Impact absorbing material for battery module, method for manufacturing same, and battery module

Abstract

The present invention provides an impact absorbing material for a battery module, a method for manufacturing the same, and a battery module that make it possible, even when high-temperature fragments scatter during thermal runaway of a battery, to absorb an impact due to collision of the fragments, to suppress breakage of a battery cell and a battery case inside the battery module, to maintain excellent thermal insulation properties, and to ensure safety. The impact absorbing material (10) has inorganic particle pieces (11), large-diameter inorganic fibers (12), and small-diameter fibers (13) having an average fiber diameter that is not more than 0.2 times the average fiber diameter of the large-diameter inorganic fibers. In addition, when the length of the long side of the inorganic particle piece (11) is L1 (μm) and the length of the short side thereof is L2 (μm), a length ratio R calculated by the formula L1 / L2 is 2 or more and 20 or less.

Description

Shock absorbing material for battery module, method for producing the same, and battery module

[0001] The present invention relates to a shock absorbing material for a battery module, a method for producing the same, and a battery module including the shock absorbing material for a battery module.

[0002] In recent years, lithium ion secondary batteries have been used in electric vehicles and the like for environmental protection. However, since lithium ion secondary batteries use an organic electrolyte, if ignition occurs during thermal runaway, a flame may be generated, which may damage the battery pack.

[0003] For example, Patent Document 1 proposes a battery pack cover having excellent flame insulation properties, which includes a cover base material and an inorganic fiber molded body having a tensile strength of 20 N or more in a predetermined tensile test. The inorganic fiber molded body is composed of inorganic fibers having an average fiber length of 3 mm or more, and examples of the inorganic fibers include single or composite fibers of silica, alumina / silica, zirconia containing these, spinel, titania and the like.

[0004] International Publication No. WO 2022 / 131067

[0005] However, in the battery pack cover described in Patent Document 1, an alumina fiber needle blanket is used as the inorganic fiber molded body. Although the tensile strength in the longitudinal direction is high, the stress from the vertical direction is not sufficient. Specifically, when a battery cell undergoes thermal runaway, a flame containing crushed cell members at a temperature of 800° C. or higher may collide with the battery pack cover. In this case, since the battery pack cover described in Patent Document 1 uses crystallized inorganic fibers, the bending strength is low, and sufficient impact resistance cannot be obtained.

[0006] The present invention has been made in view of the above problems, and aims to provide a shock-absorbing material for battery modules, a method for manufacturing the same, and a battery module that can absorb the impact caused by the collision of high-temperature crushed material even when high-temperature crushed material is scattered during thermal runaway of a battery, thereby suppressing damage to battery cells and battery cases inside the battery module, while maintaining excellent heat insulation and ensuring safety.

[0007] The above objective of the present invention is achieved by the configuration described in [1] below for a shock-absorbing material for a battery module.

[0008] [1] A shock-absorbing material for a battery module, comprising inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers having an average fiber diameter of 0.2 times or less the average fiber diameter of the large-diameter inorganic fibers, wherein when the length of the long side of the inorganic particle fragment is L1 (μm) and the length of the short side is L2 (μm), the length ratio R calculated by formula L1 / L2 is 2 or more and 20 or less.

[0009] Furthermore, preferred embodiments of the present invention relating to shock-absorbing materials for battery modules are described in [2] to

[17] below.

[0010] [2] The shock absorber for a battery module according to [1], further comprising a binder, wherein the inorganic particle fragments comprise at least one selected from wollastonite, talc, limestone, and kaolin, and the content of the inorganic particle fragments is 50% by mass or more and 80% by mass or less with respect to the total mass of the shock absorber for the battery module, wherein the large-diameter inorganic fibers comprise at least one selected from glass fibers, basalt fibers, silica fibers, alumina fibers, and alkali earth silicate fibers, and the content of the large-diameter inorganic fibers is 5% by mass or more and 35% by mass or less with respect to the total mass of the shock absorber for the battery module, wherein the small-diameter fibers comprise at least one selected from cellulose fibers, sepiolite, and attapulgite, and the content of the small-diameter fibers is 10% by mass or less with respect to the total mass of the shock absorber for the battery module, and the content of the binder comprises 5% by mass or more and 15% by mass or less with respect to the total mass of the shock absorber for the battery module.

[0011] [3] The shock-absorbing material for a battery module according to [1] or [2], characterized in that it has the inorganic particle fragments as its main component.

[0012] [4] The shock-absorbing material for a battery module according to any one of [1] to [3], further comprising at least one selected from organic fibers and a binder.

[0013] [5] The shock-absorbing material for a battery module according to any one of [1] to [4], characterized in that it has a plurality of voids on its surface and at least a portion of its interior, and at least a portion of the plurality of voids is formed around the large-diameter inorganic fiber.

[0014] [6] The shock-absorbing material for a battery module according to [5], characterized in that at least some of the large-diameter inorganic fibers penetrate the void.

[0015] [7] The shock-absorbing material for a battery module according to [5] or [6], characterized in that at least some of the ends of the large-diameter inorganic fibers protrude into the void.

[0016] [8] The shock absorber for a battery module according to any one of [1] to [7], characterized in that the inorganic particle fragments include at least one selected from boehmite, flaky silica, vermiculite, mica, plate alumina, wollastonite, talc, limestone, and kaolin.

[0017] [9] The shock absorber for a battery module according to any one of [1] to [8], characterized in that the large-diameter inorganic fiber includes at least one selected from glass fiber, basalt fiber, silica fiber, alumina fiber, and alkali earth silicate fiber.

[0018]

[10] The shock absorber for a battery module according to any one of [1] to [9], characterized in that the small-diameter fiber includes at least one selected from cellulose fiber, sepiolite, attapulgite, and microglass fiber.

[0019]

[11] The shock absorber for a battery module according to any one of [1] to

[10] , further comprising organic fibers, wherein the organic fibers comprise at least one selected from polyethylene terephthalate fibers, polypropylene fibers, polyethylene fibers, and polyvinyl alcohol fibers.

[0020]

[12] The shock-absorbing material for a battery module according to any one of [1] to

[11] , further comprising organic fibers, wherein the organic fibers include organic fibers having a core-sheath structure.

[0021]

[13] The shock absorber for a battery module according to any one of [1] to

[12] , further comprising a binder, wherein the binder comprises at least one selected from acrylic resin, vinyl acetate resin, phenolic resin, silicone resin, epoxy resin, styrene-butadiene resin, silicone-acrylic resin, and styrene resin.

[0022]

[14] The shock-absorbing material for a battery module according to any one of [1] to

[13] , further characterized by containing silica particles or glass particles.

[0023]

[15] The shock absorber for a battery module according to

[14] , characterized in that the silica particles include at least one of fused silica, wet silica, and dry silica.

[0024]

[16] The shock absorber for a battery module according to any one of [1] to

[13] , characterized by having a matrix portion containing a thermosetting resin.

[0025]

[17] The shock absorber for a battery module according to

[16] , characterized in that the thermosetting resin is at least one selected from silicone resin, epoxy resin and phenolic resin.

[0026] Furthermore, the above-mentioned objective of the present invention is achieved by the following configurations

[18] to

[20] relating to a method for manufacturing a shock-absorbing material for battery modules.

[0027]

[18] A method for manufacturing a shock-absorbing material for a battery module according to any one of [1] to

[17] , comprising: a stirring step of mixing and stirring a shock-absorbing material material including the inorganic particle fragments, the large-diameter inorganic fibers and the small-diameter fibers to prepare a mixed liquid; a dehydration step of dehydrating the mixed liquid to produce a wet sheet; and a drying step of drying the wet sheet.

[0028]

[19] The method for manufacturing a shock absorber for a battery module according to

[18] , characterized in that the shock absorber material has a binder.

