Cover protector and battery module

Abstract

Provided is a cover protector capable of maintaining excellent adhesive performance without delamination of a multilayer structure even when exposed to high heat or flames from a battery cell causing thermal runaway, and thereby capable of protecting a heat insulating material from scattered matter and maintaining excellent heat insulating performance. The cover protector (1) has a heat insulating material (2) and an inorganic fiber sheet (3) adhered to the heat insulating material (2) by an adhesive (4). The oxygen index of the cover protector (1) is greater than 24.7% as measured in accordance with JIS K7201-2, and the viscosity at 250°C of an adhesive material constituting the adhesive (4) is 40 Pa·s or more.

Description

Cover protector and battery module

[0001] The present invention relates to a cover protector and a battery module including the cover protector.

[0002] In recent years, lithium-ion secondary batteries have been used in electric vehicles and other vehicles to protect the environment. However, because lithium-ion secondary batteries use an organic electrolyte, there is a risk of fire occurring if the battery ignites during thermal runaway, which could damage the battery pack. Therefore, various insulating materials have been proposed to protect the battery pack even in the event of a fire.

[0003] For example, Patent Document 1 proposes a heat insulating fireproof material for automobile power batteries, which is composed of a surface layer, an adhesive layer, and an intermediate layer. The edges of the fireproof material are sealed by adhesive or sewing, which can prevent leakage of the aerogel felt powder used as the intermediate layer. When a heat insulating material is formed from multiple layers, it is necessary to bond the multiple layers together, for example, to prevent the heat insulating material from decomposing even in the event of a fire.

[0004] Chinese Patent Application Publication No. 107914428

[0005] However, when exposed to high heat or flames from a battery cell experiencing thermal runaway, the adhesive between the surface layer and the intermediate layer or the edges of the bonded fire-resistant material may disappear near the center of the heat or flame. Furthermore, since not only the center but also the peripheral areas become hot, if the adhesive performance at high temperatures is insufficient, the surface layer and the intermediate layer will peel off. As a result, the insulation performance and protection performance from flying debris cannot be maintained.

[0006] In the fire-resistant material described in Patent Document 1, an adhesive layer is disposed between the surface layer and the intermediate layer, and the edges are joined by adhesive or sewing, but when an adhesive is used, sufficient consideration is not given to adhesive performance at high temperatures. In addition, joining by sewing is a time-consuming process and increases the number of work steps, which increases manufacturing costs.

[0007] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a cover protector that is easy to manufacture, has a multilayer structure that maintains excellent adhesive performance without peeling even when exposed to high heat or flames from a battery cell that has experienced thermal runaway, and thereby protects the insulating material from flying debris and maintains excellent insulating performance. Another aim of the present invention is to provide a battery module equipped with a cover protector that has the above-mentioned insulating and adhesive performance.

[0008] The above object of the present invention is achieved by the following configuration [1] relating to the cover protector.

[0009] [1] A cover protector having a heat insulating material and an inorganic fiber sheet bonded to the heat insulating material with an adhesive, characterized in that the oxygen index measured in accordance with JIS K 7201-2 is greater than 24.7%, and the viscosity of the adhesive material constituting the adhesive at 250°C is 40 Pa·s or greater.

[0010] Further, preferred embodiments of the present invention relating to the cover protector relate to the following [2] to

[12] .

[0011] [2] The cover protector according to [1], characterized in that, when the ratio of the area of ​​the inorganic fiber sheet covered with the adhesive to the total area of ​​the area facing the thermal insulating material on the surface of the inorganic fiber sheet is defined as the adhesive coverage, the adhesive coverage is 0.50 or more.

[0012] [3] The cover protector according to [2], characterized in that the coverage of the adhesive is 0.76 or more.

[0013] [4] The cover protector according to any one of [1] to [3], characterized in that the oxygen index is 26.0% or more.

[0014] [5] The cover protector according to any one of [1] to [4], wherein the adhesive material contains a polyamide-based organic material.

[0015] [6] The cover protector according to [5], characterized in that the content of the polyamide-based organic material is 80 mass % or more with respect to the total mass of the adhesive material.

[0016] [7] The cover protector according to any one of [1] to [6], characterized in that the heat insulating material contains inorganic particles, and a joint portion containing the adhesive and a portion of the inorganic particles is provided between the heat insulating material and the inorganic fiber sheet.

[0017] [8] The cover protector according to any one of [1] to [7], characterized in that the inorganic fiber sheet is a sheet-shaped inorganic fiber containing at least one type of fiber selected from silica fiber, alumina fiber, glass fiber, and metal fiber.

[0018] [9] A cover protector having a heat insulating material and an inorganic fiber sheet adhered to the heat insulating material with an adhesive, wherein the inorganic fiber sheet has recesses and protrusions on the surface facing the heat insulating material, and at least one of the heat insulating material and the adhesive constituting the heat insulating material is present in at least a portion of the inside of the recesses of the inorganic fiber sheet.

[0019]

[10] The cover protector according to [9], wherein the inorganic fiber sheet is formed into a sheet shape by weaving together weft and warp threads made of inorganic fiber, and the recesses of the inorganic fiber sheet are located at the boundaries between the weft and the warp threads in a plan view of the inorganic fiber sheet.

[0020]

[11] The cover protector according to [9] or

[10] , wherein the surface roughness Ra of the inorganic fiber sheet on the heat insulating material side is 50 μm or more and 100 μm or less.

[0021]

[12] The cover protector according to any one of [9] to

[11] , characterized in that a gap having a height of 150 μm or more in the thickness direction of the cover protector is provided between the inorganic fiber sheet and the heat insulating material.

[0022] The above object of the present invention is also achieved by the following configuration

[13] relating to a battery module.

[0023]

[13] A battery module comprising: the cover protector according to any one of [1] to

[12] ; a storage battery; and a battery case that houses the cover protector and the storage battery.

[0024] A preferred embodiment of the present invention relating to a battery module relates to the following

[14] .

[0025]

[14] The battery module according to

[13] , characterized in that the battery case has a ceiling surface, side wall surfaces, and bottom wall surfaces therein, the heat insulating material is arranged to face at least one selected from the ceiling surface, the side wall surfaces, and the bottom wall surfaces, and the cover protector is attached inside the battery case.

[0026] According to the present invention, an adhesive having predetermined properties is used as the adhesive for bonding the inorganic fiber sheet and the insulating material, so that the multi-layer structure does not peel off and excellent adhesive performance can be maintained even when exposed to high heat or flames from a battery cell that has experienced thermal runaway.This makes it possible to provide a cover protector that has the effect of protecting the insulating material from flying debris and can maintain excellent insulating performance.

[0027] Furthermore, since the battery module of the present invention is equipped with a cover protector having the above-mentioned excellent adhesive and heat insulating properties, it is possible to suppress damage caused by flying debris during thermal runaway, and even if a fire does occur, it is possible to more reliably prevent the fire from spreading to the outside.

[0028] FIG. 1 is a schematic cross-sectional view showing a cover protector according to an embodiment of the present invention. FIG. 2A is a photograph showing a cross-section of a cover protector according to an embodiment of the present invention. FIG. 2B is a photograph showing an enlarged cross-section of the cover protector in a region different from that shown in FIG. 2A. FIG. 3A shows the cover protector according to this embodiment when the basis weight is 15 (g / m ２ 3B is a photograph showing the state of arrangement of the adhesive material before bonding and the coverage rate of the adhesive after bonding when the basis weight is 20 (g / m) for the cover protector according to this embodiment. ２3C is a photograph showing the state of arrangement of the adhesive material before bonding and the coverage rate of the adhesive after bonding when the basis weight is 25 (g / m) for the cover protector according to this embodiment. ２ 4 is a schematic cross-sectional view showing a battery module according to an embodiment of the present invention, in which the adhesive material is disposed before bonding and the adhesive coverage after bonding when the adhesive material is disposed in the battery module.

