyltin octoate, dioctyltin oxide, dioctyltin diversatate, dioctyltin distearate, dibutyltin bis(triethoxysilicate), bis(dibutyltin bistriethoxysilicate)oxide, dibutyltin oxybisethoxysilicate, and 1,1,3,3-tetrabutyl-1,3-dilauryloxycarbonyl-distannoxane, and organotitanium compounds such as tetra-n-butoxytitanate and tetraisopropoxytitanate. These silanol condensation catalysts may be used alone or in combination of two or more. Of the above-mentioned silanol condensation catalysts, organotin compounds are preferred, and dibutyltin dilaurate is more preferred.

[0049] The content of the silanol condensation catalyst in the curable adhesive composition for batteries is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the organic polymer containing a hydrolyzable silyl group. The content of the silanol condensation catalyst in the first agent is also preferably within this range. When the content of the silanol condensation catalyst is equal to or greater than these lower limits, the curing rate can be increased, and when the content of the silanol condensation catalyst is equal to or less than these upper limits, a decrease in the storage stability of the composition can be suppressed.

[0050] <Adhesion Promoter> The first part of the curable adhesive for batteries of the present invention, and the curable adhesive composition for batteries obtained by mixing the first part and the second part, preferably contain an adhesion promoter. From the viewpoint of storage stability, it is preferable that the second part does not contain an adhesion promoter. The adhesion promoter can further improve the adhesiveness of the cured product of the curable adhesive composition for batteries.

[0051] As the adhesion promoter, an aminosilane coupling agent is preferred. Specific examples of the aminosilane coupling agent include 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N,N'-bis-[3-(trimethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(triethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(methyldimethoxysilyl)propyl]ethylenediamine, N,N'-bis-[3-(trimethoxysilyl)propyl]hexamethylenediamine, and N,N'-bis-[3-(triethoxysilyl)propyl]hexamethylenediamine. Of these, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane is preferred.

[0052] The content of the adhesion promoter in the curable adhesive composition for batteries is preferably 1 to 10 parts by mass, more preferably 1 to 5 parts by mass, per 100 parts by mass of the organic polymer containing a hydrolyzable silyl group. The content of the silanol adhesion promoter in the first part is also preferably within this range. When the content of the adhesion promoter is equal to or greater than these lower limits, the adhesive strength of the cured product formed is likely to be improved. When the content of the adhesion promoter is equal to or less than these upper limits, the cured product formed can be prevented from becoming brittle, thereby suppressing a decrease in adhesive strength.

[0053] <Water> The second part and the curable adhesive composition for batteries obtained by mixing the first and second parts preferably contain water. This allows for rapid curing throughout the composition after the first and second parts are mixed to prepare the curable adhesive composition for batteries. The content of water in the second part is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of the organic polymer having a hydrolyzable silyl group contained in the curable adhesive composition for batteries obtained by mixing the first and second parts. Similarly, the content of water in the curable adhesive composition for batteries is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of the organic polymer having a hydrolyzable silyl group.

[0054] <Dehydrating Agent> The first part and the battery curable adhesive composition obtained by mixing the first and second parts preferably contain a dehydrating agent. The inclusion of a dehydrating agent can prevent the first part from curing due to moisture in the air or the like during storage. Examples of dehydrating agents include silane compounds such as vinyltrimethoxysilane, dimethyldimethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, tetramethoxysilane, phenyltrimethoxysilane, and diphenyldimethoxysilane, and ester compounds such as methyl orthoformate, ethyl orthoformate, methyl orthoacetate, and ethyl orthoacetate. These dehydrating agents may be used alone or in combination. Among these, vinyltrimethoxysilane is preferred.

[0055] The content of the dehydrating agent in the first part is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the organic polymer having a hydrolyzable silyl group contained in the curable adhesive composition for batteries obtained by mixing the first part and the second part. When the content of the dehydrating agent is equal to or greater than these lower limits, curing during storage is easily suppressed, while when the content of the dehydrating agent is equal to or less than these upper limits, a decrease in curability due to the dehydrating agent can be prevented. Similarly, the content of the dehydrating agent in the curable adhesive composition for batteries is preferably 0.5 to 20 parts by mass, more preferably 1 to 10 parts by mass, per 100 parts by mass of the organic polymer having a hydrolyzable silyl group.

