Composite member

Abstract

Provided is a composite member which exhibits excellent heat resistance in addition to excellent insulating properties, which does not require a winding operation that is necessary in the case of a ceramic tape, which does not have problems such as uneven winding, gap generation, and separation, and which can be easily suited to a conductive base material that has a complicated shape. This composite member (1) has a base material (2), and an insulating coating film (3) that covers at least a part of the surface of the base material (2) and has a film thickness of 150 μm or more. The insulating coating film (3) has a matrix (10) that contains a compound having a siloxane bond, and an inorganic material (20) that is dispersed in the matrix (10). If a cross-section of the insulating coating film (3), the cross-section being parallel to the film thickness direction, is observed, the ratio (P1 / P2) of the porosity P1 in a region R1 in the range from the interface with the base material (2) to 100 μm to the porosity P2 in a region R2 in the range from the surface of the insulating coating film (3) to 100 μm is 0.3 to 3.0 inclusive. The regions R1 and R2 are each 75 μm in the film thickness direction and 300 μm in a direction that is orthogonal to the film thickness.

Description

Composite materials

[0001] The present invention relates to a composite member in which a substrate is coated with an insulating coating.

[0002] Conductive materials, which are metal pieces with insulating coatings formed on their surfaces, are used to electrically connect components. For example, various electronic devices, electric vehicles or hybrid vehicles driven by electric motors, and storage batteries are equipped with power storage devices in which multiple battery cells are connected in series or parallel by conductive bus bars. Furthermore, lithium-ion secondary batteries, which have higher capacity and higher output than lead-acid batteries or nickel-metal hydride batteries, are primarily used as battery cells.

[0003] When a battery cell is charged or discharged, an overcurrent may flow through the bus bar, causing the bus bar to heat up and possibly even burst into flames. Therefore, the bus bar must be heat-resistant as well as insulating. For example, Patent Document 1 (JP-A-2003-125566) describes a bus bar in which a ceramic tape, such as mica tape, is wrapped around a copper bus bar body as a fire-resistant layer.

[0004] Chinese Utility Model No. 216902355

[0005] However, in Patent Document 1, the ceramic tape must be wrapped around the busbar body. Due to spatial limitations in the installation location of the battery cells, the busbar may have a complex shape, making it difficult to wrap the ceramic tape thoroughly around every corner of the busbar body. If the ceramic tape has uneven wrapping or gaps, sufficient insulation and heat resistance cannot be achieved. Furthermore, the adhesive surface of the ceramic tape may peel off. Furthermore, nylon tape is wrapped around the outside of the mica tape as an insulating layer, but nylon tape is sensitive to heat and has heat resistance issues.

[0006] Therefore, an object of the present invention is to provide a composite member that has excellent insulation and heat resistance, does not require winding work like ceramic tape, is free from problems such as uneven winding, gaps, and peeling, can be easily adapted to complex shapes, and can maintain excellent insulation and heat resistance by having an insulating coating that adheres to the substrate without peeling even when heated at high temperatures.

[0007] The above object of the present invention is achieved by the following configuration [1] relating to a composite member.

[0008] [1] A composite member having a substrate and an insulating coating covering at least a portion of a surface of the substrate, wherein the insulating coating has a thickness of 150 μm or more, and the insulating coating has a matrix containing a compound having a siloxane bond and an inorganic material dispersed in the matrix, wherein, when a cross section of the insulating coating parallel to a thickness direction is observed, the ratio (P1 / P2) of a porosity P1 in a rectangular region R1 extending from an interface between the insulating coating and the substrate to 100 μm in the thickness direction, the rectangular region R1 having sides of 75 μm in the thickness direction and sides of 300 μm perpendicular to the thickness direction, to a porosity P2 in a rectangular region R2 extending from a surface of the insulating coating to 100 μm in the thickness direction, the rectangular region R2 having sides of 75 μm in the thickness direction and sides of 300 μm perpendicular to the thickness direction, is 0.3 or more and 3.0 or less.

[0009] Furthermore, preferred embodiments of the present invention relating to the composite member relate to the following [2] to

[14] .

[0010] [2] The composite material according to [1], characterized in that, when a cross section parallel to a thickness direction of the insulating coating is observed, a porosity P3 in a rectangular region R3 having a length of a side parallel to the thickness direction that is 90% of the thickness of the insulating coating and a side perpendicular to the thickness direction that is 300 μm is 10% or less.

[0011] [3] The composite material according to [1] or [2], wherein the porosity P1 and the porosity P2 are both 10% or less.

