Composite member and energy storage device
Patent Information
- Application Number
- PCT/JP2026/012230
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-27
- Filing Date
- 2026-03-25
- Publication Date
- 2026-10-01
Smart Images
Figure JP2026012230_01102026_PF_FP_ABST
Abstract
Description
Composite components and energy storage devices
[0001] The present invention relates to a composite member and an energy storage device in which an insulating coating is applied to a base material.
[0002] Conductive components, which have an insulating coating formed on the surface of a metal piece, are used to electrically connect parts. For example, various electronic devices, electric vehicles or hybrid vehicles driven by electric motors, and storage batteries are equipped with energy storage devices in which multiple battery cells are connected in series or parallel using busbars, which are conductive components. Furthermore, lithium-ion secondary batteries, which offer higher capacity and higher output compared to lead-acid batteries and nickel-metal hydride batteries, are mainly used as battery cells.
[0003] In battery cells, overcurrents can flow during charging and discharging, causing the busbars to overheat and, in some cases, even emit flames. For example, Patent Document 1 describes a busbar in which a ceramic tape, such as mica tape, is wrapped around a copper busbar body as a fire-resistant layer.
[0004] Furthermore, busbars are required to be insulating to prevent fires and equipment failures caused by short circuits. Patent Document 2 discloses a busbar used to electrically connect a battery module to other external equipment. In the busbar described in Patent Document 2, mounting holes are formed at both ends of an aluminum body, and the outer surface of the body is covered with an insulating layer formed by a dipping insulation treatment.
[0005] Chinese Utility Model No. 216902355 Specification, Chinese Utility Model No. 218731641 Specification
[0006] However, Patent Document 1 requires the ceramic tape to be wrapped around the busbar body. Due to spatial constraints at the battery cell installation location, the busbar may have a complex shape, and when the busbar has a complex shape, it is difficult to wrap the ceramic tape around every corner of the busbar body. If there are uneven wrapping or gaps in the ceramic tape, sufficient insulation and heat resistance cannot be obtained. Furthermore, it is possible that the adhesive surface of the ceramic tape will peel off. Moreover, although nylon tape is wrapped around the outside of the mica tape as an insulating layer, nylon tape has problems with heat resistance and will be damaged by heat, making it impossible to maintain the desired insulation.
[0007] Furthermore, forming an insulating layer by dipping insulation, as described in Patent Document 2, eliminates the need for wrapping ceramic tape and has the advantage of easily accommodating complex busbar shapes. However, as described in Patent Document 2, forming an insulating layer by dipping insulation can lead to the insulating layer becoming thinner at corners, for example, making insulation failures at corners more likely.
[0008] In recent years, battery capacity has increased, and consequently, the demand for improved safety has also risen. To meet this demand, when forming an insulating coating by painting, it is conceivable to make the insulating layer thicker overall or to laminate multiple layers to improve functions such as insulation and heat resistance. However, insulating coatings with a laminated structure are prone to peeling and cracking, especially at high temperatures (during thermal runaway), making it difficult to ensure safety.
[0009] As mentioned above, busbars require excellent insulation and heat resistance. Furthermore, not only busbars, but also conductive components and their surrounding components such as connectors, battery module protective parts, electronic component cases, battery cells, battery modules, battery packs, and motor coils are required to have both excellent insulation and heat resistance.
[0010] The present invention has been made in view of the above problems, and aims to provide a composite material that does not require winding work like ceramic tape, does not produce uneven winding or gaps, can easily accommodate complex shapes, has excellent insulation and heat resistance, and is particularly resistant to peeling and cracking at high temperatures, and can maintain its insulation properties. Furthermore, the present invention aims to provide an energy storage device in which multiple battery cells or battery modules are connected by a composite material in which peeling of the insulating coating is suppressed, thereby exhibiting high safety even in the event of an abnormality.
[0011] The above objective of the present invention is achieved by the configuration of the composite member described in [1] below.
[0012] [1] A composite member comprising a base material, an insulating film covering at least a portion of the surface of the base material, and a resin layer covering at least a portion of the surface of the insulating film, wherein the insulating film comprises a matrix containing a compound having siloxane bonds and an inorganic material dispersed in the matrix, and the resin layer comprises a resin different from the material constituting the matrix, and when an interfacial strength test is performed between the insulating film and the base material with reference to GB / T 5210-2006 to measure the tensile stress TS1 [MPa] at the time of fracture of the insulating film, and when an interfacial strength test is performed between the resin layer and the insulating film to measure the tensile stress TS2 [MPa] at the time of fracture of the resin layer, both of the following formulas (1) and (2) are satisfied: Formula (1): TS2 < (1 / 3) × TS1 Formula (2): 0 [MPa] < TS2 < 0.50 [MPa]
[0013] Furthermore, preferred embodiments of the present invention relating to composite members are described in [2] to
[14] below.
[0014] [2] The composite member according to [1], characterized in that the resin layer, when heated from room temperature at a heating rate of 10°C / min in an atmospheric atmosphere, exhibits a weight loss rate at 500°C that is higher than 65% by weight, as determined by thermogravimetric analysis.
[0015] [3] The composite member according to [1] or [2], characterized in that the insulating coating, when heated from room temperature at a heating rate of 10°C / min in an atmospheric atmosphere, has a weight loss rate of less than 15% by weight at 500°C, as determined by thermogravimetric analysis.
[0016] [4] The composite member according to any one of [1] to [3], characterized in that the resin layer has a thermal decomposition temperature of less than 560°C when heated in an atmospheric atmosphere, as determined by thermogravimetric differential thermal analysis.
