Inter-cell thermal insulation material sheet for electric vehicle battery

Abstract

This inter-cell thermal insulation material sheet for an electric vehicle battery includes a silica aerogel and fibers, and has a plurality of pores on one surface and the other surface in the thickness direction. The ratio of the number of pores on one surface to the number of pores on the other surface is preferably 1.3 or more.

Description

Insulation sheet between battery cells for electric vehicles

[0001] This disclosure relates to an intercellular thermal insulation sheet for electric vehicle battery cells. This specification claims priority to, and references herein to, all of the following: U.S. Provisional Application No. 63 / 713,142 filed October 29, 2024; JP Patent Application No. 2024-191884 filed October 31, 2024; JP Patent Application No. 2025-069515 filed April 21, 2025; and U.S. Application No. 19 / 211,647 filed May 19, 2025.

[0002] Silica aerogel is composed of multiple linked silica nanoparticles forming a framework, with pores between the framework that are smaller than the mean free path of air. This fine, porous structure results in low thermal conductivity, making it useful as a component material for insulation in automotive parts, building materials for houses, industrial equipment, and other applications.

[0003] Insulating materials containing silica aerogel often have low surface mechanical strength, and powder shedding due to impact is a problem. For example, when used as insulating material for automobile batteries, the pressure caused by the thermal expansion of the battery can lead to powder shedding, potentially degrading the performance of electronic devices. As a solution, for example, Japanese Patent Publication No. 2024-97328 and Japanese Patent Publication No. 2023-132944 (Patent Documents 1 and 2) describe how powder shedding can be suppressed by incorporating fibrous mineral fibers and hot melt powder into a silica aerogel sheet, or by sealing the surface with a film. Furthermore, Japanese Patent Publication No. 2023-35097 (Patent Document 3) describes how powder shedding can be suppressed by providing an insulating elastic member containing an elastic layer on one side of the silica aerogel sheet and a cover layer on the other side, or by covering the sheet and the entire sheet with an outer covering.

[0004] Japanese Patent Publication No. 2024-97328, Japanese Patent Publication No. 2023-132944, Japanese Patent Publication No. 2023-35097

[0005] Among the conventional technologies described above, the film-forming technology does not aim to suppress aerogel shedding (hereinafter referred to as powder shedding) by causing the silica aerogel, which was physically and chemically bonded to the fibers, to peel off when stress is applied to the silica aerogel sheet. Furthermore, according to the technology described in Japanese Patent Application Publication No. 2023-132944 (Patent Document 2), the hardened layer formed by the hot melt powder may reduce the thermal insulation performance of the sheet. On the sheet surface, the sheet surface that is subjected to stress caused by the expansion of the battery and the sheet surface that is close to the vibration source tend to be prone to powder shedding due to the transmission of stress and vibration. When aerogel powder shedding occurs, the amount of aerogel present inside the thermal insulation sheet becomes uneven, and the thermal insulation performance may not be fully exhibited in some areas.

[0006] This disclosure aims to provide an inter-cell insulation sheet for electric vehicle batteries containing silica aerogel that can prevent powder shedding.

[0007] This disclosure provides the following [1] to

[15] : [1] An electric vehicle battery cell insulation sheet comprising silica aerogel and fibers, having a plurality of voids on one surface and the other surface in the thickness direction, wherein the ratio of the number of voids on one surface to the number of voids on the other surface is 1.3 or more. [2] The number of voids on one surface is 25,000 to 225,000 per m ２ The sheet described in [1]. [3] The number of voids on the other surface is 10,000 to 50,000 per m ２The sheet described in [1] or [2]. [4] The sheet described in any one of [1] to [3], wherein the difference between the surface roughness Sa of one surface and the surface roughness Sa of the other surface is 10 μm or more. [5] The sheet described in any one of [1] to [4], wherein the difference between the surface roughness Sa of one surface and the surface roughness Sa of the other surface is 30 μm or more. [6] The sheet described in any one of [1] to [5], wherein the surface roughness Sa of one surface is 60 μm or more. [7] The sheet described in any one of [1] to [6], wherein the surface roughness Sa of one surface is 80 to 250 μm. [8] The sheet described in any one of [1] to [7], wherein the surface roughness Sa of the other surface is 180 μm or less. [9] The sheet described in any one of [1] to [8], wherein the surface roughness Sa of the other surface is 30 to 180 μm.

[10] The sheet according to any one of [1] to [9], further comprising a film covering at least a portion of one surface and the other surface.

[11] The sheet according to any one of [1] to [9], further comprising an elastic layer laminated on at least a portion of one surface and the other surface.

[12] The sheet according to any one of [1] to [9], further comprising a film covering one surface and the other surface, and an elastic layer laminated on one surface or the other surface via the film.

[13] An electric vehicle battery cell insulation sheet comprising silica aerogel and fibers, having a plurality of irregularities on one surface and the other surface in the thickness direction, and having a ratio of the surface roughness of one surface to the surface roughness of the other surface of 1.3 or more.

[14] The number of pores on one surface is 100,000 to 150,000 per m ２ The surface roughness Sa of the pores on one surface is 80 to 100 μm, and the number of pores on the other surface is 20,000 to 30,000 per square meter. ２ The sheet according to [1], wherein the surface roughness Sa of the voids on the other surface is 30 to 50 μm.

[15] The sheet according to

[13] , wherein the ratio of the surface roughness of one surface to the surface roughness of the other surface is 2.3 to 4.4, and the difference between the surface roughness of one surface and the surface roughness of the other surface is 30 to 100 μm.

[0008] According to this embodiment, it is possible to provide an electric vehicle battery insulation sheet that prevents powder shedding and exhibits good heat insulation properties. In other words, according to this embodiment, the occurrence of powder shedding can be suppressed by responding to the difference in stress on both sides of the sheet, so the overall heat insulation performance of the sheet can be improved and it is useful as an insulation sheet between electric vehicle battery cells.

[0009] Figure 1 shows an example of an image obtained when one surface (Surface A) of a sheet according to one embodiment of the present disclosure is binarized. Figure 2 shows an example of an image obtained when the other surface (Surface B) of a sheet according to one embodiment of the present disclosure is binarized.

[0010] Next, embodiments of the present invention will be described in detail. In this specification, when "X to Y" (where X and Y are any numbers) is written, unless otherwise specified, it means "X or greater and Y or less," and also includes the meaning of "preferably greater than X" or "preferably less than Y."

[0011] In this specification, unless otherwise specified, the upper or lower limits of numerical ranges described in stages may be arbitrarily combined with the upper or lower limits of numerical ranges in other stages. Furthermore, in numerical ranges described in this specification, the upper or lower limits of those ranges may be replaced with the values ​​shown in the examples.

[0012] In this specification, "X and / or Y (where X and Y are any configuration)" means at least one of X and Y, and can mean X only, Y only, or X and Y.

[0013] 1. Materials of the insulation sheet: The insulation sheet is a sheet containing silica aerogel and fibers.

[0014] 1.1 Silica Aerogel In this specification, silica aerogel is a structure formed by the aggregation of silica microparticles as primary particles to form secondary particles, and consists of a framework mainly composed of these particles and pores between them.

[0015] -Average particle size of primary particles- The average particle size of silica microparticles (primary particles) that form the backbone of silica aerogel is usually around 2 to 5 nm.

[0016] The average particle size of silica nanoparticles can be measured by electron microscopy.

[0017] - Pore Size - The pores in silica aerogel are usually mostly mesopores. Mesopores have a diameter of 50 nm or less, which is smaller than the mean free path of air. Therefore, air convection is restricted and heat transfer is inhibited, allowing for thermal insulation performance. There is no particular lower limit, but 10 nm or more is preferred.

[0018] The shape of silica aerogel is not particularly limited; it can be spherical, irregularly shaped, or as a lump. For example, in the case of a spherical shape, it is easier to achieve close packing, allowing for a larger amount to be used, which greatly enhances the effect of improving thermal insulation.

[0019] -Average particle diameter of secondary particles- The average particle diameter of the particles (mainly secondary particles) that make up silica aerogel is usually 1 μm or more, preferably 10 μm or more. The larger the particle diameter, the smaller the surface area and the larger the pore volume, which can improve the heat insulation effect. There is no particular upper limit, but for example, it is 200 μm or less. The average particle diameter of secondary particles is the median diameter (i.e., D50) determined from the volume-based particle size distribution measured by laser diffraction and scattering.

[0020] The insulation sheet may contain one type of silica aerogel, or it may contain two or more different types of silica aerogel, preferably two or more silica aerogels with different particle sizes. This allows the smaller diameter silica aerogels to fill the gaps between the larger diameter silica aerogels, increasing the filling volume and further improving the insulation performance.