[0012] [4] The composite material according to any one of [1] to [3], characterized in that at least a part of the surface of the insulating coating has a surface layer made of the matrix material.

[0013] [5] The composite material according to [4], wherein the thickness of the surface layer is 10 μm or more and 100 μm or less.

[0014] [6] The composite material according to any one of [1] to [5], characterized in that at least a part of the surface of the insulating coating has a resin layer containing a resin different from the material of the matrix.

[0015] [7] The composite material according to [6], characterized in that the resin layer has a thickness of 100 μm or more and 600 μm or less.

[0016] [8] The composite material according to any one of [1] to [7], wherein the compound having a siloxane bond is at least one of silicone and silica sol.

[0017] [9] The composite member according to any one of [1] to [8], characterized in that the inorganic material contains at least one selected from silica, alumina, mullite, and zirconia.

[0018]

[10] The composite member according to any one of [1] to [8], characterized in that the inorganic material contains at least one selected from glass-based materials, mica, kaolin, talc, clay, pyrophyllite, montmorillonite, bentonite, wollastonite, xonotlite, zeolite, diatomaceous earth, and halloysite.

[0019]

[11] The composite member according to any one of [1] to

[10] , characterized in that the inorganic material contains at least one selected from the group consisting of flake-shaped, fibrous, and particulate inorganic materials.

[0020]

[12] The composite member according to any one of [1] to [8], wherein the inorganic material contains at least one of a glass flake material and mica.

[0021]

[13] The composite member according to any one of [1] to

[12] , which is applied to a bus bar that connects a plurality of battery cells or battery modules.

[0022]

[14] The composite member according to any one of [1] to

[12] , which is applied to a connector, a protective part for a battery module, a case for an electronic component, a battery cell, a battery module, a battery pack, or a motor coil.

[0023] The composite member of the present invention has an insulating coating that covers at least a portion of the substrate and contains a compound having a siloxane bond and an inorganic material, thereby achieving excellent heat resistance and insulating properties. Furthermore, the insulating coating has a predetermined thickness or more, and the ratio of pore densities in the thickness direction between the region close to the substrate and the region close to the outer surface is set within a predetermined range, thereby achieving excellent strength and further improving heat resistance and insulating properties.

[0024] FIG. 1 is a photograph showing a cross section of a composite member according to the present embodiment. FIG. 2 is a perspective view showing a bus bar to which the composite member according to the present embodiment is applied. FIG. 3A is a diagram showing the steps of a method for manufacturing a composite member according to the present embodiment, and is a schematic diagram showing the state after the first first coating material curing step. FIG. 3B is a diagram showing the steps of a method for manufacturing a composite member according to the present embodiment, and is a schematic diagram showing the state after the first immersion step. FIG. 3C is a diagram showing the steps of a method for manufacturing a composite member according to the present embodiment, and is a schematic diagram showing the state after the second first coating material curing step. FIG. 3D is a diagram showing the steps of a method for manufacturing a composite member according to the present embodiment, and is a schematic diagram showing the state after the resin layer forming step.

[0025] The present inventors conducted extensive research to develop a composite member that can solve the above-mentioned problems without using an insulating tape such as ceramic tape. As a result, they discovered that by applying an insulating coating material to the surface of a substrate and then forming an insulating coating that covers the surface of the substrate, it is possible to easily adapt the composite member to complex shapes. However, simply applying an insulating coating material and curing the material to form an insulating coating results in the generation of numerous pores within the insulating coating, which reduces the strength of the insulating coating. Furthermore, if the insulating coating is formed thick in order to ensure sufficient strength and insulation, uneven pore density will occur in the thickness direction of the coating, which may further reduce the strength.

[0026] The inventors have found that forming an insulating coating having a thickness equal to or greater than a predetermined value and having a pore density ratio in the thickness direction between the region close to the substrate and the region close to the outer surface within a predetermined range is effective in solving the above problems. That is, a composite member having the insulating coating exhibits high adhesion between the insulating coating and the substrate, and also exhibits excellent insulation and heat resistance.

[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments described below, and can be implemented with any modifications within the scope of the gist of the present invention.

[0028] [Composite Member] Fig. 1 is a photograph showing a cross section of a composite member according to this embodiment. The composite member 1 has a substrate 2 and an insulating coating 3 that covers at least a portion of the surface of the substrate 2. As shown in Fig. 1, the composite member 1 may also have a surface layer 4 made of a matrix 10 material, which will be described later, on at least a portion of the surface of the insulating coating 3. The insulating coating 3, surface layer 4, and substrate 2 of the composite member 1 according to this embodiment will be described in detail below.