[0017] [5] The composite member according to any one of [1] to [4], characterized in that the thickness of the insulating coating is 150 μm or more and 800 μm or less.
[0018] [6] The composite member according to any one of [1] to [5], characterized in that the thickness of the resin layer is 100 μm or more and 600 μm or less.
[0019] [7] The composite member according to any one of [1] to [6], characterized in that the compound having a siloxane bond is at least one selected from silicone and silica sol.
[0020] [8] The composite member according to any one of [1] to [7], characterized in that the inorganic material includes at least one selected from silica, alumina, calcium carbonate, mullite, and zirconia.
[0021] [9] The composite member according to any one of [1] to [7], characterized in that the inorganic material includes at least one selected from glass-based materials, mica, kaolin, talc, clay, pyrophyllite, montmorillonite, bentonite, wollastonite, xonotlite, zeolite, diatomaceous earth, and halloysite.
[0022]
[10] The composite member according to any one of [1] to [9], characterized in that the inorganic material includes at least one selected from flake, fibrous and particulate.
[0023]
[11] The composite member according to any one of [1] to
[10] , characterized in that the inorganic material includes at least one of a flake-shaped glass material and mica.
[0024]
[12] The composite member according to any one of [1] to
[11] , characterized in that the resin layer includes at least one selected from nylon resin, styrene-butadiene rubber, silicone rubber, polyvinyl chloride, and epoxy resin.
[0025]
[13] The composite member according to any one of [1] to
[12] , characterized in that it is applied to a busbar that connects multiple battery cells or battery modules.
[0026]
[14] The composite member according to any one of [1] to
[12] , characterized in that it is applied to a connector, a protective component for a battery module, a case for an electronic component, a battery cell, a battery module, a battery pack, or a coil for a motor.
[0027] The above objective of the present invention is achieved by the configuration of the energy storage device described in
[15] below.
[0028]
[15] A power storage device characterized in that a plurality of battery cells or battery modules are connected by a composite member described in any one of [1] to
[12] .
[0029] The composite member of the present invention has an insulating coating that covers at least a portion of the surface of a base material and a resin layer that covers at least a portion of the surface thereof. Since the materials of the insulating coating and the resin layer are selected so that the tensile stress of the insulating coating and the resin layer are in a predetermined relationship, it is possible to suppress the simultaneous peeling of the insulating coating and the resin layer even when exposed to high temperatures, thereby ensuring good insulation and heat resistance. Furthermore, since the energy storage device of the present invention is equipped with a composite member that has good insulation and heat resistance even when exposed to high temperatures, safety can be maintained over a long period of time.
[0030] Figure 1 is a cross-sectional view showing a composite member according to an embodiment of the present invention. Figure 2 is a schematic diagram showing an interface strength test method between a resin layer and an insulating coating applied in this embodiment. Figure 3 is a schematic diagram showing an interface strength test method between an insulating coating and a substrate applied in this embodiment. Figure 4 is a perspective view showing a busbar to which the composite member according to this embodiment is applied. Figure 5 is a schematic diagram showing an energy storage device according to an embodiment of the present invention. Figure 6 is a graph showing the TG-DTA analysis results when PVC is formed as the resin layer. Figure 7 is a graph showing the TG-DTA analysis results when SBR is formed as the resin layer. Figure 8 is a graph showing the TG-DTA analysis results when epoxy resin is formed as the resin layer by powder coating. Figure 9 is a graph showing the TG-DTA analysis results when an insulating coating W02 is formed. Figure 10 is a graph showing the TG-DTA analysis results when an insulating coating P05 is formed.
[0031] The inventors diligently conducted research to obtain a composite material that can maintain its insulating properties even at high temperatures without the need to use insulating tapes such as ceramic tapes, and without the insulating coating peeling off. As a result, they found that the above problem can be solved by having an insulating coating that covers at least a portion of the surface of the substrate and a resin layer that covers at least a portion of the surface thereof, and by selecting the materials of the insulating coating and the resin layer so that the tensile stresses of the insulating coating and the resin layer are in a predetermined relationship.
[0032] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described below, and can be modified and implemented as appropriate without departing from the spirit of the invention.
[0033] [Composite Member] Figure 1 is a cross-sectional view showing a composite member according to an embodiment of the present invention. The composite member 10 includes a base material 11, an insulating film 12 covering at least a portion of the surface of the base material 11, and a resin layer 13 covering at least a portion of the insulating film 12. The insulating film 12 includes a matrix containing a compound having siloxane bonds and an inorganic material dispersed in this matrix. The resin layer 13 contains a resin different from the material constituting the matrix contained in the insulating film 12.
[0034] If the composite material consists only of an insulating coating 12 formed on the surface of the base material 11, it becomes difficult to ensure the necessary insulation under normal conditions, even if the thickness of the insulating coating is increased.
[0035] In this embodiment, the composite member 10 has a laminated structure of an insulating film 12 and a resin layer 13, so that excellent insulating properties can be obtained under normal conditions. Furthermore, the insulating film 12 includes a matrix containing a compound having siloxane bonds and an inorganic material dispersed in this matrix. Therefore, even when the insulating film 12 is heated to a temperature of, for example, 700°C or higher, SiO ２ Because it remains and does not disappear, excellent heat resistance can be maintained. Furthermore, in this embodiment, the interfacial strength of the resin layer 13 with respect to the insulating film 12, and the relationship between the interfacial strength of the insulating film 12 with respect to the substrate 11 and the interfacial strength of the resin layer 13 with respect to the insulating film 12 are defined. Therefore, when the composite member 10 is exposed to high temperatures, only the resin layer 13 peels off first, and even after the resin layer 13 peels off, the insulating film 12 remains for a certain period of time, so that insulation can be ensured for a long time.
