Composite member and method for manufacturing same

Abstract

Provided are a composite member that is excellent in insulation property and heat resistance and enables suppression of detachment or the like of an insulating coating film at a corner part which is especially likely to be damaged by collision between the composite members or between the composite member and another component, and a method for manufacturing the same. The composite member (20) comprises a base material (25) and an insulating coating film (10) that covers at least a part of the surface of the base material (25). The base material (25) includes a pair of opposing main surface parts (25a), a plurality of end surface parts (25b) that connect the pair of main surface parts (25a) to each other, and a corner part (25c) between the main surface part (25a) and the end surface part (25b). Porosity P1 of the insulating coating film (10) formed on the corner part (25c) of the base material (25) is smaller than porosity P2 of the insulating coating film (10) formed on the main surface part (25a) of the base material (25).

Description

Composite member and manufacturing method thereof

[0001] The present invention relates to a composite member in which a substrate is coated with an insulating coating, and a method for producing the same.

[0002] Conductive members, 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] Furthermore, with the recent increase in demand for electric vehicles and other vehicles, there is a demand for smaller, more energy-efficient power storage devices. This has led to increasingly complex internal structures for power storage devices, resulting in bus bars with more complex shapes and being used in confined spaces. Furthermore, when mass-produced bus bars are used to manufacture power storage devices, a large number of bus bars must be transported. Thus, when the bus bars are transported or used in confined spaces, the corners of the bus bars may come into contact with each other, damaging the insulating coating.

[0007] The present invention has been made in consideration of these problems, and aims to provide a composite material and a method for manufacturing the same that has excellent insulation and heat resistance, does not require wrapping work like ceramic tape, is free from problems such as uneven wrapping, gaps, and peeling, can easily accommodate complex shapes, and can suppress peeling of the insulating coating at corners that are particularly susceptible to damage when composite materials collide with each other or with other parts.

[0008] The above object of the present invention is achieved by the following configuration [1] relating to a composite member.

[0009] [1] A composite member having a substrate and an insulating coating covering at least a portion of a surface of the substrate, wherein the substrate has a pair of opposing main surface portions, a plurality of end surface portions connecting the pair of main surface portions, and corner portions between the main surface portions and the end surface portions, and wherein a porosity P1 of the insulating coating formed on the corner portions of the substrate is lower than a porosity P2 of the insulating coating formed on the main surface portions of the substrate.

[0010] Furthermore, preferred embodiments of the present invention relating to the composite member relate to the following [2] to

[10] .

[0011] [2] The composite member according to [1], wherein a porosity P3 of the insulating coating formed on the end surface portion is higher than a porosity P1 of the insulating coating formed on the corner portion and lower than a porosity P2 of the insulating coating formed on the main surface portion.

[0012] [3] The composite material according to [1] or [2], wherein the ratio (P1 / P2) of the porosity P1 to the porosity P2 is 0.01 or more and 0.5 or less.

[0013] [4] The composite material according to any one of [1] to [3], characterized in that the porosity P1 is 0.1% or more and 10% or less, and the porosity P2 is 2% or more and 50% or less.

[0014] [5] The composite material according to [2], wherein the porosity P3 is 1% or more and 30% or less.

[0015] [6] The composite member according to any one of [1] to [5], characterized in that the insulating coating has a matrix containing a compound having a siloxane bond and an inorganic material dispersed in the matrix.

[0016] [7] The composite member according to [6], 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.

[0017] [8] The composite material according to [6] or [7], wherein the compound having a siloxane bond is at least one of silicone and silica sol.

[0018] [9] The composite member according to any one of [1] to [8], which is applied to a bus bar that connects a plurality of battery cells or battery modules.

[0019]

[10] The composite material according to any one of [1] to [8], 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.

[0020] The above object of the present invention is achieved by the following configuration

[11] relating to a method for producing a composite member.

[0021]

[11] A method for manufacturing a composite member according to any one of [1] to

[10] , comprising: a coating step of coating a first coating material onto at least a portion of a surface of the base material; and a first coating material hardening step of hardening the first coating material to form the insulating coating containing the first coating material, characterized in that the insulating coating is formed such that a porosity P1 of the insulating coating at the corners of the base material is lower than a porosity P2 of the insulating coating at the main surface of the base material.

[0022] Furthermore, preferred embodiments of the present invention relating to a method for manufacturing a composite member relate to the following

[12] to

[22] .

[0023]

[12] The method for producing a composite member according to

[11] , wherein the first coating material includes a matrix material containing a compound having a siloxane bond and an inorganic material.

[0024]

[13] The method for producing a composite member according to

[12] , wherein the compound having a siloxane bond contained in the first coating material is at least one of silicone and silica sol.

[0025]

[14] The method for manufacturing a composite member according to any one of

[11] to

[13] , wherein the insulating coating formed on the end surface portions has a porosity P3 that is higher than the porosity P1 of the insulating coating formed on the corner portions and lower than the porosity P2 of the insulating coating formed on the main surface portions.

[0026]

[15] The method for producing a composite member according to any one of

[11] to

[14] , wherein in the coating step, the substrate is coated with the first coating material by immersing it in the first coating material.

[0027]

[16] The method for manufacturing a composite member according to any one of

[11] to

[15] , characterized in that a first coating material drying step of drying the first coating material is provided between the deposition step and the first coating material hardening step.

