JP7724662B2 - Heat insulating elastic material - Google Patents

Description

This disclosure relates to a heat-insulating elastic member that is placed between adjacent battery cells in a battery pack that houses multiple battery cells.

Hybrid and electric vehicles are equipped with battery packs containing multiple battery cells. In a battery pack, a battery module consisting of multiple stacked battery cells is housed in a housing and secured with fastening members on both sides in the stacking direction. If the temperature of one battery cell rises for some reason, this heat can be transferred to adjacent battery cells, potentially causing a serious thermal chain reaction. Therefore, thermal chain reaction is prevented by, for example, placing insulating material between adjacent battery cells.

For example, Patent Document 1 describes a multilayer sheet placed between adjacent battery cells. As shown in Figure 3 of Patent Document 1, the multilayer sheet is formed by stacking a first thermally conductive sheet, a heat insulating sheet, a rubber sheet, a heat insulating sheet, and a first thermally conductive sheet in the thickness direction. The first thermally conductive sheet is made of a material such as a metal with high thermal conductivity, and has a heat dissipation function. Patent Document 2 describes a partition member placed between adjacent battery cells. The partition member has a base material that melts when the temperature rises, and a spacer made of thermosetting resin embedded in the base material.

Japanese Patent Application Laid-Open No. 2021-99940 JP 2010-97693 A

The insulating performance of an insulating material can be improved by increasing its thickness. However, when placing it in the limited space between battery cells inside a battery pack, the thickness of the insulating material needs to be as small as possible. For this reason, insulating materials are required to be both thin and have insulating performance.

In addition to the insulation, rubber buffer material may be interposed between adjacent battery cells to prevent misalignment of the battery cells due to vibrations while the vehicle is in motion and to accommodate expansion and contraction of the battery cells during charging and discharging. In this case, the insulation and buffer material are layered between the battery cells. For example, if the temperature of the battery cells rises and reaches high temperatures of several hundred degrees Celsius, the rubber buffer material may melt or disappear. If the buffer material disappears, the battery cells, which generate heat and expand, come into contact with the insulation, narrowing the gap between the battery cells that is normally maintained by the insulation and buffer material. As the gap between the battery cells narrows, the insulating effect decreases accordingly. If heat transfer must be suppressed solely by the insulation material in this state, there is a limit to its insulating performance without changing the thickness or material. Furthermore, if the molten rubber material adheres to components responsible for heat dissipation, such as cooling pipes, in the battery pack, it may impair the cooling function.

The multilayer sheet described in Patent Document 1 also includes a rubber sheet. However, in this multilayer sheet, insulating sheets are disposed on both thicknesswise sides of the rubber sheet. Here, the rubber sheet and the insulating sheet are the same size. That is, both thicknesswise sides of the rubber sheet are covered with the insulating sheet. Furthermore, first thermally conductive sheets with excellent heat dissipation properties are disposed on both thicknesswise sides of the insulating sheet. Therefore, even if the temperature of the battery cells increases, heat is not easily transferred to the rubber sheet. As described in paragraph [0036] of Patent Document 1, "It is preferable that the rubber sheet 13 be made of a material with high heat resistance so that it can maintain its shape without melting or decomposing due to the heat transmitted through the first thermally conductive sheet 11 and the insulating sheet 12." As described above, melting of the rubber sheet is not anticipated in the multilayer sheet. On the other hand, in the partition member described in Patent Document 2, the base material is formed from wax or the like, and melts as the temperature of the battery cells increases. As described in paragraph [0007] of Patent Document 2, the partition member suppresses heat transfer between battery cells by utilizing the heat of fusion generated when the base material melts. The spacers embedded in the base material remain between the battery cells even after the base material melts, maintaining the distance between the battery cells. However, the spacers are made of thermosetting resin, and their flame retardancy and thermal conductivity have not been taken into consideration. Therefore, simply placing spacers between battery cells does not provide sufficient insulation performance.

This disclosure was made in light of these circumstances, and aims to provide an insulating elastic member that can suppress heat transfer between battery cells by ensuring a gap between adjacent battery cells and allowing the insulating properties of the insulating sheet to be exerted, even when the temperature of a battery cell rises.

In order to solve the above problems, the insulating elastic member disclosed herein is an insulating elastic member placed between adjacent battery cells, and is characterized by comprising an insulating sheet, a plurality of elastomers arranged at predetermined intervals on one side of the insulating sheet, and a regulator arranged on one side of the insulating sheet at least between the elastomers, the regulator being made of a material different from the elastomers, having flame retardancy, and having thermal conductivity equal to or less than that of the elastomers.

