Spacer, spacer manufacturing method, and battery pack

Abstract

A spacer (4) includes: a heat insulating material (21); a cover (22) that has a first cover portion (22a) covering a first surface (21a) of the heat insulating material (21) and a second cover portion (22b) covering a second surface (21b) of the heat insulating material (21), the cover (22) further having an overlapping portion (22d) where the first cover portion (22a) and the second cover portion (22b) are disposed as overlapping each other at part of the peripheral edge thereof; and a seal line (23) that seals the overlapping portion (22d) of the cover (22). The cover (22) includes: the overlapping portion (22d) that forms part of the peripheral edge and covers part of the peripheral surface of the heat insulating material (21); and a continuous portion (22e) that forms another part of the peripheral edge, is formed so as to be continuous without the first cover portion (22a) and the second cover portion (22b) overlapping each other, and covers another part of the peripheral surface of the heat insulating material (21).

Description

Spacer, Method for Manufacturing Spacer, and Assembled Battery

[0001] The present disclosure relates to a spacer, a method for manufacturing the spacer, and an assembled battery.

[0002] Patent Documents 1 to 3 disclose spacers (heat insulating material units) arranged side by side with battery cells. The spacer is configured to cover the heat insulating material with a cover film. The cover film is formed of a first film and a second film, and the first film and the second film are joined over the entire circumference.

[0003] Japanese Patent Application Laid-Open No. 2023-53818, Japanese Patent Application Laid-Open No. 2024-120378, Japanese Patent Application Laid-Open No. 2009-287586

[0004] In order to join the first film and the second film, it is necessary to overlap the first film and the second film. This overlapping portion has a shape that extends outward from the peripheral surface of the heat insulating material housed inside, that is, a flange shape. Due to the overlapping portion, the overall size of the spacer increases. Furthermore, since the overlapping portion is not easy to dimensionally control, it is not easy to place the spacer at a desired position.

[0005] The present disclosure has been made in view of such a background, and aims to provide a spacer, a method for manufacturing the spacer, and an assembled battery that can be miniaturized and can be easily positioned with high precision.

[0006] One aspect of the present disclosure is a spacer disposed opposite an object, comprising: an insulating material having a first surface facing the object and a second surface which is the back surface of the first surface; a cover having a first cover portion that covers the first surface of the insulating material and a second cover portion that covers the second surface of the insulating material, housing the insulating material in an internal space formed by the first cover portion and the second cover portion, and having an overlapping portion in which the first cover portion and the second cover portion are arranged in overlapping positions at a part of the periphery; and a seal line that seals the overlapping portion of the cover, wherein the cover comprises: the overlapping portion which forms a part of the periphery and covers a part of the circumferential surface of the insulating material; and a continuous portion which forms another part of the periphery, is formed continuously without the first cover portion and the second cover portion overlapping, and covers another part of the circumferential surface of the insulating material.

[0007] Another aspect of the present disclosure is a method for manufacturing the spacer, wherein the cover is formed of a shrink film that shrinks when heated, the insulating material is inserted into the internal space of the cover from the overlapping portion of the cover, the seal line is formed by sealing the overlapping portion, the cover is shrunk by heating the cover, and the shrunk cover is placed along the surface of the insulating material.

[0008] Another aspect of the present disclosure is a battery pack comprising: a housing including a bottom surface; a battery cell which is the object housed in the housing; and a spacer which is housed in the housing and positioned opposite the battery cell, wherein the continuous portion is located opposite the bottom surface.

[0009] According to the spacer, the periphery of the cover includes an overlapping portion and a continuous portion. The overlapping portion is sealed by a sealing wire. The continuous portion is formed so as not to have an opening, since the first cover portion and the second cover portion are originally continuous. Thus, the periphery of the cover includes an overlapping portion that is sealed by a sealing wire and a continuous portion that does not need to be sealed by a sealing wire.

[0010] The overlapping portion has a shape that extends outward from the circumferential surface of the insulation material, i.e., a flange shape. On the other hand, the continuous portion has a smaller outward protrusion from the circumferential surface of the insulation material compared to the overlapping portion. Therefore, the spacer can be made smaller where the continuous portion is located. Furthermore, by positioning at the continuous portion, the spacer can be positioned with high precision.

[0011] According to the method for manufacturing the spacer, the spacer can be reliably manufactured. Furthermore, because the battery pack includes the spacer, it exhibits the aforementioned effects.

[0012] Based on the above, it is possible to provide a spacer that can be miniaturized and easily positioned with high precision, a method for manufacturing the spacer, and a battery pack.

