JP2023056746A - Heat transfer suppression sheet and battery pack - Google Patents

Abstract

To provide a heat transfer suppression sheet which can efficiently diffuse, to an outside, heat generated during normal use of battery cells, and suppresses propagation of heat between the battery cells during abnormal situations of the battery cells, thereby capable of preventing a chain thermal runaway, and which can also prevent falling off of particles, etc.SOLUTION: There is provided, a heat transfer suppression sheet 10 which is used in a battery pack including a plurality of battery cells connected in series or parallel therein. The heat transfer suppression sheet includes: a pair of heat insulation materials 2; an intermediate layer 3 arranged between the pair of heat insulation materials 2; and a first resin film disposed so as to enclose the heat insulation materials 2 and the intermediate layer 3 from the outside. The intermediate layer 3 includes a heat diffusion sheet 5 having higher thermal conductivity than the heat insulation materials 2, and a second resin film 6 laminated on each of both sides of the heat diffusion sheet 5, the sides being perpendicular to a thickness direction.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a heat transfer suppressing sheet and an assembled battery using the heat transfer suppressing sheet, which is suitably used for an assembled battery that serves as a power source for an electric motor that drives an electric vehicle or a hybrid vehicle, for example.

2. Description of the Related Art In recent years, from the viewpoint of environmental protection, development of electric vehicles or hybrid vehicles driven by electric motors has been vigorously advanced. The electric vehicle, hybrid vehicle, or the like is equipped with an assembled battery in which a plurality of battery cells are connected in series or in parallel to serve as a power source for an electric drive motor.

Lithium-ion secondary batteries, which have higher capacity and higher output than lead-acid batteries or nickel-metal hydride batteries, are mainly used for these battery cells. When thermal runaway occurs in one battery cell (i.e., in the case of "battery cell failure"), heat transfer to other adjacent battery cells may cause thermal runaway in other battery cells. be.

In addition, battery cells may swell during charging/discharging or repeated use. Therefore, when a partition member, for example, is arranged between battery cells, the partition member is required to have pressure resistance.

For example, Patent Literature 1 discloses an inner package capable of holding a liquid, and an outer package that accommodates the inner package and the liquid. A partition member has been proposed in which the ratio of .
According to Patent Document 1, it is described that a partition member having excellent pressure resistance and heat conduction characteristics can be obtained.

Further, Patent Document 2 discloses a heat transfer suppressing sheet having a first heat insulating layer and a second heat insulating layer, and a metal layer sandwiched between the first heat insulating layer and the second heat insulating layer. is disclosed.
According to the heat transfer suppression sheet, excellent heat transfer suppression effect and excellent mechanical strength can be obtained.

Further, Patent Literature 3 proposes a battery module that includes a plurality of battery cells, a module housing that stores the battery cells, and a gap material that enters inside the module housing. The interstitial material between the battery cells is not filled so as to cover the entire battery cells, and the upper side is a void. A battery cell is a battery element in which a plurality of plate-shaped positive and negative plates are sandwiched between partition plates and alternately stacked, and the battery elements are laminated and enclosed in a flexible exterior film together with an electrolyte. .
According to the battery module described in Patent Literature 3, it is described that a plurality of battery cells can be stably held inside and excellent heat dissipation properties of heat generated from the battery cells can be obtained.

WO2019/107562 JP 2020-165483 A JP 2020-9774 A

By the way, when the battery cells assembled into a battery are subjected to charge-discharge cycles (that is, when the battery cells are used normally), in order to fully demonstrate the charge-discharge performance of the battery cells, the surface of the battery cells must be The temperature must be kept below a predetermined value (for example, below 150°C).
In addition, in the event of an abnormal situation in which the temperature of the battery cells rises to, for example, 200° C. or higher, the battery cells are effectively cooled, and heat transfer to adjacent battery cells is suppressed to prevent thermal runaway. need to stop.

In addition, there are various materials used as heat insulating materials to be placed between a plurality of battery cells in an assembled battery, and in recent years, heat insulating materials containing inorganic particles and organic particles have also been developed. . In the case of using such a heat insulating material, if the heat insulating material is subjected to pressure or is subjected to vibration during running of a vehicle, powder and particles may come off.

However, although the partition member described in Patent Document 1 and the gap material described in Patent Document 3 can prevent powder and particles from falling off, they can effectively dissipate the heat generated during charge/discharge cycles. Cannot diffuse to the outside. Moreover, when thermal runaway occurs in one battery cell, it is difficult to effectively suppress a chain of thermal runaway with only the above structure.
In addition, the heat transfer suppressing sheet described in Patent Document 2 has not been sufficiently studied about falling off of particles, etc., and depending on the material of the heat insulating layer used, powder and particles may fall off. .
Furthermore, with the recent diversification of vehicles, etc., the heat insulating material used in the assembled battery for the power source of the electric drive motor is not only between the battery cells, but also between the battery cells and the battery case from the viewpoint of manufacturing cost reduction. It is preferable to have high versatility that can also be used between and the like.

The present invention has been made in view of the above problems, and is capable of efficiently diffusing heat generated during normal use of a battery cell to the outside, and is capable of effectively dissipating heat generated between battery cells in the event of an abnormality. To provide a heat transfer suppression sheet and an assembled battery that can suppress the propagation of heat, prevent a chain of thermal runaway, have high versatility, and can prevent falling off of particles, etc. do.

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

[1] A heat transfer suppression sheet used in an assembled battery in which a plurality of battery cells are connected in series or in parallel,
a pair of heat insulating materials laminated in the thickness direction;
an intermediate layer disposed between the pair of heat insulating materials;
a first resin film that encloses and seals at least the heat insulating material;
The intermediate layer includes a heat diffusion sheet having a higher thermal conductivity than the heat insulating material,
and a second resin film laminated on both sides perpendicular to the thickness direction of the heat diffusion sheet.

Further, preferred embodiments of the present invention relating to the heat transfer suppressing sheet relate to the following [2] to [19].

[2] At least one of the end faces parallel to the thickness direction of the intermediate layer, the intermediate layer protrudes from the pair of heat insulating materials, and forms a protruding portion together with the first resin film. The heat transfer suppressing sheet according to [1], characterized in that

[3] The intermediate layer protrudes from the pair of heat insulating materials on all end faces parallel to the thickness direction of the intermediate layer, and forms a protruding portion together with the first resin film. The heat transfer suppressing sheet according to [2].

[4] The heat transfer suppressing sheet according to [2] or [3], wherein the end surface of the heat diffusion sheet is exposed at the projecting portion.

[5] Any one of [1] to [4], wherein the intermediate layer is a film obtained by laminating and integrating the second resin film on both sides of the heat diffusion sheet. The heat transfer suppressing sheet according to .

[6] The heat transfer suppressing sheet according to [5], wherein the intermediate layer is a laminate film.

[7] The heat insulating material is included in the first resin film and the second resin film by heat-sealing the first resin film and the second resin film. The heat transfer suppressing sheet according to any one of [1] to [6], which is sealed.

[8] The first resin film and the second resin film are made of the same material or different materials, and are polyethylene, polypropylene, polystyrene, nylon, acrylic, epoxy resin, polyurethane, and polyether, respectively. The heat according to any one of [1] to [7], characterized by containing at least one resin selected from ether ketone, polyetherimide, polyethylene terephthalate, polyphenyl sulfide, polycarbonate and aramid. Transmission suppression sheet.

[9] The heat transfer suppressing sheet according to [8], wherein the first resin film and the second resin film are made of the same material.

[10] The heat transfer suppressing member according to any one of [1] to [9], wherein the first resin film has a thickness of 1 mm or less.

[11] The heat transfer suppressing member according to any one of [1] to [10], wherein the second resin film has a thickness of 5 μm or more and 100 μm or less.

[12] The heat transfer suppressing member according to any one of [1] to [11], wherein the thickness of the first resin film is thicker than the thickness of the second resin film. .