[0029] The inventors of the present application conducted extensive research to solve the problem that when the cover protector is exposed to high heat during thermal runaway of the battery cell, the adhesive portion peels off, reducing the protective and insulating performance of the thermal insulator. As a result, they found that appropriately selecting an adhesive to bond the thermal insulator and the inorganic fiber sheet is effective in solving the problem.

[0030] 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.

[0031] [Cover Protector] Fig. 1 is a schematic cross-sectional view showing a cover protector according to an embodiment of the present invention. Fig. 2A is a photograph showing a cross-section of the cover protector according to an embodiment of the present invention, and Fig. 2B is a photograph showing an enlarged cross-section of the cover protector in a region different from that shown in Fig. 2A. As shown in Figs. 1, 2A, and 2B, the cover protector 1 has a heat insulating material 2 containing, for example, inorganic particles 8 or inorganic fibers 6, and an inorganic fiber sheet 3. The inorganic fiber sheet 3 is formed into a sheet shape by weaving together weft threads 3a and warp threads 3b made of inorganic fibers.

[0032] The thermal insulation material 2 and the inorganic fiber sheet 3 are bonded with an adhesive 4, and a joint 5 is formed between the thermal insulation material 2 and the inorganic fiber sheet 3. The joint 5 contains the adhesive 4 and a portion of the inorganic particles 8 contained in the thermal insulation material 2. While it is difficult to substantially see the adhesive in FIGS. 2A and 2B , as shown in FIG. 2B , a region (joint 5) where the inorganic particles 8, which are the material of the thermal insulation material 2, and, for example, the weft threads 3 a of the inorganic fiber sheet 3 coexist can be seen. It can also be seen at the joint 5 that the fibers (weft threads 3 a) of the inorganic fiber sheet 3 penetrate into the thermal insulation material 2. By having the above-described joint 5, the cover protector 1 can maintain high adhesive performance even if the cover protector 1 is exposed to a flame and the adhesive is lost due to high heat.

[0033] The inorganic fiber sheet 3 also has recesses 9 and protrusions 10 on at least the surface facing the thermal insulation material 2. The recesses 9 are located at the boundaries between the weft threads 3a and the warp threads 3b in a plan view of the inorganic fiber sheet 3. In this embodiment, at least one of the thermal insulation material (e.g., inorganic particles 8, inorganic fibers 6, etc.) and the adhesive 4 that constitute the thermal insulation material 2 is present at least partially inside the recesses 9. Note that, for convenience, FIG. 1 shows the inorganic particles 8 only at the joints 5, but in reality, the inorganic particles 8 and the inorganic fibers 6 are contained throughout the entire interior of the thermal insulation material 2.

[0034] Furthermore, in this embodiment, a gap 7 is formed between the heat insulating material 2 and the inorganic fiber sheet 3. The gap 7 will be described later.

[0035] The cover protector 1 according to this embodiment configured as described above has the structure described above, so that the heat insulating material 2 and the inorganic fiber sheet 3 are firmly bonded together. The cover protector 1 can be obtained by controlling the oxygen index and the viscosity of the adhesive material. The oxygen index and the viscosity of the adhesive material of the cover protector according to this embodiment will be described below.

[0036] <Oxygen Index: Greater than 24.7%> In this embodiment, the oxygen index measured for the cover protector 1 is specified. The oxygen index can be measured in accordance with JIS K 7201-2:2021 and is a value that indicates the sensitivity of a material's combustion characteristics. If the oxygen index of the cover protector is 24.7% or less, the cover protector is prone to combustion and the effect of protecting the insulating material and the insulating effect cannot be sufficiently maintained. Therefore, the oxygen index of the cover protector is greater than 24.7% (i.e., greater than 24.7%), preferably 25.0% or more, more preferably 25.5% or more, and even more preferably 26.0% or more. Note that the higher the oxygen index, the higher the flame retardancy. Therefore, the upper limit of the oxygen index is not particularly limited, but considering the configuration of the cover protector in this embodiment, it can be substantially set to 40% or less.

[0037] The measurement conditions for the oxygen index in this embodiment were as follows: Sample shape: 90 mm x 10 mm (Type III) Sample conditioning (pre-treatment): 23°C ± 2°C, 50% RH ± 5% x 88 hours Measurement device: Candle combustion tester AC3 (manufactured by Toyo Seiki Seisakusho, Ltd.) Measurement conditions: Method A (top end ignition), oxygen concentration increase / decrease: 0.2%

[0038] <Viscosity of adhesive material at 250°C: 40 Pa·s or more> By controlling the viscosity of the adhesive material constituting the adhesive 4, the adhesive 4 remains in the recesses 9 of the inorganic fiber sheet 3, and the surface of the inorganic fiber sheet 3 becomes more planar, thereby increasing the adhesive strength between the inorganic fiber sheet 3 and the thermal insulating material 2. Furthermore, by using a high-viscosity adhesive material, the adhesive 4 is retained over the entire surface of the inorganic fiber sheet 3, thereby increasing the coverage rate of the adhesive 4 (the ratio of the area covered by the adhesive 4 to the total area of ​​the area of ​​the surface of the inorganic fiber sheet 3 facing the thermal insulating material 2). Furthermore, during thermal runaway of the battery cell, the area of ​​the cover protector that is directly exposed to the flame may reach, for example, 1000°C or higher and burn. However, the area surrounding the area directly exposed to the flame may reach, for example, approximately 250°C. Therefore, by using a high-viscosity adhesive material, adhesive strength can be maintained and the inorganic fiber sheet 3 may be prevented from peeling off and falling off the thermal insulating material 2.

[0039] If the viscosity of the adhesive material constituting the adhesive 4 at 250°C is less than 40 Pa·s, the effect of increasing the coverage of the adhesive 4 cannot be sufficiently obtained, resulting in a decrease in adhesive strength and making it difficult to prevent the inorganic fiber sheet 3 from falling during thermal runaway. Therefore, the viscosity of the adhesive material at 250°C is 40 Pa·s or more, preferably 55 Pa·s or more, and more preferably 70 Pa·s or more. There is no particular upper limit to the viscosity of the adhesive material at 250°C, but even if the viscosity exceeds 300 Pa·s, the effect of maintaining the coverage and adhesive strength saturates. Therefore, the viscosity of the adhesive material at 250°C is preferably 300 Pa·s or less.

[0040] The cover protector according to this embodiment is formed by bonding the heat insulating material 2 and the inorganic fiber sheet 3 with an adhesive material having a viscosity of 40 Pa·s or more at 250°C. The viscosity of the adhesive material can be measured using, for example, a melt viscoelasticity measuring device (AREA-G2) manufactured by TA Instruments Japan Co., Ltd. The measurement conditions for the viscosity of the adhesive material in this embodiment are as follows: Measurement method: Dynamic measurement Geometry: Parallel plates with a diameter of 25 mm Heating rate: 3°C / min Temperature range: 140°C to 320°C Frequency: 1 Hz Measurement interval: 20 s (every 1°C) Measurement atmosphere: Nitrogen gas flow

[0041] <Adhesive Coverage: 0.50 or More> Figures 3A to 3C are photographs showing the placement of the adhesive material before bonding and the adhesive coverage after bonding for the cover protector according to this embodiment. In the left images of Figures 3A to 3C, the white fibrous objects are adhesive material 11 placed on the surface of inorganic fiber sheet 3. In the right images, the dark black areas represent adhesive 4 melted on the surface of inorganic fiber sheet 3. The right images are used to measure the coverage of adhesive 4, and show the state after adhesive material 11 is placed on the surface of inorganic fiber sheet 3, release paper is then placed, and the sheet is bonded under actual bonding conditions, after which the release paper is peeled off. The coverage can be calculated by measuring the overall area and the area of ​​the dark black areas in the right images.

