Battery protective sheet and battery module

Abstract

To provide a battery protection sheet which has high heat insulation performance in addition to mechanical impact resistance, and to provide a battery pack module.SOLUTION: A battery protection sheet 1 includes: a sheet forming sheet layer 10 containing first inorganic fibers; and a cross layer 20 formed by second inorganic fibers. Further, a battery pack module comprises: multiple battery packs; a case for housing the battery packs; and the battery protection sheet bonded to the inner side of the case.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery protective sheet and a battery module. [Background technology]

[0002] In recent years, secondary batteries that can be charged and discharged using non-aqueous electrolytes have become widely used in automobiles, portable communication devices, laptops, and other applications due to their high energy density and high safety, as they can intercalate active metals into the active material.

[0003] Although such secondary batteries are highly safe under normal use, various accidents are anticipated, such as short circuits caused by external penetration by metal pieces such as nails. Furthermore, secondary batteries use organic electrolyte, and in recent years, many cells have been stacked to increase capacity, which means that the amount of organic electrolyte increases, making it extremely important to ensure safety.

[0004] Patent Document 1 describes a secondary battery that includes impact-resistant materials such as aramid fibers, glass fibers, UHMWPE fibers, and polybenzoxazole fibers in order to improve safety. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2013-545235 Summary of the Invention [Problem to be solved by the invention]

[0006] The invention described above is intended to prevent damage to the secondary battery itself, but once damage occurs and heat is generated, the heat is transferred to the outside of the heated secondary battery, damaging the case that covers the secondary battery, and further promoting heat generation due to a reaction between the organic electrolyte of the secondary battery and the outside air.

[0007] In view of the above problems, an object of the present invention is to provide a battery protective sheet and a battery module that have high thermal insulation properties in addition to mechanical impact resistance. [Means for solving the problem]

[0008] The battery protective sheet of the present invention for solving the above problems comprises: (1) It has a paper-made sheet layer containing a first inorganic fiber and a cloth layer made of a second inorganic fiber.

[0009] The battery protective sheet of the present invention comprises a paper-made sheet layer containing a first inorganic fiber and a cloth layer made of a second inorganic fiber, and thus the paper-made sheet layer has high thermal insulation properties, while the cloth layer has mechanical impact resistance, thereby combining thermal insulation and impact resistance. That is, the first inorganic fibers are short fibers such as chopped fibers or milled fibers so that they can be made into paper and act to block heat transfer, while the second inorganic fibers are continuous fibers so that they can be formed into a cloth and ensure high strength by taking advantage of their long fiber length.

[0010] (2) The first inorganic fibers have an average fiber length of 0.5 to 10 mm.

[0011] The first inorganic fibers have an average fiber length of 0.5 mm or more, so that they intertwine with each other after being made into a sheet, resulting in a sheet having a certain strength as a papermaking product. Also, the average fiber length is 10 mm or less, so that the distance over which heat is transferred by each inorganic fiber is short, ensuring high thermal insulation.

[0012] (3) The papermaking sheet layer further contains inorganic particles.

[0013] The papermaking sheet layer contains inorganic particles, which shortens the distance that each particle must travel to transfer heat, resulting in high thermal resistance at the contact points, ensuring high thermal insulation. Furthermore, the use of inorganic particles with high refractive indexes, such as silica nanoparticles or titania particles, facilitates surface reflection of light, providing a high shielding effect against radiant heat, especially in high-temperature regions.

[0014] (4) The papermaking sheet layer further contains a binder.

[0015] The binder prevents the first inorganic fibers and inorganic particles from falling off from the papermaking sheet layer, and the strength can be maintained.

[0016] The binder can be selected from inorganic binders such as alumina sol and silica sol, or organic binders such as cationized starch and acrylic resin. These binders are used as raw materials for the papermaking sheet in the form of an aqueous solution, and when dried, they remain at the contact points of the first inorganic fibers and inorganic particles to bind them together.