[0056] <Dispersant> At least one of the first and second parts in the battery curable adhesive of the present invention, and the battery curable adhesive composition obtained by mixing the first and second parts, may contain a dispersant. The inclusion of a dispersant facilitates a reduction in viscosity, improving workability, etc. Examples of dispersants include polymeric dispersants. Examples of polymeric dispersants include polymeric compounds having functional groups. Examples of polymeric compounds include acrylic, vinyl, polyester, polyurethane, polyether, epoxy, polystyrene, amino, and silicone compounds. Examples of functional groups include carboxyl groups, phosphate groups, sulfonic acid groups, carboxylic acid ester groups, phosphate ester groups, sulfonic acid ester groups, hydroxyl groups, amino groups, quaternary ammonium bases, and amide groups. Dispersants other than polymeric dispersants may also be used, such as alkoxysilane compounds.

[0057] The content of the dispersant in the curable adhesive composition for batteries is preferably 0.1 to 20 parts by mass, more preferably 0.5 to 15 parts by mass, per 100 parts by mass of the organic polymer having a hydrolyzable silyl group. The contents of the dispersant in each of the first and second parts are also preferably within the above ranges.

[0058] <Others> In the present invention, the first part, the second part, and the curable adhesive composition for batteries obtained by mixing these may contain other additives such as a thixotropic agent, an antioxidant, an ultraviolet absorber, a pigment, a dye, an anti-settling agent, and a solvent.

[0059] <Mass ratio and viscosity of first and second agents> The mass ratio of the first agent to the second agent (second agent / first agent) is preferably 1 or a value close to 1, specifically preferably 0.9 to 1.1, and more preferably 0.95 to 1.05. In this way, by setting the mass ratio of the first agent to the second agent to a value close to 1, it becomes easy to prepare a mixture of the first agent and the second agent.

[0060] The viscosity η1 of the first part at 25°C and a shear rate of 1 (1 / sec) is preferably 100 to 1000 Pa·s, more preferably 130 to 980 Pa·s. The viscosity η2 of the second part at 25°C and a shear rate of 1 (1 / sec) is preferably 100 to 1000 Pa·s, more preferably 130 to 980 Pa·s. When the viscosities of the first and second parts are within the above ranges, they are easy to handle. Furthermore, the absolute value of the difference between the viscosity η1 and the viscosity η2 is preferably 400 Pa·s or less, more preferably 300 Pa·s or less, and even more preferably 200 Pa·s or less. Such a small difference between the viscosity η1 and the viscosity η2 facilitates mixing of the first and second parts, making it easier to obtain a highly uniform composition. The lower limit of the absolute value of the difference between the viscosity η1 and the viscosity η2 is 0 Pa·s. The above viscosities η1 and η2 are measured by a rheometer, and the details are as described in the Examples.

[0061] The first agent and the second agent are filled in separate containers, specifically, the first agent is filled in the first container and the second agent is filled in the second container. The first container and the second container may be separate or integrated. By integrating the first container and the second container, it becomes easier to supply the container set to the consumer. In this specification, the first container filled with the first agent and the second container filled with the second agent may be collectively referred to as a container set.

[0062] Examples of containers include, but are not limited to, syringes, cartridges, pails, drums, and the like. For example, when filling a syringe, it is preferable to use a two-liquid parallel type syringe. As shown in FIG. 1 , a two-liquid parallel type syringe 30 is an integrated syringe in which a first syringe 31 constituting a first container and a second syringe 32 constituting a second container are arranged in parallel. The first agent 35 and the second agent 36 filled in the syringes 31 and 32 are preferably discharged from the syringes as dispensers and mixed.

[0063] When cartridges are used, the container set comprises a first cartridge constituting the first container and a second cartridge constituting the second container, and these cartridges may be integrated. The cartridges are usually set in syringes (e.g., a first syringe and a second syringe), and the first agent delivered from the first cartridge and the second agent delivered from the second cartridge are preferably discharged from the respective outlets of the first syringe and the second syringe, using each syringe as a dispenser, and then mixed.

[0064] The first and second agents may be mixed using a mixer such as a static mixer. As shown in FIG. 1 , the static mixer 38 is connected to the outlet 31A of the first syringe 31 and the outlet 32A of the second syringe 32, and the first agent 35 and the second agent 36 discharged from the outlets 31A and 32A can be mixed inside the mixer 38. The mixture (curable composition) obtained by mixing in the mixer 38 may be discharged from the outlet 39 of the mixer 38. Each syringe 31, 32 may have a structure in which the openings of barrels 33A, 34A, into which the first agent 35 and the second agent 36, respectively, are filled, are closed by lids 33B, 34B. In the syringe 30 shown in FIG. 1, the first agent 35 and the second agent 36 are preferably ejected from the respective outlets 31A and 32A after the respective lids 33B and 34B are removed and the first agent 35 and the second agent 36 are pushed out by pistons (not shown) inserted from the openings.

