JP7637551B2 - Fire prevention sheet, cell unit and battery - Google Patents

Description

The present invention relates to a fire prevention sheet, a battery cell unit in which the sheet is attached to a battery cell, and a battery equipped with the cell unit.

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 more popular in Europe, particularly in France, the Netherlands, Germany, and other European countries, as well as in China. However, the widespread use of electric vehicles faces challenges such as the development of high-performance batteries and the installation of a large number of charging stations.

Various batteries such as the above-mentioned automobile batteries may experience thermal runaway due to an internal short circuit or the like, which may result in fire or smoke. In recent years, automobile batteries in which multiple battery cells are arranged and mounted inside a housing have become known. In such batteries in which multiple battery cells are arranged and mounted, if one battery cell ignites or emits smoke, the heat may be transferred to the surrounding battery cells, which may cause further malfunctions such as fire, smoke, or explosion. In order to minimize damage caused by such malfunctions, methods have been considered that make it difficult for heat from abnormally hot battery cells to be transferred to the surrounding battery cells. For example, a method is known in which a fire-prevention sheet such as a fire-resistant material or a heat-insulating layer is provided between multiple battery cells (see Patent Document 1).

JP 2018-206604 A

Having excellent fire prevention function is the highest priority for a fire prevention sheet. However, in addition to this, it is also important that the fire prevention sheet be placed in the correct position within the battery and that it be easy to insert and remove the sheet from the battery. In this way, making it easy to securely install and insert and remove the fire prevention sheet and minimizing battery troubles will also contribute to achieving the applicant's sustainable development goal of "ensuring access to affordable, reliable, sustainable and modern energy for all".

The present invention was made in consideration of the above problems, and aims to provide a fire prevention sheet that can prevent the spread of fire between battery cells in a battery and that makes it easy to insert and remove battery cells into and from the battery, a cell unit in which the fire prevention sheet is attached to a battery cell, and a battery including the cell unit.

(1) In one embodiment of the fire prevention sheet for achieving the above-mentioned object, the fire prevention sheet is arranged between multiple battery cells inside a battery, and is capable of preventing the spread of fire by suppressing heat transfer to other battery cells when one of the battery cells is in an overheated state, and has at least one air flow path from the lower end to the upper end when arranged on the battery.
(2) The fire spread prevention sheet according to another embodiment may preferably be mainly composed of a porous body.
(3) In another embodiment, the fire spread prevention sheet may preferably further include, in the porous body layer, a heat-resistant reinforced sheet having higher heat resistance than the porous body layer.
(4) In the fire spread prevention sheet according to another embodiment, the flow path may be preferably formed on the outer surface of the heat-resistant reinforced sheet.
(5) In the fire spread prevention sheet according to another embodiment, the flow path may preferably be formed between the porous body layer and the heat-resistant reinforced sheet.
(6) In the fire spread prevention sheet according to another embodiment, preferably, the heat-resistant reinforced sheet may mainly contain talc.
(7) In the fire spread prevention sheet according to another embodiment, the porous layer may preferably be a foamed sheet of silicone rubber.
(8) A cell unit according to one embodiment is a cell unit of a fire prevention sheet and a battery cell, in which any of the above-mentioned fire prevention sheets is attached to at least one of the two sides in the direction in which the battery cells are arranged.
(9) In a cell unit according to another embodiment, the adhesion of the surface of the fire spread prevention sheet attached to the battery cell may preferably be lower than the adhesion of the outer surface opposite the attachment surface in the thickness direction of the fire spread prevention sheet.
(10) In the cell unit according to another embodiment, preferably, the arithmetic mean height (Sa) of the outer surface may be greater than that of the attachment surface.
(11) A battery according to one embodiment includes a plurality of cell units according to any one of the above-described cell units arranged in a row.

The present invention provides a fire prevention sheet that can prevent the spread of fire between battery cells in a battery and that makes it easy to insert and remove battery cells into and from the battery, a cell unit in which the fire prevention sheet is attached to a battery cell, and a battery equipped with the cell unit.

