JP7670525B2 - Thermal control sheet for battery pack and battery pack - Google Patents

Description

The present invention relates to a thermal control sheet for a battery pack suitable for use in a battery pack that serves as a power source for an electric motor that drives an electric vehicle or hybrid vehicle, and to a battery pack using the thermal control sheet for a battery pack.

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 first and second plates with thermal insulation disposed between adjacent first and second electricity storage elements. In addition, a low thermal conductivity layer, for example a layer of air, that has a lower thermal conductivity than the first and second plates is formed between the first and second plates.

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 a portion of 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, since the above-mentioned energy storage device only has a low thermal conductive layer between the first and second energy storage elements, the heat generated during the charge/discharge cycle cannot be efficiently diffused to the outside. Furthermore, when thermal runaway occurs in one battery cell, it is difficult to effectively suppress the chain reaction of thermal runaway using only the above-mentioned insulating material.
In this way, there has been a demand in recent years for further improvements in heat control means that can efficiently diffuse generated heat to the outside and suppress a chain reaction of thermal runaway.

The present invention has been made in consideration of the above problems, and aims to provide a thermal control sheet for a battery assembly and a battery assembly that can be used in a battery assembly in which multiple battery cells are connected in series or parallel, and that can diffuse heat generated during normal use to the outside and suppress the propagation of heat, as well as suppress the propagation of heat between battery cells in the event of an abnormality, efficiently cool the battery cells, and prevent a chain reaction of thermal runaway.

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

[1] A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the sheet being interposed between the battery cells,
A plurality of heat dissipation layers;
a spacer disposed between the adjacent heat dissipation layers, and a gas flow path is formed in an area between the adjacent heat dissipation layers excluding the spacer,
The thermal control sheet for a battery pack, wherein the heat dissipation layer has a thermal conduction layer having a thermal conductivity of 5 (W/m·K) or more.

Furthermore, preferred embodiments of the present invention relating to the thermal control sheet for a battery pack relate to the following [2] to [10].

[2] The thermal control sheet for a battery pack described in [1], characterized in that the thermally conductive layer is made of at least one material selected from metal, titanium nitride, and graphite.

[3] The thermal control sheet for a battery pack according to [2], characterized in that the thermally conductive layer is made of at least one material selected from aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, titanium or a titanium alloy, titanium nitride, and graphite.

[4] The thermal control sheet for a battery pack according to any one of [1] to [3], characterized in that the spacer contains at least one material selected from silicon dioxide, silica sol, ceramic fiber, glass, and mica.

[5] The thermal control sheet for a battery pack described in any one of [1] to [3], characterized in that the spacer is an adhesive bonded between adjacent heat dissipation layers.

[6] The thermal control sheet for a battery pack described in any one of [1] to [5], characterized in that the emissivity of the heat dissipation layer is 0.5 or less.

[7] The thermal control sheet for a battery pack described in any one of [1] to [6], characterized in that the heat dissipation layer is a composite layer in which the thermally conductive layer and a layer made of a material selected from metal, ceramic, and graphite are laminated.

[8] A thermal control sheet for a battery pack according to any one of [1] to [7], characterized in that a heat insulating material is provided at a position in contact with the battery cells.

[9] The thermal control sheet for a battery pack according to [8], characterized in that the insulating material contains at least one selected from inorganic fibers, organic fibers, inorganic particles, and organic particles.

[10] The thermal control sheet for a battery pack according to [9], characterized in that the heat insulating material contains at least one selected from alumina fiber, carbon fiber, mica, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, aerogel composite, microporous particles, hollow silica particles, thermally expandable inorganic material, and aerogel.

The above object of the present invention is also achieved by the following configuration [11] relating to the battery pack.

[11] A battery case;
A plurality of battery cells housed inside the battery case and connected in series or parallel;
and a thermal control sheet for a battery pack according to any one of [1] to [10] interposed between the plurality of battery cells.

The thermal control sheet for battery packs of the present invention is a thermal control sheet used in battery packs in which multiple battery cells are connected in series or parallel, and the heat dissipation layer can suppress radiative heat transfer from the battery cells, while diffusing heat that reaches the heat dissipation layer by conductive heat transfer. In addition, gas flow paths are formed between the heat dissipation layers, and heated gas moves to the outside of the thermal control sheet through the flow paths, promoting heat dissipation, thereby suppressing convective heat transfer from battery cell to battery cell. Furthermore, at this time, low-temperature gas flows into the flow paths, allowing the battery cells to be efficiently cooled. As a result, the heat generated from one battery cell can be suppressed from propagating to an adjacent battery cell, preventing a chain reaction of thermal runaway.