[0029] A method for manufacturing a shock absorber for a battery module as described in

[20]

[16] , comprising: a stirring step of mixing and stirring a shock absorber material containing the inorganic particle fragments, the large-diameter inorganic fibers, the small-diameter fibers, and a binder to prepare a mixed solution; a dewatering step of dewatering the mixed solution to produce a wet sheet; a precursor preparation step of drying the wet sheet to produce a shock absorber precursor; an impregnation step of impregnating the shock absorber precursor into a matrix material containing a thermosetting resin; and a molding step of heating and pressurizing the shock absorber precursor containing the matrix material to form it.

[0030] Furthermore, the above-mentioned objective of the present invention is achieved by the configuration of the battery module described in

[21] below.

[0031]

[21] A battery module comprising: a shock-absorbing material for a battery module as described in any one of [1] to

[17] ; a battery cell; and a battery case for housing the shock-absorbing material for a battery module and the battery cell.

[0032] Furthermore, preferred embodiments of the present invention relating to a battery module are described in the following

[22] to

[23] .

[0033]

[22] The battery module according to

[21] , wherein the battery case has a top surface, side walls and a bottom wall inside, and the shock-absorbing material for the battery module is a battery pack cover attached to at least one surface selected from the top surface, side walls and bottom wall.

[0034]

[23] The battery module according to

[21] , characterized in that the shock-absorbing material for the battery module is an inter-cell separator disposed between a plurality of battery cells.

[0035] The shock-absorbing material for battery modules of the present invention has inorganic particle fragments made of an inorganic material of a predetermined size as its main component, and also has large-diameter inorganic fibers and small-diameter fibers. Therefore, even when high-temperature crushed material is scattered, it can absorb the impact caused by the collision of the crushed material and maintain high heat insulation properties.

[0036] Furthermore, according to the method for manufacturing the shock-absorbing material for battery modules of the present invention, the direction of the largest side of the inorganic particle fragments is more likely to be oriented parallel to the main surface of the shock-absorbing material, making it possible to manufacture a shock-absorbing material for battery modules with excellent shock resistance.

[0037] Furthermore, the battery module of the present invention has a shock-absorbing material for battery modules having excellent heat resistance and impact resistance, battery cells, and a battery case that houses them. Therefore, damage to the battery cells and battery case inside the battery module can be suppressed in the event of thermal runaway, and even if flames occur, the spread of fire to the outside can be more reliably prevented, thereby ensuring safety.

[0038] Figure 1 is a magnified micrograph of a shock-absorbing material for a battery module according to an embodiment of the present invention. Figure 2 is a micrograph of a shock-absorbing material using alumina fibers as large-diameter inorganic fibers. Figure 3 is a micrograph of a shock-absorbing material using glass fibers as large-diameter inorganic fibers. Figure 4 is a micrograph of the shock-absorbing material shown in Figure 3, with a wider field of view of the main surface. Figure 5 is a micrograph of the shock-absorbing material shown in Figure 3, with a wider field of view of the cross-section. Figure 6 is a magnified micrograph of the shock-absorbing material shown in Figure 1. Figure 7 is a schematic cross-sectional view showing a battery module according to an embodiment of the present invention.

[0039] The inventors of the present invention conducted diligent research to obtain an impact-absorbing material for battery modules that can improve the effect of suppressing damage caused by impacts from high-temperature crushed materials. As a result, they found that by including inorganic particle fragments of a predetermined size as the main component of the impact-absorbing material for battery modules, the property of preventing damage can be significantly improved. Furthermore, they found that by including large-diameter inorganic fibers and small-diameter fibers in the impact-absorbing material for battery modules, heat insulation can be obtained, and the inorganic particle fragments can be retained even at high temperatures, thereby further improving impact resistance. The present invention is based on the above findings.

[0040] Embodiments of the present invention will be described in detail below with reference to the drawings. In this specification, "shock-absorbing material for battery modules" may be simply referred to as "shock-absorbing material." Furthermore, the shock-absorbing material according to the present invention can be used in any part of a battery module where protection from impact and heat insulation are required. Moreover, the present invention is not limited to the embodiments described below, and can be modified and implemented as desired without departing from the spirit of the invention.

[0041] [Shock-absorbing material for battery modules] Figure 1 is a magnified micrograph of a shock-absorbing material for battery modules according to an embodiment of the present invention.

[0042] The shock absorbing material 10 comprises inorganic particle pieces 11, large-diameter inorganic fibers 12, small-diameter fibers 13, and a binder not shown in FIG. 1. The inorganic particle pieces 11 are, for example, wollastonite, and are a main component of the shock absorbing material according to the present embodiment. Further, the large-diameter inorganic fibers 12 shown in FIG. 1 are basalt fibers, and the small-diameter fibers 13 are sepiolite. Further, the shock absorbing material 10 has voids 14 in a part of the periphery of the large-diameter inorganic fibers 12. In the present specification, the term "main component" refers to a component contained in the shock absorbing material that has the highest content.

[0043] In the present embodiment, since the shock absorbing material 10 includes, as a main component, the inorganic particle pieces 11 having high heat resistance, a matrix portion of the shock absorbing material 10 is constituted by the inorganic particle pieces 11. Therefore, excellent heat insulation properties and heat resistance can be obtained.

[0044] Hereinafter, each component constituting the shock absorbing material will be described in detail.

[0045] <Inorganic Particle Pieces> In the present embodiment, the inorganic particle pieces 11 have a specific size (shape). Specifically, when the length of the long side of the inorganic particle piece 11 is defined as L1 (μm) and the length of the short side thereof is defined as L2 (μm), a length ratio R calculated by the formula L1 / L2 is specified. Examples of the shape of the inorganic particle piece 11 include a columnar shape, a prismatic shape, a scaly shape, a plate shape, and a flake shape.

[0046] When measuring the length L1 of the long side and the length L2 of the short side of the inorganic particle piece 11, for example, there is a method in which the main surface and cross section of the shock absorbing material are photographed with a SEM (Scanning Electron Microscope), and measurement is performed based on the obtained photograph. In the shock absorbing material, the inorganic particle pieces 11 are oriented so as to lie substantially horizontally. Therefore, in a main surface photograph obtained by photographing the main surface of the shock absorbing material, the distance between the two parallel lines that contact the inorganic particle piece 11 (the length L1 of the long side) when the distance between the parallel lines is the largest is measured, and the distance between the parallel lines when the distance is the smallest is also measured. In addition, the thickness of the inorganic particle piece is measured in a cross-sectional photograph obtained by photographing a cross section of the shock absorbing material. Then, the distance between the smallest parallel lines sandwiching the inorganic particle piece in the main surface photograph is compared with the thickness of the inorganic particle piece in the cross-sectional photograph, and the smaller value is taken as the length L2 of the short side. Thereby, the length L1 of the long side and the length L2 of the short side of the inorganic particle piece 11 can be measured. According to the above measurement method, when the inorganic particle piece 11 has a cylindrical shape or a prismatic shape, the length L2 of the short side is the radial length orthogonal to the longitudinal direction of the inorganic particle piece 11. In addition, when the inorganic particle piece 11 is scaly, the length L2 of the short side is the thickness of the inorganic particle piece 11 in a cross-sectional view. It is preferable that the length ratio R calculated by the formula L1 / L2 is an average value obtained by selecting at least five arbitrary inorganic particle pieces.

[0047] The larger the length ratio R calculated by formula L1 / L2, the more flat or rod-shaped the inorganic particle fragments 11 are. Thus, because the shock absorber 10 has flat or rod-shaped inorganic particle fragments 11 made of inorganic material, it is easier to hold them with the small-diameter fibers 13, which will be described later, compared to the case where the inorganic particle fragments are spherical with a length ratio R close to 1. Furthermore, the flat or rod-shaped inorganic particle fragments 11 tend to be oriented along the direction of the main surface (the widest surface) of the shock absorber 10. The inorganic particle fragments 11 being oriented along the direction of the main surface of the shock absorber 10 means that the direction of the largest side of the inorganic particle fragments 11, as measured as described above, is 0° or more and less than 45° with respect to the main surface. In other words, it can be said that the inorganic particle fragments tend to be oriented along the main surface when the number of inorganic particle fragments whose largest side is 0° or more and less than 45° with respect to the main surface is greater than the number of inorganic particle fragments whose largest side is 45° or more and less than 90° with respect to the main surface.

