Heat insulation material

Abstract

To provide a heat insulation material in use for a battery pack and excellent in heat insulation property, and high in strength and excellent in handling property in addition to the heat insulation property.SOLUTION: A heat insulation material 10 is arranged between a pair of arbitrary battery cells neighboring each other in the laminating direction in a laminate of a plurality of battery cells. The heat insulation material 10 includes heat insulation layers 20, 21 having a plurality of primary particles connected to one another to form skeletons, and having a porous structure having pores between the skeletons, a reinforcing layer 30 laminated on the heat insulation layers 20, 21 and having one or more types selected from metals and inorganic fibers, and a sheath material 40 storing the heat insulation layers 20, 21 and the reinforcing layer 30. When a direction crossing the laminating direction is an along-the-laminate direction, the size in the along-the-laminate direction of the reinforcing layer 30 is smaller than the size in the along-the-laminate direction of each of the heat insulation layers 20, 21 neighboring the reinforcing layer 30.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a thermal insulator disposed between adjacent battery cells in a battery pack that houses a plurality of battery cells, and particularly to a thermal insulator that uses a porous structure such as aerogel. [Background technology]

[0002] Hybrid vehicles and electric vehicles are equipped with battery packs containing multiple battery cells. In the battery pack, a stack of multiple battery cells is housed in a housing and secured by fastening members on both sides in the stacking direction. Heat insulating material is placed between adjacent battery cells in the stacking direction to prevent heat transfer and thermal runaway in the event of abnormal heat generation in the battery cells.

[0003] Porous structures such as silica aerogel are known as heat insulating materials. For example, Patent Document 1 describes a heat insulating material including a heat insulating layer having a porous structure and functional layers disposed on both sides of the heat insulating layer in the thickness direction and having at least one of fire resistance and radiant heat dissipation properties. Furthermore, Patent Document 2 describes a heat transfer suppressing sheet used in a battery pack in which multiple battery cells are connected, the heat transfer suppressing sheet including a pair of heat insulating materials, a heat diffusion sheet disposed between the heat insulating materials and having a higher thermal conductivity than the heat insulating materials, and a resin film that encapsulates and seals at least the heat insulating materials. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2023 / 276441 [Patent Document 2] Japanese Patent Publication No. 2023-56745 Summary of the Invention [Problem to be solved by the invention]

[0005] Insulating materials for battery packs are required to have high thermal insulation properties. Furthermore, porous structures such as aerogels are relatively flexible and brittle, so when using porous structures, it is desirable to increase the strength of the insulating material and improve its handleability. However, from the perspective of reducing the size and weight of battery packs, it is difficult to increase the thickness of the insulating material, and it is not easy to improve the insulating properties and strength while thinning the insulating material.

[0006] The present disclosure has been made in view of the above circumstances, and aims to provide a thermal insulation material that is used in a battery pack and has excellent thermal insulation properties, and also has high strength and excellent handling properties in addition to the thermal insulation properties. [Means for solving the problem]

[0007] (1) In order to solve the above-mentioned problems, the insulating material of the present disclosure is an insulating material that is arranged between any pair of adjacent battery cells in a stack of multiple battery cells in the stacking direction, and is characterized in that it comprises: an insulating layer having a porous structure in which multiple primary particles are connected to form a skeleton and which has pores between the skeleton; a reinforcing layer that is laminated on the insulating layer and has one or more types selected from metal and inorganic fibers; and an exterior material that houses the insulating layer and the reinforcing layer, wherein the direction that intersects the stacking direction is defined as the layer-side direction, and the size of the reinforcing layer in the layer-side direction is smaller than the size of the insulating layer adjacent to the reinforcing layer in the layer-side direction.

[0008] The thermal insulation material of the present disclosure has a reinforcing layer containing one or more materials selected from metal and inorganic fibers in addition to a thermal insulation layer. The reinforcing layer inhibits heat transfer, improving thermal insulation compared to a thermal insulation layer alone. The reinforcing layer also has the effect of increasing strength, depending on the material and how it is arranged. This makes it possible to realize a thermal insulation material with excellent thermal insulation and ease of handling. In this way, the reinforcing layer not only serves to reinforce thermal insulation, i.e., improve thermal insulation, but may also serve to reinforce strength, i.e., increase strength. In this specification, either or both of improved thermal insulation and improved strength are collectively referred to as the reinforcing effect.

[0009] Battery cells expand and contract during charging and discharging. Therefore, it is desirable for the insulating material disposed between the battery cells to be able to deform in response to the expansion and contraction of the battery cells and maintain its insulating properties. In this regard, according to the insulating material of the present disclosure, the size of the reinforcing layer in the layer direction is smaller than the size of the insulating layer adjacent to the reinforcing layer in the layer direction. In other words, when the insulating material is viewed from the stacking direction, the area of ​​the reinforcing layer is smaller than the area of ​​the adjacent insulating layer. This makes it less likely that the reinforcing layer will hinder the insulating layer's ability to deform in response to the expansion and contraction of the battery cells. Furthermore, because the reinforcing layer does not protrude in the layer direction relative to the insulating layer, electrical conduction and heat conduction through the reinforcing layer are suppressed. This allows the insulating material to maintain its electrical insulation and thermal insulation properties.

