Thermal insulation material and method for producing thermal insulation material

Abstract

A thermal insulation material 3 is for use in a battery pack including a battery group in which single batteries and the thermal insulation material are stacked in an alternating manner. The thermal insulation material 3 comprises: a plate-like member 31 having through holes 31h formed by partitioning with a partition wall 31w comprising an inorganic non-metal material; and a reinforcement member for reinforcing the plate-like member 31. As a result, it is possible to provide a thermal insulation material and a method for producing the thermal insulation material that can suppress the spread of heat to an adjacent single battery when a single battery generates abnormal heat.

Description

Heat insulating material and method for manufacturing the same

[0001] The present invention relates to a thermal insulating material and a method for manufacturing the thermal insulating material. In particular, the present invention relates to a thermal insulating material used in a battery pack including a group of batteries in which unit cells and thermal insulating materials are alternately stacked, and a method for manufacturing the thermal insulating material.

[0002] Conventionally, assembled batteries including a group of batteries in which unit cells and insulating materials are alternately stacked have been known. The insulating materials prevent heat transfer to adjacent unit cells when a unit cell generates abnormal heat due to factors such as a short circuit or overcharging. This prevents heat transfer to adjacent unit cells, preventing or delaying the spread of fire even if a unit cell generates abnormal heat and, for example, catches fire.

[0003] Patent Document 1 discloses a partition member that separates cells constituting a battery pack or separates cells from components other than the cells. This partition member includes an inner container capable of holding a liquid and an outer container having an internal space that accommodates the liquid and the inner container in a sealed state, and the inner container is sealed under a pressure of 0.05 kgf / cm. ２ Water absorption rate 1 indicates the water absorption rate when compressed for 1 minute under a pressure of 5 kgf / cm ２ The ratio of [water absorption rate 2] / [water absorption rate 1] to water absorption rate 2, which indicates the water absorption rate when compressed at 100°C for 1 minute, is 0.4 or more.

[0004] International Publication No. 2019 / 107561

[0005] However, conventional heat insulating materials have insufficient heat insulating function and are unable to sufficiently prevent adjacent cells from overheating when a cell abnormally heats up. An object of the present invention is to provide a heat insulating material and a method for manufacturing a heat insulating material that can suppress overheating of adjacent cells when a cell abnormally heats up, compared to a case not equipped with the configuration of the present invention.

[0006] In order to solve the above problems, the present invention provides an insulating material to be used in a battery pack including a group of batteries in which single cells and insulating materials are alternately stacked, the insulating material comprising: a plate-shaped member having through holes formed by partitioning with partition walls made of an inorganic non-metallic material; and a reinforcing member that reinforces the plate-shaped member.

[0007] The present invention also provides a method for manufacturing an insulating material used in a battery pack including a group of batteries in which single cells and insulating materials are alternately stacked, the method including a preparation step of preparing a plate-shaped member having through holes formed by partitioning with partition walls made of an inorganic non-metallic material, and a reinforcing step of reinforcing the plate-shaped member by forming a reinforcing member on the plate-shaped member.

[0008] The object of the present invention is to provide a heat insulating material and a method for manufacturing the heat insulating material that can suppress heating of adjacent unit cells when a unit cell generates abnormal heat, compared to a case where the configuration of the present invention is not provided.

[0009] 6( a) to 6(c) are diagrams illustrating a battery group included in a battery pack. (a) to 6(c) are diagrams illustrating a first example of the configuration of the insulating material of this embodiment. (a) to 6(b) are diagrams illustrating a second example of the configuration of the insulating material of this embodiment. (a) to 6(d) are diagrams illustrating a third example of the configuration of the insulating material of this embodiment. (a) to 6(e) are diagrams illustrating a fourth example of the configuration of the insulating material of this embodiment. (a) to 6(d) are diagrams illustrating an overall method for manufacturing the insulating material and the battery group. (a) to 6(c) are diagrams illustrating an overall method for manufacturing the insulating material and the battery group. (a) to 6(d) are diagrams illustrating a case where a step of attaching a resin sheet as a cushion member is included. (a) to 6(d) are diagrams illustrating a first modified example of FIG. 6(b) when a filler is used as a reinforcing member. (a) to 6(d) are diagrams illustrating a second modified example of FIG. 6(b) when a filler is used as a reinforcing member. FIG. 1 is a diagram showing an extrusion molding device used when molding a rectangular parallelepiped molded body.