The battery pack of the present invention has the above-mentioned thermal control sheet interposed between multiple battery cells, which allows for efficient heat diffusion during normal use and in the event of an abnormality, while also suppressing the transfer of heat between battery cells, preventing a chain reaction of thermal runaway.

FIG. 1 is a cross-sectional view that illustrates a thermal control sheet for a battery pack according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view that illustrates a schematic diagram of a battery pack to which the thermal control sheet for a battery pack according to the first embodiment is applied. FIG. 3 is a cross-sectional view that illustrates a thermal control sheet for a battery pack according to a second embodiment of the present invention. FIG. 4 is a cross-sectional view that illustrates a thermal control sheet for a battery pack according to a third embodiment of the present invention. FIG. 5 is a cross-sectional view that illustrates a method for evaluating the effect of thermal control. FIG. 6 is a perspective view showing the size of the thermal control sheet used in this embodiment.

The inventors have conducted extensive research to provide a thermal control sheet for a battery pack that can efficiently diffuse heat generated from battery cells to the outside even during normal use when relatively low-temperature heat is generated, while suppressing the transfer of heat between battery cells during abnormal conditions when high-temperature heat is generated.

As a result, the inventors discovered that the above problem can be solved by forming a gas flow path between adjacent heat dissipation layers using spacers disposed between adjacent heat dissipation layers in a thermal control sheet for a battery pack interposed between multiple battery cells.

In other words, during normal use when relatively low-temperature heat is generated, the heat dissipation layer has the effect of suppressing radiative heat transfer from the battery cells, and since the heat dissipation layer has a thermally conductive layer, it has the effect of diffusing the heat that reaches the thermally conductive layer by conductive heat transfer. In addition, the space between adjacent heat dissipation layers acts as a thermal insulation layer, providing thermal insulation.
In addition, when the temperature of a battery cell rises due to an abnormality, the heat dissipation layer can suppress the radiative heat transfer from the battery cell and diffuse the heat that reaches the thermal conduction layer by conductive heat transfer, as in normal use. Furthermore, since spacers are disposed between adjacent heat dissipation layers and a gas flow path is formed in the area excluding the spacers, when the heat dissipation layer becomes hot and the temperature of the gas between the heat dissipation layers rises, the gas moves to the outside of the thermal control sheet through the flow path, promoting heat dissipation. Therefore, convective heat transfer from one heat dissipation layer to the other heat dissipation layer is suppressed. At the same time, low-temperature gas existing outside the thermal control sheet flows into the surface of the battery cell through the flow path, so that the battery cell can be efficiently cooled.

In this way, by utilizing the multiple heat dissipation layers and the gas flow paths formed between these multiple heat dissipation layers, radiative heat transfer and convective heat transfer in the thickness direction of the thermal control sheet are suppressed, and heat is diffused by conductive heat transfer. In the event that a battery cell becomes too hot, heat transfer is suppressed before it reaches an adjacent battery cell, and the heat can be diffused to the outside, preventing a chain reaction of thermal runaway.

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 gist of the present invention.

[1. Thermal control sheet for battery packs]
Hereinafter, the thermal control sheet for a battery pack according to the embodiment of the present invention will be described in order from the first to third embodiments. After that, the heat dissipation layer, spacer, etc. constituting the thermal control sheet for a battery pack according to the present embodiment will be described. Furthermore, the manufacturing method of the thermal control sheet for a battery pack according to the present embodiment will be described.

First Embodiment
1 is a cross-sectional view showing a schematic diagram of a thermal control sheet for a battery assembly according to a first embodiment of the present invention. Hereinafter, the thermal control sheet for a battery assembly may be simply referred to as a "thermal control sheet."
The thermal control sheet 10 for a battery assembly according to the first embodiment includes a pair of heat dissipation layers 11a and 11b, and a spacer 12 disposed between the heat dissipation layers 11a and 11b. Therefore, a gas flow path 18 is formed between the heat dissipation layers 11a and 11b in an area other than the spacer 12.
In the first embodiment, the heat dissipation layers 11a and 11b are, for example, stainless steel plates and function as heat conduction layers.