FIG. 1 shows a perspective view (1A) and a plan view (1B) for explaining the configuration of a fire spread prevention sheet and a cell unit according to the first embodiment. FIG. 2 shows a state (2A, 2B) in which a plurality of the cell units of FIG. 1 are loaded into a battery housing. FIG. 3 shows a perspective view (3A) and a plan view (3B) for explaining the configuration of the fire spread prevention sheet and the cell unit according to the second embodiment. FIG. 4 shows a plan view and a side view of a fire spread prevention sheet according to the third embodiment. FIG. 5 shows a perspective view (5A) and a plan view (5B) for explaining the configuration of the fire spread prevention sheet and the cell unit according to the fourth embodiment. FIG. 6 shows a perspective view (6A) and a plan view (6B) for explaining the configuration of the fire spread prevention sheet and the cell unit according to the fifth embodiment. FIG. 7 shows vertical cross-sectional views (7A, 7B) of two types of batteries according to an embodiment of the present invention, each having a different internal cell unit configuration.

Next, each embodiment of the present invention will be described with reference to the drawings. Note that each embodiment described below does not limit the invention according to the claims, and not all of the elements and combinations thereof described in each embodiment are necessarily essential to the solution of the present invention.

1. Fire prevention sheet and cell unit (first embodiment)
First, a fire spread prevention sheet and a cell unit according to a first embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows an oblique view (1A) and a plan view (1B) to explain the configuration of the fire spread prevention sheet and cell unit according to the first embodiment.

The fire spread prevention sheet 1 according to the first embodiment is a sheet that is disposed between multiple battery cells 30 inside a battery, and is capable of preventing the spread of fire by suppressing heat transfer to other battery cells 30 when a battery cell 30 is in an overheated state. When disposed on the battery, the fire spread prevention sheet 1 has two air flow paths 10 from the lower end to the upper end. However, it is sufficient that there is at least one flow path 10, and there may be three or more.

The fire prevention sheet 1 is used by attaching its widest surface to the battery cell 30. A single structure in which the fire prevention sheet 1 is attached to the battery cell 30 is called a cell unit 35. More specifically, the cell unit 35 is an integrated unit of the fire prevention sheet 1 and the battery cell 30, with the fire prevention sheet 1 attached to at least one of the two sides in the direction in which the battery cells 30 are arranged. In this embodiment, the fire prevention sheet 1 is in close contact with the battery cell 30, and can be attached without the need for an adhesive or other layer.

In the cell unit 35, the adhesion of the outer surface 12 on the opposite side of the adhesion surface 11 of the fire spread prevention sheet 1 in the thickness direction to the battery cell 30 is preferably lower than the adhesion of the adhesion surface 11 of the fire spread prevention sheet 1 to the battery cell 30. As a result, each cell unit 35 can be easily loaded into or removed from the battery.

In this embodiment, the attachment surface 11 where the fire spread prevention sheet 1 is attached to the battery cell 30 is a surface with high smoothness, and is a surface that can be adhered closely to the widest surface (side surface) of the battery cell 30 with almost no air intervening between it and the widest surface (side surface) of the battery cell 30. The preferred surface roughness of the attachment surface 11 of the fire spread prevention sheet 1 is an arithmetic mean height (Sa) based on "ISO 25178 Surface Quality" in the range of 0.05 to 0.4 μm, more preferably 0.05 to 0.3 μm.

The means for making the outer surface 12 less adhesive than the attachment surface 11 is not limited to providing a difference in surface roughness as described above, and other means may be used. For example, the fire spread prevention sheet 1 may be made up of two layers of sheets, with the sheet on the outer surface 12 side being harder than the sheet on the attachment surface 11 side.