[0028]

[17] The method for manufacturing a composite member according to any one of

[11] to

[16] , further comprising: a second coating material immersion step of immersing the substrate, on which a coating made of the first coating material has been formed, in a second coating material after the first coating material hardening step; and a second coating material hardening step of hardening the second coating material.

[0029]

[18] The method for manufacturing a composite member according to

[17] , characterized in that the second coating material is a material that constitutes at least a part of the insulating coating and is made of a matrix material containing a compound having a siloxane bond.

[0030]

[19] The method for producing a composite member according to

[18] , wherein the compound having a siloxane bond contained in the second coating material is at least one of silicone and silica sol.

[0031]

[20] The method for manufacturing a composite member according to any one of

[17] to

[19] , characterized in that a second coating material drying step of drying the second coating material is provided between the second coating material immersion step and the second coating material hardening step.

[0032]

[21] The method for producing a composite member according to any one of

[11] to

[20] , characterized in that, before the deposition step, a blasting treatment step is performed on the base material so that the surface roughness Ra is 1 μm or more.

[0033]

[22] The method for producing a composite member according to

[12] , characterized by comprising a resin layer forming step of applying a resin material containing a resin different from the matrix material to at least a part of the surface and curing the resin material to form a resin layer.

[0034] In the composite member of the present invention, an insulating coating covers at least a portion of the substrate, and the porosity P1 of the insulating coating formed on the corners of the substrate is lower than the porosity P2 of the insulating coating formed on the main surfaces of the substrate, thereby improving strength at the corners, which are particularly prone to peeling, and providing excellent thermal insulation at the main surfaces. Furthermore, the manufacturing method of the composite member of the present invention makes it possible to manufacture the above composite member, thereby easily manufacturing a composite member with an excellent balance between strength and thermal insulation.

[0035] FIG. 1 is a photograph, in lieu of a drawing, showing a busbar to which a composite member according to an embodiment of the present invention is applied. FIG. 2 is a schematic diagram showing an enlarged portion of a cross section of the composite member shown in FIG. 1 taken along the line A-A. FIG. 3 is a schematic diagram illustrating a method for measuring the porosity of an insulating coating on a main surface and an end surface of a substrate. FIG. 4A is a micrograph showing a portion of an insulating coating on a corner of a substrate in a composite member according to an embodiment of the present invention. FIG. 4B is a micrograph showing a portion of an insulating coating on a main surface of a substrate in the composite member shown in FIG. 4A. FIG. 4C is a micrograph showing a portion of an insulating coating on a corner of a substrate in a composite member according to another embodiment of the present invention. FIG. 4D is a micrograph showing a portion of an insulating coating on a main surface of a substrate in the composite member shown in FIG. 4C. FIG. 5A is a diagram showing the steps of a method for manufacturing a composite member according to an embodiment of the present invention, and is a schematic diagram showing a coating step. FIG. 5B is a diagram showing the steps of a method for manufacturing a composite member according to an embodiment of the present invention, and is a schematic diagram showing a first coating material hardening step. 5C and 5D are diagrams showing the steps of the method for producing a composite member according to the present embodiment, each diagram showing a second coating material immersion step and a resin layer formation step, respectively.

[0036] The present inventors conducted extensive research to obtain 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 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 can result in the formation of numerous pores within the insulating coating, which can reduce the strength of the insulating coating, particularly at corners, and can lead to peeling.

[0037] Therefore, the present inventors focused on the porosity of the insulating coating and discovered that the above problem can be solved by making the porosity of the insulating coating formed on the corner portions lower than the porosity of the insulating coating formed on the main surface portions.

[0038] 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.

[0039] [Composite Member] FIG. 1 is a photograph showing a busbar to which a composite member according to this embodiment is applied. FIG. 1 also shows the state in which a composite member (busbar) 20 is attached to a battery cell 110. The composite member 20 has a substrate (busbar body) 25 and an insulating coating 10 that covers at least a portion of the surface of the substrate 25. The substrate 25, made of a conductive material, is, for example, a Z-shaped metal plate. An electrode 111 of the battery cell 110 is inserted into a connection hole 26a at one end, and a terminal cap 112 is attached to secure the substrate 25. An adjacent battery cell (not shown) or an external device (not shown) is connected to a connection hole 26b at the other end of the composite member 20.

[0040] FIG. 2 is a schematic diagram showing an enlarged portion of the cross section of the composite member 20 shown in FIG. 1 taken along the line A-A. As shown in FIG. 1, the bus bar is, for example, a Z-shaped plate-like member. However, in this specification, the characteristics of the composite member 20 will be described using, as an example, a flat plate-like member excluding the bent portion. The substrate 25 has a pair of opposing main surface portions 25a, a plurality of end surface portions 25b connecting the pair of main surface portions 25a, and corner portions 25c between the main surface portions 25a and the end surface portions 25b. The corner portions 25c are rounded in cross section, and the outer surfaces of the insulating coatings 10 formed in the areas of the corner portions 25c are also rounded.

[0041] The surface of the insulating coating 10 on the main surface 25 a is nearly flat, but the insulating coating 10 formed on the corners 25 c and end surfaces 25 b has a gently curved surface. A plurality of pores (not shown in FIG. 2 ) are formed inside the insulating coating 10. In this embodiment, the porosity P1 of the insulating coating 10 formed on the corners 25 c of the substrate 25 is lower than the porosity P2 of the insulating coating 10 formed on the main surface 25 a of the substrate 25.

[0042] In the composite member of this embodiment configured in this manner, the porosity P1 of the insulating coating 10 at the corner 25c is lower than the porosity P2 of the insulating coating 10 at the main surface 25a, so that peeling can be suppressed at the corner 25c, where peeling is particularly likely to occur.