[0010] Incidentally, the heat insulating material described in Patent Document 1 has a pair of functional layers disposed on both sides of the heat insulating layer. Additionally, a configuration in which a radiation reflective layer is disposed between the two heat insulating layers is described. However, Patent Document 1 does not describe the sizes of the functional layer or the radiation reflective layer. Furthermore, the heat transfer suppressing sheet described in Patent Document 2 has a thermal diffusion sheet disposed between a pair of heat insulating materials to diffuse heat in the surface direction (along the layer direction). Here, the surface size of the thermal diffusion sheet is larger than that of the heat insulating material, and the thermal diffusion sheet protrudes outward beyond the heat insulating material. The protruding portion of the thermal diffusion sheet is in contact with a heat transfer member to release heat to the outside. Thus, Patent Document 2 does not include the technical idea of ​​making the thermal diffusion sheet smaller than the heat insulating material.

[0011] (2) In the above-described configuration, the reinforcing layer may be configured to include one or more selected from a metal sheet and a cloth formed from inorganic fibers. This configuration makes it easy to process the reinforcing layer to a desired size and to laminate it onto the heat insulating layer.

[0012] (3) In any of the above configurations, the reinforcing layer may include at least one of aluminum foil and glass cloth. This configuration makes it easier to achieve desired heat insulation and strength.

[0013] (4) In any of the above configurations, the reinforcing layer may have a thickness of 1 μm or more and 500 μm or less. This configuration makes it easy to make the heat insulating material thinner.

[0014] (5) In any of the above configurations, the area of ​​the reinforcing layer may be 94% or more of the area of ​​the insulating layer adjacent to the reinforcing layer when comparing the surfaces extending in the layer-side direction. This configuration makes it easy to achieve both the reinforcing effect of the insulating material and its ability to deform to conform to the battery cell.

[0015] (6) In any of the above configurations, the thickness of the heat insulating layer may be 0.5 mm or more and 5 mm or less. With this configuration, the heat insulating material can be easily made thinner.

[0016] (7) In any of the above configurations, the porous structure may be made of silica aerogel, which has a good balance between the size of its skeleton and the size of its pores and exhibits excellent heat insulating properties.

[0017] (8) In any of the above configurations, the heat insulating layer may contain one or more selected from the group consisting of a dispersant for the porous structure, infrared shielding particles, inorganic fibers, reinforcing inorganic particles, and a flame retardant.

[0018] The porous structure is poorly compatible with water and difficult to disperse. Therefore, when water is used in preparing a composition for producing a heat insulating layer or in pulverizing a porous structure, the dispersibility of the porous structure can be improved by adding a dispersant.

[0019] Insulating materials using porous structures can achieve high thermal insulation effects by suppressing mainly conduction and convection, among the three forms of heat transfer (conduction, convection, and radiation). Here, radiation is a phenomenon in which heat is transferred by electromagnetic waves, and the higher the temperature, the greater the amount of radiant energy emitted. Therefore, in high-temperature atmospheres, radiation is the primary cause of heat transfer. Therefore, if a thermal insulation layer contains, in addition to a porous structure, infrared-shielding particles that can suppress heat transfer due to radiation, it can suppress heat transfer due to radiation in addition to conduction and convection, and achieve high thermal insulation not only at room temperature but also at high temperatures of 500°C or higher.

[0020] When the insulating layer contains inorganic fibers, the mechanical strength of the insulating layer is improved and the detachment of the porous structure can be suppressed. Furthermore, when the insulating layer contains reinforcing inorganic particles, the mechanical strength of the insulating layer can be improved. Furthermore, when the insulating layer contains a flame retardant, the flame retardancy of the insulating layer, and therefore of the insulating material of the present disclosure, is improved.

[0021] (9) In any of the above configurations, the reinforcing layers may be arranged on both sides of the insulating layer in the stacking direction. With this configuration, the reinforcing effect of the insulating material can be enhanced.

[0022] (10) In any of the above configurations, two or more of the insulating layers may be arranged in the stacking direction, and the reinforcing layer may be arranged between two adjacent insulating layers, and the entire reinforcing layer may be embedded in the stack of the two insulating layers. This configuration makes it easier to maintain the electrical insulation and thermal insulation properties of the thermal insulation material. [Effects of the Invention]

[0023] The insulating material of the present disclosure has excellent insulating properties and is deformable to follow the expansion and contraction of battery cells. The insulating material of the present disclosure can increase strength and improve handleability by selecting the material and arrangement of the reinforcing layer. The insulating material of the present disclosure suppresses electrical conduction and heat conduction through the reinforcing layer. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 2 is a cross-sectional view in the thickness direction of the heat insulating material of the first embodiment. [Figure 2] This is a top view of only the first insulating layer and the reinforcing layer in the same insulating material. [Figure 3] FIG. 6 is a cross-sectional view in the thickness direction of the heat insulating material of the second embodiment. [Figure 4] FIG. 10 is a cross-sectional view in the thickness direction of a heat insulating material according to a third embodiment. [Figure 5] FIG. 10 is a cross-sectional view in the thickness direction of a heat insulating material according to a fourth embodiment. [Figure 6] FIG. 10 is a cross-sectional view in the thickness direction of the heat insulating material of the fifth embodiment. [Figure 7] FIG. 10 is a cross-sectional view in the thickness direction of the heat insulating material of the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] Hereinafter, an embodiment of the heat insulating material of the present disclosure will be described.

[0026] First Embodiment [composition] First, the configuration of the thermal insulation material of this embodiment will be described. FIG. 1 shows a cross-sectional view of the thermal insulation material of this embodiment in the thickness direction. FIG. 2 shows a top view of only the first insulating layer and intermediate reinforcing layer of the thermal insulation material. The thickness direction of the thermal insulation material (the vertical direction in FIG. 1) corresponds to the stacking direction in the stack of battery cells. The surface direction of the thermal insulation material corresponds to the side-by-side direction perpendicular to the stacking direction. As shown in FIG. 1, the thermal insulation material 10 includes a first insulating layer 20, a second insulating layer 21, an intermediate reinforcing layer 30, and an exterior material 40.