[0010] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings. <Description of the Configuration of Battery Group 1> FIG. 1 illustrates a battery group 1 included in a battery pack. The illustrated battery group 1 is formed by alternately stacking unit cells 2 and insulating materials 3. In addition to the battery group 1, the battery pack also includes busbar units connecting the positive and negative electrodes of the unit cells 2, a temperature measurement unit for measuring the temperature of the unit cells 2, a voltage detection unit for measuring the voltage of the unit cells 2, electrical wires, and a housing for accommodating these components. The unit cells 2 are, for example, lithium-ion secondary batteries, but are not limited to this type of secondary battery and may be, for example, nickel-metal hydride batteries. The insulating materials 3 are provided between adjacent unit cells 2 and are made of a thermally insulating material. This prevents heat transfer to adjacent unit cells 2 even if one unit cell 2 generates abnormal heat. The insulating materials 3 also function to insulate the unit cells 2 from each other, reducing the risk of short circuits.

[0011] <Explanation of the Structure of the Insulating Material 3> Figures 2(a) to 2(c) are diagrams showing a first example of the structure of the insulating material 3 of this embodiment. Of these, Figure 2(a) is a perspective view of the insulating material 3. The insulating material 3 is a plate-shaped member as a whole, and the main surface S0 and side surface S1 located on the left and right sides of the figure are rectangular. Figure 2(b) is a partially enlarged view showing the structure around the side surface S1 of the insulating material 3 in Figure 2(a). Figure 2(c) is a cross-sectional view taken along the line A-A' in Figure 2(b). As shown in Figure 2(b), the insulating material 3 includes a plate-shaped member 31 partitioned by partition walls 31w made of a thermally insulating material. The plate-shaped member 31 has through-holes 31h formed by partitioning by the partition walls 31w. The insulating material 3 includes a filler 32 filled in the through-holes 31h. 2(a)-(b), the through-holes 31h are formed along the main surface S0 and penetrate from the side surface S1 on the front side to the side surface S1 on the back side in the figure. In this case, the through-holes 31h can also be said to be multiple rectangular parallelepiped cells. The cross-sectional shape (opening shape) perpendicular to the extension direction of the cells is preferably a rectangle, a hexagon, an octagon, or a combination thereof. Among these, squares and hexagons are preferred.

[0012] The thickness of the partition walls 31w is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 70 μm or more, from the viewpoint of ensuring the strength of the plate-like member 31. Furthermore, the thickness of the partition walls 31w is preferably 150 μm or less, more preferably 130 μm or less, and even more preferably 100 μm or less, from the viewpoint of suppressing heat conduction to the plate-like member 31. In the present embodiment, the thickness of the partition walls 31w refers to the length of a line segment connecting the centers of gravity of adjacent cells across the partition walls in a cross section perpendicular to the cell extension direction. The average thickness of the partition walls refers to the average value of the thicknesses of all the partition walls.

[0013] The cell density (the number of cells per unit cross-sectional area perpendicular to the cell extension direction) is not particularly limited. However, from the viewpoint of ensuring the strength of the plate-like member 31, for example, it is set to 200 cells / square inch (46 cells / cm ２ ) or more, and preferably 300 cells / square inch (62 cells / cm ２ ) or more, and 400 cells / square inch (93 cells / cm ２ ) or more. From the viewpoint of suppressing heat conduction to the plate-like member 31, the thickness of the partition wall 31w is preferably 900 cells / square inch (116 cells / cm ２ ) or less, and 750 cells / in² (93 cells / cm²) or less ２ ) or less, and more preferably 600 cells / in 2 (62 cells / cm 2 ) or less. ２ Here, the cell density is calculated by dividing the bottom area of ​​one side of the plate-like member 31 excluding the outer peripheral side wall by the opening area of ​​all the cells on the bottom surface (if plugged cells exist, the calculation is performed assuming that the cells are not plugged).

[0014] The porosity of the partition walls 31w may be adjusted appropriately depending on the application, but from the viewpoint of keeping thermal conductivity low, it is preferably 25% or more, more preferably 35% or more, and even more preferably 45% or more. Furthermore, from the viewpoint of ensuring the strength of the plate-like member 31, the porosity of the partition walls 31w is preferably 80% or less, more preferably 75% or less, and even more preferably 70% or less. The porosity is measured by mercury intrusion porosimetry using a mercury porosimeter in accordance with JIS R1655:2003.

