Sealing member for a storage battery and a storage battery using the same

Abstract

To provide a seal member for a power storage battery, which is preferably used for a fire spread prevention or the like.SOLUTION: In a seal member for a power storage battery, formed by the vulcanization of a rubber composition, the rubber composition contains a silicon rubber and a vulcanization agent. A hardness Ha (a durometer-type A) measured at a temperature of 23°C and a relative humidity of 50% by overlapping three vulcanization rubber sheets having a thickness of 2 mm constructing the seal member is 90 points or less. It satisfies JIS K6262, and is compressed to 25%. A compression permanent set of the seal member is 80% or less, measured after the holding for 70 hours at 150°C. A difference between the hardness Ha (the durometer-type A) and a hardness Hb (the durometer-type A) measured at the temperature of 23°C and the relative humidity of 50% by overlapping the three vulcanization rubber sheets after the heat for 10 minutes at 400°C is 15 points or less. A mass of a residual material after the heat of the seal member for 5 minutes at 800°C is 70 to 100 mass% against the seal member before the heat, and an evaluation of fire retardancy based on a UL94 (a vertical flame test ) satisfies V-0.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a sealing member for a storage battery used for preventing fire spread and the like, and a storage battery using the same.

Background Art

[0002] Various storage batteries typified by lithium-ion batteries may experience thermal runaway and ignition due to internal short circuits or the like.

[0003] As a means for suppressing the spread of fire from a cell or the like to other cells when ignition occurs, a method of separating cells housed in a container with a fireproof sheet or the like is known (Patent Documents 1 and 2). However, these methods have an insufficient fire spread prevention effect, and once ignition occurs from a cell or the like, the fire often spreads to the entire storage battery. For this reason, there is a demand for a method that can prevent the spread of fire to the entire storage battery and minimize damage even when ignition occurs.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made to solve the above problems, and provides a sealing member for a storage battery that is suitably used for preventing fire spread and the like.

Means for Solving the Problems

[0006] The above problem is solved by providing a sealing member for a storage battery obtained by vulcanizing a rubber composition, wherein the rubber composition contains silicone rubber and a vulcanizing agent, the hardness Ha (durometer type A) of the sealing member at 23°C and a relative humidity of 50% is 90 points or less, in accordance with JIS K6262, after being compressed by 25%, the compression set of the sealing member measured after holding at 150°C for 70 hours is 80% or less, the difference between the hardness Ha (durometer type A) of the sealing member at 23°C and a relative humidity of 50% and the hardness Hb (durometer type A) of the sealing member at 23°C and a relative humidity of 50% after being heated at 400°C for 10 minutes is within 15 points, and the mass of the residue after heating the sealing member at 800°C for 5 minutes is 70 to 100% by mass with respect to the sealing member before heating.

[0007] The above problem is also solved by providing a storage battery using a sealing member, in which a plurality of cells are housed in a container, the cells are separated from each other by a heat insulating plate, and the gap between the container and the heat insulating plate is sealed with the sealing member to prevent the spread of fire.

Advantages of the Invention

[0008] The sealing member of the present invention has high flame retardancy and is difficult to lose its sealing property even when heated at a high temperature. Therefore, by using the sealing member to seal the gap between the container and the heat insulating plate, etc., even when a cell or the like catches fire, the spread of fire to the entire storage battery can be effectively prevented. Therefore, the storage battery using the sealing member has high safety.

Brief Description of the Drawings

[0009]

Figure 1

Embodiments for Carrying Out the Invention

[0010] The sealing member for a storage battery of the present invention is obtained by vulcanizing a rubber composition. The rubber composition contains silicone rubber and a vulcanizing agent. The hardness Ha (durometer type A) of the sealing member at 23°C and a relative humidity of 50% is 90 points or less. In accordance with JIS K6262, after being compressed by 25%, the compression set of the sealing member measured after being held at 150°C for 70 hours is 80% or less. The difference between the hardness Ha (durometer type A) of the sealing member at 23°C and a relative humidity of 50% and the hardness Hb (durometer type A) of the sealing member at 23°C and a relative humidity of 50% after being heated at 400°C for 10 minutes is within 15 points. And the mass of the residue after heating the sealing member at 800°C for 5 minutes is 70 to 100% by mass with respect to the sealing member before heating.