[0048] If a cloth made of inorganic fibers is used as an impact absorber, the inorganic fibers will break upon impact with high-temperature crushed material, and will be completely destroyed by continuous impacts from the crushed material. In contrast, in this embodiment, even when high-temperature crushed material impacts the impact absorber 10, the impact is absorbed by the wide surface area of ​​the inorganic particle fragments 11. Therefore, it is possible to obtain the effect of suppressing damage to the impact absorber 10 and to prevent damage to the area in which the impact absorber 10 is placed.

[0049] If the length ratio R is less than 2, the effect of being held by the small-diameter fibers 13 decreases, and the area subjected to impact also decreases, so sufficient impact resistance against high-temperature crushed material cannot be obtained. Therefore, the length ratio R calculated by formula L1 / L2 should be 2 or more, preferably 2.2 or more, and more preferably 2.5 or more. On the other hand, if the length ratio R exceeds 20, although the heat resistance does not change significantly, the orientation of the inorganic particle fragments 11 within the impact absorber decreases, and the impact resistance against high-temperature crushed material decreases. Therefore, the length ratio R calculated by formula L1 / L2 should be 20 or less, preferably 15 or less, more preferably 12 or less, and even more preferably 8 or less.

[0050] To obtain the above-mentioned effects from inorganic particle fragments, the content of inorganic particle fragments 11 is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 55% by mass or more, and particularly preferably 60% by mass or more, based on the total mass of the shock-absorbing material. Furthermore, if the content of inorganic particle fragments becomes too high, the content of large-diameter inorganic fibers and small-diameter fibers, described later, decreases, making it difficult to obtain the desired effects. Therefore, the content of inorganic particle fragments 11 is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 75% by mass or less, and particularly preferably 70% by mass or less, based on the total mass of the shock-absorbing material.

[0051] The inorganic particulate matter preferably includes at least one selected from, for example, boehmite, flake silica, vermiculite, mica, plate-like alumina, wollastonite, talc, limestone, and kaolin, and more preferably includes at least one selected from wollastonite, talc, limestone, and kaolin. These materials have heat resistance and high impact strength, and can therefore impart high strength to the impact absorber. In particular, for reasons such as heat resistance, quality stability, and cost, it is even more preferable to use wollastonite, talc, and mica, and it is especially preferable to use at least one of wollastonite and talc.

[0052] Wollastonite has a short fibrous form, for example, with an average fiber diameter of 5 μm and an average fiber length of about 15 μm, and the length ratio R calculated by formula L1 / L2 is about 3. Talc, on the other hand, is scaly, with the length of the longer side of the two-dimensional surface being about 15 μm and the thickness being 1 μm, and the length ratio R calculated by formula L1 / L2 is about 15.

[0053] <Large-diameter inorganic fibers> In the impact absorbing material according to this embodiment, the large-diameter inorganic fibers 12 have the effect of controlling the thickness of the impact absorbing material. That is, by increasing the content of the large-diameter inorganic fibers 12, the thickness of the impact absorbing material can be increased. In addition, the large-diameter inorganic fibers 12 also have the effect of improving the mechanical strength and shape retention of the impact absorbing material, and the strength and heat insulation of the impact absorbing material can be maintained even at high temperatures.

[0054] Figures 2 and 3 are micrographs showing examples of the impact-absorbing material shown in Figure 1 with modified large-diameter inorganic fibers 12. Note that the impact-absorbing materials shown in Figures 2 and 3 also contain a binder (not shown), similar to those in Figure 1. The only difference between the impact-absorbing materials in Figures 2 and 3 and those in Figure 1 is the type of large-diameter inorganic fiber; therefore, identical components are denoted by the same reference numerals, and detailed explanations are omitted.

[0055] The impact absorber 20 shown in Figure 2 uses alumina fibers as the large-diameter inorganic fibers 22, and the impact absorber 30 shown in Figure 3 uses glass fibers as the large-diameter inorganic fibers 32. In both the impact absorbers 20 and 30, voids 14 are formed in a part of the periphery of the large-diameter inorganic fibers 22 and 32.

[0056] Figure 4 is a micrograph showing a wider field of view of the main surface of the shock-absorbing material 30 shown in Figure 3. Figure 5 is a micrograph showing a wider field of view of the cross-section of the shock-absorbing material 30 shown in Figure 3. As shown in Figure 4, the shock-absorbing material 30 has multiple recesses formed on a part of its surface 30a, and has voids 14 surrounded by these recesses. As shown in Figure 5, the shock-absorbing material 30 also has multiple voids 14 inside. At least a portion of the voids 14 are formed around the large-diameter inorganic fibers 32, and the surface of the large-diameter inorganic fibers 32 is exposed within the voids 14.

[0057] Upon closer observation, it is found that the large-diameter inorganic fibers 32 within the void 14 include penetrating fibers 42a that extend through the void 14 and protruding fibers 42b whose ends protrude into the void 14. Furthermore, these penetrating fibers 42a and protruding fibers 42b extend in various different directions within the void 14, and some of them intersect and are in contact with each other. These penetrating fibers 42a and protruding fibers 42b are large-diameter inorganic fibers 32 contained in the impact absorber 30 that have extended from the surface or interior of the impact absorber 30. Therefore, it is considered that multiple large-diameter inorganic fibers 32 intersect and are in contact with each other on the surface or interior of the impact absorber 30. Consequently, these large-diameter inorganic fibers 32 act as a framework, and the impact absorber 30 can obtain extremely excellent strength.

[0058] In this embodiment, the impact absorbing material 10 mainly consists of flat or rod-shaped inorganic particle fragments 11. Compared to the case where fine inorganic particles are the main component, the movement of the inorganic particle fragments 11 during manufacturing is more easily hindered by the large-diameter inorganic fibers. Therefore, it is thought that the inorganic particle fragments 11 are less likely to fill around the large-diameter inorganic fibers, and voids 14 are more likely to form around the large-diameter inorganic fibers.

[0059] As described above, in this embodiment, since there are multiple voids 14 on the surface and inside, excellent heat insulation and flexibility can be obtained, and the shock absorption effect can be obtained when debris scattered from the battery cell collides with the shock absorber. Furthermore, as described above, the shock absorber 10 has penetrating fibers 42a that penetrate the voids 14 and protruding fibers 42b that protrude toward the voids 14, and these penetrating fibers 42a and protruding fibers 42b provide the effect of supporting the voids 14. Therefore, bending and cracking of the shock absorber originating from the voids 14 can be prevented, and excellent strength can be obtained.

[0060] The average fiber diameter of the large-diameter inorganic fibers is preferably 1 μm or more, and more preferably 3 μm or more. If the large-diameter inorganic fibers are too thick, the moldability and processability of the shock-absorbing material may decrease, so the average fiber diameter of the large-diameter inorganic fibers is preferably 20 μm or less, and more preferably 15 μm or less.

[0061] Furthermore, if the large-diameter inorganic fibers are too long, their moldability and processability may decrease, so it is preferable to keep the fiber length to 100 mm or less. On the other hand, if the large-diameter inorganic fibers are too short, their shape retention and mechanical strength may decrease, so it is preferable to keep the fiber length to 0.1 mm or more.

[0062] To obtain the above-mentioned effects from large-diameter inorganic fibers, the content of large-diameter inorganic fibers is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and particularly preferably 15% by mass or more, based on the total mass of the shock absorber. Furthermore, if the content of large-diameter inorganic fibers becomes too high, the content of inorganic particle fragments decreases, making it difficult to obtain the desired effect. Therefore, the content of large-diameter inorganic fibers is preferably 40% by mass or less, more preferably 35% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, based on the total mass of the shock absorber.