[13] The heat diffusion sheet is made of aluminum or an aluminum alloy, copper or a copper alloy, tin or a tin alloy, nickel or a nickel alloy, stainless steel, lead or a lead alloy, bronze, iridium, phosphor bronze, silver or a silver alloy, titanium. Alternatively, the heat transfer suppressing sheet according to any one of [1] to [12], containing at least one selected from titanium alloys, ceramics, graphite and diamond-like carbon.

[14] The heat transfer suppressing sheet according to [13], wherein the ceramic is at least one selected from AlN, SiC, BN and TiN.

[15] The heat transfer suppressing sheet according to any one of [1] to [14], wherein the heat insulating material has a thermal conductivity of less than 1 (W/m·K).

[16] The heat insulating material according to any one of [1] to [15], characterized in that it contains at least one selected from inorganic fibers, organic fibers, inorganic particles and organic particles. Heat transfer suppression sheet.

[17] The heat insulating material includes inorganic particles, first inorganic fibers, and second inorganic fibers,
The first inorganic fibers are amorphous fibers,
[16], wherein the second inorganic fiber is composed of at least one selected from an amorphous fiber having a higher glass transition point than the first inorganic fiber and a crystalline fiber; The heat transfer suppressing sheet described.

[18] The heat insulating material includes silica nanoparticles, titania, alumina fibers, carbon fibers, mica, basalt fibers, soluble fibers, refractory ceramic fibers, glass fibers, airgel composites, microporous particles, hollow silica particles, and thermal expansion. inorganic materials, airgel, silica, zirconia, zircon, barium titanate, zinc oxide, alumina, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, manganese hydroxide, zirconium hydroxide, water Gallium oxide, fibers containing _SiO2 , silica fibers, alumina fibers, ceramic fibers, rock wool, alkaline earth silicate fibers, zirconia fibers, and mineral fibers, characterized by containing at least one selected from The heat transfer suppressing sheet according to [16] or [17].

[19] The heat transfer suppressing sheet according to any one of [1] to [18], which is interposed between the plurality of battery cells.

Further, the above object of the present invention is achieved by the following configurations [20] and [21] relating to the assembled battery.

[20] a battery case;
a plurality of battery cells stored in the battery case and connected in series or in parallel;
and a heat transfer suppressing sheet according to any one of [1] to [18] interposed between the plurality of battery cells.

[21] a battery case;
a plurality of battery cells stored in the battery case and connected in series or in parallel;
a heat transfer suppressing sheet according to [4] interposed between the plurality of battery cells;
a heat transfer member provided between the plurality of battery cells and the battery case;
has
An assembled battery, wherein an end surface of the heat diffusion sheet and the heat transfer member are in contact with each other in the projecting portion.

In the heat transfer suppressing sheet of the present invention, since the pair of heat insulating materials are sealed with the first resin film, it is possible to prevent particles and the like constituting the heat insulating materials from falling off.
In addition, since the heat transfer suppressing sheet of the present invention includes the heat diffusion sheet, heat can be diffused and released in the surface direction of the heat diffusion sheet, so that the heat generated during normal use of the battery cell can be efficiently dissipated. can be diffused externally.
Furthermore, the heat transfer suppressing sheet of the present invention can suppress heat transfer in the thickness direction of the heat transfer suppressing sheet by providing a heat insulating material. It is possible to suppress heat propagation and prevent a chain of thermal runaways.

Since the assembled battery of the present invention has the heat transfer suppressing sheet interposed between the plurality of battery cells, heat can be efficiently diffused during normal use of the battery cells and in the event of an abnormality. can suppress the heat propagation and prevent a chain of thermal runaway.

FIG. 1 is a schematic diagram showing a heat transfer suppression sheet according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an assembled battery to which the heat transfer suppressing sheet according to this embodiment is applied. FIG. 3 is a schematic diagram showing a heat transfer suppression sheet according to a second embodiment of the present invention.

The inventor of the present invention has found that heat can be efficiently diffused to the outside during normal use of the battery cell while suppressing heat propagation in the event of an abnormality in the battery cell, and can prevent particles from falling off. In order to provide a transmission suppressing sheet, extensive studies were conducted.

As a result, the present inventors used a heat transfer suppression sheet in which an intermediate layer having a heat diffusion sheet and a resin film is arranged between a pair of heat insulating materials, and when this is placed between battery cells, It was found that the heat generated from the heat diffusion sheet can be diffused in the surface direction of the heat diffusion sheet and released.
That is, when the temperature of a certain battery cell rises, the heat generated from the battery cell is reduced through the heat insulating material. After that, the heat reaching the heat diffusion sheet disposed between the pair of heat insulating materials is diffused in the surface direction of the heat diffusion sheet by conductive heat transfer.
In this way, when a certain battery cell reaches a high temperature, the heat transfer is suppressed before it reaches the adjacent battery cell, and the heat can be diffused to the outside, thereby suppressing a chain of thermal runaway. be able to.

In addition, the inventors have found that by encapsulating and sealing the heat insulating material with a resin film, it is possible to prevent particles of the heat insulating material from falling off.

Hereinafter, heat transfer suppression sheets and assembled batteries according to first and second embodiments of the present invention will be described in detail with reference to the drawings. Also, the heat insulating material, the heat diffusion sheet, the resin film, and the like, which constitute the heat transfer suppressing sheet according to the present embodiment, will be described. It should be noted that the present invention is not limited to the embodiments described below, and can be arbitrarily modified without departing from the gist of the present invention.

[1. Heat transfer suppression sheet]
<First Embodiment>
FIG. 1 is a schematic diagram showing a heat transfer suppression sheet according to a first embodiment of the present invention.
A heat transfer suppressing sheet 10 according to the first embodiment is used in an assembled battery, which will be described later, and arranged between battery cells. The heat transfer suppressing sheet 10 includes a pair of heat insulating materials 2, an intermediate layer 3 disposed between the pair of heat insulating materials 2, and arranged so as to wrap the heat insulating materials 2 and the intermediate layer 3 from the outside. and a first resin film 4 .
Further, the intermediate layer 3 includes a heat diffusion sheet 5 having a higher thermal conductivity than the heat insulating material 2 and a second resin film 6 laminated on both sides of the heat diffusion sheet 5 perpendicular to the thickness direction. As the intermediate layer 3, it is possible to use a heat diffusion sheet 5 and two second resin films 6 bonded together with an adhesive or the like, or a laminate film obtained by laminating them. Alternatively, a vapor-deposited film obtained by vapor-depositing a metal such as aluminum, which is a material of the heat diffusion sheet 5, is prepared on the surface of the second resin film 6, and the second resin film 6 is further laminated on the surface thereof for lamination. It is also possible to use an intermediate layer 3 made by

In the intermediate layer 3 and the first resin film 4 , the four sides of the surfaces perpendicular to the thickness direction are designed to be larger than the heat insulating material 2 . Then, the heat insulating material 2 is arranged between the intermediate layer 3 and the first resin film 4, and the intermediate layer 3 and the first resin film 4 are adhered at their peripheral portions, so that each heat insulating material 2 is enclosed and sealed between the intermediate layer 3 and the first resin film 4 .

The intermediate layer 3 is disposed between the heat insulating materials 2 laminated in the thickness direction, and extends planarly to the four end surfaces of the intermediate layer 3 . On the other hand, the first resin film 4 is bent along the end face parallel to the thickness direction of the heat insulating material 2 and further bent along the extending direction of the intermediate layer 3 .
Therefore, the intermediate layer 3 and the first resin film 4 protrude from the end face parallel to the thickness direction of the heat insulating material 2 to form a protruding portion 1a. Moreover, the four end surfaces of the heat diffusion sheet 5 are exposed at the projecting portion 1a.

In the first embodiment, the heat diffusion sheet 5 forming the intermediate layer 3 is made of a material having a higher thermal conductivity than the heat insulating material 2, such as an aluminum film. Also, the first resin film 4 and the second resin film 6 are, for example, polyethylene films.