[0042] In this embodiment, the viscosity of the adhesive material at 250°C is specified. As a result, as shown in Figures 3A to 3C, the adhesive 4 not only remains in the recesses 9 of the inorganic fiber sheet 3 but also remains on the entire surface of the inorganic fiber sheet 3, thereby improving the coverage of the adhesive 4. When the coverage of the adhesive 4 is 0.50 or more, the required adhesive strength between the inorganic fiber sheet 3 and the thermal insulating material 2 can be sufficiently ensured. Therefore, the coverage of the adhesive 4 is preferably 0.50 or more, more preferably 0.76 or more, and even more preferably 0.88 or more. There is no particular upper limit to the coverage of the adhesive 4. A higher coverage can improve the adhesive strength between the inorganic fiber sheet 3 and the thermal insulating material 2, but the amount of adhesive material required increases, so the coverage may be 0.98 or less.

[0043] <Ratio of coverage to adhesive basis weight: 2.7 × 10 －２ (m ２ / g) or more> The basis weight of the adhesive 4 is the mass (g / m) of the adhesive material 11 placed per unit area of ​​the inorganic fiber sheet 3. ２ ) In other words, the larger the ratio of the coverage rate to the basis weight, the larger the coverage rate can be secured with a smaller amount of adhesive material. The ratio of the coverage rate to the basis weight will be further explained using Figures 3A to 3C.

[0044] FIG. 3A shows a fabric with a basis weight of 15 (g / m ２ ), and FIG. 3B shows an example where the basis weight is 20 (g / m ２ ), and FIG. 3C shows an example where the basis weight is 25 (g / m ２ At least, the basis weight is 15 (g / m ２ ) to 25 (g / m ２ 3A to 3C, in the cover protector of this embodiment, the ratio of the coverage rate to the adhesive basis weight is approximately 3.3×10 －２ (m ２ / g) to 3.80 × 10 －２ (m ２ / g).

[0045] In contrast, in the case of a cover protector manufactured under the same conditions as those shown in FIGS. 3A to 3C using an adhesive material with a viscosity of less than 40 Pa·s at 250°C, the basis weight was 30 (g / m ２ ), the coverage rate is only 0.77, and the ratio of the coverage rate to the basis weight is about 2.57 × 10 －２ (m ２ / g).

[0046] The ratio of the coverage rate to the adhesive weight is 2.7 x 10 －２ (m ２ / g) or more, a large coverage can be ensured with a small amount of adhesive material, which is preferable. －２ (m ２ / g) or more, and more preferably 3.3 × 10 －２ (m ２ As described above, the ratio of the coverage rate to the basis weight of the adhesive is greatly affected by the viscosity of the adhesive material, and therefore, in this embodiment, it is extremely important that the viscosity of the adhesive material at 250°C is 40 Pa s or more.

[0047] <Void Portion> As shown in Figures 1, 2A, and 2B, the cover protector 1 has a void portion 7 between the insulating material 2 and the inorganic fiber sheet 3. The void portion 7 is often formed near the recess 9 at the boundary between the weft yarns 3a and the warp yarns 3b of the inorganic fiber sheet 3, but its location is not particularly limited. The void portion 7 can be of various sizes. For example, the presence of a void portion 7 of a predetermined size or larger can further improve the insulating performance during normal use at relatively low temperatures compared to when the insulating material 2 and the inorganic fiber sheet 3 are tightly adhered to each other without any gaps. To achieve the effect of improving the insulating performance of the cover protector, the cover protector preferably has a void portion 7 with a height in the thickness direction of 150 μm or more, and more preferably a void portion 7 with a height in the thickness direction of 250 μm or more. Note that if the void portion 7 is too high, it may cause a decrease in the strength and adhesive force of the cover protector. Therefore, the height of the void portion 7 in the thickness direction of the cover protector is preferably 350 μm or less.

[0048] The heat insulating material 2, the inorganic fiber sheet 3, and the adhesive material 11 that constitutes the adhesive 4 that constitute the cover protector 1 according to this embodiment will be described in detail below.

[0049] [Insulating Material] The insulating material 2 used in the cover protector according to this embodiment is not particularly limited as long as it has an insulating effect. Thermal conductivity can be used as an index of insulating effect. In this embodiment, the thermal conductivity of the insulating material 2 is preferably less than 1 (W / m·K), more preferably less than 0.5 (W / m·K), and even more preferably less than 0.2 (W / m·K). Furthermore, the thermal conductivity of the insulating material 2 is more preferably less than 0.1 (W / m·K), more preferably less than 0.05 (W / m·K), and particularly preferably less than 0.02 (W / m·K). The thermal conductivity of the insulating material 2 can be measured in accordance with JIS R 2251, "Test Method for Thermal Conductivity of Refractories."

[0050] The heat insulating material 2 preferably contains inorganic particles 8, and also preferably contains, as other components, at least one selected from inorganic fibers, organic fibers, and organic particles. Specific examples of each are shown below.

[0051] <Inorganic particles> As the inorganic particles, a single inorganic particle may be used, or two or more types of inorganic particles may be used in combination.As the type of inorganic particles, from the viewpoint of heat insulating effect, it is preferable to use particles made of at least one inorganic material selected from oxide particles, carbide particles, nitride particles and inorganic hydrate particles, and it is more preferable to use oxide particles.In addition, the shape is not particularly limited, but it is preferable to include at least one selected from nanoparticles, hollow particles and porous particles.Specifically, it is also possible to use inorganic balloons such as silica nanoparticles, metal oxide particles, microporous particles and hollow silica particles, particles made of thermally expandable inorganic materials, particles made of hydrous porous bodies, etc.

[0052] When the average secondary particle diameter of the inorganic particles is 0.01 μm or more, they are easily available and the increase in production costs can be suppressed. When the average secondary particle diameter is 200 μm or less, the desired heat insulating effect can be obtained. Therefore, the average secondary particle diameter of the inorganic particles is preferably 0.01 μm or more and 200 μm or less, and more preferably 0.05 μm or more and 100 μm or less.

[0053] In addition, when two or more inorganic particles with different heat insulating effects are used in combination, the heat generating body can be cooled in multiple stages, and the heat absorption effect can be exerted over a wider temperature range. Specifically, it is preferable to use a mixture of large-diameter particles and small-diameter particles. For example, when nanoparticles are used as one of the inorganic particles, it is preferable to include inorganic particles made of a metal oxide as the other inorganic particle. Hereinafter, the inorganic particles will be described in more detail, with the small-diameter inorganic particles being referred to as the first inorganic particles and the large-diameter inorganic particles being referred to as the second inorganic particles.