[0015] The plate-shaped member 31 is made of a sintered inorganic non-metallic material. That is, the plate-shaped member 31 is, for example, a ceramic such as cordierite or diatomaceous earth. However, the plate-shaped member 31 does not necessarily have to be a sintered inorganic non-metallic material. By forming the plate-shaped member 31 from such a material, it is possible to reduce the thermal conductivity and make it less likely for heat to be transmitted. The plate-shaped member 31 is made to fit the size of the cell 2, but preferably has a thickness of 1 mm to 6 mm, a height of 30 mm to 200 mm, and a depth of 100 mm to 500 mm.

[0016] The filler 32 also has thermal insulation properties. The filler 32 is, for example, an aerosol, and more specifically, fumed silica, mica powder, or the like. Such filler 32 has a lower thermal conductivity than air, so providing the filler 32 in the through-holes 31h reduces the thermal conductivity compared to a hollow state, making it more difficult for heat to be transmitted. Furthermore, applying the aerosol, which is the material of the filler 32, to the side surface S1 of the plate-like member 31 can further improve the thermal insulation properties.

[0017] The filler 32 also serves as a reinforcing member that reinforces the plate-like member 31. In other words, if the plate-like member 31 is made of ceramics or the like, it is likely to have low strength and may be damaged due to vibrations during the manufacture of the heat insulating material 3 or during actual use. By providing the filler 32 in the through-holes 31h, the strength of the heat insulating material 3 is improved and damage can be suppressed.

[0018] 3(a) and 3(b) are diagrams illustrating a second example of the configuration of the insulating material 3 according to the present embodiment. The insulating material 3 shown in FIGS. 3(a) and 3(b) includes resin sheets 33 attached as cushioning members to the two main surfaces S0 of the plate-shaped member 31. The cells 2 repeatedly expand and contract during charging and discharging. By providing the resin sheets 33, the expansion of the cells 2 can be absorbed by the resin sheets 33 contracting. This prevents the cells 2 from expanding, improving their durability. Furthermore, providing the resin sheets 33 improves the strength of the insulating material 3 and reduces breakage. That is, the resin sheets 33 also function as reinforcing members that reinforce the plate-shaped member 31. Furthermore, by making the resin sheets 33 from a material with low thermal conductivity, the insulating properties of the insulating material 3 can be improved. In this case, methods for providing the resin sheets 33 include, for example, attaching a polyurethane sheet or applying an epoxy resin.

[0019] 4(a) to 4(d) are diagrams showing a third example of the configuration of the heat insulating material 3 of this embodiment. Of these, FIG. 4(a) shows the plate-shaped member 31 described above. FIG. 4(b) shows the heat insulating material 3 formed by applying reinforcing materials 34a, 34b, and 34c to the plate-shaped member 31 of FIG. 4(a) as the reinforcing material 34. Of these, reinforcing material 34a is a reinforcing material applied to the main surface S0 of the plate-shaped member 31 at locations that will become sides. Furthermore, reinforcing material 34b is a reinforcing material applied in a grid pattern on the main surface S0 of the plate-shaped member 31. Furthermore, reinforcing material 34c is a reinforcing material applied in a grid pattern on the side surface S1 of the plate-shaped member 31 that faces the main surface S0.

[0020] 4(c) shows a case where a reinforcing material 34d is further applied to the thermal insulator 3 of FIG. 4(b) to form a thermal insulator 3. The reinforcing material 34d is applied to the entire side surface S1 of the plate-like member 31, which faces the main surface S0. The reinforcing materials 34a to 34d are, for example, glues containing at least one of a silicone resin such as a modified silicone polymer and a material using sodium silicate, an acrylic resin polymer, epoxy, and urethane.

[0021] The reinforcing material 34 also functions as a cushioning material. By providing the reinforcing material 34, the expansion of the cells 2 can be absorbed by the contraction of the reinforcing material 34. Fig. 4(d) shows a case in which a metal leaf spring 35 is further attached as a cushioning material to the heat insulating material 3 of Fig. 4(c) to form the heat insulating material 3. By providing the leaf spring 35, the expansion of the cells 2 can be absorbed by the contraction of the leaf spring 35.

