JP7651346B2 - Heat transfer suppression sheet for battery pack and battery pack - Google Patents

Description

The present invention relates to a heat transfer suppression sheet for a battery assembly that is suitable for use in a battery assembly that serves as a power source for an electric motor that drives an electric vehicle or hybrid vehicle, and to a battery assembly that uses the heat transfer suppression sheet for a battery assembly.

In recent years, from the perspective of environmental protection, there has been active development of electric vehicles and hybrid vehicles that are driven by electric motors. These electric vehicles and hybrid vehicles are equipped with a battery pack in which multiple battery cells are connected in series or parallel to serve as the power source for the driving electric motor.

These battery cells mainly use lithium-ion secondary batteries, which have higher capacity and power output than lead-acid batteries or nickel-metal hydride batteries. However, if thermal runaway occurs in one battery cell due to an internal short circuit or overcharging (i.e., in the event of an "abnormality"), heat may be transmitted to other adjacent battery cells, potentially causing thermal runaway in the other battery cells.

For example, Patent Document 1 discloses an electricity storage device that can achieve effective insulation between multiple electricity storage elements such as lithium ion secondary batteries. The electricity storage device described in Patent Document 1 has a first plate material and a second plate material having thermal insulation properties arranged between a first electricity storage element and a second electricity storage element adjacent to each other. In addition, a low thermal conductivity layer, which is a layer of a material having a lower thermal conductivity than the first plate material and the second plate material, is formed between the first plate material and the second plate material.

In the energy storage device of Patent Document 1 configured in this manner, the radiant heat from the first energy storage element toward the second energy storage element, or the radiant heat from the second energy storage element toward the first energy storage element, is blocked by the first plate material and the second plate material. In addition, the transfer of heat from one of these two plate materials to the other is suppressed by the low thermal conductivity layer.

JP 2015-211013 A

Incidentally, when a charge/discharge cycle is performed on battery cells assembled into a battery pack (i.e., during "normal use"), in order to fully utilize the charge/discharge performance of the battery cells, it is necessary to maintain the temperature of the battery cell surface below a predetermined value (e.g., below 150°C).
Furthermore, in the event of an abnormal situation in which a battery cell reaches a temperature of, for example, 200° C. or higher, it is necessary to effectively cool the battery cell while suppressing the transfer of heat to adjacent battery cells and preventing thermal runaway.

However, in a structure in which a low thermal conductive layer is provided between heat-insulating plate materials of an electricity storage device as shown in Patent Document 1, the heat generated during the charge/discharge cycle cannot be efficiently diffused to the outside. Also, when thermal runaway occurs in one battery cell, it is difficult to effectively suppress the chain reaction of thermal runaway with only the above structure.
In this way, there has been a demand recently for further improvements in thermal control means that can efficiently diffuse heat generated in battery cells to the outside during normal use, while also being able to suppress a chain reaction of thermal runaway in the event of an abnormality.

The present invention has been made in consideration of the above problems, and aims to provide a heat transfer suppression sheet for a battery assembly, which is used in a battery assembly in which multiple battery cells are connected in series or parallel, and which efficiently diffuses heat generated in the battery cells to the outside of the heat transfer suppression sheet during normal use, and which can prevent a chain reaction of thermal runaway by suppressing the transfer of heat between the battery cells in the event of an abnormality.

The above object of the present invention is achieved by the following configuration [1] relating to a heat transfer suppression sheet for a battery pack.

[1] A heat transfer-suppressing sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel and provided between the battery cells, comprising:
A pair of insulating materials;
At least one highly thermally conductive layer disposed between the pair of thermal insulating materials,
The thermal conductivity of the high thermal conductivity layer is higher than the thermal conductivity of the insulating material, and
the thickness of the highly thermally conductive layer increases toward one end surface of the heat transfer-suppressing sheet,
the highly thermally conductive layer is exposed on the one end surface side.

Further, preferred embodiments of the present invention relating to the heat transfer-suppressing sheet for a battery assembly relate to the following [2] to [7].
[2] The heat transfer-suppressing sheet for a battery assembly according to [1], wherein the highly thermally conductive layer is made of at least one material selected from the group consisting of metal, ceramic, and carbon.