[0013] Figure 1 is a cross-sectional view showing a battery pack in Embodiment 1. Figure 2 is a perspective view of a spacer constituting the battery pack. Figure 3 is a view of the spacer from the flattened planar direction. Figure 4 is an enlarged cross-sectional view taken along line IV-IV in Figure 3. Figure 5 is an enlarged cross-sectional view taken along line V-V in Figure 3. Figure 6 is an enlarged schematic diagram showing the thermal insulation material constituting the spacer. Figure 7 is an enlarged schematic diagram showing a part of the inorganic particles constituting the thermal insulation material. Figure 8 is a flowchart showing the method for manufacturing the spacer in Embodiment 1. Figure 9 is a diagram illustrating S1 in Figure 8. Figure 10 is a diagram illustrating the heating tool in S2 in Figure 8, where (a) in Figure 10 is a plan view and (b) in Figure 10 is a cross-sectional view taken along line B-B. Figure 11 is a diagram illustrating S2 in Figure 8, where (a) in Figure 11 is a plan view and (b) in Figure 11 is a cross-sectional view taken along line B-B. Figure 12 is a diagram illustrating S3 in Figure 8, where (a) in Figure 12 is a plan view and (b) in Figure 12 is a cross-sectional view taken along line B-B. Figure 13 is a diagram illustrating S4 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 14 is a diagram illustrating S5 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 15 is a diagram illustrating S6 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 16 is a perspective view of the spacer in Embodiment 2. Figure 17 is a view of the spacer in Embodiment 2 from the direction of the flattened plane. Figure 18 is a diagram illustrating S1 in Figure 8 in the method for manufacturing the spacer in Embodiment 2. Figure 19 is a diagram illustrating the heating tool in S2 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 20 is a diagram illustrating S2 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 21 is a diagram illustrating S3 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 22 is a diagram illustrating S4 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 23 is a diagram illustrating S5 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B. Figure 24 is a diagram illustrating S6 in Figure 8, where (a) is a plan view and (b) is a cross-sectional view along B-B.

[0014] (Embodiment 1) 1. Battery pack 1 The battery pack 1 will be described with reference to Figure 1. The battery pack 1 includes a housing 2, a plurality of battery cells 3, a plurality of spacers 4, and a bus bar 5.

[0015] The housing 2 includes at least a bottom surface 11. The bottom surface 11 is not limited to being located downwards in the vertical direction, but may be located in other positions. The housing 2 further includes a pair of side walls 12 and 13. Multiple battery cells 3 are arranged on the bottom surface 11. The bottom surface 11 may include a heat conductive member or a cooling member to cool the battery cells 3. The pair of side walls 12 and 13 are arranged opposite each other in the left-right direction of Figure 1, and are configured to sandwich the arranged multiple battery cells 3 from both sides. The pair of side walls 12 and 13 are formed of, for example, metal or resin. The housing 2 may also include a pair of side walls that are opposite each other in the direction normal to the plane of the paper in Figure 1.

[0016] The bottom surface 11 and the pair of side walls 12 and 13 that constitute the housing 2 may be made of different materials or of the same material.

[0017] Multiple battery cells 3 are housed in a housing 2. The multiple battery cells 3 are arranged on the bottom surface 11 of the housing 2, between a pair of side walls 12 and 13. Each battery cell 3 is positioned vertically with respect to the bottom surface 11 of the housing 2. Each battery cell 3 is formed in a flattened shape. The flattened surfaces of the battery cells 3 are arranged to face each other. The shape of the outer circumferential surface of the battery cell 3 (the contour shape viewed from the normal direction of the flattened surface) is arbitrary. For example, the shape of the outer circumferential surface of the battery cell 3 is formed in a polygon, such as a rectangle.

[0018] The battery cell 3 is, for example, a rechargeable storage battery (also called a secondary battery). The battery cell 3 is one selected from the group, for example, lithium-ion batteries, lead-acid batteries, nickel-metal hydride batteries, nickel-cadmium batteries, and all-solid-state batteries. The battery cell 3 generates heat during charging and discharging. The heat generated by the battery cell 3 is transferred, for example, to the bottom surface 11 of the housing 2. In this way, the battery cell 3 is cooled.

[0019] Furthermore, the battery cell 3 expands when charged and contracts when discharged. Therefore, the battery cell 3 repeatedly expands and contracts as charging and discharging are repeated. Here, as described above, the battery cell 3 is formed in a flattened shape. Therefore, the battery cell 3 mainly expands and contracts in the direction normal to the flattened plane (left-right direction in Figure 1).

[0020] The battery cell 3 includes a cell housing (not shown) made of, for example, metal or resin, and a cell body (not shown) housed in the cell housing. The battery cell 3 expands and contracts in accordance with the expansion and contraction of the cell body. The structure of the battery cell 3 is known and therefore omitted.

[0021] Multiple spacers 4 are housed in the housing 2. Each spacer 4 is formed in a flattened shape. For example, the thickness of a spacer 4 is thinner than the thickness of a battery cell 3. Some of the multiple spacers 4 are sandwiched between adjacent battery cells 3. Other parts of the multiple spacers 4 are sandwiched between the battery cells 3 and the side walls 12 and 13, respectively. In other words, at least one side of each spacer 4 is positioned facing the battery cell 3. At least one side of each spacer 4 may be in direct contact with the battery cell 3, or it may be positioned between the spacer 4 and the battery cell 3 via other members such as heat transfer members or thickness adjustment members.

[0022] The spacers 4, like the battery cells 3, are positioned on the bottom surface 11 of the housing 2, between the pair of side walls 12 and 13. Each spacer 4 is positioned vertically with respect to the bottom surface 11 of the housing 2. If the normal to the bottom surface 11 of the housing 2 is horizontal, each spacer 4 is positioned horizontally.