[0029] <Insulating Coating> The insulating coating 3 has a matrix 10 containing a compound having a siloxane bond and an inorganic material 20 dispersed in this matrix 10. Both the compound having a siloxane bond and the inorganic material 20 are materials with excellent heat resistance and insulating properties, and therefore, when the compound having a siloxane bond and the inorganic material 20 are included as components of the insulating coating 3, an insulating coating with excellent heat resistance and insulating properties can be obtained. Furthermore, a plurality of pores 30 are formed inside the insulating coating 3.

[0030] Examples of compounds having a siloxane bond (Si—O—Si bond) include silicone and silica sol (silica: SiO ２ From the viewpoint of excellent heat resistance and insulating properties, the compound having a siloxane bond contained in the matrix 10 is preferably at least one of silicone and silica sol, and more preferably silicone. It is also a preferred embodiment that the matrix 10 contains both silicone and silica sol.

[0031] In this embodiment, the thickness of the insulating coating 3 and the porosity when a cross section of the insulating coating 3 is observed in a direction parallel to the thickness of the insulating coating 3 are defined as follows.

[0032] (Thickness of the Insulating Coating) If the thickness of the insulating coating 3 is less than 150 μm, the strength of the insulating coating 3 will be insufficient, which may result in peeling, making it difficult to ensure insulation. Therefore, the thickness of the insulating coating 3 is set to 150 μm or more, and preferably 200 μm or more. On the other hand, the strength of the insulating coating 3 improves as the thickness of the insulating coating 3 having porosity, as described below, increases, so there is no particular upper limit to the thickness. However, if the thickness is too thick, it becomes difficult to control the size of the composite member 1 and the manufacturing cost increases. Furthermore, peeling is more likely to occur. Therefore, the thickness of the insulating coating 3 is preferably set to 800 μm or less, and more preferably 600 μm or less.

[0033] (Porosity of Insulating Coating) When an attempt is made to simply form a thick insulating coating in order to improve its strength, depending on the manufacturing method, a large number of pores may be generated inside the insulating coating, and the porosity may vary. As a result, the strength of the insulating coating may be significantly reduced. In this embodiment, the strength of the insulating coating 3 is ensured by reducing the porosity variation in the thickness direction of the insulating coating 3. More specifically, when a cross section of the insulating coating 3 parallel to the thickness direction is observed, the ratio (P1 / P2) of the porosity P1 in a predetermined region R1 to the porosity P2 in a predetermined region R2 is specified.

[0034] Region R1 is a rectangular region sampled from the interface between the insulating coating 3 and the substrate 2 to a depth of 100 μm in the film thickness direction, with sides of 75 μm in the film thickness direction and sides of 300 μm perpendicular to the film thickness direction. Region R2 is a rectangular region sampled from the surface of the insulating coating 3 to a depth of 100 μm in the film thickness direction, with sides of 75 μm in the film thickness direction and sides of 300 μm perpendicular to the film thickness direction. Porosities P1 and P2 are preferably obtained by sampling regions R1 and R2 from three locations within the above range and calculating the average porosity for each region, and more preferably by calculating the average porosity for each region from five locations within the above range.

[0035] When the ratio (P1 / P2) of the porosity P1 in region R1 to the porosity P2 in region R2 is 0.3 or greater and 3.0 or less, the porosity variation in the thickness direction of the insulating coating 3 is small, and excellent strength can be obtained. Therefore, the ratio (P1 / P2) of the porosity P1 to the porosity P2 is set to 0.3 or greater, preferably 0.35 or greater, and more preferably 0.4 or greater.

[0036] As described above, in this embodiment, the strength of the insulating coating 3 is ensured by minimizing the variation in porosity in the thickness direction of the insulating coating 3. However, if the porosity is lower near the substrate 2 than at the surface of the insulating coating 3 and the density of the insulating coating 3 is higher, peeling of the insulating coating 3 from the substrate 2 can be more effectively prevented, resulting in a high-strength insulating coating. Therefore, the ratio of porosity P1 to porosity P2 (P1 / P2) should be 3.0 or less. To further prevent peeling, however, it is preferably 2.0 or less, more preferably 1.5 or less, even more preferably 1.0 or less, and particularly preferably 0.9 or less. In the composite member 1 according to this embodiment shown in FIG. 1 , the ratio of porosity P1 to porosity P2 (P1 / P2) is 0.46.