[0021] Silica aerogel may be formed by impregnating fibers with a liquid coating solution (including a slurry) containing a binder, as described later, and then drying it. Alternatively, silica aerogel may be formed by impregnating fibers with its precursor sol, then gelling it by heating, and finally drying it.

[0022] Silica aerogel may be synthesized as needed, or a commercially available product may be used.

[0023] 1.2 Fibers (Reinforcement Fibers) Examples of fibers include inorganic fibers such as glass fibers, ceramic fibers, quartz fibers, alumina fibers, silica fibers, silicon carbide fibers, boron fibers, and metal fibers (e.g., aluminum, iron); and organic fibers such as polyamide fibers, polyimide fibers, aromatic polyamide fibers (aramid fibers), polyolefin fibers (e.g., polyethylene fibers, polypropylene fibers), fluorine fibers (e.g., polytetrafluoroethylene fibers), acrylic fibers, poly(p-phenylene benzbisoxazole) (PBO) fibers, polyarylate fibers, polyurethane fibers, polyetheretherketone (PEEK) fibers, polyethersulfone (PES) fibers, polyetherimide (PEI) fibers, polyetherketone (PEK) fibers, and polyphenylene sulfide (PPS) fibers. The fibers may also be natural fibers such as wood fibers, silk, hemp, and wool fibers. Of these, fibers having strength and / or heat resistance are preferred, inorganic fibers are more preferred, and glass fibers are even more preferred. The fibers are discontinuous fibers; bundles of fibers; and fabrics such as nonwoven or woven fabrics, or a combination thereof. The fibers contained in the heat insulating sheet preferably include fabric, more preferably nonwoven fabric. This allows for further improvement of mechanical strength. By using fabrics that have been perforated or treated to create a napped surface (preferably nonwoven fabric, more preferably glass nonwoven fabric) as fibers, the porosity ratio and surface roughness of the sheet surface can be easily adjusted.

[0024] 1.3 The optional component insulation material may contain optional components other than silica aerogel and fibers. Examples of optional components include binders and thickeners.

[0025] - Binder - By adding a binder, degradation in high-temperature atmospheres can be reduced and cracking can be suppressed. The binder may be either an inorganic or organic material. Examples of inorganic materials include talc, carbon black, kaolinite, montmorillonite, mica, silica (e.g., precipitated silica, gel silica, fused silica), wollastonite, magnesium silicate, titania, metal carbides (e.g., silicon carbide, titanium carbide, or tungsten carbide), metal oxides (e.g., manganese oxide, nickel oxide, tin oxide, silver oxide, bismuth trioxide, chromium oxide, iron oxide, alumina, zirconia, manganese dioxide), metal nitrides (e.g., silicon nitride, aluminum nitride), ilmenite, zirconium silicate, potassium titanate, glass flakes, water glass (sodium silicate), calcium carbonate, barium sulfate, hydraulic materials (e.g., cement, gypsum, magnesium silicate), quicklime, and slaked lime. Combinations of these are also possible. From these, an appropriate material can be selected as needed. For example, silica is preferred because it is easily compatible with silica aerogel, inexpensive, and readily available. Hydraulic materials are also preferred because they can form a high-strength insulating layer by reacting with water, a solvent commonly used in the manufacture of silica aerogel, filling the gaps between silica particles and acting as a binder, and are inexpensive and readily available. Furthermore, materials with a large specific surface area and hardness may be selected.

[0026] The organic material is preferably an aqueous binder (a binder that is soluble or dispersible in water (capable of forming an emulsion)), and may be a substance that imparts hydrophilic groups to the silica aerogel, or a so-called surfactant.

[0027] The glass transition temperature (Tg) of the organic material is preferably -5°C or lower, and more preferably -20°C or lower. This can result in good adhesion to silica aerogel, improve the flexibility of the sheet, and suppress cracking.

[0028] Examples of organic binders include resins such as acrylic resin, urethane resin, and mixtures of acrylic and urethane resin; and rubbers such as styrene-butadiene rubber (SBR), nitrile rubber, silicone rubber, urethane rubber, and acrylic rubber, with urethane resin and SBR being preferred. This improves the flexibility of the sheet, enabling the creation of a flexible sheet. When using a binder, a crosslinking agent may also be used in combination. This allows the binder to be crosslinked, further improving the strength of the sheet.

[0029] -Thickening Agents- By using thickening agents, the dispersibility of silica aerogel in a solvent (usually water) can be increased, improving its processability. It is also possible to impart flexibility to the sheet and suppress cracking. Examples of thickening agents include polysaccharides such as carboxymethylcellulose (CMC), polyethylene oxide (PEO), carboxyethylcellulose, carboxypropylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, xanthan gum, agarose, carrageenan, and glucomannan; and polyvinyl alcohol.

[0030] -Flame Retardants- By using flame retardants, the flame retardancy of the sheet can be increased. Examples of flame retardants include halogen-based, phosphorus-based, and metal hydroxide-based flame retardants. Phosphorus-based flame retardants (e.g., ammonium polyphosphate, red phosphorus, phosphate esters) are preferred, water-insoluble phosphorus-based flame retardants are more preferred, and ammonium polyphosphate is even more preferred.

[0031] The optional components are not limited to those listed above. For example, one or more selected from preservatives, colorants, infrared shielding particles, and radiation absorbing / reflecting materials may be used.

[0032] 1.4 Composition -Silica Aerogel Content- The silica aerogel content in the thermal insulation sheet is usually 10% by mass or more, preferably 20% by mass or more, and more preferably 30% by mass or more, based on 100% by mass of the total mass of the thermal insulation sheet. This allows for better thermal insulation. The upper limit is usually 80% by mass or less, preferably 60% by mass or less, and more preferably 40% by mass or less. This suppresses a decrease in mechanical strength and suppresses so-called powder shedding.

[0033] -Fiber Content- The fiber content in the insulation sheet is usually 20% by mass or more, preferably 30% by mass or more, based on 100% by mass of the total mass of the insulation sheet. This can further improve the mechanical strength. The upper limit is usually 70% by mass or less, preferably 60% by mass or less. This allows the sheet to exhibit mechanical strength commensurate with its fiber content.

[0034] 2. Insulation Sheet The insulation sheet is made of the above materials and preferably satisfies one or more of the following shapes and physical properties.

[0035] 2.1 Sheet Thickness The insulation sheet is usually flat. The sheet thickness is not particularly limited, but for example, it can be 10 mm or less, 8 mm or less, 3 mm or less, 2.5 mm or less, or 2 mm or less. This allows the sheet strength to be maintained within an appropriate thickness range. The lower limit is usually 0.1 mm or more, preferably 0.5 mm or more, or 1 mm or more. The thickness is preferably approximately uniform, and the thickness variation may be, for example, 5% or less, 4% or less, or 3% or less.

[0036] 2.2 Surface Shape The insulation sheet has irregularities, voids (openings), etc., on its surface (one side and the other side when viewed from the horizontal direction). There are usually multiple voids, and they may be randomly arranged. The shape of the voids is not particularly limited and may be circular, polygonal, or irregular. The irregularities are usually not uniform and may be unevenly distributed.

[0037] The properties of the sheet surface differ between the two surfaces of the sheet, that is, one side and the other side when viewed from the thickness direction of the sheet. As a result, for example, on one side (hereinafter referred to as surface A), where the number (distribution) of pores is relatively large or the surface roughness is relatively large, even if the silica aerogel that was physically and chemically bonded to the fibers peels off when stress, vibration, etc. is applied to the silica aerogel sheet, the large number (distribution) of pores or the large surface roughness makes it easy to capture the peeled silica aerogel, thus suppressing powder falling to the lower part. Furthermore, since surface A has a predetermined shape and / or is formed of fibers, adhesion to films, etc. can be enhanced, so when stress, vibration, etc. is applied to the silica aerogel sheet, peeling of the film, etc. and silica aerogel is suppressed, and as a result, powder falling to the lower part can be suppressed.

[0038] On the other hand, on the other surface (hereinafter referred to as surface B), where the number (distribution) of pores is relatively small, or the surface roughness is relatively small, there is less stress and vibration applied to the silica aerogel sheet. Considering that the silica aerogel, which was physically and chemically bonded to the fibers, is less likely to peel off, the number (distribution) of pores that cause powder shedding, or the size of the surface roughness, can be reduced.

[0039] As explained above, the different surface properties of the sheets help to suppress powder shedding throughout the sheet, thus preventing a decrease in thermal insulation performance.

