Expandable sheet and battery including the same

Abstract

To provide an expandable sheet and a battery including the same which offer improved insulation and safety.SOLUTION: The present invention relates to an expandable sheet 1 that is placed in a battery box that houses one or more battery cells, and that comprises a resin sheet 3 and a thermosetting rubber sheet 2 laminated together, the thermosetting rubber sheet 2 is a sheet that contains a foaming agent in a thermosetting rubber composition, and that is expandable by absorbing the heat of the battery cells when they overheat. The present invention also relates to a battery that includes the expandable sheet 1.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an expandable sheet and a battery. [Background technology]

[0002] Currently, there is a growing movement around the world to gradually replace conventional gasoline or diesel vehicles with electric vehicles in order to reduce the burden on the global environment. Electric vehicles are becoming increasingly popular, particularly in European countries such as France, the Netherlands, and Germany, as well as in China. The widespread use of electric vehicles requires high-performance batteries.

[0003] Conventionally, automotive batteries have been known in which multiple battery cells (also simply referred to as "cells") are arranged in a housing. The battery cell housings can overheat during discharge and / or charging, and in the worst case scenario, can ignite. To prevent this from happening, methods have been proposed for reducing heat diffusion between battery cells (or battery modules) (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-171373 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the above-mentioned conventionally known methods do not provide sufficient insulation between battery cells. Furthermore, safety is also insufficient in the event of a battery cell explosion. These problems are common not only to automotive batteries, but also to batteries installed in non-automotive vehicles, such as ships or trains, and batteries for small electronic devices, such as mobile phones. Furthermore, solving these problems will contribute to achieving the applicant's Sustainable Development Goal of "ensuring access to affordable, reliable, sustainable, and modern energy for all."

[0006] The present invention has been made to solve the above problems, and has an object to provide an expandable sheet with improved heat insulation properties and safety, and a battery including the same. [Means for solving the problem]

[0007] (1) To achieve the above object, an expandable sheet according to one embodiment is an expandable sheet disposed in a battery box that accommodates one or more battery cells, A resin sheet; a thermosetting rubber sheet; and The thermosetting rubber sheet is a sheet containing a foaming agent in a thermosetting rubber composition, and is capable of foaming upon receiving heat when the battery cell is overheated. (2) In the expandable sheet according to another embodiment, preferably, one thermosetting rubber sheet may be sandwiched between two of the resin sheets. (3) In the expandable sheet according to another embodiment, the thermosetting rubber composition may preferably be a sheet-like thermosetting silicone rubber composition. (4) In the expandable sheet according to another embodiment, the thickness of the thermosetting rubber sheet may be greater than the thickness of the resin sheet. (5) To achieve the above object, an expandable sheet according to one embodiment is an expandable sheet disposed in a battery box that accommodates one or more battery cells, Equipped with a thermosetting rubber sheet, The thermosetting rubber sheet is a sheet containing a foaming agent in a thermosetting rubber composition, and is capable of foaming upon receiving heat when the battery cell is overheated. (6) In the expandable sheet according to another embodiment, the thermosetting rubber composition may preferably be a sheet-like thermosetting silicone rubber composition. (7) In order to achieve the above object, a battery according to one embodiment is a battery having a structure including any one of the expandable sheets described above and one or more battery cells in a battery box, the battery box includes the battery cells in its accommodation space; The expandable sheet is disposed in the gap between the inner surface of the battery box and the outer surface of the battery cell. (8) In the battery according to another embodiment, the expandable sheet may be fixed to either the inner surface or the outer surface. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an expandable sheet with improved heat insulation properties and safety, and a battery including the same. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 shows a perspective view of an intumescent sheet according to one embodiment. [Figure 2] FIG. 2 is a perspective view showing a state in which the battery housing is half-opened from the battery box according to one embodiment, and a state in which an expansive sheet is placed inside the battery. [Figure 3] FIG. 3 shows an enlarged view of the interior of the battery of FIG. 2 and a portion A of the interior. [Figure 4] FIG. 4 is a view similar to FIG. 3 showing a state when a battery cell in the battery of FIG. 2 becomes overheated. [Figure 5] FIG. 5 shows a perspective view of a variation of the intumescent sheet of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] Next, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below do not limit the invention according to the claims, and not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0011] 1. Expandable sheet and its manufacturing method FIG. 1 shows a perspective view of an intumescent sheet according to one embodiment.