In this embodiment, the flow path 10 is formed on the outer surface 12 on the thickness direction opposite to the attachment surface 11 where the fire spread prevention sheet 1 is attached to the battery cell 30. In this embodiment, the flow path 10 is a groove that is recessed in the thickness direction of the fire spread prevention sheet 1 and opens to the outer surface 12 of the fire spread prevention sheet 1. In this embodiment, the flow path 10 is formed so as to extend from the lower end to the upper end of the fire spread prevention sheet 1 in the length direction (also called the "height direction") of the fire spread prevention sheet 1. The flow path 10 is preferably a straight groove, but may be a curved groove with a bend.

As described below, the flow path 10 has the function of discharging air from inside the battery housing to the outside when the cell unit 35 is inserted into the battery, making it easier to insert the cell unit 35 into the housing (see FIG. 1 (1A)).

In this embodiment, the fire spread prevention sheet 1 is approximately the same size as the widest surface (side surface) of the battery cell 30, but it may be larger or smaller than that side surface. However, to improve fire spread prevention, it is preferable that the fire spread prevention sheet 1 be the same size as or larger than the side surface of the battery cell 30.

In the cell unit 35, the arithmetic mean height (Sa) of the outer surface 12 on the opposite side of the attachment surface 11 to the battery cell 30 of the fire spread prevention sheet 1 is preferably greater than that of the attachment surface 11. When the outer surface 12 is roughened relative to the attachment surface 11, the inside of the groove that becomes the flow path 10 is preferably excluded. This is because the inside of the groove does not come into contact with the adjacent cell unit 35. When a value other than Sa is used as the standard, it is preferable to make the maximum height (Sz) of the outer surface 12 based on "ISO 25178 surface quality" greater than that of the attachment surface 11. The preferred surface roughness of the outer surface 12 of the fire spread prevention sheet 1 is an arithmetic mean height (Sa) based on "ISO 25178 surface quality" in the range of 0.5 to 500 μm, more preferably 0.6 to 500 μm. For example, when the fire spread prevention sheet 1 is manufactured by molding, the roughness of the attachment surface 11 and the outer surface 12 can be easily obtained by transferring the roughness of the inner surface of the mold or the resin sheet placed in the mold. In addition, if the surface roughness of the outer surface 12 is to be increased, a blasting process in which fine particles are collided may be performed. In this way, when the surface roughness of the outer surface 12 is increased compared to the attachment surface 11, it becomes easier to load or pull out one cell unit 35 from among the multiple cell units 35 into or from the battery housing. This is because the cell unit 35 is unlikely to adhere to the adjacent cell unit 35 when loading or pulling out the cell unit 35. In particular, the multiple cell units 35 in the battery are often compressed from the outside in the column direction of the cell units 35 after being loaded into the battery. Even in such a case, if the surface roughness of the outer surface 12 is large, the situation in which the cell units 35 adhere to each other can be reduced. Furthermore, making the attachment surface 11 smooth increases the adhesion between the fire spread prevention sheet 1 and the side of the battery cell 30, making it easier to load or unload each cell unit 35 into or from the battery.

In this embodiment, the fire spread prevention sheet 1 is mainly composed of a porous body, preferably a layer of a porous body, and more preferably a porous rubber sheet. Here, "mainly" means that it occupies more than 50% of the volume. Hereinafter, the meaning of "mainly" is the same. The fire spread prevention sheet 1 may be a sheet consisting of only a porous body, 90% of the porous body, or 80 to 51% of the porous body. The porous rubber sheet is a sponge-like member having air bubbles inside. The air in the holes of the sponge has excellent heat insulation properties. Therefore, the sponge-like member contributes to the low thermal conductivity of the fire spread prevention sheet 1. Examples of rubber include thermosetting elastomers such as silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, nitrile rubber (NBR), or styrene butadiene rubber (SBR); thermoplastic elastomers such as urethane-based, ester-based, styrene-based, olefin-based, butadiene-based, and fluorine-based elastomers, or composites thereof. Of the rubbers, silicone rubber, which has relatively high heat resistance, is more preferably used. In other words, the fire spread prevention sheet 1 is most preferably a silicone rubber foam sheet. In order to further enhance the fire spread prevention performance, the fire spread prevention sheet 1 preferably contains an inorganic compound such as a halide, a phosphorus compound, platinum, magnesium hydroxide, or aluminum hydroxide. There are no particular restrictions on the thickness of the fire spread prevention sheet 1, but it is preferably 1 to 20 mm, more preferably 2 to 8 mm.