[3] The heat transfer suppressing sheet for a battery pack according to [1] or [2], in which the thickness of the high thermal conductivity layer increases continuously toward the one end surface side.

[4] The heat transfer suppressing sheet for a battery pack according to [1] or [2], in which the thickness of the high thermal conductivity layer increases stepwise toward the one end surface side.

[5] A heat transfer suppressing sheet for a battery pack according to any one of [1] to [4], in which the thickness of the highly thermally conductive layer increases toward the one end surface side of the heat transfer suppressing sheet so that the rate at which the thickness of the highly thermally conductive layer increases.

[6] The heat transfer suppressing sheet for a battery pack described in any one of [1] to [5], wherein the high thermal conductivity layer protrudes from the one end surface.

[7] The heat transfer suppressing sheet for a battery pack according to any one of [1] to [6], wherein the high thermal conductivity layer is not exposed on the other end surface of the heat transfer suppressing sheet that faces the one end surface.

The above object of the present invention is also achieved by the following configuration [8] relating to the battery pack.

[8] A battery case;
A plurality of battery cells housed inside the battery case and connected in series or in parallel;
a heat transfer-suppressing sheet for a battery assembly according to any one of [1] to [7] interposed between the plurality of battery cells; and
a cooling portion disposed between the battery case and the heat transfer-suppressing sheet,
the highly thermally conductive layer is in contact with the cooling portion at the one end surface side.

A preferred embodiment of the present invention relating to the battery pack relates to [9] below.

[9] The high thermal conductive layer has a protruding portion protruding from the one end surface,
The battery pack according to [8], wherein the heat transfer-suppressing sheet is fixed between the battery cells with the protruding portion pressing against the cooling portion.

In the heat transfer-inhibiting sheet for a battery pack of the present invention, the thickness of a highly thermally conductive layer provided between a pair of insulating materials increases toward one end face of the heat transfer-inhibiting sheet, and the highly thermally conductive layer is exposed at the one end face.
Therefore, heat generated from the battery cell and reaching the highly thermally conductive layer through the insulating material is urged in the surface direction of the highly thermally conductive layer (the direction of the surface perpendicular to the thickness direction of the highly thermally conductive layer), and the heat selectively moves to the one end face side and is diffused to the outside of the heat-transfer-suppressing sheet. In addition, the thickness of the highly thermally conductive layer gradually increases toward the one end face side, and the amount of heat that can move through the highly thermally conductive layer increases the closer it is to the one end face side. Therefore, when a large amount of heat is transferred to the highly thermally conductive layer, the heat of the highly thermally conductive layer can be prevented from leaking into the insulating material and being transferred to an adjacent battery cell.
As a result, during normal use, heat generated in the battery cells is efficiently diffused to the outside of the heat transfer suppression sheet, and in the event of an abnormality, the transfer of heat between the battery cells is suppressed, preventing a chain reaction of thermal runaway.

The battery pack of the present invention has the above-mentioned heat transfer suppression sheet interposed between multiple battery cells, so that during normal use, heat generated in the battery cells is efficiently diffused to the outside of the heat transfer suppression sheet, and in the event of an abnormality, the transfer of heat between the battery cells is suppressed, preventing a chain reaction of thermal runaway.

FIG. 1 is a cross-sectional view that illustrates a heat-transfer-suppressing sheet for a battery assembly according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view that illustrates a schematic diagram of a battery assembly to which the heat-transfer-suppressing sheet for a battery assembly according to the first embodiment is applied. FIG. 3 is a cross-sectional view that typically illustrates a heat-transfer-suppressing sheet for a battery assembly according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to a third embodiment of the present invention. FIG. 5 is a cross-sectional view that illustrates a schematic diagram of a battery assembly to which a heat-transfer-suppressing sheet for a battery assembly according to a third embodiment is applied. FIG. 6 is a cross-sectional view that typically shows a heat transfer-suppressing sheet for a battery assembly according to a fourth embodiment of the present invention. FIG. 7 is a cross-sectional view that illustrates a heat transfer-suppressing sheet for a battery assembly according to a fifth embodiment of the present invention. FIG. 8 is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to a sixth embodiment of the present invention.