[0011] The sealing member has high flame retardancy and is difficult to lose its sealing property even when heated at a high temperature. Therefore, by using the sealing member to seal the gap between the container and the heat insulating plate, even when a cell or the like catches fire, the spread of fire to the entire storage battery can be effectively prevented.

[0012] The silicone rubber is not particularly limited, but those having high flame retardancy and fire resistance are preferably used. As the silicone rubber, for example, "KE-5620BL-U", "KE-5612E-U", "KE-5620W-U", "KE-1734-U" which are silicone rubbers manufactured by Shin-Etsu Chemical Co., Ltd., "SILASTIC SH502U", "SILASTIC SH1447" which are silicone rubbers manufactured by Dow Corning Toray Co., Ltd., "TCM5406U", "TSE2183UN", "TSE2187U" which are silicone rubbers manufactured by Momentive Performance Materials Japan Co., Ltd. etc. are used.

[0013] The content of the silicone rubber in the rubber composition is usually 50% by mass or more, preferably 60% by mass or more, more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0014] The vulcanizing agent contained in the rubber composition is not particularly limited and may be appropriately selected according to the vulcanization method. Examples of the vulcanizing agent used in the case of peroxide vulcanization include those containing organic peroxides such as benzoyl peroxide, tertiary butyl perbenzoate, ortho methyl benzoyl peroxide, para methyl benzoyl peroxide, di tertiary butyl peroxide, dicumyl peroxide, 1,1-bis(tertiary butyl peroxy)3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(tertiary butyl peroxy)hexane, and 2,5-dimethyl-2,5-di(tertiary butyl peroxy)hexyne. Examples of the vulcanizing agent used in the case of addition vulcanization include a platinum catalyst.

[0015] The content of the vulcanizing agent in the rubber composition is preferably 0.05 to 5% by mass. If the content is less than 0.05% by mass, the hardness of the resulting seal member may become too low. The content is more preferably 0.1% by mass or more. On the other hand, if the content of the vulcanizing agent exceeds 5% by mass, the resulting seal member may become too hard, causing the mating material to deform and the sealing performance to deteriorate. The content is more preferably 2% by mass or less, and even more preferably 1.5% by mass or less.

[0016] From the viewpoint of the processability of the rubber composition, it is preferable that the rubber composition contains an oil. As the oil, silicone oil is preferable. As the silicone oil, modified silicone oil is preferable, and examples of the modified silicone oil include amino-modified, epoxy-modified, carboxyl-modified, carbinol-modified, (meth)acrylic-modified, mercapto-modified, phenol-modified, polyether-modified, methylstyryl-modified, alkyl-modified, higher fatty acid ester-modified, higher alkoxy-modified, fluorine-modified, aralkyl-modified and other modified silicones. And, as these modified silicone oils, there are non-reactive and reactive ones, and among them, non-reactive modified silicone oil is preferable. The content of the oil in the rubber composition is preferably 0.1 to 15% by mass. When the content is less than 0.1% by mass, the processability may be reduced. The content is more preferably 0.3% by mass or more, and even more preferably 0.5% by mass or more. On the other hand, when the content of the oil exceeds 15% by mass, there is a risk of becoming overly soft or bleeding. The content is more preferably 10% by mass or less, and even more preferably 5% by mass or less.

[0017] The rubber composition may contain a flame retardant or the like. Examples of the flame retardant include iron oxide, triazole-based compounds, aluminum hydroxide, platinum, platinum compounds, etc., and among them, platinum compounds are preferable. In addition, for example, when the rubber composition contains the platinum compound, its content is usually 1 to 5000 ppm.

[0018] The rubber composition may contain other additives other than the silicone rubber, the vulcanizing agent, the flame retardant, and the oil as long as the effects of the present invention are not inhibited.

[0019] The manufacturing method of the seal member of the present invention is not particularly limited, but a preferable manufacturing method includes a kneading step of kneading the silicone rubber, the vulcanizing agent, the oil, the flame retardant, and other additives as necessary to obtain the rubber composition, a molding step of molding the rubber composition, and a vulcanizing step of vulcanizing the obtained molded product.