[0027] The first insulating layer 20 contains silica aerogel particles, silicon carbide particles (infrared shielding particles), glass fibers (inorganic fibers), and polyethylene oxide (PEO, dispersant). The first insulating layer 20 is a square plate measuring 100 mm in length, 100 mm in width, and 1.7 mm in thickness. The second insulating layer 21 is laminated on the top surface of the first insulating layer 20 with an intermediate reinforcing layer 30 sandwiched between them. The first insulating layer 20 and the second insulating layer 21 have the same configuration, shape, and dimensions. The intermediate reinforcing layer 30 is disposed between the first insulating layer 20 and the second insulating layer 21. The intermediate reinforcing layer 30 is made of aluminum foil. The intermediate reinforcing layer 30 is a square thin film measuring 98 mm in length, 98 mm in width, and 12 μm in thickness. As shown in Figure 2, the size of the intermediate reinforcing layer 30 in the planar direction (along the layer direction) is smaller than that of the adjacent first insulating layer 20. Specifically, the area of ​​the intermediate reinforcement layer 30 is 96% of the area of ​​the first insulation layer 20. The intermediate reinforcement layer 30 does not protrude to the outer periphery of the first insulation layer 20 and the second insulation layer 21, and is embedded in the laminate of the first insulation layer 20 and the second insulation layer 21.

[0028] The exterior material 40 is composed of a first nonwoven fabric 400 and a second nonwoven fabric 401. Both the first nonwoven fabric 400 and the second nonwoven fabric 401 are made of modified polyester and are 0.4 mm thick. The first nonwoven fabric 400 covers the bottom and side surfaces of the laminate of the first insulating layer 20 and the second insulating layer 21, and the second nonwoven fabric 401 covers the top surface of the second insulating layer 21. The planar size of the first nonwoven fabric 400 and the second nonwoven fabric 401 is slightly larger than that of the first insulating layer 20 (and the same for the second insulating layer 21), and they are thermocompression-bonded at the overlapping portion around the periphery of the laminate of the first insulating layer 20 and the second insulating layer 21. The first insulating layer 20, the second insulating layer 21, and the intermediate reinforcing layer 30 are contained in a bag-shaped closed space formed by the first nonwoven fabric 400 and the second nonwoven fabric 401.

[0029] [Action and effect] Next, the effects of the thermal insulation material of this embodiment will be described. In the thermal insulation material 10, the first and second thermal insulation layers 20 and 21 contain silica aerogel particles, and an intermediate reinforcing layer 30 made of aluminum foil is disposed between the two layers. The two thermal insulation layers 20 and 21 suppress heat conduction and convection, while the intermediate reinforcing layer 30 reflects heat, achieving high thermal insulation. The two thermal insulation layers 20 and 21 contain dispersants, infrared-shielding particles, and inorganic fibers in addition to silica aerogel particles. This can be expected to improve the dispersibility of the silica aerogel particles, provide high thermal insulation at high temperatures, improve the mechanical strength of the thermal insulation layer, and prevent the silica aerogel particles from falling off. Furthermore, the surface dimension of the intermediate reinforcing layer 30 is smaller than that of the two adjacent thermal insulation layers 20 and 21. Therefore, when the thermal insulation material 10 is disposed between battery cells, the intermediate reinforcing layer 30 is less likely to impede the ability of the thermal insulation layers 20 and 21 to deform in response to the expansion and contraction of the battery cells. Therefore, the thermal insulation material 10 deforms in response to the expansion and contraction of the battery cells, allowing excellent thermal insulation to be maintained. Furthermore, because the intermediate reinforcing layer 30 does not protrude toward the outer periphery relative to the two insulating layers 20, 21, electrical conduction and heat conduction through the intermediate reinforcing layer 30 are suppressed. This allows the electrical insulation and thermal insulation properties of the thermal insulation material 10 to be maintained. Furthermore, the thicknesses of the components that make up the thermal insulation material 10 are all relatively small. Therefore, the thermal insulation material 10 can be made thinner, making it suitable for reducing the size and weight of the battery pack.

[0030] Second Embodiment The difference between the insulating material of this embodiment and the insulating material of the first embodiment is that the insulating layer is combined into one, with reinforcing layers disposed on both sides of it. Here, the differences will be mainly explained. Figure 3 shows a cross-sectional view of the insulating material of this embodiment in the thickness direction. In Figure 3, components corresponding to those in Figure 1 are designated by the same reference numerals. As shown in Figure 3, the insulating material 11 includes an insulating layer 22, a lower reinforcing layer 31, an upper reinforcing layer 32, and an exterior material 40.

[0031] The insulating layer 22 is in the shape of a square plate measuring 100 mm in length, 100 mm in width, and 3.4 mm in thickness. The configuration of the insulating layer 22 is the same as that of the two insulating layers 20, 21 of the first embodiment. The lower reinforcing layer 31 is laminated on the lower surface of the insulating layer 22. The upper reinforcing layer 32 is laminated on the upper surface of the insulating layer 22. The lower reinforcing layer 31 and the upper reinforcing layer 32 are both made of aluminum foil of the same size as the intermediate reinforcing layer 30 of the first embodiment. The planar size of the lower reinforcing layer 31 and the upper reinforcing layer 32 is smaller than that of the insulating layer 22. In other words, the lower reinforcing layer 31 and the upper reinforcing layer 32 do not protrude outward from the outer periphery of the insulating layer 22.

