JP2020187868A - Heat transfer suppression sheet and battery pack - Google Patents

Abstract

To provide a heat transfer suppression sheet having an excellent heat transfer suppressing effect and having a strength capable of suppressing a decrease in the thickness of a heat insulating material even when the battery cell expands, thereby achieving both high heat insulating performance and high compression strength.SOLUTION: A heat transfer suppression sheet 10 includes a first heat insulating material 20 and a second heat insulating material 30. The thermal conductivity of the first heat insulating material 20 is lower than the thermal conductivity of the second heat insulating material 30. The compressive strength of the second heat insulating material 30 is higher than the compressive strength of the first heat insulating material 20.SELECTED DRAWING: Figure 1A

Description

The present invention relates to a heat transfer suppression sheet arranged between battery cells and an assembled battery in which the heat transfer suppression sheet is interposed between battery cells.

In recent years, from the viewpoint of environmental protection, the development of electric vehicles or hybrid vehicles driven by electric motors has been actively promoted. The electric vehicle, hybrid vehicle, or the like is equipped with an assembled battery in which a plurality of battery cells for serving as a power source for a driving electric motor are connected in series or in parallel.

Further, as this battery cell, a lithium ion secondary battery capable of high capacity and high output as compared with a lead storage battery, a nickel hydrogen battery, or the like is mainly used. In a high-capacity and high-output battery, if a certain battery cell suddenly rises in temperature due to an internal short circuit or overcharge of the battery and causes thermal runaway that continues to generate heat thereafter, heat is generated. The heat from the battery cell that caused the runaway propagates to other adjacent battery cells, which may cause thermal runaway of the other battery cells.

As a technique for suppressing heat propagation from a battery cell that has caused thermal runaway as described above, a heat transfer suppressing sheet is interposed between the battery cells. For example, Patent Document 1 describes a power storage device including one or more power storage elements, and a first plate material and a first plate material arranged on the side of the first power storage element, which is one of the one or more power storage elements. It is a two-plate material and includes a first plate material and a second plate material arranged so that their surfaces face each other, and the heat between the first plate material and the second plate material is higher than that of the first plate material and the second plate material. By forming a low thermal conductive layer (for example, an air layer) which is a layer of a substance having low conductivity, the radiant heat from the first storage element or the radiant heat toward the first storage element is blocked by two plates. Moreover, it is disclosed that the heat transfer from one of these two plates to the other is suppressed by the low thermal conductive layer, so that effective heat insulation between the power storage element and the other object can be realized. ..

Further, Patent Document 2 proposes a heat transfer suppressing sheet containing at least one of a mineral powder and a flame retardant and a matrix resin selected from a thermosetting resin, a thermoplastic elastomer, and rubber.

JP-A-2015-210113 Japanese Unexamined Patent Publication No. 2018-20606

Here, the volume of the battery cell expands due to charging or deterioration, and a load for compressing the inter-cell material (heat transfer suppressing sheet) may occur. Since the heat transfer suppressing sheet of Patent Document 1 is composed of a first plate material, a second plate material, and a low heat conductive layer such as an air layer arranged between the first plate material and the second plate material. When the battery cell expands and the heat transfer suppressing sheet is compressed, the thickness of the low thermal conductive layer is reduced, and the heat insulating property may be significantly impaired. Similarly, in the heat transfer suppressing sheet of Patent Document 2, when a compressive force acts on the endothermic material layer made of mineral powder, flame retardant, and matrix resin due to expansion of the battery cell, the thickness of the endothermic material layer decreases. As a result, the heat insulating property may be significantly impaired. Therefore, it is desired that the heat transfer suppressing sheet arranged between the battery cells has both high heat insulation performance and high compression strength.

The present invention has been made in view of such circumstances, and has excellent heat transfer suppressing effect and strength capable of suppressing a decrease in the thickness of the heat insulating material even when the battery cell expands. It is an object of the present invention to provide a heat transfer suppressing sheet capable of maintaining higher heat insulating performance.

The object of the present invention is achieved by the configuration of the following (1) relating to the heat transfer suppressing sheet.
(1) Includes a first heat insulating material and a second heat insulating material.
The thermal conductivity of the first heat insulating material is lower than the thermal conductivity of the second heat insulating material.
And,
The compressive strength of the second heat insulating material is higher than the compressive strength of the first heat insulating material.
Heat transfer suppression sheet.

Further, preferred embodiments of the present invention relating to the heat transfer suppressing sheet relate to the following (2) to (13).

(2) The heat transfer suppressing sheet according to (1), wherein the second heat insulating material is arranged in the central portion when viewed from at least one of the surfaces perpendicular to the sheet thickness direction.
(3) The heat transfer suppressing sheet according to (1), wherein the second heat insulating material is dispersed and arranged at a plurality of locations when viewed from at least one of the surfaces perpendicular to the sheet thickness direction.
(4) The heat transfer suppressing sheet according to (1), wherein the first heat insulating material and the second heat insulating material are arranged in a stripe shape when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. ..
(5) Seen from at least one of the surfaces perpendicular to the sheet thickness direction
The second heat insulating material is formed in a grid pattern.
The heat transfer suppressing sheet according to (1), wherein the first heat insulating material is arranged in the grid-like frame.
(6) Seen from at least one of the surfaces perpendicular to the sheet thickness direction
The heat transfer suppressing sheet according to (1), wherein the second heat insulating material is arranged in a frame shape covering the outer periphery of the first heat insulating material.
(7) Seen from at least one of the surfaces perpendicular to the sheet thickness direction
The heat transfer suppressing sheet according to (1), wherein the second heat insulating material is arranged in a frame shape that covers the outer periphery of the first heat insulating material and in a grid shape that divides the inside of the frame into a plurality of pieces.