FIG. 2 is a cross-sectional view schematically showing an assembled battery to which the heat transfer suppressing sheet according to this embodiment is applied.
The assembled battery 100 includes a battery case 30, a plurality of battery cells 20a, 20b, and 20c stored inside the battery case 30, between the battery cells 20a and 20b, and between the battery cells 20b and 20c. and a heat transfer suppression sheet 10 interposed therebetween. The plurality of battery cells 20a, 20b, 20c are connected in series or in parallel by bus bars (not shown) or the like. A plate-shaped heat transfer member 21 is arranged between the bottom surface of the battery case 30 and the plurality of battery cells 20a, 20b, and 20c, and the protrusion 1a is in contact with the heat transfer member 21. As shown in FIG.

The heat transfer member 21 is a member that transfers the heat of the battery cells 20a, 20b, 20c and the heat transfer suppression sheet 10 to the heat transfer member 21 to promote heat dissipation. It also includes a thermal interface material (TIM) disposed between the heat sink or heat storage material and the battery cells 20a, 20b, 20c.

The battery cells 20a, 20b, and 20c are preferably, for example, lithium ion secondary batteries, but are not particularly limited to this, and may be applied to other secondary batteries.

In the first embodiment configured as described above, since the first resin film 4 is disposed on the outer surface of the pair of heat insulating materials 2 sandwiching the intermediate layer 3, the first resin film 4 encloses and seals at least the heat insulating material 2 . Therefore, it is possible to prevent the particles and the like, which are the materials forming the heat insulating material 2, from falling off.

Further, for example, when the temperature of the battery cell 20a rises, the heat generated from the battery cell 20a reaches the intermediate layer 3 after being reduced through the heat insulating material 2 . In the present embodiment, the intermediate layer 3 is composed of the second resin film 6 and the heat diffusion sheet 5 made of an aluminum film, and the heat generated from the battery cells 20a is transferred through the second resin film 6. , reaches the heat diffusion sheet 5 . Since the thermal diffusion sheet 5 has a higher thermal conductivity than the heat insulating material 2, heat is diffused in the surface direction of the thermal diffusion sheet 5 and released from the end faces of the thermal diffusion sheet 5 at the protrusions 1a. Moreover, since the protrusion 1 a on one end surface of the heat transfer suppressing sheet 10 is in contact with the heat transfer member 21 , heat can be efficiently released through the heat transfer member 21 .
The surface direction of the heat diffusion sheet 5 means the direction of the surface perpendicular to the thickness direction of the heat diffusion sheet 5 .

After that, the heat reduced by the heat diffusion sheet 5 is further reduced through the heat insulating material 2 arranged on the battery cell 20b side.
By disposing the battery cell 20a and the battery cell 20b with the heat transfer suppressing sheet 10 interposed in this way, when heat is generated from the battery cell 20a, the heat can be efficiently diffused. At the same time, heat propagation between battery cells can be suppressed, and a chain of thermal runaway can be prevented.

Furthermore, in the present embodiment, since the intermediate layer 3 having the heat diffusion sheet 5 is arranged on one surface of the heat insulating material 2, even when the temperature rise of the battery cell 20a stops, the heat insulating material The heat stored in the material 2 moves to the intermediate layer 3 side. Therefore, the heat stored in the heat insulating material can be prevented from returning to the battery cell 20a or being transmitted to the battery cell 20b, and the heat can be released to the outside through the heat diffusion sheet 5.

In the above-described heat transfer suppressing sheet 10, if the projecting portion 1a is formed on at least one of the end faces parallel to the thickness direction, the above effects can be obtained. In order to obtain this, it is preferable that the protrusions 1a are formed on all the end surfaces of the heat transfer suppressing sheet 10 parallel to the thickness direction.

The heat diffusion sheet 5 and the second resin film 6 forming the intermediate layer 3 are not necessarily integrated, but as described above, the second resin film 6 and the heat diffusion sheet 5 are It is preferably integrated by lamination or the like.
When the intermediate layer 3 is integrated in this way, it is possible to prevent lamination deviation from occurring between the second resin film 6 and the heat diffusion sheet 5 when the heat transfer suppressing sheet 10 is manufactured. .

Further, for example, when the heat transfer suppressing sheet 10 is applied to the assembled battery 100, since the heat diffusion sheet 5 is fixed, heat transfer caused by stacking misalignment that may occur due to the influence of vibration etc. received by the assembled battery 100 is reduced. Reduction of the suppression effect can also be suppressed.
Furthermore, if the thermal diffusion sheet 5 and the second resin film 6 are in close contact with each other and integrated, the surface of the thermal diffusion sheet 5 may be It is possible to suppress the formation of an oxide film or the like on the surface. As a result, it is possible to suppress the deterioration of the conductive heat transfer of the heat diffusion sheet 5 due to the formation of the oxide film, and to maintain the heat diffusion effect in the plane direction.
Furthermore, the heat transfer suppressing sheet 10 can be easily manufactured only by bonding the first resin film 4 and the second resin film 6 of the intermediate layer 3 by a simple bonding method such as heat sealing. can be done.

In addition, in the present embodiment, when the emissivity of the heat diffusion sheet 5 is low, radiant heat transfer can be suppressed. can be further suppressed.

In addition, the heat transfer suppressing sheet 10 is configured symmetrically with respect to the heat diffusion sheet 5 in the thickness direction. Therefore, even when heat is generated from the battery cell 20b, the heat is transferred toward the battery cell 20a through the heat insulating material 2, the intermediate layer 3 (heat diffusion sheet 5), and the heat insulating material 2 in this order. It is reduced step by step, and the heat propagation to the battery cell 20a can be suppressed.
Similarly, the heat generated from the battery cell 20b is gradually reduced toward the battery cell 20c by passing through the heat insulating material 2, the intermediate layer 3 (heat diffusion sheet 5), and the heat insulating material 2 in this order. The propagation of heat to the battery cell 20c can be suppressed.

<Second embodiment>
FIG. 3 is a schematic diagram showing a heat transfer suppression sheet according to a second embodiment of the present invention.
In the second embodiment shown in FIG. 3, the same or equivalent parts as those of the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted or simplified.
Further, since the second embodiment can be used in place of the heat transfer suppressing sheet 10 described in the assembled battery 100 shown in FIG. The effect etc. are demonstrated as what was applied.

As shown in FIG. 3 , a heat transfer suppressing sheet 12 according to the second embodiment is composed of a pair of heat transfer suppressing members 11 .
The heat transfer suppressing member 11 is composed of the heat insulating material 2, the functional film 13 laminated on one side perpendicular to the thickness direction of the heat insulating material 2, and the other side perpendicular to the thickness direction of the heat insulating material 2. and a first resin film 4 that is coated. The functional film 13 has a heat diffusion sheet 5 made of an aluminum film or the like and a second resin film 6, and is arranged so that the second resin film 6 faces the heat insulating material 2 side. As the functional film 13 , the thermal diffusion sheet 5 and the second resin film 6 are laminated with an adhesive or the like, or a laminated film, or the thermal diffusion sheet 5 is laminated on the surface of the second resin film 6 . A vapor-deposited film obtained by vapor-depositing a metal such as aluminum, which is a material for the film, can be used.

Moreover, in the functional film 13 and the first resin film 4 , the four sides of the surfaces perpendicular to the thickness direction are designed to be larger than the heat insulating material 2 . Then, the heat insulating material 2 is arranged between the functional film 13 and the first resin film 4, and the functional film 13 and the first resin film 4 are adhered at their peripheral portions, thereby providing heat insulation. The material 2 is enclosed and sealed between the functional film 13 and the first resin film 4 .

In addition, the functional film 13 extends flatly along one surface of the heat insulating material 2 to the edge. On the other hand, the first resin film 4 is bent along the end face parallel to the thickness direction of the heat insulating material 2 and further bent along the extending direction of the functional film 13 .
Therefore, the functional film 13 and the first resin film 4 protrude from the end faces parallel to the thickness direction of the heat insulating material 2 .