Figure 2 shows the situation (2A, 2B) in which multiple cell units of Figure 1 are loaded into a battery housing.

2 is, for example, a battery for an electric vehicle, and includes a number of battery cells 30. The battery 40 includes a bottomed housing 41 that opens on one side. The battery cells 30 are arranged inside 44 of the housing 41. The battery cells 30 are preferably pressed against each other in the housing 41 by applying a force in a compressive direction from both sides of the housing 41 using a screw or the like (not shown). The bottom 42 (an example of a cooling portion) of the housing 41 is provided with one or more water-cooled pipes 43 for flowing cooling water, which is an example of a coolant 45. The coolant 45 may be referred to as a cooling medium or a coolant. The battery cells 30 are arranged in the housing 41 with a fire prevention sheet 1 sandwiched between adjacent battery cells 30. The fire prevention sheet 1 is attached to the battery cells 30 to form one cell unit 35. As shown in FIG. 2 (2A), when loading cell units 35 one by one into the interior 44 of the housing 41, air can be discharged to the outside through the flow path 10, especially when loading the last one in the direction of arrow D. This makes it easy to load the cell units 35. As shown in FIG. 2 (2B), even when loading multiple cell units 35 at once toward the interior 44 of the housing 41 in the direction of arrow D, air in the interior 44 can be discharged to the outside through the flow path 10. This makes it easy to load the cell units 35 into the battery 40.

Second Embodiment
Next, a fire spread prevention sheet and a cell unit according to a second embodiment of the present invention will be described with reference to the drawings. In the second embodiment, the same description as in the first embodiment will be omitted.

Figure 3 shows an oblique view (3A) and a plan view (3B) to explain the configuration of the fire prevention sheet and cell unit according to the second embodiment.

The fire spread prevention sheet 1a according to the second embodiment is a two-layered sheet that includes a porous body layer and a heat-resistant reinforced sheet that has higher heat resistance than the porous body layer. In the fire spread prevention sheet 1a, the air flow path is formed on the outer surface of the heat-resistant reinforced sheet. This will be described in more detail below.

The fire spread prevention sheet 1a is different from the fire spread prevention sheet 1 according to the first embodiment in that it has a heat-resistant reinforced sheet 2 on the outer surface 12 of the rubber sheet 3 used as the fire spread prevention sheet 1. The rubber sheet 3 and the heat-resistant reinforced sheet 2 may be fixed together with a layer of heat-resistant adhesive, or may be fixed together by the adhesiveness of the rubber sheet 3, or may be fixed together by fitting.

The rubber sheet 3 has a groove 10a corresponding to the flow path 10 in the first embodiment, but does not have the function of discharging air as the fire spread prevention sheet 1a. The heat-resistant reinforced sheet 2 overlaps the opening side of the groove 10a and has a flow path 20 that opens to the outer surface 22 side. Similar to the flow path 10 in the first embodiment, there are two flow paths 20 from the lower end to the upper end when the fire spread prevention sheet 1a is placed on the battery 40. However, there must be at least one flow path 20, and there may be three or more. Also, the flow paths 20 do not have to be linear grooves.

In the cell unit 35a, the adhesion of the outer surface 22 on the opposite side of the adhesion surface 11 of the fire spread prevention sheet 1a in the thickness direction to the battery cell 30 is preferably lower than the adhesion of the adhesion surface 11 of the fire spread prevention sheet 1a. As a result, each cell unit 35a can be easily loaded into or removed from the battery 40.