[0036] <Interfacial Strength> The range of interfacial strength defined in this embodiment will be described in detail below. In order for only the resin layer 13 to peel off first when the composite member 10 is exposed to high temperatures, it is necessary to make the interfacial strength of the insulating coating 12 to the substrate 11 greater than the interfacial strength of the resin layer 13 to the insulating coating 12. Therefore, in this embodiment, an interfacial strength test is performed, and the tensile stress TS1 [MPa] at the time of fracture of the insulating coating 12 and the tensile stress TS2 [MPa] at the time of fracture of the resin layer 13 are defined so that cracking or peeling of the insulating coating does not occur even when heated at a temperature of 500°C for 5 minutes, for example.
[0037] The interfacial strength test will be described in more detail with reference to the drawings. Figure 2 is a schematic diagram showing the interfacial strength test method between the resin layer and the insulating coating applied in this embodiment. In this embodiment, the test will be carried out with reference to GB / T 5210-2006, the standard for interfacial strength testing. As shown in Figure 2, a pair of aluminum cylindrical jigs 25a and 25b are clamped by a tensile testing machine (not shown) so that their axes are aligned in a straight line. The test piece 20 is made by blasting the surface of a base material 21 made of the material to be actually used, and then coating one of its main surfaces with the insulating coating 22 and the resin layer 23 that are to be tested.
[0038] In the interfacial strength test, adhesive 24a is applied to the end face of the cylindrical jig 25a, and the cylindrical jig 25a and the resin layer 23 are placed on top of each other and dried at room temperature for 15 hours or more. Similarly, adhesive 24b is applied to the end face of the cylindrical jig 25b, and the cylindrical jig 25b and the base material 21 are placed on top of each other and dried at room temperature for 15 hours or more. Then, the cylindrical jigs 25a and 25b are clamped in a tensile testing machine, and stress is applied in a direction that moves them away from each other, and the tensile stress at which the resin layer 23 breaks is measured.
[0039] The tensile stress specified in the present embodiment is a value measured under the following conditions. ・Reference standard: GB / T 5210-2006 ・Adhesive used (for bonding between the insulating coating and the cylindrical jig): ThreeBond 2082C (manufactured by ThreeBond Co., Ltd.) ・Adhesive used (for bonding between the resin layer and the cylindrical jig): Aron Alpha (manufactured by Toagosei Co., Ltd.) ・Tensile tester: Instron 5567 universal material testing machine (manufactured by Instron) ・Bonding area: 314 mm ２ ・Tensile speed: 1 mm / min ・Base material: Copper C1100 (tough pitch copper standardized in JIS H 3100:2018) ・Base material size: 30 mm × 30 mm × 2 mm (length × width × thickness on the surface where the insulating coating and the resin layer are formed) ・Thickness of the insulating coating: 250 μm
[0040] In the present embodiment, the structure is designed such that only the resin layer peels off first, therefore, according to the above method, the resin layer 23 breaks, and only the interfacial strength (tensile stress TS2) between the resin layer 23 and the insulating coating 22 is measured. Therefore, as shown in FIG. 3, the tensile stress TS1 at break of the insulating coating 22 can be obtained by either peeling only the resin layer 23 from the test piece 20, or preparing a test piece 31 in which only the insulating coating 22 is formed on one main surface of the base material 21, and measuring the interfacial strength between the insulating coating 22 and the base material 21 by the same method as described above. When bonding the insulating coating 22 and the cylindrical jig 25a with an adhesive, the surface of the insulating coating 22 may be sanded with a file to prevent poor adhesion.
[0041] When the relationship between the tensile stress TS1 at break of the insulating coating and the tensile stress TS2 at break of the resin layer deviates from the following formula (1), that is, when TS2 is 1 / 3 or more of TS1, the insulating coating is prone to cracking when exposed to high temperature, and the insulating coating may peel off from the base material together with the resin layer. Therefore, the tensile stress TS2 at break of the resin layer, measured with reference to GB / T 5210-2006, shall be smaller than (1 / 3)×TS1, preferably not more than (1 / 5)×TS1, more preferably not more than (1 / 7)×TS1, and even more preferably not more than (1 / 10)×TS1.
[0042] Furthermore, when the tensile stress TS2 at break of the resin layer is 0 [MPa], the resin layer will not be bonded to the insulating coating, which makes handling difficult. Therefore, the tensile stress TS2 at break of the resin layer, measured with reference to GB / T 5210-2006, is more than 0 [MPa], preferably 0.05 [MPa] or more, and more preferably 0.10 [MPa] or more.
[0043] On the other hand, when the tensile stress TS2 at break of the resin layer is 0.50 [MPa] or more, the adhesive force between the resin layer and the insulating coating becomes too high, so that when exposed to high temperature, the insulating coating is prone to peel off from the base material together with the resin layer. Therefore, the tensile stress TS2 at break of the resin layer, measured with reference to GB / T 5210-2006, is less than 0.50 [MPa], preferably 0.45 [MPa] or less, and more preferably 0.40 [MPa] or less. Further, the tensile stress TS2 is preferably 0.30 [MPa] or less, more preferably 0.20 [MPa] or less, and even more preferably 0.15 [MPa] or less.
[0044] Furthermore, when the tensile stress TS1 at break of the insulating coating is 1.0 [MPa] or more, cracking of the insulating coating and peeling from the base material can be suppressed under normal conditions and when exposed to high temperature. Therefore, the tensile stress TS1 at break of the insulating coating, measured with reference to GB / T 5210-2006, is preferably 1.0 [MPa] or more, more preferably 1.20 [MPa] or more, and even more preferably 1.50 [MPa] or more.