The pair of heat transfer suppressing members 11 are arranged so that the heat diffusion sheets 5 face each other and contact each other, thereby forming the heat transfer suppressing sheet 12 . Further, when the pair of heat transfer suppressing members 11 are combined, the protruding portions of the functional film 13 and the first resin film 4 are united to form the protruding portion 11a.
It should be noted that the pair of heat transfer suppressing members may be simply placed on top of each other, or may be fixed together with an adhesive or locking material.

Also in the second embodiment configured in this manner, the pair of heat insulating materials 2 of the heat transfer suppressing sheet 12 are substantially enclosed in the first resin film 4, so that the heat insulating materials 2 It is possible to prevent the falling off of particles, etc., which are the materials constituting the.
Further, in the second embodiment, unlike the first embodiment, the intermediate layer 3 is formed by a pair of laminated thermal diffusion sheets 5 and a pair of second resin films 6 laminated on both sides thereof. However, the function of the heat diffusion sheet 5 is the same as in the first embodiment. That is, after reaching the heat diffusion sheet 5, the heat generated from the battery cells 20a is diffused in the surface direction and diffused from the protrusions 11a. A heat insulation effect can be obtained.

In the first embodiment and the second embodiment, when the thermal diffusion sheets 5 having the same thickness are used, the second embodiment has a structure in which a pair of the thermal diffusion sheets 5 are laminated. Therefore, the thickness of the heat transfer suppression sheet 12 is increased. However, since the thicker the heat diffusion sheet 5, the more heat is diffused in the surface direction, the thickness of the heat diffusion sheet 5 may be adjusted according to the required size.
Further, when the pair of heat transfer suppressing members 11 are arranged between the battery cells, an aluminum film having an arbitrary thickness is further sandwiched between the heat diffusion sheets 5 arranged so as to face each other. The transmission suppression sheet 12 can be designed to have any thickness, and the effect of transmitting and releasing heat in the plane direction can be further enhanced.

Furthermore, in the present embodiment, only one heat transfer suppressing member 11 can be arranged between the battery case 30 and the battery cells 20a, 20b, 20c. As a result, it is possible to prevent heat from being transferred from the battery cells 20a, 20b, and 20c to the outside.
Therefore, as shown in the second embodiment, if the heat transfer suppressing sheet 12 is composed of a pair of heat transfer suppressing members 11, various forms can be used according to the place of use, the interval between the battery cells, and the like. can be taken, the versatility is high.

In the first and second embodiments, the intermediate layer 3 and the first resin film 4 protrude outward from the end surface parallel to the thickness direction of the heat insulating material 2 to form protrusions 1a and 11a. However, the invention is not limited to such a form.
For example, a form in which a pair of heat insulating materials sandwiching the intermediate layer 3 are completely wrapped with the first resin film 4 may be used. Moreover, in the case where the heat transfer suppressing sheet 12 is divided into a pair of heat transfer suppressing members 11 as in the second embodiment, the intermediate layer 3 and the first resin film 4 form the heat insulating material 2 It may be in a form that envelops the
However, as described above, the first and second embodiments having the protrusions 1a and 11a can expose the end surface of the heat diffusion sheet 5 in the intermediate layer 3, so that the heat reaching the intermediate layer 3 is easily released to the outside.

Furthermore, in the case where the heat transfer suppressing sheet 12 is divided into a pair of heat transfer suppressing members 1, the overlapping area of the heat diffusion sheet 5 in the projecting portion 11a is opened to separate the heat diffusion sheet 5. The edges can be exposed in a plane. Therefore, when the exposed area on the surface is brought into contact with the heat transfer member 21, it is possible to obtain the effect of further dissipating heat.

Next, the heat insulating material, the intermediate layer, etc. that constitute the heat transfer suppressing sheet according to the present embodiment will be described in detail.

<1-1. Insulation>
The heat insulating material used for the heat transfer suppressing sheet according to this embodiment is not particularly limited as long as it has a heat insulating effect. Thermal conductivity can be mentioned as an index representing the heat insulating effect. In the present embodiment, the thermal conductivity of the heat insulating material is preferably less than 1 (W / m K), /m·K), and more preferably less than 0.2 (W/m·K). Furthermore, the thermal conductivity of the heat insulating material is more preferably less than 0.1 (W/mK), more preferably less than 0.05 (W/mK), and more preferably less than 0.02 (W/mK). /m·K) is particularly preferred.
The thermal conductivity of the heat insulating material can be measured according to JIS R 2251, "Testing Method for Thermal Conductivity of Refractories".

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.
As inorganic fibers, alumina fibers, carbon fibers, basalt fibers, soluble fibers, refractory ceramic fibers, glass fibers, airgel composites, and the like can be used.
A cellulose fiber etc. can be used as an organic fiber.
As for these fibers, a single fiber may be used, or two or more types of fibers may be used in combination.

As inorganic particles, mica, microporous particles, hollow silica particles, thermally expandable inorganic materials and aerogels can be used.
Vermiculite, bentonite, mica, perlite, etc., can be mentioned as thermally expandable inorganic materials.
Hollow polystyrene particles or the like can be used as the organic particles.

Among these heat insulating materials, alumina fibers, glass fibers, airgel composites, and the like can be preferably used.

Further, another example of the heat insulating material specifically includes inorganic particles, first inorganic fibers, and second inorganic fibers, the first inorganic fibers being amorphous fibers, and The second inorganic fiber can include at least one selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers and crystalline fibers.
The inorganic particles, the first inorganic fibers, and the second inorganic fibers are all heat-resistant materials, and furthermore, numerous minute spaces are formed between the particles, between the particles and the fibers, and between the fibers, Since the heat insulation effect of air is also exhibited, it is excellent in heat transfer suppression performance.
The inorganic particles, the first inorganic fibers, and the second inorganic fibers that may be contained in the heat insulating material are described in detail below.

<1-1-1. Inorganic particles>
The material of the inorganic particles is not particularly limited, but from the viewpoint of the heat transfer suppressing effect, the inorganic particles are preferably made of at least one selected from oxide particles, carbide particles, nitride particles and inorganic hydrate particles. , more preferably comprising oxide particles.
The shape and size of the inorganic particles are also not particularly limited, but preferably contain at least one selected from nanoparticles, hollow particles and porous particles, and more preferably contain nanoparticles.

As the inorganic particles, a single inorganic particle may be used, or two or more kinds of inorganic particles may be used in combination. When two or more kinds of inorganic particles having different heat transfer suppressing effects are used in combination, the heating element can be cooled in multiple stages, and the endothermic action can be exhibited over a wider temperature range.
It is also preferable to use a mixture of large-diameter particles and small-diameter particles as the inorganic particles. When the small-diameter inorganic particles enter the gaps between the large-diameter inorganic particles, the structure becomes more dense, and the heat transfer suppressing effect can be improved.

When the average secondary particle size of the inorganic particles is 0.01 μm or more, it is easy to obtain, and it is possible to suppress an increase in manufacturing cost. Moreover, a desired heat insulation effect can be obtained as it is 200 micrometers or less. Therefore, the average secondary particle size of the inorganic particles is preferably 0.01 μm or more and 200 μm or less, more preferably 0.05 μm or more and 100 μm or less.

Next, an example of the material or shape of particles that can be used as inorganic particles will be described in detail below.

(1-1-1-1. Oxide particles)
Since oxide particles have a high refractive index and a strong effect of diffusely reflecting light, the use of oxide particles as the inorganic particles can suppress radiative heat transfer, especially in a high temperature range such as abnormal heat generation. As the oxide particles, at least one kind of particles selected from silica, titania, zirconia, zircon, barium titanate, zinc oxide and alumina can be used. That is, among the oxide particles that can be used as inorganic particles, only one kind may be used, or two or more kinds of oxide particles may be used. In particular, silica is a component with high heat insulation, and titania is a component with a higher refractive index than other metal oxides, and has the effect of blocking radiant heat by diffusely reflecting light in a high temperature range of 500 ° C or higher. It is most preferred to use silica and titania as the oxide particles due to their high.

