Composite member and method for forming insulating coating

Abstract

To provide an insulation film which exhibits excellent heat resistance in addition to excellent insulation, does not require a winding operation in contrast to ceramic tape, does not cause problems of gaps, peeling and uneven winding, and can also easily be adapted to conductive base materials having complex shapes.SOLUTION: In an insulation film 1, at least an inorganic material 20 is dispersed in a first matrix 10 comprising silicone. Further, a material of the first matrix 10 or a material of a second matrix being a different component than the first matrix 10 may be impregnated. The insulation film 1 is formed by, for example, dip coating.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an insulating coating, a method for forming the same, and a composite member in which an insulating coating is coated on a substrate, including a conductive substrate such as a bus bar. [Background technology]

[0002] Conductive members in which an insulating coating is formed on the surface of a metal piece are used to electrically connect components. For example, various electronic devices, electric vehicles or hybrid vehicles driven by electric motors, storage batteries, etc. are equipped with power storage devices in which multiple battery cells are connected in series or parallel by bus bars that are conductive members. In addition, lithium-ion secondary batteries, which are capable of higher capacity and higher output than lead-acid batteries, nickel-metal hydride batteries, etc., are mainly used as battery cells.

[0003] In a battery cell, an overcurrent may flow during charging and discharging, causing the busbar to heat up and, in some cases, to burst into flames. Therefore, the busbar is required to have heat resistance as well as insulation properties. For example, Patent Document 1 describes a busbar in which a ceramic tape such as mica tape is wrapped around a copper busbar body as a fire-resistant layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] China Utility Model No. 216902355 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in Patent Document 1, the ceramic tape needs to be wound around the busbar body. Due to spatial restrictions on the installation location of the battery cells, the busbar may have a complex shape, and when the busbar has a complex shape, it is difficult to wrap the ceramic tape around every corner of the busbar body. If the ceramic tape has uneven winding or gaps, sufficient insulation and heat resistance cannot be obtained. It is also expected that the adhesive surface of the ceramic tape may peel off. Furthermore, nylon tape is wound around the outside of the mica tape as an insulating layer, but nylon tape is weak against heat and has problems with heat resistance.

[0006] Therefore, an object of the present invention is to provide an insulating coating that has excellent heat resistance in addition to insulation properties, does not require wrapping work as with ceramic tape, does not have problems such as uneven wrapping, gaps, or peeling, and can be easily adapted to complex shapes. [Means for solving the problem]

[0007] The above object of the present invention can be achieved by the following configuration [1] relating to an insulating coating.

[0008] [1] An insulating coating comprising at least an inorganic material dispersed in a first matrix containing silicone.

[0009] Further, preferred embodiments of the present invention relating to the insulating coating relate to the following [2] to [9].

[0010] [2] The insulating coating according to [1], characterized in that at least a portion of the film surface has a layer made of the first matrix material. [3] The insulating coating according to [1] or [2], characterized in that the content of the first matrix is ​​a gradient composition in which the content increases toward the film surface. [4] The insulating coating according to any one of [1] to [3], characterized in that at least a portion of the film surface has a layer made of a second matrix material having a different composition from the first matrix. [5] The insulating coating according to [4], characterized in that the content of the second matrix is ​​a gradient composition in which the content is higher closer to the film surface. [6] The insulating coating according to any one of [1] to [5], wherein the inorganic material is at least one selected from the group consisting of silica, alumina, mullite, and zirconia. [7] The insulating coating according to any one of [1] to [5], wherein the inorganic material is 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. [8] The insulating coating according to any one of [1] to [7], wherein the inorganic material is at least one selected from the group consisting of flakes, fibers, and particles. [9] The insulating coating according to any one of [1] to [5], wherein the inorganic material contains at least one of a flake glass material and mica.

[0011] The above object of the present invention can be achieved by the following configuration

[10] relating to a method for forming an insulating coating.

[0012]

[10] A method for forming an insulating coating, comprising: immersing a substrate in a coating liquid containing a first matrix material and at least an inorganic material, and then drying the coating liquid adhered to the substrate.