[0037] In this embodiment, it is also preferable to specify a porosity P3 in a region R3 from the interface with the substrate 2 to the surface of the insulating coating 3 when observing a cross section of the insulating coating 3 in a direction parallel to the thickness of the insulating coating 3. If the porosity P3 is 10% or less, the number of pores will be reduced overall, and the spaces between the inorganic material 20 in the insulating coating 3 will approach a state in which the matrix 10 fills the spaces, making the entire insulating coating 3 dense, thereby ensuring sufficient strength of the insulating coating 3. Therefore, the porosity P3 is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

[0038] Region R3 refers to a rectangular region with sides in the thickness direction that are 90% of the thickness of insulating coating 3 and sides perpendicular to the thickness direction that are 300 μm. Preferably, region R3 is sampled from three locations within the above range and the porosity P3 is calculated by averaging the porosities of the respective regions, and more preferably, the porosity P3 is calculated by averaging the porosities of five locations within the above range.

[0039] Furthermore, in this embodiment, the porosity P1 and the porosity P2 are also preferably not more than predetermined values. A porosity P1 and a porosity P2 of 10% or less means that a large number of pores 30 are not generated only on the surface of the insulating coating 3 or only near the interface with the substrate 2, and the pores 30 do not vary widely, resulting in even greater strength. Therefore, the porosity P1 and the porosity P2 are both preferably not more than 10%, more preferably not more than 8%, and even more preferably not more than 6%.

[0040] In this embodiment, the porosities P1 to P3 are calculated using the following method. First, a micrograph is taken of a cross section of the composite member 1 on which the insulating coating 3 is formed, taken in a direction parallel to the thickness direction. Next, the pores 30 present in regions R1 to R3 are extracted from the obtained photograph, and the total area of ​​the pores 30 in each region is calculated. Then, the total area of ​​the pores 30 is divided by the area of ​​that region to calculate the porosities P1 to P3 in regions R1 to R3.

[0041] In the composite material 1 configured as described above, the base material 2 is not insulated by wrapping tape around it, but rather an insulating coating material is applied to the surface of the base material 2, forming an insulating coating 3 that adheres closely to the base material 2. Therefore, when manufacturing the composite material 1 according to this embodiment, no wrapping work is required, there are no problems with uneven winding, gaps, or peeling, and it can easily be made to fit complex shapes. In addition, the insulating coating 3 is made of silicone or silica sol (silica: SiO ２ Since the composite member 1 includes the matrix 10 containing a compound having a siloxane bond (Si—O—Si bond), such as ethylenediamine fluoride, and the inorganic material 20, the composite member 1 is less likely to deteriorate even when exposed to high temperatures, and can maintain excellent heat resistance and insulating properties. Furthermore, since the thickness and porosity of the insulating coating 3 are specified as described above, excellent strength can be obtained, and as a result, even better heat resistance and insulating properties can be obtained.

[0042] The material that constitutes the insulating coating in the composite material 1 according to this embodiment will be described in further detail below.

[0043] (Compound having siloxane bonds: silicone) Silicone, which is a suitable example of a compound having siloxane bonds and is contained in the matrix 10 of the insulating coating 3, is heated in the curing step of the coating material in the manufacturing method described below, whereby functional groups disappear and SiO bonds are generated. Furthermore, if a fire or the like occurs near the composite member and the insulating coating is heated to a temperature of, for example, 700°C or higher, the silicone will be thermally decomposed to form SiO ２ is generated. Then, this SiO ２ Since the insulating coating 3 containing silicone is not burned even when exposed to flames, the insulating coating 3 can obtain excellent heat resistance. That is, even when the composite member 1 according to this embodiment is heated at high temperatures, the insulating coating 3 adheres to the substrate 2 without peeling off, and excellent insulating properties and heat resistance can be maintained. Silicone includes silicone resin and silicone rubber, and either is acceptable, but the use of silicone resin is important because the SiO ２ This is preferable from the viewpoint of increasing the density.

[0044] (Inorganic Material) Inorganic material 20 has a high melting point and excellent heat resistance, and therefore, including inorganic material 20 in insulating coating 3 can further improve the heat resistance of insulating coating 3. Furthermore, inorganic material 20 can also function as a skeleton in insulating coating 3, thereby improving the strength of insulating coating 3.

[0045] The inorganic material 20 preferably contains a silicate compound. As described above, silicone, which is an example of a compound having a siloxane bond, is thermally decomposed to form SiO ２ However, silicate compounds can be converted into SiO ２ Since the silicate compound has the same components as those of the silicone matrix 10, it is possible to improve the bonding strength between the silicone matrix 10 and the inorganic material 20. The silicate compound preferably contains at least one selected from glass-based materials, mica, kaolin, talc, clay, pyrophyllite, montmorillonite, bentonite, wollastonite, xonotlite, zeolite, diatomaceous earth, and halloysite.