[0023] Spacer 4 has thermal insulation properties. In other words, spacer 4 suppresses the transfer of heat from one adjacent battery cell 3 to the opposite battery cell 3. If heat from one battery cell 3 is transferred to an adjacent battery cell 3, it may cause a heat chain reaction. As a result, the lifespan of the battery cell 3 will decrease. Therefore, the thermal insulation properties of spacer 4 help to suppress the reduction in the lifespan of the battery cell 3.

[0024] Furthermore, it is preferable that the spacer 4 is elastic. As described above, the battery cell 3 expands and contracts with charging and discharging. When the battery cell 3 expands and contracts, the spacer 4 is required to hold the battery cell 3 within a predetermined pressure range. This helps to suppress the reduction in the lifespan of the battery cell 3. Therefore, the spacer 4 is formed to have a predetermined elastic force when it deforms in accordance with the expansion and contraction of the battery cell 3.

[0025] The busbar 5 is positioned on top of the multiple battery cells 3, spanning across the multiple battery cells 3. The busbar 5 is made of an electrically conductive material and is electrically connected to the electrodes of the battery cells 3. Note that the busbar 5 is not limited to being positioned above the battery cells 3, but may also be positioned on the sides.

[0026] 2. Spacer 4 The spacer 4 will be described with reference to Figures 2 to 5. In Figures 2 and 3, the vertical direction coincides with the vertical direction in Figure 1. Therefore, the lower end of the spacer 4 shown in Figures 2 and 3 is supported by the bottom surface 11 of the housing 2 shown in Figure 1.

[0027] The spacer 4 includes an insulating material 21 (shown in Figures 4 and 5), a cover 22, and a sealing wire 23. However, the spacer 4 may also include elements other than those described above (elements 21 to 23).

[0028] The thermal insulation material 21 is formed in a flattened shape. Preferably, the contour shape of the thermal insulation material 21, when viewed from the direction normal to the flattened surface, corresponds to the outer shape of the battery cell 3. However, it is preferable that the thermal insulation material 21 has a shape that is slightly smaller than the outer shape of the battery cell 3. For example, the thermal insulation material 21 is formed in a polygon, such as a rectangle.

[0029] As shown in Figures 4 and 5, the thermal insulation material 21 includes a first surface 21a and a second surface 21b that are facing away from each other and constitute a flattened surface. The first surface 21a faces the flattened surface of the battery cell 3. The second surface 21b is the back surface of the first surface 21a. However, if the spacer 4 is sandwiched between adjacent battery cells 3, the second surface 21b also faces the flattened surface of the battery cell 3. The first surface 21a and the second surface 21b are formed into any shape, such as a rectangle. The thermal insulation material 21 also includes a circumferential surface 21c. If the first surface 21a and the second surface 21b are rectangular, there are four circumferential surfaces 21c.

[0030] The thermal insulation material 21 can be made from various materials as long as they have thermal insulation properties. The thermal insulation material 21 may exhibit thermal insulation properties through the materials that make it up, for example, or it may exhibit thermal insulation properties by holding a gas such as air inside. The thermal insulation material 21 may contain multiple particles, for example. The thermal insulation material 21 may be made up of multiple particles bonded together as a single unit, or the multiple particles may be arranged independently.

[0031] Furthermore, the thermal insulation material 21 may include materials with various purposes in addition to materials having thermal insulation properties. For example, the thermal insulation material 21 may include reinforcing materials to improve the strength of the thermal insulation material 21, or base materials to hold the thermal insulation material. Examples of reinforcing materials include reinforcing fibers. Reinforcing fibers can be inorganic fibers such as glass fibers or organic fibers such as resin fibers. In addition to being thread-like, reinforcing fibers can also be formed into, for example, woven fabrics or nonwoven fabrics.

[0032] The cover 22 is formed from a flexible sheet. The cover 22 includes a first cover portion 22a that covers the first surface 21a of the heat insulating material 21, and a second cover portion 22b that covers the second surface 21b of the heat insulating material 21. The first cover portion 22a and the second cover portion 22b are made from a single sheet. For example, the cover 22 is formed in a cylindrical shape. That is, the cover 22 is formed in a cylindrical shape with openings at both ends when it is not sealed by the sealing wire 23.

[0033] The cover 22 houses the thermal insulation material 21. That is, the thermal insulation material 21 is housed in the internal space 22c formed by the first cover portion 22a and the second cover portion 22b. The cover 22 may have a shape that conforms to the surface of the thermal insulation material 21. If there is no intervening material between the cover 22 and the thermal insulation material 21, the cover 22 adheres tightly to the surface of the thermal insulation material 21. If there is an intervening material between the cover 22 and the thermal insulation material 21, the cover 22 adheres tightly to the intervening material. However, the cover 22 may be positioned with a gap between it and the surface of the thermal insulation material 21.

[0034] As shown in Figures 2 to 5, the cover 22 includes an overlapping portion 22d and a continuous portion 22e at its periphery.

[0035] As shown in Figures 2 to 4, the overlapping portion 22d is formed by overlapping the first cover portion 22a and the second cover portion 22b. In the overlapping portion 22d, the first cover portion 22a and the second cover portion 22b are overlapped in the direction of their respective surface normals. In other words, the overlapping portion 22d has a shape that extends outward from the circumferential surface of the insulation material 21, i.e., a flange shape. The overlapping portion 22d is formed on a part of the periphery of the cover 22. The overlapping portion 22d covers a part of the circumferential surface of the insulation material 21.