[0063] The large-diameter inorganic fibers preferably include at least one selected from glass fibers, basalt fibers, silica fibers, alumina fibers, and alkali earth silicate fibers (AES fibers), and it is preferable that all of the large-diameter inorganic fibers consist of at least one of the above fibers. Of these fibers, it is more preferable to use at least one of alumina fibers, glass fibers, and basalt fibers, particularly from the viewpoint of heat resistance. It is also preferable to use at least one of glass fibers and basalt fibers from the viewpoint of availability and cost. When basalt fibers are used as the large-diameter inorganic fibers, it is more preferable that the basalt fiber content be 5% by mass or more and 35% by mass or less, relative to the total mass of the impact absorber.

[0064] <Small-diameter fibers> In the impact-absorbing material according to this embodiment, small-diameter fibers have the effect of holding inorganic particle fragments and increasing the flexibility of the impact-absorbing material. The small-diameter fibers may be inorganic fibers or organic fibers.

[0065] When the average fiber diameter of small-diameter fibers approaches that of large-diameter inorganic fibers, the effect of holding inorganic particle fragments cannot be sufficiently obtained. Therefore, small-diameter fibers should have an average fiber diameter of 0.2 times or less the average fiber diameter of large-diameter inorganic fibers, preferably 0.1 times or less, and more preferably 0.05 times or less. Specifically, the average fiber diameter of small-diameter fibers is preferably 1 μm or less, more preferably 0.8 μm or less, and even more preferably 0.5 μm or less.

[0066] On the other hand, if the average fiber diameter of the small-diameter fibers is too small, they are prone to breakage and their ability to hold inorganic particle fragments decreases. Therefore, the average fiber diameter of the small-diameter fibers is preferably 1 nm or more, more preferably 10 nm or more, and even more preferably 50 nm or more.

[0067] Furthermore, if the small-diameter fibers are too short or too long, the moldability of the shock-absorbing material decreases, as does its effect of holding inorganic particle fragments. Therefore, the average fiber length of the small-diameter fibers is preferably 5 μm or more, and more preferably 10 μm or more. In addition, the average fiber length of the small-diameter fibers is preferably 500 μm or less, and more preferably 100 μm or less.

[0068] To obtain the above-mentioned effects from small-diameter fibers, the content of small-diameter fibers is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, based on the total mass of the shock absorber. Furthermore, if the content of small-diameter fibers becomes too high, the moldability of the shock absorber decreases, and the content of inorganic particles decreases, making it difficult to obtain the desired effects. Therefore, the content of small-diameter fibers is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less, based on the total mass of the shock absorber. Furthermore, the content of small-diameter fibers is more preferably 8% by mass or less, and even more preferably 6% by mass or less, based on the total mass of the shock absorber.

[0069] The small-diameter fibers preferably include at least one selected from cellulose fibers (including pulp fibers), sepiolite, attapulgite, and microglass fibers. More preferably, they include at least one selected from cellulose fibers (including pulp fibers), sepiolite, and attapulgite, and even more preferably, all of the small-diameter fibers consist of at least one of the above materials. In particular, from the viewpoint of heat resistance, the use of sepiolite is more preferable.

[0070] As described above, the impact-absorbing material according to this embodiment has inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers. The inorganic particle fragments may have a flaky shape as well as a short fibrous shape, but each component can be clearly distinguished by the length in the longitudinal direction or the length of the long side of the broad surface that extends in two dimensions. For example, the fiber length of the large-diameter inorganic fibers is several millimeters, while the length of the longest side of the inorganic particle fragments is at most 250 μm, so the inorganic particle fragments and large-diameter inorganic fibers are very different. Furthermore, the average fiber diameter of the small-diameter fibers is preferably 1 μm or less, and the aspect ratio (average fiber length / average fiber diameter) of the small-diameter fibers is, for example, 40 or more, so the inorganic particle fragments and small-diameter fibers are also very different.

[0071] In the impact absorbing material according to this embodiment, the total content of inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers is preferably 65% ​​by mass or more, and more preferably 75% by mass or more, based on the total mass of the impact absorbing material.

[0072] The impact-absorbing material shown in Figures 1 to 5 contains inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers, as well as a binder. In this embodiment, the binder is not essential, but it is preferable to include at least one selected from the binder and organic fibers for the purpose of binding the inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers together, and for improving the strength and impact resistance of the impact-absorbing material. The binder will be described in detail below with reference to Figure 6.

[0073] Figure 6 is a magnified micrograph of the shock-absorbing material 10 shown in Figure 1. In Figure 6, the same reference numerals are used for parts identical to those shown in Figure 1, and their detailed descriptions are omitted.

[0074] The impact-absorbing material 10 shown in Figure 6 contains an acrylic resin added as a binder 15. The binder 15 melts during the manufacturing of the impact-absorbing material 10, spreads in a film-like manner, and then hardens. More specifically, the binder 15 self-crosslinks during the drying process and precursor production process during the manufacturing of the impact-absorbing material 10, and spreads in a film-like manner between the inorganic particle fragments 11, large-diameter inorganic fibers 12, and small-diameter fibers 13. Therefore, the inclusion of the binder 15 in the impact-absorbing material 10 binds the inorganic particle fragments 11, large-diameter inorganic fibers, and small-diameter fibers 13, thereby preventing powder shedding. Furthermore, because the binder can firmly bond each component, damage caused by the impact of high-temperature crushed material can be further suppressed, and the strength of the impact-absorbing material can be improved.

[0075] <Binder> When the shock absorber contains a binder, in order to obtain the effects of preventing powder shedding and improving strength due to the binder, the binder content is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 8% by mass or more, based on the total mass of the shock absorber. On the other hand, if the binder content is too high, the heat resistance may decrease, so the binder content is preferably 35% by mass or less, more preferably 25% by mass or less, even more preferably 15% by mass or less, and particularly preferably 12% by mass or less, based on the total mass of the shock absorber.

[0076] As a binder, for example, one can be selected from acrylic resins, vinyl acetate resins, phenolic resins, silicone resins, epoxy resins, styrene-butadiene resins, silicone-acrylic resins, and styrene resins. Of these binders, using a thermoplastic resin provides greater flexibility after molding compared to using a thermosetting resin, allowing it to be deformed into various shapes and positioned at the desired location. Therefore, it is more preferable to select a binder that includes at least one selected from acrylic resins, vinyl acetate resins, styrene-butadiene resins, silicone-acrylic resins, and styrene resins.

[0077] <Organic Fibers> As described above, in this embodiment, the shock absorber may have organic fibers. When organic fibers are included in the shock absorber together with the large-diameter inorganic fibers and small-diameter fibers, they form the framework of the shock absorber and enhance flexibility, thereby improving the strength and impact resistance of the shock absorber. Depending on their melting point, organic fibers can also be used as a binder. For example, when the shock absorber according to this embodiment is manufactured by a wet molding method, the wet paper strength is low after papermaking, so the sheet may break before drying. Also, the outer surface of the shock absorber may be covered by lamination. For this reason, it is preferable that the shock absorber has organic fibers in order to improve strength and adhesion to film. It is preferable that the organic fibers include at least one selected from polyethylene terephthalate (PET) fibers, polypropylene (PP) fibers, polyethylene (PE) fibers, and polyvinyl alcohol (PVA) fibers (vinylon).

[0078] Furthermore, it is also preferable to use core-sheath structured fibers as organic fibers. Core-sheath structured organic fibers have a core portion extending in the longitudinal direction of the fiber and a sheath portion formed to cover the outer surface of the core portion. The core portion and the sheath portion are made of organic materials having different melting points, with the melting point of the organic material constituting the core portion being higher than that of the organic material constituting the sheath portion. When the shock absorber contains core-sheath structured organic fibers, the sheath portion functions as a binder that fuses the inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers together, and the core portion functions as a skeleton.

[0079] In an organic fiber with a core-sheath structure, the organic material constituting the core is not particularly limited, as long as its melting point is higher than that of the organic material constituting the sheath. For example, the organic material constituting the core can be at least one selected from polyethylene terephthalate, polypropylene, and nylon. The organic material constituting the sheath can be at least one selected from polyethylene terephthalate, polyethylene, polypropylene, and nylon.