The inventors have conducted extensive research to provide a heat-transfer suppression sheet for a battery pack that can efficiently diffuse heat generated from the battery cells to the outside of the heat-transfer suppression sheet during normal use, and can also suppress the transfer of heat between the battery cells even in abnormal situations where a large amount of heat is generated, thereby preventing a chain reaction of thermal runaway.

As a result, the inventors discovered that the above problem can be solved by configuring a heat transfer inhibitor sheet provided between battery cells such that the thickness of a highly thermally conductive layer provided between insulating materials increases toward one end face of the heat transfer inhibitor sheet, and further by configuring the highly thermally conductive layer to be exposed at the one end face.
In other words, when heat reaches the highly thermally conductive layer, the highly thermally conductive layer conducts the heat in the planar direction of the highly thermally conductive layer (the direction of a plane perpendicular to the thickness direction of the highly thermally conductive layer) and selectively moves the heat to the above-mentioned one end face side, thereby allowing the heat to be efficiently diffused outside the heat transfer suppression sheet.

The following describes in detail an embodiment of the present invention with reference to the drawings. Note that the present invention is not limited to the embodiment described below, and can be modified as desired without departing from the spirit of the present invention.

[1. Heat transfer suppression sheet for battery pack]
Hereinafter, the heat-transfer-suppressing sheet for a battery assembly according to the present invention will be described in order from the first to sixth embodiments. After that, the heat insulating material, the highly thermally conductive layer, and the like that constitute the heat-transfer-suppressing sheet for a battery assembly according to the present embodiments will be described. Furthermore, a method for manufacturing the heat-transfer-suppressing sheet for a battery assembly according to the present embodiments will be described.

First Embodiment
1 is a cross-sectional view that typically illustrates a heat-transfer-suppressing sheet for a battery assembly according to a first embodiment of the present invention. Hereinafter, the heat-transfer-suppressing sheet for a battery assembly may be simply referred to as the "heat-transfer-suppressing sheet."
The heat transfer-suppressing sheet 10 for a battery assembly according to the first embodiment includes thermal insulators 11a and 11b and a highly thermally conductive layer 12a provided between the thermal insulators 11a and 11b. The highly thermally conductive layer 12a has a higher thermal conductivity than the thermal insulators 11a and 11b, and the highly thermally conductive layer 12a becomes continuously thicker toward one end surface 10a of the heat transfer-suppressing sheet 10.

Figure 2 is a cross-sectional view showing a schematic diagram of a battery pack to which the heat transfer suppression sheet for a battery pack according to the first embodiment is applied. The battery pack 100 includes a battery case 30, a plurality of battery cells 20a, 20b, and 20c housed inside the battery case 30, a heat transfer suppression sheet 10 interposed between the battery cells 20a and 20b and between the battery cells 20b and 20c, and a cooling unit 40 disposed between the battery cells 20a, 20b, and 20c and the heat transfer suppression sheet 10 and the battery case 30.

The heat transfer suppression sheet 10 is arranged so that one end surface 10a of the sheet 10 is in contact with the cooling section 40. The battery cells 20a, 20b, and 20c are connected in series or parallel by bus bars (not shown) or the like.

As shown in FIG. 2, the cooling unit 40 does not need to be disposed on the entire bottom surface of the battery case 30, but only needs to be disposed between the heat transfer suppression sheet 10 and the battery case 30. The battery cells 20a, 20b, and 20c are preferably, for example, lithium ion secondary batteries, but are not limited thereto and may also be applied to other secondary batteries.

In the first embodiment configured in this manner, when heat generated, for example, from the battery cell 20a is transmitted to the high thermal conductivity layer 12a through the insulating material 11a, the heat of the high thermal conductivity layer 12a moves quickly through the high thermal conductivity layer 12a along its surface direction, because the high thermal conductivity of the high thermal conductivity layer 12a is high.
Here, when the thickness of high thermal conductivity layer 12a is constant, if a large amount of heat is transferred to high thermal conductivity layer 12a, some of the heat in high thermal conductivity layer 12a leaks into insulation material 11a or insulation material 11b as it moves in the planar direction, and is transferred to the adjacent battery cell 20b.