[0022] 5(a) to 5(e) are diagrams illustrating a fourth example of the configuration of the thermal insulator 3 according to the present embodiment. Of these, FIG. 5(a) illustrates multiple pieces 31p constituting a plate-shaped member 31. FIG. 5(b) illustrates a plate-shaped member 31 formed by bonding multiple pieces 31p arranged in a grid pattern with adhesive 36 so that the surfaces of the pieces 31p facing the main surface S0 correspond to the side surfaces S1. The adhesive 36 is preferably elastic and heat-resistant. This allows the plate-shaped member 31 to be flexible and absorb the expansion and contraction of the cells 2. An example of an adhesive 36 that satisfies this requirement is an epoxy adhesive. FIG. 5(c) illustrates a thermal insulator 3 formed by applying a reinforcing material 34d to the plate-shaped member 31 of FIG. 5(b). Similar to the case of FIG. 4(c), the reinforcing material 34d is applied to the entire side surface S1 of the plate-shaped member 31 facing the main surface S0. By forming the plate-shaped member 31 by bonding together multiple pieces 31p, the plate-shaped member 31 can be made more flexible and less prone to breakage than when the plate-shaped member 31 is formed from a single piece as shown in FIG. 4(a). FIG. 5(d) shows a case where the insulating material 3 is formed by applying a reinforcing material 34e to the insulating material 3 of FIG. 5(c). The reinforcing material 34e is applied to the entire main surface S0 of the plate-shaped member 31. In this case, the reinforcing material 34e also functions as a cushioning material. By providing the reinforcing material 34e, the expansion of the cells 2 can be absorbed by the contraction of the reinforcing material 34e.

[0023] In Fig. 5(b), the pieces 31p are arranged in a grid pattern, but this is not limiting. Fig. 5(e) is a diagram showing another method of arranging the pieces 31p. Here, the pieces 31p are arranged in a staggered pattern. The pieces 31p arranged in a staggered pattern are bonded together with adhesive 36 so that the surfaces of the pieces 31p that form the side surfaces S1 relative to the main surface S0 form the plate-like member 31.

[0024] <Description of Manufacturing Method of Insulating Material 3 and Battery Group 1> Figures 6(a)-(d) and 7(a)-(c) are diagrams illustrating the overall manufacturing method of the insulating material 3 and battery group 1. The orientation of the through-holes 31h in the plate-shaped member 31 differs between Figures 6(a)-(d) and Figures 7(a)-(c). In Figures 6(a)-(d), the through-holes 31h extend along the main surface S0 of the plate-shaped member 31, as in Figure 2. In this case, to create the plate-shaped member 31, a sintered body 40 having through-holes 31h is first prepared and then cut into plates (cutting process). The sintered body 40 is a sintered body made of an inorganic nonmetallic material. Examples of inorganic nonmetallic materials include cordierite and diatomaceous earth. Figure 6(a) is a diagram illustrating this cutting process. Here, the sintered body 40 is cut out along the dotted lines to form the plate-shaped member 31. In the case of Figure 6(a), a rectangular parallelepiped sintered body 40 is prepared and cut along the direction of the through-holes 31h. The sintered body 40 in Figure 6(a) is cut to a predetermined length using a cutting means such as a cutter to form plate-like members 31. The sintered body 40 is preferably sized to allow for cutting out plate-like members 31 having a length of 3 cm to 10 cm, a width of 10 cm to 30 cm, and a thickness of 1 mm to 6 mm. There are no particular restrictions on the height of the sintered body 40 (the length of each cell), but in one embodiment, it can be 5 cm to 40 cm.

[0025] 6(a) can also be considered as a preparation step for preparing a plate-shaped member 31 having through holes 31h. In addition to the cutting step, the preparation step can also include a bonding step for bonding together the surfaces of the pieces 31p constituting the plate-shaped member 31 that form the side surfaces S1 relative to the main surface S0, as described with reference to FIG.

[0026] 6(b) shows a plate-like member 31 created by cutting out the fired body 40. In this embodiment, reinforcing members are formed from this state. As described above, the reinforcing members include the filler 32 (see FIG. 2) filled in the through holes 31h, the resin sheet 33 (see FIG. 3) attached to the two main surfaces S0 of the plate-like member 31, and the reinforcing material 34 (see FIG. 4) formed on the main surface S0 and side surface S1 of the plate-like member 31.