[0043] Furthermore, when the composite member 20 is applied to a bus bar, the insulating coating 10 may be hit by metal fragments from a battery cell 110 that has experienced thermal runaway, fragments of the insulating coating from other bus bars, or fragments of the battery case 120. In this embodiment, the porosity P1 of the insulating coating 10 formed on the corners 25 c is low and the density is high, and the outer surface of the insulating coating 10 formed on the corners 25 c has an R-shape. Therefore, even if flying fragments or the like collide with the outer surface of the insulating coating 10, damage to the insulating coating 10 by the fragments or the like can be minimized. Furthermore, because the surface of the insulating coating 10 formed on the corners 25 c has an R-shape, colliding fragments or the like are reflected obliquely, thereby mitigating the impact of the fragments or the like on the composite member 20.

[0044] Furthermore, if the composite member 20 has a shape with a bent portion 25d or a curved portion (not shown), such as the Z-shape shown in FIG. 1 , wrapping the ceramic tape around the bus bar as in the bus bar of Patent Document 1 becomes cumbersome. Specifically, the wrapping process requires time and effort to ensure that there are no uneven windings or gaps around the bent portion 25d or curved portion. Furthermore, even when the composite member 20 is in use, it is possible that gaps may occur between the substrate 25 and the tape due to vibrations or the like, or that the adhesive may peel off.

[0045] In contrast, in this embodiment, the insulating coating 10 can be formed by applying an insulating varnish to the surface of the substrate 25. Therefore, the above-mentioned problem does not occur. Details of the method for forming an insulating coating on the surface of the substrate 25 so as to reduce the porosity P1 at the corners 25c will be described later. In this way, the insulating coating 10 formed by applying an insulating varnish to the surface of the substrate 25 and drying it is superior in terms of removability and workability, unlike insulating layers formed by wrapping tape or the like.

[0046] 2, corners 25c of substrate 25 have a rounded cross-sectional shape, but in the present invention, the cross-sectional shape of corners 25c is not particularly limited and may have a substantially right-angled shape. In either case, it is preferable that the surface of insulating coating 10 at corners 25c of substrate 25 has a rounded cross-sectional shape.

[0047] Next, specific porosities P1, P2, and P3 of the corner portions 25c, the main surface portion 25a, and the end surface portion 25b of the substrate 25 will be described in detail below.

[0048] (Porosity P1 of the Insulating Coating at Corners) In particular, in components with rectangular cross sections, corners are prone to force due to collisions with other components or vibrations. Therefore, if the insulating coating 10 formed at the corners 25c of the substrate 25 has many pores, the insulating coating 10 becomes brittle and is easily damaged at the corners 25c by small impacts or vibrations. On the other hand, if the insulating coating 10 at the corners 25c has few pores, the spaces between, for example, inorganic materials in the insulating coating 10 are closer to being filled with a matrix, making the insulating coating 10 in this region denser and providing sufficient strength. Therefore, the porosity P1 is preferably 10% or less, more preferably 8% or less, and even more preferably 6% or less.

[0049] The fewer pores in insulating coating 10 at corners 25c, the more effectively peeling can be prevented, but the additional steps required to reduce the pores increase manufacturing costs. Therefore, the porosity P1 of insulating coating 10 at corners 25c is preferably 0.1% or greater, more preferably 1% or greater, and even more preferably 2% or greater.

[0050] (Porosity P2 of the Insulating Coating on the Main Surface Portion) As shown in FIG. 1 , when the composite member 20 according to this embodiment is used as a bus bar, the insulating coating 10 preferably suppresses the transfer of heat generated by the substrate 25 to the outside. Because the pores in the insulating coating 10 also have the effect of improving thermal insulation, in this embodiment, the porosity P2 of the insulating coating 10 on the main surface portion 25 a is set higher than the porosity P1 of the insulating coating 10 on the corners 25 c. This improves the strength of the insulating coating 10 at the corners 25 c and also improves the thermal insulation provided by the insulating coating 10 on the main surface portion 25 a. Specifically, if the insulating coating 10 on the main surface portion 25 a has fewer pores, the thermal insulation on the main surface portion 25 a side may be reduced. Therefore, the porosity P2 of the insulating coating 10 on the main surface portion 25 a is preferably 2% or more, more preferably 4% or more, and even more preferably 6% or more.

[0051] On the other hand, if the number of pores in the insulating coating 10 on the main surface portion 25a becomes too large, the strength of the insulating coating 10 decreases and peeling becomes more likely to occur. Therefore, the porosity P2 of the insulating coating 10 on the main surface portion 25a is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less.

[0052] (Porosity P3 of the Insulating Coating at the End Surfaces) The end surfaces 25b of the substrate 25 are less susceptible to damage to the insulating coating than the corners 25c, but more susceptible to damage than the main surfaces 25a. However, because the end surfaces 25b have a larger area than the corners 25c, they are also required to provide thermal insulation. Therefore, the porosity P3 of the insulating coating 10 formed on the end surfaces 25b is preferably higher than the porosity P1 of the insulating coating 10 formed on the corners 25c. Furthermore, the porosity P3 of the insulating coating 10 formed on the end surfaces 25b is preferably lower than the porosity P2 of the insulating coating 10 formed on the main surfaces 25a. Specifically, the porosity P3 of the insulating coating 10 on the end surfaces 25b is preferably 1% or higher, more preferably 3% or higher, and even more preferably 5% or higher. Furthermore, the porosity P3 of insulating coating 10 at end surface portion 25b is preferably 30% or less, more preferably 20% or less, and even more preferably 10% or less.