On the other hand, in this embodiment, the thickness of the high thermal conductivity layer 12a gradually increases toward one end face 10a of the heat transfer suppression sheet 10, and the closer to the one end face 10a, the greater the amount of heat that can move through the high thermal conductivity layer 12a, so that heat is selectively promoted in the planar direction toward the one end face 10a.
Therefore, when a cooling unit 40 is provided on one end surface 10a of the heat-transfer-suppressing sheet 10 where the high thermal conductivity layer 12a is thick, the heat of the high thermal conductivity layer 12a is efficiently removed by the cooling unit 40 arranged in contact with the high thermal conductivity layer 12a, and is diffused to the outside of the heat-transfer-suppressing sheet 10. As a result, the heat that reaches the high thermal conductivity layer 12a can be suppressed from being transmitted to the adjacent battery cell through the insulating material 11b.
The "plane direction" of the highly thermally conductive layer 12a refers to the direction of the plane perpendicular to the thickness direction of the highly thermally conductive layer 12a (the left-right direction in FIG. 1).

In this manner, in this embodiment, since the highly thermally conductive layer 12a having a specific shape is disposed between the insulating material 11a and the insulating material 11b, the heat that reaches the highly thermally conductive layer 12a can be selectively propagated in one direction. As a result, when heat is generated from a certain battery cell, the heat is efficiently diffused to the outside of the heat transfer suppression sheet during normal use, and the propagation of heat to adjacent battery cells is suppressed during an abnormality, preventing a chain reaction of thermal runaway.

Second Embodiment
Fig. 3 is a cross-sectional view that shows a schematic diagram of a heat-transfer-suppressing sheet for a battery assembly according to a second embodiment of the present invention. In the second to sixth embodiments shown in Figs. 3 to 8, the same or equivalent parts as those in the first embodiment are denoted by the same reference numerals in the drawings, and their description will be omitted or simplified. In addition, since the second embodiment can be used in place of the heat-transfer-suppressing sheet 10 described in the battery assembly 100 shown in Fig. 2, the effects and the like will be described assuming that the heat-transfer-suppressing sheet according to the second embodiment is applied to the battery assembly 100.

As shown in FIG. 3, the heat transfer suppressing sheet 15 for a battery pack according to the second embodiment has heat insulating materials 11a and 11b and a highly thermally conductive layer 12b provided between the heat insulating materials 11a and 11b. As with the highly thermally conductive layer 12a of the first embodiment, the highly thermally conductive layer 12b is configured to continuously become thicker toward the one end surface 15a of the heat transfer suppressing sheet 15. However, in this embodiment, the highly thermally conductive layer 12b is extremely thin near the other end surface 15b opposite the one end surface 15a, and the rate at which the thickness of the highly thermally conductive layer 12b becomes thicker increases as it approaches the one end surface 15a.

The second embodiment configured in this manner also provides the same effects as the first embodiment. In addition, in the second embodiment, the rate of increase in the thickness of the high thermal conductivity layer 12b increases from the other end surface 15b side toward the one end surface 15a side, so that the heat insulating effect of the insulating materials 11a, 11b is high near the other end surface 15b, where the heat dissipation effect is small. Therefore, when heat is generated from the battery cell 20a and reaches the high thermal conductivity layer 12b near the other end surface 15b, it is possible to prevent the heat from flowing into the battery cell 20b side via the insulating material 11b.

Third Embodiment
Fig. 4 is a cross-sectional view showing a heat transfer-suppressing sheet for a battery assembly according to a third embodiment of the present invention, and Fig. 5 is a cross-sectional view showing a battery assembly to which the heat transfer-suppressing sheet for a battery assembly according to the third embodiment is applied.

4, the heat-transfer-suppressing sheet 16 for a battery assembly according to the third embodiment includes thermal insulators 11a and 11b and a highly thermally conductive layer 12c provided between the thermal insulators 11a and 11b. As in the first embodiment, the highly thermally conductive layer 12c becomes continuously thicker toward one end surface 16a of the heat-transfer-suppressing sheet 16. However, the highly thermally conductive layer 12c in the third embodiment includes a protruding portion 22c that protrudes from the one end surface 16a of the heat-transfer-suppressing sheet 16 toward the outside of the battery assembly 100 beyond the thermal insulators 11a and 11b.
As shown in FIG. 5, the heat-transfer-suppressing sheet 16 is fixed between the battery cells with the protruding portion 22c of the highly thermally conductive layer 12c pressing against the cooling portion 40.