[0017] (5) An intermediate layer in which the first inorganic fibers penetrate into the cloth layer is provided at the interface region between the cloth layer and the paper-made sheet layer.

[0018] The cloth layer has an intermediate layer penetrated by first inorganic fibers, ensuring high peel strength. Furthermore, the cloth layer and the papermaking sheet layer are firmly bonded together, making them less likely to peel off even when subjected to repeated vibrations or external compression, and less likely to fall off even from the side or top of the inner wall of the battery case. Furthermore, because the cloth layer and the papermaking sheet layer are both inorganic and directly bonded without an organic intervening material, they can be used stably without peeling off even when exposed to high temperatures.

[0019] (6) The sheet layer has a thickness of 0.1 to 5 mm.

[0020] A thickness of 0.1 mm or more of the paper-made sheet layer can provide high heat insulation to the battery protective sheet. A thickness of 5 mm or less of the paper-made sheet layer can ensure flexibility and allow the sheet to be bent into a predetermined shape for use. A thickness of 0.2 to 1.1 mm is preferable.

[0021] (7) The cloth layer has a thickness of 0.1 to 5 mm.

[0022] A cloth layer having a thickness of 0.1 mm or more can impart high mechanical strength to the battery protective sheet. A cloth layer having a thickness of 5 mm or less can ensure flexibility and can be bent into a predetermined shape for use. A thickness of 0.3 to 1.4 mm is preferable.

[0023] (8) A first coating layer is provided on the outside of the papermaking sheet layer.

[0024] When the first coating layer is provided on the outside of the sheet layer, powder can be prevented from falling off from the sheet layer.

[0025] (9) The first cover layer and the papermaking sheet layer are bonded together by a first bonding layer made of an adhesive or a thermoplastic resin.

[0026] When the first coating layer is fixed by the bonding layer, it can be made difficult to peel off even when an external force such as friction is applied.

[0027] (10) A second coating layer is provided on the outside of the cloth layer.

[0028] By providing the second covering layer on the outside of the cloth layer, the edges of the cloth layer are less likely to fray even when external frictional force is applied to them.

[0029] (11) The second cover layer and the cloth layer are bonded together by a second bonding layer made of an adhesive or a thermoplastic resin.

[0030] When the second covering layer is fixed by the second bonding layer, the edges are less likely to curl up, and the cloth layer is less likely to come undone even when an external force such as friction is applied.

[0031] Further, the battery module of the present invention for solving the above-mentioned problems comprises: (12) A battery pack includes a plurality of assembled batteries, a case for accommodating the assembled batteries, and the battery protective sheet according to any one of (1) to (11) attached to the inside of the case.

[0032] The battery module of the present invention has a battery protective sheet with excellent mechanical impact resistance and heat resistance on the inside of the case that houses the battery assembly, which protects the battery from external damage caused by protrusions, suppresses heat transfer to the outside of the case in the event of a battery abnormality, prevents damage to the case, and prevents combustible materials from coming into contact with the outside air and combusting violently, resulting in excellent safety. [Effects of the Invention]

[0033] According to the present invention, a battery protective sheet is provided which is composed of a paper-made sheet layer containing a first inorganic fiber and a cloth layer made of a second inorganic fiber, and therefore the cloth layer has mechanical impact resistance and the paper-made sheet layer has high thermal insulation properties, thereby providing both impact resistance and thermal insulation properties.