[0020] The method of mixing each component in the kneading step is not particularly limited, and kneading can be performed using an open roll, a kneader, a Banbury mixer, an intermix, an extruder, or the like. Among these, it is preferable to knead using an open roll. The temperature during kneading is preferably 20 to 100°C.

[0021] Examples of the method for molding the rubber composition include injection molding, extrusion molding, compression molding, roll molding, and the like. Among these, injection molding and compression molding are preferable. At this time, it may be vulcanized after being molded in advance, or may be vulcanized simultaneously with molding. The vulcanization temperature is usually 100 to 200°C. The vulcanization time is usually 0.1 to 60 minutes. As the heating method for vulcanization, general methods used for vulcanizing silicone rubber such as compression heating, steam heating, oven heating, and hot air heating are used. Furthermore, secondary vulcanization may be performed. In that case, the vulcanization temperature is usually 150 to 200°C, and the vulcanization time is usually 1 to 4 hours.

[0022] Thus, the seal member of the present invention is obtained. It is necessary that the compression set of the seal member, measured after being compressed by 25% in accordance with JIS K6262 and held at 150°C for 70 hours, is 80% or less. Since the sealing performance of the seal member is enhanced when the compression set is 80% or less, flashover can be effectively prevented. The compression set is preferably 65% or less, more preferably 50% or less, still more preferably 40% or less, and particularly preferably 30% or less. On the other hand, the compression set is usually 1% or more.

[0023] The hardness Ha (durometer type A) of the sealing member at 23°C and a relative humidity of 50% needs to be 90 points or less. When the hardness Ha (durometer type A) is 90 points or less, the surface pressure is maintained against the mating surface, and the sealing performance of the sealing member is enhanced, so that the spread of fire can be effectively prevented. The hardness Ha (durometer type A) is preferably 85 points or less, and more preferably 80 points or less. On the other hand, from the viewpoint of further improving the sealing performance, the hardness Ha (durometer type A) is preferably 30 points or more, more preferably 35 points or more, and still more preferably 40 points or more. The hardness Ha (durometer type A) of the sealing member is measured by the method described in the examples.

[0024] In the present invention, the difference between the hardness Ha (durometer type A) of the sealing member at 23°C and a relative humidity of 50% and the hardness Hb (durometer type A) of the sealing member at 23°C and a relative humidity of 50% after being heated at 400°C for 10 minutes needs to be within 15 points. When the difference is within 15 points, when ignition occurs, it becomes difficult for the sealing performance of the sealing member to deteriorate, so that the spread of fire can be effectively prevented. On the other hand, although the difference may be ±0, it is usually 1 point or more. As long as the difference is within 15 points, either the hardness Ha (durometer type A) of the sealing member before heating or the hardness Hb (durometer type A) of the sealing member after heating may be higher.

[0025] The mass of the residue after heating the sealing member at 800°C for 5 minutes needs to be 70 to 100% by mass with respect to the sealing member before heating. Thereby, when ignition occurs, even after the sealing member is heated and the sealing performance deteriorates, the shape is maintained, so that a certain fire spread prevention effect is exhibited. The mass of the residue is preferably 75% by mass or more, and more preferably 78% by mass or more. The mass of the residue is determined by the method described in the examples.

[0026] The sealing member of the present invention has an excellent effect of preventing flame spread because it is difficult to lose its sealing property even when heated and retains its shape even after the sealing property is lost. Therefore, the sealing member is preferably used as a sealing member for various storage batteries (secondary batteries) such as lithium-ion batteries, lithium-ion polymer batteries, nickel-hydrogen batteries, lithium-sulfur batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, sodium-sulfur batteries, lead-acid batteries, and air batteries. Among them, more preferably, the sealing member of the present invention is used as a sealing member for a lithium-ion battery, which has a high energy density and may cause great damage if it catches fire.

[0027] A storage battery 2 using the sealing member 1, in which a plurality of cells 3 are housed in a container 4, the cells 3 are separated from each other by a heat insulating plate 5, and the gap between the container 4 and the heat insulating plate 5 is sealed with the sealing member 1 to prevent flame spread, is a preferred embodiment of the present invention. FIG. 1 is an example of a schematic cross-sectional view of the storage battery 2 of the present invention. Hereinafter, the storage battery 2 of the present invention will be described with reference to FIG. 1.

