Cover protector and battery module

Abstract

To provide a cover protector capable of maintaining excellent adhesive performance without peeling a multilayer structure even when receiving high heat or flame from a battery cell causing thermal runaway, thereby maintaining an effect of protecting a heat insulating material from a scattered object and excellent heat insulating performance.SOLUTION: The cover protector 1 has a heat insulating material 2 and an inorganic fiber sheet 3 bonded to the heat insulating material 2 by an adhesive 4. The oxygen index of the cover protector 1 measured according to JISK7201 2 is larger than 24.7%, and the viscosity at 250 °C of an adhesive material constituting the adhesive 4 is 40Pa s or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[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 powder of the aerogel felt material used as the intermediate layer. When the heat insulating material is formed from multiple layers, it is necessary to fix the multiple layers together, for example by bonding them together, to prevent the heat insulating material from decomposing even in the event of a fire. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Chinese Patent Application Publication No. 107914428 Summary of the Invention [Problem to be solved by the invention]

[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 can be easily manufactured, and that can maintain excellent adhesive performance without peeling off its multilayer structure even when exposed to high heat or flames from a battery cell that has experienced thermal runaway, thereby having the effect of protecting the insulation material from flying debris and maintaining excellent insulation performance. Another object of the present invention is to provide a battery module equipped with a cover protector having the above-mentioned heat insulating and adhesive properties. [Means for solving the problem]

[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, 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.

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

[12] .

[0011] [2] 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, The cover protector according to [1], characterized in that the coverage of the adhesive 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], wherein 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 thermal insulation material includes inorganic particles, The cover protector according to any one of [1] to [6], characterized in that a joint containing the adhesive and a portion of the inorganic particles is provided between the heat insulating material and the inorganic fiber sheet.

[0017] [8] A cover protector according to any one of [1] to [7], characterized in that the inorganic fiber sheet is made 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.

[0018] [9] A cover protector having a heat insulating material and an inorganic fiber sheet bonded 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.

[0019]

[10] 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 [9], wherein the recess of the inorganic fiber sheet is located at a boundary between the weft and the warp in a plan view of the inorganic fiber sheet.

[0020]

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

[10] , characterized in that 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] A 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 present 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 cover protector according to any one of [1] to

[12] , A storage battery and A battery module comprising: a battery case that houses the cover protector and the storage battery.

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

[14] .

[0025]

[14] The battery case has a ceiling surface, side wall surfaces, and a bottom wall surface therein,

[13] The battery module according to

[13] , characterized in that the heat insulating material is arranged 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. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0028] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a cover protector according to an embodiment of the present invention. [Figure 2A] FIG. 2A is a photograph, substituted for a drawing, showing a cross section of a cover protector according to an embodiment of the present invention. [Figure 2B] FIG. 2B is a photograph substituting for a drawing, showing an enlarged cross section of the cover protector in a region different from that in FIG. 2A. [Figure 3A] FIG. 3A is a photograph showing the arrangement of the adhesive material before bonding and the coverage of the adhesive after bonding for the cover protector according to this embodiment, when the basis weight is 15 (g / m2). [Figure 3B]FIG. 3B is a photograph showing the arrangement of the adhesive material before bonding and the coverage of the adhesive after bonding for the cover protector according to this embodiment, when the basis weight is 20 (g / m2). [Figure 3C] FIG. 3C is a photograph showing the arrangement of the adhesive material before bonding and the coverage of the adhesive after bonding for the cover protector according to this embodiment, when the basis weight is 25 (g / m2). [Figure 4] FIG. 4 is a schematic cross-sectional view showing a battery module according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[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 some 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 3a of the inorganic fiber sheet 3 coexist can be seen. It can also be seen that, at the joint 5, the fibers of the inorganic fiber sheet 3 (the weft threads 3a) 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 insulating 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 heat insulating material (e.g., inorganic particles 8, inorganic fibers 6, etc.) and the adhesive 4 that constitute the thermal insulating material 2 is present at least partially inside the recesses 9. 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 insulating 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: over 24.7%> In this embodiment, an 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., over 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 conditions for measuring the oxygen index in this embodiment are as follows: Sample shape: 90mm x 10mm (Type III) Sample conditioning (pre-treatment): 23°C ± 2°C, 50% RH ± 5% x 88 hours Measuring device: Candle combustion tester AC3 type (manufactured by Toyo Seiki Seisakusho Co., Ltd.) Measurement conditions: Method A (top 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, making the surface of the inorganic fiber sheet 3 more planar, thereby increasing the adhesive strength between the inorganic fiber sheet 3 and the thermal insulation 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 insulation 2). Furthermore, in the event of thermal runaway of the battery cell, the area of ​​the cover protector that is directly hit by the flame will reach, for example, 1000°C or higher and burn. However, the area surrounding the area directly hit by the flame will 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 can be prevented from peeling off and falling off the thermal insulation 2.