[0054] <First Inorganic Particles> (Oxide Particles) When oxide particles are used as the first inorganic particles, radiant heat transfer can be suppressed, particularly in high-temperature regions such as abnormal heat generation. As the oxide particles, at least one type of particle selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina can be used. That is, among the above oxide particles that can be used as inorganic particles, only one type may be used, or two or more types of oxide particles may be used. In particular, silica is a component with high heat insulating properties, and titania is a component with a higher refractive index than other metal oxides, and is highly effective in scattering light and blocking radiant heat in high-temperature regions of 500°C or higher. Therefore, it is most preferable to use silica and titania as the oxide particles.

[0055] Since oxide particles have a high refractive index and a strong effect of diffusely reflecting light, the particle size of the oxide particles may affect the effect of reflecting radiant heat. Therefore, by limiting the average primary particle size of the oxide particles to a predetermined range, even higher thermal insulation properties can be obtained.

[0056] (Average primary particle diameter of oxide particles: 0.001 μm or more and 50 μm or less) When the average primary particle diameter of the oxide particles is 0.001 μm or more, the oxide particles are sufficiently larger than the wavelength of light that contributes to heating and efficiently diffusely reflect light, thereby suppressing radiative heat transfer within the cover protector in high-temperature ranges of 500° C. or more and further improving heat insulation. On the other hand, when the average primary particle diameter of the oxide particles is 50 μm or less, the number and contact points between particles do not increase even when compressed, making it difficult to form paths for conductive heat transfer, thereby reducing the impact on heat insulation, particularly in normal temperature ranges where conductive heat transfer is dominant.

[0057] In the present invention, the average primary particle size can be determined by observing particles under a microscope, comparing with a standard scale, and taking the average of any 10 particles.

[0058] (Nanoparticles) In the present invention, nanoparticles refer to particles on the nanometer order that are spherical or nearly spherical and have an average primary particle diameter of less than 1 μm. Nanoparticles have a low density, which suppresses conductive heat transfer. When nanoparticles are used as the first inorganic particles, the fine voids are dispersed, resulting in excellent thermal insulation that suppresses convective heat transfer. Therefore, nanoparticles are preferred because they can suppress heat conduction between adjacent nanoparticles during normal battery operation at room temperature. Furthermore, when nanoparticles with a small average primary particle diameter are used as oxide particles, an increase in conductive heat transfer through the insulating material can be suppressed even when the insulating material is compressed due to expansion caused by thermal runaway in the battery cell, increasing its internal density. This is thought to be because nanoparticles are prone to forming fine voids between particles due to electrostatic repulsion, and their low bulk density allows the particles to be packed together to provide cushioning.

[0059] When nanoparticles are used as the first inorganic particles, there are no particular limitations on the material as long as they comply with the definition of nanoparticles. For example, silica nanoparticles are a material with high heat insulating properties, and the contact points between particles are small, so the amount of heat conducted by silica nanoparticles is smaller than when silica particles with a large particle diameter are used. Furthermore, commonly available silica nanoparticles have a bulk density of 0.1 (g / cm３ ), for example, even if a large compressive stress is applied to the heat insulating material, the size (area) and number of contact points between silica nanoparticles do not increase significantly, and heat insulating properties can be maintained. Therefore, it is preferable to use silica nanoparticles as the nanoparticles. Examples of silica nanoparticles include wet silica, dry silica, and aerogel, but silica nanoparticles that are particularly suitable for this embodiment will be described below.

[0060] (Average primary particle diameter of nanoparticles: 1 nm or more and 100 nm or less) Limiting the average primary particle diameter of nanoparticles to a predetermined range can achieve even higher thermal insulation. That is, when the average primary particle diameter of nanoparticles is 1 nm or more and 100 nm or less, convective heat transfer and conductive heat transfer within the thermal insulation material can be suppressed, particularly in the temperature range below 500°C, thereby further improving the thermal insulation. Furthermore, even when compressive stress is applied, the voids remaining between the nanoparticles and the contact points between many particles suppress conductive heat transfer, thereby maintaining the thermal insulation properties of the thermal insulation material. The average primary particle diameter of nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. On the other hand, the average primary particle diameter of nanoparticles is more preferably 50 nm or less, and even more preferably 10 nm or less.

[0061] (Inorganic hydrate particles) When inorganic hydrate particles receive heat from a heating element and reach a temperature above the thermal decomposition initiation temperature, they undergo thermal decomposition, releasing their own water of crystallization to lower the temperature of the heating element and its surroundings, thereby exhibiting the so-called "endothermic effect." After releasing the water of crystallization, they become porous, and exhibit heat insulating properties due to the countless air holes. Specific examples of inorganic hydrates include aluminum hydroxide (Al(OH) ３ ), magnesium hydroxide (Mg(OH) ２ ), calcium hydroxide (Ca(OH) ２ ), zinc hydroxide (Zn(OH) ２ ), iron hydroxide (Fe(OH) ２ ), manganese hydroxide (Mn(OH) ２ ), zirconium hydroxide (Zr(OH) ２ ), gallium hydroxide (Ga(OH)３ ) etc.

[0062] For example, aluminum hydroxide contains about 35% water of crystallization, and as shown in the following formula, it thermally decomposes, releasing the water of crystallization and exhibiting an endothermic effect. After releasing the water of crystallization, it becomes a porous alumina (Al ２ O ３ ) and functions as a heat insulating material. 2Al(OH) ３ →Al ２ O ３ +3H ２ O

[0063] In a battery cell that has experienced thermal runaway, the temperature rises sharply to over 200° C. and continues to rise to around 700° C. Therefore, the inorganic particles contained in the thermal insulating material 2 are preferably made of inorganic hydrates whose thermal decomposition temperature begins at 200° C. or higher.

[0064] The thermal decomposition starting temperatures of the inorganic hydrates listed above are approximately 200°C for aluminum hydroxide, approximately 330°C for magnesium hydroxide, approximately 580°C for calcium hydroxide, approximately 200°C for zinc hydroxide, approximately 350°C for iron hydroxide, approximately 300°C for manganese hydroxide, approximately 300°C for zirconium hydroxide, and approximately 300°C for gallium hydroxide. All of these temperatures roughly overlap with the temperature range in which a battery cell experiencing thermal runaway experiences a sudden rise in temperature, and can efficiently suppress the temperature rise, making these inorganic hydrates preferable.

[0065] (Average secondary particle diameter of inorganic hydrate particles: 0.01 μm or more and 200 μm or less) Furthermore, when inorganic hydrate particles are used as the first inorganic particles, if the average particle diameter is too large, it takes a certain amount of time for the first inorganic particles (inorganic hydrate) near the center of the thermal insulation material 2 to reach their thermal decomposition temperature, and therefore the first inorganic particles near the center of the thermal insulation material 2 may not be completely thermally decomposed. For this reason, the average secondary particle diameter of the inorganic hydrate particles is preferably 0.01 μm or more and 200 μm or less, and more preferably 0.05 μm or more and 100 μm or less.

[0066] (Particles Made of Thermally Expandable Inorganic Material) Examples of thermally expandable inorganic materials include vermiculite, bentonite, mica, and perlite.

[0067] (Particles Made of Hydrous Porous Material) Specific examples of hydrous porous materials include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

[0068] (Inorganic Balloons) The thermal insulating material 2 used in the present invention may contain inorganic balloons as the first inorganic particles. When inorganic balloons are contained, convective heat transfer or conductive heat transfer within the thermal insulating material 2 can be suppressed in a temperature range of less than 500°C, thereby further improving the thermal insulation properties of the thermal insulating material 2. As the inorganic balloons, at least one type selected from shirasu balloons, silica balloons, fly ash balloons, barite balloons, and glass balloons can be used.