The third embodiment configured in this manner also provides the same effect as the first embodiment. In the third embodiment, the highly thermally conductive layer 12c protrudes toward the outside of the battery pack 100 beyond the insulating materials 11a and 11b on one end surface 16a side of the heat transfer suppression sheet 16, and the protruding portion 22c presses the cooling portion 40. Therefore, the protruding portion 22c is covered by the cooling portion 40, and the contact area between the highly thermally conductive layer 12c and the cooling portion 40 increases, so that the highly thermally conductive layer 12c can be cooled more efficiently.

Fourth Embodiment
Fig. 6 is a cross-sectional view showing a schematic diagram of a heat-transfer-suppressing sheet for a battery assembly according to a fourth embodiment of the present invention. Since the fourth to sixth embodiments described below can be used in place of the heat-transfer-suppressing sheet 10 shown in Fig. 2 for the battery assembly 100, the effects and the like will be described assuming that the heat-transfer-suppressing sheets according to the fourth to sixth embodiments are applied to the battery assembly 100.

As shown in Fig. 6, the heat transfer suppressing sheet 17 for a battery pack according to the fourth embodiment has insulating materials 11a and 11b, and a highly thermally conductive layer 12d provided between the insulating materials 11a and 11b. As shown in Fig. 6, the heat transfer suppressing sheet 17 according to the fourth embodiment is configured such that the highly thermally conductive layer 12d is not exposed to the outside of the battery pack 100 on the other end surface 17b side opposite the one end surface 17a side of the heat transfer suppressing sheet 17.

The fourth embodiment configured in this manner also provides the same effects as the first embodiment. In addition, a bus bar is provided on the other end surface 17b side of the heat transfer suppression sheet 17 to connect the terminals of the battery cells to each other. In this embodiment, since the insulating material 11a and the insulating material 11b are provided between the high thermal conductivity layer 12d and the bus bar, good insulation can be achieved between the high thermal conductivity layer 12d and the bus bar.

Fifth embodiment
FIG. 7 is a cross-sectional view that illustrates a heat transfer-suppressing sheet for a battery assembly according to a fifth embodiment of the present invention.
As shown in Fig. 7, a heat-transfer-inhibiting sheet 18 for a battery assembly according to the fifth embodiment has thermal insulators 11a and 11b and a highly thermally conductive layer 12e provided between the thermal insulators 11a and 11b. As shown in Fig. 7, in the heat-transfer-inhibiting sheet 18 according to the fifth embodiment, the highly thermally conductive layer 12e is exposed on the other end surface 18b of the heat-transfer-inhibiting sheet 18, and the highly thermally conductive layer 12e also has a predetermined thickness on the other end surface 18b side. Therefore, when cooling by an air-cooling method is provided, heat is dissipated from the end surface 18b side, and the highly thermally conductive layer 12c can be cooled more efficiently.

The fifth embodiment configured in this manner also provides the same effects as the first embodiment. Furthermore, since the highly thermally conductive layer 12e having a predetermined thickness is present over the entire area from one end surface 18a to the other end surface 18b of the heat-transfer-suppressing sheet 18, heat generated from the battery cells can easily reach the highly thermally conductive layer 12e. Therefore, the heat can be diffused to the outside of the heat-transfer-suppressing sheet 18 more efficiently. Furthermore, since the highly thermally conductive layer 12e has a predetermined thickness over the entire area from one end surface 18a to the other end surface 18b of the heat-transfer-suppressing sheet 18, the overall strength of the heat-transfer-suppressing sheet 18 can be improved.
From the viewpoint of transferring heat in the planar direction of the highly thermally conductive layer 12e and improving the strength of the entire heat-transfer-suppressing sheet 18, the thickness of the highly thermally conductive layer 12e on the other end surface 18b side is preferably 0.5% to 50% of the thickness of the sheet, and more preferably 1% to 25%. The thickness of the highly thermally conductive layer 12e on the other end surface 18b side is preferably 0.005 to 1 mm, and more preferably 0.01 to 0.5 mm.