[0039] If the viscosity of the adhesive material constituting the adhesive 4 at 250°C is less than 40 Pa·s, the adhesive 4 will not be able to sufficiently increase its coverage, resulting in reduced adhesive strength and making it difficult to prevent the inorganic fiber sheet 3 from falling off during thermal runaway. Therefore, the viscosity of the adhesive material at 250°C should be 40 Pa·s or higher, preferably 55 Pa·s or higher, and more preferably 70 Pa·s or higher. 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 coverage and adhesive strength will saturate. Therefore, the viscosity of the adhesive material at 250°C is preferably 300 Pa·s or lower.

[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, for example, using a melt viscoelasticity measuring device (AREA-G2) manufactured by TA Instruments Japan Inc. The conditions for measuring the viscosity of the adhesive material in this embodiment are as follows: Measurement method: Dynamic measurement Geometry: 25mm diameter parallel plates Heating rate: 3℃ / min Temperature range: 140℃~320℃ Frequency: 1Hz Measurement interval: 20 seconds (every 1°C) Measurement atmosphere: Nitrogen gas flow

[0041] <Adhesive coverage rate: 0.50 or more> 3A to 3C are photographs showing the placement of the adhesive material before bonding and the coverage of the adhesive after bonding for the cover protector according to this embodiment. In the left images of FIGS. 3A to 3C, the white fibrous material is 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. In the right images, the coverage can be calculated by measuring the total area and the area of ​​the dark black areas.

[0042] In this embodiment, the viscosity of the adhesive material at 250°C is specified. As a result, as shown in FIGS. 3A to 3C , the adhesive 4 is retained not only in the recesses 9 of the inorganic fiber sheet 3 but also over 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. Therefore, the coverage may be 0.98 or less.

[0043] <Ratio of coverage to adhesive weight: 2.7 x 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 ) This means that 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 Figs. 3A to 3C.

[0044] Figure 3A shows a fabric with a basis weight of 15 (g / m 2 ), and Figure 3B shows an example where the basis weight is 20 (g / m 2 ), and Figure 3C shows an example where the basis weight is 25 (g / m 2 ) is an example where the basis weight is at least 15 (g / m 2 )~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) ~ 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 coverage rate to 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 rate can be secured with a small amount of adhesive material, which is preferable. -2 (m 2 / g) or more, and -2 (m 2As described above, the ratio of the coverage 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> As shown in Figures 1, 2A, and 2B, the cover protector 1 has a void 7 between the insulating material 2 and the inorganic fiber sheet 3. The void 7 is often formed near the recess 9 at the boundary between the weft 3a and warp 3b of the inorganic fiber sheet 3, but its location is not particularly limited. The void 7 can be of various sizes. For example, if a void 7 of a predetermined size or larger is present, the insulating performance during normal use at relatively low temperatures can be further improved compared to when the insulating material 2 and the inorganic fiber sheet 3 are tightly attached. To achieve the effect of improving the insulating performance of the cover protector, the cover protector preferably has a void 7 with a height in the thickness direction of 150 μm or more, and more preferably a void 7 with a height of 250 μm or more. Note that if the void 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 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 forms the adhesive 4 that constitute the cover protector 1 according to this embodiment will be described in detail below.