2 is a cross-sectional view showing a schematic diagram of a battery pack to which the thermal control 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 stored inside the battery case 30, and a thermal control sheet 10 interposed between the battery cells 20a and 20b and between the battery cells 20b and 20c. The plurality of battery cells 20a, 20b, and 20c are connected in series or in parallel by bus bars (not shown) or the like.
The battery cells 20a, 20b, and 20c are preferably, for example, lithium ion secondary batteries, but are not limited thereto and may be other secondary batteries.

In a typical conventional battery pack, a sheet disposed between a plurality of battery cells has a heat insulating material disposed on the surface closest to the battery cells.
In contrast, in the thermal control sheet 10 of the first embodiment, the heat dissipation layers 11a, 11b made of stainless steel are arranged so as to be in contact with the battery cells 20a, 20b, 20c, and the emissivity of stainless steel is lower than the emissivity (e.g., 0.8) of commonly used insulating materials.

In the first embodiment configured as described above, for example, when the temperature of the battery cell 20a rises, the heat dissipation layer 11a provided at a position in contact with the battery cell 20a is made of stainless steel and has a low emissivity of, for example, 0.2, so that it is possible to suppress the radiative heat transfer to the heat dissipation layer 11b side. In addition, since the heat dissipation layer 11a has a thermal conductivity of, for example, 16 (W/m·K), a part of the heat propagated to the heat dissipation layer 11a is propagated in the surface direction of the heat dissipation layer 11a and diffused to the outside of the thermal control sheet 10. In this way, the amount of heat generated from the battery cell 20a is reduced through the heat dissipation layer 11a, and the heat transfer to the heat dissipation layer 11b side is suppressed.
The planar direction of the heat dissipation layers 11a and 11b refers to the direction of the plane perpendicular to the thickness direction of the heat dissipation layers 11a and 11b.

Furthermore, during normal use when relatively low-temperature heat is generated, when the temperature of the battery cell 20a rises, the temperature of the heat dissipation layer 11a also rises. However, since air, for example, is present in the flow path 18 between the heat dissipation layer 11a and the heat dissipation layer 11b and the thermal conductivity of air is extremely low, for example, about 0.02 (W/m·K), the space between the heat dissipation layer 11a and the heat dissipation layer 11b functions as a thermal insulating layer 15.
In addition, in the event of an abnormality, if the temperature of the battery cell 20a rises further, the temperature of the heat dissipation layer 11a also rises and the gas in the flow path 18 is heated. However, since the heated gas is released to the outside of the thermal control sheet 10 via the flow path 18, convective heat transfer from the heat dissipation layer 11a to the heat dissipation layer 11b is suppressed.
Furthermore, as the heated gas moves, low-temperature gas that was present in other areas flows into the flow path 18, thereby cooling the heat dissipation layer 11a, and as a result, the battery cell 20a can be efficiently cooled.

Some of the heat then reaches the heat dissipation layer 11b, but like the heat dissipation layer 11a, the heat dissipation layer 11b can also suppress radiative heat transfer to the battery cell 20b side. In addition, because heat is propagated in the surface direction of the heat dissipation layer 11b by conductive heat transfer, the heat that reaches the heat dissipation layer 11b is diffused to the outside of the thermal control sheet 10.

In this way, by arranging the battery cell 20a and the battery cell 20b via the thermal control sheet 10, during normal use, the presence of the heat dissipation layers 11a and 11b suppresses conductive heat transfer to the battery cell 20b side, allowing the heat to be diffused and suppressing radiative heat transfer. In addition, the flow path 18 of the thermal control sheet 10 functions as a heat insulating layer, providing good thermal insulation. Furthermore, in the event of an abnormality, when high heat is generated from the battery cell 20a, the effect of the heat dissipation layer can be obtained as in normal use, and convective heat transfer from the heat dissipation layer 11a to the heat dissipation layer 11b is suppressed, so that the propagation of heat between the battery cells can be suppressed and a chain reaction of thermal runaway can be prevented.

The thermal control sheet 10 is configured symmetrically in the thickness direction with respect to the insulating layer 15 (a layer configured of the spacers 12 and the gas flow paths 18). Therefore, even if heat is generated from the battery cell 20b, this heat is gradually reduced toward the battery cell 20a by passing through the heat dissipation layer 11b, the insulating layer 15, and the heat dissipation layer 11a in this order, and the propagation of heat to the battery cell 20a can be suppressed.
Similarly, the heat generated from battery cell 20b is gradually reduced by passing through heat dissipation layer 11a, insulating layer 15, and heat dissipation layer 11b, in that order, toward battery cell 20c, thereby suppressing the transmission of heat to battery cell 20c.