[0012] The expandable sheet 1 according to this embodiment is a sheet placed in a battery box that houses one or more battery cells. The expandable sheet 1 is formed by laminating a resin sheet 2 and a thermosetting rubber sheet 3. The thermosetting rubber sheet 3 is a sheet containing a foaming agent in a thermosetting rubber composition, and is capable of foaming when the battery cell overheats by absorbing the heat. There are no particular restrictions on the thickness of the thermosetting rubber sheet 3, and it can be larger or smaller than the thickness of the resin sheet 2, but it is preferably larger than the thickness of the resin sheet 2.

[0013] The term "battery" is broadly interpreted to include not only automotive batteries but also batteries installed in vehicles other than automobiles, such as ships or trains, and batteries for small electronic devices such as mobile phones. The battery box may be of any shape and made of any material, as long as it is a space that can accommodate battery cells.

[0014] The expandable sheet 1 is not particularly limited in its shape or size. The expandable sheet 1 may be in any shape, such as a rectangular parallelepiped, a cylinder, or an elliptical cylinder. A preferred shape for the expandable sheet 1 is a rectangular parallelepiped, particularly a sheet-shaped rectangular parallelepiped with one of its three sides being very small. In this case, the long side (the longest side) is preferably 100 mm or more and 1000 mm or less, more preferably 200 mm or more and 800 mm or less. The short side (the second longest side), provided that it is shorter than the long side, is preferably 50 mm or more and 700 mm or less, more preferably 100 mm or more and 500 mm or less. Furthermore, the thickness (shortest side) is not particularly limited, but is preferably 1.5 mm or more and 40 mm or less, more preferably 3 mm or more and 25 mm or less.

[0015] (1) Resin sheet The resin sheet 2 constituting the expandable sheet 1 may be made of any type of resin, including thermoplastic resin, thermosetting resin, photocurable resin, or electron beam curable resin. Preferred examples of such materials include polypropylene, polyester, polyvinylidene fluoride, polyamide, polycarbonate, polyphenylene sulfide, polyimide, polyetherimide, polytetrafluoroethylene, polyamideimide, phenolic resin, allyl resin, epoxy resin, furan resin, and silicone resin. Polyester is more preferred, and polyethylene terephthalate is even more preferred. The resin sheet 2 may be a sheet containing aromatic polyamide resin fibers (aramid fibers) or a sheet molded from such fibers. The thickness of the resin sheet 2 is not particularly limited, but is preferably 0.5 mm to 10 mm, more preferably 1 mm to 5 mm. The resin sheet 2 is preferably rectangular in plan view, with its long and short sides preferably within the same range as those of the expandable sheet 1.

[0016] (2) Thermosetting rubber sheet The thermosetting rubber sheet 3 constituting the expandable sheet 1 is a sheet that hardens when heated to become a rubber sheet. When not yet heated, it is in an uncured state (which may also be referred to as a semi-cured state) that is not completely hardened. The thermosetting rubber sheet 3 has a thermosetting rubber composition as a matrix, within which a foaming agent (see foaming agent 10 in Figure 3) is dispersed. There are no particular restrictions on the type of thermosetting rubber composition, and preferred examples include rubber compositions that harden to become silicone rubber, acrylic rubber, styrene rubber, butyl rubber, ethylene propylene rubber, or fluororubber. A more preferred thermosetting rubber composition is a sheet-like curable silicone rubber composition. The rubber sheet after hardening of the thermosetting rubber composition is preferably a highly heat-resistant sheet that remains as a foam without melting or sublimating at the melting temperature of the resin sheet 2.