(Average primary particle diameter of oxide particles: 0.001 μm or more and 50 μm or less)
Since the particle size of oxide particles may affect the effect of reflecting radiant heat, limiting the average primary particle size to a predetermined range makes it possible to obtain even higher heat insulation.
That is, when the average primary particle diameter of the oxide particles is 0.001 μm or more, it is sufficiently larger than the wavelength of light that contributes to heating, and the light is efficiently diffusely reflected. Radiation heat transfer of heat inside is suppressed, and heat insulation can be further improved.
On the other hand, when the average primary particle diameter of the oxide particles is 50 μm or less, the number of contact points between particles does not increase even when compressed, and it is difficult to form paths for conductive heat transfer, so conductive heat transfer is particularly dominant. It is possible to reduce the influence on heat insulation in the normal temperature range.

When two or more kinds of oxide particles are used, it is also preferable to use a mixture of large-diameter particles and small-diameter particles (nanoparticles). more preferably 5 μm or more and 30 μm or less, and most preferably 10 μm or less.
In the present invention, the average primary particle size can be determined by observing particles under a microscope, comparing with a standard scale, and averaging 10 arbitrary particles.

(1-1-1-2. Nanoparticles)
In the present invention, nanoparticles refer to nanometer-order particles having an average primary particle diameter of less than 1 μm and having a spherical or nearly spherical shape. Since nanoparticles have a low density, conductive heat transfer is suppressed, and when nanoparticles are used as inorganic particles, voids are dispersed more finely, so that excellent heat insulation properties that suppress convective heat transfer can be obtained. For this reason, it is preferable to use nanoparticles because heat conduction between adjacent nanoparticles can be suppressed when the battery is normally used in the normal temperature range.

In the present invention, at least one of oxide particles, carbide particles, nitride particles and inorganic hydrate particles selected as inorganic particles is preferably nanoparticles.
Furthermore, when nanoparticles with a small average primary particle size are used as the oxide particles, the heat transfer suppressing sheet is compressed due to expansion due to thermal runaway of the battery cell, and even if the internal density increases, the insulating material can suppress the increase in conductive heat transfer. This is presumably because fine voids are likely to be formed between nanoparticles due to the repulsive force of static electricity, and the particles are packed so as to have cushioning properties due to their low bulk density.

In the present invention, when nanoparticles are used as the inorganic particles, the material is not particularly limited as long as it conforms to the above definition of nanoparticles. For example, in addition to being a material with high heat insulating properties, silica nanoparticles have small contact points between particles, so the amount of heat conducted by silica nanoparticles is smaller than when silica particles with a large particle size are used. Become. In addition, generally available silica nanoparticles have a bulk density of about 0.1 g/cm ³ , so for example, the battery cells arranged on both sides of the heat transfer suppressing sheet thermally expand, and the heat transfer suppressing sheet On the other hand, even when a large compressive stress is applied, the size (area) and number of contact points between silica nanoparticles do not significantly increase, and heat insulating properties can be maintained. Therefore, it is preferable to use silica nanoparticles as the nanoparticles. As silica nanoparticles, wet silica, dry silica, aerogel, and the like can be used.

As mentioned above, titania is highly effective in blocking radiant heat, and silica nanoparticles have extremely low conductive heat transfer, and can maintain excellent thermal insulation even when compressive stress is applied to the insulating material. Most preferably, both titania and silica nanoparticles are used as inorganic particles.

(Average primary particle size of nanoparticles: 1 nm or more and 100 nm or less)
By limiting the average primary particle size of the nanoparticles to a predetermined range, even higher heat insulating properties can be obtained.
That is, when the average primary particle diameter of the nanoparticles is 1 nm or more and 100 nm or less, it is possible to suppress the convective heat transfer and conductive heat transfer of heat in the heat insulating material, especially in the temperature range of less than 500 ° C., and the heat insulating property is further improved. It can be improved further. In addition, even when compressive stress is applied, voids remaining between nanoparticles and contact points between many particles suppress conductive heat transfer, and the heat insulating properties of the heat insulating material can be maintained.
The average primary particle size of the nanoparticles is more preferably 2 nm or more, and even more preferably 3 nm or more. On the other hand, the average primary particle size of the nanoparticles is more preferably 50 nm or less, even more preferably 10 nm or less.

(1-1-1-3. Inorganic hydrate particles)
When the inorganic hydrate particles receive heat from the heating element and reach a thermal decomposition initiation temperature or higher, they thermally decompose, releasing their own water of crystallization to lower the temperature of the heating element and its surroundings, a so-called "endothermic effect". express. In addition, after the water of crystallization is released, it becomes a porous body and exhibits heat insulating properties due to its numerous air holes.
Specific examples of inorganic hydrates include aluminum hydroxide (Al(OH) ₃ ), magnesium hydroxide (Mg(OH) ₂ ), calcium hydroxide (Ca(OH) ₂ ), zinc hydroxide (Zn(OH) ₂ ), iron hydroxide (Fe(OH) ₂ ), manganese hydroxide (Mn(OH) ₂ ), zirconium hydroxide (Zr(OH) ₂ ), gallium hydroxide (Ga(OH) ₃ ), and the like. .

For example, aluminum hydroxide has about 35% water of crystallization, and as shown in the following formula, it is thermally decomposed to release water of crystallization to exhibit endothermic action. After releasing the water of crystallization, it becomes porous alumina (Al ₂ O ₃ ) and functions as a heat insulating material.
_2Al (OH) ₃ → _Al2O3 + _3H2O

As will be described later, the assembled battery of the present invention has the heat transfer suppressing sheet 10 interposed between the battery cells. The temperature continues to rise until Therefore, the inorganic particles are preferably composed of an inorganic hydrate having a thermal decomposition initiation temperature of 200° C. or higher.
The thermal decomposition initiation temperature of the inorganic hydrates listed above is about 200 ° C. for aluminum hydroxide, about 330 ° C. for magnesium hydroxide, about 580 ° C. for calcium hydroxide, about 200 ° C. for zinc hydroxide, and about 200 ° C. for iron hydroxide. is about 350°C, manganese hydroxide is about 300°C, zirconium hydroxide is about 300°C, and gallium hydroxide is about 300°C. It can be said that it is a preferable inorganic hydrate because it overlaps and can efficiently suppress the temperature rise.

Also, when inorganic hydrate particles are used as the inorganic particles, if the average particle size is too large, the inorganic particles (inorganic hydrate) near the center of the heat insulating material will be heated until they reach their thermal decomposition temperature. Since it takes a certain amount of time to complete the thermal decomposition, the inorganic particles near the center of the heat insulating material may not be completely thermally decomposed. Therefore, the average secondary particle size of the inorganic hydrate particles is preferably 0.01 μm or more and 200 μm or less, more preferably 0.05 μm or more and 100 μm or less.

<1-1-2. First inorganic fiber>
The first inorganic fibers are amorphous fibers, and the second inorganic fibers are at least one selected from amorphous fibers having a higher glass transition point than the first inorganic fibers and crystalline fibers. It is a fiber consisting of The melting point of crystalline inorganic fibers is generally higher than the glass transition point of amorphous inorganic fibers. Therefore, when the first inorganic fiber is exposed to a high temperature, its surface softens earlier than the second inorganic fiber, and binds the inorganic particles and the second inorganic fiber. can be improved.
Specifically, inorganic fibers having a melting point of less than 700° C. are preferable as the first inorganic fibers, and many amorphous inorganic fibers can be used. Among them, fibers containing SiO ₂ are preferable, and glass fibers are more preferable because they are inexpensive, readily available, and excellent in handleability.

<1-1-3. Second inorganic fiber>
As described above, the second inorganic fibers are fibers made of at least one selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers and crystalline fibers. Many crystalline inorganic fibers can be used as the second inorganic fibers.
When the second inorganic fibers are crystalline fibers or have a higher glass transition point than the first inorganic fibers, the first inorganic fibers soften when exposed to high temperatures. However, the second inorganic fibers do not melt or soften. Therefore, it is possible to maintain the shape and continue to exist between the battery cells even during thermal runaway of the battery cells.
In addition, if the second inorganic fibers are not melted or softened, there will be Since a small space is maintained in the space, the heat insulating effect of the air is exhibited, and excellent heat transfer suppressing performance can be maintained.