[0027] This step can also be considered a reinforcing step in which a reinforcing member is formed on the plate-shaped member 31 to reinforce the plate-shaped member 31. When a filler 32 is used as the reinforcing member, the reinforcing step can also be considered to include a filling step in which a heat-insulating filler is filled into the through-holes. When a reinforcing material 34 is used as the reinforcing member, the reinforcing step can also be considered to include an application step in which the reinforcing material 34 is applied to at least one of the portions that will become the sides, the lattice pattern, and the entire main surface on the main surface S0 of the plate-shaped member 31. The reinforcing step can also be considered to include an application step in which the reinforcing material 34 is applied to at least one of the lattice pattern and the entire side surface on the side surface S1 of the plate-shaped member 31 relative to the main surface S0.

[0028] The above steps allow the production of the heat insulating material 3. Fig. 6(c) shows a case where a battery group 1 is produced in which the cells 2 and the heat insulating materials 3 are alternately stacked.

[0029] The sintered body 40 is not limited to the rectangular parallelepiped shape shown in Fig. 6(a). For example, a cylindrical sintered body 40 may be prepared and cut to create the plate-like member 31. Alternatively, a thin rectangular sintered body 40 shown in Fig. 6(d) may be prepared and used as the plate-like member 31 as is.

[0030] On the other hand, in Figures 7(a) to (c), the through holes 31h are similar to those in Figures 6(a) to (c), except that the direction in which the through holes 31h extend is aligned with the normal direction of the main surface S0 of the plate-like member 31. Figure 7(a) is a diagram illustrating the cutting process when aligning the through holes 31h in this direction. Here, the dotted line in the figure indicates that the sintered body 40 is cut out to form the plate-like member 31. In the case of Figure 7(a), it can also be said that a rectangular shaped sintered body 40 is prepared, and this sintered body 40 is cut along a direction intersecting the direction in which the through holes 31h extend. In this case, the intersecting direction is a direction perpendicular to the direction in which the through holes 31h extend.

[0031] 2, to fill the through-holes 31h with the filler 32, the through-holes 31h of the plate-like member 31 are filled with the powder filler 32. As described above, the filler 32 is an aerosol of fumed silica or mica.

[0032] 3, for example, when a polyurethane sheet is used as the resin sheet 33, the polyurethane sheet is attached to the plate-like member 31 with an adhesive. FIGS. 8(a) to 8(d) are diagrams illustrating a case in which a step of attaching the resin sheet 33 as a cushion member is included. FIGS. 8(a) to 8(b) are similar to FIGS. 7(a) to 7(b). However, in this case, as shown in FIG. 8(c), a step (cushion member attachment step) of providing the resin sheet 33 as a cushion member that absorbs expansion of the cells 2 on the main surface S0 of the plate-like member 31 is added.

[0033] The above steps allow the production of the heat insulating material 3. Fig. 8(d) shows a case where a battery group 1 is produced in which the cells 2 and the heat insulating materials 3 provided with the resin sheets 33 are alternately stacked.

[0034] Furthermore, when the resin sheet 33 is provided by applying an epoxy resin, a slurry containing the epoxy resin is stored in advance in a storage container. Next, a mask having openings in locations corresponding to the cells where the resin sheet 33 is to be formed is attached to one bottom surface of the plate-like member 31. The bottom surface with the mask attached is then immersed in the storage container, and the openings are filled with the slurry containing the epoxy resin to form an epoxy resin sheet. An epoxy resin sheet is also formed on the other bottom surface in the same manner.

[0035] 4 is formed by applying glue containing at least one of silicone resin, sodium silicate, acrylic resin polymer, epoxy, and urethane to predetermined locations. Also, the leaf spring 35 shown in FIG. 4(d) can be attached by bonding the leaf spring 35 to the plate-shaped member 31 with adhesive.

[0036] 9(a) to 9(d) illustrate a first modification of FIG. 6(b) in which filler 32 is used as a reinforcing member. First, as shown in FIG. 9(a), a plate-shaped member 31 similar to that shown in FIG. 6(b) is prepared. Next, as shown in FIG. 9(b), the plate-shaped member 31 is cut along the dotted lines. As a result, as shown in FIG. 9(c), the plate-shaped member 31 is divided into two pieces, plate-shaped member 31a and plate-shaped member 31b. Then, the plate-shaped members 31a and 31b are placed opposite each other, and the partition walls 31w are arranged in a staggered pattern. Filler 32 is then filled in the form shown in FIG. 9(d). This process can also be considered a filling process in which heat-insulating filler 32 is filled into the through-holes 31h. In this case, the through-holes 31h are formed by arranging multiple partition walls 31w in a staggered pattern.