[0013] Moreover, a preferred embodiment of the present invention relating to a method for forming an insulating coating relates to the following

[11] .

[0014]

[11] A method for forming an insulating coating according to

[10] , characterized in that the substrate on which the insulating coating has been formed is immersed in a coating liquid containing the first matrix material or a second matrix material having components different from those of the first matrix to impregnate the substrate.

[0015] The above object of the present invention is achieved by the following configuration

[12] relating to a composite member.

[0016]

[12] A composite material, comprising a substrate, at least a portion of which is coated with the insulating coating according to any one of [1] to [9].

[0017] Furthermore, preferred embodiments of the present invention relating to a composite member relate to the following

[13] and

[14] .

[0018]

[13] The composite material according to

[12] , characterized in that the substrate is a bus bar that connects multiple battery cells or battery modules.

[0019]

[14] The composite member according to

[12] , wherein the substrate is 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. Effect of the Invention

[0020] The insulating coating of the present invention has a silicone matrix, and silicone is thermally decomposed and functional groups are lost to form SiO bonds, which then change to SiO2. SiO2 is not burned even when exposed to flames, and has high heat resistance. Inorganic materials also have excellent heat resistance. Furthermore, both silicone and inorganic materials have excellent insulation properties.

[0021] In addition, by impregnating the insulating coating with silicone as a matrix and inorganic material dispersed therein with a matrix material, the volatile components of the film material evaporate during film formation and fill the air bubbles that occur in the insulating coating, making the insulating coating denser and increasing the film strength. In addition, the matrix material remains on at least a part of the surface of the insulating coating and hardens to form a layer as a top coat, preventing powdering of the inorganic material and damage to the film surface and increasing impact resistance.

[0022] Furthermore, the method for forming the insulating coating is a dip coating using a coating liquid containing a matrix and an inorganic material, so the manufacturing process is simple. Also, impregnation with the matrix material is simple, since it is only necessary to immerse the material in the matrix material.

[0023] The insulating coating is particularly useful for covering conductive members such as bus bars. In this case, since it is a dip coating, wrapping work such as ceramic tape is not required, and there are no problems such as uneven wrapping, gaps, or peeling, and it can easily be applied to complex shapes. In addition, since silicone and inorganic materials have excellent heat resistance, they can be fully used even if, for example, a battery cell of an electricity storage device to which the bus bar is applied experiences thermal runaway and a flame occurs. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a photograph, substituted for a drawing, showing a cross section of an insulating coating according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a photograph showing a cross section of an insulating coating according to a second embodiment of the present invention. [Diagram 3] FIG. 3 is a perspective view that illustrates a bus bar, which is a conductive member, as an example of the composite member of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a test apparatus used in the examples. [Diagram 5] FIG. 5 shows the results of observing whether or not the insulating coating 1A (test piece A / invention example) and the mica tape (test piece B / comparative example) peeled off after heating using the test apparatus shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, the 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 modified and implemented as desired without departing from the gist of the present invention.

[0026] [Insulating coating] (First embodiment) 1 is a photograph of a cross section of an insulating coating according to the present embodiment. In the insulating coating 1, an inorganic material (white lines in the figure: reference number 20) is dispersed in a first matrix containing silicone (gray portion in the figure: reference number 10).

[0027] When silicone is thermally decomposed, functional groups disappear and SiO bonds are generated, which are then burned away and converted into SiO2. SiO2 is not burned away even when exposed to flames, and the insulating coating 1 has excellent heat resistance. Silicone includes silicone resin and silicone rubber, and either may be used, but silicone resin is preferred from the viewpoint of making the SiO2 formed high density.

[0028] As described later, the insulating coating 1 is obtained by dip coating, and in order to improve the coating performance of the coating liquid containing the material of the first matrix 10 and the inorganic material 20, it is preferable to use a thixotropic agent in combination.

[0029] The inorganic material 20 has a high melting point and is excellent in heat resistance, and preferably contains a silicate compound. As described above, silicone can be converted into SiO2 by thermal decomposition, but the silicate compound has the same components as the SiO2 formed by silicone, and therefore the bonding strength between the first matrix 10 containing silicone and the inorganic material 20 is increased. The silicate compound is preferably at least one selected from glass-based materials, mica, kaolin, talc, clay, pyrophyllite, montmorillonite, bentonite, wollastonite, xonotlite, zeolite, diatomaceous earth, and halloysite.