The attachment surface 11 of the fire spread prevention sheet 1a is the surface of the rubber sheet 3 that does not have the grooves 10a, and is a surface with a high level of smoothness similar to that of the attachment surface 11 in the first embodiment. On the other hand, the outer surface 22 of the fire spread prevention sheet 1a is a rougher surface than the attachment surface 11, and is a surface that is as rough or rougher than the outer surface 12 in the first embodiment. The surface roughness of the outer surface 22 can be easily obtained by transferring the roughness of the inner surface of a mold, but if it is desired to increase the surface roughness of the outer surface 22, a blasting process in which fine particles are collided may be performed. Note that when the outer surface 22 is made rougher than the attachment surface 11, preferably the inside of the groove that becomes the flow path 20 is excluded. The reason for this is the same as that explained in the first embodiment.

The preferred surface roughness of the outer surface 22 of the fire spread prevention sheet 1a is an arithmetic mean height (Sa) based on "ISO 25178 Surface Quality" in the range of 0.5 to 500 μm, more preferably 0.6 to 500 μm.

The heat-resistant reinforced sheet 2 has a function of effectively preventing the spread of fire between the battery cells 30. The heat-resistant reinforced sheet 2 may be made of any material, but is preferably a ceramic sheet, and more preferably a sheet containing talc as the main component. Here, "main component" means a ratio of more than 50 volume % of the total volume of the heat-resistant reinforced sheet. The heat-resistant reinforced sheet 2 may be a sheet containing only talc, 90 volume % talc, or 80 to 51 volume % talc. In addition to talc, the heat-resistant reinforced sheet 2 may contain a paper material such as cellulose, an inorganic material such as silica or aerogel, or a resin such as polyethylene or polypropylene. The materials and functions of the heat-resistant reinforced sheet described above are the same in the following embodiments.

Talc is generally a ceramic whose main component is magnesium silicate hydrate, and contains small amounts of impurities such as iron oxide. The type and amount of impurities vary depending on the origin of the talc ore, but the talc contained in the heat-resistant reinforced sheet 2 is not particularly limited in these respects. The average particle size of the talc measured by the laser light diffraction method is preferably 0.1 to 50 μm, more preferably 1 to 30 μm. Talc may be surface-treated with a known surface treatment agent such as an organic silane compound, an organic borane compound, an epoxy compound, an organic titanate compound, or an isocyanate compound. The heat-resistant reinforced sheet 2 may contain only one type of talc as described above, or may contain two or more types with different average particle sizes, types, surface treatment agents, etc.

The heat-resistant reinforced sheet 2 is preferably a sheet having excellent heat resistance and flame retardancy. The heat-resistant reinforced sheet 2 is not limited to a sheet containing talc as a main component as described above, and may be made of a material having at least higher heat resistance and flame retardancy than the rubber sheet 3. Examples of such materials include materials having a relatively low thermal conductivity compared to aluminum nitride, alumina, or graphite, such as mullite, cordierite, steatite, forsterite, titania, and zirconia. The heat-resistant reinforced sheet 2 may or may not have excellent electrical conductivity. The heat-resistant reinforced sheet 2 is preferably a sheet having excellent curvature (or bending), and although there is no restriction on its thickness, it is preferably 0.02 to 3 mm, and more preferably 0.1 to 0.5 mm. The thickness of the heat-resistant reinforced sheet 2 is preferably smaller than that of the rubber sheet 3. However, it is preferable that the thickness of the heat-resistant reinforced sheet 2 is determined by comprehensively considering the strength, flexibility, and heat resistance of the sheet.