[0065] 2, the container set may include a first pail 41 that constitutes the first container and is filled with a first agent 45, and a second pail 42 that constitutes the second container and is filled with a second agent 46. Each pail 41, 42 includes, for example, a container body 43A, 44A that has an opening and is filled with the first agent 45 and the second agent 46, and a lid 43B, 44B that closes the opening of each container body 43A, 44B.

[0066] [Battery Structure] The battery structure of the present invention includes a structure and a plurality of cells arranged on the structure, and an adhesive layer is arranged at least one between the structure and the cells or between the plurality of cells. The adhesive layer is a cured product of a curable adhesive composition for batteries, which comprises an organic polymer having a hydrolyzable silyl group and a thermally conductive filler, and the cured product has a shear adhesive strength of 0.5 to 2.5 MPa, a maximum stress elongation of 0.3 mm or more at a thickness of 2 mm, and a thermal conductivity of 1.5 W / m·K or more.

[0067] The cured product constituting the adhesive layer in the battery structure is the above-described curable adhesive composition for batteries. The components contained in the curable adhesive composition for batteries are as described above. The shear adhesive strength, elongation at maximum stress, and thermal conductivity of the cured product of the curable adhesive composition for batteries are also as described above.

[0068] The structural body includes various components that form a battery structure, such as a substrate for connecting cells, a battery pack case, a battery module case, a cooling plate, a water-cooled plate, etc. The cured product of the curable adhesive for batteries or the curable adhesive composition for batteries of the present invention can be used as at least one of the gap materials between battery cells, between a battery cell and a module housing, between a battery module and a battery pack housing, and between a battery cell and a battery pack housing. Specific examples of the battery structure of the present invention will be described below.

[0069] 3 shows a battery structure (battery module) 10 including a battery module case (housing) 11 and a plurality of cells 12 arranged within the case 11. The cells 12 are arranged with their flat surfaces facing each other. Adhesive layers 13, which are cured products of a curable adhesive composition for batteries, are fixed between the plurality of cells 12 at intervals A.

[0070] The cell 12 is a structural unit of a lithium-ion secondary battery or the like, and generally comprises an exterior film and battery elements (not shown) enclosed within the exterior film. Examples of battery elements include a positive electrode, a negative electrode, a separator, and an electrolyte. As shown in FIG. 4 , the cell 12 is a flat body having a thickness smaller than its width, with the positive electrode 12 a and the negative electrode 12 b exposed to the outside, and the flat surface 12 c being thicker than the crimped end 12 d. While the cell 12 is described as a laminated cell using an exterior film, rectangular or cylindrical cells may also be used in addition to the laminated cell.

[0071] 5, the adhesive layer 13 can also be provided between the case 11 and the cell 12 at a position B. The adhesive layer 13 is provided at least one of between the case 11 and the cell 12 at a position B and between the plurality of cells 12 at a position A. Although not shown, the adhesive layer 13 may be provided both between the case 11 and the cell 12 at a position B and between the plurality of cells 12 at a position A.

[0072] 6 shows a battery structure (battery pack) 20 including a battery pack case (housing) 14 and a plurality of battery modules 10 arranged in the battery pack case 14. Adhesive layers 13 are fixed between the plurality of battery modules 10 at C.

[0073] 6, the adhesive layer 13 is also adhered to a gap D between the battery pack case 14 and the battery module 10. Although Fig. 6 shows an embodiment in which the adhesive layer 13 is adhered to both the gap D between the battery pack case 14 and the battery module 10 and the gaps C between the plurality of battery modules 10, the adhesive layer 13 may be adhered to at least one of the gaps D between the battery pack case 14 and the battery module 10 and the gaps C between the plurality of battery modules 10. Furthermore, Fig. 6 shows an embodiment in which the adhesive layer 13 is not used inside the battery module 10, but the adhesive layer 13 may also be provided inside the battery module 10 arranged inside the battery pack as shown in Figs. 3 and 5.