[0040] - Number of voids - The number of voids differs between surfaces A and B. The ratio of the number of voids on surface A to the number of voids on surface B is preferably 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, or 2.1 or more; more preferably 2.2 or more, 2.3 or more, 2.4 or more, 2.5 or more, or 2.6 or more; even more preferably 2.7 or more, 2.8 or more, 2.9 or more, 3.0 or more, 3.1 or more, 3.2 or more, 3.3 or more, 3.4 or more, 3.5 or more, 3.6 or more, 3.7 or more, 3.8 or more, 3.9 or more, or 4.0 or more. The upper limit is preferably 9.0 or less, 8.9 or less, 8.8 or less, 8.7 or less, 8.6 or less, 8.5 or less, 8.4 or less, 8.3 or less, 8.2 or less, or 8.1 or less, more preferably 8.0 or less, 7.9 or less, 7.8 or less, 7.7 or less, 7.6 or less, 7.5 or less, 7.4 or less, 7.3 or less, 7.2 or less, or 7.1 or less, and even more preferably 7.0 or less. Therefore, the preferred range of the ratio is 1.3 or more, more preferably 1.3 to 9.0, 1.3 to 8.9, 1.3 to 8.8, 1.3 to 8.7, 1.3 to 8.6, 1.3 to 8.5, 1.3 to 8.4, 1.3 to 8.3, 1.3 to 8.2, 1.3 to 8.1, 1.3 to 8.0, 1.3 to 7.9, 1.3 to 7.8, 1.3 to 7.7, 1.3 to 7 6, 1.3-7.5, 1.3-7.4, 1.3-7.3, 1.3-7.2, 1.3-7.1, 1.3-7.0, 1.4-7.0, 1.5-7.0, 1.6-7.0, 1.7-7.0, 1.8-7.0, 1.9-7.0, 2.0-9.0, 2.0-8.9, 2.0-8.8, 2.0-8.7, 2.0-8.6, 2.0-8. 5, 2.0-8.4, 2.0-8.3, 2.0-8.2, 2.0-8.1, 2.0-8.0, 2.0-7.9, 2.0-7.8, 2.0-7.7, 2.0-7.6, 2.0-7.5, 2.0-7.4, 2.0-7.3, 2.0-7.2, 2.0-7.1, 2.0-7.0, 2.1-7.0, 2.2-9.0, 2.2-8.9 , 2.2-8.8, 2.2-8.7, 2.2-8.6, 2.2-8.5, 2.2-8.4, 2.2-8.3, 2.2-8.2, 2.2-8.1, 2.2-8.0, 2.2-7.9, 2.2-7.8, 2.2-7.7, 2.2-7.6, 2.2-7.5, 2.2-7.4, 2.2-7.3, 2.2-7.2, 2.2-7.1,2.2 to 7.0, 2.7 to 9.0, 2.7 to 8.9, 2.7 to 8.8, 2.7 to 8.7, 2.7 to 8.6, 2.7 to 8.5, 2.7 to 8.4, 2.7 to 8.3, 2.7 to 8.2, 2.7 to 8.1, 2.7 to 8.0, 2.7 to 7.9, 2.7 to 7.8, 2.7 to 7.7, 2.7 to 7.6, 2.7 to 7.5, 2.7 to 7.4, 2.7 to 7.3, 2.7 to 7.2, 2.7 to 7.1, 2.7 to 7.0, 2.8 to 7.0, 2.9 to 7.0, 3.0 to 7.0, 3.1 to 7.0, 3.2 to 7.0, 3.3 to 7.0, 3.4 to 7.0, 3.5 to 7.0, 3.6 to 7.0, 3.7 to 7.0, 3.8 to 7.0, 3.9 to 7.0, 4.0 to 9.0, 4.0 to 8.9, 4.0 to 8.8, 4.0 to 8.7, 4.0 to 8.6, 4.0 to 8.5, 4.0 to 8.4, 4.0 to 8.3, 4.0 to 8.2, 4.0 to 8.1, 4.0 to 8.0, 4.0 to 7.9, 4.0 to 7.8, 4.0 to 7.7, 4.0 to 7.6, 4.0 to 7.5, 4.0 to 7.4, 4.0 to 7.3, 4.0 to 7.2, 4.0 to 7.1, 4.0 to 7.0. Thus, surface B can better prevent powder shedding and exhibit better heat insulation performance, while surface A can better prevent powder shedding and improve adhesion, thereby better demonstrating heat insulation performance respectively.,

[0041] The number of pores on surface A is preferably 25,000 / m ２ or more, 26,000 / m ２ or more, 27,000 / m ２ or more, 28,000 / m ２ or more, 29,000 / m ２ or more, 30,000 / m ２ or more, 31,000 / m ２ or more, 32,000 / m ２ or more, 33,000 / m ２ or more, or 34,000 / m ２ or more, more preferably 35,000 / m ２ or more, 36,000 / m ２ or more, 37,000 / m ２ or more, 38,000 / m ２ or more, 39,000 / m ２ or more, 40,000 / m ２ or more, 41,000 / m ２ or more, 42,000 / m ２More than 43,000 pieces / m ２ More than or equal to 44,000 pieces / m ２ More than 45,000 pieces / m ２ More than 46,000 pieces / m ２ More than 47,000 pieces / m ２ More than 48,000 pieces / m ２ More than 49,000 pieces / m ２ More preferably, 50,000 pieces / m ２ This completes the process. This captures powder that falls off the sheet surface and suppresses powder shedding. The upper limit is preferably 225,000 particles / m ２ Below, 220,000 pieces / m ２ Below, 215,000 pieces / m ２ Below, 210,000 pieces / m ２ Below, 205,000 pieces / m ２ More preferably, 200,000 pieces / m ２ Below, 195,000 pieces / m ２ Below, 190,000 pieces / m ２ Below, 185,000 pieces / m ２ Below, 180,000 pieces / m ２ Below, 175,000 pieces / m ２ Below, 170,000 pieces / m ２ Below, 165,000 pieces / m ２ Below, 160,000 pieces / m ２ The following, or 155,000 pieces / m ２ More preferably, 150,000 pieces / m ２ This prevents the pores themselves from falling off the sheet surface, thus suppressing powder shedding. Therefore, a density of 25,000 to 225,000 pores / m is preferred. ２ , 26,000~220,000 pieces / m ２ , 27,000~220,000 pieces / m ２ , 28,000~220,000 pieces / m ２ , 29,000-215,000 pieces / m ２ , 30,000~215,000 pieces / m ２ , 31,000~215,000 pieces / m ２ , 32,000~210,000 pieces / m ２, 33,000~210,000 pieces / m ２ , 34,000~205,000 pieces / m ２ More preferably, 35,000 to 200,000 particles / m ２ , 36,000~195,000 pieces / m ２ , 37,000~195,000 pieces / m ２ , 38,000~195,000 pieces / m ２ , 39,000~190,000 pieces / m ２ , 40,000~190,000 pieces / m ２ , 41,000~185,000 pieces / m ２ , 42,000~185,000 pieces / m ２ , 43,000~170,000 pieces / m ２ , 44,000~170,000 pieces / m ２ , 45,000~165,000 pieces / m ２ , 46,000~165,000 pieces / m ２ , 47,000~160,000 pieces / m ２ , 48,000~160,000 pieces / m ２ , 49,000~155,000 pieces / m ２ More preferably 50,000 to 150,000 pieces / m ２ That is the case.

[0042] The number of pores on surface B is preferably 10,000 per square meter. ２ Above, 11,000 pieces / m ２ Above, 12,000 pieces / m ２ Above, 13,000 pieces / m ２ Above, 14,000 pieces / m ２ Above, 15,000 pieces / m ２ Above, 16,000 pieces / m ２ Above, 17,000 pieces / m ２ Above, 18,000 pieces / m ２ More than or equal to 19,000 pieces / m ２ More preferably, 20,000 pieces / m ２ This completes the process. This captures powder that falls off the sheet surface and suppresses powder shedding. The upper limit is preferably 50,000 particles / m ２ Below, 49,000 pieces / m ２Less than 48,000 / m ２ Less than 47,000 / m ２ Less than 46,000 / m ２ Less than 45,000 / m ２ Less than 44,000 / m ２ Less than 43,000 / m ２ Less than 42,000 / m ２ Less than 41,000 / m ２ Less than 40,000 / m ２ Less than 39,000 / m ２ Less than 38,000 / m ２ Less than 37,000 / m ２ Less than 36,000 / m ２ Less than 35,000 / m ２ Less than 34,000 / m ２ Less than 33,000 / m ２ Less than 32,000 / m ２ Less than or 31,000 / m ２ More preferably less than 30,000 / m ２ It is as follows. Thereby, the fall of the pores themselves from the sheet surface can be suppressed, and powder scattering can be suppressed. Therefore, preferably 10,000 to 50,000 / m ２ 10,000 to 49,000 / m ２ 10,000 to 48,000 / m ２ 11,000 to 47,000 / m ２ 11,000 to 46,000 / m ２ 12,000 to 45,000 / m ２ 12,000 to 44,000 / m ２ 13,000 to 43,000 / m ２ 13,000 to 42,000 / m ２ 14,000 to 41,000 / m ２ 14,000 to 40,000 / m ２ 15,000 to 39,000 / m ２ 15,000 to 38,000 / m ２ 16,000 to 37,000 / m ２ 16,000 to 36,000 / m ２ 17,000 to 35,000 / m２ , 17,000-34,000 pieces / m ２ , 18,000-33,000 pieces / m ２ , 18,000-32,000 pieces / m ２ ,,19,000~31,000 pieces / m ２ More preferably 20,000 to 30,000 pieces / m ２ That is the case.