In the heat-insulating elastic member of the present disclosure, multiple elastic bodies and a regulator are arranged on one side of the heat-insulating sheet. The elastic bodies have cushioning properties and serve to prevent misalignment of the battery cells when the vehicle is running, and to absorb deformation due to expansion and contraction of the battery cells during charging and discharging. The regulators are arranged between the elastic bodies. The regulators are made of a material different from the elastic bodies and are flame-retardant. Therefore, even if the temperature of the battery cells rises and the elastic bodies melt, the regulators remain, thereby suppressing expansion of the battery cells and maintaining the spacing between the battery cells and between the battery cells and the heat-insulating sheet. In addition, because the thermal conductivity of the regulators is the same as or lower than that of the elastic bodies, a heat-insulating effect can also be expected from the regulators. By interposing the regulators in this way, the spacing between the battery cells is maintained and the heat-insulating effect of the regulators and the heat-insulating sheet can be fully exerted.

Therefore, the insulating elastic member of the present disclosure can suppress heat transfer between adjacent battery cells without increasing the thickness of the insulating sheet or increasing the amount of insulating material. This allows for cost reduction. Furthermore, even if the insulating sheet is prone to bending and has poor self-supporting properties, the regulating body acts as a skeleton, allowing the insulating elastic member as a whole to exhibit self-supporting properties. As a result, workability during assembly can be improved. Furthermore, by arranging the regulating body below the elastic body or arranging it in a frame shape around the elastic body, it is possible to suppress the outflow of molten elastic body. This prevents the molten elastic body from adhering to components responsible for heat dissipation, such as cooling pipes, arranged in the battery pack.

1 is a cross-sectional schematic view of a battery pack in which a heat-insulating elastic member according to a first embodiment is disposed. FIG. FIG. 2 is a perspective view of the heat insulating elastic member of the first embodiment. FIG. 3 is a cross-sectional view of the heat insulating elastic member in the thickness direction. FIG. 10 is a perspective view of a heat insulating elastic member according to a second embodiment. FIG. 3 is a cross-sectional view of the heat insulating elastic member in the thickness direction. FIG. 10 is a perspective view of a heat insulating elastic member according to a third embodiment. FIG. 3 is a cross-sectional view of the heat insulating elastic member in the thickness direction.

First Embodiment
[composition]
First, the configuration of the insulating elastic member of the first embodiment will be described. FIG. 1 shows a cross-sectional schematic diagram of a battery pack in which the insulating elastic member of the first embodiment is disposed. FIG. 2 shows a perspective view of the insulating elastic member of the first embodiment. FIG. 3 shows a cross-sectional view taken along line III-III of FIG. 2 (a cross-sectional view of the insulating elastic member in the thickness direction). Regarding the orientation in the figure, the arrangement direction of the battery cells (thickness direction of each component, stacking direction) is designated as the X direction, and of the two directions perpendicular to the X direction, one of the longitudinal directions of the battery cells is designated as the Y direction, and the other of the lateral directions (the direction corresponding to the direction of gravity) is designated as the Z direction (the same applies to the following drawings). As shown in FIG. 1, the battery pack 1 includes a housing 10, a plurality of battery cells 2, and an insulating elastic member 30.

The housing 10 is made of metal and has a box-like shape. The multiple battery cells 2 are lithium-ion batteries. Each of the multiple battery cells 2 has a rectangular thin plate shape and is stacked in the thickness direction (X direction). The insulating elastic member 30 is disposed between adjacent battery cells 2. As shown in Figures 2 and 3, the insulating elastic member 30 has an insulating sheet 40, two elastic bodies 50, 51, and a regulating body 60.

The insulating sheet 40 is a rectangular sheet with a thickness of 2 mm. It comprises a sheet body 41 and a cover layer 42. The sheet body 41 comprises an insulating layer and a substrate supporting it. The insulating layer comprises silica aerogel, silica particles as a binder, and gypsum. The substrate is made of glass cloth. The insulating layer is formed by applying a slurry-like composition containing silica aerogel to the substrate. A portion of the insulating layer is impregnated into the pores between the glass fibers that make up the substrate. The cover layer 42 is made of a resin film and covers the surface of the sheet body 41. The back surface of the sheet body 41, which is not covered by the cover layer 42, is in contact with the battery cell 2.

Two elastic bodies 50, 51 are arranged on one side of the insulation sheet 40, i.e., one of the Y-Z planes. The two elastic bodies 50, 51 are adhered to the cover layer 42 of the insulation sheet 40 with double-sided tape (not shown). The two elastic bodies 50, 51 each extend in the Y direction (the longitudinal direction of the insulation sheet 40) and are arranged parallel to each other with a predetermined distance in the Z direction (the transverse direction of the insulation sheet 40). The two elastic bodies 50, 51 are identical in material, shape, and dimensions. Therefore, only one of the elastic bodies, 50, will be described here. The elastic body 50 is made of a cross-linked rubber composition containing ethylene-propylene-diene rubber (EPDM). The elastic body 50 has a flat plate portion 500 and two ridge portions 501. The two ridge portions 501 each extend in the Y direction. The two ridge portions 501 are arranged parallel to each other in the Z direction, separated by the flat plate portion 500. The flat plate portions 500 and protruding portions 501 are alternately arranged in the Z direction, giving the surface of the elastic body 50 facing the battery cell 2 an uneven shape. The height of the two protruding portions 501 (maximum thickness of the elastic body 50) is 6 mm in an uncompressed state. The two protruding portions 501 are in elastic contact with the adjacent battery cell 2.