Second Embodiment
In the first embodiment described above, the thermal control sheet 10 for the battery pack has a three-layer structure in which the heat dissipation layer 11a, the insulating layer 15, and the heat dissipation layer 11b are arranged in this order, but the thermal control sheet for the battery pack of the present invention is not limited to three layers.
For example, it may have three heat dissipation layers and a heat insulating layer disposed between each adjacent heat dissipation layer.

Figure 3 is a cross-sectional view showing a schematic diagram of a thermal control sheet for a battery pack according to a second embodiment of the present invention. Hereinafter, in the second and third embodiments shown in Figures 3 and 4, the same or equivalent parts as those in the first embodiment are given the same reference numerals in the drawings, and their description will be omitted or simplified. In addition, since the second and third embodiments can be used in place of the thermal control sheet 10 described in the battery pack 100 shown in Figure 2, the effects and the like will be described assuming that the thermal control sheet according to the second embodiment is applied to the battery pack 100.

The thermal control sheet 40 for a battery pack according to the second embodiment includes three heat dissipation layers 11a, 11b, and 11c, a plurality of spacers 12a disposed between the heat dissipation layers 11a and 11b, and a plurality of spacers 12b disposed between the heat dissipation layers 11b and 11c. A gas flow path 18a is formed in the area between the heat dissipation layers 11a and 11b, excluding the spacers 12a, forming a heat insulating layer 15a. Similarly, a gas flow path 18b is formed in the area between the heat dissipation layers 11b and 11c, excluding the spacers 12b, forming a heat insulating layer 15b.
In the second embodiment, similarly to the first embodiment, the heat dissipation layers 11a, 11b, and 11c are made of, for example, stainless steel.

In the second embodiment configured as described above, when the temperature of the battery cell 20a rises within a relatively low temperature range during normal use, the presence of the heat dissipation layer 11a suppresses conductive heat transfer to the battery cell 20b side, and the heat can be diffused while suppressing radiative heat transfer. Also, the heat that reaches the heat insulating layer 15a is reduced by the insulating effect of the gas (air).
In addition, when the temperature of the battery cell 20a further rises during an abnormality, the heat dissipation layer 11a provided at a position in contact with the battery cell 20a can suppress the radiative heat transfer to the insulating layer 15a. Also, a part of the heat propagated to the heat dissipation layer 11a is propagated in the planar direction of the heat dissipation layer 11a and diffused to the outside of the thermal control sheet 40.

Furthermore, the heated gas is released to the outside of the thermal control sheet 40 through the flow path 18a, and gas that was present in other areas flows into the flow path 18a, thereby cooling the heat dissipation layer 11a and the battery cell 20a.

Then, in a similar manner, the heat generated from the battery cell 20a passes through the heat dissipation layer 11b, the insulating layer 15b, and the heat dissipation layer 11c in this order, suppressing conductive heat transfer to the battery cell 20b side and allowing the heat to be diffused. In addition, since radiative heat transfer is suppressed and convective heat transfer from the heat dissipation layer 11b to the heat dissipation layer 11c is suppressed, the propagation of heat between the battery cells can be suppressed and a chain reaction of thermal runaway can be prevented.

The effects of the present invention can be obtained even if the heat dissipation layer has, for example, four or more layers and spacers are disposed between each adjacent heat dissipation layer. However, since increasing the number of layers increases the overall thickness of the thermal control sheet and requires a reduction in the thickness of the heat dissipation layer, it is preferable to appropriately select the number of layers of the heat dissipation layer and the thickness of the spacer, etc., according to the required performance.

Third Embodiment
4 is a cross-sectional view showing a thermal control sheet for a battery pack according to a third embodiment of the present invention. In the thermal control sheet for a battery pack 50 according to the third embodiment, insulating materials 13a and 13b are provided on the outermost surface of the thermal control sheet 10 according to the first embodiment, i.e., between the heat dissipation layer 11a and the battery cell 20a, and between the heat dissipation layer 11b and the battery cell 20b, respectively.