[0049] [Insulation material] The heat insulating material 2 used in the cover protector according to this embodiment is not particularly limited as long as it has a heat insulating effect. Thermal conductivity can be cited as an index of heat insulating effect, and in this embodiment, the heat conductivity of the heat 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 heat conductivity of the heat 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 heat insulating material 2 can be measured in accordance with the "Testing method for thermal conductivity of refractories" described in JIS R 2251.

[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> The inorganic particles may be a single inorganic particle or a combination of two or more 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. The shape of the inorganic particles is not particularly limited, but it is preferable to use at least one selected from nanoparticles, hollow particles, and porous particles. Specific examples include silica nanoparticles, metal oxide particles, inorganic balloons such as microporous particles and hollow silica particles, particles made of thermally expandable inorganic materials, and particles made of hydrous porous bodies.

[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. Furthermore, 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, a 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 referred to as the first inorganic particles and the large-diameter inorganic particles referred to as the second inorganic particles.

[0054] <First inorganic particle> (oxide particles) The use of oxide particles as the first inorganic particles can suppress radiant heat transfer, particularly in high-temperature regions such as those experiencing abnormal heat generation. The oxide particles can be at least one type of particle selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina. That is, among the above-mentioned oxide particles that can be used as inorganic particles, only one type or two or more types of oxide particles can 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 size of oxide particles: 0.001 μm to 50 μm) When the average primary particle size of the oxide particles is 0.001 μm or more, the 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 higher, further improving thermal insulation. On the other hand, when the average primary particle size 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 thermal insulation, especially 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 order of nanometers that are spherical or nearly spherical and have an average primary particle diameter of less than 1 μm. Nanoparticles have low density, which suppresses conductive heat transfer. When nanoparticles are used as the first inorganic particles, finer voids are dispersed, resulting in excellent heat insulation that suppresses convective heat transfer. Therefore, it is preferable to use nanoparticles because they can suppress heat transfer between adjacent nanoparticles during normal use of the battery at room temperature. Furthermore, if nanoparticles with a small average primary particle size are used as oxide particles, the 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 the internal density. This is thought to be because nanoparticles are prone to forming small voids between particles due to electrostatic repulsion, and because their bulk density is low, the particles are 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 / cm 3 ), 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 to 100 nm) If the average primary particle size of the nanoparticles is limited to a predetermined range, even higher heat insulating properties can be obtained. That is, when the average primary particle diameter of the 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, and the thermal insulation properties can be further improved. Furthermore, even when compressive stress is applied, the voids remaining between the nanoparticles and the contact points between many particles suppress conductive heat transfer, allowing the thermal insulation properties of the thermal insulation material to be maintained. The average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more, while the average primary particle size of the 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 their thermal decomposition initiation temperature, they undergo thermal decomposition and release their own water of crystallization, lowering the temperature of the heating element and its surroundings, thereby exhibiting a so-called "endothermic effect." After releasing the water of crystallization, the particles become porous, and the numerous air holes provide thermal insulation. 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), and gallium hydroxide (Ga(OH)3).

[0062] For example, aluminum hydroxide has 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 (Al2O3) and functions as a heat insulating material. 2Al(OH)3 → Al2O3 + 3H2O

[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 heat insulating material 2 are preferably made of inorganic hydrates whose thermal decomposition temperature starts 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 may take some time for the first inorganic particles (inorganic hydrate) near the center of the thermal insulating material 2 to reach their thermal decomposition temperature, and the first inorganic particles near the center of the thermal insulating 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 the hydrous porous material include zeolite, kaolinite, montmorillonite, acid clay, diatomaceous earth, wet silica, dry silica, aerogel, mica, and vermiculite.

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

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

[0070] (Average particle size of inorganic balloons: 1 μm to 100 μm) The average particle size 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 are also effective in 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 insulation. Therefore, when nanoparticles are used as the first inorganic particles, it is preferable to further include second inorganic particles made of a metal oxide that are larger in diameter than the first 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 it is most preferable to use titania.