[0028] The type of the storage battery 2 using the sealing member 1 is not particularly limited, and examples thereof include those described above as storage batteries using the sealing member of the present invention. The shape of the cell 3 is not particularly limited, and examples thereof include a cylindrical shape, a rectangular shape, and a laminated shape. The cell 3 usually includes a positive electrode material, a negative electrode material, a separator, a positive electrode terminal, a negative electrode terminal, etc. housed in an exterior member.

[0029] A plurality of cells 3 are accommodated in a container 4. The shape of the container 4 is not particularly limited, and examples include a rectangular shape and a cylindrical shape. The cells 3 accommodated in the container 4 are separated from each other by a heat insulating plate 5. In FIG. 1, the plurality of cells 3 accommodated in the container 4 are divided into two by using one heat insulating plate 5, but by using two or more heat insulating plates 5, the plurality of cells 3 accommodated in the container 4 may be divided into three or more. The type of the container 4 is not particularly limited, and a metal container, a resin container, etc. are used. The type of the heat insulating plate 5 is also not particularly limited as long as it has high heat insulating properties and flame retardancy, and a metal heat insulating plate 5, a heat insulating plate 5 made of resin, etc. are used. The heat insulating plate 5 may be a laminate of a plurality of types of plates.

[0030] And a seal member 1 is disposed between the container 4 and the heat insulating plate 5. By sealing the gap between the container 4 and the heat insulating plate 5 with the seal member 1, even when ignition occurs from the cell 3 or the like, the spread of fire to other cells 3 or the like separated by the heat insulating plate 5 is prevented or delayed. The seal member 1 may be disposed at least in part of the gap between the container 4 and the heat insulating plate 5. The seal member 1 may be disposed at a place necessary for preventing the spread of fire in consideration of the design of the storage battery 2 or the like. It is preferable that the seal member 1 is disposed in the gap between the container 4 and the heat insulating plate 5 so that gas does not leak from one space separated by the heat insulating plate 5 to the other space. For example, a method of installing the seal member 1 around the entire circumference of the heat insulating plate 5 and bringing the seal member 1 into contact with the container 4 can be mentioned. In addition, as long as the spread of fire to other cells 3 or the like is prevented or delayed, the seal member 1 may be installed at a part around the heat insulating plate 5. The shape of the seal member 1 is not particularly limited, and it may be determined in consideration of the shape of the heat insulating plate 5 and the container 4, the shape of the gap between the heat insulating plate 5 and the container 4, and the like. The seal member 1 may, for example, have a pair of lip portions that are pressure-bonded to the inner wall of the container 4 in an elastically deformed state. The storage battery 2 of the present invention using a predetermined seal member 1 has high safety because the spread of fire to other cells 3 or the like separated by the heat insulating plate 5 is prevented or delayed even when ignition occurs from the cell 3 or the like.

Example

[0031] Hereinafter, the present invention will be described in more detail with reference to examples.

[0032] (Normal physical properties) Three vulcanized rubber sheets with a thickness of 2 mm were stacked, and using a Type A durometer, measurements were taken at 23 °C and a relative humidity of 50%, and the peak value was taken as the hardness (durometer type A) of the vulcanized rubber sheet.

[0033] (Compression set test) Based on JIS K6262 compliance (150 °C, 70 hours), a cylindrical test piece was compressed by 25%, held in air at 150 °C for 70 hours, the compression was then released, and the compression set was calculated. The smaller the value, the higher the restoring force when compressed for a long time.

[0034] (Combustion test) The flame retardancy was evaluated based on UL94 (vertical combustion test). Based on a 20 mm vertical combustion test (IEC60695-11-10 Method B, ASTM D3801), a strip sample with a length of 125 ± 5 mm, a width of 13.0 ± 0.5 mm, and a thickness of 1 mm was vertically attached to a clamp, and indirect flame application with a 20 mm flame was performed twice for 10 seconds each, and the flame retardancy was evaluated based on the combustion behavior. The strip sample was obtained by cutting out a vulcanized rubber sheet.