[0043] The number of voids can be counted using the following method: Cut the sheet into 15cm x 15cm sections and photograph five arbitrary locations on the sheet surface using a digital camera (e.g., Canon PowerShot SX720 HS). Using image processing software (e.g., ImageJ), extract a 2cm x 2cm (200 pixels x 200 pixels) image from the captured images. Using ImageJ's binarization function, binarize areas with a brightness of 125 or less as voids (for example, Figures 1 and 2 show examples of binarized surfaces A and B, respectively). Next, using ImageJ's particle analysis function, remove particles smaller than 4 pixels² as noise and count them as voids. In this way, calculate the average value of the five locations and use it as the number of voids. Note that voids may be covered by glass fibers, etc., and voids that penetrate from the surface to the back surface are also included. Furthermore, the diameter of the voids counted under the above conditions is greater than 0.2 mm.

[0044] The degree of unevenness on the sheet surface can be expressed by the surface roughness Sa (arithmetic mean height). The lower limit of the surface roughness of surface A is preferably 60 μm or more, 61 μm or more, 62 μm or more, 63 μm or more, or 64 μm or more, more preferably 65 μm or more, 66 μm or more, 67 μm or more, 68 μm or more, or 69 μm or more, even more preferably 70 μm or more, 71 μm or more, 72 μm or more, 73 μm or more, 74 μm or more, 75 μm or more, 76 μm or more, 77 μm or more, 78 μm or more, or 79 μm or more, 80 μm or more, 81 μm or more, 82 μm or more, 83 μm or more, 84 μm or more, 85 μm or more, 86 μm or more, 87 μm or more, 88 μm or more, 89 μm or more, or 90 μm or more. This captures powder that falls off the sheet surface, suppressing powder shedding.

[0045] The upper limit of the surface roughness of surface A is preferably 250 μm or less, 249 μm or less, 248 μm or less, 247 μm or less, 246 μm or less, 245 μm or less, 244 μm or less, 243 μm or less, 242 μm or less, or 241 μm or less, 240 μm or less, 239 μm or less, 238 μm or less, 237 μm or less, 236 μm or less, 235 μm or less, 233 μm or less, 232 μm or less, or 231 μm or less, 230 μm or less, 229 μm or less, 228 μm or less, 227 μm or less, 226 μm or less, 225 μm or less, 224 μm or less, 223 μm or less, 22 2 μm or less, or 221 μm or less, 220 μm or less, 219 μm or less, 218 μm or less, 217 μm or less, 216 μm or less, 215 μm or less, 214 μm or less, 213 μm or less, 212 μm or less, or 211 μm or less, 210 μm or less, 209 μm or less, 208 μm or less, 207 μm or less, 206 μm or less, 205 μm or less, 204 μm or less, 203 μm or less, 202 μm or less, or 201 μm or less, 200 μm or less, 199 μm or less, 198 μm or less, 197 μm or less, 196 μm or less, 195 μm or less, 194 μm or less, 193 μm or less, 192 μm m or less, or 191 μm or less, 190 μm or less, 189 μm or less, 188 μm or less, 187 μm or less, 186 μm or less, 185 μm or less, 184 μm or less, 183 μm or less, 182 μm or less, or 181 μm or less, 180 μm or less, 179 μm or less, 178 μm or less, 177 μm m or less, 176 μm or less, 175 μm or less, 174 μm or less, 173 μm or less, 172 μm or less, or 171 μm or less, 170 μm or less, 169 μm or less, 168 μm or less, 167 μm or less, 166 μm or less, 165 μm or less, 164 μm or less, 163 μm or less, 162 μm or less Below, or 161 μm or less, 160 μm or less, 159 μm or less, 158 μm or less, 157 μm or less, 156 μm or less, 155 μm or less, 154 μm or less, 153 μm or less, 152 μm or less, or 151 μm or less, 150 μm or less, 149 μm or less, 148 μm or less, 147 μm or less, 146 μm or less, 145 μm or less, 144 μm or less, 143 μm or less, 142 μm or less, or 141 μm or less, 140 μm or less, 139 μm or less, 138 μm or less, 137 μm or less, 136 μm or less, 135 μm or less, 134 μm or less, 133 μm or less, 132 μm or less,Or 131 μm or less, 130 μm or less, 129 μm or less, 128 μm or less, 127 μm or less, 126 μm or less, 125 μm or less, 124 μm or less, 123 μm or less, 122 μm or less, or 121 μm or less, more preferably 120 μm or less, 119 μm or less, 118 μm or less, 117 μm or less, 116 μm or less, 115 μm or less, 114 μm or less, 113 μm or less, 112 μm or less, or 111 μm or less, even more preferably 110 μm or less, 109 μm or less, 108 μm or less, 107 μm or less, 106 μm or less, 105 μm or less, 104 μm or less, 103 μm or less, 102 μm or less, or 101 μm or less, or 100 μm or less. This suppresses the shedding of the voids themselves from the sheet surface, thereby suppressing powder shedding. Therefore, the surface roughness of surface A is preferably 60-250 μm, 60-240 μm, 60-230 μm, 60-220 μm, 60-210 μm, 60-200 μm, 60-190 μm, 60-180 μm, 60-170 μm, 60-160 μm, 60-150 μm, 60-140 μm, 60-130 μm, 61-130 μm, 61-129 μm, 61-128 μm, 61-127 μm m, 61-126 μm, 62-125 μm, 62-124 μm, 62-123 μm, 62-122 μm, 62-121 μm, 63-120 μm, 63-119 μm, 63-118 μm, 63-117 μm, 63-116 μm, 64-115 μm, 64-114 μm, 64-113 μm, 64-112 μm, 64-111 μm, more preferably 65-110 μm, 66-109 μm, 66-108 μm, 66-107 μm, 67-106 μm, 67-105 μm, 68-104 μm, 68-103 μm, 69-102 μm, 69-101 μm, more preferably 70-250 μm, 70-240 μm, 70-230 μm, 70-220 μm, 70-210 μm, 70-200 μm, 70-190 μm, 70-180 μm, 70-170 μm, 70-160 μm, 70-150μm, 70-140μm, 70-130μm, 70-120μm, 70-110μm, 70-100μm, 71-100μm, 72-100μm, 73-100μm, 74-1 00 μm, 75-100 μm, 76-100 μm, 77-100 μm, 78-100 μm, 79-100 μm, 80-100 μm, 81-100 μm, 82-100 μm, 83-100 μm,The particle sizes are 84–100 μm, 85–100 μm, 86–100 μm, 87–100 μm, 88–100 μm, 89–100 μm, and 90–100 μm.

[0046] The lower limit of the surface roughness of surface B is preferably 20 μm or more, 21 μm or more, 22 μm or more, 23 μm or more, 24 μm or more, or 25 μm or more, more preferably 30 μm or more, 31 μm or more, 32 μm or more, 33 μm or more, 34 μm or more, 35 μm or more, 36 μm or more, 37 μm or more, 38 μm or more, or 39 μm or more, and even more preferably 40 μm or more. This allows for the capture of powder that falls off the sheet surface and suppresses powder shedding. The upper limit of the surface roughness of surface B is preferably 180 μm or less, 170 μm or less, 160 μm or less, 150 μm or less, 140 μm or less, 130 μm or less, 120 μm or less, 110 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, less than 60 μm, more preferably 55 μm or less, and even more preferably 50 μm or less. This suppresses the shedding of the voids themselves from the sheet surface and reduces powder shedding. Therefore, the surface roughness of surface B is preferably 20-180 μm, 20-170 μm, 20-160 μm, 20-150 μm, 20-140 μm, 20-130 μm, 20-120 μm, 20-110 μm, 20-100 μm, 20-90 μm, 20-80 μm, 20-70 μm, less than 20-60 μm, and 21-60 μm. Less than μm, 22 to less than 60 μm, 23 to less than 60 μm, 24 to less than 60 μm, 25 to less than 60 μm, 26 to less than 60 μm, 27 to less than 60 μm, 28 to less than 60 μm, 29 to less than 60 μm, more preferably 30 to 180 μm, 30 to 170 μm, 30 to 160 μm, 30 to 150 μm, 30 to 140 μm, 30 ~130 μm, 30-120 μm, 30-110 μm, 30-100 μm, 30-90 μm, 30-80 μm, 30-70 μm, 30-60 μm, 30-59 μm, 30-58 μm, 30-57 μm, 30-56 μm, 30-55 μm, 30-54 μm, 30-53 μm, 30-52 μm, 30-51 μm More preferably, the particle sizes are 30-50 μm, 31-50 μm, 32-50 μm, 33-50 μm, 34-50 μm, 35-50 μm, 36-50 μm, 37-50 μm, 38-50 μm, 39-50 μm, 40-50 μm, 40-49 μm, 40-48 μm, 40-47 μm, 40-46 μm, and 40-45 μm.