Sixth embodiment
FIG. 8 is a cross-sectional view that typically shows a heat-transfer-suppressing sheet for a battery assembly according to a sixth embodiment of the present invention.
8, a heat-transfer-suppressing sheet 19 for a battery assembly according to the sixth embodiment includes thermal insulators 11a and 11b and a highly thermally conductive layer 12f provided between the thermal insulators 11a and 11b. In the heat-transfer-suppressing sheet 19 for a battery assembly according to the sixth embodiment, the highly thermally conductive layer 12f becomes thicker in a stepped manner toward one end surface 19a of the heat-transfer-suppressing sheet 19.

The sixth embodiment thus configured also provides the same effects as the first embodiment. In addition, the sixth embodiment can be formed by stacking a plurality of sheets of different sizes, as shown in Fig. 8. Therefore, compared to the first to fifth embodiments, the high thermal conductive layer 12f configured to become thicker toward the one end surface 19a can be easily produced.
Furthermore, in the heat transfer-suppressing sheet 19 for a battery pack according to the sixth embodiment, the highly thermally conductive layer 12f is configured to become thicker in a stepped manner toward the one end surface 19a side, and therefore a space 21 may be formed between the highly thermally conductive layer 12f, which becomes thicker in a stepped manner, and the insulating material 11a or the insulating material 11b. Therefore, air is retained in the space 21, and the insulating effect between adjacent battery cells can be further improved.

The high thermal conductivity layer 12f, which thickens in a stepped manner toward one end surface of the heat transfer suppression sheet, may be formed in this shape from a single sheet of material such as metal.

Next, we will explain in detail the highly thermally conductive layer, the insulating material, and the cooling section that make up the heat transfer suppression sheet for a battery pack according to the present invention.

(High thermal conductivity layer)
The highly thermally conductive layer used in the heat-transfer-inhibiting sheet for a battery pack according to this embodiment has the effect of suppressing the transfer of radiative heat to adjacent battery cells, and the effect of moving heat that reaches the highly thermally conductive layer in the direction of one end face of the heat-transfer-inhibiting sheet and diffusing it to the outside of the heat-transfer-inhibiting sheet.

As the high thermal conductivity layer having a thermal conductivity higher than that of the insulating material, it is preferable to select at least one material selected from metal, ceramic, and carbon. Specifically, the metal can be selected from aluminum or aluminum alloy, stainless steel, copper or copper alloy, silver or silver alloy, nickel or nickel alloy, titanium or titanium alloy, etc. Furthermore, the ceramic can be selected from silicon carbide, aluminum nitride, silicon nitride, boron nitride, titanium nitride, etc. Furthermore, the carbon can be selected from carbon fiber, carbon nanotube, diamond, graphite, etc.

The high thermal conductivity layer may be formed by laminating a plurality of metal layers made of different kinds of the above metals. Examples of such high thermal conductivity layers include an aluminum/copper/aluminum composite layer, an aluminum/silver/aluminum composite layer, a nickel/stainless steel/nickel composite layer, and a silver/stainless steel/silver composite layer. The above composite layer can be obtained by forming surface layers on both sides of a central base layer by a method such as wet plating or vapor deposition.
The high thermal conductivity layer may also be made of a combination of different types of materials selected from the above metals, ceramics, and carbon.

The thermal conductivity of the high thermal conductive layer is 5 to 450 (W/m·K), which is sufficiently greater than the thermal conductivity of the insulating material described below (e.g., 0.05 (W/m·K)), and therefore heat that reaches the high thermal conductive layer can be efficiently diffused to the outside of the heat transfer suppression sheet. In terms of specific thermal conductivity compared to the insulating material, the thermal conductivity of the high thermal conductive layer is preferably 10 times or more, and more preferably 100 times or more, the thermal conductivity of the insulating material.

The thermal conductivity of the high thermal conductive layer can be calculated by a laser flash method and a differential scanning calorimetry (DSC) method, as shown in the following (1) to (3).
(1) Thermal diffusivity is measured in accordance with the "Method for measuring thermal diffusivity of metals by laser flash method" described in JIS H 7801.
(2) The specific heat capacity is measured in accordance with "Method for measuring specific heat capacity of long fiber reinforced ceramic composite material by differential scanning calorimetry" described in JIS R 1672.
(3) Calculate the thermal conductivity based on the values obtained in (1) and (2).