The cell unit 35a is formed by attaching the attachment surface 11 of the fire spread prevention sheet 1a to the side surface (here, the widest surface) of the battery cell 30. The outer surface 22 of the fire spread prevention sheet 1a is also the outer surface of the heat-resistant reinforced sheet 2, and is formed relatively rough as described above. In addition, the attachment surface 11 of the fire spread prevention sheet 1a is one side in the thickness direction of the rubber sheet 3, and is very smooth as described above. This reduces the adhesion of the cell unit 35a to adjacent cell units 35a, making it easy to load and pull out the cell unit 35a from the interior 44 of the housing 41.

In this embodiment, the surface roughness of the heat-resistant reinforced sheet 2 is greater than that of the rubber sheet 3, but this is not essential. This is because the heat-resistant reinforced sheet 2 is a ceramic layer that is less adhesive than the rubber sheet 3. This also applies to the following embodiments.

Third Embodiment
Next, a fire spread prevention sheet and a cell unit according to a third embodiment of the present invention will be described with reference to the drawings. In the third embodiment, the same description as in the previous embodiments will be omitted.

Figure 4 shows a plan view and a side view of a fire prevention sheet according to the third embodiment.

The fire spread prevention sheet 1a according to the third embodiment has the same configuration as the fire spread prevention sheet 1a according to the second embodiment. The cell unit 35b according to the third embodiment is provided with fire spread prevention sheets 1a on both sides, the widest in the thickness direction (also called the width direction) of the battery cell 30. That is, the cell unit 35b has a structure in which the battery cell 30 is sandwiched between two fire spread prevention sheets 1a. Thus, unlike the cell units 35 and 35a described above, the cell unit 35b is provided with fire spread prevention sheets 1a on both sides in the width direction of the battery cell 30. The cell unit 35b with such a structure also makes it easy to load and unload the cell unit 35b into the battery 40.

(Fourth embodiment)
Next, a fire spread prevention sheet and a cell unit according to a fourth embodiment of the present invention will be described with reference to the drawings. In the fourth embodiment, the same description as in the previous embodiments will be omitted.

Figure 5 shows an oblique view (5A) and a plan view (5B) to explain the configuration of the fire spread prevention sheet and cell unit according to the fourth embodiment.

The fire spread prevention sheet 1b according to the fourth embodiment is a two-layered sheet having a porous layer and a ceramic layer. In the fire spread prevention sheet 1b, the air flow path is formed on the outer surface of the rubber sheet. This will be explained in more detail below.

Similar to the fire spread prevention sheet 1a according to the second embodiment, the fire spread prevention sheet 1b has a heat-resistant reinforced sheet 2a on the outer surface 12 of the rubber sheet 3 used as the fire spread prevention sheet 1. However, the heat-resistant reinforced sheet 2a is a flat sheet that does not have a flow path. The rubber sheet 3 and the heat-resistant reinforced sheet 2a may be fixed together with a layer of heat-resistant adhesive, or may be fixed together by the adhesiveness of the rubber sheet 3, or may be fixed together by fitting.

The flow path 10 formed on the outer surface 12 of the rubber sheet 3 is similar to the flow path 10 of the fire spread prevention sheet 1 according to the first embodiment. When the flat heat-resistant reinforced sheet 2a is attached to the outer surface 12 of the rubber sheet 3, the flow path 10 is formed inside the fire spread prevention sheet 1b. That is, the flow path 10 is formed between the rubber sheet 3 as a layer of a porous body and the heat-resistant reinforced sheet 2a. The flow path 10 formed in such a position also contributes to facilitating loading of the cell unit 35c into the battery 40. The attachment surface 11 of the fire spread prevention sheet 1b is the surface on the side of the rubber sheet 3 that does not have the flow path 10, and is a surface with a high level of smoothness similar to the attachment surface 11 in the first embodiment. On the other hand, the outer surface 22 of the fire spread prevention sheet 1b is a surface rougher than the attachment surface 11, and is a surface that is equal to or rougher than the outer surface 12 in the first embodiment. The surface roughness of the outer surface 22 can be easily obtained by transferring the roughness of the inner surface of the mold, but if you want to increase the surface roughness of the outer surface 22, you can use a blasting process in which fine particles are collided with the surface.