[0069] (Content of inorganic balloons: 60 mass % or less based on the total mass of the heat insulating material) The content of inorganic balloons is preferably 60 mass % or less based on the total mass of the heat insulating material.

[0070] (Average Particle Diameter of Inorganic Balloons: 1 μm or More and 100 μm or Less) The average particle diameter of the inorganic balloons is preferably 1 μm or more and 100 μm or less.

[0071] <Second inorganic particles> When two types of inorganic particles are contained in the thermal insulating material 2, the second inorganic particles are not particularly limited as long as they are different from the first inorganic particles in terms of material, particle size, etc. Examples of the second inorganic particles that can be used include oxide particles, carbide particles, nitride particles, inorganic hydrate particles, silica nanoparticles, metal oxide particles, inorganic balloons such as microporous particles and hollow silica particles, particles made of a thermally expandable inorganic material, and particles made of a hydrous porous body, the details of which are as described above.

[0072] Nanoparticles have extremely low conductive heat transfer and can maintain excellent heat insulation even when compressive stress is applied to the heat insulating material. Metal oxide particles such as titania have a high effect of blocking radiant heat. Furthermore, when large-diameter inorganic particles and small-diameter inorganic particles are used, the small-diameter inorganic particles penetrate into the gaps between the large-diameter inorganic particles, resulting in a denser structure and improved heat insulating properties. Therefore, when nanoparticles are used as the first inorganic particles, it is preferable to further include metal oxide particles larger in diameter than the first inorganic particles as the second inorganic particles in the heat insulating material.

[0073] Examples of metal oxides include silicon oxide, titanium oxide, aluminum oxide, barium titanate, zinc oxide, zircon, zirconium oxide, etc. In particular, titanium oxide (titania) is a component with a higher refractive index than other metal oxides, and is highly effective in scattering light and blocking radiant heat in a high temperature range of 500°C or higher, so titania is most preferably used.

[0074] When at least one type of particle selected from silica nanoparticles and silica aerogel is used as the first inorganic particles, and at least one type of particle selected from titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina is used as the second inorganic particles, in order to obtain excellent heat insulating performance within a temperature range of 90 ° C. or less, the first inorganic particles are preferably 50 mass % or more, more preferably 60 mass % or more, and even more preferably 70 mass % or more, based on the total mass of the inorganic particles. Furthermore, the first inorganic particles are preferably 95 mass % or less, more preferably 90 mass % or less, and even more preferably 80 mass % or less, based on the total mass of the inorganic particles.

[0075] On the other hand, in order to obtain excellent heat insulating performance within a temperature range exceeding 90° C., the content of the second inorganic particles is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more, based on the total mass of the inorganic particles. Furthermore, the content of the second inorganic particles is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, based on the total mass of the inorganic particles.

[0076] (Average primary particle diameter of second inorganic particles) When second inorganic particles made of a metal oxide are contained in a thermal insulating material, if the average primary particle diameter of the second inorganic particles is 1 μm or more and 50 μm or less, radiation heat transfer can be efficiently suppressed in a high temperature range of 500° C. or more. The average primary particle diameter of the second inorganic particles is more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

[0077] (Inorganic Particle Content) In this embodiment, if the total content of inorganic particles in the thermal insulation material 2 is appropriately controlled, the thermal insulation properties of the thermal insulation material 2 can be sufficiently ensured. The total content of inorganic particles is preferably 60% by mass or more, and more preferably 70% by mass or more, relative to the total mass of the thermal insulation material. Furthermore, if the total content of inorganic particles becomes too high, the content of organic fibers will relatively decrease. Therefore, in order to sufficiently obtain the skeleton reinforcing effect and the inorganic particle retention effect, the total content of inorganic particles is preferably 95% by mass or less, and more preferably 90% by mass or less, relative to the total mass of the thermal insulation material.

[0078] The content of inorganic particles in the heat insulating material can be calculated, for example, by heating the heat insulating material at 800° C., decomposing the organic components, and then measuring the mass of the remaining portion.

[0079] <Inorganic Fibers> As the inorganic fibers, a single inorganic fiber may be used, or two or more inorganic fibers may be used in combination. Examples of inorganic fibers include ceramic fibers such as silica fiber, alumina fiber, alumina silicate fiber, zirconia fiber, carbon fiber, soluble fiber, refractory ceramic fiber, aerogel composite, magnesium silicate fiber, alkaline earth silicate fiber, potassium titanate fiber, silicon carbide fiber, and potassium titanate whisker fiber; glass fibers such as glass fiber, glass wool, and slag wool; and natural mineral fibers other than these fibers, such as rock wool, basalt fiber, wollastonite, and mullite fiber. These inorganic fibers are preferred in terms of heat resistance, strength, and availability. Among the inorganic fibers, from the viewpoint of handleability, at least one selected from silica-alumina fiber, alumina fiber, silica fiber, rock wool, alkaline earth silicate fiber, and glass fiber is particularly preferred.

[0080] The cross-sectional shape of the inorganic fiber is not particularly limited, and examples thereof include a circular cross section, a flat cross section, a hollow cross section, a polygonal cross section, a core cross section, etc. Among these, modified cross section fibers having a hollow cross section, a flat cross section, or a polygonal cross section are preferably used because they have slightly improved heat insulation properties.

[0081] (Average fiber length of inorganic fibers) The preferred lower limit of the average fiber length of inorganic fibers is 0.1 mm, more preferably 0.5 mm. On the other hand, the preferred upper limit of the average fiber length of inorganic fibers is 50 mm, more preferably 10 mm. If the average fiber length of inorganic fibers is less than 0.1 mm, the inorganic fibers are less likely to be entangled with each other, which may reduce the mechanical strength of the insulating material. On the other hand, if the average fiber length exceeds 50 mm, although a reinforcing effect can be obtained, the inorganic fibers may not be able to be tightly entangled with each other, or may be curled up by a single inorganic fiber, which may result in a reduction in insulating properties.

[0082] The preferred lower limit of the average fiber diameter of the inorganic fibers is 1 μm, more preferably 2 μm, and even more preferably 3 μm. On the other hand, the preferred upper limit of the average fiber diameter of the inorganic fibers is 15 μm, and more preferably 10 μm. If the average fiber diameter of the inorganic fibers is less than 1 μm, the mechanical strength of the inorganic fibers themselves may be reduced. Furthermore, from the viewpoint of the effects on human health, the average fiber diameter of the inorganic fibers is preferably 3 μm or more. On the other hand, if the average fiber diameter of the inorganic fibers is greater than 15 μm, solid heat transfer through the inorganic fibers may increase, leading to a decrease in thermal insulation properties, and the moldability and strength of the thermal insulation material may be deteriorated.

[0083] (Inorganic Fiber Content) In the present embodiment, when the thermal insulating material 2 contains inorganic fibers, the content of the inorganic fibers is preferably 3 mass % or more and 15 mass % or less with respect to the total mass of the thermal insulating material.

[0084] Furthermore, the content of inorganic fibers is more preferably 5% by mass or more and 10% by mass or less of the total mass of the thermal insulation material. By setting the content in this range, the shape retention, pressing force resistance, wind pressure resistance, and inorganic particle retention ability of the inorganic fibers are exhibited in a balanced manner. Furthermore, by appropriately controlling the content of inorganic fibers, the organic fibers and inorganic fibers are entangled with each other to form a three-dimensional network, which further improves the effect of retaining inorganic particles and other compounding materials described below.