[0074] 7 schematically shows a battery structure 30 in a battery module without a housing. The battery structure 30 includes a plurality of battery cells 12 and a cooling plate 15. The plurality of battery cells 12 are bonded to the cooling plate 15 via an adhesive layer 13, which is a cured product of a curable adhesive composition for batteries.

[0075] The adhesive layer, which is the cured product of the curable adhesive composition for batteries of the present invention, has moderate adhesive strength, so it can secure each structure and cell, or each cell to another, ensuring a certain strength, and can be peeled off as needed. Since excessive stress is not generated during peeling, deformation of the structure or cell does not occur, resulting in excellent recyclability. Furthermore, the cured product (adhesive layer) has high thermal conductivity and good elongation, and is also excellent in shape-following ability to expand and contract cells, etc.

[0076] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0077] In this example, the evaluation was carried out by the following method.

[0078] [Shear Adhesion Strength, Elongation at Maximum Stress] Shear adhesive strength and elongation at maximum stress were measured according to the tensile shear test of JIS K6850:1999. Two substrates (KTL boards (manufactured by Nippon Test Panel Co., Ltd., "Material: SPCC-SD, Specifications: Cationic Electrodeposition Coating (Black)")) measuring 100 mm in length, 25 mm in width, and 2 mm in thickness were prepared. The tips of the substrates were arranged so that they overlapped each other by a length of 25 mm x 25 mm. A curable adhesive composition for batteries, consisting of equal amounts of a first part and a second part (1:1 by mass), was applied to the overlapping portion of the substrates so that the thickness of the cured product was 2 mm. The cured adhesive composition was then cured at 25°C and 50% RH for two weeks to prepare a measurement sample. A tensile test was performed on the above measurement samples using a tensile tester (TENSILON RTC-1310A manufactured by A&D Co., Ltd.) at room temperature of 25°C and a tensile speed of 10 mm / min to measure the tensile shear strength. The maximum stress in the obtained stress curve was taken as the shear adhesive strength. The shear tensile strength test was also performed, and the displacement at which the tensile stress reached its maximum value was taken as the elongation at maximum stress (mm).

[0079] [Viscosity] The viscosity (Pa s) of each of the first and second parts at 25°C was measured using a rheometer (for example, an Anton Paar MCR-302e rheometer). The sample temperature was adjusted to 25°C using a Peltier plate, and viscosity was measured using φ20 mm parallel plates with a gap of 1 mm while continuously changing the shear rate within the range of 0.0001 to 100 (1 / sec). The viscosity (Pa s) value was the viscosity at a shear rate of 1 (1 / s).

[0080] [Two-component] The battery curable adhesives in each example and comparative example were evaluated as follows: A: Both the first and second parts had properties that allowed viscosity measurement, and were two-component. B: Viscosity measurement of one or both of the first and second parts was not possible, and they were not two-component.

[0081] [Thermal Conductivity] A battery curable adhesive composition was prepared by mixing equal amounts of the first and second components (1:1 by mass), and the cured product was cured at 25°C and 50% RH for two weeks. The thermal conductivity was measured using a cured product. The thermal conductivity was determined by measuring thermal resistance using a measuring device conforming to ASTM D5470-06. Specifically, cured products with thicknesses of 1.0 mm, 1.5 mm, and 2.0 mm were prepared, and the thermal resistance and thickness were measured when compressed at a pressure of 30 psi. A graph was created for these three thermal resistance values, with the horizontal axis representing thickness and the vertical axis representing thermal resistance. A three-point approximation line was then obtained using the least squares method. The slope of the approximation line represents the thermal conductivity. Thermal resistance measurements were performed at 80°C using an LW-9389 thermocouple manufactured by Long Win Science and Technology Corporation.

[0082] [Observation of Breakage Morphology] After the above-described measurement of shear adhesive strength, the test piece was observed to observe the breakage morphology of the cured product (adhesive layer).

[0083] <Overall evaluation> A: Thermal conductivity of 1.5 W / mK or higher, shear bond strength of 0.7 to 2.5 MPa, and elongation at maximum stress of 0.4 mm or higher. B: Thermal conductivity of 1.5 W / mK or higher, and although either shear bond strength or elongation at maximum stress does not satisfy the requirement of A above, the shear bond strength is 0.5 to 2.5 MPa and the elongation at maximum stress is 0.3 mm or higher. C: Any of the following applies: Thermal conductivity less than 1.5 W / mK, shear bond strength less than 0.5 MPa, and elongation at maximum stress less than 0.3 mm.