[0034] Furthermore, according to the present invention, a battery protective sheet with excellent mechanical impact resistance and heat resistance is provided on the inside of the case that houses the assembled battery, thereby protecting the battery from external damage caused by protrusions, suppressing heat transfer to the outside of the case in the event of a battery abnormality, preventing damage to the case, and preventing combustible materials from coming into contact with the outside air and combusting violently, thereby providing an assembled battery module with excellent safety. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 shows a cross-sectional view of a battery protection sheet in accordance with a first embodiment of the present invention. [Figure 2] FIG. 2 is a partial enlarged view of part A in FIG. [Figure 3] FIG. 3 is a partial enlarged view of part B in FIG. [Figure 4] FIG. 4 shows a cross-sectional view of a battery protective sheet in accordance with a second embodiment of the present invention. [Figure 5] FIG. 5 shows a cross-sectional view of a battery protective sheet according to a third embodiment of the present invention. [Figure 6] FIG. 6 shows a cross-sectional view of a battery module using the battery protective sheet of the present invention. [Figure 7]FIG. 7 is an explanatory diagram showing a method for a shear test of a battery protective sheet. DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention will now be described in detail with reference to the drawings.

[0037] <Battery protection sheet> [Embodiment 1] As shown in FIG. 1, the battery protective sheet 1 has a paper-made sheet layer 10 and a cloth layer 20 .

[0038] (1. Papermaking sheet layer) FIG. 2 is an enlarged schematic view of part A in FIG. 1, in which the papermaking sheet layer 10 contains first inorganic fibers 11.

[0039] (1-1. First inorganic fiber) Chopped fibers or milled fibers are preferred for the first inorganic fibers 11 for ease of papermaking. Also, the first inorganic fibers 11 are preferably those with excellent heat resistance, such as ceramic fibers such as silica fibers, alumina fibers, alumina silicate fibers, and zirconia fibers, and glass fibers. These inorganic fibers may be used alone or in combination of two or more.

[0040] When a mixture is used, it is preferable that one of the inorganic fibers is an amorphous fiber and the other is at least one selected from amorphous fibers having a higher glass transition temperature than the other fiber and crystalline fibers. In such a case, when the battery protective sheet 1 is exposed to high temperatures, the surface of one of the inorganic fibers softens relatively quickly and binds the other inorganic fiber and inorganic particles 15 described below, thereby improving the mechanical strength.

[0041] The average fiber length of the first inorganic fibers 11 is preferably 0.5 to 10 mm. The papermaking sheet layer 10 is obtained by papermaking a suspension containing the first inorganic fibers 11. Because the average fiber length is 0.5 mm or more, the fibers are entangled with each other after papermaking, and the papermaking body has a certain strength. Furthermore, because the average fiber length of the first inorganic fibers 11 is 10 mm or less, the distance over which heat is transferred by a single inorganic fiber is short, ensuring high thermal insulation.

[0042] (1-2.Inorganic particles) The papermaking sheet layer 10 may further contain inorganic particles 15. Each inorganic particle 15 has a short heat transfer distance and a high thermal resistance at its contact point, ensuring high thermal insulation.

[0043] The material of the inorganic particles 15 is not particularly limited, but from the viewpoint of the heat transfer suppression effect, it is preferable that the inorganic particles 15 consist of at least one kind selected from oxide particles, carbide particles, nitride particles, and inorganic hydrate particles, and it is more preferable that the inorganic particles 15 contain oxide particles.

[0044] The shape and size of the inorganic particles 15 are not particularly limited, but preferably contain at least one type selected from nanoparticles, hollow particles, and porous particles, and more preferably contain nanoparticles.

[0045] Furthermore, the inorganic particles 15 may be a single inorganic particle or a combination of two or more inorganic particles. The combined use of two or more inorganic particles with different heat transfer suppression effects allows the heat generating element to be cooled in multiple stages, enabling the endothermic effect to be exerted over a wider temperature range. It is also preferable to use a mixture of large-diameter particles and small-diameter particles. When small-diameter particles fill the gaps between the large-diameter particles, a denser structure is formed, improving the heat transfer suppression effect.

[0046] When the average secondary particle diameter of the inorganic particles 15 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 15 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.

[0047] An example of the material or shape of particles that can be used as the inorganic particles 15 will be described in detail below.