In the third embodiment configured in this manner, the heat insulating materials 13a and 13b are disposed in positions in contact with the battery cells 20a, 20b, and 20c, and therefore the heat generated from the battery cell 20a reaches the heat dissipation layer 11a via the heat insulating material 13a, thereby reducing the amount of heat that reaches the heat dissipation layer 11a.
Thereafter, similarly to the first embodiment, the heat is gradually reduced through the heat dissipation layer 11a, the heat insulating layer 15, and the heat dissipation layer 11b, and the heat transfer is further suppressed through the heat insulating material 13b. Therefore, the heat transfer between the battery cells can be suppressed, and the chain reaction of thermal runaway can be prevented.

Next, we will explain in detail the heat dissipation layer, spacer, heat insulating material, etc. that make up the thermal control sheet for battery packs according to the present invention.

(Heat dissipation layer)
The heat dissipation layer used in the thermal control sheet for a battery pack according to this embodiment has the effect of diffusing the heat that reaches the heat dissipation layer by conductive heat transfer. Therefore, the heat dissipation layer has a thermally conductive layer that efficiently conducts heat in the planar direction, and the thermal conductivity of the thermally conductive layer is 5 (W/m·K) or more. The thermal conductivity of the thermally conductive layer is preferably 15 (W/m·K) or more.
The heat dissipation layer also has the effect of suppressing radiative heat transfer from the battery cell, and therefore the specific value of the emissivity of the heat dissipation layer is preferably less than 0.5, and more preferably less than 0.2.

Specifically, the thermally conductive layer is preferably made of at least one material selected from metal, titanium nitride, and graphite, and more preferably made of at least one material selected from aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, titanium or a titanium alloy, titanium nitride, and graphite.
The thermal conductivity of the above-mentioned materials exemplified as the thermal conductive layer is 5 to 450 (W/m·K), and the heat that reaches the heat dissipation layer can be efficiently diffused via the thermal conductive layer.

The thermal conductivity of the heat dissipation 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).
The emissivity of the heat dissipation layer can be measured in accordance with "Method of measuring emissivity of fine ceramics and ceramic composite materials" described in JIS R 1693.

The heat dissipation layer may be a composite layer in which the heat conduction layer and a layer made of a material selected from metal, ceramic, and graphite are laminated. When a composite layer made of the heat conduction layer and a metal is adopted as the heat dissipation layer, two or more metals selected from stainless steel, copper or copper alloy, silver or silver alloy, nickel or nickel alloy, titanium or titanium alloy, and titanium nitride can be selected. Examples of such heat dissipation layers include a [silver/copper/silver] composite layer, a [nickel/copper/nickel] composite layer, a [nickel/stainless steel/nickel] composite layer, and a [silver/stainless steel/silver] composite layer. The silver, copper, and nickel in the composite layer may each be in the form of an alloy.
When a composite layer of the above-mentioned thermally conductive layer and ceramic is used as the heat dissipation layer, the ceramic may be selected from AlN, SiC, TiN, and the like.
The composite layer can be obtained by forming a metal layer on the surface of a base layer serving as a center by wet plating or vapor deposition, or by laminating layers made of different materials.

As shown in the first and second embodiments, when the thermal control sheet is arranged so that the heat dissipation layer is in contact with the battery cell, it is preferable to select a material for the heat dissipation layer so that the heat dissipation layer can be prevented from being damaged by melting, etc., even if the battery cell becomes hot. Specifically, it is more preferable that the material constituting the heat dissipation layer is made of a metal or ceramic with a melting point of 600°C or higher. It is even more preferable that the heat dissipation layer is made of a metal or ceramic with a melting point of 900°C or higher.

Of the materials specifically given as examples of the thermally conductive layer, stainless steel, silver, and titanium nitride have melting points of approximately 1400°C, approximately 960°C, and 2930°C, respectively. Furthermore, stainless steel and silver are less susceptible to oxidation compared to other metals, and their emissivity does not increase much even when exposed to high temperatures. Titanium nitride also hardly changes when exposed to high temperatures. Therefore, when the heat dissipation layer is in contact with the battery cell, it is more preferable to use stainless steel, silver or a silver alloy, or titanium nitride as the material that constitutes the heat dissipation layer.

On the other hand, as shown in the third embodiment, when a heat insulating material is interposed between the battery cell and the heat dissipation layer, the effects of oxidation and melting due to heat are reduced, so that one material selected from aluminum or an aluminum alloy, copper or a copper alloy, silver or a silver alloy, and titanium nitride, which have excellent thermal conductivity, can be preferably used as the material for the heat dissipation layer.