[0030] Furthermore, the inorganic material 20 is preferably at least one selected from silica, alumina, mullite, and zirconia, from the viewpoint of having a high melting point and high insulating properties. When a busbar, which is a conductive member, is used as an example of the composite member of the present invention, these materials are suitable for use in the insulating coating 1 for the busbar, since they are inorganic materials having melting points that are equal to or higher than the melting points of metal materials used in general busbar bodies and equal to or higher than the expected heat exposure temperature.

[0031] Furthermore, it is preferable that the inorganic material 20 be at least one type selected from the group consisting of flake, fiber, and particulate, because when the inorganic material 20 is dispersed in the first matrix 10, the adhesion to the first matrix 10 is increased, thereby contributing to improving the strength of the insulating coating 1.

[0032] In addition, when the inorganic material 20 contains a glass-based material, the glass-based material is preferably at least one selected from flake glass, glass particles, and glass fibers. Among these, flake glass is particularly preferably contained, since flake glass is oriented in a planar shape in the film and exhibits excellent insulation and heat resistance. In addition, the above-mentioned mica is also preferably used for the same reason as flake glass.

[0033] The content of inorganic material 20 relative to all components in insulating coating 1 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 properties 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.

[0034] Furthermore, both silicone and inorganic material 20 are useful as components of insulating coating 1 because they have excellent heat resistance and insulating properties.

[0035] In addition to the above-described first matrix 10 and inorganic material 20, insulating coating 1 may contain other materials such as a flame retardant, a dispersant, and a pigment, as long as the insulating properties and heat resistance are not affected.

[0036] Second embodiment The insulating coating 1 of the first embodiment has an inorganic material 20 dispersed in a first matrix 10, but volatile components of the film material evaporate during film formation, generating air bubbles in the insulating coating 1. In Fig. 1, the black parts are air bubbles 30, and many of them are scattered throughout the film.

[0037] Therefore, in order to fill the air bubbles 30, the insulating coating 1 of the first embodiment is impregnated with the same material as the first matrix 10, or in some cases with a second matrix material having a different component from the first matrix (hereinafter collectively referred to as "matrix material"). That is, the insulating coating 1A of the second embodiment is obtained by filling the air bubbles 30 of the insulating coating 1 of the first embodiment with a matrix material, making the coating denser and increasing the film strength. FIG. 2 is a cross-sectional photograph of the insulating coating 1A of the second embodiment, and it can be seen that the air bubbles 30, unlike the insulating coating 1 of the first embodiment, are hardly visible, but rather the air bubbles 30 are filled with the matrix material.

[0038] From the standpoint of affinity, the impregnated matrix material is preferably the same as the first matrix 10 of the insulating coating 1. In addition, because the first matrix 10 is silicone, an increase in the amount of silicone improves adhesion to the substrate on which the insulating coating 1A is formed, and also increases the retention of the inorganic material 20. Furthermore, an increase in the amount of silicone also results in an increase in the amount of SiO2, so that the insulating coating 1A is more effectively maintained even when exposed to flames.

[0039] The material of the second matrix also preferably has high affinity with the material of the first matrix, and is preferably the same material as the first matrix 10. Even when the material of the second matrix is ​​used, the heat resistance due to SiO2 derived from silicone is maintained since the first matrix 10 exists in the film.

[0040] Since the matrix material penetrates into the membrane from the membrane surface, a part of the matrix material remains on the membrane surface and hardens as it is to form a layer. Also, if the amount of matrix material is sufficiently large, the remaining matrix material spreads over the membrane surface in addition to the part that is soaked into the membrane, hardens as it is to form a layer. Depending on the amount of matrix material, a layer may be formed to cover the entire membrane surface.

[0041] That is, in the insulating coating 1A, a layer 40 is present on a part of or the entire surface of the film, as shown in Fig. 2. Such layer 40 acts as a top coat, preventing powdering of the inorganic material 20, etc., suppressing damage to the film surface, and mitigating the impact of a colliding object.