[0047] The surface roughness of surface A is preferably greater than the surface roughness of surface B, and the difference between the two (A-B) is usually 10 μm or more, 11 μm or more, 12 μm or more, 13 μm or more, 14 μm or more, 15 μm or more, 16 μm or more, 17 μm or more, 18 μm or more, or 19 μm or more, preferably 20 μm or more, 21 μm or more, 22 μm or more, 23 μm or more, 24 μm or more, 25 μm or more, 26 μm or more, 27 μm or more, 28 μm or more, or 29 μm or more, more preferably 30 μm or more, 31 μm or more, 32 μm or more, 33 μm or more, 34 μm or more, 35 μm or more, 36 μm or more, 37 μm or more, 38 μm or more, 39 μm or more, or 40 μm or more. There is no particular upper limit, but for example, it is 100 μm or less, 99 μm or less, 98 μm or less, 97 μm or less, 96 μm or less, 95 μm or less, 94 μm or less, 93 μm or less, 92 μm or less, 91 μm or less, 90 μm or less, 89 μm or less, 88 μm or less, 87 μm or less, 86 μm or less, 85 μm or less, 84 μm or less, 83 μm or less, 82 μm or less, 81 μm or less, and 80 μm or less.

[0048] The ratio of the surface roughness of surface A to the surface roughness of surface B (A / B) is preferably 1.3 or more, or 1.4 or more, more preferably 1.5 or more, 1.6 or more, 1.7 or more, 1.8 or more, 1.9 or more, 2.0 or more, 2.1 or more, or 2.2 or more, and even more preferably 2.3 or more, 2.4 or more, 2.5 or more, 2.6 or more, 2.7 or more, 2.8 or more, 2.9 or more, 3.0 or more, 3.1 or more, 3.2 or more, 3.3 or more, 3.4 or more, 3.5 or more, 3.6 or more, 3.7 or more, 3.8 or more, 3.9 or more, 4.0 or more, 4.1 or more, 4.2 or more, 4.3 or more, 4.4 or more, or 4.5 or more. The upper limit is usually 7.0 or less, 6.9 or less, 6.8 or less, 6.7 or less, or 6.6 or less, preferably 6.5 or less, 6.4 or less, 6.3 or less, 6.2 or less, or 6.1 or less, more preferably 6.0 or less.Therefore, preferably 1.3 or more, more preferably 1.3 to 7.0, 1.3 to 6.9, 1.3 to 6.8, 1.3 to 6.7, 1.3 to 6.6, 1.3 to 6.5, 1.3 to 6.0, 1.4 to 7.0, 1.4 to 6.9, 1.4 to 6.8, 1.4 to 6.7, 1.4 to 6.6, 1.5 to 7.0, 1.5 to 6.9, 1.5 to 6.8, 1.5 to 6.7, 1.5 to 6.6, 1.5 to 6.5, 1.5 to 6.4, 1.5-6.3, 1.5-6.2, 1.5-6.1, 1.5-6.0, 1.6-6.0, 1.7-6.0, 1.8-6.0, 1.9-6.0, 2.0-6.0, 2.1-6.0, 2.2-6.0, 2.3-7.0, 2.3-6.9, 2.3-6.8, 2.3-6.7, 2.3-6.6, 2.3-6.5, 2.3-6.4, 2.3-6.3, 2.3-6.2, 2.3-6.1, 2 3-6.0, 2.4-6.0, 2.5-6.0, 2.6-6.0, 2.7-7.0, 2.7-6.9, 2.7-6.8, 2.7-6.7, 2.7-6.6, 2.7-6.5, 2.7-6.4, 2.7-6.3, 2.7-6.2, 2.7-6.1, 2.7-6.0, 2.8-6.0, 2.9-6.0, 3.0-6.0, 3.1-6.0, 3.2-6.0, 3.3-6.0, 3.4-6. The ranges are 0, 3.5-6.0, 3.6-6.0, 3.7-6.0, 3.8-6.0, 3.9-6.0, 4.0-6.0, 4.1-6.0, 4.2-6.0, 4.3-6.0, 4.4-6.0, 4.5-7.0, 4.5-6.9, 4.5-6.8, 4.5-6.7, 4.5-6.6, 4.5-6.5, 4.5-6.4, 4.5-6.3, 4.5-6.2, 4.5-6.1, and 4.5-6.0.

[0049] Surface roughness Sa is the arithmetic mean height, and is the average of values ​​measured at any five locations in accordance with ISO 25178. The surface roughness Sa of surfaces A and B can be measured by observation using a microscope (for example, Keyence's "One-Shot 3D Shape Measuring Machine VR-6000"). A 15 cm x 15 cm measurement sheet is prepared, and 0.13 kg weights are placed on both ends at 3 cm intervals when viewed from the front to flatten the sheet surface. The value calculated using the surface roughness mode in the analysis program (program name: KEYENCE VR-6000 analysis application) of the image taken at 12x magnification in the central area (18 mm x 24 mm) can be used as the surface roughness Sa.

[0050] As explained above, by adjusting the surface properties of the two surfaces of the sheet when viewed from the horizontal, such as the number (distribution) of pores, the shape of the surface roughness, and the ratio thereof between the two surfaces, within a predetermined range, it is possible to form one surface (Surface A) with a relatively large number (distribution) of pores or a relatively large surface roughness, and the other surface (Surface B) with a relatively small number (distribution) of pores or a relatively small surface roughness.

[0051] By adjusting the surface properties of the insulation sheet in this way, the sheet's insulation performance can be maintained at a high level. The reason for this is presumed to be as follows.

[0052] As a result, on one side (surface A), even if the silica aerogel that was physically and chemically bonded to the fibers peels off when stress, vibration, etc. are applied to the silica aerogel sheet, the large number (distribution) of pores or the relatively large surface roughness makes it easy to capture the peeled silica aerogel, thus suppressing powder falling to the lower surface.

[0053] On the other side (surface B), since there is less stress and vibration applied to the silica aerogel sheet, the silica aerogel, which was physically and chemically bonded to the fibers, is less likely to peel off. In light of this, the number (distribution) of pores that cause powder shedding can be reduced, or the surface roughness can be made relatively smaller.

[0054] This suppresses powder shedding throughout the entire sheet, thus preventing a decrease in thermal insulation performance. Furthermore, the adhesion to films, etc., can be enhanced by having a relatively large number (distribution) of pores or a relatively large surface roughness on surface A, which has a predetermined shape and / or is formed of fibers. As a result, when stress, vibration, etc., are applied to the silica aerogel sheet, delamination between the film, etc. and the silica aerogel is suppressed, and consequently, powder shedding to the lower part can be suppressed.

[0055] 3. Method for manufacturing the thermal insulation sheet One method for manufacturing the thermal insulation sheet is to dissolve a silica material in a solvent to prepare a reaction solution (sol), then gel it, remove impurities such as the solvent and unreacted substances from the resulting wet gel, and then coat and dry it in a frame.

[0056] Examples of silica materials include methyltrimethoxysilane (MTMS), trimethylmethoxysilane (TMS), dimethyldimethoxysilane (DMS), trimethylethoxysilane, dimethyldiethoxysilane (DMDS), methyltriethoxysilane (MTES), ethyltriethoxysilane (ETES), diethyldiethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane (PhTES), hexamethyldisilazane, and hexaethyldisilazane.

[0057] Suitable solvents include, for example, water, methanol, ethanol, isopropanol, ethyl acetate, ethyl acetoethyl acetate, acetone, dichloromethane, and tetrahydrofuran. Of these, acidic aqueous solutions are preferred, and aqueous acetic acid solutions are more preferred. The reaction solution usually contains a hydrolyzable compound (e.g., urea), and may optionally contain a surfactant (e.g., aliphatic ammonium, alkylbenzylammonium). When preparing the sol, ice cooling and stirring may be performed as needed. Drying is usually done by supercritical drying, but atmospheric pressure drying is also acceptable. Supercritical drying is performed by repeating the process of exchanging the solvent (e.g., alcohol such as 2-propanol or ethanol) with a supercritical fluid (e.g., supercritical carbon dioxide) one or more times. Pressurization may be applied during drying as needed. This allows for uniform thickness of the sheet. The timing of fiber addition is preferably from the preparation of the reaction solution to the gelation stage (e.g., impregnating the fiber nonwoven fabric into the reaction solution one or more times) and / or the drying stage, and it is more preferable to impregnate the fiber into the reaction solution (sol). The method of gelation is not particularly limited and can be carried out by, for example, letting the reaction solution stand (e.g., letting it stand in a sealed device, preferably under heating in a sealed device (e.g., 50°C or higher, 60°C or higher)), adding a catalyst, or irradiating with ultraviolet light, etc., with standing being preferred. The porosity ratio and surface roughness of the sheet surface can also be adjusted by the gelation conditions and the fiber addition conditions (number of impregnations). In this specification, silica aerogel includes not only silica aerogel in the narrow sense (silica aerogel obtained by supercritical drying) but also silica aerogel obtained by other drying methods (e.g., xerogel (produced by drying at atmospheric pressure), cryogel (produced by freeze-drying), ambigel (produced by drying under ambient pressure)). At any stage of production, pores can be formed by, for example, a method such as puncturing. This allows for adjustment of the porosity ratio and surface roughness of the sheet surface.