(8) The heat transfer according to any one of (1) to (7), wherein the second heat insulating material is arranged so as to penetrate from one surface perpendicular to the sheet thickness direction to the other surface. Suppression sheet.
(9) The heat transfer according to any one of (1) to (7), wherein the second heat insulating material is not arranged so as to penetrate from one surface perpendicular to the sheet thickness direction to the other surface. Suppression sheet.
(10) The heat transfer suppressing sheet according to any one of (1) to (9), wherein the heat transfer suppressing sheet is covered with a packaging material.
(11) Of the pair of surfaces perpendicular to the sheet thickness direction, the surface on the side where the projected area of the second heat insulating material is large in the sheet thickness direction.
When the projected area of the first heat insulating material in the sheet thickness direction is S _1, and the projected area of the second heat insulating material in the sheet thickness direction is S ₂ .
The heat transfer suppressing sheet according to any one of (1) to (10), wherein S ₂ / (S ₁ + S ₂ ) is 50% or less.
(12) The heat transfer suppressing sheet according to (11), wherein S ₂ / (S ₁ + S ₂ ) is 20% or less.
(13) The heat transfer suppressing sheet according to (12), wherein S ₂ / (S ₁ + S ₂ ) is 5% or less.

Further, the object of the present invention is achieved by the configuration of the following (14) relating to the assembled battery.
(14) An assembled battery in which a plurality of battery cells are connected in series or in parallel.
An assembled battery in which a heat transfer suppressing sheet according to any one of (1) to (13) is interposed between the battery cells.

The heat transfer suppressing sheet of the present invention includes a first heat insulating material and a second heat insulating material, and the heat conductivity of the first heat insulating material is lower than that of the second heat insulating material, and , The compressive strength of the second heat insulating material is higher than the compressive strength of the first heat insulating material. Therefore, the first heat insulating material having a lower thermal conductivity than the second heat insulating material suppresses heat transfer from one side to the other side of the heat transfer suppressing sheet, and has a higher compressive strength than the first heat insulating material. The high second heat insulating material can resist an external impact or pressing force to suppress a decrease in the thickness of the first heat insulating material and suppress a decrease in heat insulating performance. Therefore, it is possible to achieve both high heat insulation performance and high compression strength, which are problems as a heat transfer suppressing sheet.

For example, the mica sheet, which is an example of the second heat insulating material, has high insulation and high compressive strength, but is inferior to the inorganic fiber-based / inorganic particle-based material, which is an example of the first heat insulating material, in terms of heat insulating property. On the other hand, it is difficult for inorganic fiber-based / inorganic particle-based sheets to have high compressive strength like mica sheets. Therefore, by combining these materials, it is possible to achieve both high heat insulation performance and high compression strength characteristics, which are difficult to obtain with each single material. This technology can be suitably used as a heat transfer suppression sheet for effectively suppressing thermal runaway of a lithium ion battery mounted on an electric vehicle.

Further, in the assembled battery of the present invention, the above-mentioned heat transfer suppressing sheet is interposed between the battery cells. Therefore, even if the battery cell expands due to thermal expansion of the battery cell and a pressing force acts on the adjacent heat transfer suppressing sheet, the pressing force is received by the second heat insulating material, and the heat transfer suppressing sheet, particularly the first one. It is possible to suppress the decrease in the thickness of the heat insulating material and maintain a good heat insulating function.

FIG. 1A is a front view and a side view of the heat transfer suppressing sheet according to the first embodiment of the present invention. FIG. 1B is a front view and a side view of the heat transfer suppressing sheet according to the modified example of the first embodiment. FIG. 1C is a front view and a side view of the heat transfer suppressing sheet according to another modification of the first embodiment. FIG. 2 is a front view and a side view of the heat transfer suppressing sheet according to the second embodiment of the present invention. FIG. 3A is a front view and a side view of the heat transfer suppressing sheet according to the third embodiment of the present invention. FIG. 3B is a front view and a side view of the heat transfer suppressing sheet according to the modified example of the third embodiment. FIG. 4 is a front view and a side view of the heat transfer suppressing sheet according to the fourth embodiment of the present invention. FIG. 5 is a front view and a side view of the heat transfer suppressing sheet according to the fifth embodiment of the present invention. FIG. 6 is a front view and a side view of the heat transfer suppressing sheet according to the sixth embodiment of the present invention. FIG. 7 is a front view and a side view of the heat transfer suppressing sheet according to the seventh embodiment of the present invention. FIG. 8 is a cross-sectional view schematically showing an example of an assembled battery. FIG. 9A is a front view and a side view of the heat transfer suppression sheet used in the test of Example 1. FIG. 9B is a front view and a side view of the heat transfer suppression sheet used in the test of Example 2. FIG. 9C is a front view and a side view of the heat transfer suppression sheet used in the test of Example 3. FIG. 10A is a front view and a side view of the heat transfer suppressing sheet used in the test of Comparative Example 1. FIG. 10B is a front view and a side view of the heat transfer suppressing sheet used in the test of Comparative Example 2. FIG. 11 is a graph showing a comparison of the performance of the heat transfer suppression sheets of Examples 1 to 3 and Comparative Examples 1 and 2. FIG. 12A is a front view and a side view of the heat transfer suppression sheet used in the test of Example 4. FIG. 12B is a front view and a side view of the heat transfer suppression sheet used in the test of Example 5. FIG. 13 is a graph showing a comparison of the performance of the heat transfer suppression sheets of Example 4, Example 5, Comparative Example 1 and Comparative Example 2.