[0046] The main component of silica sol (silica), which is another suitable example of a compound having a siloxane bond, is SiO ２ and the silicate compound is silica sol (SiO ２ ), the bonding strength between the matrix 10 containing silica sol (silica) and the inorganic material 20 can also be improved.

[0047] It is also preferable that the inorganic material 20 contains at least one selected from silica, alumina, mullite, and zirconia. These materials have high melting points and high insulating properties. Therefore, including these materials in the insulating coating 3 can further improve the heat resistance and insulating properties of the insulating coating 3. When a busbar is used as an example of the composite member of the present invention, the expected heat exposure temperature of the busbar is equal to or higher than the melting point of the metal material typically used in the body of a busbar. In this embodiment, including silica, alumina, mullite, zirconia, or the like as the inorganic material 20 can prevent the busbar body from being exposed to high heat because these materials have melting points equal to or higher than the heat exposure temperature. Therefore, these materials are suitable for use as materials for the insulating coating 3 of a busbar.

[0048] The shape of inorganic material 20 preferably includes at least one selected from flakes, fibers, and particles. When inorganic material 20 has such a shape, the adhesive strength between inorganic material 20 and matrix 10 is increased when inorganic material 20 is dispersed in matrix 10, thereby improving the strength of insulating coating 3.

[0049] Furthermore, when the inorganic material 20 includes a glass-based material, it is preferable to use at least one selected from a flaky glass-based material, glass particles, and glass fibers as the glass-based material. Among these, the flaky glass-based material is oriented in a planar shape inside the insulating coating 3 and exhibits excellent insulating properties and heat resistance. Therefore, it is particularly preferable that the glass-based material includes a flaky glass-based material. Furthermore, for the same reasons as for the flaky glass-based material, it is particularly preferable that mica be used as the inorganic material 20.

[0050] The content of inorganic material 20 relative to all components in insulating coating 3 is preferably 3 to 70 volume %, more preferably 10 to 50 volume %, and even more preferably 20 to 40 volume %. If the content of inorganic material 20 is less than 3 volume %, sufficient insulation and heat resistance may not be obtained. On the other hand, if the content exceeds 70 volume %, the viscosity of the coating liquid used for dip coating becomes too high, resulting in poor film formability.

[0051] The content of the inorganic material 20 in the insulating coating 3 can be measured, for example, using a method similar to the porosity measurement method described above. Specifically, a cross section of the insulating coating 3 parallel to the thickness direction is photographed using an electron microscope, and any region within the photograph is selected. Portions of this region that are judged to be inorganic material are colored. The total area of ​​the colored region (inorganic material) is then divided by the area of ​​the selected region to calculate the content (volume %) of the inorganic material 20. The larger the size of the measurement region, the smaller the error. For example, a rectangular region can be selected, similar to the measurement region for porosity P3 described above, with sides measuring 90% of the thickness of the insulating coating 3 in the thickness direction and 300 μm in the direction perpendicular to the thickness direction. The content of the inorganic material 20 in the insulating coating 3 is preferably determined by sampling regions of the above size from three different locations within the insulating coating 3 and averaging the obtained content values. More preferably, it is determined by averaging the content values ​​obtained from five different locations.

[0052] In addition to the matrix 10 and inorganic material 20 described above, the insulating coating 3 may contain other materials such as a flame retardant, a dispersant, or a pigment, as long as the materials do not affect the insulating properties or heat resistance. As will be described later, the insulating coating 3 is formed by applying a coating material (coating liquid) to the surface of the substrate. In order to improve the application performance of the coating liquid containing the material of the matrix 10 and the inorganic material 20, it is preferable that the insulating coating 3 contain a thixotropic agent.

[0053] <Surface Layer> The composite member 1 may have a surface layer 4 made of the material of the matrix 10 on at least a portion of the surface of the insulating coating 3. Unlike the insulating coating 3, the surface layer 4 does not contain the inorganic material 20; it is made of only the material of the matrix 10. Therefore, the surface layer 4 has high adhesion to the insulating coating 3 and is harder and denser than the insulating coating 3, thereby providing the effect of protecting the surface of the insulating coating 3. Therefore, forming the surface layer 4 on at least a portion of the surface of the insulating coating 3 can suppress damage to the surface of the insulating coating 3 and cushion the impact of a colliding object. Furthermore, the formation of the surface layer 4 can also provide the effect of preventing powder shedding of the inorganic material 20, etc.