[0058] Furthermore, hydrophobic treatment (for example, conversion of silica surface functional groups (e.g., hydroxyl groups) to hydrophobic trimethylsilyl groups) may be performed at any stage, and it is preferable to perform it before the drying process. Hydrophobic treatment can be performed by adding a hydrophobic agent such as a trimethylsilylating agent. When hydrophobic treatment is performed, the content of hydrophobic silica in the total aerosilica gel sheet obtained after the treatment is preferably 5% by mass or more, more preferably 7% by mass or more, with an upper limit of preferably 30% by mass or less, and more preferably 25% by mass or less. In addition, the mass ratio of hydrophobic silica to non-hydrophobic silica (hydrophobic / non-hydrophobic) is preferably 0.1 or more, more preferably 0.2 or more, with an upper limit of preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less.

[0059] 4. Other layer insulation sheets may form a laminate (insulation material) together with other components. Examples of other components include films, elastic layers, and adhesive layers.

[0060] 4.1 The film insulation material may further have a film that covers (seals) at least one surface (preferably only surface A, or both surfaces A and B). This further suppresses powder shedding. It is preferable to cover surface A or both surfaces. This further suppresses powder shedding more efficiently. This effect can be further demonstrated by positioning sheet surface A on the side of the cells that receives greater stress, and surface B on the side of the cells that receives less stress, vibration, etc.

[0061] Examples of polymer films include films made from polyimide, polycarbonate, PET, p-phenylene sulfide, polyetherimide, crosslinked polyethylene, flame-retardant chloroprene rubber, polyvinyldenium fluoride, rigid polyvinyl chloride (PVC), polybutylene terephthalate, PTFE, PFA, FEP, ETFE, flame-retardant PET, polystyrene, polyethersulfone, polyamideimide, polyacrylonitrile, polyethylene, polypropylene, polyamide, and the like.

[0062] 4.2 Adhesive Layer When other components are provided to the insulation material, an adhesive layer may be further included. The adhesive layer can be made of a material capable of bonding the insulation sheet to the other components. Examples of materials for the adhesive layer include epoxy resin, phenolic resin, acrylic resin, melamine resin, vinyl acetate resin, silicone resin, urethane resin, polyethylene, and polypropylene.

[0063] 4.3 Elastic Layer The elastic layer is a layer that relieves stress generated in the insulation sheet and applies a constant compressive load to the battery cells. In particular, covering surface A can further enhance the stress relief effect. This effect can be further demonstrated by positioning surface A, which is covered with the elastic layer, on the side of the cell that receives greater stress. The material of the elastic layer may be natural rubber or synthetic rubber, and is preferably mainly composed of polyisoprene, hydrogenated polyisoprene, polybutadiene, styrene-butadiene copolymer, isobutylene-isoprene copolymer, ethylene-propylene copolymer, ethylene-propylene-diene ternary copolymer (EPDM), or silicone. The shape of the elastic body is not particularly limited, and the shape of its surface is not particularly limited, but it is preferable to have protrusions such as irregularities on the surface that does not come into contact with the insulation sheet (for example, the surface that comes into contact with the cells). This can further enhance the powder fall prevention effect by relieving stress on the sheet.

[0064] 4.4 Lamination Method The method of laminating other layers onto the sheet is not particularly limited, and includes methods of laminating other layers necessary for the insulation material sheet. The lamination process can be, for example, by applying an adhesive to at least one surface of the insulation material sheet (using equipment and tools such as a blade coater, bar coater, die coater, comma coater®, roll coater, brush, etc., as needed), drying (for example, 80 to 180°C, several minutes to several tens of minutes), or by bonding pre-prepared other layers via an adhesive or adhesive layer. In the case of a film, for example, a method of attaching the film to the sheet surface with an adhesive, etc., or a method of housing it in a bag-shaped film can be used.

[0065] 5. Applications of the Insulation Sheet The insulation sheet can exhibit a good balance of both insulation and thermal properties. Therefore, it can be used as an insulation sheet between automotive battery cells. When used between automotive battery cells, the sheet can be placed between the cells.

[0066] It is preferable to position surface A of the sheet facing the side that experiences greater stress, such as the side where the battery expands and generates stress, the vibration source side, or the side with greater motor vibration. This effectively suppresses powder shedding while maintaining adhesion, while surface B maintains its heat insulation and adhesion properties, thus providing overall heat insulation performance.

[0067] The following examples and comparative examples are provided to illustrate the features of one or more embodiments, but the examples and comparative examples should not be construed as limiting the scope of the embodiments of the present invention, nor should the comparative examples be construed as being outside the scope of the embodiments of the present invention. Furthermore, these embodiments are not limited to the specific details described in the examples and comparative examples.

[0068] [Method for producing glass fiber reinforced aerogel sheets] - Preparation of glass fiber reinforced aerogel sheet (1) - 1.00 g of cetyltrimethylammonium bromide (also known as hexadecyltrimethylammonium bromide: manufactured by Nacalai Tesque Co., Ltd., hereinafter abbreviated as "CTAB") as a cationic surfactant was dissolved in 10.00 g of a 0.01 mol / L aqueous acetic acid solution, which is an acidic aqueous solution. Then, 0.50 g of urea (manufactured by Nacalai Tesque Co., Ltd.) was added as a hydrolyzable compound and dissolved. 5.0 mL of methyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., LS-530 (specific gravity: 0.95), hereinafter abbreviated as "MTMS") as a silica material was added to this acidic aqueous solution. The mixture was then stirred and mixed under ice cooling for 30 minutes to allow the hydrolysis reaction of MTMS to occur and produce a sol. The sol was then impregnated into a perforated glass fiber nonwoven fabric (Nitigura Mat, MNA-300-1000-30m, 3mm thick, manufactured by Nippon Glass Fiber Industry Co., Ltd.) placed on top of a polypropylene film (50μm thick). It was left to stand in a sealed container at 60°C for 3 hours to gel. The gel was then matured by leaving it to stand in a sealed container for another 96 hours. After removing it from the sealed container, the solvent was replaced by immersion in 2-propanol. This procedure was performed twice: the first time at 60°C for 24 hours, and the second time at 60°C for 48 hours with fresh 2-propanol.

[0069] Next, the aerogel sheets were supercritically dried under the following conditions: A 400 mL autoclave was filled with 2-propanol, and the aerogel sheets, after solvent replacement, were placed inside. The lid was closed, and liquefied carbon dioxide was introduced to create a pressure of approximately 882 N / cm². 2 (approx. 90 kgf / cm 2 While maintaining the position, the first liquid phase replacement operation was performed (time required: 1.5 hours).

[0070] After the first liquid phase displacement was complete, the valve was closed and the pressure was maintained while liquefied carbon dioxide was diffused into the gel over 17.5 hours. Subsequently, the pressure was increased to approximately 882 N / cm², similar to the first liquid phase displacement. 2 (approx. 90 kgf / cm 2While maintaining the pressure, a second liquid phase displacement was performed (time required: 1 hour). After the second liquid phase displacement was completed, the valve was closed and the pressure was maintained as in the first time, and liquefied carbon dioxide was diffused into the gel over 5 hours. After that, as in the first liquid phase displacement, approximately 882 N / cm was used. 2 (approx. 90 kgf / cm 2 While maintaining the condition, a third liquid phase displacement was performed in the same manner (time required: 0.75 hours).

[0071] After the third liquid phase displacement was complete, the valve was closed and the autoclave was heated from room temperature to 80°C over 1.5 hours. After reaching 80°C, the pressure was 4.9 N / cm². 2 ・min(0.5kgf / cm 2 The pressure was reduced at a rate of min(0). After reaching atmospheric pressure, the autoclave was cooled to room temperature over 2 hours. Then, the autoclave was opened, the aerogel sheet was removed, and the supercritical drying process was completed. This produced glass fiber reinforced aerogel sheet 1 (3 mm thick). The side in contact with the film is side B.