Hereinafter, each embodiment of the heat transfer suppressing sheet according to the present invention will be described in detail with reference to the drawings.

The present inventors have diligently studied a heat transfer suppression sheet that is arranged between battery cells and can effectively suppress heat from a battery cell that has caused thermal runaway from propagating to adjacent battery cells. I went. When the heat transfer suppression sheet was composed only of a heat insulating material having a high heat insulating effect such as inorganic particles and inorganic fibers, the obtained heat insulating effect was lower than the theoretical value. The reason is that the heat insulating material such as inorganic particles and inorganic fibers has high heat insulating performance (that is, low thermal conductivity), but has low compressive strength, so that the heat insulating material is compressed by the expansion of the battery cell and becomes thick. It is considered that this is due to the decrease in heat insulation due to the thinning.

Therefore, the heat transfer suppressing sheet according to the present embodiment has higher heat insulating performance (that is, lower thermal conductivity) and lower compression strength than the second heat insulating material, which is a key point of the first heat insulating material. In addition, a second heat insulating material having a lower heat insulating performance (that is, a higher thermal conductivity) but a higher compressive strength than the first heat insulating material is arranged so that the first heat insulating material has a lower compressive strength. It has been found that it is possible to improve the heat insulation performance of the heat transfer suppression sheet as a whole by suppressing the thickness reduction. That is, as described above, by balancing the heat insulating performance of the heat insulating material with the reduction of the thickness of the heat insulating material, both high heat insulating performance and high compression strength, which are difficult to obtain with each single material, are achieved. It becomes possible.

Although the present invention is based on such findings, each embodiment of the present invention will be described in detail below with reference to the drawings.

[Heat transfer suppression sheet]
(First Embodiment)
FIG. 1A is a front view and a side view schematically showing a heat transfer suppressing sheet according to the first embodiment of the present invention. As shown in FIG. 1A, the heat transfer suppressing sheet 10 of the present embodiment has high compression strength as compared with the first heat insulating material 20 having high heat insulating performance but low compressive strength and the first heat insulating material 20. A second heat insulating material 30 which has but has low heat insulating performance is provided. That is, the heat transfer suppressing sheet 10 is configured by arranging the first and second heat insulating materials 20 and 30 having different compressive strength and heat insulating performance in the sheet surface direction, respectively.

Specifically, in the heat transfer suppressing sheet 10, as shown in FIG. 1A, the first heat insulating material 20 is formed in a sheet shape having, for example, a length L, a width W, and a thickness t1, and the sheet thickness direction ( A second heat insulating material 30 having a thickness of t2 is integrally embedded or fixed in a through hole 21 formed in the center thereof when viewed from at least one of the surfaces perpendicular to the vertical direction in the drawing. Has. That is, the second heat insulating material 30 is arranged so as to penetrate from one surface 20a perpendicular to the sheet thickness direction of the first heat insulating material 20 to the other surface 20b.
Here, the second heat insulating material 30 is arranged so as to penetrate from one surface 20a to the other surface 20b of the first heat insulating material 20, and the compressive force due to the expansion of the battery cell 40 is determined by the battery cell 40. Since the second heat insulating material 30 is surely received from the initial stage of expansion, the first heat insulating material 20 is hardly compressed. Therefore, the decrease in thickness of the heat transfer suppressing sheet 10, particularly the first heat insulating material 20, can be suppressed as much as possible, and the heat insulating function can be maintained satisfactorily.

However, the thickness t2 of the second heat insulating material 30 does not have to be the same as the thickness t1 of the first heat insulating material 20, and may be thicker or thinner than the thickness t1 of the first heat insulating material 20. , And may have the same thickness (t2 ≧ t1 or t2 ≦ t1).

When the thickness t2 of the second heat insulating material 30 is thicker than the thickness t1 of the first heat insulating material 20 (that is, t2> t1), the expanding battery cell 40 and the first heat insulating material 20 described later An air layer is formed between them, but this is not a problem because the air layer has a heat insulating function. Further, when the thickness t2 of the second heat insulating material 30 is thinner than the thickness t1 of the first heat insulating material 20 (that is, t2 <t1), the first heat insulating material 20 is the second heat insulating material 30. Can be compressed to a thickness of t2.
The thickness t2 of the second heat insulating material 30 is the same as the thickness t1 of the first heat insulating material 20 (that is, t1 = t2), but the unevenness is formed on the pair of surfaces perpendicular to the sheet thickness direction. It is preferable because there is no foreign matter accumulation, it is easy to stack and pack the sheet when transporting it, mistakes during material handling or processing handling, and sheet damage are unlikely to occur. Note that t1 = t2 here does not mean that the thickness t1 and the thickness t2 are completely the same, and includes the case where the thickness t1 and the thickness t2 are considered to be substantially the same due to a dimensional error or the like. ..

The above relationship regarding the thickness t1 of the first heat insulating material 20 and the thickness t2 of the second heat insulating material 30 is the same in each of the following embodiments. The shape of the through hole 21 and the second heat insulating material 30 shown in FIG. 1A is circular, but the shape is not particularly limited.

The first heat insulating material 20 has a main purpose of heat insulating and is selected from materials having high heat insulating performance, and the second heat insulating material 30 has a main purpose of improving compressive strength and is selected from materials having high compressive strength. ..