[0045] The upper limit of the tensile stress TS1 at break of the insulating coating is not particularly limited, but when it is 10.0 [MPa] or less, the material for the insulating coating can be easily selected. Therefore, the tensile stress TS1 at break of the insulating coating, measured with reference to GB / T 5210-2006, is preferably 10.0 [MPa] or less, more preferably 9.0 [MPa] or less, and even more preferably 8.0 [MPa] or less.
[0046] <Weight loss rate of the resin layer at 500°C: higher than 65% by weight> The weight loss rate of the resin layer under predetermined conditions, as measured by thermogravimetric analysis (TG), affects the remaining state of the resin layer and the peeling of the insulating coating at high temperatures. In thermogravimetric analysis when heated from room temperature at a heating rate of 10°C / min in an atmospheric environment, if the weight loss rate of the resin layer at 500°C is higher than 65% by weight, then in abnormally high-temperature environments, the resin layer will not remain in a way that affects the insulating coating, and the insulating coating will remain even if the resin layer peels off. As a result, the insulating state can be maintained for a certain period of time. Therefore, in thermogravimetric analysis under the above conditions, the weight loss rate of the resin layer at 500°C is preferably higher than 65% by weight, more preferably 70% by weight or more, and even more preferably 80% by weight or more.
[0047] <Weight loss rate of insulating coating at 500°C: Lower than 15% by weight> Similar to the resin layer, the weight loss rate of the insulating coating under predetermined conditions, as measured by thermogravimetric analysis, affects the remaining state of the insulating coating and its delamination at high temperatures. In thermogravimetric analysis when heated from room temperature at a heating rate of 10°C / min in an atmospheric environment, if the weight loss rate of the insulating coating at 500°C is lower than 15% by weight, the insulating coating will remain for a certain period after the resin layer has delaminated in an abnormally high-temperature environment, thus maintaining the insulating state. Therefore, in thermogravimetric analysis under the above conditions, the weight loss rate of the insulating coating at 500°C is preferably lower than 15% by weight, more preferably 10% by weight or less, and even more preferably 8% by weight or less.
[0048] <Thermal Decomposition Temperature of the Resin Layer> The thermal decomposition temperature of the resin layer under predetermined conditions, measured by thermogravimetric differential thermal analysis (TG-DTA), affects the remaining state of the resin layer at high temperatures and the peeling of the insulating film, similar to the weight loss rate mentioned above. In thermogravimetric differential thermal analysis when heated from room temperature at a heating rate of 10°C / min in an atmospheric environment, if the thermal decomposition temperature of the resin layer is lower than 560°C, the resin layer will not remain in a way that affects the insulating film in abnormally high-temperature environments, and even if the resin layer peels off, the insulating film will remain, thus maintaining an insulating state for a certain period. Therefore, in thermogravimetric differential thermal analysis under the above conditions, the thermal decomposition temperature of the resin layer is preferably lower than 560°C, more preferably 550°C or lower, and even more preferably 540°C or lower.
[0049] <Thickness of insulating coating: 150 μm or more and 800 μm or less> The thickness of the insulating coating affects the strength and peelability of the insulating coating. When the thickness of the insulating coating is 150 μm or more, sufficient strength as an insulating coating can be obtained, and the occurrence of peeling can be suppressed. Therefore, the thickness of the insulating coating is preferably 150 μm or more, more preferably 200 μm or more, and even more preferably 250 μm or more. Furthermore, when the thickness of the insulating coating is 800 μm or less, the occurrence of peeling due to increased internal stress can be suppressed. Therefore, the thickness of the insulating coating is preferably 800 μm or less, more preferably 700 μm or less, and even more preferably 600 μm or more.
[0050] <Resin layer thickness: 100 μm or more and 600 μm or less> The thickness of the resin layer affects the strength and peelability of the resin layer. When the thickness of the resin layer is 100 μm or more, sufficient strength as a resin layer can be obtained, and the spread of fire during thermal runaway of the battery can be suppressed. Therefore, the thickness of the resin layer is preferably 100 μm or more, more preferably 120 μm or more, and even more preferably 150 μm or more. Furthermore, when the thickness of the resin layer is 600 μm or less, the occurrence of peeling due to increased internal stress can be suppressed. Therefore, the thickness of the resin layer is preferably 600 μm or less, more preferably 550 μm or less, and even more preferably 500 μm or less.
[0051] The materials constituting the insulating coating and the resin layer in the composite member according to this embodiment will be described in more detail below.
[0052] <Insulating Coating> (Compounds containing siloxane bonds) A suitable example of a compound containing siloxane bonds included in the matrix of the insulating coating is silicone. Silicone is heated during the curing process of the insulating coating material, which causes the functional groups to disappear and SiO bonds to be formed. Also, if a fire occurs near the composite member and the insulating coating is heated to a temperature of, for example, 700°C or higher, thermal decomposition will occur and SiO will be formed. ２ This is generated. And this SiO ２ Because it does not burn even when exposed to flames, the insulating coating containing silicone can obtain excellent heat resistance. In other words, even when exposed to high temperatures, the composite member according to this embodiment can maintain excellent insulation and heat resistance as the insulating coating adheres to the substrate without peeling off. The compound having siloxane bonds (Si-O-Si bonds) in the matrix material of the insulating coating is silicone and silica sol (silica: SiO ２is preferably at least one selected from), more preferably silicone. In addition, it is also a preferred embodiment that the matrix contains both silicone and silica sol. Furthermore, silicones include silicone resins and silicone rubbers, either of which may be used; however, silicone resins are preferred for the formed SiO ２ from the viewpoint of increasing the density thereof.