[0072] - Preparation of glass fiber reinforced aerogel sheet (2) - Glass fiber reinforced aerogel sheet (2) was prepared in the same manner as the preparation of sheet (1), except that the generated sol was heated at 60°C for 0.5 hours, then impregnated into a glass fiber nonwoven fabric and left to gel in a sealed container at 60°C for 2.5 hours.

[0073] - Preparation of glass fiber reinforced aerogel sheet (3) - Glass fiber reinforced aerogel sheet (3) was prepared in the same manner as the preparation of sheet (1), except that the generated sol was heated at 60°C for 1 hour, then impregnated into a glass fiber nonwoven fabric and left to gel in a sealed container at 60°C for 2 hours.

[0074] - Preparation of glass fiber reinforced aerogel sheet (4) - Glass fiber reinforced aerogel sheet (4) was prepared in the same manner as the preparation of sheet (2), except that a nonwoven fabric impregnated with sol was sandwiched between polypropylene films, squeegeeed from side A, and then the polypropylene film on side A was peeled off.

[0075] - Preparation of glass fiber reinforced aerogel sheet (5) - Glass fiber reinforced aerogel sheet (5) was prepared in the same manner as the preparation of sheet (2), except that holes were punched in the glass fiber nonwoven fabric from the B side.

[0076] - Preparation of glass fiber reinforced aerogel sheet (6) - A glass fiber reinforced aerogel sheet (6) was prepared in the same manner as the preparation of sheet (1), except that a nonwoven fabric impregnated with sol was left to stand in a sealed container at 60°C for 1 hour, then removed from the sealed container and impregnated with sol again.

[0077] - Preparation of glass fiber reinforced aerogel sheet (7) - Glass fiber reinforced aerogel sheet 7 was prepared in the same manner as the preparation of sheet (6), except that a nonwoven fabric with a napped surface A was used.

[0078] - A glass fiber reinforced aerogel sheet (8) was prepared in the same manner as the preparation method for sheet (1), except that a nonwoven fabric impregnated with the preparation sol was sandwiched between polypropylene films, squeegeeed from side A, and then the polypropylene film on side A was peeled off.

[0079] - Preparation of glass fiber reinforced aerogel sheet (9) - Except for using a nonwoven fabric with a napped surface on side B, the glass fiber reinforced aerogel sheet (9) was prepared in the same manner as the preparation of sheet (8).

[0080] - Preparation of glass fiber reinforced aerogel sheet (10) - A glass fiber reinforced aerogel sheet (10) was prepared in the same manner as the preparation of sheet (5), except that a nonwoven fabric impregnated with sol was left to stand in a sealed container at 60°C for 1 hour, then removed from the sealed container and impregnated with sol again.

[0081] - Preparation of glass fiber reinforced aerogel sheet (11) - Glass fiber reinforced aerogel sheet (11) was prepared in the same manner as the preparation of sheet (1), except that the generated sol was heated at 60°C for about 0.1 hours, impregnated into a glass fiber nonwoven fabric, and allowed to stand in a sealed container at 60°C for about 2.9 hours to gel.

[0082] - Preparation of glass fiber reinforced aerogel sheet (12) - Glass fiber reinforced aerogel sheet (11) was prepared in the same manner as the preparation of sheet (1), except that the generated sol was heated at 60°C for about 0.7 hours, impregnated into a glass fiber nonwoven fabric, and allowed to stand in a sealed container at 60°C for about 2.3 hours to gel.

[0083] - Preparation of glass fiber reinforced aerogel sheets (13) and (14) - Glass fiber reinforced aerogel sheets (13) and (14) were prepared in the same manner as the preparation of sheet (4), except that holes were punched in the glass fiber nonwoven fabric from the B side.

[0084] - Preparation of glass fiber reinforced aerogel sheet (15) - The glass fiber reinforced aerogel sheet (15) was prepared in the same manner as the preparation of sheet (1), except that the generated sol was heated at 60°C for 2 hours, then impregnated into a glass fiber nonwoven fabric and left to stand in a sealed container at 60°C for 1 hour to gel.

[0085] - Preparation of glass fiber reinforced aerogel sheet (16) - The generated sol was impregnated into a glass fiber nonwoven fabric (Nitto Boseki, Chopped Strand Mat, MC-600A, 1 mm thick) with the A-side and B-sides of the glass fiber nonwoven fabric (Nitto Boseki, Chopped Strand Mat, MC-600A, 1 mm thick) which was layered to a thickness of 3 mm, and then left to gel in a sealed container at 60°C for 3 hours. The glass fiber reinforced aerogel sheet (16) was prepared in the same manner as the preparation of sheet (1).

[0086] - Preparation of glass fiber reinforced aerogel sheet (17) - The glass fiber reinforced aerogel sheet (17) of Comparative Example 3 was prepared in the same manner as the preparation of sheet (4), except that the generated sol was impregnated into a glass fiber nonwoven fabric (Nitto Boseki, chopped strand mat, MC-600A, 1 mm thick) layered to a thickness of 3 mm, sandwiched between polypropylene films, squeegeeed from side A, the film on side A was peeled off to impregnate with the sol, and then sandwiched again between polypropylene films.

[0087] - Preparation of glass fiber reinforced aerogel sheet (18) A glass fiber reinforced aerogel sheet (18) was prepared in the same manner as the preparation of sheet (15), except that the A-side of the generated sol was made fluffy.

[0088] - Preparation of glass fiber reinforced aerogel sheet (19) - Glass fiber reinforced aerogel sheet (19) was prepared in the same manner as the preparation of sheet (2), except that the generated sol was impregnated into a glass fiber nonwoven fabric (Nitto Boseki, chopped strand mat, MC-600A, 1 mm thick) layered to a thickness of 3 mm.

[0089] - Preparation of glass fiber reinforced aerogel sheet (20) - Except for using Nitigura mat, MNA-800-1000-20m, with a thickness of 8 mm as the glass fiber nonwoven fabric, a glass fiber reinforced aerogel sheet (20) was prepared in the same manner as the preparation of sheet (2).

[0090] - Preparation of glass fiber reinforced aerogel sheet (21) - Except for using Nitigura mat, MNA-800-1000-20m, with a thickness of 8 mm as the glass fiber nonwoven fabric, a glass fiber reinforced aerogel sheet (21) was prepared in the same manner as the preparation of sheet (3).

[0091] - Preparation of glass fiber reinforced aerogel sheet (22) - The glass fiber reinforced aerogel sheet (22) was prepared in the same manner as the sheet (20), except that the A-side was made fluffy.

[0092] - Preparation of glass fiber reinforced aerogel sheet (23) - The glass fiber reinforced aerogel sheet (23) was prepared in the same manner as the sheet (20), except that the B-side was made fluffy.

[0093] [Test Method for Physical Properties] - Evaluation Method for "Powder Shedding" - (1) A sample was prepared by covering a measurement sheet (prepared by cutting it to a surface of 5 x 5 cm) with a PET film (thickness 50 μm) and adhering it to a rubber sheet. The rubber sheet has a structure in which multiple ridge units (in cross-section, the base has a width of 10.86 mm, a height of approximately 7 mm, and consists of a convex part that extends in the width direction with a 60° taper and a concave part around it, with a width of approximately 20.5 mm including the concave and convex parts) are connected. The measurement sheet and the rubber sheet were positioned so that the concave part of the ridge was on the A-side. In a vibrator equipped with a jig consisting of a pair of metal plates and a powder receiver, the sample was sandwiched between the metal plates so that its surface was approximately vertical (upright), and the sample was compressed to 50% and fixed, and vibrated at 3 G / 15 Hz x 800,000 times. (2) After that, the film was peeled off with the sample standing in a nearly horizontal position, and the amount of aerogel that fell off each of surfaces A and B was visually confirmed. In evaluating the powder shedding properties of sheets (1) to (19), the amount of aerogel that fell off each surface A of these sheets was compared with the amount of aerogel that fell off surface A of sheet (15), and for surface B, it was compared with the amount of aerogel that fell off surface B of sheet (16) to determine which of the evaluation criteria in (3) it met. In evaluating the powder shedding properties of sheets (20) to (23), the amount of aerogel that fell off each surface A of these sheets was compared with the amount of aerogel that fell off surface A of sheet (23), and the amount of aerogel that fell off each surface B of these sheets was compared with the amount of aerogel that fell off surface B of sheet (23), to determine which of the evaluation criteria in (3) it met. (3) Evaluation Criteria (For sheets (1) to (19), surface A is evaluated based on surface A of sheet (15), and surface B is evaluated based on surface B of sheet (16); for sheets (20) to (23), surface A and surface B of sheet (23) are evaluated based on each of the following criteria) Aerogel fall rate is 1 / 3 or less of the standard... A Aerogel fall rate is more than 1 / 3 but 1 / 2 or less of the standard... B Aerogel fall rate is more than 1 / 2 of the standard... C Samples (15), (16), and (23) are the criteria for evaluating powder shedding properties, and therefore the evaluation results for powder shedding properties and the overall evaluation results for these sheets are not entered in the table below.