The first heat insulating material 20 whose main purpose is heat insulation includes an inorganic material or an organic material formed in a fibrous or blanket shape (hereinafter collectively referred to as “fibrous”), or a particulate or bulk shape. It is composed of inorganic materials and organic materials formed in a dense body, a sheet, a plate, and a powder (hereinafter collectively referred to as "particulates").

As the fibrous inorganic material, at least one can be selected from the group consisting of alumina, RCF, AES, rock wool, basalt fiber, silica fiber, zirconia fiber, and glass wool. As the fibrous organic material, a thermosetting resin or a thermoplastic resin can be selected. Further, as the particulate inorganic material, at least one can be selected from the group consisting of alumina, zirconia, silica, titania, cordierite, synthetic silica, and airgel. Particulate organic materials include thermosetting resins and thermoplastic resins. It can also be a complex such as an airgel blanket.

The second heat insulating material 30 whose main purpose is to improve the compressive strength is an inorganic material or an organic material formed in a bulk shape, a compact body, a sheet shape, or a plate shape (hereinafter collectively referred to as “bulk shape”). It is composed. As the bulk-like inorganic material, at least one can be selected from the group consisting of alumina, silica, zirconia, titania, cordierite, mica, calcium silicate, pearlite, zeolite, aluminum hydroxide, vermiculite, and calcium carbonate. As the bulk organic material, at least one can be selected from the group consisting of thermosetting resin, thermoplastic resin, thermoplastic elastomer, and rubber. Further, at least one of the second heat insulating material 30 may be selected from the group consisting of SUS, iron, copper and aluminum.

As will be described later (see FIG. 8), in the assembled battery 100 of the present embodiment, the heat transfer suppression sheet 10 is arranged between the battery cells 40, and a plurality of battery cells 40 are connected in series or in parallel (see FIG. 8). The connected state is not shown) and is stored in the battery case 50.

As the battery cell 40, for example, a lithium ion secondary battery is preferably used, but the battery cell 40 is not particularly limited to this, and can be applied to other secondary batteries.

Then, the battery cell 40 that has caused thermal runaway expands itself and exerts a large pressing force on the heat transfer suppressing sheet 10. However, most of this pressing force is received by the second heat insulating material 30, which has high compressive strength and is arranged so as to penetrate from one surface 20a to the other surface 20b of the first heat insulating material 20. , The influence of the pressing force on the first heat insulating material 20 is greatly reduced. That is, the decrease in thickness of the first heat insulating material 20 is suppressed to the minimum. As a result, it is possible to suppress a decrease in the heat insulating performance of the heat transfer suppressing sheet 10 as a whole, and the heat from the battery cell 40 that caused the thermal runaway propagates to another adjacent battery cell 40, thereby causing another. Effectively prevents the battery cell 40 from causing thermal runaway.

Further, in the battery cell 40 that expands due to thermal runaway, the central portion thereof tends to swell most, but the second heat insulating material 30 having a high compressive strength is placed in the central portion of the first heat insulating material 20, that is, the battery. By arranging the battery cells 40 so as to face each other near the center of the cells 40, the expansion of the battery cells 40 can be suppressed, and the decrease in the thickness of the first heat insulating material 20 can be effectively suppressed.

(Modified example of the first embodiment)
FIG. 1B is a front view and a side view schematically showing a heat transfer suppressing sheet according to a modified example of the first embodiment of the present invention. As shown in FIG. 1B, in the heat transfer suppressing sheet 10 of this modified example, the first heat insulating material 20 is formed in a sheet shape having, for example, a length L, a width W, and a thickness t1 in the sheet thickness direction (FIG. 1B). A second heat insulating material 30 having a thickness t2 is integrally embedded in a recess 21a having a depth t2 formed in the center thereof when viewed from the other surface 20b of the surfaces perpendicular to the middle and vertical directions. Or it has a fixed configuration. That is, the second heat insulating material 30 is not arranged so as to penetrate the first heat insulating material 20 in the sheet thickness direction.
In this case, the expansion of the battery cell 40 can compress the first heat insulating material 20 until it reaches the thickness t2 of the second heat insulating material 30, but after that, the compressive force due to the expansion of the battery cell 40 is applied. , Can be reliably received by the second heat insulating material 30. Therefore, it is possible to suppress a decrease in the thickness of the heat transfer suppressing sheet 10, particularly the first heat insulating material 20, and maintain a good heat insulating function.

(Other Modified Examples of First Embodiment)
FIG. 1C is a front view and a side view schematically showing a heat transfer suppressing sheet according to another modification of the first embodiment of the present invention. As shown in FIG. 1C, in the heat transfer suppressing sheet 10 of this modified example, the first heat insulating material 20 is formed in a sheet shape having, for example, a length L, a width W, and a thickness t1 in the sheet thickness direction (FIG. 1C). A second heat insulating material 30 having a thickness of t2 is integrally embedded or fixed in a recess 21a having a depth of t2 formed in the center thereof when viewed from a plane perpendicular to the middle and vertical directions. Have. The second heat insulating material 30 is common to the above modified example in that the second heat insulating material 30 is not arranged so as to penetrate the first heat insulating material 20 in the sheet thickness direction. However, the second heat insulating material 30 is not exposed on the surface not only on one surface 20a but also on the other surface 20b.
Even in this case, as in the above modification, the expansion of the battery cell 40 can compress the first heat insulating material 20 until it reaches the thickness t2 of the second heat insulating material 30, but after that, the battery cell 40 The compressive force due to expansion can be reliably received by the second heat insulating material 30. Therefore, it is possible to suppress a decrease in the thickness of the heat transfer suppressing sheet 10, particularly the first heat insulating material 20, and maintain a good heat insulating function.