The regulator 60 is also disposed on the Y-Z plane of the heat insulating sheet 40, where the two elastic bodies 50 and 51 are disposed. The regulator 60 is adhered to the cover layer 42 of the heat insulating sheet 40 with double-sided tape (not shown). The regulator 60 is strip-shaped and disposed between the two elastic bodies 50 and 51. The regulator 60 extends in the Y direction at a midpoint in the Z direction. The regulator 60 is 2 mm thick. The regulator 60 is made of a flame-retardant insulating cloth. The flame-retardant insulating cloth is the same as the sheet body 41 of the heat insulating sheet 40, and includes an insulating layer containing silica aerogel, silica particles, and gypsum as binders, and glass cloth supporting the insulating layer. A portion of the insulating layer is impregnated into the pores between the fibers of the glass cloth. The glass cloth is included in the concept of "inorganic fiber cloth" in this disclosure. The regulator 60 is flame-retardant, and its thermal conductivity is lower than that of the elastic bodies 50 and 51.

[Action and effect]
Next, the effects of the heat-insulating elastic member of this embodiment will be described. In the heat-insulating elastic member 30, two elastic bodies 50, 51 and a regulating body 60 are arranged on one side of the heat-insulating sheet 40. The two elastic bodies 50, 51 elastically contact the battery cells 2 and repeatedly compress and restore in response to the expansion and contraction of the battery cells 2 during charging and discharging. This prevents the battery cells 2 from shifting position while the vehicle is running and absorbs deformation of the battery cells 2 due to charging and discharging. Furthermore, because the elastic body 50 has two protrusions 501 (the same applies to the elastic body 51), its cross-sectional area in the X-Z direction is smaller than when it is formed into a rectangular parallelepiped shape with the same thickness. As a result, the elastic bodies 50, 51 are easily compressively deformed and have excellent conformity to the battery cells 2. Both of the two elastic bodies 50, 51 extend linearly in one direction. This makes it easy to manufacture by extrusion. The two elastic bodies 50, 51 are arranged symmetrically in the Z direction, sandwiching the regulating body 60. Therefore, deformation of adjacent battery cells 2 can be absorbed in a balanced manner, and problems such as tilting of the battery cells 2 during charging and discharging are less likely to occur.

The regulator 60 is positioned between the two elastic bodies 50, 51. Unlike the two elastic bodies 50, 51, the regulator 60 is made of a flame-retardant insulating fabric. Therefore, even if the temperature of the adjacent battery cell 2 rises, the regulator 60 is resistant to combustion and heat transfer. The flame-retardant insulating fabric is formed by supporting an insulating layer containing silica aerogel and other materials on glass cloth. The binder that binds the components of the insulating layer, such as silica aerogel, is silica particles and gypsum. This makes the binder less likely to decompose or deteriorate even at high temperatures, maintaining the insulating structure. The regulator 60 is also relatively hard and is resistant to crushing even when compressed by the expansion of the battery cell 2. Therefore, even if the temperature of the battery cell 2 rises and the two elastic bodies 50, 51 melt, the regulator 60 remains. This prevents the battery cell 2 from expanding and maintains the distance between the battery cell 2 and the insulating sheet 40. The regulator 60 is positioned to separate the two elastic bodies 50, 51. This also has the effect of blocking the molten material from the elastic bodies 50, 51. Here, because the regulator 60 contains glass cloth, some of the molten material from the elastic bodies 50, 51 is impregnated into the pores between the glass fibers. The regulator 60 is arranged in a strip-like shape at the center in the Z direction. When the temperature of the battery cells 2 rises, the center portion of the battery cells 2 tends to expand. Therefore, when the regulator 60 is arranged in a central region on one side of the heat insulating sheet 40, it is effective in maintaining the distance between the battery cells 2 and the heat insulating sheet 40. In this way, the heat insulating elastic member 30 allows the heat insulating effect of the regulator 60 and the heat insulating sheet 40 to be fully exerted.

The insulating elastic member 30 is 8 mm thick. The insulating elastic member 30 can suppress heat transfer between adjacent battery cells 2 without increasing the thickness of the insulating sheet 40 or increasing the amount of insulating material. This reduces costs. Although the insulating sheet 40 is thin and not self-supporting, the regulator 60 acts as a framework, allowing the insulating elastic member 30 as a whole to exhibit self-supporting properties. This improves assembly workability. The sheet body 41 of the insulating sheet 40 is covered by a cover layer 42. This prevents fluffing of glass fibers and powder shedding of silica aerogel, improving workability. Furthermore, it also prevents the glass cloth of the sheet body 41 from being impregnated with the molten elastic bodies 50 and 51.