In order to fully obtain the heat diffusion effect by conductive heat transfer, the thickness of the highly thermally conductive layer at its thinnest point preferably exceeds 0 μm, more preferably is 10 μm or more, even more preferably is 20 μm or more, even more preferably is 30 μm or more, and particularly preferably is 50 μm or more.
On the other hand, from the standpoint of the overall thickness of the heat-transfer-suppressing sheet, the high-thermal-conductivity layer preferably has a thickness of 300 μm or less at its thickest point, and more preferably has a thickness of 200 μm or less.
Furthermore, as described above, the highly thermally conductive layer may be a single layer or a laminate of multiple layers made of various materials. When layers made of the same material are laminated to form the highly thermally conductive layer, the same effect can be obtained as long as the total thickness of the multiple layers is the same as the thickness of the highly thermally conductive layer made of a single layer. Therefore, even when the highly thermally conductive layer is made of multiple layers, it is preferable that the total thickness is within the above range.

(Thermal insulation)
The heat insulating material used in the heat transfer suppressing sheet for a battery pack according to the present embodiment is not particularly limited as long as it has a heat insulating effect. Thermal conductivity can be cited as an index showing the heat insulating effect, and in the present embodiment, the heat conductivity of the heat insulating material is preferably less than 1 (W/m·K), more preferably less than 0.5 (W/m·K), and even more preferably less than 0.2 (W/m·K). Furthermore, the heat conductivity of the heat insulating material is more preferably less than 0.1 (W/m·K), more preferably less than 0.05 (W/m·K), and particularly preferably less than 0.02 (W/m·K).
As such a heat insulating material, for example, a material containing at least one selected from inorganic fibers, organic fibers, inorganic particles, and organic particles can be used.

The thermal conductivity of the insulating material can be measured in accordance with the "Test method for thermal conductivity of refractories" described in JIS R 2251.

As the inorganic fiber, alumina fiber, carbon fiber, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, aerogel composite material, and the like can be used.
As the organic fiber, cellulose fiber or the like can be used.
These fibers may be used alone or in combination of two or more kinds.

As inorganic particles, mica, microporous particles, hollow silica particles, thermally expandable inorganic materials, and aerogels can be used.
Examples of the thermally expandable inorganic material include vermiculite, bentonite, mica, and perlite.
As the organic particles, hollow polystyrene particles or the like can be used.

Among these insulating materials, alumina fiber, glass fiber, aerogel composites, etc. can be preferably used.

<Thickness of heat transfer suppression sheet>
In this embodiment, the thickness of the heat-transfer-suppressing sheet is not particularly limited, but is preferably in the range of 0.05 to 6 mm. If the thickness of the heat-transfer-suppressing sheet is less than 0.05 mm, the heat-transfer-suppressing sheet cannot be provided with sufficient mechanical strength. On the other hand, if the thickness of the heat-transfer-suppressing sheet exceeds 6 mm, the molding of the heat-transfer-suppressing sheet itself may become difficult.

Next, we will explain the manufacturing method of the heat transfer suppression sheet for the battery pack according to this embodiment.

<Method of Manufacturing Heat Transfer-Suppressing Sheet>
The heat transfer-suppressing sheet according to the present embodiment can be obtained, for example, by disposing a highly thermally conductive layer having the above-mentioned specific shape between a pair of heat insulating materials. These may or may not be bonded together. When they are bonded together, for example, a method of fixing the peripheral portions of the laminated sheets by adhesion or welding can be used.

The heat transfer suppression sheet according to this embodiment can be easily bent depending on the type and thickness of the highly thermally conductive layer and the insulating material. Therefore, it can be adapted to any shape without being affected by the shape of the battery cells 20a, 20b, 20c and the battery case 30. Specifically, it can be applied to cylindrical batteries, flat batteries, etc. in addition to square batteries.

In addition, as shown in FIG. 2, the heat transfer suppression sheet according to this embodiment does not necessarily need to be provided with a cooling section 40. For example, the space inside the battery case 30 or the battery case 30 can be used as the cooling section to diffuse heat from the highly thermally conductive layer 12a heated by the heated battery cell to the space inside the battery case 30 or the battery case 30, which has a lower temperature.