When the second inorganic fiber is crystalline, the second inorganic fiber includes ceramic fibers such as silica fiber, alumina fiber, alumina silicate fiber and zirconia fiber, rock wool, alkaline earth silicate fiber, zirconia. fibers, mineral fibers such as potassium titanate fibers and wollastonite;
Among the fibers exemplified as the second inorganic fibers, if the melting point exceeds 1000 ° C., even if the thermal runaway of the battery cell occurs, the second inorganic fibers will not melt or soften, and the shape will not change. Since it can be maintained, it can be preferably used.
Among the fibers mentioned as the second inorganic fibers, it is more preferable to use, for example, silica fibers, ceramic fibers such as alumina fibers and alumina silicate fibers, and mineral fibers, among which the melting point is 1000. It is more preferable to use those above °C.
Even if the second inorganic fiber is amorphous, it can be used as long as it has a glass transition point higher than that of the first inorganic fiber. For example, a glass fiber having a glass transition point higher than that of the first inorganic fiber may be used as the second inorganic fiber.
As the second inorganic fiber, various inorganic fibers exemplified may be used alone, or two or more kinds may be used in combination.

As described above, the first inorganic fiber has a lower glass transition point than the second inorganic fiber, and when exposed to high temperature, the first inorganic fiber softens first. can bind the inorganic particles and the second inorganic fibers. However, for example, when the second inorganic fiber is amorphous and its fiber diameter is smaller than the fiber diameter of the first inorganic fiber, the glass transition between the first inorganic fiber and the second inorganic fiber If the points are close together, the second inorganic fiber may soften first.
Therefore, when the second inorganic fibers are amorphous fibers, the glass transition point of the second inorganic fibers is preferably 100° C. or more higher than the glass transition point of the first inorganic fibers, and preferably 300° C. more preferably higher than

(Average fiber diameter of inorganic fibers)
In the present invention, inorganic fibers having a large average fiber diameter (thick diameter) have the effect of improving the mechanical strength and shape retention of the heat insulating material. By increasing the diameter of either the first inorganic fiber or the second inorganic fiber, the above effect can be obtained. Since the heat transfer suppressing sheet may be subject to impact from the outside, impact resistance is enhanced by including large-diameter inorganic fibers. The impact from the outside includes, for example, pressing force due to expansion of the battery cell, wind pressure due to ignition of the battery cell, and the like.
Further, in order to improve the mechanical strength and shape retention of the heat insulating material, it is particularly preferable that the large-diameter inorganic fibers are linear or needle-like. The linear or needle-like fibers refer to fibers having a degree of crimp of less than 10%, preferably 5% or less, which will be described later.

More specifically, in order to improve the mechanical strength and shape retention of the heat insulating material, the average fiber diameter of the large-diameter inorganic fibers is preferably 1 μm or more, more preferably 3 μm or more. However, if the thick inorganic fibers are too thick, the moldability and processability of the heat insulating material may be deteriorated. Therefore, the average fiber diameter is preferably 20 μm or less, more preferably 15 μm or less.
It should be noted that the fiber length is preferably 100 mm or less because there is a risk that the moldability and processability of the large-diameter inorganic fiber will be lowered if the fiber length is too long. Further, if the inorganic fiber having a large diameter is too short, the shape retention and mechanical strength are lowered, so the fiber length is preferably 0.1 mm or more.

On the other hand, inorganic fibers having a small average fiber diameter (thin diameter) have the effect of improving the retention of inorganic particles and increasing the flexibility of the heat insulating material. Therefore, by reducing the diameter of the other of the first inorganic fibers and the second inorganic fibers, the above effect can be obtained.

More specifically, in order to improve the holding property of the inorganic particles, it is preferable that the small-diameter inorganic fibers are easily deformable and have flexibility. Therefore, the fine inorganic fibers preferably have an average fiber diameter of less than 1 μm, more preferably 0.1 μm or less. However, if the fine-diameter inorganic fibers are too fine, they are likely to break, resulting in a decrease in the ability to retain the inorganic particles. In addition, the proportion of the fibers remaining entangled in the heat insulating material without retaining the inorganic particles increases, and in addition to the decrease in the ability to retain the inorganic particles, the moldability and shape retention are also deteriorated. Therefore, the average fiber diameter of the fine inorganic fibers is preferably 1 nm or more, more preferably 10 nm or more.
It should be noted that the fiber length of fine inorganic fibers is preferably 0.1 mm or less, because if the fiber length is too long, the moldability and shape retention deteriorate.

In addition, the small-diameter inorganic fibers are preferably dendritic or crimped. When the small-diameter inorganic fibers have such a shape, they are entangled with the large-diameter inorganic fibers and inorganic particles in the heat insulating material. Therefore, the ability to retain the inorganic particles is improved. In addition, when the insulating material is subjected to pressing force or wind pressure, the small inorganic fibers are prevented from sliding, and this improves the mechanical strength, especially against external pressing force and impact. do.

The dendritic structure is a two-dimensionally or three-dimensionally branched structure, and includes, for example, a feather shape, a tetrapod shape, a radial shape, and a three-dimensional network shape.
When the fine-diameter inorganic fibers are dendritic, the average fiber diameter can be obtained by measuring the diameters of the trunk and branch portions at several points by SEM and calculating the average value thereof.

Moreover, the crimped shape is a structure in which the fibers are bent in various directions. As one of the methods for quantifying the crimped form, it is known to calculate the degree of crimp from an electron micrograph. For example, it can be calculated from the following formula.
Crimp degree (%) = (fiber length - distance between fiber ends) / (fiber length) x 100
Here, both the fiber length and the distance between fiber ends are measured values on an electron micrograph. That is, the fiber length and the distance between fiber ends projected onto a two-dimensional plane are shorter than the actual values. Based on this formula, the degree of crimp of fine inorganic fibers is preferably 10% or more, more preferably 30% or more. If the degree of crimping is small, the ability to retain inorganic particles and the entanglement (network) between large-diameter inorganic fibers and between large-diameter inorganic fibers are difficult to form.

As described above, it is preferable that the average fiber diameter of one of the first inorganic fibers and the second inorganic fibers is larger than the average fiber diameter of the other. More preferably, the average fiber diameter is larger than the average fiber diameter of the second inorganic fibers. When the average fiber diameter of the first inorganic fibers is large, the glass transition point of the first inorganic fibers is low and softens quickly. On the other hand, when the average fiber diameter of the second inorganic fibers is small, the small-diameter second inorganic fibers remain in the form of fibers even when the temperature rises, so that the structure of the heat insulating material is maintained and the powder It can prevent falling.

As the first inorganic fiber, both a large-diameter linear or acicular inorganic fiber and a small-diameter dendritic or crimped inorganic fiber are used. As fibers, if both a large-diameter linear or needle-like inorganic fiber and a small-diameter dendritic or crimped inorganic fiber are used, the effect of holding inorganic particles and the mechanical strength And it is most preferable because it can further improve the shape retention.

(Each content of inorganic particles, first inorganic fibers, and second inorganic fibers)
The content of the inorganic particles is preferably 30% by mass or more and 94% by mass or less with respect to the total mass of the heat insulating material, and the content of the first inorganic fiber is 3% with respect to the total mass of the heat insulating material. The content of the second inorganic fibers is preferably 3% by mass or more and 30% by mass or less with respect to the total mass of the heat insulating material.

More preferably, the content of the inorganic particles is 60% by mass or more and 90% by mass or less, and the content of the first inorganic fibers is 5% by mass or more and 15% by mass or less, relative to the total mass of the heat insulating material. and the content of the second inorganic fibers is 5% by mass or more and 15% by mass or less. By setting such a content, the heat absorption and heat insulation effect of the inorganic particles, the shape retention and pressure resistance of the first inorganic fibers, the resistance to wind pressure, and the ability to retain the inorganic particles of the second inorganic fibers are balanced. well expressed.