[0037] FIGS. 10(a) to 10(d) illustrate a second modification of FIG. 6(b) in which filler 32 is used as a reinforcing member. FIGS. 10(a) to 10(c) are similar to FIGS. 2(a) to 2(c), except that the through-holes 31h extend in a direction normal to the main surface S0 of the plate-like member 31. However, this modification presents a problem in that the through-holes 31h are short, making the filler 32 filling the through-holes 31h prone to falling out. Therefore, to prevent the filler 32 from falling out, a sealant 37 is applied to cover the through-holes 31h and the filler 32, as shown in FIG. 10(d). The sealant 37 can be formed, for example, by applying a paste containing a filler made of the same ceramic material as the plate-like member 31, such as cordierite or diatomaceous earth. Alternatively, the sealant 37 may be a resin sheet. In this case, the heat insulating material 3 further includes a sealing material 37 that seals the filler 32 on the main surface S0 of the plate-shaped member 31. It can be said that the reinforcing step further includes a sealing step of sealing the filler 32 on the main surface S0 of the plate-shaped member 31.

[0038] In addition to the above-described configuration, a heat dissipation function can also be provided by, for example, bonding a highly heat-conductive material such as ceramic or copper to the side surface of the plate-like member 31 and connecting it to a cooling plate provided in the battery pack.

[0039] <Method for Manufacturing Sintered Body 40> Next, a method for manufacturing the sintered body 40 will be described. (Extrusion Molding Process for Molded Body) First, a clay containing ceramic raw materials, a pore-forming agent, a binder, and a dispersion medium is prepared as a molding raw material. This molding raw material is then extruded through a ring-shaped or angular mask having an inner peripheral contour that defines the outer peripheral contours of the first and second bottom surfaces to produce a molded body (extrusion molding process for molded body). The mask is installed on a die that defines the opening shape of the multiple cells, and downstream of the die. Extrusion molding is performed in an orientation such that the extension direction of the cells is horizontal. After extrusion molding, the extrusion is cut to a predetermined length using a cutting means such as a cutter. By using a square-shaped mask, a rectangular parallelepiped molded body as shown in FIG. 6(a) can be produced. Alternatively, by using a ring-shaped die, a cylindrical molded body can be produced.

[0040] The ceramic raw material is a raw material for the portion that remains after firing of metal oxides, metals, etc., and that constitutes the skeleton of the fired body 40 as ceramic. The ceramic raw material may be provided in the form of, for example, powder. In addition to the cordierite and diatomaceous earth described above, the ceramic raw material may also be mullite, zircon, aluminum titanate, silicon carbide, silicon nitride, zirconia, spinel, indialite, sapphirine, corundum, titania, or the like.

[0041] The pore-forming material is not particularly limited as long as it forms pores after firing, and examples of the pore-forming material include wheat flour, starch, foamed resin, water-absorbent resin, silica gel, carbon (e.g., graphite), ceramic balloons, polyethylene, polystyrene, polypropylene, nylon, polyester, acrylic, phenol, foamed foamed resin, and unfoamed resin.

[0042] Examples of binders include organic binders such as methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, etc. In particular, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination.

[0043] Examples of the dispersion medium include water and a mixed solvent of water and an organic solvent such as alcohol, with water being particularly preferred.

[0044] FIG. 11 shows an extrusion molding apparatus 500 used to mold a rectangular parallelepiped molded article. The cross-sectional structure of the extrusion molding apparatus 500 is shown schematically as viewed from a direction perpendicular to the extrusion direction. The extrusion molding apparatus 500 includes a die 510 having slits 511a and 512a through which the molding raw material is extruded, and an annular mask 520 disposed downstream of the die 510. In the extrusion molding apparatus 500, the die 510 has an inner portion 511 and an outer peripheral portion 512. The inner portion 511 protrudes downstream (downward in FIG. 11 ), and a step portion 513 is formed between the inner portion 511 and the outer peripheral portion 512. The inner portion 511 is provided with slits 511a that define a cell structure having the desired cell shape, partition wall thickness, cell density, etc. The outer peripheral portion 512 is provided with slits 512a that are shorter than the slits 511a of the inner portion 511. A gap 530 that forms the outer peripheral side wall of the cell structure is formed between the die 510 and the annular mask 520. A back pressure plate 550 for fixing the die 510 is attached to the upstream side of the die 510. Furthermore, a pressing jig 540 is attached from the downstream side of the annular mask 520 so as to surround the outer peripheral side of the annular mask 520, the outer peripheral side of the die 510, and the outer peripheral side of the back pressure plate 550, and serves as a holder for fixing the die 510 and the annular mask 520.