[0084] The components used in the examples are as follows.

[0085] <Organic polymers having hydrolyzable silyl groups> Kaneka Corporation's "MS polymer SAX010", number average molecular weight 2,400, linear type, terminal silylation rate 94%, organic polymer having dimethoxymethylsilyl groups at both ends of polypropylene oxide Kaneka Corporation's "MS polymer SAT115", number average molecular weight 3,400, linear type, terminal silylation rate 60%, organic polymer having dimethoxymethylsilyl groups at both ends of polypropylene oxide Kaneka Corporation's "MS polymer SAT350", number average molecular weight 6,800, linear type, terminal silylation rate 91%, organic polymer having dimethoxymethylsilyl groups at both ends of polypropylene oxide AGC Corporation's "S4530", number average molecular weight 25,000, linear type, terminal silylation rate 86%, organic polymer having dimethoxymethylsilyl groups at both ends of polypropylene oxide

[0086] <Thermal conductive filler> Aluminum hydroxide 1 (surface untreated, irregular shape, average particle size 90 μm, specific gravity 2.4 g / cm ３ ) Aluminum hydroxide 2 (surface untreated, irregular shape, average particle size 50 μm, specific gravity 2.4 g / cm ３ ) Aluminum hydroxide 3 (no surface treatment, irregular shape, average particle size 10 μm, specific gravity 2.4 g / cm ３ ) Aluminum hydroxide 4 (no surface treatment, irregular shape, average particle size 1 μm, specific gravity 2.4 g / cm ３ ) Aluminum hydroxide 5 (surface untreated, irregular shape, average particle size 105 μm, specific gravity 2.4 g / cm ３ ) Aluminum oxide 1 (no surface treatment, spherical, average particle size 70 μm, specific gravity 3.94 g / cm ３ ) Aluminum oxide 2 (surface untreated, spherical, average particle size 50 μm, specific gravity 3.94 g / cm ３ ) Aluminum oxide 3 (no surface treatment, spherical, average particle size 10 μm, specific gravity 3.94 g / cm ３ ) Aluminum oxide 4 (surface untreated, spherical, average particle size 3 μm, specific gravity 3.94 g / cm ３ ) Aluminum oxide 5 (surface untreated, spherical, average particle size 43 μm, specific gravity 3.94 g / cm ３) Aluminum oxide 6 (surface untreated, spherical, average particle size 12.5 μm, specific gravity 3.94 g / cm ３ )

[0087] <Plasticizer> Triethylene glycol di(2-ethylhexanoate) 3GO 1,2-cyclohexanedicarboxylic acid diisononyl ester DINCH

[0088] <Additives> Silanol condensation catalyst: dibutyltin dilaurate Silanol condensation catalyst 2: dioctyltin diversatate, trade name "U-830", manufactured by Nitto Kasei Co., Ltd. Water Dehydrating agent: vinyltrimethoxysilane Adhesion promoter: N-(2-aminoethyl)-3-aminopropyltrimethoxysilane Dispersant: "DISPERBYK-106" manufactured by BYK-Chemie Compatibilizer: butyl carbitol Antioxidant: SOGNOX1010 manufactured by Songwon

[0089] <Calculation of the sum of the surface areas of metal hydroxides> The sum of the surface areas of metal hydroxides (m ２ ) is the surface area (m) per gram of each metal hydroxide to be added. ２ For example, the surface area (m / g) per 1 g of metal hydroxide having an average particle size of A μm was calculated based on the surface area (m / g) per 1 g of metal hydroxide. ２ / g) is calculated according to the following formula (1): ２ / g) = surface area of ​​one particle (m ２ / particle) / volume of one particle (m ３ / particle) / specific gravity (g / cm ３ ) / 10 －６ Formula (1) In formula (1), the surface area of ​​one particle (m ２ / particle) is "4 × π × (A / 2) ２ x10 －１２ In formula (1), the volume of one particle (m ３ / particle) is "(4 / 3) × π × (A / 2) ３ x10 －１8 " where π is the constant of the circumference of a circle.