[0032] The thermal insulation material 11 of this embodiment has the same effects as the thermal insulation material 10 of the first embodiment in the parts that share the same configuration. The thermal insulation material 11 has improved thermal insulation properties because it has two reinforcing layers 31 and 32. In addition, the thermal insulation layer 22 is thick as a single layer, which increases the strength of the thermal insulation material 11 and improves its handleability.

[0033] Third Embodiment The difference between the thermal insulation material of this embodiment and the thermal insulation material of the second embodiment is that the material and arrangement of the reinforcing layer have been changed. Here, the differences will be mainly explained. Figure 4 shows a cross-sectional view of the thermal insulation material of this embodiment in the thickness direction. In Figure 4, components corresponding to those in Figure 3 are designated by the same reference numerals. As shown in Figure 4, the thermal insulation material 12 includes a thermal insulation layer 22, a lower reinforcing layer 33, and an exterior material 40.

[0034] The lower reinforcing layer 33 is laminated on the lower surface of the insulating layer 22. The lower reinforcing layer 33 is made of a glass net. The lower reinforcing layer 33 is in the shape of a square thin plate with a length of 98 mm, a width of 98 mm, and a thickness of 300 μm. The size of the lower reinforcing layer 33 in the planar direction is smaller than that of the insulating layer 22. Specifically, the area of ​​the lower reinforcing layer 33 is 96% of the area of ​​the insulating layer 22. The lower reinforcing layer 33 does not protrude outward from the outer periphery of the insulating layer 22.

[0035] The insulating material 12 of this embodiment has the same effects as the insulating material 10 of the first embodiment and the insulating material 11 of the second embodiment in the parts that share the same configuration. According to the insulating material 12, a lower reinforcing layer 33 made of glass net is arranged. Since the strength of the glass net is relatively high, it is effective in increasing the strength of the insulating material 12 and improving its handleability. In addition, the glass net has a mesh-like shape and is flexible. Therefore, the ability of the insulating layer 22 to conform to the battery cell is not easily hindered.

[0036] <Fourth embodiment> The difference between the insulating material of this embodiment and the insulating material of the first embodiment is that a reinforcing layer has been added. Here, the differences will be mainly explained. Figure 5 shows a cross-sectional view of the insulating material of this embodiment in the thickness direction. In Figure 5, components corresponding to those in Figure 1 are designated by the same reference numerals. As shown in Figure 5, the insulating material 13 includes a first insulating layer 20, a second insulating layer 21, an intermediate reinforcing layer 30, a lower reinforcing layer 33, an upper reinforcing layer 34, and an exterior material 40.

[0037] The lower reinforcing layer 33 is laminated on the lower surface of the first insulation layer 20. The planar size of the lower reinforcing layer 33 is smaller than that of the first insulation layer 20. That is, the lower reinforcing layer 33 does not protrude toward the outer periphery of the first insulation layer 20. The upper reinforcing layer 34 is laminated on the upper surface of the second insulation layer 21. The planar size of the upper reinforcing layer 34 is smaller than that of the second insulation layer 21. That is, the upper reinforcing layer 34 does not protrude toward the outer periphery of the second insulation layer 21. Both the lower reinforcing layer 33 and the upper reinforcing layer 34 are made of glass nets of the same size as the lower reinforcing layer 33 of the third embodiment.

[0038] The insulating material 13 of this embodiment has the same effects as the insulating material 10 of the first embodiment in the parts that share the same configuration. According to the insulating material 13, a lower reinforcing layer 33 and an upper reinforcing layer 34 made of glass net are arranged in addition to the intermediate reinforcing layer 30. This not only improves the insulating properties but also increases the strength of the insulating material 13 and improves its handleability.

[0039] Fifth Embodiment The difference between the insulating material of this embodiment and the insulating material of the first embodiment is that the reinforcing layer is a laminate of two layers. Here, the differences will be mainly explained. Figure 6 shows a cross-sectional view of the insulating material of this embodiment in the thickness direction. In Figure 6, components corresponding to those in Figure 1 are designated by the same reference numerals. As shown in Figure 6, the insulating material 14 includes a first insulating layer 20, a second insulating layer 21, an intermediate reinforcing layer 35, and an exterior material 40.

[0040] The intermediate reinforcing layer 35 is disposed between the first insulation layer 20 and the second insulation layer 21. The intermediate reinforcing layer 35 is composed of a laminate in which a first reinforcing layer 350 and a second reinforcing layer 351 are stacked in the thickness direction. The first reinforcing layer 350 is disposed on the first insulation layer 20 side (lower side). The first reinforcing layer 350 is composed of a glass net of the same size as the lower reinforcing layer 33 in the third embodiment. The second reinforcing layer 351 is disposed on the second insulation layer 21 side (upper side). The second reinforcing layer 351 is composed of aluminum foil of the same size as the intermediate reinforcing layer 30 in the first embodiment. The planar size of the first reinforcing layer 350 is the same as the planar size of the second reinforcing layer 351. The planar size of the intermediate reinforcing layer 35 is smaller than that of the adjacent first insulation layer 20 and second insulation layer 21. The intermediate reinforcing layer 35 does not protrude outward from the outer periphery of the first insulation layer 20 and second insulation layer 21, but is embedded in the laminate of the first insulation layer 20 and second insulation layer 21.

[0041] The thermal insulation material 14 of this embodiment has the same effects as the thermal insulation material 10 of the first embodiment in the parts that share the same configuration. In the thermal insulation material 14, the intermediate reinforcing layer 35 is composed of a laminate of two layers with different properties. This allows the properties of both the glass net that is the first reinforcing layer 350 and the aluminum foil that is the second reinforcing layer 351 to be exhibited, thereby achieving the effects of both improved thermal insulation and improved handleability.