[2. Battery pack]
The battery pack according to this embodiment is a battery pack in which a plurality of battery cells are connected in series or parallel, and a heat-transfer-suppressing sheet for a battery pack according to this embodiment is interposed between the battery cells. Specifically, for example, as shown in Fig. 2, a battery pack 100 is configured by arranging a plurality of battery cells 20a, 20b, 20c side by side, connecting them in series or parallel, and housing them in a battery case 30, and a heat-transfer-suppressing sheet 10 is interposed between the battery cells 20a, 20b, 20c. A cooling unit 40 is disposed between the battery case 30 and the heat-transfer-suppressing sheet 10, and the highly thermally conductive layer 12a of the heat-transfer-suppressing sheet 10 is disposed so as to be in contact with the cooling unit 40.

In this battery pack 100, the heat-transfer-suppressing sheet 10 is interposed between each of the battery cells 20a, 20b, and 20c, and during normal use, the heat-transfer-suppressing sheet 10 selectively transfers heat to one end of the heat-transfer-suppressing sheet, where the heat is diffused to the outside of the heat-transfer-suppressing sheet, thereby suppressing the transfer of heat between each of the battery cells 20a, 20b, and 20c.
Furthermore, even if one of the multiple battery cells 20a, 20b, and 20c experiences thermal runaway, becomes too hot, expands, or catches fire, the presence of the heat-transfer-suppressing sheet 10 according to this embodiment suppresses the transfer of heat between the battery cells 20a, 20b, and 20c, preventing a chain reaction of thermal runaway. This makes it possible to minimize adverse effects on the other battery cells.

(Cooling section)
In the battery pack according to this embodiment, examples of the cooling section include those configured to circulate a gas or liquid refrigerant, those in which the refrigerant is sealed, cooling plates, heat dissipation sheets, heat dissipation gels, and the like; however, in the present invention, there are no particular limitations on the structure and material of the cooling section.

10, 15, 16, 17, 18, 19 Heat transfer suppressing sheet for battery pack 10a, 15a, 16a, 17a, 18a, 19a One end surface 11a, 11b Heat insulating material 12a, 12b, 12c, 12d, 12e, 12f High thermal conductivity layer 20a, 20b, 20c Battery cell 21 Space 30 Battery case 40 Cooling section 100 Battery pack

Claims (9)

A heat transfer-suppressing sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the heat transfer-suppressing sheet being provided between the battery cells,
A pair of insulating materials;
At least one highly thermally conductive layer disposed between the pair of thermal insulating materials,
The thermal conductivity of the high thermal conductivity layer is higher than the thermal conductivity of the insulating material, and
the thickness of the highly thermally conductive layer increases toward one end surface of the heat transfer-suppressing sheet,
the highly thermally conductive layer is exposed on the one end surface side. The heat transfer suppression sheet for a battery pack according to claim 1, wherein the high thermal conductivity layer is made of at least one material selected from metal, ceramic, and carbon. The heat transfer suppression sheet for a battery pack according to claim 1 or 2, wherein the thickness of the high thermal conductivity layer increases continuously toward the one end surface side. The heat transfer suppression sheet for a battery pack according to claim 1 or 2, wherein the thickness of the high thermal conductivity layer increases stepwise toward the one end surface side. The heat transfer suppressing sheet for a battery pack according to any one of claims 1 to 4, wherein the thickness of the high thermal conductivity layer increases toward the one end surface side of the heat transfer suppressing sheet so that the rate at which the thickness of the high thermal conductivity layer increases. The heat transfer suppressing sheet for a battery pack according to any one of claims 1 to 5, wherein the high thermal conductivity layer protrudes from the one end surface. The heat transfer suppressing sheet for a battery pack according to any one of claims 1 to 6, wherein the high thermal conductivity layer is not exposed on the other end surface of the heat transfer suppressing sheet that faces the one end surface. A battery case;
A plurality of battery cells housed inside the battery case and connected in series or in parallel;
a heat transfer-suppressing sheet for a battery assembly according to any one of claims 1 to 7, which is interposed between the plurality of battery cells;
a cooling portion disposed between the battery case and the heat transfer-suppressing sheet,
the highly thermally conductive layer is in contact with the cooling portion at the one end surface side. the high thermal conductivity layer has a protruding portion protruding from the one end surface,
The battery pack according to claim 8 , wherein the heat transfer-suppressing sheet is fixed between the battery cells with the protruding portion pressing against the cooling portion.

Images