Second Embodiment
[composition]
The difference between the insulating elastic member of this embodiment and the insulating elastic member of the first embodiment is the arrangement of the elastic body and the regulating body. Here, the differences will be mainly explained. FIG. 4 shows a perspective view of the insulating elastic member of this embodiment. FIG. 5 shows a V-V cross-sectional view of FIG. 4 (a cross-sectional view of the insulating elastic member in the thickness direction). In FIGS. 4 and 5, the same components as those in the first embodiment are designated by the same reference numerals. As shown in FIGS. 4 and 5, the insulating elastic member 31 has an insulating sheet 40, two elastic bodies 52, 53, and a regulating body 61.

Two elastic bodies 52, 53 are arranged on one side of the insulation sheet 40, i.e., one of the Y-Z planes. The two elastic bodies 52, 53 are adhered to the cover layer 42 of the insulation sheet 40 with double-sided tape (not shown). The two elastic bodies 52, 53 are arranged one on each side in the Y direction (the longitudinal direction of the insulation sheet 40) with a predetermined distance between them. The two elastic bodies 52, 53 are identical in material, shape, and dimensions. Therefore, only one of the elastic bodies, 52, will be described here. The elastic body 52 is made of a cross-linked rubber composition containing EPDM. The elastic body 52 has a flat plate portion 520 and six ridge portions 521. Each of the six ridge portions 521 extends in the Z direction. The six ridge portions 521 are arranged parallel to each other in the Z direction, with the flat plate portion 520 interposed between them. The flat plate portions 520 and protrusions 521 are alternately arranged in the Y direction, giving the surface of the elastic body 52 facing the battery cell an uneven shape. The height of the six protrusions 521 (maximum thickness of the elastic body 52) is 6 mm in an uncompressed state. The six protrusions 521 are in elastic contact with adjacent battery cells.

The regulator 61 is also arranged on the YZ plane of the heat insulating sheet 40 where the two elastic bodies 52, 53 are arranged. The regulator 61 is adhered to the cover layer 42 of the heat insulating sheet 40 with double-sided tape (not shown). The regulator 61 has a rectangular plate shape and is arranged between the two elastic bodies 52, 53. The regulator 61 is arranged in the middle section when one side of the heat insulating sheet 40 is divided into approximately three sections in the Y direction. The regulator 61 is 2 mm thick. The regulator 61 is made of the same flame-retardant insulating fabric as the regulator 60 of the first embodiment.

[Action and effect]
Next, the effects of the insulating elastic member of this embodiment will be described. The insulating elastic member of this embodiment and the insulating elastic member of the first embodiment have similar effects in the parts that share the same configuration. According to the insulating elastic member 31, the two elastic bodies 52, 53 are arranged symmetrically in the Y direction with the restrictor 61 in between. This allows for balanced absorption of deformation of adjacent battery cells, making it less likely for problems such as battery cell tilting during charging and discharging to occur. The restrictor 61 is arranged over the entire middle position in the Y direction. This is therefore effective in maintaining the gap between the battery cell and the insulating sheet 40 even when the temperature of the battery cell rises and the central area expands.

Third Embodiment
[composition]
The differences between the heat insulating elastic member of this embodiment and the heat insulating elastic member of the first embodiment are the configuration of the heat insulating sheet, the shape of the elastic body, and the inclusion of an exterior body. Here, the differences will be mainly described. Fig. 6 shows a perspective view of the heat insulating elastic member of this embodiment. Fig. 7 shows a cross-sectional view (thickness direction cross-sectional view of the heat insulating elastic member) taken along line VII-VII of Fig. 6. For ease of explanation, the exterior body is omitted from Fig. 6. In Figs. 6 and 7, the same components as those in the first embodiment are denoted by the same reference numerals. As shown in Figs. 6 and 7, the heat insulating elastic member 32 includes a heat insulating sheet 43, two elastic bodies 54 and 55, a regulating body 60, and an exterior body 44.

The heat insulating sheet 43 is a rectangular sheet with a thickness of 2 mm. The heat insulating sheet 43 is the same as the sheet body 41 in the first embodiment, and is made of a heat insulating layer containing silica aerogel or the like supported on a glass cloth substrate.