[0053] (Ratio (P1 / P2) of Porosity P1 to Porosity P2) By setting the ratio of porosity P1 to porosity P2 to a small value, a well-balanced composite member 20 can be obtained, having high strength at the corner portions 25c and excellent heat insulation at the main surface portions 25a. Therefore, the ratio (P1 / P2) of porosity P1 to porosity P2 is preferably 0.5 or less, more preferably 0.4 or less, and even more preferably 0.3 or less. Note that, since the smaller the ratio (P1 / P2) of porosity P1 to porosity P2, the more likely the manufacturing process will become complicated, the ratio (P1 / P2) is preferably 0.01 or more, more preferably 0.02 or more, and even more preferably 0.05 or more.

[0054] 2 and 3, a method for measuring the porosities P1 to P3 of the insulating coating 10 at the corners 25c, main surfaces 25a, and end surfaces 25b of the substrate 25 will be described below. If the composite member 20 has bent or curved portions, the composite member 20 is cut near the bent or curved portion to form a rectangular, flat member, and the porosity of the insulating coating 10 is measured using this cut member.

[0055] To measure the porosity P1 of the insulating coating 10 formed at the corner 25c of the substrate 25, a micrograph is first taken of a cross section perpendicular to the direction in which the corner 25c extends. Because the corner 25c may have a rounded shape, as shown in FIG. 2 , the position where the rounded shape begins from the main surface 25a to the end surface 25b of the substrate 25 is designated as point a, and an auxiliary line 35 is drawn parallel to the end surface 25b from point a. The position where the rounded shape ends at the end surface 25b is designated as point b, and an auxiliary line 36 is drawn parallel to the main surface 25a from point b. Pores 14 present in any three regions between the auxiliary lines 35 and 36 are then extracted, and the total area of ​​the pores 14 in the three regions is divided by the total area of ​​the regions to calculate the porosity P1 of the insulating coating 10 at the corner 25c.

[0056] To measure the porosity P2 of the insulating coating formed on the main surface portion 25a of the substrate 25, two pairs of opposing corners 25c extending linearly around one of the pair of main surfaces 25a of the substrate 25 are each divided into three equal parts, thereby dividing the main surface portion 25a into nine regions, as shown in Figure 3. In this embodiment, a micrograph is taken of a cross section perpendicular to the main surface portion 25a of the central main surface region 30 (shown by a thick solid line in Figure 2) of the nine regions. Then, for any three regions photographed, the total area of ​​the pores 14 is divided by the total area of ​​the region to calculate the porosity P2 of the insulating coating 10 on the main surface portion 25a.

[0057] The method for measuring the porosity P3 of the insulating coating formed on the end surface 25b of the substrate 25 is similar to the method for measuring the porosity P2 of the insulating coating on the main surface 25a. As shown in FIG. 3 , two pairs of opposing sides surrounding the end surface 25b of the substrate 25 on which the insulating coating 10 is formed are each divided into thirds, thereby dividing the end surface 25b into nine regions. In this embodiment, a micrograph is taken of a cross section perpendicular to the end surface 25b of the end surface central region 31 (shown by a thick dashed line in FIG. 2 ) among the nine regions. The porosity P3 of the insulating coating 10 on the end surface 25b can then be calculated by dividing the total area of ​​the pores 14 in any three regions photographed by the total area of ​​the region. Note that if the thickness of the substrate 25 is extremely small and it is difficult to divide the end surface 25b into three equal parts in the thickness direction, it is not necessary to divide it into three equal parts exactly; instead, a substantially central region can be selected.

[0058] Fig. 4A is a micrograph showing a portion of an insulating coating at a corner of a substrate in a composite member according to an embodiment of the present invention, and Fig. 4B is a micrograph showing a portion of an insulating coating on a main surface of the substrate in the composite member shown in Fig. 4A. Fig. 4C is a micrograph showing a portion of an insulating coating at a corner of a substrate in a composite member according to another embodiment of the present invention, and Fig. 4D is a micrograph showing a portion of an insulating coating on a main surface of the substrate in the composite member shown in Fig. 4C. As shown in Figs. 4A and 4C, insulating coating 10 formed on the surface of corner 25c of substrate 25 comprises, for example, inorganic material 13 contained in matrix 12, and a plurality of pores 14 are formed in insulating coating 10. 4B and 4D, the insulating coating 10 formed on the surface of the main surface portion 25a of the substrate 25 also contains an inorganic material 13 in a matrix 12, but the porosity P2 of the pores 14 in the insulating coating 10 is greater than the porosity P1 of the pores 14 shown in FIGS. 4A and 4C, respectively.

[0059] More specifically, the porosity P1 of the insulating coating 10 formed on the corner 25c of the substrate 25 shown in Figure 4A was 7.4%, and the porosity P2 of the insulating coating 10 formed on the main surface 25a of the substrate 25 shown in Figure 4B was 15.6%. Therefore, the ratio of porosity P1 to porosity P2 (P1 / P2) was 0.47. Furthermore, the porosity P1 of the insulating coating 10 formed on the corner 25c of the substrate 25 shown in Figure 4C was 0.2%, and the porosity P2 of the insulating coating 10 formed on the main surface 25a of the substrate 25 shown in Figure 4D was 3.9%. Therefore, the ratio of porosity P1 to porosity P2 (P1 / P2) was 0.05.