[0035] (High temperature test) The electric furnace was set to 400 °C. After the temperature rose, a square sample with a side length of 30 mm and a thickness of 2 mm, obtained by cutting out a vulcanized rubber sheet, was placed in a crucible and inserted into the electric furnace, and taken out after 10 minutes. Then, three vulcanized rubber sheets were stacked, and using a Type A durometer, measurements were taken at 23 °C and a relative humidity of 50%, and the peak value was taken as the hardness (durometer type A) of the vulcanized rubber sheet after heating.

[0036] The electric furnace was set to 800 °C. After the temperature rose, the mass of a square sample with a side length of 20 mm and a thickness of 2 mm, obtained by cutting out a vulcanized rubber sheet, was measured, then placed in a crucible and inserted into the electric furnace, and taken out after 5 minutes. The mass of the sample (residue) was measured.

[0037] Examples 1 to 3, 5 to 7, Comparative Examples 1 to 4 A mixture having the composition shown in Table 1 was kneaded at a temperature of 20 to 100°C for 10 to 30 minutes using an open roll to obtain a rubber composition. Then, an unvulcanized rubber sheet was prepared using this rubber composition. Using the obtained unvulcanized rubber sheet, press vulcanization was carried out at 165°C for 10 minutes, and then secondary vulcanization was carried out at 200°C for 4 hours to obtain a vulcanized rubber sheet having a thickness of 2 mm or 1 mm (hereinafter, may be simply referred to as a vulcanized rubber sheet). Further, the stacked unvulcanized rubber sheets were put into a mold for press molding, press vulcanized at 165°C for 30 minutes, and then secondary vulcanization was carried out at 200°C for 4 hours to obtain a cylindrical test piece for measuring compression set having a diameter of 29.0 mm and a thickness of 12.5 mm. Each measurement was carried out using the vulcanized rubber sheet and the test piece for measuring compression set. The results are shown in Table 1.

[0038] [Table 1] [Explanation of Reference Signs]

[0039] 1 Seal member 2 Storage battery 3 Cell 4 Container 5 Heat insulating plate

Claims

1. A sealing member for a storage battery obtained by vulcanizing a rubber composition, wherein the rubber composition contains silicone rubber and a vulcanizing agent, three vulcanized rubber sheets having a thickness of 2 mm constituting the sealing member are stacked, and the hardness Ha (durometer type A) measured at 23°C and a relative humidity of 50% is 90 points or less, in accordance with JIS K6262, after being compressed by 25%, the compression set of the sealing member measured after being held at 150°C for 70 hours is 80% or less, the difference between the hardness Ha (durometer type A) and the hardness Hb (durometer type A) measured at 23°C and a relative humidity of 50% of three stacked vulcanized rubber sheets after being heated at 400°C for 10 minutes is within 15 points, the mass of the residue after heating the sealing member at 800°C for 5 minutes is 70 to 100% by mass with respect to the sealing member before heating, and a sealing member satisfying V-0 in the flame retardancy evaluation based on UL94 (vertical burning test).

2. The sealing member according to claim 1, wherein the rubber composition contains 0.1 to 15% by mass of a non-reactive modified silicone oil.

3. In a storage battery in which a plurality of cells are housed in a container and the cells are separated by a heat insulating plate, the sealing member is for sealing the gap between the container and the heat insulating plate, and when the sealing member is disposed in the gap between the container and the heat insulating plate, it has a lip portion that is pressure-bonded to the inner wall of the container in an elastically deformed state. The sealing member according to claim 1 or 2.

4. A storage battery using the sealing member according to claim 1 or 2, wherein a plurality of cells are housed in a container, the cells are separated by a heat insulating plate, and the gap between the container and the heat insulating plate is sealed with the sealing member to prevent the spread of fire. A storage battery.

5. A storage battery using the sealing member according to claim 3, wherein a plurality of cells are housed in a container, the cells are separated by a heat insulating plate, the sealing member is disposed in the gap between the container and the heat insulating plate, and the lip portion of the sealing member is pressure-bonded to the inner wall of the container in an elastically deformed state, whereby the gap between the container and the heat insulating plate is sealed with the sealing member to prevent the spread of fire. A storage battery.

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