[0036] In Figures 2 and 3, the cover 22 is formed in a cylindrical shape. Therefore, the cover 22 includes a pair of overlapping portions 22d. That is, the overlapping portions 22d are located at both ends of the cylindrical shape of the cover 22. The overlapping portions 22d are located at positions corresponding to the left and right sides of the thermal insulation material 21. The overlapping portions 22d are not located opposite the bottom surface 11 of the housing 2, and are located at positions other than the bottom surface 11.

[0037] Furthermore, in the overlapping portion 22d, the surfaces of the first cover portion 22a and the second cover portion 22b may be in direct contact, provided that no intervening material is present between them. Alternatively, an intervening material (not shown) may be placed between the first cover portion 22a and the second cover portion 22b in the overlapping portion 22d. In this case, the layers would be stacked in the order of the first cover portion 22a, the intervening material (not shown), and the second cover portion 22b.

[0038] As shown in Figures 2, 3, and 5, the continuous portion 22e is formed continuously between the first cover portion 22a and the second cover portion 22b without overlapping. In other words, the continuous portion 22e corresponds to the part where the boundary between the first cover portion 22a and the second cover portion 22b cannot be clearly defined. The continuous portion 22e is formed on another part of the periphery of the cover 22. The continuous portion 22e covers another part of the circumferential surface of the heat insulating material 21. In Figures 2 and 3, the cover 22 includes a pair of continuous portions 22e. That is, the continuous portion 22e is located at a position corresponding to a pair of upper and lower sides of the heat insulating material 21. The continuous portion 22e is located opposite the bottom surface 11 of the housing 2.

[0039] The purpose of enclosing the insulation material 21 with the cover 22 is optional. For example, the cover 22 may serve to protect the surface of the insulation material 21. Also, if the insulation material 21 is formed of multiple particles, the cover 22 may function as a component to prevent dust generation from the insulation material 21. The cover 22 may also function to maintain the shape of the insulation material 21.

[0040] The cover 22 may be formed from a sheet without through holes. However, the cover 22 may have fine through holes.

[0041] The material of the cover 22 can be, for example, resin, cloth, paper, or metal. The cover 22 may be formed from a single material or may have a multi-layer structure made of multiple different materials. For example, the cover 22 may have a structure formed from a metal layer and a resin layer, a structure formed from a cloth layer containing resin and a metal layer, or a structure formed from a resin layer and a cloth layer.

[0042] The resin may include a thermoplastic resin. Examples of such resins include polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polyethylene terephthalate (PET). Examples of fabrics include woven fabrics and nonwoven fabrics. The fibers of the fabric may include the aforementioned thermoplastic resin.

[0043] The thickness of the cover 22 is not particularly limited. Also, the thickness of the cover 22 varies depending on the material. For example, the thickness of the cover 22 is 5 μm to 1 mm.

[0044] The cover 22 may be formed of a shrink film that shrinks upon heating. In this case, the cover 22 can be formed in a shape along the surface of the heat insulating material 21. Note that the cover 22 may be formed of a resin film other than the shrink film.

[0045] The seal line 23 seals the overlapping portion 22d of the cover 22. The overlapping portion 22d has an opening between the first cover portion 22a and the second cover portion 22b in the unsealed state. That is, the seal line 23 seals the opening. In this way, the seal line 23 seals the overlapping portion 22d by joining the first cover portion 22a and the second cover portion 22b. The first cover portion 22a and the second cover portion 22b may be joined directly or through an intervening substance. Examples of the joining means by the seal line 23 include welding and joining with a joining material. Examples of welding include thermal welding, high-frequency welding, ultrasonic welding, and laser welding. The material of the cover 22 is selected according to the joining means. When joining by welding is applied, the cover 22 preferably contains a thermoplastic resin.

[0046] As described above, the overlapping portion 22d is located at both ends of the tubular shape in the cover 22. Therefore, as shown in FIGS. 2 and 3, the seal line 23 seals the overlapping portion 22d located at both ends of the tubular shape in the cover 22.

[0047] For example, when forming the cover 22 in a shape along the surface of the heat insulating material 21, the dimensions of the sealing line 23 can be as follows. In the extending direction of the sealing line 23 (the vertical direction in FIG. 3), the length L23 of the sealing line 23 coincides with the length of the overlapping portion 22d. Also, in the extending direction of the sealing line 23, the length L23 of the sealing line 23 is preferably shorter than the distance between a pair of continuous portions 22e of the cover 22 (the distance between the outer surfaces of the pair of continuous portions 22e) L22e. Furthermore, in the extending direction of the sealing line 23, the length L23 of the sealing line 23 is preferably shorter than the length L21 of the heat insulating material 21.

[0048] And in the extending direction of the sealing line 23, the end portion of the sealing line 23 does not protrude outside the continuous portion 22e located in the vicinity. That is, in the extending direction of the sealing line 23, the end portion of the sealing line 23 is located inside the continuous portion 22e located in the vicinity.