Two elastic bodies 54, 55 are arranged on one side of the insulation sheet 43, i.e., one of the Y-Z planes. Each of the two elastic bodies 54, 55 has a flat plate shape extending in the Y direction (the longitudinal direction of the insulation sheet 40). The two elastic bodies 54, 55 are arranged parallel to each other with a predetermined distance in the Z direction (the transverse direction of the insulation sheet 40). The two elastic bodies 54, 55 are identical in material, shape, and dimensions. Therefore, only one of the elastic bodies, 54, will be described here. The elastic body 54 is made of a cross-linked rubber composition containing EPDM. The elastic body 54 has a hollow portion 540 and a pair of lightening holes 541. The hollow portion 540 is located in the center of the interior of the elastic body 54 and extends in the Y direction. The pair of lightening holes 541 are located on both sides of the elastic body 54 in the Z direction, and each extend in the Y direction. The thickness of the elastic body 54 is 6 mm in an uncompressed state. The surface of the elastic body 54 facing the battery cell is in elastic contact with the adjacent battery cell.

The regulator 60 is also arranged on the Y-Z plane of the heat insulating sheet 43, where the two elastic bodies 54, 55 are arranged. The regulator 60 is strip-shaped and is arranged between the two elastic bodies 54, 55. The regulator 60 extends in the Y direction at a midpoint in the Z direction. The regulator 60 is made of a 2 mm thick flame-retardant heat insulating fabric.

The outer casing 44 is made of a resin film and covers the entire surface of the laminate consisting of the heat insulating sheet 43, elastic bodies 54, 55, and regulator 60. The heat insulating elastic member 32 is manufactured by placing the laminate in a bag-shaped resin film, degassing it, and then thermocompressing the opening of the film. The outer casing 44 fixes and integrates the elastic bodies 54, 55, and regulator 60 to the heat insulating sheet 43.

[Action and effect]
Next, the effects of the insulating elastic member of this embodiment will be described. The insulating elastic member of this embodiment and the insulating elastic member of the first embodiment share the same configuration and have similar effects. In the insulating elastic member 32, the elastic body 54 has a hollow portion 540 and a pair of hollowed-out portions 541 (the same applies to the elastic body 55). Therefore, the cross-sectional area in the X-Z direction is smaller than when the elastic body 54 is formed into a solid rectangular parallelepiped shape with the same thickness. Therefore, the elastic bodies 54 and 55 are easily compressively deformed and have excellent conformity to the battery cells. The insulating elastic member 32 has an exterior body 44, and the elastic bodies 54 and 55 and the regulating body 60 are fixed and integrated to the insulating sheet 43 by the exterior body 44. Therefore, adhesives, pressure-sensitive adhesives, etc., are not required to bond the respective components. Additionally, the insulating sheet 43, the elastic bodies 54 and 55, and the regulating body 60 are enclosed within the exterior body 44, resulting in excellent handling and workability. Furthermore, since there is no need to consider fluffing of glass fibers or powder falling off of silica aerogel, a cover layer is not required on the heat insulating sheet as in the first and second embodiments.

<Other embodiments>
The above describes three embodiments of the heat insulating elastic member of the present disclosure. However, the embodiments are not limited to the above embodiments. The heat insulating elastic member of the present disclosure can be embodied in various forms by applying modifications and improvements that can be made by those skilled in the art.

[Elastic body]
The elastic body constituting the insulating elastic member of the present disclosure may have sufficient elasticity to deform in response to the expansion and contraction of the battery cells. For example, when the battery cells expand during charging, a thickness of approximately 1/3 to 1/4, and preferably approximately 1/2, is preferable. The thickness of the elastic body may be determined appropriately taking into account the spacing between the battery cells, the degree of expansion of the battery cells, and the like. For example, it may be 1 mm or more and 6 mm or less. When a cross-linked rubber composition is used for the elastic body, examples of the rubber component include ethylene-propylene-diene rubber (EPDM), silicone rubber, and acrylonitrile butadiene rubber (NBR). Of these, EPDM is preferable because it does not contain low-molecular-weight siloxane. Furthermore, it is desirable to use an organic peroxide as a cross-linking agent for the rubber component because it does not contain volatile components such as sulfur.

Multiple elastic bodies are arranged at predetermined intervals on one side of the heat insulating sheet. There are no particular limitations on the arrangement of the elastic bodies, but from the perspective of absorbing deformation due to expansion and contraction of the battery cells in a balanced manner, it is desirable to arrange them symmetrically on the surface of the heat insulating sheet laminated on the battery cells. The number of elastic bodies should be two or more. For example, if the battery cells are arranged in the X direction, and one of the two directions perpendicular to the X direction is the Y direction and the other is the Z direction, the elastic bodies can be arranged in a strip shape that divides the Y direction or the Z direction. Alternatively, they can be arranged in an island shape on the Y-Z plane, for example, dividing the Y-Z plane into four.

The shape of the elastic body is not particularly limited. The surface facing the battery cell may be uneven as in the first and second embodiments, flat as in the third embodiment, or even curved. The elastic body may be solid or hollow. If it has protrusions as in the first and second embodiments, the number and shape of the protrusions are not particularly limited. The cross section of the protrusions in the thickness direction may be trapezoidal, rectangular, semicircular, or the like. If it has a hollow portion as in the third embodiment, the size and shape of the hollow portion are not particularly limited.