<1-1-4. Other Compounding Materials>
Organic fibers, organic binders, and the like can be added to the heat insulating material, if necessary. All of these are useful for the purpose of reinforcing the heat insulating material and improving moldability, and the total amount is preferably 10% by mass or less with respect to the total mass of the heat insulating material.

<1-2. First Resin Film>
The first resin film encloses and seals at least the heat insulating material, and can prevent particles, which are materials constituting the heat insulating material, from falling off.
The material constituting the first resin film is selected from polyethylene, polypropylene, polystyrene, nylon, acrylic, epoxy resin, polyurethane, polyetheretherketone, polyetherimide, polyethyleneterephthalate, polyphenylsulfide, polycarbonate and aramid. At least one resin can be selected.

As described above, the first resin film preferably has an appropriate thickness because it covers the outer surface of the heat insulating material and has the effect of preventing particles and the like from falling off. Further, as shown in FIGS. 1 and 3, when the first resin film laminated in the thickness direction of the heat insulating material is bent along the shape of the heat insulating material, the first resin film preferably have appropriate flexibility.
When the thickness of the first resin film exceeds 1 mm, it becomes difficult to conform to the shape of the heat insulating material, and cracks and breakage may occur. Therefore, the thickness of the first resin film is preferably 1 mm or less, more preferably 0.1 mm or less, and even more preferably 0.05 mm or less.
On the other hand, the lower limit of the thickness of the first resin film is not particularly limited. is more preferable.

Moreover, since the first resin film is in contact with the battery cells, it preferably has flame retardancy, and specifically, preferably contains an inorganic substance or a flame retardant material. Examples of inorganic substances contained in the first resin film as materials constituting the first resin film include talc, calcium carbonate, aluminum hydroxide, titanium oxide, vermiculite, zeolite, synthetic silica, zirconia, zircon, barium titanate, Zinc oxide and alumina may be mentioned, and flame retardants may include brominated flame retardants, chlorine flame retardants, phosphorus flame retardants, boron flame retardants, silicone flame retardants, and nitrogen-containing compounds.

<1-3. Intermediate layer>
The intermediate layer 3 used in the heat transfer suppressing sheet according to the present embodiment includes a heat diffusion sheet 5 having a higher thermal conductivity than the heat insulating material, and a second resin film 6 laminated on both sides of the heat diffusion sheet 5. , and the heat diffusion sheet 5 has the effect of diffusing heat in the surface direction.

(1-3-1. Thermal diffusion sheet)
As the heat diffusion sheet 5, specifically, aluminum or aluminum alloy, copper or copper alloy, tin or tin alloy, nickel or nickel alloy, stainless steel, lead or lead alloy, bronze, iridium, phosphor bronze, silver or silver alloy , titanium or titanium alloys, ceramics, graphite and diamond-like carbon.
Also, when ceramic is used as the thermal diffusion sheet, at least one selected from AlN, SiC, BN and TiN can be used as the ceramic.

(1-3-2. Second resin film)
As described above, the second resin film 6 protects the surface of the thermal diffusion sheet 5 made of an easily oxidizable metal, suppresses the formation of an oxide film, and maintains the effect of diffusing heat in the plane direction. can do. Further, when the second resin film 6 and the heat diffusion sheet 5 are integrated, the first resin film 4 and the second resin film 6 are bonded by a simple bonding method such as heat sealing. Therefore, the heat transfer suppressing sheets 10 and 12 having the configurations shown in the first and second embodiments can be easily manufactured.

The material constituting the second resin film is selected from polyethylene, polypropylene, polystyrene, nylon, acrylic, epoxy resin, polyurethane, polyetheretherketone, polyetherimide, polyethyleneterephthalate, polyphenylsulfide, polycarbonate and aramid. At least one resin can be selected. The second resin film may be made of the same material as the first resin film, or may be made of a different material.

Since the second resin film is laminated with the heat diffusion sheet (for example, a metal film) to constitute an intermediate layer or a functional film, if the thickness of the second resin film is too thin, the second resin film A space may be created between the heat insulating material 2 and the functional film by tearing or peeling off from the heat diffusion sheet or the heat insulating material 2, and heat conduction to the functional film may be hindered. Therefore, the thickness of the second resin film is preferably 5 μm or more, more preferably 10 μm or more, and more preferably 20 μm or more.
On the other hand, if the thickness of the second resin film is too thick, the amount of organic matter in the second resin film increases, resulting in a decrease in flame retardancy. Therefore, the thickness of the second resin film is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 25 μm or less.

In addition, although the second resin film does not come into contact with the battery cells, it may be exposed to high temperatures due to thermal runaway of the battery cells. Like the film, it preferably contains an inorganic or flame retardant material. Inorganic substances include talc, calcium carbonate, aluminum hydroxide, titanium oxide, vermiculite, zeolite, synthetic silica, zirconia, zircon, barium titanate, zinc oxide, and alumina. Flame retardants include brominated flame retardants, Chlorine-based flame retardants, phosphorus-based flame retardants, boron-based flame retardants, silicone-based flame retardants, and nitrogen-containing compounds.

Furthermore, the second resin film preferably contains an insulating conductive filler as a material. Conductive fillers and insulating fillers are conceivable as high thermal conductivity materials, and there is no problem in using either of them. However, for applications between battery cells, it is more preferable to use insulating fillers. A high thermal conductivity filler is a material in which a high thermal conductivity inorganic (insulating) filler is dispersed in a resin film. Examples of high thermal conductivity inorganic fillers include boron nitride, aluminum nitride, silicon carbide, and silicon nitride. mentioned.
When the second resin film contains a high thermal conductive material filler, if the thermal conductivity of the second resin film is too higher than that of the heat diffusion sheet 5, the heat transfer does not proceed in the desired direction. 2 There is a possibility that the heat will be trapped in the film. Therefore, it is preferable that the thermal conductivity of the second resin film is lower than that of the thermal diffusion sheet 5 .
On the other hand, if the thermal conductivity of the second resin film is too low, the heat generated from the battery cells will be less likely to reach the heat diffusion sheet. m·K) or more, more preferably 0.5 (W/m·K) or more, and even more preferably 1.0 (W/m·K) or more.

The first resin film and the second resin film may have the same thickness, but when the heat transfer suppressing member has a shape as shown in FIG. Since the film has a shape that follows the surface of the heat insulating material, the thickness of the first resin film is preferably thinner than the thickness of the second resin film.
In addition, since the heat generated from the battery cells reaches the heat insulating material through the first resin film, the first resin film may have heat insulating properties like the heat insulating material. may be about the same as the thermal conductivity of However, if the thermal conductivity of the second resin film is low, the heat does not reach the heat diffusion sheet, making it difficult to radiate the heat in the plane direction of the heat diffusion sheet. Therefore, the thermal conductivity of the first resin film and the second resin film may be the same, but the thermal conductivity of the first resin film is lower than the thermal conductivity of the second resin film. is preferred.

Next, a method for manufacturing the heat transfer suppressing sheet according to this embodiment will be described.

[2. Method for manufacturing heat transfer suppressing sheet]
The heat transfer suppression sheet according to this embodiment can be manufactured, for example, by the following method.
First, a pair of heat insulating materials, a pair of first resin films having a size larger than a plane perpendicular to the thickness direction of the heat insulating materials, and an intermediate layer are prepared. Next, the first resin film/heat insulating material/intermediate layer/heat insulating material/first resin film are laminated in this order. After that, the heat transfer suppressing sheet can be obtained by bonding the first resin film and the intermediate layer at the peripheral edge portion extending from the heat insulating material.