[0085] <Organic Fibers> Organic fibers have the effect of imparting flexibility to the insulating material, and by forming a skeleton, they have the effect of increasing the strength of the insulating material. Furthermore, if inorganic particles and other organic fibers are fused to the surface of the organic fibers, the effect of improving the strength of the insulating material and the effect of maintaining its shape can be further improved. Furthermore, if the insulating material contains organic fibers in an appropriate content, multiple voids are formed inside the insulating material, and when the insulating material is heated, air and moisture can be released to the outside through the voids.

[0086] As the organic fiber material for the insulation material 2, in addition to single-component organic fibers such as cellulose fiber, polyvinyl alcohol (PVA) fiber, polyethylene fiber, nylon fiber, polyurethane fiber, ethylene-vinyl alcohol copolymer fiber, etc. can be used.

[0087] When the heat insulating material is manufactured by a papermaking method, it is difficult to raise the heating temperature above 250°C. Therefore, the glass transition point of the organic fiber is preferably 250°C or lower, and more preferably 200°C or lower.

[0088] Although the lower limit of the glass transition point of the organic fiber is not particularly limited, when a resin binder is used, if the difference between the glass transition point of the organic fiber and the glass transition point of the resin binder is 10°C or more, the resin binder will solidify after the organic fiber, which was in a semi-molten state, has completely solidified in the cooling step during production, and therefore the skeleton reinforcing effect of the resin binder can be sufficiently obtained. Therefore, the difference between the glass transition point of the resin binder and the glass transition point of the organic fiber is preferably 10°C or more, and more preferably 30°C or more.

[0089] On the other hand, if the difference in glass transition point between the two is 130°C or less, the time from when the organic fibers completely solidify until the resin binder starts to solidify can be appropriately adjusted, and the resin binder solidifies while remaining in a well-dispersed state, thereby achieving an even greater reinforcement effect for the skeleton. Therefore, the difference between the glass transition point of the resin binder and the glass transition point of the organic fibers is preferably 130°C or less, more preferably 120°C or less, even more preferably 100°C or less, even more preferably 80°C or less, and particularly preferably 70°C or less.

[0090] The organic fibers may also be binder fibers with a sheath-core structure. The binder fibers have a core extending in the longitudinal direction of the fiber and a sheath formed to cover the outer surface of the core. In this case, the core is made of a first organic material, and the sheath is made of a second organic material, and the melting point of the first organic material is higher than that of the second organic material.

[0091] (First Organic Material) In the present embodiment, when a binder fiber having a core-sheath structure is used, the first organic material constituting the core is not particularly limited as long as it has a melting point higher than that of the sheath present on the outer surface of the core, i.e., the second organic material. Examples of the first organic material include at least one selected from polyethylene terephthalate, polypropylene, and nylon.

[0092] (Second Organic Material) The second organic material is not particularly limited as long as it has a melting point lower than that of the first organic material constituting the organic fiber. Examples of the second organic material include at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon. The melting point of the second organic material is preferably 90°C or higher, more preferably 100°C or higher. The melting point of the second organic material is preferably 150°C or lower, more preferably 130°C or lower.

[0093] (Organic fiber content) When the organic fiber content in the thermal insulation material 2 is appropriately controlled, a sufficient skeleton reinforcing effect can be obtained. The organic fiber content is preferably 5 mass% or more, and more preferably 10 mass% or more, relative to the total mass of the thermal insulation material. Furthermore, if the organic fiber content is too high, the inorganic particle content will relatively decrease. Therefore, in order to obtain the desired thermal insulation performance, the organic fiber content is preferably 25 mass% or less, and more preferably 20 mass% or less, relative to the total mass of the thermal insulation material.

[0094] (Fiber length of organic fibers) The fiber length of the organic fibers is not particularly limited, but from the viewpoint of ensuring moldability and processability, the average fiber length of the organic fibers is preferably 10 mm or less. On the other hand, from the viewpoint of making the organic fibers function as a skeleton and ensuring the compressive strength of the thermal insulating material, the average fiber length of the organic fibers is preferably 0.5 mm or more.

[0095] (Infusible Fiber) The heat insulating material 2 may contain infusible fiber as the fiber. Examples of the infusible fiber include fibers obtained by infusibility treatment of thermoplastic resins such as polyacrylonitrile, cellulose, and pitch. The infusible fiber is, for example, a fiber that has been infusible treated, and examples of the infusible treatment include a method of crosslinking by irradiation with radiation or an electron beam, and a method of exposing the fiber to high temperatures in oxygen or water vapor to make it infusible by the action of oxygen.

[0096] (Carbon Content) The infusible fiber preferably has a carbon content of 55 to 95% by mass. When the carbon content is 55% by mass or more, weight loss due to thermal decomposition has already progressed, so shrinkage due to thermal decomposition is small, and even if directly exposed to flames during thermal runaway, the fiber retains its original shape and maintains its thermal insulation properties. When the carbon content is 95% by mass or less, components other than carbon are eliminated and the fiber changes to a structure consisting only of carbon, causing an endothermic reaction, which can delay the time it takes for heat to reach the back surface of the flame-retardant structure.

[0097] The lower limit of the carbon content is preferably 60% by mass or more, and the upper limit of the carbon content is preferably 90% by mass or less, and more preferably 85% by mass or less.

[0098] The carbon content can be adjusted by heat treatment. For example, heat treatment in air or oxygen at a temperature in the range of 150 to 300°C can further promote infusibility and remove components other than carbon, thereby increasing the carbon content. For example, heat treatment at a temperature in the range of 300 to 1000°C can promote the formation of condensed polycyclic aromatic structures and generate decomposition gases, thereby increasing the carbon content.

[0099] The infusible fibers are not limited to fibers that have been infusible from thermoplastic fibers, and may be inorganic fibers as long as they have a carbon content within the above range.

[0100] (Fiber Shape) The infusible fibers are preferably short fibers. Short fibers mean that they are not continuous fibers. Continuous fibers, like cloth or filament winding, form fiber bundles with the fibers oriented in the same direction, whereas short fibers form aggregates (mats, blankets, and paper products) with the fibers oriented in random directions. Furthermore, insulation materials using short fibers have short conductive paths, so they can have low conductivity even when carbonization of fibers progresses or when carbonization progresses due to thermal runaway. Furthermore, the random orientation of the fibers makes them more likely to form point contacts with each other, thereby reducing thermal conductivity.

[0101] When manufacturing a thermal insulation material containing infusible fibers, it is preferable to use milled or chopped infusible fibers (fiber length of about 0.01 to 10 mm). The infusible fibers preferably have a fiber diameter of 1 to 30 μm. When the fiber diameter of the infusible fibers is 1 μm or more, the rate of air oxidation and sublimation can be suppressed even when exposed to high temperatures, and the flame-retardant effect can be maintained for a long period of time. On the other hand, when the fiber diameter of the infusible fibers is 30 μm or less, a certain degree of flexibility can be maintained even when exposed to high temperatures and carbonized, making them less susceptible to breakage even when deformed or impacted.

[0102] <Organic Particles> As the organic particles, hollow polystyrene particles or the like can be used.

[0103] <Other Compounding Materials> (Resin Binder) The material of the heat insulating material 2 in this embodiment can also be bound by a resin binder. There are no particular limitations on the resin binder as long as it has a glass transition point lower than the glass transition point of the single-component organic fiber. For example, a resin binder containing at least one selected from styrene-butadiene resin, acrylic resin, silicone-acrylic resin, and styrene resin can be used.