In order to fully obtain the effect of suppressing radiative heat transfer by the heat dissipation layer and the effect of diffusing heat by conductive heat transfer, the thickness of the heat dissipation layer is preferably 5 μm or more, more preferably 10 μm or more, even more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 50 μm or more. On the other hand, taking into consideration the overall thickness of the thermal control sheet, the thickness of the heat dissipation layer is preferably 300 μm or less, and more preferably 200 μm or less.

Furthermore, the heat dissipation layer may be made of one type of material, or may be made of a laminate of two or more types of materials, as described above, or may be made of multiple thin films of the same material laminated together. When the heat dissipation layer is made of laminated thin films of the same material, the same effect can be obtained if the total thickness of the multiple layers is the same as the thickness of the heat dissipation layer made of a single layer. Therefore, even if the heat dissipation layer is made of multiple layers, it is preferable that the total thickness is within the above range.

(Spacer)
The spacer used in the thermal control sheet for battery pack according to the present embodiment is disposed to secure a space between adjacent heat dissipation layers and form a gas flow path. If a material having a thermal conductivity equal to or higher than that of the heat dissipation layers is used as the spacer, there is a risk that heat will be conducted from one of the heated heat dissipation layers to the other heat dissipation layer via the spacer. Therefore, the spacer is preferably formed of a material having thermal insulation properties, and preferably contains at least one selected from, for example, silicon dioxide, silica sol, ceramic fiber, glass, and mica. Examples of materials containing silicon dioxide include mixtures containing silicon dioxide as the main raw material. Examples of materials containing ceramic fiber include crushed ceramic fiber.

Also, an adhesive bonded to the surface of the heat dissipation layer can be used as the spacer. For example, an inorganic adhesive (silicon-based, calcium-based, etc.) with a high heat resistance can be used as the adhesive, and for example, a mixture whose main ingredient is silicon dioxide can be used. When an adhesive is used, the spacer can be formed by dripping a liquid adhesive material onto multiple locations on the surface of the heat dissipation layer and allowing it to dry and solidify.

The thermal conductivity of the spacer 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 thickness of the spacer, i.e., the distance between adjacent heat dissipation layers, is preferably 0.1 mm or more, more preferably 0.3 mm or more, and even more preferably 0.5 mm or more, in order to ensure a gas flow path. On the other hand, taking into consideration the overall thickness of the thermal control sheet, the thickness of the spacer is preferably 6.0 mm or less, and more preferably 1.5 mm or less.

The number of spacers is not particularly limited as long as a space can be secured between adjacent heat dissipation layers to form a gas flow path. In order to prevent the heat dissipation layers from contacting each other, the number of spacers between adjacent heat dissipation layers is preferably 4 or more.
The shape of the spacer is not particularly limited, and spacers of various shapes such as cylindrical, prismatic, spherical, and other shapes extending long in one direction can be used.

(Thermal insulation)
As shown in the third embodiment, the thermal control sheet for a battery pack according to this embodiment may have a heat insulating material. The heat insulating material is not particularly limited as long as it has a heat insulating effect. Thermal conductivity can be given as an index representing the heat insulating effect, and in this 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 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.
In addition, 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 thermal control sheet>
In this embodiment, the thickness of the thermal control sheet is not particularly limited, but is preferably in the range of 0.05 to 6 mm. If the thickness of the thermal control sheet is 0.05 mm or more, sufficient mechanical strength can be imparted to the thermal control sheet. On the other hand, if the thickness of the thermal control sheet is 6 mm or less, good assembly properties can be obtained.

Next, we will explain the manufacturing method of the thermal control sheet for the battery pack according to this embodiment.

<Method of manufacturing the thermal control sheet>
The thermal control sheet of this embodiment can be obtained, for example, by preparing a pair of heat dissipation layers, dripping adhesive onto the surface of one of the heat dissipation layers and solidifying it to form a spacer, and then overlapping the other heat dissipation layer via the spacer.
Also, a spacer made of a heat insulating material may be prepared and attached to one or both of the heat dissipation layers to prepare a thermal control sheet.

[2. Battery pack]
The battery pack according to the present embodiment is a battery pack in which a plurality of battery cells are connected in series or parallel, and the thermal control sheet for a battery pack according to the present embodiment is interposed between the battery cells. Specifically, for example, as shown in Fig. 3, a battery pack 100 is a battery pack in which a plurality of battery cells 20a, 20b, 20c are arranged side by side, connected in series or parallel, and stored in a battery case 30, and the thermal control sheet 10 is interposed between the battery cells 20a, 20b, 20c.