[0017] The foaming agent is not particularly limited as long as it is suitable for use in plastics and rubber materials. Representative examples of foaming agents include azodicarbonamide (ADCA), N,N'-dinitropentamethylenetetramine (DPT), 4,4'-oxybisbenzenesulfonylhydrazide (OBSH), bicarbonate, carbonate, and bicarbonate + organic acid salt. Another example of a foaming agent is thermally expandable resin beads. The foaming temperature of the foaming agent is preferably lower than the curing temperature of the thermosetting rubber composition. The content of the foaming agent is preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, and even more preferably 5 to 12 parts by mass, per 100 parts by mass of the thermosetting rubber composition. The thermosetting rubber composition may also preferably contain a curing catalyst, a crosslinking agent, etc., in addition to the main rubber component.

[0018] The thickness of the thermosetting rubber sheet 3 is not particularly limited, but is preferably 1 mm to 30 mm, more preferably 2 mm to 20 mm. The thermosetting rubber sheet 3 is preferably rectangular in plan view, and its long and short sides preferably fall within the same range as the long and short sides of the expandable sheet 1.

[0019] (3) Exemplary Manufacturing Method of Expandable Sheet The expandable sheet 1 can be produced using, for example, the following materials. 100 parts by mass of a thermosetting silicone rubber composition (curing agent not included, curing temperature: approximately 120°C), which is an example of a thermosetting rubber composition, is mixed with 3 parts by mass of a curing agent (e.g., a platinum-based curing catalyst) and 10 parts by mass of a foaming agent (foaming temperature: approximately 100°C), and the resulting mixture is extruded onto a polyethylene terephthalate (PET) or polyimide (PI) film, which is an example of a resin sheet 2, to produce a two-layer expandable sheet 1. The resin sheet 2 is preferably a sheet with high insulating properties and high heat resistance. A sheet containing aramid fiber or a molded sheet of aramid fiber may also be used as the resin sheet 2.

[0020] When the battery cell is abnormally overheated, the expandable sheet 1 is supplied with heat, and the foaming agent in the thermosetting rubber sheet 3 constituting the sheet 1 first foams, and then the temperature further rises, causing the matrix material of the thermosetting rubber sheet 3 to begin to harden. When the cured thermosetting rubber sheet 3 is exposed to heat, the resin sheet 2 may melt midway and become unable to maintain its shape.

[0021] 2. Battery Next, a battery according to an embodiment will be described.

[0022] FIG. 2 is a perspective view showing a state in which the battery housing is half-opened from the battery box according to one embodiment, and a state in which an expansive sheet is placed inside the battery.

[0023] The battery 5 according to this embodiment is, for example, a battery for an electric vehicle, and includes a plurality of battery cells (also simply referred to as "cells") 8 arranged side by side. The battery 5 has a structure including an expandable sheet 1 and one or more battery cells 8 in a battery box 6. The number of battery cells 8 is 13 in this embodiment, but may be 1 to 12 or 14 or more. The battery 5 is a battery that can be charged and discharged, and is preferably a lithium-ion battery.

[0024] The battery box 6 includes battery cells 8 in its storage space. The battery box 6 includes a detachable housing 7 in which the battery cells 8 can be placed (arrow P: the direction of insertion and removal of the housing 7). The expandable sheet 1 is disposed in the gap between the inner surface of the battery box 6 and the outer surface of the battery cells 8. In FIG. 2, the expandable sheet 1 is inserted into the battery 5 as shown by arrow S. The expandable sheet 1 may be fixed to either the inner surface of the battery box 6 or the outer surface of the battery cells 8. If the battery cells 8 are provided with a drain (e.g., a drain valve) for when the internal pressure rises, the expandable sheet 1 is preferably disposed so as to cover the position of the drain. In this embodiment, a drain (not shown) is provided on the upper surface of the battery cells 8, which is located at the top in FIG. 2. Therefore, the expandable sheet 1 is disposed so as to cover the upper surfaces of the battery cells 8.

[0025] FIG. 3 shows an enlarged view of the interior of the battery of FIG. 2 and a portion A of the interior.

[0026] The expansive sheet 1 is disposed on the top surfaces of a total of 13 battery cells 8. The expansive sheet 1 does not have to be disposed on the top surfaces of all battery cells 8 in the battery 5. However, since it is often unclear which of the battery cells 8 in the battery 5 will overheat, it is preferable that the expansive sheet 1 be disposed on the top surfaces of all battery cells 8 in the battery 5.