[0104] The glass transition point of the resin binder is not particularly specified, but is preferably -10°C or higher. If the glass transition point of the resin binder is room temperature or higher, the strength of the insulating material can be further improved when the insulating material containing the resin binder is used at room temperature. Therefore, the glass transition point of the resin binder is, for example, more preferably 20°C or higher, even more preferably 30°C or higher, even more preferably 50°C or higher, and particularly preferably 60°C or higher.

[0105] The content of the resin binder is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on the total mass of the heat insulating material, and is preferably 20% by mass or less, more preferably 10% by mass or less.

[0106] (Hot Melt Powder) In addition to the inorganic particles, inorganic fibers, organic fibers, and organic particles, the mixture used to manufacture the insulating material 2 may contain hot melt powder. When using the core-sheath binder fiber, the hot melt powder contains, for example, a third organic material different from the first and second organic materials, and is a powder that melts when heated. When the hot melt powder is added to the material mixture of the insulating material 2 and heated, the hot melt powder melts, and when cooled, it hardens in a state that includes the surrounding inorganic particles. This further prevents the inorganic particles from falling off the insulating material.

[0107] Hot melt powders with various melting points can be used, but a hot melt powder with an appropriate melting point can be selected taking into account the melting points of the core and sheath of the binder fiber used. When a core-sheath binder fiber is used as the organic fiber, if the third organic material constituting the hot melt powder has a melting point lower than that of the first organic material constituting the organic fiber, the heating temperature can be set to melt the sheath and hot melt powder while leaving the core. For example, if the melting point of the hot melt powder is lower than that of the sheath, the heating temperature during production can be set between the melting points of the core and the sheath, making it even easier to set the heating temperature.

[0108] Alternatively, the type of hot melt powder used can be selected so that its melting point lies between the melting points of the core and the sheath. When a hot melt powder with such a melting point is used, the sheath and hot melt powder melt together, and then when they cool and harden, the organic fibers (core), the molten sheath around them, and the hot melt powder present in the gaps between the inorganic particles harden first. As a result, the position of the organic fibers can be fixed, and then the molten sheath is fused to the organic fibers, facilitating the formation of a three-dimensional skeleton. This further improves the strength of the entire insulation.

[0109] If the melting point of the third organic material constituting the hot melt powder is sufficiently lower than that of the first organic material constituting the core, the heating temperature setting margin in the heating step can be expanded, making it easier to set the temperature to obtain the desired structure. For example, the melting point of the first organic material is preferably 60°C or more higher than that of the third organic material, more preferably 70°C or more higher, and even more preferably 80°C or more higher.

[0110] The melting point of the hot melt powder (third organic material) is preferably 80° C. or higher, and more preferably 90° C. or higher. The melting point of the hot melt powder (third organic material) is preferably 180° C. or lower, and more preferably 150° C. or lower. Examples of components constituting the hot melt powder include polyethylene, polyester, polyamide, and ethylene vinyl acetate.

[0111] (Hot melt powder content) When hot melt powder is contained in the material of the insulating material to suppress the shedding of inorganic particles, even a small amount of hot melt powder can be used to suppress powder shedding. Therefore, the content of the hot melt powder is preferably 0.5% by mass or more, more preferably 1% by mass or more, based on the total mass of the materials constituting the insulating material. On the other hand, since the content of inorganic particles and the like decreases relatively when the content of the hot melt powder is increased, in order to obtain the desired insulating performance, the content of the hot melt powder is preferably 5% by mass or less, more preferably 4% by mass or less, based on the total mass of the materials constituting the insulating material.

[0112] When the insulating material contains a hot melt powder, the heating temperature in the heating step is preferably set to be at least 10°C higher, more preferably 20°C higher, than the higher of the melting point of the second organic material constituting the sheath and the melting point of the third organic material constituting the hot melt powder. On the other hand, the heating temperature is preferably set to be at least 10°C lower, more preferably 20°C lower, than the melting point of the first organic material constituting the core. Setting the heating temperature at such a temperature allows a strong skeleton to be formed, further improving the strength of the insulating material and preventing the inorganic particles from falling off.

[0113] The heat insulating material 2 may further contain other binders, colorants, etc. as needed. These are all useful for the purpose of reinforcing the heat insulating material or improving its formability, and the total amount of these additives is preferably 10 mass % or less based on the total mass of the heat insulating material.

[0114] In the present invention, there is no particular limitation on the method for manufacturing the thermal insulation material 2, and commonly used wet and dry methods can be used to manufacture the thermal insulation material 2. As for the materials used in manufacturing, a material suitable for the manufacturing method may be selected from the materials listed above depending on the required properties.

[0115] [Inorganic fiber sheet] The inorganic fiber sheet 3 in this embodiment is formed by processing inorganic fibers into a sheet, and the inorganic fibers used are not particularly limited. For example, the inorganic fibers described in the above-mentioned thermal insulating material 2 can be used. Among them, it is preferable to use inorganic fibers containing at least one type of fiber selected from silica fibers, alumina fibers, glass fibers, and metal fibers because they are inexpensive, easy to handle, and have high heat resistance.

[0116] There are no restrictions on the shape of the inorganic fibers, such as the fiber diameter, but in order to prevent collisions with flying particles during thermal runaway, it is preferable that the mesh size is small.

[0117] (Surface roughness Ra of inorganic fiber sheet: 50 μm or more and 100 μm or less) As described above, the inorganic fiber sheet 3 has recesses 9 and protrusions 10 on at least the surface facing the thermal insulation material 2. By having the recesses 9 and protrusions 10 on the inorganic fiber sheet 3, at least one of the adhesive 4 and the thermal insulation material can easily penetrate into the recesses 9, thereby increasing the adhesive strength between the thermal insulation material 2 and the inorganic fiber sheet 3. In this embodiment, the surface roughness Ra is used as an indicator of the recesses 9 and the protrusions 10.

[0118] If the surface roughness Ra of the inorganic fiber sheet 3 on the insulating material 2 side is 50 μm or more, part of the insulating material 2 and adhesive 4 will penetrate into the recesses 9, creating a spike effect that makes them less likely to peel off, further increasing adhesive strength. Therefore, the surface roughness Ra of the inorganic fiber sheet 3 on the insulating material 2 side is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more. On the other hand, if the surface roughness Ra exceeds 100 μm, penetration will be shallower, resulting in a smaller adhesive area and insufficient adhesive strength. Therefore, the surface roughness Ra of the inorganic fiber sheet 3 on the insulating material 2 side is preferably 100 μm or less, more preferably 90 μm or less, and even more preferably 80 μm or less.

[0119] The surface roughness Ra of the inorganic fiber sheet 3 can be measured using, for example, a shape measuring laser microscope (VK-X210, manufactured by Keyence Corporation).

[0120] [Adhesive Material] The cover protector 1 according to this embodiment is obtained by disposing an adhesive material between the heat insulating material 2 and the inorganic fiber sheet 3, applying heat and pressure, and then cooling to harden the adhesive material. The adhesive material preferably contains a polymer. Furthermore, the polymer contained in the adhesive material preferably includes a polyamide-based organic material, a polyolefin-based material, a rubber-based material, or a silicone-based material.