As a method of producing the heat transfer suppressing sheet according to this modification, for example, as shown in FIG. 1C, a second heat insulating material is used for each of the two first heat insulating materials 20 (24, 26). It is conceivable to provide a recess for accommodating the 30 and to superimpose the two first heat insulating materials 20 (24, 26) in a state where the second heat insulating material 30 is stored in the recess.

(Second Embodiment)
FIG. 2 is a front view and a side view schematically showing a heat transfer suppressing sheet according to a second embodiment of the present invention. As shown in FIG. 2, in the heat transfer suppressing sheet 10 of the present embodiment, the first heat insulating material 20 is formed in a sheet shape having, for example, a length L, a width W, and a thickness t1, and is perpendicular to the sheet thickness direction. A plurality of second heat insulating materials 30 having a thickness of t2 are dispersedly arranged at a plurality of locations when viewed from at least one of the surfaces. Further, the second heat insulating material 30 is arranged so as to penetrate from one surface 20a perpendicular to the sheet thickness direction of the first heat insulating material 20 to the other surface 20b. The size, shape, position, and number of the second heat insulating material 30 can be arbitrarily set, but it is preferable that the second heat insulating material 30 is uniformly arranged from the center of the first heat insulating material 20. By arranging the plurality of second heat insulating materials 30 in a dispersed manner in this way, the expansion of the battery cell 40 can be effectively suppressed, and the deterioration of the heat insulating performance due to the decrease in the thickness of the first heat insulating material 20 is suppressed. be able to.
Since other configurations and operations are the same as those of the heat transfer suppressing sheet of the first embodiment, the description thereof will be omitted. The same description will be omitted in each of the following embodiments.

(Third Embodiment)
FIG. 3A is a front view and a side view schematically showing a heat transfer suppressing sheet according to a third embodiment of the present invention. As shown in FIG. 3A, in the heat transfer suppressing sheet 10 of the present embodiment, a plurality of first heat insulating materials 20 having a thickness t1 and a second heat insulating material 30 having a thickness t2 formed in a rectangular shape are used.
When viewed from at least one of the surfaces perpendicular to the sheet thickness direction, the sheets are arranged in a stripe shape and formed into a sheet shape having a length L, a width W, and a thickness t1. According to this configuration, the expansion of the battery cell 40 is effective by arranging the first heat insulating material 20 having a low compressive strength and the second heat insulating material 30 having a high compressive strength alternately dispersed in a stripe shape. It is possible to suppress the deterioration of the heat insulating performance due to the decrease in the thickness of the first heat insulating material 20.

(Modified example of the third embodiment)
FIG. 3B is a front view and a side view schematically showing a heat transfer suppressing sheet according to a modified example of the third embodiment of the present invention. As shown in FIG. 3B, in the heat transfer suppressing sheet 10 of this modified example, a plurality of second heat insulating materials 30 having a thickness t2 formed in a triangular columnar shape are formed, and a plurality of first heat insulating materials having a thickness t1 are provided. It is sandwiched alternately by 20 and arranged in a stripe shape. As shown in FIG. 3B, the ridges 31 of the triangular prisms of the second heat insulating material 30 may be oriented in opposite directions or in the same direction. If the ridge line 31 is sharp, the battery cell 40 may be damaged. Therefore, it is preferable to take measures such as forming a roundness at the tip of the ridge line 31. Further, the cross-sectional shape of the second heat insulating material 30 is not limited to a polygon, and can be any cross-sectional shape.

(Fourth Embodiment)
FIG. 4 is a front view and a side view schematically showing a heat transfer suppressing sheet according to a fourth embodiment of the present invention. As shown in FIG. 4, in the heat transfer suppressing sheet 10 of the present embodiment, the second heat insulating material 30 having a thickness t2 is formed in a grid pattern when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. A first heat insulating material 20 having a thickness of t1 is arranged in each of the lattice frames. According to this configuration, by arranging the second heat insulating material 30 having a high compressive strength in a grid pattern, the compressive strength of the heat transfer suppressing sheet 10 can be increased, and cell expansion can be effectively suppressed.

(Fifth Embodiment)
FIG. 5 is a front view and a side view schematically showing a heat transfer suppressing sheet according to a fifth embodiment of the present invention. As shown in FIG. 5, in the heat transfer suppressing sheet 10 of the present embodiment, a second heat insulating material 30 having a thickness of t2 is formed in a frame shape when viewed from at least one of the surfaces perpendicular to the sheet thickness direction, and is substantially formed. The outer periphery 22 (four sides of the outer circumference) of the first heat insulating material 20 in the shape of a rectangular sheet is bordered by the second heat insulating material 30. According to this configuration, since the second heat insulating material 30 having a high compressive strength is arranged in a frame shape covering the outer peripheral 22 of the first heat insulating material 20, the mechanical strength of the heat transfer suppressing sheet 10 is improved. However, the handleability of the heat transfer suppressing sheet 10 is improved.

(Sixth Embodiment)
FIG. 6 is a front view and a side view schematically showing a heat transfer suppressing sheet according to a sixth embodiment of the present invention. As shown in FIG. 6, in the heat transfer suppressing sheet 10 of the present embodiment, the second heat insulating material 30 having a thickness t2 is formed in a so-called paddle shape when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. A first heat insulating material 20 having a thickness of t1 is arranged in each frame. According to this configuration, since the second heat insulating material 30 is arranged in a frame shape and in a grid pattern that divides the inside of the frame into a plurality of frames, the mechanical strength of the heat transfer suppressing sheet 10 is further improved, and heat transfer is further performed. Cell expansion can be effectively suppressed not only in the vicinity of the center of the suppression sheet 10 but also in the peripheral portion. In addition, the handleability of the heat transfer suppressing sheet 10 is improved.