[0080] When the shock-absorbing material has an organic fiber core-sheath structure, the melting point of the organic material constituting the sheath is preferably 90°C or higher, and more preferably 100°C or higher. Furthermore, the melting point of the organic material constituting the sheath is preferably 150°C or lower, and more preferably 130°C or lower. Moreover, the melting point of the organic material constituting the core is preferably 60°C or higher, more preferably 70°C or higher, and even more preferably 80°C or higher than the melting point of the organic material constituting the sheath.

[0081] Furthermore, the small-diameter fibers contained as essential components in the shock-absorbing material according to this embodiment and the organic fibers mentioned above can be distinguished from each other because they differ in size and type. Specifically, the average fiber diameter of the small-diameter fibers is preferably 1 nm to 1 μm, and the average fiber length is preferably 5 μm to 500 μm. In contrast, the average fiber diameter of the organic fibers, which may be optionally included in the shock-absorbing material, is preferably 3 μm to 30 μm, and the average fiber length is preferably 3 mm to 6 mm. However, since organic fibers may break and shorten during the manufacturing process of the shock-absorbing material, it is necessary to distinguish them from the small-diameter fibers, taking into account the differences in type. Examples of small-diameter fibers include fibers from natural raw materials such as cellulose fiber (pulp), sepiolite, and attapulgite, as well as artificial mineral fibers such as microglass fibers. In contrast, examples of organic fibers that may be optionally included in the shock-absorbing material include synthetic (chemical) fibers such as PET fiber, PP fiber, PE fiber, and PVA fiber.

[0082] However, the shock absorber does not necessarily need to contain organic fibers, and the organic fiber content may be 0% by mass. However, if the shock absorber contains organic fibers, the above effects due to the addition of organic fibers can be obtained if the organic fiber content is 0.5% by mass or more. Therefore, the organic fiber content is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, relative to the total mass of the shock absorber. On the other hand, if the organic fiber content is 5% by mass or less, it is possible to prevent a decrease in heat resistance and impact resistance. Therefore, the organic fiber content is preferably 5% by mass or less, and more preferably 4% by mass or less, relative to the total mass of the shock absorber.

[0083] In this embodiment, the shock absorber may further preferably contain silica particles or glass particles. Although not shown in the figures, the shock absorber containing silica particles or glass particles shows, for example, a state in which the silica particles or glass particles are aggregated and packed into voids, inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers as shown in Figure 1. In this way, when the shock absorber contains silica particles or glass particles, if the battery cell experiences thermal runaway and the shock absorber is exposed to flames, the silica component sinters, the particles bond together and harden, and thus the impact resistance can be significantly improved.

[0084] The silica particles are preferably made of amorphous silica, and are preferably particles containing at least one of fused silica, wet silica, and dry silica.

[0085] Furthermore, in this embodiment, it is also preferable that the shock absorber has a matrix portion containing a thermosetting resin. The method for manufacturing the shock absorber containing the thermosetting resin will be described later, but it is manufactured by preparing a precursor of the shock absorber, impregnating this precursor with a material containing a thermosetting resin, and then heating and pressurizing it. Therefore, the thermosetting resin penetrates into the voids and other areas shown in Figure 1, hardens upon heating, and forms the matrix portion. Specifically, the thermosetting resin is present in the voids and other areas shown in Figure 1, as well as in the gaps between inorganic particles, large-diameter inorganic fibers, and small-diameter fibers. However, it does not completely fill all the voids and gaps; rather, only a portion of these are filled with the thermosetting resin.

[0086] Thus, shock-absorbing materials containing thermosetting resins can be manufactured in various shapes and, because they have high hardness, their impact resistance can be further improved.

[0087] As the thermosetting resin, at least one selected from silicone resin, epoxy resin, and phenolic resin can be used, and the type of resin should be selected according to the required properties. For example, silicone resin has high heat resistance and sintersects when the shock absorber is exposed to flame, thus providing excellent impact resistance. Furthermore, a shock absorber having a matrix containing epoxy resin can achieve high strength. Although epoxy resin may burn when exposed to flame, by appropriately designing the thickness of the shock absorber, it is possible to prevent the formation of holes that penetrate from the flame-exposed surface to the back surface in the shock absorber.

[0088] (Sheet density of impact-absorbing material) In the impact-absorbing material according to this embodiment, the heat resistance and impact resistance differ depending on the type and content of large-diameter fibers, the sheet density, and the sheet thickness, for example. Therefore, the sheet density is not specifically defined, but the higher the sheet density, the better the heat resistance and impact resistance can be. Specifically, the sheet density is 0.8 g / cm³. ３ Preferably, it is 0.9 g / cm³ or more. ３ It is more preferable that the concentration be greater than or equal to 1.0 g / cm³. ３ It is even more preferable that the concentration be greater than or equal to 1.1 g / cm³.３ It is especially preferable that the above conditions are met.

[0089] [Method for Manufacturing Shock Absorbing Material for Battery Modules] Below, an example of a method for manufacturing the shock absorbing material according to this embodiment will be described using the shock absorbing material 10 shown in Figure 1 as an example. As a first embodiment, a method for manufacturing a shock absorbing material including inorganic particle fragments, large-diameter inorganic fibers, small-diameter fibers, and a binder will be described.

[0090] <First Embodiment> (Agitation Process) The shock absorber 10 can be manufactured, for example, by a wet molding method. First, a mixture is prepared by mixing inorganic particle fragments 11, large-diameter inorganic fibers 12, small-diameter fibers 13 and a binder in water and stirring with a stirrer.

[0091] (Dehydration process) The mixture is then dehydrated by sucking moisture from the back of the mesh through a filtration mesh to produce a wet sheet.

[0092] (Heating and pressurizing process (drying process)) The obtained wet sheet is then heated and pressurized to dry it. This allows the shock absorber 10 to be obtained. Before the heating and pressurizing process, a ventilation drying treatment may be performed in which hot air is passed through the wet sheet to dry it, but this ventilation drying treatment may be omitted, and the sheet may be dried by heating and pressurizing it while it is still wet.

[0093] In addition to inorganic particle fragments, large-diameter inorganic fibers, small-diameter fibers, and binders, the impact-absorbing material can also include the aforementioned organic fibers (including organic fibers with a core-sheath structure), silica particles, or glass particles.

[0094] According to the manufacturing method of the shock absorber according to the first embodiment described above, since a wet molding method is used, when moisture from the mixed liquid is sucked from the back side of the mesh, the direction of the largest side of the inorganic particle fragments 11 tends to be oriented parallel to the main surface of the resulting shock absorber 10. Therefore, even when high-temperature crushed material collides with the shock absorber 10, the impact can be absorbed by the wide surface of the inorganic particle fragments 11, thereby suppressing damage to the shock absorber 10 and maintaining the heat insulation performance of the shock absorber 10 for a long time.

[0095] Next, as a second embodiment, a method for manufacturing an impact absorbing material having a matrix portion containing a thermosetting resin will be described.

[0096] <Second Embodiment> (Agitation Process and Dehydration Process) First, similar to the first embodiment, the shock-absorbing material is mixed in water and stirred with a stirrer to prepare a mixed solution (Agitation Process). Then, the mixed solution is dehydrated to produce a wet sheet (Dehydration Process).

[0097] (Precursor preparation process) The obtained wet sheet is dried by passing hot air through it to prepare a shock-absorbing material precursor.

[0098] (Impregnation process) The shock-absorbing material precursor is impregnated into a matrix material containing a thermosetting resin.

[0099] (Molding process) The impact-absorbing material precursor containing the matrix material obtained in the impregnation process is heated and pressurized to form the desired shape. This allows the impact-absorbing material to be obtained.

[0100] In the manufacturing method of the shock absorber according to the second embodiment described above, a wet molding method is used, similar to the first embodiment. As a result, the direction of the largest side of the inorganic particle fragments is more easily oriented parallel to the main surface of the shock absorber. Therefore, excellent impact resistance can be obtained, and the heat insulation performance of the shock absorber can be maintained for a long time. In the second embodiment, the shock absorber precursor is impregnated with a matrix material and then cured by heating and pressurizing. Since thermosetting resins harden when heated, the shock absorber precursor can be placed in a mold of the desired shape and then heated and pressurized to easily mold it into the required shape (3D shape). Therefore, the shock absorber can be freely applied according to its position and shape.