[0090] Example 1 A first part was prepared by mixing an organic polymer having a hydrolyzable silyl group (MS polymer SAT350), aluminum hydroxide 1, aluminum hydroxide 4, aluminum oxide 2, aluminum oxide 3, a plasticizer, a silanol condensation catalyst, a dehydrating agent, an adhesion promoter, a dispersant, and an antioxidant according to the formulation in Table 1. A second part was prepared by mixing an organic polymer having a hydrolyzable silyl group (MS polymer SAT350), aluminum hydroxide 1, aluminum hydroxide 4, aluminum oxide 2, aluminum oxide 3, a plasticizer, water, and a dispersant according to the formulation in Table 1. In this manner, a curable adhesive for batteries composed of the first part and the second part was obtained.

[0091] [Examples 2 to 10, Reference Examples 1 and 2, Comparative Examples 1 to 6] A curable adhesive for batteries composed of a first agent and a second agent was obtained in the same manner as in Example 1, except that the type and amount of each component was changed according to Table 1, Table 1-2, and Table 1-3.

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] The battery curable adhesive of each example was composed of a first part and a second part containing an organic polymer having a hydrolyzable silyl group and a thermally conductive filler. The first and second parts each had an appropriate viscosity range, allowing for use as a two-component adhesive. Furthermore, the shear adhesive strength of the cured product obtained by curing the battery curable adhesive composition obtained by mixing these first and second parts was 0.5 to 2.5 MPa, the elongation at maximum stress was 0.3 mm or more, and the thermal conductivity was 1.5 W / m·K or more. That is, the battery curable adhesive of each example had a high thermal conductivity of 1.5 W / m·K or more and excellent heat dissipation properties. Furthermore, the elongation at maximum stress was high, 0.3 mm or more, and the battery cell expansion and contraction response was also excellent. Furthermore, the shear adhesive strength of 0.5 to 2.5 MPa allowed the cured product to secure the components forming the battery structure with appropriate adhesive strength, and the cured product did not require excessive stress when peeling, resulting in excellent peelability.

[0098] The battery curable adhesive of Reference Example 1 satisfied the specified values ​​of the present invention for shear bond strength, elongation at maximum stress, and thermal conductivity. However, the compositions of the first and second parts were significantly different, such as the first part containing an organic polymer with a hydrolyzable silyl group and the first part containing a small amount of plasticizer (diluent). As a result, the viscosity difference between the two parts was large and the handling was poor. Similarly, the battery curable adhesive of Reference Example 2, like Reference Example 1, had a significantly different composition between the first and second parts, resulting in a large viscosity difference between the two parts and poor handling. Furthermore, the battery curable adhesive of Reference Example 2 had a low terminal silylation rate of the organic polymer, which resulted in low reactivity with thermally conductive fillers containing hydroxyl groups and poor shear bond strength. In Reference Examples 1 and 2, it is conceivable to reduce the viscosity difference by changing the formulation of the thermally conductive filler between the first and second agents, but in that case, the degree of freedom in design would be reduced, as only organic polymers with low viscosity could be used in the first agent, which has a smaller amount of plasticizer. Furthermore, from the perspective of reducing viscosity, it is conceivable to increase the proportion of alumina, which has high thermal conductivity, and reduce the total amount of thermally conductive filler, but in this case, the amount of aluminum hydroxide would be reduced, which is thought to make the shear adhesive strength more likely to decrease.

[0099] The battery curable adhesive of Comparative Example 1 had low shear adhesive strength and was unable to secure the components that form the battery structure with appropriate adhesive strength. This is thought to be because the sum of the surface areas of the metal hydroxides per 100 g of organic polymer was smaller than in the Examples. The battery curable adhesive of Comparative Example 2 also had low shear adhesive strength and was unable to secure the components that form the battery structure with appropriate adhesive strength. This is thought to be because the molecular weight of the organic polymer containing hydrolyzable silyl groups used in Comparative Example 2 was relatively high, resulting in a low concentration of reaction sites with the thermally conductive filler containing hydroxyl groups. The battery curable adhesives of Comparative Examples 3 and 6 also had low shear adhesive strength and were unable to secure the components that form the battery structure with appropriate adhesive strength. This is thought to be because the organic polymer containing hydrolyzable silyl groups used in Comparative Example 3 and 6 had a low terminal silylation rate, resulting in a low concentration of reaction sites with the thermally conductive filler containing hydroxyl groups. Comparative Examples 4 and 5 had low elongation at maximum stress, resulting in poor compliance with the expansion and contraction of the battery cell. This is thought to be because the sum of the surface areas of the metal hydroxides per 100 g of the organic polymer is large due to the incorporation of a large amount of aluminum hydroxide with a small particle size.