[0074] When the first inorganic particles are at least one type of particles selected from silica nanoparticles and silica aerogel, and the second inorganic particles are at least one type of particles selected from titania, zircon, zirconia, silicon carbide, zinc oxide, and alumina, the first inorganic particles preferably account for 50% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more of the total mass of the inorganic particles, in order to obtain excellent heat insulating performance within a temperature range of 90° C. or less. Furthermore, the first inorganic particles preferably account for 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less of 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. Also, 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 size 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 size 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 size 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 heat insulating material 2 is appropriately controlled, the heat insulating properties of the heat insulating material 2 can be sufficiently ensured. The total content of inorganic particles is preferably 60% by mass or more, more preferably 70% by mass or more, based on the total mass of the thermal insulation material. If the total content of inorganic particles is too high, the content of organic fibers will relatively decrease, so 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, more preferably 90% by mass or less, based on 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> The inorganic fibers may be a single inorganic fiber or a combination of two or more inorganic fibers. 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 material, 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, availability, etc. Among the inorganic fibers, at least one selected from silica-alumina fiber, alumina fiber, silica fiber, rock wool, alkaline earth silicate fiber, and glass fiber is particularly preferred from the viewpoint of handleability.

[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 the inorganic fibers is 0.1 mm, more preferably 0.5 mm. Meanwhile, the preferred upper limit of the average fiber length of the inorganic fibers is 50 mm, more preferably 10 mm. If the average fiber length of the inorganic fibers is less than 0.1 mm, the inorganic fibers are less likely to intertwine with each other, which may reduce the mechanical strength of the insulating material. Meanwhile, if the average fiber length exceeds 50 mm, although a reinforcing effect is obtained, the inorganic fibers may not be able to intertwine tightly with each other, or may curl up as a single inorganic fiber, which may result in reduced 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 this embodiment, when the heat 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 heat 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, compressive 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 fiber> The organic fibers have the effect of imparting flexibility to the insulating material and, by forming a skeleton, have the effect of increasing the strength of the insulating material. Furthermore, when 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, when the insulating material contains an appropriate amount of organic fibers, 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 fibers, polyvinyl alcohol (PVA) fibers, polyethylene fibers, nylon fibers, polyurethane fibers, and ethylene-vinyl alcohol copolymer fibers can be used.

[0087] When the 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 there are no particular limitations on the lower limit of the glass transition point of the organic fiber, 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 during the cooling step during production, and the resin binder will therefore be able to fully reinforce the skeleton. 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 well dispersed, thereby achieving an even greater skeleton reinforcement effect. 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, with the melting point of the first organic material being higher than that of the second organic material.

[0091] (First organic material) In this embodiment, when a core-sheath binder fiber 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. The first organic material may be 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, and 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, and more preferably 100° C. or higher. The melting point of the second organic material is preferably 150° C. or lower, and more preferably 130° C. or lower.

[0093] (organic fiber content) If the content of organic fibers in the heat insulating material 2 is appropriately controlled, the effect of reinforcing the skeleton can be sufficiently obtained. The organic fiber content is preferably 5% by mass or more, more preferably 10% by mass or more, based on the total mass of the thermal insulation material. If the organic fiber content is too high, the inorganic particle content will relatively decrease, so in order to obtain the desired thermal insulation performance, the organic fiber content is preferably 25% by mass or less, more preferably 20% by mass or less, based on the total mass of the thermal insulation material.

[0094] (fiber length of organic fiber) There are no particular limitations on the fiber length of the organic fibers, but from the viewpoint of ensuring moldability and processability, it is preferable that the average fiber length of the organic fibers be 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 heat insulating material, it is preferable that the average fiber length of the organic fibers is 0.5 mm or more.