[0042] Sixth Embodiment The difference between the insulating material of this embodiment and the insulating material of the second embodiment is that the lower reinforcing layer is a two-layer laminate. Here, the difference will be mainly explained. Figure 7 shows a cross-sectional view of the insulating material of this embodiment in the thickness direction. In Figure 7, components corresponding to those in Figure 3 are designated by the same reference numerals. As shown in Figure 7, the insulating material 15 includes an insulating layer 22, a lower reinforcing layer 36, an upper reinforcing layer 32, and an exterior material 40.

[0043] The lower reinforcing layer 36 is composed of a laminate in which a first reinforcing layer 360 and a second reinforcing layer 361 are laminated in the thickness direction. The first reinforcing layer 360 is arranged on the first nonwoven fabric 400 side (lower side). The first reinforcing layer 360 is made of aluminum foil of the same size as the intermediate reinforcing layer 30 in the first embodiment. The second reinforcing layer 361 is arranged on the insulating layer 22 side (upper side). The second reinforcing layer 361 is made of glass net of the same size as the lower reinforcing layer 33 in the third embodiment. The planar size of the first reinforcing layer 360 is the same as the planar size of the second reinforcing layer 361. The planar size of the lower reinforcing layer 36 is smaller than that of the adjacent insulating layer 22. The lower reinforcing layer 36 does not protrude outward from the outer periphery of the insulating layer 22.

[0044] The insulating material 15 of this embodiment has the same effects as the insulating material 10 of the first embodiment and the insulating material 11 of the second embodiment in the parts that share the same configuration. In the insulating material 12, the lower reinforcing layer 36 is composed of a laminate of two layers with different properties. This allows the properties of both the aluminum foil that is the first reinforcing layer 360 and the glass net that is the second reinforcing layer 361 to be exhibited, achieving the effects of both improved thermal insulation and improved handleability.

[0045] <Other forms> Six embodiments of the heat insulating material of the present disclosure have been described above. However, the embodiments are not limited to the above embodiments. Various modifications and improvements that can be made by those skilled in the art are also possible.

[0046] [Insulation material usage] The insulating material of the present disclosure is used in a battery pack in which multiple battery cells are arranged in a predetermined direction. The type of battery cell is not particularly limited. Examples include lithium-ion batteries and nickel-metal hydride batteries. The arrangement of the insulating material of the present disclosure and its size relative to the battery cells are not particularly limited. The insulating material of the present disclosure may be arranged between adjacent battery cells in the stacking direction, or between battery cells at both ends of the stacking direction and fastening members. The thickness of the insulating material may be determined appropriately taking into account the arrangement space, ensuring insulation between battery cells, and other factors. For example, from the perspective of achieving a slim design, a thickness of 8 mm or less is desirable, and even 5 mm or less is desirable. On the other hand, from the perspective of ensuring sufficient spacing between adjacent battery cells via the insulating material during cell expansion, a thickness of 1 mm or more is desirable, and even 2 mm or more is desirable. The insulating material's size, such as its thickness, may vary depending on its location in the battery pack.

[0047] [Insulation composition] (1) Heat insulating layer The heat insulating layer has a porous structure in which multiple primary particles are linked to form a skeleton and pores are formed between the skeletons. The diameter of the primary particles forming the skeleton is preferably approximately 2 to 5 nm, and the size of the pores formed between the skeletons is preferably approximately 10 to 50 nm. If most of the pores are so-called mesopores with a size of 50 nm or less, the mesopores are smaller than the mean free path of air, restricting air convection and impeding heat transfer. The shape of the porous structure is not particularly limited, and may be spherical or irregularly shaped, lumpy, or the like. The type of porous structure is not particularly limited. Examples of primary particles include silica, alumina, zirconia, and titania. Among these, silica aerogels in which the primary particles are silica, i.e., multiple silica fine particles linked to form a skeleton, are preferred because of their excellent chemical stability and the ease with which a well-balanced skeleton size and pore size can be obtained. Aggregate structures in which multiple fumed silica fine particles are linked to form a skeleton are also suitable.

[0048] The method for producing silica aerogel is not particularly limited, and the drying process may be performed under normal pressure or under supercritical conditions. Depending on the drying method used in producing the aerogel, aerogels dried under normal pressure may be called "xerogels," those dried under supercritical conditions may be called "aerogels," and those freeze-dried may be called "cryogels." In this specification, these are collectively referred to as "aerogels."

[0049] In addition to the porous structure, the thermal insulation layer may contain other components, such as a dispersant for the porous structure, infrared-shielding particles, inorganic fibers, reinforcing inorganic particles, a flame retardant, and a binder to bind the components. The dispersant improves the dispersibility of the porous structure when water is used during the preparation of the composition for producing the thermal insulation layer or the grinding process of the porous structure. Dispersants include surfactants and water-soluble oligomers with both polar and nonpolar moieties in their side chains. Surfactants include ionic surfactants (cationic surfactants, anionic surfactants, and amphoteric surfactants) and nonionic surfactants. For example, the use of ionic surfactants can increase the viscosity of the composition even in relatively small amounts and stabilize the dispersion of materials such as the porous structure in the composition. Ionic surfactants include sodium carboxymethylcellulose (CMC-Na), polycarboxylic acid amine salts, polycarboxylic acid ammonium salts, polycarboxylic acid sodium salts, and TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl)-oxidized cellulose nanofibers (CNF-Na). The use of nonionic surfactants makes it easier for materials such as porous structures to be incorporated into the solvent when preparing the composition. They also make it easier for these materials to be redispersed when they aggregate or separate in the composition, and they also make it easier for the solvent to be expelled during pressure molding. Examples of nonionic surfactants include polyethylene oxide (PEO) and polyvinyl alcohol (PVA).