[0042] Furthermore, since the insulating coating 1A is obtained by further impregnating the matrix material, the composition has a gradient in which the amount of matrix material increases toward the film surface. This is particularly advantageous in that it can more effectively prevent powdering of the inorganic material 20 and the like, suppress damage to the film surface, and cushion the impact of a colliding object.

[0043] [Method of forming insulating film] Since the matrix material is liquid, it is preferable to use dip coating as a method for forming the insulating coating. Dip coating does not require wrapping work as in the case of ceramic tape, and the process is simple. In addition, there are no problems such as uneven wrapping, gaps, or peeling, and it can easily be applied to conductive substrates with complex shapes.

[0044] That is, to form the insulating coating 1 of the first embodiment, the substrate is immersed in a coating liquid containing the first matrix material and at least an inorganic material, and after being pulled out, the coating liquid is dried.

[0045] To form the insulating coating 1A of the second embodiment, the substrate on which the insulating coating 1 has been formed is immersed in a coating liquid containing a matrix material to impregnate the substrate, and then the substrate is pulled out and the coating liquid is dried. The amount of impregnated matrix material is controlled by the immersion time.

[0046] [Conductive material] The present invention also relates to a conductive member in which a conductive base material is coated with the insulating coating 1 or the insulating coating 1A. There are no limitations on the conductive member, but here, a bus bar used to connect multiple battery cells or battery modules in an energy storage device will be described as an example.

[0047] 3 is an exploded perspective view showing a state in which a busbar 100 according to this embodiment is attached to a battery cell 130. The busbar body 110 is, for example, a metal plate member having an overall Z-shape, and an electrode 135 of the battery cell 130 is inserted into a connection hole 115a at one end and fixed by covering it with a terminal cap 136. An adjacent battery cell (not shown) or an external device (not shown) is connected to a connection hole 115b at the other end of the busbar body 110. The busbar body 110 is covered with an insulating coating 1 or an insulating coating 1A except for connection holes 115a and 115b to form the busbar 100.

[0048] Although not shown in the drawings, the busbar body 110 can have various shapes depending on where the battery cell 130 is installed, such as an overall I-shape or an irregular shape with a curved portion.

[0049] If the busbar body 110 has a shape with bent portions 110a and curved portions (not shown), such as the Z-shape shown in the figure, then in the method of wrapping ceramic tape around the busbar in Patent Document 1, it is expected that the wrapping work will be time-consuming in order to prevent uneven winding or gaps around the bent portions 110a and curved portions, or that gaps will occur due to vibration or the adhesive will peel off. However, in this embodiment, such problems do not occur because the insulating coating 1 or insulating coating 1A is formed by "dip coating".

[0050] In manufacturing bus bar 100, connection holes 115a, 115b are masked and immersed in a coating liquid when "dip coating" is performed.

[0051] Because the insulating coating 1 or insulating coating 1A that covers the bus bar 100 contains silicone, even if it is exposed to flames from a battery cell 130 that has experienced thermal runaway, it will not be burned up due to the generation of SiO.

[0052] [Composite material] The present invention is not limited to the above-mentioned conductive member, but also relates to a composite member in which a substrate is coated with the above-mentioned insulating coating 1 or insulating coating 1A. There are no particular limitations on the composite member, and examples of the composite member include a substrate other than a bus bar, which is an example of the above-mentioned conductive member, such as 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.

[0053] When applied to a bus bar, the conductive substrate is one in which the substrate itself is electrically conductive; however, the substrate to be coated with insulating coating 1 or insulating coating 1A of the present invention is not limited to this, and the present invention is not limited to substrates in which the substrate itself is not electrically conductive. EXAMPLES

[0054] In this example, the technical effect of the insulating coating 1A according to the example of the invention was verified.

[0055] First, a coating liquid containing silicone resin and mica was applied to a copper plate (C1100) measuring 30 mm x 75 mm and 2 mm thick, and the coating liquid on the copper plate was then dried and cured to form an intermediate insulating coating 1A. Next, the intermediate insulating coating 1A thus formed was further impregnated with silicone resin, and then dried and cured to produce test piece A comprising insulating coating 1A on a copper plate. The final thickness of insulating coating 1A formed by further impregnation with silicone resin was 1006 μm.