[0048] (1-2-1. Oxide particles) Oxide particles have a high refractive index and a strong effect of diffusely reflecting light. Therefore, using oxide particles as inorganic particles can suppress radiant heat transfer, particularly in high-temperature regions such as those involving abnormal heat generation. The oxide particles can be at least one selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide, and alumina. That is, among the above 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 diffusely reflecting light and blocking radiant heat in high-temperature regions of 500°C or higher. Therefore, it is most preferable to use at least one of silica and titania as the oxide particles.

[0049] Because the particle size of the oxide particles can affect the effect of reflecting radiant heat, limiting the average primary particle size to a predetermined range can achieve even higher thermal insulation. That is, when the average primary particle size of the oxide particles is 0.001 μm or more, it is sufficiently larger than the wavelength of light that contributes to heating and efficiently diffuses light, thereby suppressing radiant heat transfer within the battery protective sheet 1 at high temperatures of 500°C or higher, thereby 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 number of contact points between particles do not increase even when compressed, making it difficult to form paths for conductive heat transfer. This can reduce the impact on thermal insulation, especially in normal temperature ranges where conductive heat transfer is dominant.

[0050] When two or more types of oxide particles are used, it is also preferable to use a mixture of large-diameter particles and small-diameter particles (nanoparticles). In this case, the average primary particle size of the large-diameter particles is more preferably 1 μm or more and 50 μm or less, even more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.

[0051] 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.

[0052] 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 a low density, which suppresses conductive heat transfer. Furthermore, when nanoparticles are used as inorganic particles, the finely dispersed voids provide excellent heat insulation, suppressing convective heat transfer. Therefore, the use of nanoparticles is preferred because they can suppress heat transfer between adjacent nanoparticles during use in the normal room temperature range.

[0053] In the present invention, it is preferable that at least one of oxide particles, carbide particles, nitride particles, and inorganic hydrate particles selected as the inorganic particles 15 is a nanoparticle.

[0054] When nanoparticles are used as the inorganic particles 15, 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 larger particle size are used. Furthermore, commonly available silica nanoparticles have a bulk density of 0.1 g / cm. 3 Therefore, even if a large compressive stress is applied to the battery protective sheet 1, the size (area) and number of contact points between the silica nanoparticles do not increase significantly, and heat insulation properties can be maintained. Therefore, it is preferable to use silica nanoparticles as the nanoparticles. As the silica nanoparticles, wet silica, dry silica, aerogel, etc. can be used.

[0055] In the present invention, it is preferable that at least one of the oxide particles, carbide particles, nitride particles, and inorganic hydrate particles selected as the inorganic particles 15 be nanoparticles. As described above, titania has a high effect of blocking radiant heat, and silica nanoparticles have extremely low conductive heat transfer and can maintain excellent heat insulation even when compressive stress is applied to the battery protective sheet 1. Therefore, it is most preferable to use both titania and silica nanoparticles as the inorganic particles 15.

[0056] Limiting the average primary particle diameter of the nanoparticles to a predetermined range can achieve even higher thermal insulation. 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 battery protective sheet 1 can be suppressed, particularly in the temperature range below 500°C, and the thermal insulation 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 of the battery protective sheet 1 to be maintained.

[0057] 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.

[0058] (1-2-2. 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.

[0059] 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).

[0060] 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

[0061] Furthermore, in a battery pack that has experienced thermal runaway, the temperature rises sharply to over 200°C and continues to rise to around 700°C. Therefore, it is preferable that the inorganic particles be made of an inorganic hydrate whose thermal decomposition onset temperature is 200°C or higher. The thermal decomposition onset 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 of the rapid temperature rise in a battery cell that has experienced thermal runaway, and can efficiently suppress the temperature rise, making them preferable inorganic hydrates.

[0062] When inorganic hydrate particles are used, if their average particle size is too large, it may take some time for the inorganic hydrate particles near the center of the sheet layer 10 to reach their thermal decomposition temperature, and the inorganic hydrate particles near the center of the sheet may not be completely thermally decomposed. For this reason, the average secondary particle size 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.