[0053] (Inorganic Material) Since inorganic materials have a high melting point and excellent heat resistance, the inclusion of an inorganic material in the insulating coating can further improve the heat resistance of the insulating coating. Additionally, in the insulating coating, the inorganic material can also function as a framework, so the strength of the insulating coating can be improved.
[0054] As the inorganic material, it is preferable to include a silicate compound. As described above, silicone, which is an example of a compound having a siloxane bond, is thermally decomposed into SiO ２ while the silicate compound has the same components as the SiO ２ formed by silicone, so the binding force between the silicone-containing matrix and the inorganic material can be improved. It is preferable that the silicate compound includes at least one selected from the group consisting of glass-based materials, mica, kaolin, talc, clay, pyrophyllite, montmorillonite, bentonite, wollastonite, xonotlite, zeolite, diatomaceous earth, and halloysite.
[0055] The main component of silica sol (silica), which is a suitable example of a compound having a siloxane bond, is SiO ２ and the silicate compound as the inorganic material has the same components as silica sol (SiO ２ ). Therefore, when silica sol is contained in the matrix of the insulating coating, the binding force between the matrix and the inorganic material can also be improved.
[0056] Furthermore, it is preferable to include at least one inorganic material selected from silica, alumina, calcium carbonate, mullite, and zirconia. Since these materials have high melting points and high insulating properties, including them in the insulating coating can further improve the heat resistance and insulating properties of the insulating coating. In the case of a busbar, which is an example of a composite member of the present invention, the expected thermal exposure temperature to the busbar is above the melting point of the metal material used for the busbar body. In this embodiment, if the inorganic material includes silica, alumina, calcium carbonate, mullite, zirconia, etc., these materials have melting points above the above thermal exposure temperature, so it is possible to suppress the busbar body from being exposed to high heat. Therefore, these materials are suitably used as materials for the insulating coating in a busbar.
[0057] Furthermore, it is preferable that the inorganic material includes at least one shape selected from flake, fibrous, and particulate forms. When the inorganic material has the above shapes, the adhesion between the inorganic material and the matrix is increased when the inorganic material is dispersed in the matrix, thereby improving the strength of the insulating film.
[0058] Furthermore, when the inorganic material includes a glass-based material, it is preferable to use at least one of flake-shaped glass-based materials, glass particles, and glass fibers as the glass-based material. Among these, the flake-shaped glass-based material is oriented in a planar manner within the insulating film and exhibits excellent insulating properties and heat resistance. Similarly, the mica mentioned above also exhibits excellent insulating properties and heat resistance for the same reasons as the flake-shaped glass-based material. Therefore, it is particularly preferable that the inorganic material includes at least one of the flake-shaped glass-based material and mica.
[0059] The inorganic material content in the insulating coating is preferably 3 to 70 volume%, more preferably 10 to 50 volume%, and even more preferably 20 to 40 volume%. If the inorganic material content is less than 3 volume%, sufficient insulation and heat resistance may not be obtained. On the other hand, if it exceeds 70 volume%, the viscosity of the coating material when forming the insulating coating becomes too high, resulting in poor film formation.
[0060] The inorganic material content in an insulating film can be measured, for example, by the following method. First, a cross-section of the insulating film parallel to its thickness is photographed with an electron microscope. An arbitrary region is selected from the resulting photograph, and the parts within this region that can be identified as inorganic material are colored. Then, the inorganic material content (volume %) can be calculated by dividing the total area of the colored parts (inorganic material) by the area of the selected region. The larger the size of the region to be measured, the smaller the error. For example, a rectangular region can be selected where the length of the side in the film thickness direction is 90% of the film thickness of the insulating film, and the length of the side perpendicular to the film thickness direction is 300 μm. It is preferable to obtain the inorganic material content in the insulating film by taking regions of the above size from three different locations in the insulating film and calculating the average of the obtained content, and it is even more preferable to obtain the content from five different locations and calculating the average of the obtained content.
[0061] In addition to the matrix and inorganic materials described above, the insulating coating may also contain other materials such as flame retardants, dispersants, and pigments, as long as they do not affect its insulating properties or heat resistance. Furthermore, the insulating coating is formed by applying the coating material (coating liquid) to the surface of the substrate, and it is preferable to include a thixotropic agent in order to improve the coating performance of the coating liquid containing the matrix material and inorganic materials.
[0062] <Resin Layer> The resin layer contains a resin different from the material that constitutes the matrix included in the insulating film. Preferably, the resin layer contains at least one selected from, for example, nylon resin, SBR (styrene-butadiene rubber), silicone rubber, PVC (polyvinyl chloride), and epoxy resin. If the resin layer contains the above resins, the insulating properties under normal conditions can be further improved. Note that the properties of some resin layers using these resins also change depending on the formation method. For example, in the case of epoxy resin, resin layers formed by powder coating tend to have a high tensile stress TS2 at fracture, while resin layers formed by UV curing tend to have a low tensile stress TS2 at fracture. Therefore, it is preferable to select the material and manufacturing method of the resin layer so as to satisfy both formulas (1) and (2) above.
[0063] <Base Material> In this embodiment, the base material is not particularly limited, and the main body of various products to which the composite member according to this embodiment is applied can be used as the base material. For example, when a busbar, which will be described later, is applied as the composite member, a conductive busbar body can be used as the base material. Although the busbar body is conductive and the base material itself is electrically conductive, in this embodiment, the base material to be covered with an insulating coating is not limited to conductive materials. For example, a base material made of a non-electrical material can also be used.