[0101] [Battery Module] Figure 7 is a schematic cross-sectional view showing a battery module according to an embodiment of the present invention. As shown in Figure 7, the battery module 100 houses a plurality of battery cells 110 in a battery case 120. The electrode terminals 111 of each battery cell 110 are connected in series by a busbar 130.

[0102] Furthermore, the battery case 120 has a top surface 120a, side walls 120b, and a bottom wall 120c inside. For example, shock-absorbing material 10 is attached to the entire surface of the top surface 120a of the battery case 120 using tape or the like. That is, the shock-absorbing material 10 shown in Figure 7 is used as a battery pack cover to protect the top surface 120a of the battery case 120.

[0103] The impact-absorbing material 10 according to this embodiment has excellent heat insulation properties and high strength even at high temperatures. Therefore, in the battery module 100 according to this embodiment, even if the battery cell 110 experiences thermal runaway and the impact-absorbing material 10 is exposed to high-temperature crushed material or flames, it can absorb the impact caused by the collision of the crushed material and suppress damage to the impact-absorbing material 10. Thus, heat insulation properties can be maintained, and even if flames occur, the spread of fire to the outside can be prevented more reliably. In addition, because the impact-absorbing material 10 absorbs the impact, damage to the battery case 120 can also be prevented, ensuring a high level of safety.

[0104] In the battery module 100 shown in Figure 7, the shock-absorbing material 10 is attached only to the top surface 120a of the battery case 120, but the present invention is not limited to this configuration. For example, by attaching the shock-absorbing material 10 to the gas outlet side of the battery cell 110, the transfer of heat to the outside of the battery case 120 can be delayed. That is, when the shock-absorbing material 10 is used as a battery pack cover, the surface to which the shock-absorbing material 10 is attached can be selected from at least one surface of the battery case 120, such as the top surface 120a, the side wall surface 120b, and the bottom wall surface 120c, depending on the configuration of the battery cell 110. Furthermore, if the shock-absorbing material 10 is attached to all surfaces of the battery case 120, such as the top surface 120a, the side wall surface 120b, and the bottom wall surface 120c, the heat insulation and flame retardancy can be further improved.

[0105] Furthermore, when the shock-absorbing material 10 is used as an inter-cell separator, the shock-absorbing material 10 can be placed between multiple battery cells 110. Using the shock-absorbing material 10 as an inter-cell separator can prevent damage to other battery cells in the event of thermal runaway in one battery cell, and can also suppress heat transfer, thereby preventing a chain reaction of thermal runaway.

[0106] Furthermore, when the shock-absorbing material is used as a battery pack cover, "shock-absorbing material" in this specification may be read as "battery pack cover." Also, when the shock-absorbing material is used as an inter-cell separator, "shock-absorbing material" may be read as "inter-cell separator." For example, the present invention also includes the following (battery pack cover).

[0107] (1) A battery pack cover having inorganic particle fragments as its main component, and comprising large-diameter inorganic fibers and small-diameter fibers having an average fiber diameter of 0.2 times or less the average fiber diameter of the large-diameter inorganic fibers, wherein when the length of the long side of the inorganic particle fragment is L1 (μm) and the length of the short side is L2 (μm), the length ratio R calculated by formula L1 / L2 is 2 or more and 20 or less.

[0108] Furthermore, preferred embodiments of the present invention relating to a battery pack cover are as follows (2) to (11).

[0109] (2) The battery pack cover according to (1), further comprising at least one selected from organic fibers and a binder.

[0110] (3) The battery pack cover according to (1) or (2), characterized in that it has a plurality of voids on its surface and at least a portion of its interior, and at least a portion of the plurality of voids is formed around the large-diameter inorganic fiber.

[0111] (4) The battery pack cover according to (3), characterized in that at least some of the large-diameter inorganic fibers penetrate the void.

[0112] (5) The battery pack cover according to (3) or (4), characterized in that at least some of the ends of the large-diameter inorganic fibers protrude into the void.

[0113] (6) The battery pack cover according to any one of (1) to (5), characterized in that the inorganic particle fragments include at least one selected from boehmite, flaky silica, vermiculite, mica, plate-like alumina, wollastonite, talc, limestone, and kaolin.

[0114] (7) The battery pack cover according to any one of (1) to (6), characterized in that the large-diameter inorganic fiber includes at least one selected from glass fiber, basalt fiber, silica fiber, alumina fiber, and alkali earth silicate fiber.

[0115] (8) The battery pack cover according to any one of (1) to (7), characterized in that the small-diameter fiber includes at least one selected from cellulose fiber, sepiolite, attapulgite, and microglass fiber.

[0116] (9) The battery pack cover according to any one of (1) to (8), further comprising organic fibers, wherein the organic fibers comprise at least one selected from polyethylene terephthalate fibers, polypropylene fibers, polyethylene fibers, and polyvinyl alcohol fibers.

[0117] (10) The battery pack cover according to any one of (1) to (9), further comprising organic fibers, wherein the organic fibers include organic fibers having a core-sheath structure.

[0118] (11) The battery pack cover according to any one of (1) to (10), further comprising a binder, wherein the binder comprises at least one selected from acrylic resin, vinyl acetate resin, phenolic resin, silicone resin, epoxy resin, styrene-butadiene resin, silicone-acrylic resin, and styrene resin.

[0119] Furthermore, the present invention also includes the following (battery module).

[0120] (12) A battery module comprising a battery pack cover as described in any one of (1) to (11), a battery cell, and a battery case for housing the battery pack cover and the battery cell.

[0121] Furthermore, a preferred embodiment of the present invention relating to a battery module is described in (13) below.

[0122] (13) The battery module according to (12), wherein the battery case has a top surface, a side wall surface and a bottom wall surface inside, and the battery pack cover is mounted on at least one surface selected from the top surface, the side wall surface and the bottom wall surface.

[0123] Furthermore, the present invention also includes the following (shock-absorbing material for battery modules).

[0124] "1" A shock-absorbing material for a battery module, comprising inorganic particle fragments as the main component, large-diameter inorganic fibers, and small-diameter fibers having an average fiber diameter of 0.2 times or less the average fiber diameter of the large-diameter inorganic fibers, wherein when the length of the long side of the inorganic particle fragment is L1 (μm) and the length of the short side is L2 (μm), the length ratio R calculated by formula L1 / L2 is 2 or more and 20 or less.

[0125] Furthermore, preferred embodiments of the present invention relating to shock-absorbing materials for battery modules are described in the following "2" to "11".

[0126] "2" The shock-absorbing material for a battery module according to "1", further comprising at least one selected from organic fibers and a binder.

[0127] "3" The shock-absorbing material for a battery module according to "1" or "2", characterized in that it has a plurality of voids on its surface and at least a portion of its interior, and at least a portion of the plurality of voids is formed around the large-diameter inorganic fiber.

[0128] "4" The shock-absorbing material for a battery module according to "3", characterized in that at least some of the large-diameter inorganic fibers penetrate the void.

[0129] "5" The shock-absorbing material for a battery module according to "3" or "4", characterized in that at least some of the ends of the large-diameter inorganic fibers protrude into the void.

[0130] "6" The shock absorber for a battery module according to any one of "1" to "5", characterized in that the inorganic particle fragments include at least one selected from boehmite, flaky silica, vermiculite, mica, plate-like alumina, wollastonite, talc, limestone, and kaolin.

[0131] "7" The shock absorber for a battery module according to any one of "1" to "6", characterized in that the large-diameter inorganic fiber includes at least one selected from glass fiber, basalt fiber, silica fiber, alumina fiber, and alkali earth silicate fiber.

[0132] "8" The shock absorber for a battery module according to any one of "1" to "7", characterized in that the small-diameter fiber includes at least one selected from cellulose fiber, sepiolite, attapulgite, and microglass fiber.