[0094] - Evaluation Method for "Adhesion" - Samples were prepared by attaching adhesive tape (manufactured by Sekisui Chemical Co., Ltd., 0.15 mm thick, green) to sides A and B of an insulating sheet. A 180° peel test (compliant with JIS Z 0237:2009, tensile speed 300 mm / min) was performed at the interface between the insulating sheet and the adhesive tape using a benchtop tensile testing machine (Minebeva "AGS-1kNG"), and the peel force was measured and defined as the interlayer adhesion force. <Criteria for Side A> Samples with a tensile load of 5 N / 25 mm or more were classified as having good adhesion "A", samples with a tensile load of 0.5 to 5 N / 25 mm were classified as having good adhesion "B", and samples with a tensile load of less than 0.5 N / 25 mm were classified as having poor adhesion "C". <Criteria for Side B> Samples with a tensile load of 0.5 N / 25 mm or more were classified as having good adhesion "A", and samples with a tensile load of less than 0.5 N / 25 mm were classified as having poor adhesion "C".

[0095] - Evaluation Method for "Overall Evaluation" - The overall evaluation was conducted based on the following criteria: If all are A...++ (very good) If one or both are A and B...+ (good) If even one is a C...- (poor)

[0096] [Test Method for Sheet Surface Properties] -Surface Roughness- Surface roughness Sa was measured using the following method. The sheet was cut into 15 cm x 15 cm pieces, and 0.13 kg weights were placed on both ends at 3 cm intervals when viewed from the front to flatten the sheet surface. The average value of the values ​​calculated for five arbitrary locations in the surface roughness mode of the analysis program (program name: KEYENCE VR-6000 analysis application) was defined as surface roughness Sa. Images were taken at 12x magnification using a microscope (KEYENCE "One-Shot 3D Shape Measuring Machine VR-6000") within the central area of ​​the sheet measurement surface (18 mm x 24 mm).

[0097] - Number of voids per unit area - The number of voids was measured using the following method. The sheet was cut into 15 cm x 15 cm sections, and five arbitrary locations on the sheet surface were photographed using a digital camera (Canon PowerShot SX720 HS). Using image processing software (ImageJ), a 2 cm x 2 cm (200 pixels x 200 pixels) image was extracted from the captured images, and the area with a brightness of 125 or less was binarized as a void using ImageJ's binarization function. Next, particles smaller than 4 pixels² were removed as noise using ImageJ's particle analysis function, and the number of voids was counted, and the average value for the five locations was calculated. Note that voids may be covered by glass fibers, etc., and voids that penetrate from the surface to the back are also included. Furthermore, the diameter of voids counted under the above conditions is larger than 0.2 mm.

[0098]

[0099]

[0100]

[0101]

[0102]

[0103]

[0104]

[0105]

[0106]

[0107]

[0108] [Footnote to the table] In the table, the number of voids refers to the number of voids observed in a 2 cm × 2 cm (200 pixels × 200 pixels) area, and 1 m ２ The number of items per unit (indicated in parentheses) is also shown.

[0109] Sheets (1) to (14) with a void ratio of 1.3 or higher all received an overall evaluation of + or ++. Additionally, sheets (18) and (19) with a surface roughness difference of 30 or more also received an overall evaluation of +.

[0110] The following observations were made regarding the number of pores on surface A. Comparing sheets (1) and (2), sheet (1) received a B rating for powder shedding on surface A, while sheet (2), which had a relatively small number of pores on surface A, received an A rating. Furthermore, comparing sheets (3) and (10) with sheet (2), sheets (3) and (10) received a B rating for powder shedding, while sheet (2), which had a relatively large number of pores on surface A, received an A rating. These results indicate that a smaller number of pores on surface A tends to suppress the shedding of the pores themselves, while a larger number of pores tends to trap powder more easily.

[0111] The following observations were made regarding the number of voids on surface B. Comparing sheets (4) and (2), sheet (4) received a B rating for powder shedding on surface B, while sheet (2), which had a relatively large number of voids on surface B, received an A rating. Similarly, comparing sheets (5) and (10) with (2), sheets (5) and (10) received a B rating for powder shedding on surface B, while sheet (2), which had a relatively large number of voids on surface B, received an A rating. These results indicate that, similar to surface A, a smaller number of voids on surface B tends to suppress the shedding of the voids themselves, while a larger number of voids tends to trap powder more easily.

[0112] For sheets (1) to (14) and (18) to (22), where the roughness ratio was 1.3 or higher, the overall evaluation was + or ++. The surface roughness of surface A was examined as follows: Comparing sheet (6) and (2), sheet (6) received a B rating for powder shedding on surface A, while sheet (2), with relatively high surface roughness of surface A, received an A rating. Comparing sheet (7) and (2), sheet (7) received a B rating for powder shedding, while sheet (2), with relatively low surface roughness of surface A, received an A rating. Furthermore, comparing sheets (20) and (21) with (22), sheet (22) received a B rating for powder shedding, while sheets (20) and (21), with relatively low surface roughness of surface A, received an A rating. These results indicate that a higher surface roughness of surface A tends to trap powder through voids, while a lower surface roughness tends to suppress the shedding of the voids themselves.

[0113] The surface roughness of surface B was examined as follows: Comparing sheets (8) and (2), the powder shedding performance of surface B on sheet (8) was rated B, while on sheet (2), where surface B had a relatively large surface roughness, it was rated A. Furthermore, comparing sheets (9) and (2), the powder shedding performance of sheet (9) was rated B, while on sheet (2), where surface A had a relatively small surface roughness, it was rated A. These results indicate that, similar to surface A, for surface B, a larger surface roughness of surface B tends to trap powder more effectively due to the voids, while a smaller surface roughness tends to suppress the shedding of the voids themselves.

[0114] The above embodiments illustrate specific embodiments of the present invention. However, these embodiments are merely illustrative; therefore, they should not be interpreted restrictively. Various modifications that will be obvious to those skilled in the art are intended to be within the scope of these embodiments.

[0115] The above results demonstrate that the thermal insulation sheet according to this embodiment can exhibit good thermal insulation properties and may be useful as thermal insulation material between automotive battery cells.

Claims

1. An electric vehicle battery cell insulation sheet comprising silica aerogel and fibers, having multiple voids on one surface and the other surface in the thickness direction, wherein the ratio of the number of voids on one surface to the number of voids on the other surface is 1.3 or more.

2. The number of voids on one of the aforementioned surfaces is 25,000 to 225,000 per square meter. ２ The sheet according to claim 1.

3. The number of voids on the other surface is 10,000 to 50,000 per square meter. ２ The sheet according to claim 1 or 2.

4. The sheet according to any one of claims 1 to 3, wherein the difference between the surface roughness Sa of one surface and the surface roughness Sa of the other surface is 10 μm or more.

5. The sheet according to any one of claims 1 to 4, wherein the difference between the surface roughness Sa of one surface and the surface roughness Sa of the other surface is 30 μm or more.

6. The sheet according to any one of claims 1 to 5, wherein the surface roughness Sa of one of the surfaces is 60 μm or more.

7. The sheet according to any one of claims 1 to 6, wherein the surface roughness Sa of one of the surfaces is 80 to 250 μm.

8. The sheet according to any one of claims 1 to 7, wherein the surface roughness Sa of the other surface is 180 or less.

9. The sheet according to any one of claims 1 to 8, wherein the surface roughness Sa of the other surface is 30 to 180 μm.

10. The sheet according to any one of claims 1 to 9, further comprising a film covering at least a portion of one surface and the other surface.

11. The sheet according to any one of claims 1 to 10, further comprising an elastic layer laminated on at least a portion of one surface and the other surface.

12. The sheet according to any one of claims 1 to 11, further comprising a film covering one surface and the other surface, and an elastic layer laminated on the one surface or the other surface via the film.

13. An electric vehicle battery cell insulation sheet comprising silica aerogel and fibers, having multiple irregularities on one surface and the other surface in the thickness direction, and having a ratio of the surface roughness of one surface to the surface roughness of the other surface of 1.3 or more.

14. The number of voids on one of the aforementioned surfaces is 100,000 to 150,000 per square meter. ２ The surface roughness Sa of the pores on one surface is 80 to 100 μm, and the number of pores on the other surface is 20,000 to 30,000 per square meter. ２ The sheet according to claim 1, wherein the surface roughness Sa of the voids on the other surface is 30 to 50 μm.

15. The sheet according to claim 13, wherein the ratio of the surface roughness of one surface to the surface roughness of the other surface is 2.3 to 4.4, and the difference between the surface roughness of one surface and the surface roughness of the other surface is 30 to 100 μm.

Images