[0064] <Method for Manufacturing Composite Members> In this embodiment, the method for manufacturing composite members is not particularly limited. An insulating film 12 is formed by applying the material constituting the insulating film to at least a portion of the surface of the base material 11, drying and curing it. Then, a resin layer 13 is formed by applying the material constituting the resin layer to at least a portion of the surface of the insulating film 12, drying and curing it. This allows for the manufacture of composite members 10. The insulating film 12 may be formed in areas of the surface of the base material 11 where insulation is required. The resin layer 13 may be formed on at least a portion of the surface of the insulating film 12, but it is preferable that it be formed on the entire surface of the insulating film 12.
[0065] Methods for applying the insulating coating material and the resin layer material include "dip coating," in which the substrate or the substrate on which the insulating coating is formed is immersed in a coating solution, and coating by brush or spray.
[0066] [Specific Application Examples of Composite Components] The products to which the composite component 10 is applied are not particularly limited, but for example, it can be applied to busbars used to connect multiple battery cells or battery modules in energy storage devices. The following describes the configuration when the composite component 10 is applied to a busbar.
[0067] Figure 4 is a perspective view showing a busbar to which the composite member according to this embodiment is applied. Note that Figure 2 shows the state immediately before the busbar (composite member) 100 is attached to the battery cell 130. The busbar body (base material) 110 is, for example, a metal plate member that is Z-shaped overall. The electrodes 135 of the battery cell 130 are inserted into the connection hole 115a at one end and fixed by covering it with a terminal cap 136. The connection hole 115b at the other end of the busbar body 110 is connected to an adjacent battery cell (not shown) or external equipment (not shown). The area of the busbar body 110 excluding the connection holes 115a and 115b is covered with an insulating coating and a resin layer 13 (not shown in Figure 4). That is, a cross-section cut along the thickness direction of the busbar 100, for example, by the dashed line L, has a configuration similar to the composite member 10 shown in Figure 1. The busbar 100 is constructed in this way.
[0068] Although not shown in the diagram, the busbar body 110 may be I-shaped overall or have an irregular shape with a curved section, and can be made into various shapes depending on the installation location of the battery cell 130.
[0069] If the busbar body 110 has a shape such as the Z-shaped bend 110a or curved portion (not shown) as shown in the figure, the following problems arise. For example, in the busbar shown in Patent Document 1, where ceramic tape is wrapped around the body, the wrapping process is time-consuming in order to prevent uneven wrapping or gaps from occurring in the bend 110a or curved portion. In addition, it is conceivable that gaps may occur between the ceramic tapes due to vibration or that the adhesive between the ceramic tape and the body may peel off.
[0070] In contrast, in the busbar 100 configured as described above, insulation is not provided by wrapping tape around the busbar body 110; rather, an insulating film is formed on the surface of the busbar body 110, and a resin layer is formed on at least a part of that surface. Therefore, during the manufacturing of the busbar 100, wrapping work is unnecessary, there are no problems with uneven wrapping, gaps, or peeling, and it can easily accommodate complex shapes.
[0071] As described above, methods for applying the insulating coating material to the surface of the busbar body 110 include "dip coating," in which the busbar body 110 is immersed in a coating solution, and painting with a brush or spray. When using dip coating, the insulating coating is not formed in the connection holes 115a and 115b, so these areas are masked before immersion in the coating solution. Furthermore, as a method for applying the resin layer 13 to the surface of the insulating coating, the busbar body may be masked after the insulating coating has been formed, and then the resin layer material may be immersed or painted.
[0072] In addition to the busbar described above, the composite member according to this embodiment can be applied to connectors, protective components for battery modules, cases for electronic components, battery cells, battery modules, battery packs, or motor coils.
[0073] [Energy Storage Device] Figure 5 is a schematic diagram showing an energy storage device according to an embodiment of the present invention. The energy storage device 200 consists of a plurality of battery cells 130, 130 connected by the busbar (composite member) 100 and housed in a case 210. Alternatively, the energy storage device 200 may consist of a plurality of battery modules (not shown) connected by the busbar 100 and housed in a case 210.
[0074] Since the busbar body 110 of the busbar 100 is covered with the insulating coating and resin layer 13 of this embodiment described above, even if a battery cell 130 experiences thermal runaway, the resin layer 13 will peel off first, and the insulating properties can be maintained for a certain period of time until the insulating coating peels off. Therefore, excellent safety can be obtained.
[0075] The following describes examples and comparative examples of composite members according to this embodiment.
[0076] [First Example] <Preparation of Test Specimens> An insulating coating and a resin layer were laminated in this order on one main surface of a copper substrate to prepare a test specimen for measuring the interfacial strength between the resin layer and the insulating coating. For the insulating coating of this test specimen, an insulating coating P05 containing silicone resin and mica was formed. For the resin layer, epoxy resin applied by powder coating or styrene-butadiene rubber was used. In addition, a test specimen was prepared by forming only an insulating coating on one main surface of a copper substrate to measure the interfacial strength between the insulating coating and the substrate. For the insulating coating of this test specimen, an insulating coating W02 containing silicone emulsion, silica sol and mica, or an insulating coating P05 containing silicone resin and mica was formed. The materials of the substrate, insulating coating and resin layer are shown in Table 1 below.