[0060] The material constituting the insulating coating 10 and the preferred film thickness thereof in the composite member 20 according to this embodiment will be described in further detail below.

[0061] <Insulating Coating> The insulating coating 10 preferably has a matrix 12 containing a compound having a siloxane bond and an inorganic material 13 dispersed in this matrix 12. Both the compound having a siloxane bond and the inorganic material 13 are materials with excellent heat resistance and insulating properties, and therefore, when the compound having a siloxane bond and the inorganic material 13 are included as components of the insulating coating 10, an insulating coating with excellent heat resistance and insulating properties can be obtained.

[0062] 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 12 is preferably at least one of silicone and silica sol, and more preferably silicone. It is also a preferred embodiment that the matrix 12 contains both silicone and silica sol.

[0063] (Compound Having Siloxane Bonds: Silicone) Silicone, which is a suitable example of a compound having siloxane bonds and is contained in the matrix 12 of the insulating coating 10, is heated during the curing process of the coating material in the manufacturing method described below, whereby the functional groups disappear and SiO bonds are generated. Furthermore, if a fire or the like occurs near the composite member and the insulating coating 10 is heated to a temperature of, for example, 700°C or higher, the silicone will thermally decompose and produce SiO ２ is generated. Then, this SiO ２ Since the insulating coating 10 containing silicone is not burned even when exposed to flames, the insulating coating 10 can have excellent heat resistance. That is, in the composite member 20 according to this embodiment, even when heated at high temperatures, the insulating coating 10 adheres to the substrate 25 without peeling off, and excellent insulating properties and heat resistance can be maintained. Silicone includes silicone resin and silicone rubber, and either can be used, but the use of silicone resin is important because the SiO ２ This is preferable from the viewpoint of increasing the density.

[0064] (Inorganic Material) Inorganic material 13 has a high melting point and excellent heat resistance, and therefore, including inorganic material 13 in insulating coating 10 can further improve the heat resistance of insulating coating 10. Furthermore, inorganic material 13 can also function as a skeleton in insulating coating 10, thereby improving the strength of insulating coating 10.

[0065] The inorganic material 13 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, it is possible to improve the bonding strength between the silicone matrix and the inorganic material. 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.

[0066] 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 12 containing silica sol (silica) and the inorganic material 13 can also be improved.

[0067] It is also preferable that the inorganic material 13 contains at least one selected from silica, alumina, mullite, zirconia, and calcium carbonate. These materials have high melting points and high insulating properties. Therefore, including these materials in the insulating coating 10 can further improve the heat resistance and insulating properties of the insulating coating 10. When the composite member 20 according to this embodiment is used in a busbar, the expected heat exposure temperature of the busbar is equal to or higher than the melting point of the metal material typically used in busbar bodies. In this embodiment, when the inorganic material 13 contains silica, alumina, mullite, zirconia, calcium carbonate, or the like, these materials have melting points equal to or higher than the heat exposure temperature, thereby preventing the busbar body from being exposed to high heat. Therefore, these materials are suitable for use in the insulating coating 10.

[0068] The shape of inorganic material 13 preferably includes at least one selected from flakes, fibers, and particles. When inorganic material 13 has such a shape, the adhesive strength between inorganic material 13 and matrix 12 is increased when inorganic material 13 is dispersed in matrix 12, thereby improving the strength of insulating coating 10.

[0069] Furthermore, when the inorganic material 13 includes a glass-based material, it is preferable to use at least one selected from a glass-based material flake, glass particles, and glass fibers as the glass-based material. Among these, the glass-based material flake is oriented in a planar shape inside the insulating coating 10 and exhibits excellent insulating properties and heat resistance. Therefore, it is particularly preferable that the glass-based material include a glass-based material flake. Furthermore, it is particularly preferable to use mica as the inorganic material 13 for the same reasons as the glass-based material flake.

[0070] (Inorganic Material Content) The manufacturing method for the composite member 20 according to this embodiment will be described later. One method for making the porosity P1 of the insulating coating 10 at the corners 25c of the substrate 25 smaller than the porosity P2 of the insulating coating at the main surfaces 25a is to appropriately control the content of the inorganic material 13. If the content of the inorganic material 13 is less than 1% by volume, sufficient insulation and heat resistance may not be achieved. On the other hand, if the content of the inorganic material 13 exceeds 20% by volume, the viscosity of the coating liquid during manufacturing may be too high, potentially preventing the difference between the porosity P1 at the corners 25c and the porosity P2 at the main surfaces 25a from appearing. Therefore, the content of the inorganic material 13 relative to the total components of the insulating coating 10 is preferably 1 to 20% by volume, more preferably 3 to 15% by volume, and even more preferably 5 to 10% by volume.

[0071] An example of a method for measuring the content of inorganic material 13 in the insulating coating 10 is described below. For example, a cross section perpendicular to the main surface 25a is photographed using an electron microscope, and any region within the photograph is selected. Portions of this region that are identified as containing inorganic material 13 are then colored. The total area of ​​the colored regions (inorganic material) is then divided by the area of ​​the selected region to calculate the content (volume %) of inorganic material 13. The larger the region to be measured and the greater the number of measurement regions, the smaller the error. For example, a rectangular region with a side length in the thickness direction of the insulating coating 10 that is 90% of the film thickness and a side length perpendicular to the film thickness direction of 300 μm can be selected as the size of the measurement region. If the content of inorganic material 13 in the insulating coating 10 varies among the main surface 25a, the end surface 25b, and the corner 25c, it is preferable to sample regions of the above size from multiple different locations in each region and calculate the average of the obtained content values. As for the number of measurement regions, it is preferable to calculate the content from three different locations for each of the insulating coatings 10 formed on the main surface portion 25 a, the end surface portion 25 b, and the corner portion 25 c, and then calculate the average for the entire region, and it is more preferable to calculate from five different locations for each.