[0045] In extrusion molding using the extrusion molding apparatus 500, the molding raw material is extruded from the upstream side of the die 510 (upper side in FIG. 11 ) to the downstream side through the die 510 by an extruder (not shown). The molding raw material extruded through the slit 511a provided in the inner portion 511 of the die 510, which is open downstream, forms a cellular structure having multiple cells. Meanwhile, the molding raw material extruded through the slit 512a provided in the outer peripheral portion 512 of the die 510 has its cellular structure crushed by the action of the gap 530, and changes its traveling direction from the extrusion direction to a direction along the step portion 513. After passing through the gap 530, the molding raw material changes its traveling direction back to the extrusion direction, forming an outer peripheral side wall surrounding the cells. In this manner, a rectangular parallelepiped molded product 560 is continuously molded from the extrusion molding apparatus 500. In this embodiment, the extrusion direction is horizontal, and the extrusion is performed in a direction such that the extension direction of the cells is horizontal. If the extrusion direction is horizontal, it is advantageous for continuously molding a long rectangular parallelepiped molded body 560 .

[0046] (Drying Process for Molded Body) Next, a drying process is carried out in which the molded body 560 is dried to obtain a dried body. In the drying process, a conventionally known drying method such as hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, etc. Among these, a drying method that combines hot air drying with microwave drying or dielectric drying is preferred because it can dry the entire molded body quickly and uniformly.

[0047] (Step of Firing the Molded Body) The dried body is placed on a shelf so that the extension direction of the cells is parallel to the vertical direction to the placement surface, and is fired while passing through a continuous firing furnace. Through the above steps, a fired body 40 can be obtained.

[0048] Example 1 A plate-shaped member 31 was prepared by cutting a fired body 40 made using diatomaceous earth as a raw material. This plate-shaped member 31 had a thickness of 3 mm, a height of 100 mm, and a depth of 300 mm. Fumed silica was then filled into this plate-shaped member 31 as a filler 32 to prepare a thermal insulator 3 having the structure shown in FIG. 2. The thermal conductivity of this thermal insulator 3 was 0.065 [W / (mK)].

[0049] Example 2 A plate-shaped member 31 was prepared by cutting a fired body 40 made using cordierite as a raw material. Fumed silica was then filled into this plate-shaped member 31 as a filler 32 to prepare a thermal insulator 3 having the structure shown in Fig. 2. The thermal conductivity of this thermal insulator 3 was 0.101 [W / (mK)].

[0050] Comparative Example: A conventional heat insulating material made of a mica sheet was prepared as a conventional product. The thermal conductivity of this heat insulating material was 0.18 [W / (mK)].

[0051] Therefore, it can be seen that the thermal insulation material 3 having the structure shown in Figure 2 in Examples 1 and 2 has better thermal insulation properties than conventional thermal insulation materials. When the filler 32 was not filled, the thermal conductivity was 0.091 [W / (mK)] in Example 1, and 0.121 [W / (mK)] in Example 2. In these cases, the thermal conductivity was also better than that of conventional products, but there was a problem of insufficient strength and susceptibility to breakage.

[0052] <Explanation of Effects> The above-described embodiment provides a thermal insulator 3 and a method for manufacturing the thermal insulator 3 that can suppress heating of adjacent cells 2 when cells 2 abnormally heat up, compared to a case without the configuration of the present invention. As a result, even when a cell 2 experiences thermal runaway, the thermal insulator 3 of this embodiment has a thermal insulating function that prevents heat from being transferred to adjacent cells 2. When a cell 2 experiences thermal runaway, the temperature may rise to, for example, 800°C or higher. Even in this case, the thermal propagation can be delayed, ensuring time for the driver to evacuate when the battery pack is used in a vehicle. Furthermore, when the thermal insulator 3 includes a cushioning member, the cushioning member can contract to absorb the expansion of the cells 2. Furthermore, when a highly thermally conductive material such as ceramic or copper is bonded to the side of the plate-shaped member 31 of the thermal insulator 3 and connected to the cooling plate of the battery pack, excellent heat dissipation is achieved. Furthermore, when the plate-shaped member 31 is made of a sintered inorganic nonmetallic material, it is lightweight, thereby reducing the weight of the thermal insulator 3 and the battery pack.