[0077]
[0078] <Interfacial Strength Test> An interfacial strength test was performed on each test specimen. As described in Figure 2, adhesive 24a was applied to the end face of the upper cylindrical jig 25a to bond the cylindrical jig 25a to the resin layer 23. Similarly, adhesive 24b was applied to the end face of the lower cylindrical jig 25b to bond the cylindrical jig 25b to the base material 21. Adhesives 24a and 24b were each kept at room temperature for 15 hours or more to dry and harden. After that, the cylindrical jigs 25a and 25b were clamped in a tensile testing machine, and stress was applied in the direction that moved the cylindrical jigs 25a and 25b away from each other at a uniform tensile speed, and the tensile stress TS2 at the time of fracture of the resin layer 23 was measured.
[0079] Furthermore, as shown in Figure 3, the upper cylindrical jig 25a and the insulating coating 22 were bonded together with adhesive 24a, and the lower cylindrical jig 25b and the base material 21 were bonded together with adhesive 24b. Subsequently, the tensile stress TS1 at the time of fracture of the insulating coating 22 was measured using the same method as described above. The test conditions are shown in Table 2 below.
[0080]
[0081] <Evaluation Results> The tensile stresses TS1 and TS2 at the time of fracture of the insulating coating 22 and the resin layer 23 were substituted into the following equations (1) and (2) to confirm whether TS1 and TS2 were values that satisfied equations (1) and (2). In addition, a cracking and delamination test was performed on each test piece by heating it at 500°C for 5 minutes, and the cracking or delamination of the insulating coating 22 was observed. The values of the tensile stresses TS1 and TS2, and the evaluation results are shown in Tables 3 and 4 below. In the columns for equations (1) and (2) in Tables 3 and 4 below, ○ indicates that the equations are satisfied, and × indicates that they are not satisfied. In the column for the cracking and delamination evaluation, ○ indicates that neither cracking nor delamination of the insulating coating 22 occurred after heating, and × indicates that cracking or delamination occurred.
[0082] Formula (1): TS2<(1 / 3)×TS1 Formula (2): 0[MPa]<TS2<0.50[MPa]
[0083]
[0084]
[0085] As shown in Tables 3 and 4 above, Invention Examples No. 1 to 15 used SBR as the resin layer, and the tensile strengths TS1 and TS2 at the time of fracture of the insulating film and resin layer both satisfied values of formulas (1) and (2). Therefore, even when heated at 500°C for 5 minutes, no cracking or peeling of the insulating film occurred. On the other hand, Comparative Examples No. 1 to 15 used epoxy resin formed by powder coating as the resin layer, and the tensile strengths TS1 and TS2 at the time of fracture of the insulating film and resin layer did not satisfy either or both of formulas (1) and (2). Therefore, cracking and peeling of the insulating film occurred. As mentioned above, Comparative Examples No. 1 to 15 used a resin layer formed by powder coating as the resin layer, but it is conceivable that the tensile strength TS2 at the time of fracture would be lower if a resin layer made of epoxy resin were formed by UV curing. As a result, the values obtained satisfy equations (1) and (2) may suppress cracking and peeling in the cracking and peeling test of the insulating coating.
[0086] [Second Embodiment] <Preparation of Test Specimen and Interfacial Strength Test> A test specimen was prepared to measure the interfacial strength under different conditions than those of the first embodiment. Specifically, as shown in Figure 3, an insulating coating 22 was formed on one main surface of a copper substrate 21. In addition, instead of adhesive 24a, the resin layer material was placed on the end face of a cylindrical jig 25a, and the insulating coating 22 and the resin layer were held together so that they overlapped. By drying the resin layer, the cylindrical jig 25a and the resin layer were bonded together, and the resin layer and the insulating coating 22 were bonded together. As with the first embodiment, tough pitch copper (C1100) was used as the substrate. As for the resin layer, PVC or SBR as shown in Table 1 was used.
[0087] Subsequently, the cylindrical fixtures 25a and 25b were clamped in a tensile testing machine, and stress was applied at a uniform tensile speed in a direction that moved the cylindrical fixtures 25a and 25b away from each other. The tensile stress TS2 at the time of fracture of the resin layer corresponding to the adhesive 24a in Figure 3 was measured. The test conditions were the same as those shown in Table 2 above, except that no adhesive was used.
[0088] <Evaluation Results> The tensile stresses TS1 and TS2 at the time of fracture of the insulating coating and resin layer were substituted into equations (1) and (2) above to confirm whether TS1 and TS2 were values that satisfied equations (1) and (2). In addition, a cracking and delamination test was performed on test pieces in which the insulating coating and resin layer were formed on the surface of the substrate using the same material as each test piece, by heating at 500°C for 5 minutes, and the cracking or delamination of the insulating coating 22 was observed. For the insulating coating, P05-4, which showed the highest tensile stress, and W02-1, which showed the lowest tensile stress, were used to confirm whether they were values that satisfied equations (1) and (2). The evaluation criteria were the same as in the first embodiment above. The values of the tensile stresses TS1 and TS2 and the evaluation results are shown in Table 5 below.
[0089]
[0090] As shown in Table 5 above, in both cases where the resin layer was made of SBR and PVC, the tensile stresses TS1 and TS2 at the time of fracture of the insulating coating and resin layer satisfied equations (1) and (2). Therefore, no cracking or delamination of the insulating coating occurred.