[0054] (Thickness of Surface Layer) When the composite material 1 has a surface layer 4, if the thickness of the surface layer 4 is 10 μm or more, the surface layer 4 can have the effect of protecting the insulating coating 3. Furthermore, if the thickness of the surface layer 4 is 100 μm or less, the size of the composite material 1 is not affected and an increase in manufacturing costs can be suppressed.

[0055] <Resin Layer> The composite material 1 may have a resin layer (not shown) on at least a portion of its surface, the resin layer containing a resin different from the matrix material. The resin layer may be made of an insulating resin, such as epoxy resin, nylon resin, SBR (styrene butadiene rubber), or silicone rubber. The composite material 1 having a resin layer can further improve its insulating properties and heat resistance. The resin layer may be formed on the surface of the insulating coating 3 or on the surface layer 4.

[0056] (Thickness of Resin Layer) When the composite material 1 has a resin layer, if the thickness of the resin layer is 100 μm or more, the effect of improving insulation and heat resistance can be sufficiently obtained. 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, if the thickness of the resin layer is 600 μm or less, it does not affect the size of the composite material 1 and can also suppress an increase in manufacturing costs. 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.

[0057] <Substrate> In this embodiment, the substrate 2 is not particularly limited, and the main body of various products to which the composite material 1 according to this embodiment is applied can be used as the substrate 2. For example, when a bus bar, which will be described later, is applied as the composite material 1, a conductive bus bar body can be used as the substrate 2. Note that the bus bar body is conductive, and the substrate itself is electrically conductive; however, in this embodiment, the substrate 2 to be coated with the insulating coating 3 is not limited to a conductive material. For example, a substrate made of a non-electrically conductive material can also be used.

[0058] [Specific Application Examples of the Composite Material] There are no particular limitations on the products to which the composite material 1 can be applied, but it can be applied, for example, to bus bars used to connect multiple battery cells or battery modules in an energy storage device. The configuration of the composite material 1 will be described below using a bus bar as an example.

[0059] FIG. 2 is a perspective view showing a busbar to which the composite member according to this embodiment is applied. Note that FIG. 2 shows the busbar (composite member) 100 in a state immediately before being attached to a battery cell 130. The busbar body (base material) 110 is, for example, a Z-shaped metal plate member. The busbar body is secured in place by inserting an electrode 135 of the battery cell 130 into a connection hole 115a at one end and covering it with a terminal cap 136. The busbar body 110 also has a connection hole 115b at the other end, which is used to connect an adjacent battery cell (not shown) or an external device (not shown). The busbar body 110 is covered with an insulating coating 3 throughout its entirety, excluding the connection holes 115a and 115b. This is how the busbar 100 is configured.

[0060] Although not shown in the figures, the busbar body 110 may be I-shaped overall or may have an irregular shape with curved portions, and may have various shapes depending on the installation location of the battery cell 130.

[0061] If the busbar body 110 has a shape with a bent portion 110a or a curved portion (not shown), such as the Z-shape shown in the figure, the following problems may occur. For example, in a method in which ceramic tape is wrapped around the body, as in the busbar disclosed in Patent Document 1, the wrapping process is time-consuming to prevent unevenness or gaps in the winding at the bent portion 110a or the curved portion. In addition, it is possible that gaps may occur in the ceramic tape due to vibration or the adhesive between the ceramic tape and the body may peel off.

[0062] In contrast, in the busbar 100 configured as described above, the busbar body 110 is not insulated by wrapping tape around it, but rather a material (coating liquid) for forming the insulating coating 3 is applied to the surface of the busbar body 110, forming the insulating coating 3 in close contact with the busbar body 110. Therefore, no wrapping operation is required when manufacturing the busbar 100, and there are no problems such as uneven winding, gaps, or peeling, and the busbar can easily be made into a complex shape.

[0063] Methods for applying the coating liquid to the surface of the busbar body 110 include "dip coating," in which the busbar body 110 is immersed in the coating liquid, and painting with a brush or spray. When dip coating is used, the insulating coating 3 is not formed on the connection holes 115a and 115b, so these areas are masked before being immersed in the coating liquid. In this way, the insulating coating 3 can be formed to cover at least a portion of the surface of the busbar body 110.

[0064] In addition to the bus bar, the composite member according to this embodiment can be applied to connectors, protective parts for battery modules, cases for electronic components, battery cells, battery modules, battery packs, or motor coils.

[0065] [Method for manufacturing composite member] The composite member according to this embodiment can be manufactured, for example, by the manufacturing method shown below. Figures 3A to 3D are schematic diagrams showing the manufacturing method for the composite member according to this embodiment in the order of steps. Note that the manufacturing method described below will be described for the case where the compound having a siloxane bond contained in the matrix 10 is silicone, but it can also be applied in the same way when the compound having a siloxane bond is silica sol (silica).