[0049] By setting the length L23 of the sealing line 23 to the above dimensions, the sealing line 23 does not contact the bottom surface 11 of the housing 2 and does not affect the positioning of the spacer 4.

[0050] The line width of the sealing line 24 can be, for example, 0.2 mm to 10.0 mm. The line width of the sealing line 24 is preferably 0.3 mm to 3.0 mm, and more preferably 0.3 mm to 1.0 mm.

[0051] 3. Example of the heat insulating material 21 As described above, in addition to having heat insulating performance, the spacer 4 preferably has elasticity. Thereby, when the battery cell 3 expands and contracts, the spacer 4 can hold the battery cell 3 within a predetermined pressure range. In this case, the heat insulating material 21 may be formed of a material having heat insulating performance and elasticity.

[0052] As described above, various materials can be used for the heat insulating material 21 as long as it has heat insulating performance. Regarding the case where the heat insulating material 21 is formed of a material having heat insulating performance and elasticity as an example of the heat insulating material 21, it will be described with reference to FIGS. 6 and 7.

[0053] As shown in Figure 6, the thermal insulation material 21 is manufactured by pressure molding a composition having a porous structure powder 31.

[0054] As shown in Figure 7, the porous structure has a framework formed by the linkage of multiple primary particles 31a, with pores 31b between the framework. The diameter of the primary particles 31a forming the framework is preferably about 2 to 5 nm, and the size of the pores 31b formed between the framework is preferably about 10 to 50 nm. If most of the pores 31b are so-called mesopores with a size of 50 nm or less, the mesopores are smaller than the mean free path of air, thus restricting air convection and inhibiting heat transfer. The primary particles 31a (inorganic particles) forming the framework are mainly composed of inorganic materials such as silica, alumina, zirconia, and titania. A porous structure in which the primary particles are silica is preferred because of its excellent chemical stability.

[0055] An example of a porous structure is silica aerogel. Depending on the drying method used in the production of aerogel, those dried at atmospheric pressure are sometimes called "xerogels," and those dried under supercritical conditions are sometimes called "aerogels," but both are referred to as "aerogels." Silica aerogels are suitable because they have a good balance between the size of the skeleton and the size of the pores. Silica aerogels are produced, for example, by a sol-gel reaction of a solution containing two or more silane compounds with different numbers of siloxane bonds (hereinafter sometimes referred to as "silane compound-containing solution").

[0056] In addition to silica aerogel, the following can also be used as porous structures. A cohesive structure in which nanoparticles with a particle size of less than 1 μm are linked together to form a framework is also suitable. Examples of nanoparticles include fumed silica, wet silica, and those obtained by crushing or dispersing these, as well as those produced from nanoparticle sols such as colloidal silica and colloidal alumina.

[0057] In Figure 6, the porous structure powder 31 constituting the pressure-molded body consists of particles of different shapes and sizes obtained by grinding a porous structure manufactured by the sol-gel method. For the grinding process, a media-less grinding and mixing device such as a jet mill or a stirrer may be used. The porous structure takes on various shapes after grinding, but shapes other than spherical are desirable.

[0058] The average particle size of the porous structure powder 31 is preferably 30 μm or larger from the viewpoint of increasing the pore volume and improving heat insulation. Powders with an average particle size of less than 30 μm are difficult to obtain by grinding, and fine voids tend to form between the particles, which may make the press-molded product brittle. A suitable average particle size is 50 μm or larger. On the other hand, from the viewpoint of ease of molding into a sheet and suppression of particle shedding, the average particle size is preferably 150 μm or less. Powders with an average particle size exceeding 150 μm do not tend to form voids between particles, but the size of the voids tends to be large. A suitable average particle size is 120 μm or less. The average particle size of the porous structure powder is determined by the median diameter (D) obtained from the volume-based particle size distribution measured by laser diffraction / scattering. ５０ ) should be adopted.

[0059] The composition having the porous structure powder 31 may consist only of the porous structure powder 31, or it may contain other components. From the viewpoint of ensuring the desired thermal insulation performance of the thermal insulation material 21, the content of the porous structure powder in the composition shall be 65% by mass or more, preferably 70% by mass or more, when the solid content of the composition is 100% by mass. Here, the solid content refers to the components excluding volatile substances such as organic solvents and water. Other components include, for example, infrared shielding particles, inorganic fibers, dispersants, reinforcing inorganic particles, and flame retardants. Furthermore, from the viewpoint of easily achieving the desired filling state and porosity of the porous structure powder 31 in the thermal insulation material 21, which is a pressure-molded body, it is desirable that the composition does not contain a binder that binds the components of the pressure-molded body, such as the porous structure powder 31.

[0060] As shown in Figure 6, in a thermal insulation material 21 obtained by pressure molding a composition having porous structure powder 31, it is desirable that the porous structure powder 31 be in a randomly stacked form. In the thermal insulation material 21, multiple porous structure powders 31 are arranged to be stacked on top of each other.