[0063] (1-3.Binding material) The papermaking sheet layer 10 preferably further contains a binder 17. Figure 3 is an enlarged schematic diagram of part B in Figure 2, which prevents the first inorganic fibers 11 and also the inorganic particles 15 (not shown) from falling off the papermaking sheet layer 10, thereby maintaining its strength.

[0064] The binder 17 can be selected from inorganic binders such as alumina sol and silica sol, and organic binders such as cationized starch and acrylic resin. These binders 17 are used in the form of an aqueous solution as the raw material for the papermaking sheet layer 10, and when dried, they remain at the contact points of the first inorganic fibers 11 and inorganic particles 15 to bind them together.

[0065] (1-4. Composition of the Papermaking Sheet Layer) When the papermaking sheet layer 10 contains inorganic particles 15 and binder 17, it is preferable that the inorganic particles 15 account for 30 to 94 mass % of the total amount of the papermaking sheet layer 10, the binder 17 account for 0 to 10 mass %, and the remainder be the first inorganic fibers 11. By using such a composition, the effects of the inorganic particles 15 and binder 17 described above can be obtained in a balanced manner.

[0066] (1-5. Thickness of the papermaking sheet layer) The thickness of the paper-made sheet layer 10 is preferably 0.1 to 5 mm. When the thickness of the paper-made sheet layer 10 is 0.1 mm or more, high heat insulating properties can be imparted to the battery protective sheet 1. When the thickness of the paper-made sheet layer 10 is 5 mm or less, flexibility can be ensured, and the battery protective sheet 1 can be bent into a predetermined shape for use. A thickness of 0.2 to 1.1 mm is preferable.

[0067] (2. Cross layer) 2, the cloth layer 20 is formed by weaving second inorganic fibers 21 into a cross shape using weft threads 21a and warp threads 21b. The second inorganic fibers 21 are continuous fibers that can form a cross, and the long fiber length ensures high strength of the battery protective sheet 1.

[0068] (2-1. Second inorganic fiber) The second inorganic fibers 21 may be, as with the first inorganic fibers 11, ceramic fibers such as silica fibers, alumina fibers, alumina silicate fibers, and zirconia fibers, glass fibers, etc. These inorganic fibers may be used alone or in combination of two or more.

[0069] The second inorganic fibers 21 and the first inorganic fibers 11 may be the same type of inorganic fibers or different types of inorganic fibers. In either case, the combination of inorganic materials results in the battery protective sheet 1 having excellent heat resistance.

[0070] (2-2. Thickness of the cloth layer) The cloth layer 20 preferably has a thickness of 0.1 to 5 mm. When the cloth layer 20 has a thickness of 0.1 mm or more, high mechanical strength can be imparted to the battery protective sheet 1. When the cloth layer 20 has a thickness of 5 mm or less, flexibility can be ensured, and the battery protective sheet 1 can be bent into a predetermined shape for use. A thickness of 0.3 to 1.4 mm is preferable.

[0071] (3. Middle Class) As shown in Figure 2, it is preferable that in the interface region between the papermaking sheet layer 10 and the cloth layer 20, the first inorganic fibers 11 of the papermaking sheet layer 10 penetrate into the meshes of the second inorganic fibers 21 of the cloth layer 20 to form an intermediate layer 30.

[0072] The penetration of the second inorganic fibers 21 into the cloth layer 20 ensures high peel strength. Furthermore, because the cloth layer 20 and the papermaking sheet layer 10 are firmly bonded together, the battery protective sheet 1 is unlikely to peel off even when subjected to repeated vibrations or external compression, and is unlikely to fall off even when attached to the side or top surface of the inner wall of the battery case 120 of the battery module 100 (described later). Furthermore, because the cloth layer 20 and the papermaking sheet layer 10 are both inorganic and directly bonded together without the intervention of an organic material, the battery protective sheet 1 will not peel off even when exposed to high temperatures, ensuring stable use.