[Regulatory body]
The regulating body constituting the insulating elastic member of the present disclosure is made of a material different from the elastomer. The regulating body is required only to have flame retardancy and a lower thermal conductivity than the elastomer. The presence or absence of flame retardancy can be determined, for example, by the following burner test. A 2 mm thick sheet-like test piece is prepared from the material of the regulating body, and the test piece is exposed to a direct flame of approximately 1000°C using a propane gas burner for 10 seconds. If no holes are formed in the test piece, the regulating body can be determined to be "flame retardant." Furthermore, it is desirable that the regulating body has compression resistance that can withstand the pressure caused by expansion of the battery cell when the temperature rises. The regulating body may be made of the same material as the constituent components of the insulating sheet.

The regulator can be formed from flame-retardant fabric or flame-retardant paper. A flame-retardant insulating fabric that also has thermal insulation properties is suitable as the flame-retardant fabric. Examples of flame-retardant insulating fabrics include those in which an insulating layer is supported on an inorganic fiber fabric. The insulating layer comprises a porous structure having a skeleton formed by multiple interconnected microparticles, internal pores, and hydrophobic regions on at least the surface or interior thereof, and a binder. As will be explained in detail later, the porous structure has a skeleton formed by multiple interconnected microparticles and a pore structure with a size of approximately 10 to 50 nm. Therefore, the thermal conductivity of the porous structure is lower than that of air, and the insulating layer having the porous structure has high thermal insulation properties. Examples of inorganic fiber fabrics include woven and nonwoven fabrics made from glass fiber, rock wool, ceramic fiber, etc. Examples of flame-retardant paper include flame-retardant insulating paper manufactured as a composite of pulp and magnesium silicate.

The shape of the regulating body is not limited. The regulating body may or may not come into contact with the battery cell under normal conditions. The thickness of the regulating body can be determined appropriately depending on the hardness and behavior when compressed, and may be the same as, larger or smaller than, the thickness of the elastic body. If the regulating body is relatively hard, it should be thinner than the elastic body. For example, a thickness of about half the thickness of the elastic body or less is preferable. Conversely, if the regulating body is relatively soft, it may be the same as or thicker than the elastic body.

There are no limitations on the number or placement of the regulators, as long as they are placed at least between the elastic bodies. The regulators may be placed so that they extend in one direction, or so that they intersect, for example, in a cross shape, or in an island shape. In addition to being placed so that they divide the elastic bodies, the regulators may also be placed around one side of the heat insulating sheet, or on the end of the battery pack on the cooling member side. Placing the regulators in these positions can prevent the outflow of molten elastic material caused by a temperature rise in the battery cells. Furthermore, placing the regulators so that they include the central region on one side of the heat insulating sheet is highly effective in suppressing expansion of the battery cells and maintaining the distance between the battery cells and the heat insulating sheet.

[Thermal insulation sheet]
The heat insulating sheet constituting the heat insulating elastic member of the present disclosure may have any configuration, as long as it is a sheet-like member having heat insulating properties. For example, it is desirable for the heat insulating sheet to be configured to have a heat insulating layer and a substrate supporting the heat insulating layer. Here, it is desirable for the heat insulating layer to have a porous structure in which a plurality of fine particles are connected to form a skeleton, have pores inside, and have hydrophobic portions on at least the surface of the surface and the interior, and a binder. A heat insulating sheet of this configuration can be produced by applying a composition for producing a heat insulating layer (heat insulating layer composition) to a substrate and drying it.

Porous structures have hydrophobic sites on at least the surface, out of the surface and interior. Having hydrophobic sites on the surface can prevent moisture and other substances from seeping in, thereby maintaining the pore structure and making it less likely that insulation properties will be impaired. For example, surface treatment with a silane coupling agent or the like can impart hydrophobic properties to the surface of the porous structure. Furthermore, hydrophobic treatment, such as the addition of hydrophobic groups, may be performed during the manufacturing process of the porous structure.

The type of porous structure is not particularly limited. Examples of primary particles include silica, alumina, zirconia, and titania. Among these, silica aerogel, in which the primary particles are silica, i.e., multiple silica microparticles linked together to form a skeleton, is preferred from the perspective of excellent chemical stability. Silica aerogel is white and reflects infrared rays. Therefore, using silica aerogel can impart a heat-shielding effect to the insulating layer.

The method for producing silica aerogel is not particularly limited, and the drying process can be performed at normal pressure or supercritical pressure. For example, if hydrophobic treatment is performed before the drying process, supercritical drying is not necessary; drying at normal pressure is sufficient, making production easier and less costly. Depending on the drying method used to produce aerogel, those dried at normal pressure are sometimes called "xerogel" and those dried at supercritical pressure are sometimes called "aerogel," but in this specification, both are referred to as "aerogel."