[0072] In addition to the matrix 12 and inorganic material 13 described above, insulating coating 10 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, insulating coating 10 is formed by applying a coating material (coating liquid) to the surface of a substrate. In order to improve the application performance of the coating liquid containing the material of matrix 12 and inorganic material 13, it is preferable that insulating coating 10 contain a thixotropic agent.

[0073] (Thickness of the insulating coating) If the thickness of the insulating coating 10 is less than 150 μm, the strength of the insulating coating 10 will be insufficient, and peeling may occur, making it difficult to ensure insulation. Therefore, the thickness of the insulating coating 10 is preferably 150 μm or more, and more preferably 200 μm or more. On the other hand, the thicker the insulating coating 10, the greater its strength. However, if the thickness is too thick, it becomes difficult to control the size of the composite member 20 and the manufacturing cost increases. Furthermore, peeling is more likely to occur. Therefore, the thickness of the insulating coating 10 is preferably 800 μm or less, and more preferably 600 μm or less.

[0074] The thickness of the insulating coating 10 can be obtained by measuring the distance from the surface of the insulating coating 10 to the surface of the substrate 25 in the thickness direction of the insulating coating 10 .

[0075] Furthermore, the composite member 20 according to this embodiment may have a surface layer made of a matrix material, which will be described later, or a resin layer made of another material, on at least a portion of the surface of the insulating coating 10. The surface layer, resin layer, substrate, etc. will be further described below.

[0076] <Surface Layer> The insulating coating 10 in the composite member 20 may have a surface layer made of the matrix material (e.g., second layer 52 in FIG. 5C , described later) on at least a portion of its surface. Unlike the coating made of the first coating material (first layer 51 in FIG. 5C , described later), which contains inorganic material 13, the surface layer is made of only the matrix material 12. This provides high adhesion to the coating made of the first coating material and is harder and denser than the coating, thereby providing protection for the insulating coating 10. Therefore, the presence of a surface layer on at least a portion of the surface of the insulating coating 10 can suppress damage to the surface of the insulating coating 10 and cushion the impact of a colliding object. Furthermore, the presence of a surface layer can also provide the effect of preventing powder shedding of the inorganic material 13, etc.

[0077] (Thickness of Surface Layer) When insulating coating 10 has a surface layer, if the thickness of the surface layer is 10 μm or more, the surface layer can provide the effect of protecting insulating coating 10. Furthermore, if the thickness of the surface layer is 100 μm or less, the size of composite member 20 is not affected and an increase in manufacturing costs can be suppressed.

[0078] <Resin Layer> The composite material 20 may have a resin layer containing a resin different from the matrix material on at least a portion of its surface. The resin layer may be made of an insulating resin, such as epoxy resin, nylon resin, SBR (styrene butadiene rubber), silicone rubber, or PVC (polyvinyl chloride). The composite material 20 having a resin layer can further improve its insulation and heat resistance. The resin layer may be formed on the surface of the insulating coating 10 or on the surface layer.

[0079] (Thickness of Resin Layer) When the composite material 20 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 20 and can 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.

[0080] <Substrate> In the present embodiment, the substrate 25 is not particularly limited, and the main body portion of various products to which the composite material 20 according to the present embodiment is applied can be used as the substrate 25. For example, when the composite material 20 is applied to a bus bar, a conductive material can be used as the substrate 25, which serves as the bus bar main body. Note that the bus bar main body is conductive and electrically conductive, but in the present embodiment, the substrate 25 to be covered with the insulating coating 10 is not limited to a conductive material. For example, a substrate made of an electrically non-conductive material can also be used.

[0081] [Specific Application Examples of the Composite Material] There are no particular limitations on the products to which the composite material 20 can be applied. In addition to the bus bar shown in FIG. 1 , the composite material 20 can be applied to connectors, protective parts for battery modules, cases for electronic components, battery cells, battery modules, battery packs, or motor coils.

[0082] [Method for manufacturing composite member] The composite member according to this embodiment can be manufactured, for example, by the manufacturing method shown below. Figures 5A to 5D 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 12 is silicone, but it can also be applied in the same way when the compound having a siloxane bond is silica sol (silica).

[0083] 5A , first, the first coating material 11 is applied to at least a portion of the surface of the substrate 25 by dip coating, in which the substrate 25 is immersed in a liquid first coating material 11. The first coating material 11 is, for example, an organic solvent to which a matrix 12 material containing silicone (a compound having a siloxane bond) and an inorganic material 13 have been added. When the manufactured composite member is to be applied to a bus bar, it is necessary to avoid forming an insulating coating 10 on the connection holes of the bus bar body. Therefore, it is preferable to mask the area including the connection holes before immersing the substrate in the first coating material 11.

[0084] (First Coating Material Drying Step) After the above-mentioned coating step, the first coating material 11 is dried at a temperature of, for example, 50° C. In this first coating material drying step, the organic solvent is volatilized.