[0056] For comparison, test piece B was prepared by wrapping two layers of mica tape having a thickness of 150 μm around the same copper plate.

[0057] Then, the presence or absence of peeling of insulating coating 1A (test piece A / invention example) and mica tape (test piece B / comparative example) after heating was observed using a test device shown in Fig. 4. Test device 200 is composed of an aluminum movable part 220, one end of which is fitted with test piece 210, and a base 230 that rotatably supports the other end of movable part 220 and is suspended from a support stand 250. One end (the test piece side) of movable part 220 is lifted by hand so that it forms a predetermined angle θ with base 230, and when the hand is released, it collides with base 230 in a pendulum-like trajectory (arrow in the figure).

[0058] In the test, assuming that the busbar would be subjected to flames from a battery cell experiencing thermal runaway, test piece A or test piece B was heated in an electric furnace at approximately 1000°C for a prescribed time (60 minutes), and then test piece A or test piece B was attached to movable part 220 and collided with base part 230 at angles θ of 15°, 30°, 60°, and 90°, respectively. After the collision, the state of damage to insulating coating 1A of test piece A and the mica tape of test piece B was visually confirmed.

[0059] The test results are shown in Figure 5. As shown in Figure 5, in the case of test piece A, which is an example of the invention, no peeling was observed in the insulating coating 1A of test piece A after the first repeated test, regardless of whether the impact was made from an angle θ of 15°, 30°, or 60°. Furthermore, when the impact was made from an angle θ of 90°, no peeling was observed in the insulating coating 1A of test piece A even after the fifth repeated test.

[0060] On the other hand, in the case of test piece B, which is a comparative example, no peeling was observed in the mica tape of test piece B after the first repeated test when it was collided from an angle of θ = 15°, 30°, or 60°. However, when it was collided from an angle of θ = 90°, peeling was observed in the mica tape of test piece B after the second repeated test (see the arrow in the figure).

[0061] This shows that the insulating coating 1A of the test piece A, which is an example of the invention, maintains a sufficient coating even when exposed to high temperatures, and is suitable for use as a bus bar, for example. [Explanation of symbols]

[0062] 1,1A Insulation coating 10 The First Matrix 20 Inorganic materials 30 Bubbles 40 layers 100 Busbar 110 Busbar body 115a, 115b Connection holes 130 Battery Cells 135 Electrode 136 Terminal Cap 200 Test Equipment 210 Test Piece 220 Moving parts 230 base 250 Support stand

Claims

1. A composite member in which at least a portion of a substrate, which is a bus bar connecting a plurality of battery cells or battery modules, is coated with an insulating coating, A composite member, characterized in that the insulating coating has a film in which at least an inorganic material is dispersed in a first matrix containing silicone, and at least a portion of the film surface has a layer made of a second matrix material having a different composition from the first matrix.

2. A composite member as described in claim 1, characterized in that at least a portion of the membrane surface has a layer made of the first matrix material.

3. 3. The composite member according to claim 1, wherein the content of the first matrix is ​​a gradient composition in which the content is higher closer to the membrane surface.

4. 3. The composite member according to claim 1, wherein the inorganic material is at least one selected from the group consisting of silica, alumina, mullite, and zirconia.

5. 3. The composite material according to claim 1, wherein the inorganic material is 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.

6. 3. The composite member according to claim 1, wherein the inorganic material is in at least one form selected from the group consisting of flakes, fibers, and particles.

7. 3. The composite member according to claim 1, wherein the inorganic material includes at least one of a flake-like glass-based material and mica.

8. A method for forming an insulating coating, comprising: immersing a substrate, which is a bus bar connecting a plurality of battery cells or battery modules, in a coating liquid containing a first matrix material and at least an inorganic material, and then drying the coating liquid adhered to the substrate, A method for forming an insulating coating, comprising immersing and impregnating the substrate on which the insulating coating is formed into a coating liquid containing a second matrix material having components different from those of the first matrix.

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