[0066] 3A , first, a first coating material (not shown) is applied to at least a portion of the surface of the substrate 2. The first coating material (coating liquid) is, for example, an organic solvent to which a silicone-containing matrix 10 material and an inorganic material 20 have been added.

[0067] (First Coating Material Drying Step) After the above-mentioned coating step, the first coating material is dried at a temperature of, for example, 50° C. In this first coating material drying step, the organic solvent is volatilized.

[0068] (First Coating Material Curing Step) The dried first coating material is then heated to a temperature of, for example, 200° C. to cure it. This first coating material curing step causes dehydration condensation of the silicone, forming the first layer 5 with a three-dimensional network structure. Numerous pores 30 are also formed in the first layer 5.

[0069] (First Immersion Process) The substrate 2 on which the first layer 5 has been formed is then immersed in a second coating material. The second coating material does not contain the inorganic material 20, but is an organic solvent to which the silicone-containing matrix 10 material has been added. The second coating material is then dried, for example, at a temperature of 50°C, and then heated, for example, at a temperature of 200°C to harden it. As shown in FIG. 3B , this immersion process causes the second coating material to fill some of the numerous pores 30 formed in the first layer 5, thereby reducing the porosity of the first layer 5. The second coating material may not contain the inorganic material 20 of the first coating material, or may be a material different from the material of the matrix 10.

[0070] 3C, a first coating material (not shown) is again laminated on the surface of the first layer 5. The first coating material (coating liquid) is the same material as that used in the first coating process. At this time, the first coating material also fills some of the pores 30 remaining in the first layer 5.

[0071] (Second drying step of the first coating material) After the above-mentioned coating step, the first coating material is dried at a temperature of, for example, 50° C. This second drying step of the first coating material volatilizes the organic solvent in the first coating material applied in the second coating step.

[0072] (Second First Coating Material Curing Process) The dried first coating material is then heated to a temperature of, for example, 200° C. and cured. This second first coating material curing process causes dehydration condensation of the silicone, forming a second layer 6 with a three-dimensional network structure. A large number of pores 30 are also formed in the second layer 6.

[0073] (Second Immersion Process) Then, as shown in FIG. 3D , the substrate 2 on which the second layer 6 has been formed is immersed in a second coating material. The second coating material is the same material as that used in the first immersion process. The second coating material is then dried, for example, at a temperature of 50°C, and then heated, for example, at a temperature of 200°C to harden it. This immersion process causes the second coating material to fill some of the numerous pores 30 formed in the second layer 6, thereby reducing the porosity of the second layer 6. Note that the second coating material used in the second immersion process may not contain the inorganic material 20 of the first coating material, or may be a material different from the material of the matrix 10.

[0074] The immersion time in the second immersion step may be the same as that of the first immersion step, or may be longer than that of the first immersion step. The second coating material penetrates into the second layer 6 from the surface thereof, but if the second coating material remains on the surface of the second layer 6 due to the long immersion time, it hardens as it is, forming a surface layer 4 on the surface of the second layer 6. This surface layer 4 is made of the second coating material remaining on the surface, and therefore has a dense structure that does not contain inorganic material 20.

[0075] (Resin Layer Forming Step) Thereafter, the resin layer 7 is formed on the surface layer 4 by, for example, electrostatic powder coating or fluidized bed dip coating of an epoxy resin paint. When forming the resin layer 7, part of the material constituting the resin layer 7 may penetrate into the layer below it.

[0076] According to the above manufacturing method, the first layer is formed by applying a first coating material to the substrate 2 and drying and curing it. Immersing this layer in a second coating material fills some of the pores 30 in the first layer with the second coating material. The second layer is then formed by applying a first coating material to the substrate 2 and drying and curing it. Immersing this layer in a second coating material fills not only the pores in the second layer but also the pores remaining in the first layer with the second coating material. For example, by extending the immersion time in the second immersion step, the pores remaining in the first layer can be filled with the second coating material to a greater extent. Therefore, when these steps are repeated while adjusting the immersion time to form an insulating coating 3 consisting of multiple layers, the porosity P1 of the region R1 near the substrate 2 can be made smaller than the porosity P2 of the region R2 on the surface of the insulating coating 3. As a result, the ratio of the porosity P1 to the porosity P2 (P1 / P2) can be set to 0.9 or less.