The preferred surface roughness of the outer surface 22 of the fire spread prevention sheet 1b is as described in the second embodiment. The heat-resistant reinforced sheet 2a has the function of effectively preventing the spread of fire between the battery cells 30. The heat-resistant reinforced sheet 2a may be made of any material, but is preferably a sheet containing talc as its main component. The heat-resistant reinforced sheet 2a is the same as the heat-resistant reinforced sheet 2 in the second embodiment, except that it has a flat plate shape. For this reason, details of the heat-resistant reinforced sheet 2a will be omitted.

Fifth Embodiment
Next, a fire spread prevention sheet and a cell unit according to a fifth embodiment of the present invention will be described with reference to the drawings. In the fifth embodiment, the same description as in the previous embodiments will be omitted.

Figure 6 shows an oblique view (6A) and a plan view (6B) to explain the configuration of the fire prevention sheet and cell unit according to the fifth embodiment.

The fire spread prevention sheet 1c according to the fifth embodiment is a two-layered sheet that further includes a heat-resistant reinforced sheet in addition to the porous body layer. In the fire spread prevention sheet 1c, the air flow path is formed on the outer surface of the ceramic layer. This will be described in more detail below.

The fire spread prevention sheet 1c is provided with a heat-resistant reinforced sheet 2b on the outer surface 12 of a flat rubber sheet 3a, which is an example of a porous layer. The heat-resistant reinforced sheet 2b is a sheet having an air flow path 20. However, the heat-resistant reinforced sheet 2b is a sheet that does not protrude to the back side of the flow path 20. Therefore, the rubber sheet 3a and the heat-resistant reinforced sheet 2b are attached to each other on their flat surfaces, regardless of whether or not an adhesive layer is interposed. The attachment surface 11 of the rubber sheet 3a is a smooth surface similar to the attachment surface 11 of the rubber sheet 3 in the second embodiment. The outer surface 22 of the heat-resistant reinforced sheet 2b has a surface roughness similar to that of the outer surface 22 of the heat-resistant reinforced sheet 2 in the second embodiment.

The cell unit 35d according to the fifth embodiment is provided with a fire prevention sheet 1c on the widest side in the width direction of the battery cell 30. Even with a cell unit 35d having such a structure, it is easy to load and unload the cell unit 35d into the battery 40.

2. Battery Next, a battery according to an embodiment of the present invention will be described with reference to the drawings. In the description of the battery, the fire prevention sheet and the cell unit are the same as those in the above-mentioned embodiments of the fire prevention sheet and the cell unit. Therefore, the repeated description of the fire prevention sheet and the cell unit will be omitted.

Figure 7 shows vertical cross-sectional views (7A, 7B) of two types of batteries according to an embodiment of the present invention, each with a different internal cell unit configuration.

Here, "longitudinal cross-sectional view" refers to a cross-section of the battery cut in the length direction (i.e., height direction) of the battery cells inside the battery housing. Also, in FIG. 7, the battery has 12 battery cells, but the number of battery cells is not particularly limited.

In this embodiment, the battery 40, 40a is, for example, a battery for an electric vehicle, and includes a number of battery cells 30. The battery 40, 40a includes a bottomed housing 41 that opens on one side. The housing 41 is preferably made of aluminum or an aluminum-based alloy. The battery cell 30 is disposed inside the housing 41 at an interior 44. An electrode is provided protruding from the upper part of the battery cell 30. The battery cells 30 are preferably pressed against each other in the housing 41 by applying a compressive force from both sides of the battery cells 30 using a screw or the like (not shown). The bottom 42 (an example of a cooling portion) of the housing 41 is provided with one or more water-cooled pipes 43 for flowing cooling water, which is an example of a coolant 45. The coolant 45 may be referred to as a cooling medium or a coolant. The battery cells 30 are disposed in the housing 41 with a fire-prevention sheet 1a sandwiched between adjacent battery cells 30.