(7th Embodiment)
FIG. 7 is a front view and a side view schematically showing a heat transfer suppressing sheet according to a seventh embodiment of the present invention. As shown in FIG. 7, the heat transfer suppressing sheet 10 of the present embodiment has a plurality of first heat insulating sheets arranged in a stripe shape (see FIG. 3A) when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. The material 20 and the second heat insulating material 30 are further covered with a packaging material 32 such as a film or a non-woven fabric. According to this configuration, the handleability of the heat transfer suppressing sheet 10 is improved, and the assembly work of the assembled battery 100 becomes easy.

[Battery set]
FIG. 8 is a cross-sectional view schematically showing an example of an assembled battery. As shown in FIG. 8, the assembled battery 100 according to the present embodiment has the above-mentioned heat transfer suppressing sheet 10 interposed between the battery cells 40. Specifically, as shown in FIG. 8, in the assembled battery 100, a plurality of battery cells 40 are arranged side by side, connected in series or in parallel, and housed in the battery case 50. Each battery cell 40 A heat transfer suppressing sheet 10 is interposed between them.

The pressing force from the adjacent battery cell 40 is constantly acting on the battery cell 40, and most of the pressing force is received by the heat transfer suppressing sheet 10, particularly the second heat insulating material 30 having high compression strength. .. Further, when thermal runaway occurs, most of the pressing force by the expanding battery cell 40 is also received by the second heat insulating material 30 having high compressive strength, so that the reduction in the thickness of the first heat insulating material 20 is suppressed. .. As a result, the deterioration of the heat insulating performance of the heat transfer suppressing sheet 10 is suppressed, and the chain of thermal runaway of the battery cell 40 is effectively prevented. That is, it is possible to achieve both high heat insulation performance and high compression strength, which are problems of the heat transfer suppressing sheet 10 used between the battery cells 40.

Hereinafter, the present invention will be further described with reference to examples, but the present invention is not limited thereto.

(Example 1)
FIG. 9A is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Example 1. As shown in FIG. 9A, an alumina fiber blanket, which is an example of the first heat insulating material 20, is formed in the form of a sheet having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm, and a penetration having a diameter of D = 25.4 mm is formed in the central portion thereof. A hole 21 was provided. Then, a mica sheet having a thickness of 2 mm, which is an example of the second heat insulating material 30, is fitted into the semicircular region of the through hole 21, and the first heat insulating material 20 is fitted into the remaining semicircular region. The above alumina fiber blanket having a thickness of 2 mm, which is an example, was fitted to prepare Sample 1 used in Example 1. That is, the thickness of the alumina fiber blanket and the thickness of the mica sheet are the same, and the mica sheet is arranged so as to penetrate from one surface 20a to the other surface 20b of the alumina fiber blanket.

Here, of the pair of surfaces of the heat transfer suppressing sheet 10 perpendicular to the sheet thickness direction, the surface on the side where the projected area of the second heat insulating material 30 is large in the sheet thickness direction is the first heat insulating material in the sheet thickness direction. The projected area of 20 is defined as S _1, and the projected area of the second heat insulating material 30 in the sheet thickness direction is defined as S ₂ . As shown in FIG. 9A, in the heat transfer suppressing sheet 10, the projected area of the second heat insulating material 30 in the sheet thickness direction when viewed from one surface 20a and the sheet when viewed from the other surface 20b. If the projected area of the second heat insulating material 30 in the thickness direction is the same, it does not matter which surface is adopted, but for example, as shown in FIG. 3B, the second having a triangular cross section has a columnar cross section. When the heat insulating material 30 is used, the projected area of the second heat insulating material 30 in the sheet thickness direction may be different between one surface 20a and the other surface 20b. In that case, as described above, the surface on the side where the projected area of the second heat insulating material 30 is large in the sheet thickness direction is adopted, and the projected area of the first heat insulating material 20 in the sheet thickness direction on that surface is S. _It is set to _1, and the projected area of the second heat insulating material 30 in the sheet thickness direction is defined as S ₂ .

Further, the above S ₁ and S ₂ are defined by the projected area of each heat insulating material in the sheet thickness direction, as shown in FIG. 9A, the thickness t1 of the first heat insulating material 20 and the second heat insulating material 30. When the thickness t2 of the second heat insulating material is the same, there is no problem by setting the area of each heat insulating material on the sheet surface. For example, the thickness t2 of the second heat insulating material 30 is the area of the first heat insulating material 20. This is because it is thinner than the thickness t1, that is, when the second heat insulating material 30 is buried from the sheet surface, the area of the second heat insulating material 30 is exposed when viewed from the sheet thickness direction.

Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Example 1, _{i.e., (S 2 / (S 1} + S 2)) was about 4%.

(Example 2)
FIG. 9B is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Example 2. As shown in FIG. 9B, an alumina fiber blanket, which is an example of the first heat insulating material 20, is formed in a sheet shape having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm, and a penetration having a diameter of D = 25.4 mm is formed in the central portion thereof. A hole 21 was provided. Then, a mica sheet having a thickness of 2 mm, which is an example of the second heat insulating material 30, was fitted into the through hole 21 to prepare the sample 2 used in Example 2. That is, the thickness of the alumina fiber blanket and the thickness of the mica sheet are the same, and the mica sheet is arranged so as to penetrate the alumina fiber blanket from one surface 20a to the other surface 20b.
Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Example 2, _{i.e., (S 2 / (S 1} + S 2)) was about 8%.