[0050] Infrared-shielding particles absorb heat from a heat source and re-emit it from the surface of the heat source, thereby blocking radiant heat from the heat source and contributing to improved insulation, especially at high temperatures. Examples include particles of silicon carbide, kaolinite, silicon nitride, mica, alumina, zirconia, aluminum nitride, zirconium silicate, cerium oxide, boron carbide, manganese oxide, tin oxide, and iron oxide. Inorganic fibers are physically entangled around the porous structure, improving the mechanical strength of the insulating layer and preventing the porous structure from falling off. Suitable examples include ceramic fibers such as glass fiber and alumina fiber. Reinforcing inorganic particles also improve the mechanical strength of the insulating layer. Examples of suitable particles include precipitated silica, gel silica, fused silica, wollastonite, potassium titanate, magnesium silicate, glass flake, calcium carbonate, and barium sulfate, which have relatively high hardness and a large specific surface area. Known flame retardants, such as halogen-based, phosphorus-based, and metal hydroxide-based flame retardants, may be used. Considering the environmental impact, it is desirable to use a phosphorus-based flame retardant. Examples of phosphorus-based flame retardants include ammonium polyphosphate, red phosphorus, and phosphate esters. Examples of binders include inorganic binders such as colloidal silica and aqueous emulsion binders.

[0051] The heat insulating layer can be produced by placing a composition containing a porous structure powder and, if necessary, other components in a mold and pressurizing it. Alternatively, the heat insulating layer can be produced by applying a slurry-like composition containing a porous structure powder and, if necessary, other components mixed with a solvent such as water to a substrate (including an exterior material) and drying it. When pressurizing, if the applied load is small and the voids between the particles of the porous structure are large, heat transfer due to air convection may increase, potentially reducing the heat insulating properties of the heat insulating layer. Conversely, if the applied load is large and the voids between the particles of the porous structure are small, the heat insulating layer may become hard and its conformability may decrease. For example, the pressure during pressurization should be 0.1 MPa or more and 20 MPa or less. Pressurization can be performed at room temperature or with heating. For example, if the pressurization also serves to dry the composition, it should be performed at a temperature of 100°C or more and 160°C or less.

[0052] The number of insulating layers constituting the insulating material may be one or more. The total thickness of the insulating layers in the stacking direction may be determined appropriately taking into consideration the distance between the battery cells, the configuration and arrangement of the reinforcing layers, etc. For example, from the viewpoint of thermal insulation, it is desirable to set the thickness to 0.5 mm or more, and even 1 mm or more. From the viewpoint of thinning the insulating material and increasing its flexibility, it is desirable to set the thickness to 5 mm or less, and even 3 mm or less.

[0053] (2) Reinforcement layer The reinforcing layer is laminated on the insulating layer. The reinforcing layer may be arranged on only one side or both sides of the insulating layer. The number of reinforcing layers constituting the insulating material may be one or two or more. For example, two or more reinforcing layers may be arranged in the stacking direction. Furthermore, one reinforcing layer may be divided into multiple segments and arranged side by side in the layer-wise direction that intersects the stacking direction. One reinforcing layer may be composed of one layer, or a laminate of two or more layers made of different materials. Examples of the latter laminate include a laminate of glass net and aluminum foil shown in the fifth and sixth embodiments, as well as a metallized film in which metal is vapor-deposited on the surface of a resin film.

[0054] The size of the reinforcing layer in the layer-side direction is smaller than the size of the adjacent insulating layer in the layer-side direction. For example, when two or more insulating layers are arranged in the stacking direction and the reinforcing layer is arranged between two adjacent insulating layers, it is desirable that the entire reinforcing layer be embedded in the stack of the two insulating layers. When comparing surfaces extending in the layer-side direction, from the perspective of increasing the reinforcing effect of the insulating material, it is desirable that the area of ​​the reinforcing layer be 94% or more of the area of ​​the adjacent insulating layer. On the other hand, considering the ability to conform to the battery cell, electrical conductivity through the reinforcing layer, and suppression of heat conduction, it is desirable that the area of ​​the reinforcing layer be 98% or less of the area of ​​the adjacent insulating layer.

[0055] The thickness of each reinforcing layer may be determined appropriately taking into consideration the reinforcing effect of the heat insulating material, thinning of the heat insulating material, flexibility, etc. For example, from the viewpoint of increasing the reinforcing effect, it is desirable to set the thickness to 1 μm or more, and even 5 μm or more. From the viewpoint of thinning of the heat insulating material and increasing its flexibility, it is desirable to set the thickness to 500 μm or less, 300 μm or less, or even 40 μm or less.

[0056] The reinforcing layer contains one or more materials selected from metals and inorganic fibers. When the reinforcing layer contains a metal with a relatively low emissivity, the reinforcing layer reflects heat and suppresses heat transfer, which is effective in improving thermal insulation. Examples of metals with a relatively low emissivity include aluminum, aluminum compounds, magnesium, magnesium compounds, silver, titanium, titanium compounds, tin, gold, and copper. Furthermore, when inorganic fibers are contained, the strength of the insulating material increases, which is effective in improving handleability. Examples of inorganic fibers include glass fiber, alumina fiber, silica fiber, refractory ceramic fiber (RCF), polycrystalline alumina fiber (Polycrystalline Wool: PCW), alkaline earth silicate (AES) fiber, rock wool, carbon fiber, and metal fiber.