[0077] As described above, the second coating material used in the above immersion step may be the same as the first coating material used in the first immersion step, may not contain the inorganic material 20 of the first coating material, or may be a material different from the material of the matrix 10. However, from the viewpoint of affinity, it is preferable to use a material that is the same as the first coating material or that does not contain the inorganic material 20 of the first coating material. Furthermore, since the material of the matrix 10 is silicone, if the second coating material contains silicone, the amount of silicone increases, which further improves adhesion between the insulating coating 3 and the substrate and also increases the retention of the inorganic material 20. Furthermore, an increase in the amount of silicone increases the amount of SiO ２ This increases the resistance to fire and allows the insulating coating 3 to be more effectively maintained even when subjected to flames.

[0078] In the above-described manufacturing method, the series of steps from the deposition step to the immersion step was repeated twice, but it may be repeated multiple times until the desired film thickness is achieved. Even when the series of steps is repeated multiple times, since the immersion step is included in each repeated step, it is possible to form an insulating coating with low porosity and high strength.

[0079] Furthermore, in the above-described manufacturing method, the first coating material (coating liquid) is an organic solvent to which a silicone-containing matrix 10 material and an inorganic material 20 have been added, and the second coating material (coating liquid) does not contain the inorganic material 20 but is an organic solvent to which a silicone-containing matrix 10 material has been added. However, depending on the types of the first coating material and the second coating material, such as in the case of silica sol (silica), the composite member of the present invention can be obtained without performing the above-described immersion step.

[0080] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications or alterations within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present invention. Furthermore, the components of the above-described embodiments may be combined in any manner without departing from the spirit of the invention.

[0081] This application is based on a Japanese patent application (Patent Application No. 2023-170682) filed on September 29, 2023, the contents of which are incorporated herein by reference.

[0082] REFERENCE SIGNS LIST 1 composite member 2 substrate 3 insulating coating 4 surface layer 7 resin layer 10 matrix 20 inorganic material 30 pores 100 busbar 110 busbar body 115a, 115b connection hole 130 battery cell 135 electrode 136 terminal cap

Claims

1. A composite member having a substrate and an insulating coating covering at least a portion of a surface of the substrate, wherein the insulating coating has a thickness of 150 μm or more, and the insulating coating has a matrix containing a compound having a siloxane bond and an inorganic material dispersed in the matrix, wherein, when a cross section of the insulating coating parallel to a thickness direction is observed, the ratio (P1 / P2) of a porosity P1 in a rectangular region R1 ranging from an interface between the insulating coating and the substrate to 100 μm in the thickness direction, the region R1 having a side in the thickness direction of 75 μm and a side perpendicular to the thickness direction of 300 μm, to a porosity P2 in a rectangular region R2 ranging from the surface of the insulating coating to 100 μm in the thickness direction, the region R2 having a side in the thickness direction of 75 μm and a side perpendicular to the thickness direction of 300 μm, is 0.3 or more and 3.0 or less.

2. The composite material described in claim 1, characterized in that, when a cross section parallel to the thickness direction of the insulating coating is observed, the porosity P3 in a rectangular region R3 having a side length parallel to the thickness direction that is 90% of the thickness of the insulating coating and a side perpendicular to the thickness direction that is 300 μm is 10% or less.

3. The composite material according to claim 1, wherein the porosity P1 and the porosity P2 are both 10% or less.

4. The composite member according to claim 1, characterized in that at least a portion of the surface of said insulating coating has a surface layer made of the material of said matrix.

5. The composite material according to claim 4, wherein the thickness of the surface layer is 10 μm or more and 100 μm or less.

6. A composite member according to any one of claims 1 to 5, characterized in that at least a portion of the surface of the insulating coating has a resin layer containing a resin different from the material of the matrix.

7. The composite material according to claim 6, wherein the thickness of the resin layer is 100 μm or more and 600 μm or less.

8. The composite member according to any one of claims 1 to 5, wherein the compound having a siloxane bond is at least one of silicone and silica sol.

9. The composite member according to any one of claims 1 to 5, characterized in that the inorganic material contains at least one selected from the group consisting of silica, alumina, mullite and zirconia.

10. The composite member according to any one of claims 1 to 5, characterized in that the inorganic material 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.

11. The composite member according to any one of claims 1 to 5, characterized in that the inorganic material contains at least one type selected from the group consisting of flake-shaped, fibrous and particulate inorganic materials.

12. The composite member according to any one of claims 1 to 5, wherein the inorganic material includes at least one of a flake-like glass-based material and mica.

13. A composite member according to any one of claims 1 to 5, which is used as a bus bar for connecting a plurality of battery cells or battery modules.

14. The composite member according to any one of claims 1 to 5, which is applied to a connector, a protective part 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.

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