[0095] (infusible fiber) The thermal insulation material 2 may contain infusible fibers as fibers. Examples of infusible fibers include fibers obtained by infusibility treatment of thermoplastic resins such as polyacrylonitrile, cellulose, and pitch. The infusible fibers are, for example, fibers that have been infusible treated, and examples of infusible treatment include a method of crosslinking by irradiation with radiation or an electron beam, and a method of exposing the fibers to high temperatures in oxygen or water vapor to make them 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 minimal, 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 if the fibers are highly carbonized or if carbonization progresses due to thermal runaway. Furthermore, the random orientation of the fibers makes them more likely to come into point contact 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 is 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 is 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 that of the single-component organic fiber. For example, a resin binder containing at least one resin 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 also contain a hot melt powder. When using the core-sheath binder fiber, the hot melt powder may contain, for example, a third organic material different from the first and second organic materials, and be a powder that melts when heated. When the hot melt powder is added to the material mixture for the insulating material 2 and heated, it melts and then hardens, taking with it the surrounding inorganic particles, upon cooling. This further reduces the risk of inorganic particles 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 using core-sheath binder fibers as the organic fibers, 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 fibers, the heating temperature can be set to melt the sheath and hot melt powder while leaving the core intact. 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 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 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 will fuse 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 latitude 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. Components constituting the hot melt powder include polyethylene, polyester, polyamide, and ethylene vinyl acetate.

[0111] (Hot melt powder content) When hot melt powder is added to the insulating material to prevent inorganic particles from falling off, even a small amount of hot melt powder can be used to prevent powder from falling off. Therefore, the hot melt powder content is preferably 0.5% by mass or more, and more preferably 1% by mass or more, of the total mass of the insulating material. On the other hand, when the content of the hot melt powder is increased, the content of inorganic particles and the like is relatively decreased. Therefore, in order to obtain the desired heat insulating performance, the content of the hot melt powder is preferably 5 mass % or less, and more preferably 4 mass % or less, of the total mass of the materials constituting the heat 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, and more preferably at least 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, and more preferably at least 20°C lower, than the melting point of the first organic material constituting the core. Setting the heating temperature at this level allows for the formation of a strong skeleton, 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 reinforcing the heat insulating material and 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, the method for producing the heat insulating material 2 is not particularly limited, and commonly used wet and dry methods can be used to produce the heat insulating material 2. As for the materials used in production, a material suitable for the production 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 made by processing inorganic fibers into a sheet, and the inorganic fibers used are not particularly limited. For example, the inorganic fibers described above for the heat insulating material 2 can be used. Among these, 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 of inorganic fiber sheet Ra: 50 μm to 100 μm) As described above, the inorganic fiber sheet 3 has recesses 9 and protrusions 10 on at least the surface facing the thermal insulating material 2. The presence of the recesses 9 and protrusions 10 in the inorganic fiber sheet 3 makes it easier for at least one of the adhesive 4 and the thermal insulating material to penetrate into the recesses 9, thereby increasing the adhesive strength between the thermal insulating material 2 and the inorganic fiber sheet 3. In this embodiment, the surface roughness Ra is used as an index of the recesses 9 and 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 placing an adhesive material between a heat insulating material 2 and an 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 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. If 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 will not be 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, based on the total mass of the adhesive material. On the other hand, if 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 will not be 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, based on the total mass of the adhesive material.

[0122] [Cover protector manufacturing method] Next, an example of a method for 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 process> First, the adhesive material 11 that constitutes 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] <Joining process> 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 joints 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, a battery module 100 includes a plurality of storage batteries 110 housed in a battery case 120. 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 to the entire surface of the ceiling surface 120a of the battery case 120 with tape or the like. 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 side 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 and will protect the heat insulating material, thereby 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 the thermal insulation and fire resistance. Furthermore, the cover protector 1 may be attached between multiple storage batteries 110. [Explanation of symbols]

[0131] 1 Cover protector 2. Insulation 3. Inorganic fiber sheet 3a weft 3b warp thread 4. Adhesive 5 Joint 6. Inorganic fibers 7 Cavity 8 Inorganic particles 9 Recess 10 Convex part 11 Adhesive materials 100 battery modules 110 Storage battery 111 Electrode terminal 120 Battery Case 120a Ceiling surface 120b Side wall 120c Bottom wall surface 130 Busbar

Claims

1. 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.

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

4. 2. The cover protector according to claim 1, wherein the oxygen index is 26.0% or more.

5. The cover protector according to claim 1 , wherein the adhesive material includes a polyamide-based organic material.

6. 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.

7. 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.

8. 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.

9. 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.

10. 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.

11. 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.

12. 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.

13. 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.

14. 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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