As the binder, it is preferable to use a binder (aqueous binder) that uses water (including pure water, tap water, etc.) as a solvent, as it makes it easier to prepare the insulating layer composition. It is desirable to use an inorganic binder, whose binder component is an inorganic material, as it reduces decomposition and deterioration of organic components at high temperatures and suppresses the occurrence of cracks, etc. Inorganic materials include metal oxides such as silica, titania, zinc oxide, and zirconia, as well as water glass (sodium silicate), cement, gypsum, magnesium silicate, quicklime, and hydrated lime. Among these, binders containing silica are preferred because they are compatible with the porous structure, inexpensive, and readily available. Hydraulic materials such as cement, gypsum, and magnesium silicate are also preferred because they react with the solvent water to form a binder while filling the gaps between the porous structure, thereby forming a high-strength insulating layer.

When the inorganic material is nanoparticles (particles on the nanometer order), the drawbacks of hardness and brittleness caused by the presence of inorganic materials in the thermal insulation layer can be improved. Examples of binders containing silica nanoparticles include colloidal silica or sodium silicate solution, which use water as a dispersion medium. Examples of binders containing titania nanoparticles include an aqueous titania dispersion.

In addition to the porous structure and binder, the thermal insulation layer may contain other components such as crosslinkers, thickeners, reinforcing fibers, and flame retardants. Porous structures with hydrophobic sites on their surface or interior are less compatible with water. Silica aerogel, in particular, has a low specific gravity and tends to float in water. Therefore, when preparing a thermal insulation layer composition, dispersing silica aerogel in a water-based binder liquid is difficult, resulting in a time-consuming dispersion process. For example, adding a thickener increases the viscosity of the binder liquid, improving the water suspension of the hydrophobic porous structure and facilitating dispersion of the porous structure. This shortens the time required to disperse the porous structure and improves productivity. It also imparts flexibility to the thermal insulation layer, thereby suppressing cracking. Examples of thickeners that can be used include polysaccharides such as carboxymethyl cellulose (CMC), polyethylene oxide (PEO), carboxyethyl cellulose, carboxypropyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, xanthan gum, agarose, and carrageenan, as well as polyvinyl alcohol and glucomannan.

When reinforcing fibers are added, they become physically entangled around the porous structure, improving the mechanical strength of the insulating layer and preventing the porous structure from falling off. There are no particular restrictions on the type of reinforcing fiber, but considering heat resistance and other factors, ceramic fibers such as glass fiber and alumina fiber are preferred.

The incorporation of a flame retardant can impart flame retardancy to the insulating layer. Known flame retardants, such as halogen-based, phosphorus-based, and metal hydroxide-based flame retardants, can be used. Considering the environmental impact, it is preferable to use a phosphorus-based flame retardant. Examples of phosphorus-based flame retardants include ammonium polyphosphate, red phosphorus, and phosphate esters. Of these, water-insoluble flame retardants are preferred because they are less likely to leak even when in contact with moisture during use; for example, ammonium polyphosphate is suitable.

Materials for the substrate include cloth, resin, and paper. Examples of fibers that make up cloth include glass fiber, rock wool, ceramic fiber, alumina fiber, silica fiber, carbon fiber, metal fiber, polyimide fiber, aramid fiber, and polyphenylene sulfide (PPS) fiber. Known ceramic fibers include refractory ceramic fiber (RCF), polycrystalline alumina fiber (Polycrystalline Wool: PCW), and alkaline earth silicate (AES) fiber. Among these, AES fiber is biosoluble and therefore safer. Examples of resins include polyethylene terephthalate (PET), polyimide, polyamide, and PPS. Examples of paper include pulp and composites of pulp and magnesium silicate. The shape of the substrate is not particularly limited, and examples include woven fabric, nonwoven fabric, film, and sheet. For example, woven and nonwoven fabrics made from inorganic fibers such as glass fiber and metal fiber, such as glass cloth, and flame-retardant insulating paper made as a composite of pulp and magnesium silicate have relatively low thermal conductivity and retain their shape well even in high-temperature environments. Highly heat-resistant substrates can be made from glass fiber, rock wool, ceramic fiber, polyimide, PPS, etc., and specific examples include glass fiber nonwoven fabric, glass cloth, aluminum glass cloth, AES wool paper, and polyimide fiber nonwoven fabric.