[0061] Many of the porous structure powders 31 have shapes other than spherical, and their individual shapes and sizes differ. The packing state of the porous structure powders 31 is similar to the "nozurazumi" style found in the stone walls of Japanese castles. "Nozurazumi" is a stone masonry method in which natural stones or roughly cut stones are stacked without processing. There are small gaps 32 between the porous structure powders 31. The porous structure powders 31 come into contact with each other at points, lines, or surfaces, or a combination thereof, and there is no regularity in their arrangement. Therefore, when compressed from the outside in the thickness direction, the porous structure powders 31 move and deform by shifting from one another. In addition, because the porous structure powders 31 are elastic, they deform while generating a desired reaction force when the insulation material 21 is compressed, and return to their original shape when unloaded.

[0062] The amount of voids in the thermal insulation material 21 affects its thermal insulation properties. When the amount of voids 32 increases, i.e., the porosity increases, heat transfer due to air convection increases, thus reducing thermal insulation properties. Therefore, if only thermal insulation properties are considered, it is desirable to have no voids 32. However, if the amount of voids 32 is small, the powder 31 of the porous structure may not shift easily when compressed from the outside, potentially resulting in a smaller deformation. Conversely, if the amount of voids 32 is too large, the number of contact points formed by points, lines, and surfaces of the porous structure, or a combination thereof, decreases, making it difficult for the elasticity of the porous structure to be exhibited, potentially reducing the recovery rate. Therefore, in the thermal insulation material 21, the porosity was set to 20% or less, taking into consideration thermal insulation properties, deformability, and recovery properties. A suitable porosity is 15% or less.

[0063] 4. Effects of Spacer 4 The periphery of the cover 22 of spacer 4 includes an overlapping portion 22d and a continuous portion 22e. The overlapping portion 22d is sealed by a sealing wire 23. The continuous portion 22e is formed so as not to open, as the first cover portion 22a and the second cover portion 22b are originally continuous. Thus, the periphery of the cover 22 includes an overlapping portion 22d that is sealed by the sealing wire 23 and a continuous portion 22e that does not need to be sealed by the sealing wire 23.

[0064] The overlapping portion 22d has a shape that extends outward from the circumferential surface of the insulation material 21, i.e., a flange shape. On the other hand, the continuous portion 22e has a smaller outward protrusion from the circumferential surface of the insulation material 21 compared to the overlapping portion 22d. Therefore, the spacer 4 can be made smaller at the location where the continuous portion 22e is located. Furthermore, by positioning at the continuous portion 22e, the spacer 4 can be positioned with high precision.

[0065] Furthermore, in the direction of extension of the sealing wire 23, the end of the sealing wire 23 does not protrude outward (up and down in Figure 3) beyond the continuous portion 22e. In other words, in the direction of extension of the sealing wire 23, the end of the sealing wire 23 is located inward from the continuous portion 22e. This allows the spacer 4 to be positioned with high precision without the sealing wire 23 contacting the bottom surface 11 of the housing 2. In particular, the effect is ensured by making the length L23 of the sealing wire 23 shorter than the distance L22e between the pair of continuous portions 22e. Furthermore, the effect is enhanced by making the length L23 of the sealing wire 23 shorter than the length L21 of the heat insulating material 21.

[0066] Furthermore, when the cover 22 is not sealed by the sealing wire 23, it is formed in a cylindrical shape with overlapping portions 22d at both ends. In this case, the sealing wire 23 seals the overlapping portions 22d located at both ends of the cylindrical shape of the cover 22. This reduces the number of positions where the sealing wire 23 is formed, making it easier to secure a continuous portion 22e.

[0067] Furthermore, the cover 22 has a shape that conforms to the surface of the heat insulating material 21. In particular, because the cover 22 is formed of a shrink film that shrinks when heated, it is easy to make the cover 22 conform to the surface of the heat insulating material 21. The cover 22 is also designed to be in close contact with the heat insulating material 21. The cover 22 can also be in close contact with an intervening material.

[0068] 5. Manufacturing Method of Spacer 4 The manufacturing method of spacer 4 will be explained with reference to Figures 8 to 15.

[0069] As shown in Figure 9, the material 40 for the spacer 4 is prepared. The material 40 for the spacer 4 includes a cover material 41 corresponding to the first cover portion 22a and the second cover portion 22b, and an insulating material 21. The cover material 41 is formed in a cylindrical shape with openings at both ends. Therefore, the cover material 41 has an internal space 41a. In the cover material 41, the portion that forms the cylindrical shape is formed continuously. The cover material 41 is made of a shrink film that shrinks when heated.

[0070] The method for manufacturing the cylindrical cover material 41 is not particularly limited. For example, the cover material 41 may be formed into a cylindrical shape by extrusion molding. Alternatively, the cover material 41 may be formed into a cylindrical shape by overlapping both ends using, for example, a sheet-like film, by heat welding such as line welding or surface welding, as well as ultrasonic welding or electrostatic sealing.

[0071] As shown in Figure 10, a heating tool 50 is prepared. The heating tool 50 includes a lower mold 51, an upper mold 52, and a heating section 53. The lower mold 51 is formed so that the material 40 of the spacer 4 can be placed on it. The upper mold 52 corresponds to the lower mold 51 and is formed in a shape that covers it.

[0072] The heating section 53 is held in the upper mold 52 and protrudes downward from the lower surface of the upper mold 52. The heating section 53 has two straight lines. The heating section 53 is formed in a shape corresponding to the sealing line 23. However, the line width of the heating section 53 is formed to be larger than the line width of the sealing line 23.