[0100] REFERENCE SIGNS LIST 10 Battery structure 11 Battery module case 12 Cell 12a Positive electrode 12b Negative electrode 12c Flat surface 12d End 13 Adhesive layer 14 Battery pack case 15 Cooling plate 20 Battery structure 30 Syringe 31 First syringe 31A First syringe outlet 32 ​​Second syringe 32A Second syringe outlet 33A, 34A Barrel 33B, 34B Barrel lid 35, 45 First agent 36, 46 Second agent 38 Mixer 39 Mixer outlet 40 Battery structure 41 First pail 42 Second pail 43A, 44A Container body with opening 43B, 44B Lid for closing the opening of the container body

Claims

1. A curable adhesive for batteries, comprising a first part which contains a silanol condensation catalyst and a thermally conductive filler and is filled in a first container, and a second part which contains an organic polymer having a hydrolyzable silyl group and a thermally conductive filler and is filled in a second container, wherein the first and second parts are mixed together to form a curable adhesive composition for batteries, and the composition is allowed to cure for two weeks in an environment of 25°C and 50% RH, resulting in a cured product having a shear adhesive strength of 0.5 to 2.5 MPa in a tensile shear test, an elongation at maximum stress of 0.3 mm or more in a tensile shear test with a thickness of 2 mm, and a thermal conductivity of the cured product of 1.5 W / m・K or more.

2. The curable adhesive for batteries according to claim 1, wherein the content of the thermally conductive filler in the curable adhesive composition for batteries is 60 to 85 volume %, and the thermally conductive filler contains a thermally conductive filler having hydroxyl groups on the surface.

3. The content of the thermally conductive filler in the curable adhesive composition for batteries is 60 to 85 volume %, the thermally conductive filler contains a metal hydroxide, and the sum of the surface areas of the metal hydroxide per 100 g of an organic polymer having a hydrolyzable silyl group in the curable adhesive composition for batteries is 200 to 1500 m ２ The curable adhesive for batteries according to claim 1 or 2, 4. The curable adhesive for batteries according to claim 1 or 2, wherein the first agent further contains an organic polymer having a hydrolyzable silyl group.

5. The curable adhesive for batteries according to claim 1 or 2, wherein the second part further contains water.

6. The curable adhesive for batteries according to claim 3, wherein the content of the metal hydroxide in the curable adhesive composition for batteries is 10 to 80 volume %.

7. The curable adhesive for a battery according to claim 3, wherein said metal hydroxide is aluminum hydroxide.

8. The curable adhesive for a battery according to claim 3, wherein the metal hydroxide is aluminum hydroxide that is not surface-treated.

9. The curable adhesive for batteries according to claim 1 or 2, wherein the thermally conductive filler comprises small particle size aluminum hydroxide having an average particle size of 20 μm or less.

10. The curable adhesive for batteries according to claim 1 or 2, wherein the organic polymer having a hydrolyzable silyl group is a polyalkylene oxide having a hydrolyzable silyl group.

11. The curable adhesive for batteries according to claim 1 or 2, wherein the organic polymer having a hydrolyzable silyl group has a hydrolyzable silyl group at the end of a linear main chain.

12. The curable adhesive for batteries according to claim 1 or 2, wherein the organic polymer having a hydrolyzable silyl group has a number average molecular weight (Mn) of 1,000 to 40,000.

13. The curable adhesive for batteries according to claim 1 or 2, wherein at least one of the first and second parts further contains a plasticizer.

14. A curable adhesive for batteries as described in claim 1 or 2, wherein the viscosity η1 (25°C, shear rate 1 (1 / sec)) of the first agent is 100 to 1000 Pa·s, the viscosity η2 (25°C, shear rate 1 (1 / sec)) of the second agent is 100 to 1000 Pa·s, and the absolute value of the difference between the viscosity η1 and the viscosity η2 is 400 Pa·s or less.

15. A battery structure comprising a structure and a plurality of cells arranged on the structure, wherein an adhesive layer is arranged at least either between the structure and the cells or between the plurality of cells, the adhesive layer being a cured product of a curable adhesive composition for batteries comprising an organic polymer having a hydrolyzable silyl group and a thermally conductive filler, the cured product having a shear adhesive strength of 0.5 to 2.5 MPa in a tensile shear test, a maximum stress elongation of 0.3 mm or more in a tensile shear test with a thickness of 2 mm, and a thermal conductivity of 1.5 W / m K or more.

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