[0073] (4. Manufacturing method of battery protective sheet) The first inorganic fibers 11, which are the raw materials for the papermaking sheet layer 10, as well as the inorganic particles 15 and binder 17, are added to water in a predetermined ratio to prepare a suspension.

[0074] The above suspension is poured onto one side of the cloth layer 20, the water is drained and dehydrated, and then the layer is pressurized and vacuum dried to obtain a battery protective sheet 1 in which the cloth layer 20 and the papermaking sheet layer 10 are joined together with the first inorganic fibers 11 of the papermaking sheet layer 10 penetrating the stitches of the second inorganic fibers 21 of the cloth layer 20.

[0075] [Embodiment 2] As shown in Fig. 4, the battery protective sheet 1 may have a first covering layer 50 attached to the outside of the papermaking sheet layer 10 via a first bonding layer 40, in addition to the papermaking sheet layer 10 and the cloth layer 20. The first covering layer 50 can prevent powder (first inorganic fibers 11, inorganic particles 15, and cured binder 17) from falling off from the papermaking sheet layer 10. Furthermore, when the first covering layer 50 is fixed by the first bonding layer 40, it is less likely to peel off even when an external force such as friction is applied.

[0076] (1. First Bonding Layer) There are no particular limitations on the material of the first bonding layer 40, as long as it can bond the first inorganic fibers 11 and inorganic particles 15 that make up the papermaking sheet layer 10 to the material forming the first coating layer 50 (described below). For example, various types of adhesives, thermoplastic resins, double-sided tape, etc. can be used.

[0077] (2. First Covering Layer) The first covering layer 50 can be made of a resin such as polypropylene or paper, and a film or cloth made of these can be used.

[0078] As shown in the figure, it is also preferable to have a second covering layer 70 on the outside of the cloth layer 20 via a second bonding layer 60. The second covering layer 70 makes the ends of the cloth layer 20 less likely to fray even when external frictional force is applied to them.

[0079] The second bonding layer 60 and the second covering layer 70 can be made of the same materials as the first bonding layer 40 and the first covering layer 50 described above.

[0080] [Embodiment 3] 5, the battery protective sheet 1 may have, in addition to the paper-made sheet layer 10 and the cloth layer 20, a first covering layer 50 attached to the outside of the paper-made sheet layer 10. Also, a second covering layer 70 may be attached to the outside of the cloth layer 20. The details and effects of the first covering layer 50 and the second covering layer 70 are the same as those in the second embodiment.

[0081] However, since the first coating layer 50 and the second coating layer 70 are attached directly to the surface of the paper-made sheet layer or the cloth layer 20 without an adhesive layer, a portion of the first coating layer 50 melts and bonds to the paper-made sheet layer, or a portion of the second coating layer 70 melts and bonds to the cloth layer 20, and this can be applied to a first coating layer 50 or a second coating layer 70 made of a resin having a softening point.

[0082] <Battery module> 6, the battery module 100 is configured by attaching the battery protective sheet 1 to the entire inner surface (ceiling, side walls, and bottom) of a battery case 120 that houses multiple battery packs 110. When attaching the battery protective sheet 1, either the papermaking sheet layer 10 or the cloth layer 20 may face the case side relative to the battery case 120.

[0083] The battery module 100 is lined with the battery protective sheet 1, which protects the battery assembly 110 from external damage caused by protrusions, suppresses heat transfer to the outside of the battery case 120 in the event of an abnormality in the battery assembly 110, preventing damage, and prevents combustible materials such as the organic electrolyte solution in the battery assembly 110 from coming into contact with the outside air and combusting violently, thereby providing a high level of safety. [Example]

[0084] Example 1 Glass fibers were weighed as the first inorganic fibers, accounting for 11% by mass of the total amount; silica nanoparticles and titania were weighed as the inorganic particles, accounting for 80% by mass of the total amount (silica nanoparticles (average particle size 5 nm): 56% by mass; titania (average particle size 8 μm): 24% by mass); and acrylic resin was weighed as the binder, accounting for 5% by mass of the total amount. These were added to water and stirred well to prepare a suspension. The suspension was then poured onto one side of a silica fiber cloth (thickness 1.36 mm, 4% by mass of the total amount), dehydrated, pressurized, and vacuum dried to produce a battery protective sheet in which a paper-formed sheet layer and a cloth layer were laminated. The thickness of the paper-formed sheet layer was 1.0 mm.