[0133] "9" The shock absorber for a battery module according to any one of "1" to "8", further comprising organic fibers, wherein the organic fibers comprise at least one selected from polyethylene terephthalate fibers, polypropylene fibers, polyethylene fibers, and polyvinyl alcohol fibers.

[0134] "10" The shock-absorbing material for a battery module according to any one of "1" to "9", further comprising organic fibers, wherein the organic fibers include organic fibers having a core-sheath structure.

[0135] "11" The shock-absorbing material for a battery module according to any one of "1" to "10", further comprising a binder, wherein the binder comprises at least one selected from acrylic resin, vinyl acetate resin, phenolic resin, silicone resin, epoxy resin, styrene-butadiene resin, silicone-acrylic resin, and styrene resin.

[0136] Furthermore, the above-mentioned objective of the present invention is achieved by the configuration of the battery module described in "12" below.

[0137] A battery module comprising: a shock-absorbing material for a battery module as described in any one of "1" to "11"; a battery cell; and a battery case for housing the shock-absorbing material for a battery module and the battery cell.

[0138] Furthermore, preferred embodiments of the present invention relating to a battery module are described in "13" to "14" below.

[0139] "13" The battery module according to "12", wherein the battery case has a top surface, side walls and a bottom wall inside, and the shock-absorbing material for the battery module is a battery pack cover attached to at least one surface selected from the top surface, side walls and bottom wall.

[0140] "14" The battery module according to "12", characterized in that the shock-absorbing material for the battery module is an inter-cell separator disposed between a plurality of battery cells.

[0141] Furthermore, the present invention also includes the following (shock-absorbing material for battery modules).

[0142] <1> The material comprises inorganic particle fragments, large-diameter inorganic fibers, small-diameter fibers having an average fiber diameter of 0.2 times or less the average fiber diameter of the large-diameter inorganic fibers, and a binder, wherein the inorganic particle fragments include at least one selected from wollastonite, talc, limestone, and kaolin, and the content of the inorganic particle fragments is 50% by mass or more and 80% by mass or less based on the total mass of the shock absorber for the battery module, the large-diameter inorganic fibers include at least one selected from glass fibers, basalt fibers, silica fibers, alumina fibers, and alkali earth silicate fibers, and the content of the large-diameter inorganic fibers is 5% by mass or more and 35% by mass or less based on the total mass of the shock absorber for the battery module, the small-diameter fibers include at least one selected from cellulose fibers, sepiolite, and attapulgite, and the content of the small-diameter fibers is 10% by mass or less based on the total mass of the shock absorber for the battery module, and the content of the binder is 5% by mass or more and 15% by mass or less based on the total mass of the shock absorber for the battery module. A shock-absorbing material for a battery module, characterized in that, when the length of the long side of the inorganic particle piece is L1 (μm) and the length of the short side is L2 (μm), the length ratio R calculated by the formula L1 / L2 is 2 or more and 20 or less.

[0143] Furthermore, preferred embodiments of the present invention relating to shock-absorbing materials for battery modules are described in the following <2> to <12>.

[0144] <2> The shock-absorbing material for battery modules according to <1>, further characterized by containing organic fibers.

[0145] <3> The shock absorber for a battery module according to <2>, characterized in that the organic fiber includes at least one selected from polyethylene terephthalate fiber, polypropylene fiber, polyethylene fiber, and polyvinyl alcohol fiber.

[0146] <4> The shock-absorbing material for a battery module according to <2>, characterized in that the organic fiber includes an organic fiber having a core-sheath structure.

[0147] <5> The shock-absorbing material for a battery module according to any one of <1> to <4>, characterized in that the binder comprises at least one selected from acrylic resin, vinyl acetate resin, styrene-butadiene resin, silicone-acrylic resin, and styrene resin.

[0148] <6> The shock-absorbing material for a battery module according to any one of <1> to <5>, characterized in that it has a plurality of voids on its surface and at least a portion of its interior, and at least a portion of the plurality of voids is formed around the large-diameter inorganic fiber.

[0149] <7> The shock-absorbing material for a battery module according to <6>, characterized in that at least some of the large-diameter inorganic fibers penetrate the void.

[0150] <8> The shock-absorbing material for a battery module according to <6> or <7>, characterized in that at least some of the ends of the large-diameter inorganic fibers protrude into the void.

[0151] <9> The shock-absorbing material for a battery module according to any one of <1> to <8>, further characterized by containing silica particles or glass particles.

[0152] <10> The shock-absorbing material for a battery module according to <9>, characterized in that the silica particles include at least one of fused silica, wet silica, and dry silica.

[0153] <11> The shock absorber for a battery module according to any one of <1> to <10>, characterized by having a matrix portion containing a thermosetting resin.

[0154] <12> The shock absorber for a battery module according to <11>, characterized in that the thermosetting resin is at least one selected from silicone resin, epoxy resin, and phenolic resin.

[0155] Furthermore, the above objective of the present invention is achieved by the following configurations <13> to <14> relating to a method for manufacturing shock-absorbing material for battery modules.

[0156] <13> A method for manufacturing a shock-absorbing material for a battery module as described in any one of <1> to <10>, comprising: a stirring step of mixing and stirring shock-absorbing material materials including inorganic particle fragments, large-diameter inorganic fibers, small-diameter fibers and a binder to prepare a mixed solution; a dehydration step of dehydrating the mixed solution to produce a wet sheet; and a drying step of drying the wet sheet.

[0157] <14> A manufacturing method for producing a shock-absorbing material for a battery module as described in <11>, comprising: a stirring step of mixing and stirring a shock-absorbing material material containing the inorganic particle fragments, the large-diameter inorganic fibers, the small-diameter fibers, and the binder to prepare a mixed solution; a dewatering step of dewatering the mixed solution to produce a wet sheet; a precursor preparation step of drying the wet sheet to produce a shock-absorbing material precursor; an impregnation step of impregnating the shock-absorbing material precursor into a matrix material containing a thermosetting resin; and a molding step of heating and pressurizing the shock-absorbing material precursor containing the matrix material to form it.

[0158] Furthermore, the above-mentioned objective of the present invention is achieved by the configuration of the battery module described in <15> below.

[0159] <15> A battery module characterized by comprising: a shock-absorbing material for a battery module as described in any one of <1> to <12>; a battery cell; and a battery case for housing the shock-absorbing material for a battery module and the battery cell.

[0160] Furthermore, preferred embodiments of the present invention relating to a battery module are described in the following <16> to <17>.

[0161] <16> The battery module according to <15>, wherein the battery case has a top surface, side walls and a bottom wall inside, and the shock-absorbing material for the battery module is a battery pack cover attached to at least one surface selected from the top surface, side walls and bottom wall.

[0162] <17> The battery module according to <15>, characterized in that the shock-absorbing material for the battery module is an inter-cell separator disposed between a plurality of battery cells.

[0163] The shock-absorbing material for battery modules of the present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0164] <Manufacturing of Shock Absorbing Material> Shock absorbing material materials with varying amounts of small-diameter fibers were mixed in water and stirred with a stirrer to prepare a mixture. Next, the mixture was dewatered by sucking water from the back of a filtration mesh to produce a wet sheet. Subsequently, the wet sheet was heated to produce sheet-shaped shock absorbing materials that would serve as the inventive example and comparative example. The shock absorbing material materials used are shown below.

[0165] Inorganic particle fragments: wollastonite; Large-diameter inorganic fibers: basalt fibers; Small-diameter fibers: sepiolite; Binder: acrylic resin

[0166] <Evaluation of Impact Absorbers> The thickness and density of each impact absorber obtained were measured. In addition, one main surface of each impact absorber was heated with a burner, and after the heated main surface reached 1200°C, an evaluation test was conducted in which alumina particles were radiated onto the main surface to evaluate its heat insulation and impact resistance. The temperature of the main surface reached 1200°C between 30 and 60 seconds after the start of heating with the burner. The evaluation test methods for each will be explained further below.