[0085] 5B, the dried first coating material 11 is then heated to a temperature of, for example, 200°C to harden it. This hardening process of the first coating material causes dehydration condensation of the silicone, forming an insulating coating made of a first layer 51 with a three-dimensional network structure. Furthermore, numerous pores 14 are formed in the insulating coating 10.

[0086] According to the manufacturing method of the present embodiment, the viscosity of the first coating material 11 can be controlled by appropriately adjusting the content of inorganic material in the first coating material 11. Furthermore, by immersing the substrate 25 in the first coating material 11 having a predetermined viscosity, the porosity P1 of the insulating coating at the corners of the substrate 25 can be made smaller than the porosity P2 of the insulating coating at the main surface. The mechanism by which the porosity P1 is adjusted by this method is unclear, but it is thought that when the substrate 25 is lifted from the immersion in the first coating material 11, only the liquid portion of the first coating material 11 migrates to the larger main surface due to surface tension. As a result, the liquid content of the insulating coating at the main surface is higher than that at the corners, and numerous pores 14 are formed during the subsequent drying and curing steps of the first coating material.

[0087] In the coating step, the method for applying the first coating material to the surface of the substrate 25 is not limited to dipping, and a coating method may also be used. Furthermore, if the immersion step described below is performed following the first coating material curing step, the porosity P1 of the insulating coating 10 at the corners of the substrate 25 can be reduced.

[0088] (Second Coating Material Immersion Process) Then, as shown in FIG. 5C , the substrate 25 on which the first layer 51 has been formed is immersed in a second coating material. The second coating material, for example, does not contain the inorganic material 13 and is obtained by adding a silicone-containing matrix 12 material to an organic solvent. This immersion process fills some of the numerous pores 14 formed in the first layer 51 with the second coating material, thereby reducing the porosity of the first layer 51. Furthermore, excess second coating material that has not been absorbed into the pores 14 remains on the surface of the first layer 51. The second coating material may not contain the inorganic material 13 of the first coating material, or may be a material different from the material of the matrix 12.

[0089] Generally, the first layer 51 formed by dip coating or application tends to have a smaller thickness at the corners 25c of the substrate 25 and a larger thickness at the main surface 25a. The thickness of the first layer 51 at the end surface 25b of the substrate 25 tends to be larger than the thickness of the first layer 51 at the corners 25c and smaller than the thickness of the first layer 51 at the main surface 25a. In the second coating material immersion step, a smaller thickness of the first layer 51 facilitates penetration of the second coating material into the vicinity of the substrate 25.

[0090] (Second Coating Material Drying and Curing Process) The second coating material is then dried, for example, at 50°C, and then heated and cured, for example, at 200°C. This hardens the second coating material that has filled the pores of the first layer 51, and a second layer 52 made of a silicone-containing matrix 12 material is formed on the surface of the first layer 51. This results in the formation of an insulating coating 10 consisting of the first layer 51 and the second layer (surface layer) 52. In the present invention, the second coating material may be cured without drying, but performing the drying process prevents the resulting layer from expanding during the curing process. Therefore, performing the drying process is preferable. Due to the film thickness relationship described above, the porosity of the insulating coating 10 formed during the second coating material drying and curing process is highest at the main surface 25a, followed by the porosity P2 at the end surface 25b and the porosity P1 at the corners 25c, in that order.

[0091] For example, the insulating coating 10 shown in Figures 4A and 4B was formed by repeating the steps of applying a first coating material and curing the first coating material three times, followed by a step of immersing the second coating material in a second coating material and a step of curing the second coating material. The insulating coating 10 shown in Figures 4C and 4D was formed by repeating the steps of applying a first coating material and curing the first coating material once, followed by a step of immersing the second coating material in a second coating material and a step of curing the second coating material twice.

[0092] As shown in Figures 4A to 4D, by repeating the second coating material immersion process, the porosity P1 of the insulating coating 10 formed on the corner portion 25c of the substrate 25 and the porosity P2 of the insulating coating 10 formed on the main surface portion 25a are both reduced.

[0093] (Resin Layer Forming Step) In this embodiment, a resin layer may be formed as needed. As shown in FIG. 5D , a resin layer 7 may be formed on the surface of the second layer 52, i.e., the surface of the insulating coating 10, by electrostatic powder coating or fluidized bed dip coating of a resin material containing a resin different from the material of the matrix 12, such as an epoxy resin paint. This forms a composite member 20 having the insulating coating 10 and the resin layer 7 on the substrate 25. When forming the resin layer 7, part of the material constituting the resin layer 7 may permeate into the first layer 51 or the second layer 52.

[0094] According to the method for manufacturing a composite member according to the first embodiment, the porosity P1 of the insulating coating 10 at the corners 25c of the substrate 25 can be made lower than the porosity P2 of the insulating coating 10 on the main surfaces 25a of the substrate 25. As a result, the insulating coating 10 can be formed to have excellent strength at the corners 25c and excellent heat insulating properties on the main surfaces 25a.

[0095] In the above-described method for manufacturing a composite member, a blasting step is preferably performed on the substrate 25 before the coating step in which the first coating material is applied to the surface of the substrate 25. While there are no particular limitations on the surface roughness of the substrate 25 obtained by the blasting step, if the surface roughness Ra of the substrate 25 is 1 μm or greater, the bonding area between the substrate 25 and the first coating material increases, thereby ensuring sufficient adhesion between the two and preventing peeling of the insulating coating 10. Therefore, the blasting step is preferably performed so that the substrate has a surface roughness Ra of 1 μm or greater, and more preferably so that the surface roughness Ra is 2 μm or greater.