[0057] The reinforcing layer may be in the form of a dense sheet or a mesh having voids. For example, a metal sheet or a cloth made of inorganic fibers is suitable. Examples of the metal sheet include aluminum foil and aluminum-deposited film. Examples of the cloth made of inorganic fibers include woven fabric and nonwoven fabric, such as glass cloth, glass fiber nonwoven fabric, and aluminum-glass cloth. The glass net used in the third embodiment is included in the glass cloth.

[0058] (3) Exterior materials The exterior packaging material accommodates the insulating layer and the reinforcing layer. The exterior packaging material may be composed of a single substrate or a combination of two or more substrates. For example, a laminate of the insulating layer and the reinforcing layer may be wrapped in a single substrate, or two substrates may be arranged sandwiching the laminate. The entire insulating layer and the reinforcing layer do not necessarily have to be covered with the exterior packaging material. Also, an adhesive layer may be interposed between the exterior packaging material and the laminate of the insulating layer and the reinforcing layer. The adhesive layer may contain a flame retardant in addition to adhesive components.

[0059] Examples of materials for the exterior material (substrate) include cloth, resin, and paper. Examples of the form of the exterior material include woven fabric, nonwoven fabric, and sheet. For example, fabrics (woven fabrics) and nonwoven fabrics made from inorganic fibers such as glass fiber and metal fiber, and fire-resistant insulating paper made as a composite of pulp and magnesium silicate, have relatively low thermal conductivity and high shape retention even in high-temperature environments. Among these, glass fiber nonwoven fabric, glass cloth, aluminum glass cloth, AES wool paper, and polyimide fiber nonwoven fabric are highly heat-resistant and suitable.

[0060] [Insulation material manufacturing method] The method for producing the heat insulating material of the present disclosure is not particularly limited. For example, a heat insulating layer and a reinforcing layer that have been prepared separately may be laminated and housed in an exterior packaging material. Alternatively, a laminate obtained by laminating a composition for producing the heat insulating layer and a reinforcing layer and press-molding the laminate may be housed in an exterior packaging material. Alternatively, a laminate of a composition for producing the heat insulating layer and a reinforcing layer may be housed in an exterior packaging material and press-molded. [Example]

[0061] Next, the present disclosure will be described more specifically with reference to examples. Heat insulating material samples of the forms shown in the first to sixth embodiments were produced, and their heat insulating properties and handling properties were evaluated.

[0062] <Production of insulation samples> [Production of composition for heat insulating layer] First, 69 parts by mass of silica aerogel powder, 20 parts by mass of silicon carbide powder as infrared shielding particles, 8 parts by mass of inorganic glass fiber, and 3 parts by mass of PEO as a dispersant were added to a mixer and stirred for 1 minute. While continuing to stir, water was added to achieve a solids content of 40-50%. This was then further stirred and mixed for 45 minutes to produce a clay-like composition. The details of the materials used are as follows: Silica aerogel powder: Ground "Aerogel Particles P200" manufactured by Cabot Corporation, average particle size 100 μm. Silicon carbide powder: Fuji Random GC #4000 manufactured by Fuji Manufacturing Co., Ltd., average particle size 5 μm. Glass fiber: "Wet Chop" manufactured by Nippon Electric Glass Co., Ltd., length 3 mm, filament diameter 6.5 μm. PEO: Polyethylene oxide "PEO-8" manufactured by Sumitomo Seika Chemicals Co., Ltd., viscosity average molecular weight 1.7 million to 2.2 million.

[0063] [Pressure molding] First, a first nonwoven fabric made of modified polyester was placed in a box-shaped preforming mold as an exterior material. Next, the obtained composition and separately prepared aluminum foil and glass netting as reinforcing layers were placed inside the first nonwoven fabric in various configurations corresponding to the first to sixth embodiments, and preforming was performed by applying pressure from above to a predetermined thickness. Next, a second nonwoven fabric made of modified polyester as an exterior material was placed to cover the upper surface of the preform, and the overlapping portion between the first and second nonwoven fabrics was fused to surround the periphery of the preform. Finally, the preform housed in the exterior material was hot-pressed at a temperature of 150°C and a pressure of 20 MPa. In this manner, nine types of insulation samples were produced. These are hereinafter referred to as samples of Examples 1 to 9. The surface dimensions of the insulation layer in the samples of Examples 1 to 9 were 80 mm long and 80 mm wide, unlike those of the first to sixth embodiments. Correspondingly, the surface dimensions of the reinforcing layer were also set to 78.4 mm in length and 78.4 mm in width so that the area was 96% of the area of ​​the heat insulating layer. The thickness of each layer was the same as in the first to sixth embodiments.

[0064] Table 1 shows the type and arrangement of the reinforcing layer in the samples of Examples 1 to 9 in a format corresponding to the first to sixth embodiments. For comparison, an insulating material sample with only an insulating layer without a reinforcing layer was manufactured in the same manner as the samples of the Examples, and is shown in Table 1 as a sample of Comparative Example 1. The configuration of the insulating layer in the sample of Comparative Example 1 is the same as that of the insulating layer in the samples of the Examples, and the size of the insulating layer is the same as that of the insulating layer in the sample of Example 3, which has only one insulating layer (a square plate measuring 80 mm in length, 80 mm in width, and 3.4 mm in thickness). [Table 1]