[0027] In this embodiment, the expansive sheet 1 is placed on the upper surface of the battery cell 8, but it may also be attached to the upper surface. If the thermosetting rubber sheet 3 of the expansive sheet 1 has adhesiveness, the thermosetting rubber sheet 3 side of the expansive sheet 1 can be detachably attached to the upper surface of the battery cell 8 without using an adhesive.

[0028] On the other hand, the expansive sheet 1 may be attached to the inside surface of the battery box 6, for example, the inner top surface. In this case, the expansive sheet 1 and the inner top surface of the battery box 6 may be bonded with an adhesive. Furthermore, if the thermosetting rubber sheet 3 of the expansive sheet 1 has adhesiveness, the thermosetting rubber sheet 3 side of the expansive sheet 1 can be detachably attached to the inner top surface of the battery box 6 without using an adhesive.

[0029] 3, the battery cells 8 are not yet in an overheated state, and therefore the foaming agent 10 dispersed in the thermosetting rubber sheet 3 of the expandable sheet 1 has not yet foamed.

[0030] FIG. 4 is a view similar to FIG. 3 showing a state when a battery cell in the battery of FIG. 2 becomes overheated.

[0031] When at least some of the battery cells 8 overheat during charging and discharging, the foaming agent 10 in the thermosetting rubber sheet 3 constituting the expansive sheet 1 begins to foam. This causes the thermosetting rubber sheet 3 to expand. After a predetermined time has passed since the start of foaming, the thermosetting rubber sheet 3 begins to harden. As a result, the expansive sheet 1 becomes a laminate 16 of a foamed rubber sheet 3a and a resin sheet 2. The air bubbles 15 in the foamed rubber sheet 3a enhance the insulating properties of the laminate 16. Therefore, the laminate 16 contributes to inhibiting heat transfer between the battery cells 8. If the thermosetting rubber sheet 3 becomes a highly heat-resistant rubber sheet, such as a foamed silicone rubber or a foamed fluororubber sheet, after hardening, the resin sheet 2 may remain even after burning and continue to inhibit heat transfer between the battery cells 8.

[0032] More specifically, if some abnormality causes some battery cells 8 to overheat and the electrolyte inside them erupts at a high temperature, even if the heat of the electrolyte melts the resin sheet 2, the thermosetting rubber sheet 3 absorbs the heat, foams, and then begins to harden. As a result, the expandable sheet 1 expands through foaming, spreading into the gap between the battery cells 8 and the battery box 6 and ideally filling the gap. This prevents the spread of fire between the battery cells 8.

[0033] 3. Modification of Expandable Sheet FIG. 5 shows a perspective view of a variation of the intumescent sheet of FIG.

[0034] The expansive sheet 1a according to the modified example has one thermosetting rubber sheet 3 sandwiched between two resin sheets 2. Other than this configuration, it is the same as the expansive sheet 1 of FIG.

[0035] The expandable sheet 1a is not particularly limited in its shape or size. The expandable sheet 1a may be in any shape, such as a rectangular parallelepiped, a cylinder, or an elliptical cylinder. A preferred shape for the expandable sheet 1a is a rectangular parallelepiped, particularly a sheet-shaped rectangular parallelepiped with one of its three sides being very small. In this case, the long side is preferably 100 mm or more and 1000 mm or less, more preferably 200 mm or more and 800 mm or less. The short side, provided that it is shorter than the long side, is preferably 50 mm or more and 700 mm or less, more preferably 100 mm or more and 500 mm or less. The thickness (shortest side) is not particularly limited, but is preferably 2 mm or more and 50 mm or less, more preferably 4 mm or more and 30 mm or less.