[0053] Although the present embodiment has been described above, the technical scope of the present invention is not limited to the scope of the above embodiment. It is clear from the claims that various modifications and improvements to the above embodiment are also included in the technical scope of the present invention.

[0054] REFERENCE SIGNS LIST 1...battery group, 2...single cell, 3...insulating material, 31...plate-shaped member, 31h...through hole, 31w...partition wall, 31p...piece, 32...filler, 33...resin sheet, 34, 34a, 34b, 34c...reinforcing material, 35...leaf spring, 36...adhesive, 37...sealing material, 40...fired body, 500...extrusion molding device, S0...main surface, S1...side surface

Claims

1. A thermal insulator used in a battery pack including a group of batteries in which unit cells and thermal insulators are alternately stacked, the thermal insulator comprising: a plate-shaped member having through holes formed by partitioning the plate-shaped member with partition walls made of an inorganic non-metallic material; and a reinforcing member that reinforces the plate-shaped member.

2. The heat insulating material according to claim 1, wherein the reinforcing member is a filler having heat insulating properties and filled into the through-hole.

3. The heat insulating material according to claim 2, further comprising a sealant for sealing the filler on the main surface of the plate-like member.

4. The insulation material of claim 2, wherein the filler comprises an aerosol.

5. The heat insulating material according to claim 1, wherein the reinforcing member is at least one of the following (1) to (2): (1) A reinforcing member applied to at least one of the edges, a lattice pattern, and the entire main surface of the main surface of the plate-shaped member; (2) A reinforcing member applied to at least one of the lattice pattern and the entire side surface of the side surface of the plate-shaped member opposite the main surface.

6. The heat insulating material according to claim 5, wherein the reinforcing material is a glue containing at least one of a silicone resin, a material using sodium silicate, an acrylic resin polymer, an epoxy, and a urethane.

7. The heat insulating material according to claim 1, wherein the plate-like member is made of a sintered body of the inorganic nonmetallic material.

8. The heat insulating material according to claim 1, further comprising a cushioning member for absorbing the expansion of the unit cells.

9. The heat insulating material according to claim 8, wherein the cushion member is at least one of a resin sheet and a metal leaf spring.

10. The heat insulating material according to claim 1, wherein the plate-like member is made by bonding together a plurality of pieces constituting the plate-like member with their side surfaces facing the main surface.

11. The heat insulating material according to claim 1, wherein the through holes are formed by arranging a plurality of rectangular parallelepiped cells or the partition walls in a staggered pattern.

12. A method for manufacturing an insulating material used in a battery pack including a group of batteries in which unit cells and insulating materials are alternately stacked, the method comprising: a preparation step of preparing a plate-like member having through holes formed by partitioning the plate-like member with partition walls made of an inorganic non-metallic material; and a reinforcing step of reinforcing the plate-like member by forming a reinforcing member on the plate-like member.

13. The method for manufacturing a heat insulating material according to claim 12, wherein the preparation step includes a cutting step of cutting a fired body of an inorganic nonmetallic material into plate-shaped members.

14. A method for manufacturing a heat insulating material as described in claim 12, wherein the preparation step includes a bonding step of bonding the surfaces of the plurality of pieces constituting the plate-like member that are side surfaces of the main surface together.

15. The method for manufacturing a heat insulating material according to claim 12, wherein the reinforcing step includes a filling step of filling the through holes with a filler having heat insulating properties.

16. The method for manufacturing a heat insulating material according to claim 15, wherein the reinforcing step further includes a sealing step of sealing the filler into the main surface of the plate-like member.

17. The method for manufacturing a heat insulating material according to claim 12, wherein the reinforcing step includes at least one of the following steps (3) to (4): (3) a coating step of applying a reinforcing material to at least one of the areas on the main surface of the plate-like member that will become sides, a lattice pattern, and the entire main surface; and (4) a coating step of applying a reinforcing material to at least one of the lattice pattern and the entire side surface on the side surface of the plate-like member that faces the main surface.

18. The method for manufacturing a heat insulating material according to claim 12, further comprising a cushion member attaching step of providing a cushion member on a main surface of the plate-like member to absorb expansion of the unit cells when the unit cells expand.

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