The battery 40 shown in FIG. 7 (7A) is equipped with 12 cell units 35a according to the second embodiment. The fire prevention sheet 1a is attached to one of the widest sides of the battery cell 30. On the other hand, the battery 40a shown in FIG. 7 (7B) is equipped with 12 cell units 35b according to the third embodiment. The fire prevention sheet 1a is attached to both of the widest sides of the battery cell 30. The battery may include cell units 35, 35c, and 35d. The battery may also include a mixture of one or more cell units 35, 35a, 35b, 35c, and 35d.

3. Other Embodiments As described above, the preferred embodiments of the present invention have been described, but the present invention is not limited to these and can be practiced in various modifications.

For example, at least one of the two fire prevention sheets 1a that make up cell unit 35b may be fire prevention sheets 1, 1b, and 1c.

The flow paths 10, 20 are air passages that extend in the height direction of the battery cell 30 to which the fire prevention sheet 1, 1a, 1b, 1c is attached. A flow path different from the flow paths 10, 20 may be provided on the outer surface 12, 22 or inside the fire prevention sheet 1, 1a, 1b, 1c. The separate flow path may be formed, for example, so as to intersect with the flow paths 10, 20. In addition, the fire prevention sheet 1 and the rubber sheet 3, 3a are not limited to a foamed sheet of silicone rubber, and are not limited to a layer of a porous body.

In the above embodiment, the surface roughness of the attachment surface 11 and the outer surfaces 12, 22 is expressed as an arithmetic mean height (Sa) based on "ISO 25178 Surface Quality". However, instead of this, it may be expressed as a calculated average roughness: Ra based on JIS B 0601 using the surface roughness (also called line roughness) of the attachment surface 11 and the outer surfaces 12, 22. In that case, the Ra of the attachment surface 11 is preferably in the range of 0.02 to 0.4 μm, more preferably 0.03 to 0.3 μm. The Ra of the outer surfaces 12, 22 is preferably in the range of 0.45 to 500 μm, more preferably 0.5 to 500 μm.

Furthermore, the multiple components of each of the above-mentioned embodiments can be freely combined, except in cases where they cannot be combined with each other.

The present invention can be used in the field of batteries.

1, 1a, 1b, 1c...fire spread prevention sheet, 2, 2a, 2b...heat resistant reinforced sheet, 3, 3a...rubber sheet, 10...flow path, 11...attachment surface, 12...outer surface, 20...flow path, 22...outer surface, 30...battery cell, 35, 35a, 35b, 35c, 35d...cell unit, 40, 40a...battery.

Claims (5)

A fire prevention sheet that is disposed between a plurality of battery cells inside a battery and is capable of preventing the spread of fire by suppressing heat transfer to other battery cells when the battery cell is in an overheated state,
It is mainly composed of porous materials,
The porous body layer further includes a heat-resistant reinforced sheet having a higher heat resistance than the porous body layer,
At least one air flow path is provided from the lower end to the upper end when the air flow path is disposed on the battery ;
A fire spread prevention sheet, characterized in that the flow path is formed between the porous layer and the heat-resistant reinforced sheet . The fire spread prevention sheet according to claim 1 , characterized in that the heat-resistant reinforced sheet mainly contains talc. 2. The fire prevention sheet according to claim 1 , wherein the porous layer is a foamed sheet of silicone rubber. The fire spread prevention sheet according to any one of claims 1 to 3 is attached to at least one of two side surfaces in a direction in which the battery cells are arranged ,
the adhesion of the surface of the fire spread prevention sheet attached to the battery cell is lower than the adhesion of an outer surface on the opposite side of the attachment surface in the thickness direction of the fire spread prevention sheet;
A cell unit of the fire prevention sheet and the battery cell, characterized in that the arithmetic mean height (Sa) of the outer surface is greater than that of the attachment surface . A battery comprising a plurality of cell units according to claim 4 arranged side by side.