[0036] The expandable sheet 1a can be manufactured using, for example, the following materials. 100 parts by mass of a thermosetting silicone rubber composition (curing agent not included, curing temperature: approximately 120°C), which is an example of a thermosetting rubber composition, is mixed with 3 parts by mass of a curing agent (e.g., a platinum-based curing catalyst) and 10 parts by mass of a foaming agent (foaming temperature: approximately 100°C), and the resulting mixture is molded into a sheet of a certain thickness using a polyethylene terephthalate (PET) or polyimide (PI) sheet as a carrier. Then, a sheet identical to the carrier is prepared, and the thermosetting rubber sheet 3 is sandwiched between two resin sheets 2 to obtain the expandable sheet 1a with a three-layer laminate structure. The resins constituting the two resin sheets 2 may be the same type of resin or different types of resin. The resin sheet 2 is preferably a sheet with high insulation and heat resistance. A sheet containing aramid fiber or a molded sheet of aramid fiber may also be used as the resin sheet 2.

[0037] Similar to the expansive sheet 1, the expansive sheet 1a can be placed inside the battery 5 in FIG. 3. The battery box 6 has battery cells 8 in its storage space. The battery box 6 has a retractable housing 7 in which the battery cells 8 can be placed. The expansive sheet 1a can be placed in the gap between the inner surface of the battery box 6 and the outer surface of the battery cells 8.

[0038] 4. Other embodiments Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be practiced in various modified forms.

[0039] For example, the term "battery" can be interpreted as meaning the entire space (accommodation space + battery cell) that accommodates only one battery cell in an electronic device such as a mobile phone. In this case, the term "battery box" refers to the part that accommodates the battery cell. The expansive sheet 1, 1a can be placed in the gap between the battery cell and the space that accommodates the battery cell in the electronic device. The expansive sheet 1, 1a may also be attached to the inner surface of a lid that closes the battery cell accommodation space.

[0040] In another embodiment, an expandable sheet including the thermosetting rubber sheet 3 but not the resin sheet 2 can be placed in the battery box 6. For example, during manufacturing, a laminated sheet including the thermosetting rubber sheet 3 and the resin sheet 2 as a carrier may be prepared, and when the expandable sheet is to be provided in the battery 5, the carrier may be peeled off and only the thermosetting rubber sheet 3 may be placed in the battery box 6. The thermosetting rubber composition constituting the thermosetting rubber sheet 3 is preferably a sheet-like thermosetting silicone rubber composition.

[0041] The features of the claims may be combined in any combination except where they are incombinable with one another. [Industrial Applicability]

[0042] The present invention can be used as a sheet that can be compressed and deformed in response to the expansion of a heat source. [Explanation of symbols]

[0043] 1, 1a···Expansive sheet, 2···Resin sheet, 3···Thermosetting rubber sheet, 3a···Foam rubber sheet, 5···Battery, 6···Battery box, 7···Housing, 8···Battery cell (also simply called "cell"), 10···Foaming agent, 15···Air bubbles, 16···Laminate.

Claims

1. An expandable sheet disposed in a battery box containing one or more battery cells, A resin sheet; a thermosetting rubber sheet; and The thermosetting rubber sheet is an expandable sheet that is a sheet containing a foaming agent in a thermosetting rubber composition, and is capable of foaming by absorbing heat when the battery cell is overheated.

2. 2. The expandable sheet according to claim 1, wherein one thermosetting rubber sheet is sandwiched between two resin sheets.

3. 2. The expandable sheet according to claim 1, wherein the thermosetting rubber composition is a sheet-shaped thermosetting silicone rubber composition.

4. 2. The expandable sheet according to claim 1, wherein the thickness of the thermosetting rubber sheet is greater than the thickness of the resin sheet.

5. An expandable sheet disposed in a battery box containing one or more battery cells, Equipped with a thermosetting rubber sheet, The thermosetting rubber sheet is an expandable sheet that is a sheet containing a foaming agent in a thermosetting rubber composition, and is capable of foaming by absorbing heat when the battery cell is overheated.

6. 6. The expandable sheet according to claim 5, wherein the thermosetting rubber composition is a sheet-shaped thermosetting silicone rubber composition.

7. A battery having a structure including the expandable sheet according to any one of claims 1 to 6 and one or more battery cells in a battery box, the battery box includes the battery cells in its accommodation space; The battery, wherein the expandable sheet is disposed in a gap between an inner surface of the battery box and an outer surface of the battery cell.

8. 8. The battery of claim 7, wherein the expandable sheet is secured to either the inner surface or the outer surface.

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