In such a battery pack 100, the thermal control sheet 10 is interposed between each of the battery cells 20a, 20b, and 20c, so that during normal use, the transfer of heat between each of the battery cells 20a, 20b, and 20c can be suppressed.
In addition, even if one of the battery cells 20a, 20b, and 20c experiences thermal runaway, becomes too hot, expands, or catches fire, the presence of the thermal control sheet 10 according to this embodiment can suppress the transfer of heat between the battery cells 20a, 20b, and 20c. This makes it possible to prevent a chain reaction of thermal runaway, and minimize the adverse effects on the other battery cells.

The thermal control sheet according to this embodiment can be easily bent depending on the type and thickness of the heat dissipation layer. Therefore, it can be adapted to any shape, regardless of 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.

Below, we will explain an example of the invention and a comparative example of the thermal control sheet for a battery pack according to this embodiment.

A thermal control sheet was fabricated as an example of the invention by preparing multiple heat dissipation layers made of stainless steel, forming spacers between adjacent heat dissipation layers by bonding inorganic adhesive, and stacking the heat dissipation layers. Note that as an example of the invention, a thermal control sheet was fabricated in which the heat dissipation layers were 2 to 5 layers and spacers were disposed between adjacent heat dissipation layers.
In addition, a sheet was prepared as a comparative example by laminating the same number of heat dissipation layers as in the invention example. The effect of heat control on the presence or absence of a heat insulating layer consisting of a spacer and a gas flow path was then evaluated for the obtained sheet.

Fig. 5 is a cross-sectional view showing a typical method for evaluating the effect of thermal control, and Fig. 6 is a perspective view showing the size of the thermal control sheet used in this example.
As shown in Fig. 5, an Fe jig 16 heated to 800 ° C. in an electric furnace was placed on one side (surface of the heat dissipation layer 11a) of the thermal control sheet 40 to simulate an abnormality, so that the Fe jig 16 was moved from the electric furnace within 5 seconds. Then, the temperature was measured 90 seconds after placement by a thermocouple 17 placed on the other side (surface of the heat dissipation layer 11c) of the thermal control sheet 10, and the influence of thermal control in an abnormality was evaluated. In addition, in the evaluation of the thermal control of the invention example and the comparative example, the thermal control sheet 40 shown in Fig. 5 was replaced with a test piece of the invention example in which the number of heat dissipation layers was changed, and a test piece of the comparative example in which only the heat dissipation layer was laminated, and the influence of thermal control was evaluated.

As shown in FIG. 5, the thermal control sheet 40 used as an example of the invention was a square with a side length of 50 mm. Furthermore, on one side of the thermal control sheet 40, the width of the contact area A with the Fe jig 16 was 25 mm, and the length in the direction perpendicular to the width direction was 50 mm from one side of the thermal control sheet 40 to the opposing side.

Detailed measurement conditions are shown in Table 1 below, and lamination conditions and measurement results are shown in Table 2 below. In the tables shown below, test pieces with the same No. for the invention example and the comparative example have the same number of layers. In addition, "SUS" represents stainless steel, and "-" represents the absence of that layer.
Furthermore, the emissivity of the stainless steel plate serving as the heat dissipation layer was about 0.2, and the thermal conductivity of the spacer was 0.80 (W/m·K).

As shown in Table 2 above, Example No. 1 is a thermal control sheet according to an embodiment of the present invention consisting of two heat dissipation layers and a heat insulating layer between them, and therefore, compared to Comparative Example No. 1 consisting of only two heat dissipation layers, it was possible to obtain a suppression effect of radiative heat transfer in an abnormal state and a diffusion effect by conductive heat transfer. Similarly, Example No. 2 is a thermal control sheet according to an embodiment of the present invention consisting of three heat dissipation layers and a heat insulating layer between them, and therefore, compared to Comparative Example No. 2 consisting of only three heat dissipation layers, it was possible to obtain a superior heat insulating effect in an abnormal state.
In addition, since Example No. 3 is a thermal control sheet according to an embodiment of the present invention consisting of four heat dissipation layers and a heat insulating layer therebetween, it has a superior heat insulating effect in an abnormal state compared to Comparative Example No. 3 consisting of only four heat dissipation layers. Example No. 4 is a thermal control sheet according to an embodiment of the present invention consisting of five heat dissipation layers and a heat insulating layer therebetween, so it has a superior heat insulating effect in an abnormal state compared to Comparative Example No. 4 consisting of only five heat dissipation layers.
In addition, since Comparative Examples No. 1 to 4 did not have a gas insulating layer, they were unable to obtain a sufficient insulating effect against heat generation during normal operation at relatively low temperatures, as compared with Invention Examples No. 1 to 4.