[0096] The surface roughness Ra of the substrate 2 can be measured in accordance with JIS B 0031. In this embodiment, the surface roughness Ra represents an average value of surface roughness measured at any three points on the surface of the substrate 2.

[0097] Furthermore, in the above-described manufacturing method, the first coating material is applied to the surface of the substrate 25, and then the substrate is immersed in the second coating material. However, the process of applying the first coating material and the process of immersing the substrate in the second coating material may be repeated multiple times until the desired film thickness is achieved.

[0098] In the above-described manufacturing method, the first coating material (coating liquid) is an organic solvent to which a silicone-containing matrix 12 material and an inorganic material 13 have been added, and the second coating material (coating liquid) is an organic solvent to which a silicone-containing matrix 12 material has been added, without including the inorganic material 13. However, depending on the types of the first coating material and the second coating material, such as silica sol (silica), the composite member of the present invention can be obtained without performing the above-described immersion step.

[0099] 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.

[0100] This application is based on a Japanese patent application (Patent Application No. 2024-030515) filed on February 29, 2024, the contents of which are incorporated herein by reference.

[0101] 7 Resin layer 10 Insulating coating 11 First coating material 12 Matrix 13 Inorganic material 14 Pores 20 Composite material 25 Base material 25a Main surface portion 25b End surface portion 25c Corner portion 25d Bent portion 26a, 26b Connection holes 51 First layer 52 Second layer 110 Battery cell 111 Electrode 120 Battery case P1, P2, P3 Porosity

Claims

1. A composite member having a substrate and an insulating coating covering at least a portion of the surface of the substrate, wherein the substrate has a pair of opposing main surfaces, a plurality of end surfaces connecting the pair of main surfaces, and corners between the main surfaces and the end surfaces, and wherein the porosity P1 of the insulating coating formed on the corners of the substrate is lower than the porosity P2 of the insulating coating formed on the main surfaces of the substrate.

2. A composite member as described in claim 1, characterized in that the porosity P3 of the insulating coating formed on the end surface portion is higher than the porosity P1 of the insulating coating formed on the corner portion and lower than the porosity P2 of the insulating coating formed on the main surface portion.

3. The composite material according to claim 1, wherein the ratio (P1 / P2) of the porosity P1 to the porosity P2 is 0.01 or more and 0.5 or less.

4. The composite material according to claim 1, wherein the porosity P1 is 0.1% or more and 10% or less, and the porosity P2 is 2% or more and 50% or less.

5. The composite material according to claim 2, wherein the porosity P3 is 1% or more and 30% or less.

6. The composite member according to claim 1, wherein the insulating coating has a matrix containing a compound having a siloxane bond and an inorganic material dispersed in the matrix.

7. The composite member according to claim 6, characterized in that at least a portion of the surface of said insulating coating has a resin layer containing a resin different from the material of said matrix.

8. The composite member according to claim 6, wherein the compound having a siloxane bond is at least one of silicone and silica sol.

9. The composite member according to claim 1, which is used as a bus bar connecting a plurality of battery cells or battery modules.

10. The composite member according to claim 1, 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.

11. A method for producing a composite member as set forth in any one of claims 1 to 10, comprising: a coating step of coating at least a portion of the surface of the substrate with a first coating material; and a first coating material hardening step of hardening the first coating material to form the insulating coating containing the first coating material, characterized in that the porosity P1 of the insulating coating at the corners of the substrate is lower than the porosity P2 of the insulating coating on the main surface of the substrate.

12. The method for manufacturing a composite member according to claim 11, wherein the first coating material includes a matrix material containing a compound having a siloxane bond and an inorganic material.

13. The method for manufacturing a composite member according to claim 12, wherein the compound having a siloxane bond contained in the first coating material is at least one of silicone and silica sol.

14. A method for manufacturing a composite member as described in claim 11, characterized in that the porosity P3 of the insulating coating formed on the end surface portion is formed to be higher than the porosity P1 of the insulating coating formed on the corner portion and lower than the porosity P2 of the insulating coating formed on the main surface portion.

15. The method for producing a composite member according to claim 11, wherein in the coating step, the substrate is coated with the first coating material by immersion.

16. A method for manufacturing a composite member according to claim 11, characterized in that a first coating material drying step of drying the first coating material is provided between the application step and the first coating material hardening step.

17. A method for manufacturing a composite member as described in claim 11, characterized in that after the first coating material hardening step, the method comprises: a second coating material immersion step of immersing the substrate on which the coating of the first coating material has been formed in a second coating material; and a second coating material hardening step of hardening the second coating material.

18. A method for manufacturing a composite member as described in claim 17, characterized in that the second coating material is a material that constitutes at least a part of the insulating coating and is made of a matrix material containing a compound having a siloxane bond.

19. The method for manufacturing a composite member according to claim 18, wherein the compound having a siloxane bond contained in the second coating material is at least one of silicone and silica sol.

20. A method for manufacturing a composite member as described in claim 17, characterized in that a second coating material drying step for drying the second coating material is provided between the second coating material immersion step and the second coating material hardening step.

21. A method for manufacturing a composite member according to claim 11, characterized in that, prior to the deposition step, a blasting treatment step is performed on the substrate so that the surface roughness Ra is 1 μm or more.

22. A method for manufacturing a composite member according to claim 12, characterized in that it includes a resin layer forming step of applying a resin material containing a resin different from the matrix material to at least a portion of the surface and curing the resin material to form a resin layer.

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