[0073] Then, as shown in Figures 8 and 9, the material 40 of the spacer 4 is placed. In other words, the heat insulating material 21 is inserted into the internal space 41a of the cover material 41 (S1: material placement step). The internal space 41a corresponds to the internal space 22c of the cover 22.

[0074] Next, as shown in Figures 8 and 11, the material 40 of the spacer 4 is placed on the heating tool 50 (S2: tool placement step). At this time, the portion of the periphery of the material 40 of the spacer 4 where the cover material 41 overlaps is supported by the lower mold 51. Furthermore, the portion where the heat insulating material 21 is present may also be supported by the lower mold 51.

[0075] Next, as shown in Figures 8 and 12, a predetermined portion of the material 40 of the spacer 4 is sealed by heating with the heating tool 50 (S3: sealing process). As a result, a portion of the overlapping portion of the cover material 41 is heated and sealed. In other words, the portion of the overlapping portion of the cover material 41 corresponding to the heating portion 53 is sealed by heat welding. In this way, a portion corresponding to the seal line 23 is formed. The sealing process can be carried out, for example, by performing surface welding using a heat sealer to weld together a portion of the surface of the cover material 41.

[0076] Next, as shown in Figures 8 and 13, the material 40 of the spacer 4 is removed from the heating tool 50 (S4: removal step). Subsequently, as shown in Figures 8 and 14, the sealed portion of the material 40 of the spacer 4 is cut (S5: cutting step).

[0077] Next, as shown in Figures 8 and 15, the cover material 41 (cover 22) is heated to shrink it (S6: shrinkage step). In this way, the shrunk cover 22 is formed to conform to the surface of the heat insulating material 21, and the spacer 4 is completed.

[0078] The spacer 4 can be manufactured using the described manufacturing method. Although the manufacturing method for forming the seal line 23 by heat welding has been described, similar methods can be applied to other methods for forming the seal line 23. Also, it is not necessary to cut the outer edge of the cover 22 in the cutting step S5.

[0079] In the above manufacturing method, the sealing step S3 and the cutting step S5 were treated as separate steps. Alternatively, the cutting step S5 may be performed simultaneously with the sealing step S3. For example, the cutting step S5 by thermal cutting can be performed in conjunction with the sealing step S3, which seals the cylindrical cover material 41 by heat welding or ultrasonic welding.

[0080] (Embodiment 2) The spacer 104 and its manufacturing method in Embodiment 2 will be described with reference to Figures 8 and 16 to 24. In Embodiment 2, reference numerals that are the same as those used in previously described embodiments represent the same components as those in the previously described embodiments, unless otherwise specified.

[0081] The spacer 104 will be described with reference to Figures 16 and 17. In Figures 16 and 17, the vertical direction coincides with the vertical direction in Figure 1. Therefore, the lower end of the spacer 4 shown in Figures 16 and 17 is supported by the bottom surface 11 of the housing 2 shown in Figure 1.

[0082] The spacer 104 includes an insulating material 21 (shown in Figure 4), a cover 122, and a sealing wire 123. However, the spacer 104 may also include elements other than the aforementioned elements 21, 122, and 123.

[0083] The cover 122 is formed in the shape of a single sheet when not sealed by the sealing line 123. The cover 122 includes a first cover portion 122a and a second cover portion 122b. The cover 122 houses the thermal insulation material 21. That is, the thermal insulation material 21 is housed in the internal space 122c formed by the first cover portion 122a and the second cover portion 122b.

[0084] The cover 122 includes an overlapping portion 122d and a continuous portion 122e at its periphery. The overlapping portion 122d is located on a pair of opposing sides of the cover 122 and on one side connecting the pair of opposing sides. In other words, the overlapping portion 122d is located on three of the four sides of the thermal insulation material 21 in a U-shape. The overlapping portion 122d is not located in a position opposite to the bottom surface 11 of the housing 2, and is located in a position corresponding to a position other than the bottom surface 11. The continuous portion 122e is located in a position corresponding to the bottom edge of the thermal insulation material 21. The continuous portion 122e is located in a position opposite to the bottom surface 11 of the housing 2.

[0085] The sealing wire 123 seals the overlapping portion 122d of the cover 122. The sealing wire 123 is positioned on three of the four sides of the heat insulating material 21 in a U-shape. The U-shaped ends of the sealing wire 123 do not protrude outward (downward in Figure 17) from the continuous portion 122e in the direction of extension of the sealing wire 123 (up and down direction in Figure 17: direction of extension of the end portion of the sealing wire 123). In other words, the ends of the sealing wire 123 are located inward from the continuous portion 122e in the direction of extension of the sealing wire 123. By setting the ends of the sealing wire 123 to the above dimensions, the spacer 104 can be positioned with high precision without the sealing wire 123 coming into contact with the bottom surface 11 of the housing 2.

[0086] The manufacturing method of the spacer 104 will be explained with reference to Figures 8 and 18 to 24.

[0087] As shown in Figure 18, the material 140 for the spacer 104 is prepared. The material 140 for the spacer 104 includes a cover material 141 corresponding to the first cover portion 122a and the second cover portion 122b, and an insulating material 21. The cover material 141 is formed in the shape of a single sheet. By folding the cover material 141, the cover material 141 has an internal space 141a. In the cover material 141, the folded portion is formed continuously. The cover material 141 is formed of a shrink film that shrinks when heated.