10, 40, 50 Thermal control sheet for battery pack 11a, 11b, 11c Heat dissipation layer 12, 12a, 12b Spacer 13a, 13b Heat insulating material 15, 15a, 15b Heat insulating layer 17 Thermocouple 18 Flow path 20a, 20b, 20c Battery cell 30 Battery case 100 Battery pack

Claims (10)

A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the thermal control sheet being interposed between the battery cells,
A plurality of heat dissipation layers;
a spacer disposed between the plurality of adjacent heat dissipation layers, and a gas flow path is formed in an area between the plurality of adjacent heat dissipation layers excluding the spacer,
The heat dissipation layer has a heat conduction layer having a thermal conductivity of 5 to 450 (W/m·K ) ,
The spacer comprises at least one material selected from the group consisting of silicon dioxide, silica sol, ceramic fiber, glass, and mica . A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the thermal control sheet being interposed between the battery cells,
A plurality of heat dissipation layers;
a spacer disposed between the plurality of adjacent heat dissipation layers, and a gas flow path is formed in an area between the plurality of adjacent heat dissipation layers excluding the spacer,
The heat dissipation layer has a heat conduction layer having a thermal conductivity of 5 to 450 (W/m·K ) ,
The thermal control sheet for a battery pack, wherein the spacer is an adhesive fixed between adjacent ones of the heat dissipation layers . A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the thermal control sheet being interposed between the battery cells,
A plurality of heat dissipation layers;
a spacer disposed between the plurality of adjacent heat dissipation layers, and a gas flow path is formed in an area between the plurality of adjacent heat dissipation layers excluding the spacer,
The heat dissipation layer has a heat conduction layer having a thermal conductivity of 5 to 450 (W/m·K ) ,
The thermal control sheet for a battery pack , wherein the heat dissipation layer is a composite layer formed by laminating the thermally conductive layer and a layer made of a material selected from the group consisting of metal, ceramic, and graphite . A thermal control sheet for a battery assembly used in a battery assembly in which a plurality of battery cells are connected in series or parallel, the thermal control sheet being interposed between the battery cells,
A plurality of heat dissipation layers;
a spacer disposed between the adjacent heat dissipation layers, and a gas flow path is formed in an area between the adjacent heat dissipation layers excluding the spacer,
The heat dissipation layer has a heat conduction layer having a thermal conductivity of 5 to 450 (W/m·K ) ,
A thermal control sheet for a battery assembly , comprising a heat insulating material disposed in a position in contact with the battery cells . 5. The thermal control sheet for a battery pack according to claim 4 , wherein the heat insulating material contains at least one material selected from the group consisting of inorganic fibers, organic fibers, inorganic particles, and organic particles. The thermal control sheet for a battery pack according to claim 5, characterized in that the heat insulating material contains at least one selected from the group consisting of alumina fiber, carbon fiber, mica, basalt fiber, soluble fiber, refractory ceramic fiber, glass fiber, aerogel composite material, microporous particles, hollow silica particles, thermally expandable inorganic materials, and aerogel. 7. The thermal control sheet for a battery pack according to claim 1 , wherein the thermally conductive layer is made of at least one material selected from the group consisting of metal, titanium nitride, and graphite. 8. The thermal control sheet for a battery pack according to claim 7, wherein the thermal conductive layer is made of at least one material selected from the group consisting of aluminum or an aluminum alloy, stainless steel, copper or a copper alloy, silver or a silver alloy, nickel or a nickel alloy, titanium or a titanium alloy, titanium nitride, and graphite. 9. The thermal control sheet for a battery pack according to claim 1 , wherein the heat dissipation layer has an emissivity of 0.5 or less. A battery case;
A plurality of battery cells housed inside the battery case and connected in series or parallel;
A battery pack comprising: the thermal control sheet for a battery pack according to any one of claims 1 to 9 , interposed between the plurality of battery cells.

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