[0085] Example 2 A battery protection sheet was produced by attaching polypropylene films to both sides of the battery protection sheet of Example 1 via double-sided tape to form the first and second covering layers, and applying pressure from both sides.

[0086] (Evaluation test) A peel test was performed to evaluate the battery protective sheet of Example 1 and the battery protective sheet of Example 2. That is, as shown in Fig. 7, a battery protective sheet 200 was attached to two steel plates 210 using double-sided tape, and pulled in the vertical direction as shown in the figure, and the shear force at which peeling occurred was measured.

[0087] As a result of the measurement, the battery protective sheet of Example 1 had a resistance of 15 [N / cm 2 In contrast, the battery protective sheet of Example 2 peeled off inside the papermaking sheet layer at a shear force of 90 N / cm 2 The shear force of " caused the double-sided tape to peel off between the steel plate 210 and the polypropylene film on the cloth layer side.

[0088] From this, it was confirmed that in the battery protective sheets of Examples 1 and 2, the paper-made sheet layer and the cloth layer were sufficiently bonded, resulting in an integrated battery protective sheet having mechanical impact resistance and high thermal insulation properties. Furthermore, it can be seen that the battery protective sheet of Example 2 has a stronger adhesive force between the uneven papermaking sheet layer and the polypropylene film, resulting in a stronger bonding force. When fabricating a battery module, placing the papermaking sheet layer on the case side can result in a stronger bonding force. [Explanation of symbols]

[0089] 1 Battery protection sheet 10 Papermaking sheet layer 11 First inorganic fiber 15 Inorganic particles 17 Binding material 20 cross layers 21 Second inorganic fiber 30 Middle Class 40 First bonding layer 50 First coating layer 60 Second bonding layer 70 Second coating layer 100 battery modules 110 Battery pack 120 Battery Case 200 Battery protection sheet 210 Steel plate

Claims

1. The sheet has a first inorganic fiber-containing sheet layer and a second inorganic fiber-containing cloth layer, The battery protective sheet has an intermediate layer at the interface region between the cloth layer and the paper-made sheet layer, in which the first inorganic fibers penetrate the meshes of the second inorganic fibers of the cloth layer.

2. 2. The battery protective sheet according to claim 1, wherein the first inorganic fibers have an average fiber length of 0.5 to 10 mm.

3. 3. The battery protective sheet according to claim 1, wherein the papermaking sheet layer further contains inorganic particles.

4. 4. The battery protective sheet according to claim 1, wherein the paper-made sheet layer further contains a binder.

5. 5. The battery protective sheet according to claim 1, wherein the paper-made sheet layer has a thickness of 0.1 to 5 mm.

6. 6. The battery protective sheet according to claim 1, wherein the cloth layer has a thickness of 0.1 to 5 mm.

7. 7. The battery protective sheet according to claim 1, further comprising a first covering layer on the outside of the paper-made sheet layer.

8. 8. The battery protective sheet according to claim 7, wherein the first covering layer and the papermaking sheet layer are joined together by a first joining layer made of an adhesive or a thermoplastic resin.

9. 9. The battery protective sheet according to claim 1, further comprising a second covering layer on the outside of the cloth layer.

10. 10. The battery protective sheet according to claim 9, wherein the second cover layer and the cloth layer are joined together by a second joining layer made of an adhesive or a thermoplastic resin.

11. 11. A battery module comprising: a plurality of battery assemblies; a case for accommodating the battery assemblies; and the battery protective sheet according to claim 1 attached to the inside of the case.

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