[0088] As shown in Figure 19, a heating tool 150 is prepared. The heating tool 150 includes a lower mold 151, an upper mold 152, and a heating section 153. The lower mold 151 is formed so that the material 140 of the spacer 104 can be placed on it. The upper mold 152 corresponds to the lower mold 151 and is formed in a shape that covers it.

[0089] The heating section 153 is held in the upper mold 152 and protrudes downward from the lower surface of the upper mold 152. The heating section 153 has a U-shape. The heating section 153 is formed in a shape corresponding to the sealing line 123. However, the line width of the heating section 153 is formed to be larger than the line width of the sealing line 123.

[0090] Then, as shown in Figures 8 and 18, the material 140 of the spacer 104 is placed. That is, the heat insulating material 21 is placed in the internal space 141a formed by the folded cover material 141 (S11: material placement step). The internal space 141a corresponds to the internal space 122c of the cover 122.

[0091] Next, as shown in Figures 8 and 20, the material 140 of the spacer 104 is placed on the heating tool 150 (S12: tool placement step). At this time, the portion of the periphery of the material 140 of the spacer 104 where the cover material 141 overlaps is supported by the lower mold 151. Furthermore, the portion where the heat insulating material 21 is present may also be supported by the lower mold 151.

[0092] Next, as shown in Figures 8 and 21, the heating tool 150 is used to heat and seal a predetermined portion of the spacer material 140 (S13: sealing step). As a result, a portion of the overlapping portion of the cover material 141 is heated and sealed. In other words, the portion of the overlapping portion of the cover material 141 corresponding to the heating portion 153 is sealed by heat welding. In this way, a portion corresponding to the seal line 123 is formed. The portion corresponding to the seal line 123 is located on three sides of the periphery of the heat insulating material 21.

[0093] Next, as shown in Figures 8 and 22, the material 140 of the spacer 104 is removed from the heating tool 150 (S14: removal step). Subsequently, as shown in Figures 8 and 23, the sealed portion of the material 140 of the spacer 104 is cut (S15: cutting step). The cutting points are located on three sides of the periphery of the insulation material 21.

[0094] Next, as shown in Figures 8 and 24, the cover material 141 (cover 122) is heated to shrink it (S16: shrinkage step). In this way, the shrunk cover 122 is formed to conform to the surface of the heat insulating material 21, and the spacer 104 is completed.

[0095] (Other embodiments) In the above embodiment, the spacers 4 and 104 were positioned facing the battery cell 3, which is the object of the design. The object on which the spacers 4 and 104 are placed is not limited to the battery cell 3; the spacers 4 and 104 can be positioned facing other objects that require thermal insulation performance.

Claims

1. A spacer positioned opposite an object, comprising: an insulating material having a first surface facing the object and a second surface which is the back surface of the first surface; a cover having a first cover portion that covers the first surface of the insulating material and a second cover portion that covers the second surface of the insulating material, housing the insulating material in the internal space formed by the first cover portion and the second cover portion, and having an overlapping portion in which the first cover portion and the second cover portion are overlapped at a part of the periphery; and a sealing line that seals the overlapping portion of the cover, wherein the cover comprises: the overlapping portion which forms a part of the periphery and covers a part of the circumferential surface of the insulating material; and a continuous portion which forms another part of the periphery, where the first cover portion and the second cover portion are formed continuously without overlapping and cover another part of the circumferential surface of the insulating material.

2. The spacer according to claim 1, wherein the cover is formed in a cylindrical shape having overlapping portions at both ends when not sealed by the sealing wire, and the sealing wire seals the overlapping portions located at both ends of the cylindrical shape of the cover.

3. The spacer according to claim 2, wherein the cover comprises a pair of continuous portions, and in the direction of extension of the seal line, the length of the seal line is shorter than the distance between the pair of continuous portions.

4. The spacer according to claim 1, wherein the end of the sealing wire is located inside the continuous portion in the direction of extension of the sealing wire.

5. The spacer according to any one of claims 1 to 4, wherein the cover has a shape that conforms to the surface of the heat insulating material.

6. The spacer according to claim 5, wherein the cover is formed of a shrink film that shrinks when heated.

7. The spacer according to claim 5, wherein the cover is in close contact with the heat insulating material.

8. The spacer according to claim 1, wherein the thermal insulation material is formed of a plurality of inorganic particles.

9. The spacer according to claim 1, wherein the thermal insulation material is elastic.

10. The spacer according to claim 1, wherein the object is a battery cell.

11. A method for manufacturing a spacer according to claim 6, comprising: inserting the heat insulating material into the internal space of the cover from the overlapping portion of the cover; forming the seal line by sealing the overlapping portion; shrinking the cover by heating the cover; and forming the shrunk cover into a shape that conforms to the surface of the heat insulating material.

12. A battery pack comprising: a housing including a bottom surface; a battery cell which is the object housed in the housing; and the spacer according to claim 1, which is housed in the housing and positioned opposite the battery cell, wherein the continuous portion is located opposite the bottom surface.

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