(Example 3)
FIG. 9C is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Example 3. As shown in FIG. 9C, an alumina fiber blanket, which is an example of the first heat insulating material 20, is formed into a sheet having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm, and a penetration having a square having a side of 50 mm at the center thereof. A hole 21 was provided. Then, a mica sheet having a thickness of 2 mm, which is an example of the second heat insulating material 30, was fitted into the through hole 21 to prepare the sample 3 used in Example 3. That is, the thickness of the alumina fiber blanket and the thickness of the mica sheet are the same, and the mica sheet is arranged so as to penetrate the alumina fiber blanket from one surface 20a to the other surface 20b.
Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Example 2, _{i.e., (S 2 / (S 1} + S 2)) was about 39%.

(Comparative Example 1)
FIG. 10A is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Comparative Example 1. As shown in FIG. 10A, an alumina fiber blanket, which is an example of the first heat insulating material 20, was formed into a sheet having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm to prepare a sample 4 used in Comparative Example 1. .. That is, the sample 4 is formed only of the alumina fiber blanket.
Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Comparative Example 1, _{i.e., (S 2 / (S 1} + S 2)) was 0%.

(Comparative Example 2)
FIG. 10B is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Comparative Example 2. As shown in FIG. 10B, a mica sheet, which is an example of the second heat insulating material 30, was formed into a sheet having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm to prepare a sample 5 used in Comparative Example 2. That is, the sample 5 is formed only of the mica sheet.
Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Comparative Example 2, _{i.e., (S 2 / (S 1} + S 2)) was 100%.

Subsequently, the following tests were conducted in order to confirm the heat transfer suppressing effect of each of the samples 1 to 5 (heat transfer suppressing sheet 10) prepared above. First, on one surface side of each of Samples 1 to 5 (heat transfer suppression sheet 10) of Examples 1 to 3 and Comparative Examples 1 and 2, a heater simulating a battery cell causing a heat runaway is suppressed by heat transfer. It was arranged 40 mm apart from the sheet 10, and on the other surface side, a metal plate (without heating) simulating an adjacent battery cell was arranged in contact with the heat transfer suppressing sheet 10. Subsequently, after the heater is heated and the temperature reaches 800 ° C., each sample 1 to 5 is pressed with a force of 16 kPa or 469 kPa with the heater and the metal plate, and the surface of the metal plate with respect to the elapsed time after heating the heater. The temperature change of was measured. After pressing with a predetermined load, the power of the heater was turned off.

A graph in which the maximum temperature (° C.) of the metal plate surface in Examples 1 to 3 and Comparative Examples 1 and 2 is plotted is shown in FIG.

As shown in FIG. 11, the maximum temperature of the metal plate surface in Examples 1 to 3 in which the second heat insulating material 30 having a high compressive strength is arranged in the central portion of the first heat insulating material 20 is the first heat insulating material. It can be seen that the temperature is lower than that of Comparative Example 1 formed only of 20 and Comparative Example 2 formed only of the second heat insulating material 30.
Further, it can be seen that in Comparative Example 1 composed of only the first heat insulating material 20 having low thermal conductivity, that is, high heat insulating performance, the temperature is higher than that in Examples 1 to 3. That is, the reason why the heat insulating effect is small is that the compressive force due to the expansion of the battery cell 40 acts on the first heat insulating material 20, so that the high heat insulating performance of the first heat insulating material 20 is canceled out. It is considered that the thickness of the heat insulating material 20 of the above is reduced.
On the other hand, in Examples 1 to 3, the reduction of the thickness of the first heat insulating material 20 is suppressed by arranging the second heat insulating material 30 having high compressive strength in the central portion of the first heat insulating material 20. It can be seen that it is effectively insulated.

Further, as can be seen from FIG. 11, the above S ₂ / (S ₁ + S ₂ ) is preferably 50% or less, more preferably 20% or less, still more preferably 5% or less.

Further, even if the values of S ₂ / (S ₁ + S ₂ ) are the same, the higher the compressive force of the heat transfer suppressing sheet 10, the higher the temperature, which is the compressive force acting on the heat transfer suppressing sheet 10. This is because the thickness of the heat transfer suppressing sheet 10 is reduced due to this, and the heat insulating performance is lowered.
From the above, it is understood that the technique of the present invention makes it possible to achieve both high heat insulation performance and high compression strength of the heat transfer suppressing sheet 10.

In the first to third embodiments, the thickness of the first heat insulating material 20 and the thickness of the second heat insulating material 30 are the same, that is, the second heat insulating material 30 is the first heat insulating material 20. This is a case where it is arranged so as to penetrate from one surface 20a to the other surface 20b. Subsequently, the thickness of the second heat insulating material 30 is thinner than the thickness of the first heat insulating material 20, and the second heat insulating material 30 transfers the first heat insulating material 20 from one surface 20a to the other surface 20b. A similar test was performed for cases where it did not penetrate.

(Example 4)
FIG. 12A is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Example 4. As shown in FIG. 12A, an alumina fiber blanket, which is an example of the first heat insulating material 20, is formed in the form of a sheet having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm, and has a diameter D = 25.4 mm at the center thereof. A recess 21a having a depth of 1 mm was provided. Then, a mica sheet having a thickness of 1 mm, which is an example of the second heat insulating material 30, is fitted into the semicircular region of the recess 21a, and an example of the first heat insulating material 20 is fitted into the remaining semicircular region. The above alumina fiber blanket having a thickness of 1 mm was fitted to prepare sample 4 used in Example 4.
Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Example 4, _{i.e., (S 2 / (S 1} + S 2)) was about 4%.