[0065] <Evaluation of insulation samples> [Thermal insulation] The thermal insulation properties of the insulation material sample were evaluated using an insulation property evaluation device equipped with a pressure mechanism and a plate-shaped heater as follows. First, the heater in the insulation property evaluation device was heated to 800°C. Next, the insulation material sample was placed below the plate-shaped heater, and an aluminum dummy cell with a thickness of 25 mm and a mass of 430 g was placed below that. The heater, insulation material sample, and dummy cell all had the same surface dimensions. A heating-side thermocouple was attached to the heater, and a heat-receiving-side thermocouple was attached to the dummy cell. Next, power to the heater was stopped, and a pressure of 0.15 MPa was applied from above the heater to begin measuring the heater temperature (heating-side temperature) and the dummy cell temperature (heat-receiving-side temperature). Temperature measurements were continued until the dummy cell temperature reached saturation, and the maximum temperature reached by the dummy cell was recorded. The lower the maximum temperature reached by the dummy cell, the higher the insulation properties of the insulation material sample. The insulation material samples were placed with the upper side facing the heater as shown in each embodiment, but for samples of Examples 5 and 6 (corresponding to the third embodiment), in which the reinforcing layer was placed on only one side (lower side) of the insulation layer, the lower reinforcing layer side was placed on the heater side.

[0066] [Bending strength] A three-point bending test was conducted on insulation samples using a 1 kN compression-tensile testing machine. This test used samples that differed only in their surface dimensions from the previously manufactured insulation samples. The surface dimensions of the insulation layer in the sample used were 100 mm long and 250 mm wide, and the surface dimensions of the reinforcing layer were 98 mm long and 246 mm wide. The area of ​​the reinforcing layer was 96% of the area of ​​the insulation layer. The three-point bending test was conducted in accordance with JIS K7171:2022. A load was applied from above the sample at a support distance of 150 mm and a test speed of 100 mm / min, and the displacement (deflection) relative to the load was measured. In the obtained load-deflection diagram, the load at which the sample buckled was defined as the "initial cracking load." The maximum slope of the curve up to the initial cracking load was calculated and used as the bending strength (N / mm) of the sample. The higher the bending strength of a sample, the better its handleability is evaluated.

[0067] [Evaluation results] The evaluation results of the insulation samples are summarized in Table 1 above. As shown in Table 1, the samples of Examples 1 to 9, which had a reinforcing layer, all had lower maximum temperatures in the dummy cells (heat-receiving side) compared to the sample of Comparative Example 1, which did not have a reinforcing layer, confirming improved insulation. In particular, the sample of Example 3, in which aluminum foil was used as a reinforcing layer and it was arranged on both sides of the insulation layer, showed a greater improvement in insulation. It was also confirmed that using a glass net as a reinforcing layer increased bending strength and improved handleability. Furthermore, using both aluminum foil and a glass net as reinforcing layers, as in the samples of Examples 7 to 9, was effective in improving both insulation and handleability. Of these, the sample of Example 7, in which aluminum foil was arranged between two insulation layers and a glass net was arranged on the outside of each insulation layer, showed a particularly significant improvement in handleability. [Explanation of symbols]

[0068] 10, 11, 12, 13, 14, 15: insulation material, 20: first insulation layer, 21: second insulation layer, 22: insulation layer, 30: intermediate reinforcing layer, 31: lower reinforcing layer, 32: upper reinforcing layer, 33: lower reinforcing layer, 34: upper reinforcing layer, 35: intermediate reinforcing layer, 350: first reinforcing layer, 351: second reinforcing layer, 36: lower reinforcing layer, 360: first reinforcing layer, 361: second reinforcing layer, 40: exterior material, 400: first nonwoven fabric, 401: second nonwoven fabric.

Claims

1. A thermal insulator disposed between any pair of adjacent battery cells in a stack of a plurality of battery cells, a heat insulating layer having a porous structure in which a plurality of primary particles are connected to form a skeleton and pores are formed between the skeletons; a reinforcing layer laminated on the heat insulating layer and having one or more types selected from metal and inorganic fibers; an exterior material that accommodates the heat insulating layer and the reinforcing layer; Equipped with An insulating material characterized in that the direction intersecting the stacking direction is the layer direction, and the size of the reinforcing layer in the layer direction is smaller than the size of the insulating layer adjacent to the reinforcing layer in the layer direction.

2. The heat insulating material according to claim 1 , wherein the reinforcing layer comprises at least one material selected from the group consisting of a metal sheet and a fabric made of inorganic fibers.

3. The heat insulating material according to claim 1 , wherein the reinforcing layer comprises at least one of aluminum foil and glass cloth.

4. 2. The heat insulating material according to claim 1, wherein the reinforcing layer has a thickness of 1 μm or more and 500 μm or less.

5. 2. The insulating material according to claim 1, wherein the area of ​​the reinforcing layer is 94% or more of the area of ​​the insulating layer adjacent to the reinforcing layer when comparing the surfaces extending in the layer-wise direction.

6. The heat insulating material according to claim 1, wherein the thickness of the heat insulating layer is 0.5 mm or more and 5 mm or less.

7. The heat insulating material according to claim 1 , wherein the porous structure is silica aerogel.

8. The heat insulating material according to claim 1 , wherein the heat insulating layer comprises at least one selected from the group consisting of a dispersant for the porous structure, infrared shielding particles, inorganic fibers, reinforcing inorganic particles, and a flame retardant.

9. The thermal insulation material according to claim 1 , wherein the reinforcing layers are arranged on both sides of the thermal insulation layer in the stacking direction.

10. Two or more heat insulating layers are arranged in the stacking direction, 2. The thermal insulation material according to claim 1, wherein the reinforcing layer is disposed between two adjacent thermal insulation layers, and the entire reinforcing layer is embedded in the stack of the two thermal insulation layers.

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