In addition to the insulating layer, the insulating sheet may have a functional layer with properties such as flame retardancy, radiant heat dissipation, and electrical insulation. The functional layer may be laminated on one or both sides of the insulating layer. The functional layer can be formed by combining functional materials such as mica, kaolinite, silica, talc, zirconia, and titanium oxide, blended according to the required function, with a binder. The insulating sheet may also have a cover layer that encases the sheet body consisting of the insulating layer and functional layer. The inclusion of the cover layer improves the adhesion, handling, and workability of the elastomer and regulating body. The cover layer can be formed, for example, from a high-melting-point material such as talc, kaolinite, montmorillonite, mica, silica, potassium titanate, titanium oxide, silicon nitride, alumina, aluminum nitride, silicon carbide, or zirconia, ammonium polyphosphate as a flame retardant, and a urethane resin as a binder. It may also be formed from a high-melting-point material and colloidal silica. Furthermore, the cover layer may be formed from a resin film made of glass cloth or polyimide.

[Exterior body]
Although an outer casing is not necessarily required, by placing components such as a heat insulating sheet inside a bag-shaped outer casing, the components can be integrated, improving handling and workability. As the outer casing, a resin film made of PET, polypropylene (PP), or the like is suitable.

[Battery pack]
The type of battery cell to which the heat insulating elastic member of the present disclosure is applied is not particularly limited. For example, a battery module formed by stacking a plurality of battery cells made of lithium ion batteries and the heat insulating elastic member of the present disclosure can be fastened from both sides in the stacking direction with fastening members and housed in a housing to form a battery pack.

1: Battery pack, 2: Battery cell, 10: Housing, 30, 31, 32: Heat insulating elastic member, 40, 43: Heat insulating sheet, 41: Sheet body, 42: Cover layer, 44: Exterior body, 50, 51, 52, 53, 54, 55: Elastic body, 60, 61: Regulating body, 500, 520: Flat plate portion, 501, 521: Protrusion portion, 540: Hollow portion, 541: Lightening portion.

Claims (14)

A heat insulating elastic member disposed between adjacent battery cells,
A heat insulating sheet,
a plurality of elastic bodies arranged at predetermined intervals on one side of the heat insulating sheet;
a regulating body that is disposed on one side of the heat insulating sheet at least between the elastomers, that is made of a material different from the elastomers, that has flame retardancy, and that has a thermal conductivity lower than that of the elastomers;
A heat insulating elastic member comprising: When the arrangement direction of the battery cells is the X direction, and one of two directions perpendicular to the X direction is the Y direction and the other is the Z direction,
The plurality of elastic bodies extend in the Y direction or the Z direction,
The heat insulating elastic member according to claim 1 , wherein the restricting body is disposed between adjacent ones of the elastic bodies. The Y direction is the longitudinal direction of the heat insulating sheet, and the Z direction is the lateral direction of the heat insulating sheet,
The plurality of elastic bodies extend in the Y direction and are arranged one by one at predetermined intervals in the Z direction,
3. The heat insulating elastic member according to claim 2, wherein the regulating body is disposed between the two elastic bodies and extends in the Y direction. An insulating elastic member according to any one of claims 1 to 3, wherein the regulating body is arranged to include a central region on one side of the insulating sheet. The insulating elastic member described in any one of claims 1 to 4, wherein each of the multiple elastic bodies has a protrusion that elastically contacts the adjacent battery cell, and the surface of the elastic body facing the battery cell is uneven. An insulating elastic member according to any one of claims 1 to 5, wherein each of the multiple elastic bodies has a hollow portion. The regulating body is made of a flame-retardant heat insulating cloth or a flame-retardant paper,
The flame-retardant insulating fabric is a heat-insulating elastic member described in any one of claims 1 to 6, which is formed by supporting an insulating layer having a porous structure in which a plurality of microparticles are linked to form a skeleton, which has pores inside, and which has hydrophobic portions on at least the surface of the surface and the interior, and a binder, on an inorganic fiber cloth. Further, it has a bag-shaped outer body,
8. The heat insulating elastic member according to claim 1, wherein the heat insulating sheet, the plurality of elastic bodies, and the regulating body are integrated by the exterior body. The heat insulating sheet has a heat insulating layer,
The insulating elastic member according to any one of claims 1 to 8, wherein the insulating layer comprises a porous structure having a skeleton formed by connecting a plurality of microparticles, pores inside, and hydrophobic portions at least on the surface of the surface and inside, and a binder. The insulating elastic member according to claim 9, wherein the insulating sheet further comprises a substrate supporting the insulating layer. The insulating elastic member according to claim 9 or claim 10, wherein the binder is an inorganic binder containing an inorganic material. The insulating elastic member according to claim 11, wherein the inorganic material comprises one or more selected from silica, water glass, cement, gypsum, magnesium silicate, quicklime, and slaked lime. The insulating elastic member according to any one of claims 9 to 12, wherein the insulating layer further contains one or more selected from a thickener and a reinforcing fiber. The insulating elastic member according to any one of claims 9 to 13, wherein the porous structure is a silica aerogel in which a skeleton is formed by connecting multiple silica microparticles.