(Example 5)
FIG. 12B is a front view and a side view of the heat transfer suppressing sheet 10 used in the test of Example 5. As shown in FIG. 12B, an alumina fiber blanket, which is an example of the first heat insulating material 20, is formed in the form of a sheet having a length of 80 mm, a width of 80 mm, and a thickness of 2 mm, and has a diameter D = 25.4 mm at the center thereof. A recess 21a having a depth of 1 mm was provided. Then, a mica sheet having a thickness of 1 mm, which is an example of the second heat insulating material 30, was fitted into the recess 21a to prepare the sample 5 used in Example 5.
Then, based on the definition described above, the ratio of _{S 2} to the sum of _S 1 + _{S 2} in Example 5, _{i.e., (S 2 / (S 1} + S 2)) was about 8%.

Subsequently, the heat transfer suppressing effect of Sample 4 and Sample 5 was confirmed by the same test method as described above. FIG. 13 shows a graph in which the maximum temperature (° C.) of the metal plate surface in Example 4, Example 5, Comparative Example 1 and Comparative Example 2 is plotted.

As shown in FIG. 13, the metal in Examples 4 and 5 in which the second heat insulating material 30 having a high compressive strength is arranged in the central portion of the first heat insulating material 20 as in the cases of Examples 1 to 3. It can be seen that the maximum temperature of the plate surface is lower than the temperatures of Comparative Example 1 formed only of the first heat insulating material 20 and Comparative Example 2 formed only of the second heat insulating material 30. That is, it is shown that the same tendency as in the case where the second heat insulating material 30 does not penetrate from one surface 20a to the other surface 20b in the first heat insulating material 20 can be obtained. Was done.

The present invention is not limited to the above-described embodiments, modifications, and embodiments, and modifications, improvements, and the like can be made as appropriate. The heat transfer suppression sheet of the present invention is interposed between battery cells to prevent other battery cells from causing thermal runaway due to heat from the battery cell that caused thermal runaway when the battery cell causes thermal runaway. However, the application is not limited to this application. For example, it can also be used as a heat transfer suppression sheet for automobile exhaust pipes. In addition, it is very difficult to handle, but it is possible to handle materials (airgel, synthetic silica, etc.) that are clearly excellent in physical properties by making a frame from a rigid material and arranging it inside. It can also be a heat insulating material having excellent physical properties and mechanical strength when mounted.

10 Heat transfer suppression sheet 20 First heat insulating material 20a One side 20b The other side 21 Through hole 22 Outer periphery 30 Second heat insulating material 32 Packaging material 40 Battery cell 50 Battery case 100 assembled battery S ₁ First heat insulating material Surface area S ₂ Surface area of the second heat insulating material

Claims (14)

Including a first heat insulating material and a second heat insulating material,
The thermal conductivity of the first heat insulating material is lower than the thermal conductivity of the second heat insulating material.
And,
The compressive strength of the second heat insulating material is higher than the compressive strength of the first heat insulating material.
Heat transfer suppression sheet. The heat transfer suppressing sheet according to claim 1, wherein the second heat insulating material is arranged in the central portion when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. The heat transfer suppressing sheet according to claim 1, wherein the second heat insulating material is dispersedly arranged at a plurality of locations when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. The heat transfer suppressing sheet according to claim 1, wherein the first heat insulating material and the second heat insulating material are arranged in a stripe shape when viewed from at least one of the surfaces perpendicular to the sheet thickness direction. Seen from at least one of the planes perpendicular to the sheet thickness direction
The second heat insulating material is formed in a grid pattern.
The heat transfer suppressing sheet according to claim 1, wherein the first heat insulating material is arranged in the grid-like frame. Seen from at least one of the planes perpendicular to the sheet thickness direction
The heat transfer suppressing sheet according to claim 1, wherein the second heat insulating material is arranged in a frame shape covering the outer periphery of the first heat insulating material. Seen from at least one of the planes perpendicular to the sheet thickness direction
The heat transfer suppressing sheet according to claim 1, wherein the second heat insulating material is arranged in a frame shape that covers the outer periphery of the first heat insulating material and in a grid shape that divides the inside of the frame into a plurality of pieces. The heat transfer suppressing sheet according to any one of claims 1 to 7, wherein the second heat insulating material is arranged so as to penetrate from one surface perpendicular to the sheet thickness direction to the other surface. The heat transfer suppressing sheet according to any one of claims 1 to 7, wherein the second heat insulating material is not arranged so as to penetrate from one surface perpendicular to the sheet thickness direction to the other surface. The heat transfer suppressing sheet according to any one of claims 1 to 9, wherein the heat transfer suppressing sheet is covered with a packaging material. Of the pair of surfaces perpendicular to the sheet thickness direction, the surface on the side where the projected area of the second heat insulating material is large in the sheet thickness direction.
When the projected area of the first heat insulating material in the sheet thickness direction is S _1, and the projected area of the second heat insulating material in the sheet thickness direction is S ₂ .
The heat transfer suppressing sheet according to any one of claims 1 to 10, wherein S ₂ / (S ₁ + S ₂ ) is 50% or less. The heat transfer suppressing sheet according to claim 11, wherein S ₂ / (S ₁ + S ₂ ) is 20% or less. The heat transfer suppressing sheet according to claim 12, wherein S ₂ / (S ₁ + S ₂ ) is 5% or less. An assembled battery in which multiple battery cells are connected in series or in parallel.
An assembled battery in which a heat transfer suppressing sheet according to any one of claims 1 to 13 is interposed between the battery cells.

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