[0091] [Third Example] Thermogravimetric differential thermal analysis was performed on the two types of insulating coatings and three types of resin layers shown in Table 1 above. Figure 6 is a graph showing the results of thermogravimetric differential thermal analysis (TG-DTA) when polyvinyl chloride (PVC) was formed as the resin layer. Figure 7 is a graph showing the results of TG-DTA analysis when styrene-butadiene rubber (SBR) was formed as the resin layer. Furthermore, Figure 8 is a graph showing the results of TG-DTA analysis when epoxy resin was formed as the resin layer by powder coating. Figure 9 is a graph showing the results of TG-DTA analysis when insulating coating W02 shown in Table 1 was formed. Figure 10 is a graph showing the TG-DTA analysis results when the insulating film P05 shown in Table 1 is formed.
[0092] The measurements were performed in an atmospheric environment, and the heating rate was set to 10°C / min, starting from room temperature. The TG-DTA8122 was used as the analytical instrument.
[0093] As shown in Figure 6, when PVC was selected as the resin layer, the weight loss rate at 500°C was approximately 87% by weight, and the thermal decomposition temperature was approximately 540°C (a value lower than 540°C). Also, as shown in Figure 7, when SBR was selected as the resin layer, the weight loss rate at 500°C was approximately 89% by weight, and the thermal decomposition temperature was approximately 400°C. In contrast, as shown in Figure 9, when insulating film W02 was selected, the weight loss rate at 500°C was approximately 2.4% by weight, and as shown in Figure 10, when insulating film P05 was selected, the weight loss rate at 500°C was approximately 9.5% by weight. From this, it was shown that in abnormal high-temperature environments, the resin layer peels off first, leaving the insulating film. Therefore, it is considered that a composite member in which a resin layer made of PVC or SBR is formed on the surface of insulating film W02 or insulating film P05 can maintain an insulating state for a certain period of time even under abnormal conditions.
[0094] As shown in Figure 8, when epoxy resin applied by powder coating was selected as the resin layer, the weight loss rate of the epoxy resin at 500°C was approximately 61% by weight, and the thermal decomposition temperature was higher than 560°C. Therefore, it is considered difficult to maintain insulation properties in abnormally high-temperature environments, as the resin layer would not remain intact and would peel off together with the insulating coating.
[0095] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.
[0096] This application is based on a Japanese patent application (Patent Application No. 2025-054058) filed on March 27, 2025, the contents of which are incorporated herein by reference.
[0097] 10 Composite component 11, 21 Base material 12, 22 Insulating coating 13, 23 Resin layer 20, 31 Test piece 24a, 24b Adhesive 25a, 25b Cylindrical jig 100 Busbar 110 Busbar body 110a Bent section 115a, 115b Connection hole 130 Battery cell 135 Electrode 136 Terminal cap 200 Energy storage device 210 Case
Claims
1. A composite member comprising a base material, an insulating film covering at least a portion of the surface of the base material, and a resin layer covering at least a portion of the surface of the insulating film, wherein the insulating film comprises a matrix containing a compound having siloxane bonds and an inorganic material dispersed in the matrix, and the resin layer comprises a resin different from the material constituting the matrix, and when an interfacial strength test is performed between the insulating film and the base material with reference to GB / T 5210-2006 to measure the tensile stress TS1 [MPa] at the time of fracture of the insulating film, and when an interfacial strength test is performed between the resin layer and the insulating film to measure the tensile stress TS2 [MPa] at the time of fracture of the resin layer, both of the following formulas (1) and (2) are satisfied: Formula (1): TS2 < (1 / 3) × TS1 Formula (2): 0 [MPa] < TS2 < 0.50 [MPa] 2. The composite member according to claim 1, characterized in that, in thermogravimetric analysis, the resin layer exhibits a weight loss rate at 500°C that is higher than 65% by weight when heated from room temperature at a heating rate of 10°C / min in an atmospheric environment.
3. The composite member according to claim 1, characterized in that, in thermogravimetric analysis, the insulating coating exhibits a weight loss rate of less than 15% by weight at 500°C when heated from room temperature at a heating rate of 10°C / min in an atmospheric environment.
4. The composite member according to claim 1, characterized in that the resin layer has a thermal decomposition temperature of less than 560°C when heated in an atmospheric environment, as determined by thermogravimetric differential thermal analysis.
5. The composite member according to claim 1, characterized in that the thickness of the insulating coating is 150 μm or more and 800 μm or less.
6. The composite member according to claim 1, characterized in that the thickness of the resin layer is 100 μm or more and 600 μm or less.
7. The composite member according to claim 1, characterized in that the compound having a siloxane bond is at least one selected from silicone and silica sol.
8. The composite member according to claim 1, characterized in that the inorganic material includes at least one selected from silica, alumina, calcium carbonate, mullite, and zirconia.
9. The composite member according to claim 1, characterized in that the inorganic material includes at least one selected from glass-based materials, mica, kaolin, talc, clay, pyrophyllite, montmorillonite, bentonite, wollastonite, xonotlite, zeolite, diatomaceous earth, and halloysite.
10. The composite member according to claim 1, characterized in that the inorganic material includes at least one selected from flake, fibrous, and particulate forms.
11. The composite member according to claim 1, characterized in that the inorganic material includes at least one of a flake-shaped glass-based material and mica.
12. The composite member according to claim 1, characterized in that the resin layer comprises at least one selected from nylon resin, styrene-butadiene rubber, silicone rubber, polyvinyl chloride, and epoxy resin.
13. The composite member according to any one of claims 1 to 12, characterized in that it is applied to a busbar connecting a plurality of battery cells or battery modules.
14. The composite member according to any one of claims 1 to 12, characterized in that it is applied to a connector, a protective component for a battery module, a case for an electronic component, a battery cell, a battery module, a battery pack, or a motor coil.
15. An energy storage device characterized by connecting a plurality of battery cells or battery modules with a composite member as described in any one of claims 1 to 12.