[0121] (Polyamide-based organic material content in adhesive material: 80% by mass or more) When a polyamide-based organic material is used as the polymer in the adhesive material, the viscosity of the adhesive material is significantly affected by the content of the polyamide-based organic material. When the content of the polyamide-based organic material in the adhesive material is 80% by mass or more, the viscosity of the adhesive material at 250°C is not too low, and the desired adhesive strength can be obtained. Therefore, the content of the polyamide-based organic material in the adhesive material is preferably 80% by mass or more, and more preferably 95% by mass or more, relative to the total mass of the adhesive material. On the other hand, when the content of the polyamide-based organic material in the adhesive material is 99% by mass or less, the viscosity of the adhesive material at 250°C is not too high, and the desired adhesive strength and coverage can be obtained. Therefore, the content of the polyamide-based organic material in the adhesive material is preferably 99% by mass or less, relative to the total mass of the adhesive material.

[0122] [Method of Manufacturing Cover Protector] Next, an example of a method of manufacturing the cover protector according to this embodiment will be briefly described with reference to FIGS. 1, 2A, and 2B, but this embodiment is not limited to the following manufacturing method.

[0123] <Placement Step> First, the adhesive material 11 constituting the adhesive 4 is placed on the inorganic fiber sheet 3. Then, the heat insulating material 2 is placed on the inorganic fiber sheet 3 on which the adhesive material 11 has been placed.

[0124] <Bonding Step> Next, the area where the heat insulating material 2, adhesive material 11, and inorganic fiber sheet 3 are laminated is heated and pressurized. When a polyamide-based organic material is used as the adhesive material 11, the heating temperature can be set to, for example, 200°C, which is higher than the melting point of the polyamide-based organic material, and the pressure can be set to, for example, 100 kPa, but the temperature and pressure are not particularly limited. Thereafter, by cooling, the cover protector 1 in which the heat insulating material 2 and the inorganic fiber sheet 3 are bonded at the joint 5 can be obtained.

[0125] In the above manufacturing method, the viscosity and type of adhesive material used and the surface roughness Ra of the inorganic fiber sheet 3 on the heat insulating material 2 side are as described above.

[0126] According to the above-mentioned method for manufacturing the cover protector, it can be manufactured using only adhesive bonding, and compared to using sewing, it is possible to easily obtain a cover protector 1 that can maintain excellent adhesive strength and heat insulating performance without increasing the number of work steps or manufacturing costs.

[0127] [Battery Module] Fig. 4 is a schematic cross-sectional view showing a battery module according to an embodiment of the present invention. As shown in Fig. 4, the battery module 100 includes a plurality of storage batteries 110 housed in a battery case 120. The electrode terminals 111 of the storage batteries 110 are connected in series by a bus bar 130.

[0128] The battery case 120 has a ceiling surface 120a, side wall surfaces 120b, and a bottom wall surface 120c inside. The cover protector 1 according to the present embodiment is attached with tape or the like to the entire surface of the ceiling surface 120a of the battery case 120. Although not shown in the drawings, the cover protector 1 is disposed so that the inorganic fiber sheet of the cover protector 1 faces the electrode terminal 111 and so that the heat insulating material of the cover protector 1 faces the ceiling surface of the battery case 120.

[0129] In the battery module 100 configured in this manner, the cover protector 1 has excellent heat insulating properties, so even if the storage battery 110 experiences thermal runaway, becomes hot, or catches fire, it is possible to delay the transfer of heat to the outside of the battery case 120. Furthermore, in this embodiment, the inorganic fiber sheet and the heat insulating material are bonded with high adhesive strength, so that if the storage battery 110 explodes due to thermal runaway, the inorganic fiber sheet will not fall, protecting the heat insulating material and preventing damage to the heat insulating material.

[0130] Although the battery module 100 shown in FIG. 4 has the cover protector 1 attached only to the ceiling surface 120a of the battery case 120, the present invention is not limited to this configuration. For example, attaching the cover protector 1 to at least one of the ceiling surface 120a, side wall surface 120b, and bottom wall surface 120c of the battery case 120 can slow the transfer of heat to the outside of the battery case 120. Attaching the cover protector 1 to all of the ceiling surface 120a, side wall surface 120b, and bottom wall surface 120c of the battery case 120 can further improve thermal insulation and flame resistance. Furthermore, the cover protector 1 may be attached between multiple storage batteries 110.

[0131] 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.

[0132] This application is based on a Japanese patent application (Patent Application No. 2024-114186) filed on July 17, 2024, the contents of which are incorporated herein by reference.

[0133] REFERENCE SIGNS LIST 1 Cover protector 2 Heat insulating material 3 Inorganic fiber sheet 3a Weft 3b Warp 4 Adhesive 5 Joint 6 Inorganic fiber 7 Void 8 Inorganic particle 9 Concave 10 Convex 11 Adhesive material 100 Battery module 110 Storage battery 111 Electrode terminal 120 Battery case 120a Ceiling surface 120b Side wall surface 120c Bottom wall surface 130 Bus bar

Claims

A cover protector having a heat insulating material and an inorganic fiber sheet adhered to the heat insulating material with an adhesive, The oxygen index measured in accordance with JIS K 7201-2 is greater than 24.7%; A cover protector characterized in that the adhesive material constituting the adhesive has a viscosity of 40 Pa·s or more at 250°C. 　 When the ratio of the area of ​​the inorganic fiber sheet covered with the adhesive to the total area of ​​the area facing the thermal insulating material on the surface of the inorganic fiber sheet is defined as the coverage rate of the adhesive, 2. The cover protector according to claim 1, wherein the adhesive has a coverage of 0.50 or more.

3. The cover protector according to claim 2, wherein the adhesive has a coverage rate of 0.76 or more.

2. The cover protector according to claim 1, wherein the oxygen index is 26.0% or more. 　 The cover protector according to claim 1 , wherein the adhesive material includes a polyamide-based organic material.

6. The cover protector according to claim 5, wherein the content of the polyamide organic material is 80% by mass or more with respect to the total mass of the adhesive material. 　 the thermal insulating material includes inorganic particles; The cover protector according to claim 1, wherein a joint portion containing the adhesive and a portion of the inorganic particles is provided between the heat insulating material and the inorganic fiber sheet.

2. The cover protector according to claim 1, wherein the inorganic fiber sheet is formed by processing inorganic fibers containing at least one type of fiber selected from silica fibers, alumina fibers, glass fibers, and metal fibers into a sheet shape. 　 A cover protector having a heat insulating material and an inorganic fiber sheet adhered to the heat insulating material with an adhesive, A cover protector characterized in that the inorganic fiber sheet has recesses and protrusions on the surface facing the insulation material, and at least one of the insulating material and the adhesive that constitute the insulation material is present in at least a portion of the inside of the recesses of the inorganic fiber sheet. 　 The inorganic fiber sheet is formed into a sheet shape by weaving together weft and warp threads made of inorganic fibers, The cover protector according to claim 9, wherein the recessed portion of the inorganic fiber sheet is located at a boundary between the weft threads and the warp threads in a plan view of the inorganic fiber sheet.

10. The cover protector according to claim 9, wherein the inorganic fiber sheet has a surface roughness Ra on the side of the heat insulating material of 50 μm or more and 100 μm or less.

10. The cover protector according to claim 9, wherein a gap having a height of 150 μm or more in a thickness direction of the cover protector is provided between the inorganic fiber sheet and the heat insulating material. 　 A cover protector according to any one of claims 1 to 12; A storage battery and A battery module comprising: a battery case that houses the cover protector and the storage battery. 　 the battery case has a ceiling surface, side wall surfaces, and a bottom wall surface therein; 14. The battery module according to claim 13, wherein the heat insulating material is disposed so as to face at least one selected from the ceiling surface, the side wall surface, and the bottom wall surface, and the cover protector is attached inside the battery case.

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