[0167] (Thermal insulation) The temperature difference ΔT between one main surface and the other main surface of the shock absorber was measured after applying a flame. A larger value of ΔT indicates better thermal insulation. In this example, materials with a temperature difference ΔT exceeding 500°C were judged to have excellent thermal insulation.

[0168] (Impact Resistance) Alumina particles were radiated onto one side of the impact absorber, and for those in which the alumina particles penetrated the impact absorber, the mass of alumina particles until penetration (blast particle amount) was measured. The blast particle amount was limited to 150 g, and the condition of the impact absorber after the alumina particles were radiated was observed. In this example, impact absorbers that showed damage (perforation) before the blast particle amount reached 150 g were judged to have poor impact resistance, while those that did not show damage were judged to have good impact resistance. The thickness and density of the impact absorber, as well as the evaluation results of its heat insulation and impact resistance, are shown in Table 1 below.

[0169]

[0170] As shown in Table 1 above, Invention Example 1 and Invention Example 2 contain sepiolite as small-diameter fibers in the impact-absorbing material. Therefore, the effect of holding inorganic particle fragments of small-diameter fibers can be sufficiently obtained, and in impact resistance evaluation tests, no damage occurred, and excellent impact resistance was obtained. Although the thermal insulation performance tends to decrease with increasing sepiolite content, both Invention Example 1 and Invention Example 2 showed good thermal insulation performance.

[0171] In contrast, Comparative Example 1, because the shock-absorbing material did not contain small-diameter fibers, had good heat insulation properties, but it could not achieve the effect of holding inorganic particle fragments, and puncture (damage) occurred with a blast particle amount of 2.5 g.

[0172] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to these examples. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these will naturally also fall within the technical scope of the present invention. Furthermore, the components of the above embodiments may be combined in any way without departing from the spirit of the invention.

[0173] This application is based on the Japanese Patent Application No. 2025-053613 filed on March 27, 2025, the Japanese Patent Application No. 2025-128869 filed on July 31, 2025, and the contents of the Japanese Patent Application No. 2025-128870 filed on July 31, 2025, and their contents are incorporated by reference in this application.

[0174] 10, 20, 30 Shock absorber 11 Inorganic particle fragments 12, 22, 32 Large-diameter inorganic fibers 13 Small-diameter fibers 14 Void 15 Binder 42a Through fibers 42b Protruding fibers 100 Battery module 110 Battery cell 111 Electrode terminal 120 Battery case 120a Top surface 120b Side wall surface 120c Bottom wall surface 130 Bus bar

Claims

1. A shock-absorbing material for a battery module, comprising inorganic particle fragments, large-diameter inorganic fibers, and small-diameter fibers having an average fiber diameter of 0.2 times or less the average fiber diameter of the large-diameter inorganic fibers, wherein when the length of the long side of the inorganic particle fragment is L1 (μm) and the length of the short side is L2 (μm), the length ratio R calculated by formula L1 / L2 is 2 or more and 20 or less.

2. The shock absorber for a battery module according to claim 1, further comprising a binder, wherein the inorganic particle fragments comprise at least one selected from wollastonite, talc, limestone, and kaolin, and the content of the inorganic particle fragments is 50% by mass or more and 80% by mass or less based on the total mass of the shock absorber for the battery module, wherein the large-diameter inorganic fibers comprise at least one selected from glass fibers, basalt fibers, silica fibers, alumina fibers, and alkali earth silicate fibers, and the content of the large-diameter inorganic fibers is 5% by mass or more and 35% by mass or less based on the total mass of the shock absorber for the battery module, wherein the small-diameter fibers comprise at least one selected from cellulose fibers, sepiolite, and attapulgite, and the content of the small-diameter fibers is 10% by mass or less based on the total mass of the shock absorber for the battery module, and the content of the binder comprises 5% by mass or more and 15% by mass or less based on the total mass of the shock absorber for the battery module.

3. The shock-absorbing material for a battery module according to claim 1, characterized in that it mainly comprises the inorganic particle fragments.

4. The shock-absorbing material for a battery module according to claim 1, further characterized by comprising at least one selected from organic fibers and a binder.

5. The shock-absorbing material for a battery module according to claim 1, characterized in that it has a plurality of voids on its surface and at least a portion of its interior, and at least a portion of the plurality of voids is formed around the large-diameter inorganic fiber.

6. The shock-absorbing material for a battery module according to claim 5, characterized in that at least some of the large-diameter inorganic fibers penetrate the void.

7. The shock-absorbing material for a battery module according to claim 5, characterized in that at least some of the ends of the large-diameter inorganic fibers protrude into the void.

8. The shock absorber for a battery module according to claim 1, characterized in that the inorganic particle fragments include at least one selected from boehmite, flaky silica, vermiculite, mica, plate-like alumina, wollastonite, talc, limestone, and kaolin.

9. The shock absorber for a battery module according to claim 1, characterized in that the large-diameter inorganic fiber includes at least one selected from glass fiber, basalt fiber, silica fiber, alumina fiber, and alkali earth silicate fiber.

10. The shock absorber for a battery module according to claim 1, characterized in that the small-diameter fibers include at least one selected from cellulose fibers, sepiolite, attapulgite, and microglass fibers.

11. The shock absorber for a battery module according to claim 1, further comprising organic fibers, wherein the organic fibers comprise at least one selected from polyethylene terephthalate fibers, polypropylene fibers, polyethylene fibers, and polyvinyl alcohol fibers.

12. The shock-absorbing material for a battery module according to claim 1, further comprising organic fibers, wherein the organic fibers include organic fibers having a core-sheath structure.

13. The shock-absorbing material for a battery module according to claim 1, further comprising a binder, wherein the binder comprises at least one selected from acrylic resin, vinyl acetate resin, phenolic resin, silicone resin, epoxy resin, styrene-butadiene resin, silicone-acrylic resin, and styrene resin.

14. The shock-absorbing material for a battery module according to claim 1, further characterized by containing silica particles or glass particles.

15. The shock-absorbing material for a battery module according to claim 14, characterized in that the silica particles include at least one of fused silica, wet silica, and dry silica.

16. The shock-absorbing material for a battery module according to claim 1, characterized by having a matrix portion containing a thermosetting resin.

17. The shock absorber for a battery module according to claim 16, characterized in that the thermosetting resin is at least one selected from silicone resin, epoxy resin, and phenolic resin.

18. A method for manufacturing a shock-absorbing material for a battery module according to any one of claims 1 to 17, comprising: a stirring step of mixing and stirring a shock-absorbing material material including the inorganic particle fragments, the large-diameter inorganic fibers, and the small-diameter fibers to prepare a mixed liquid; a dehydration step of dehydrating the mixed liquid to produce a wet sheet; and a drying step of drying the wet sheet.

19. The method for manufacturing a shock-absorbing material for a battery module according to claim 18, characterized in that the shock-absorbing material has a binder.

20. A method for manufacturing a shock-absorbing material for a battery module according to claim 16, comprising: a stirring step of mixing and stirring a shock-absorbing material material containing the inorganic particle fragments, the large-diameter inorganic fibers, the small-diameter fibers, and a binder to prepare a mixed solution; a dewatering step of dewatering the mixed solution to produce a wet sheet; a precursor preparation step of drying the wet sheet to produce a shock-absorbing material precursor; an impregnation step of impregnating the shock-absorbing material precursor into a matrix material containing a thermosetting resin; and a molding step of heating and pressurizing the shock-absorbing material precursor containing the matrix material to form it.

21. A battery module comprising: a shock-absorbing material for a battery module according to any one of claims 1 to 17; a battery cell; and a battery case for housing the shock-absorbing material for a battery module and the battery cell.

22. The battery module according to claim 21, wherein the battery case has a top surface, side walls and a bottom wall inside, and the shock-absorbing material for the battery module is a battery pack cover attached to at least one surface selected from the top surface, side walls and bottom wall.

23. The battery module according to claim 21, characterized in that the shock-absorbing material for the battery module is an inter-cell separator disposed between a plurality of battery cells.

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