In addition, as shown in the second embodiment, when the heat transfer suppressing sheet is configured by a pair of heat transfer suppressing members, the pair of heat insulating materials and the size larger than the surface orthogonal to the thickness direction of the heat insulating materials A pair of first resin film and functional film are prepared. As a functional film, a laminate of a heat diffusion sheet and a second resin film is prepared. Next, the functional film and the first resin film are arranged such that the second resin film of the functional film faces the first resin film, and one heat insulating material is arranged between them. After that, the heat transfer suppressing member is produced by bonding the first resin film and the functional film at the peripheral portion extending from the heat insulating material. After that, the heat transfer suppressing sheet can be obtained by combining the other heat transfer suppressing member prepared in the same manner so that the heat diffusion sheets in the functional film are brought into contact with each other.

Further, the peripheral edge portion of the first resin film and the intermediate layer or the peripheral edge portion of the first resin film and the functional film are bonded by heat sealing or the like with only a part left to form a bag shape, A heat transfer suppressing sheet can also be manufactured by bonding the unbonded portions after inserting a heat insulating material into the interior thereof. According to such a method, it is possible to enclose a heat insulating material in the form of a powder, particles, fibers, etc., in addition to the heat insulating material processed into a sheet or plate. As a result, the materials forming the heat insulating material can be easily adjusted according to various requirements, and the degree of freedom in designing the heat insulating material can be improved.

(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. When the thickness of the heat transfer suppressing sheet is 0.05 mm or more, sufficient mechanical strength can be imparted to the heat transfer suppressing sheet. On the other hand, when the thickness of the heat transfer suppressing sheet is 6 mm or less, it is possible to obtain good assembling performance.

[3. Batteries]
An assembled battery according to an embodiment of the present invention comprises a battery case, a plurality of battery cells housed inside the battery case and connected in series or in parallel, and the above [1. Heat transfer suppression sheet].
Further, an assembled battery according to another embodiment of the present invention includes a battery case, a plurality of battery cells stored in the battery case and connected in series or in parallel, and heat interposed between the plurality of battery cells. It has a transfer suppression sheet and a heat transfer member provided between the plurality of battery cells and the battery case. Then, as shown in FIG. 2, the end face of the heat diffusion sheet 5 and the heat transfer member 21 are in contact with each other at the projecting portion 1a.

[1. heat transfer suppression sheet], when heat is generated from one battery cell, the heat transfer is reduced by the heat insulating material, and the heat diffusion sheet spreads the heat in the planar direction. Heat is diffused and released. Therefore, heat propagation between battery cells can be suppressed, and a chain of thermal runaway can be prevented.
Further, when the end surface of the heat diffusion sheet and the heat transfer member are in contact with each other at the projecting portion, heat can be more efficiently released through the heat transfer member 21 .

Although illustration is omitted, the above [1. Heat transfer suppression sheet] can be arranged not only between a plurality of battery cells, but also between a battery cell and a battery case. Therefore, high versatility is obtained, and not only is there an effect of preventing a chain of thermal runaway due to heat transfer between adjacent battery cells, but if a certain battery cell ignites, the battery will not reach the outside of the battery case. It can prevent the spread of fire.

For example, the assembled battery according to the present embodiment is used in an electric vehicle (EV) or the like, and may be placed under the floor of a passenger. In this case, even if the battery cell catches fire, the safety of the passenger can be ensured.
In this case, the heat transfer suppression sheet or the like interposed between the battery cells can also be placed between the battery cell and the battery case, so there is no need to prepare a new flameproof material, etc. A low-cost and safe assembled battery can be easily constructed.

1a, 11a protruding portion 2 heat insulating material 3 intermediate layer 4 first resin film 5 heat diffusion sheet 6 second resin film 10, 12 heat transfer suppressing sheet 11 heat transfer suppressing member 13 functional films 20a, 20b, 20c battery cell 21 heat transfer member 30 battery case 100 assembled battery

Claims (21)

A heat transfer suppression sheet used in an assembled battery in which a plurality of battery cells are connected in series or in parallel,
a pair of heat insulating materials laminated in the thickness direction;
an intermediate layer disposed between the pair of heat insulating materials;
a first resin film that encloses and seals at least the heat insulating material;
The intermediate layer includes a heat diffusion sheet having a higher thermal conductivity than the heat insulating material,
and a second resin film laminated on both sides perpendicular to the thickness direction of the heat diffusion sheet. At least one of the end faces parallel to the thickness direction of the intermediate layer protrudes from the pair of heat insulating materials, and the intermediate layer forms a protruding portion together with the first resin film. The heat transfer suppressing sheet according to claim 1. At all end faces parallel to the thickness direction of the intermediate layer, the intermediate layer protrudes from the pair of heat insulating materials, and forms a protrusion together with the first resin film. The heat transfer suppressing sheet according to claim 2. 4. The heat transfer suppressing sheet according to claim 2, wherein an end face of said heat diffusion sheet at said projecting portion is exposed. The heat transfer according to any one of claims 1 to 4, wherein the intermediate layer is a film in which the second resin film is laminated on both sides of the heat diffusion sheet and integrated. suppression sheet. 6. The heat transfer suppressing sheet according to claim 5, wherein the intermediate layer is a laminate film. The heat insulating material is enclosed and sealed between the first resin film and the second resin film by thermally bonding the first resin film and the second resin film. The heat transfer suppressing sheet according to any one of claims 1 to 6, characterized in that The first resin film and the second resin film are made of the same material or different materials, and are polyethylene, polypropylene, polystyrene, nylon, acrylic, epoxy resin, polyurethane, polyetheretherketone, The heat transfer suppressing sheet according to any one of claims 1 to 7, comprising at least one resin selected from polyetherimide, polyethylene terephthalate, polyphenyl sulfide, polycarbonate and aramid. 9. The heat transfer suppressing sheet according to claim 8, wherein the first resin film and the second resin film are made of the same material. The heat transfer suppressing sheet according to any one of claims 1 to 9, wherein the first resin film has a thickness of 1 mm or less. The heat transfer suppressing sheet according to any one of claims 1 to 10, wherein the second resin film has a thickness of 5 µm or more and 100 µm or less. The heat transfer suppressing sheet according to any one of claims 1 to 11, wherein the thickness of the first resin film is thicker than the thickness of the second resin film. The heat diffusion sheet is made of aluminum or an aluminum alloy, copper or a copper alloy, tin or a tin alloy, nickel or a nickel alloy, stainless steel, lead or a lead alloy, bronze, iridium, phosphor bronze, silver or a silver alloy, titanium or a titanium alloy. 13. The heat transfer suppressing sheet according to any one of claims 1 to 12, comprising at least one selected from , ceramic, graphite and diamond-like carbon. 14. The heat transfer suppressing sheet according to claim 13, wherein the ceramic is at least one selected from AlN, SiC, BN and TiN. The heat transfer suppressing sheet according to any one of claims 1 to 14, wherein the thermal conductivity of the heat insulating material is less than 1 (W/m·K). The heat transfer suppressing sheet according to any one of claims 1 to 15, wherein the heat insulating material contains at least one selected from inorganic fibers, organic fibers, inorganic particles and organic particles. The heat insulating material includes inorganic particles, first inorganic fibers, and second inorganic fibers,
The first inorganic fibers are amorphous fibers,
17. The method according to claim 16, wherein the second inorganic fibers are made of at least one selected from amorphous fibers having a glass transition point higher than that of the first inorganic fibers and crystalline fibers. The heat transfer suppressing sheet described. The heat insulating material includes silica nanoparticles, titania, alumina fibers, carbon fibers, mica, basalt fibers, soluble fibers, refractory ceramic fibers, glass fibers, airgel composites, microporous particles, hollow silica particles, and thermally expandable inorganic materials. , aerogel, silica, zirconia, zircon, barium titanate, zinc oxide, alumina, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, zinc hydroxide, iron hydroxide, manganese hydroxide, zirconium hydroxide, gallium hydroxide, 16. It contains at least one selected from fibers containing _SiO2 , silica fibers, alumina fibers, ceramic fibers, rock wool, alkaline earth silicate fibers, zirconia fibers, and mineral fibers. Or the heat transfer suppressing sheet according to 17. The heat transfer suppressing sheet according to any one of claims 1 to 18, which is interposed between the plurality of battery cells. a battery case;
a plurality of battery cells stored in the battery case and connected in series or in parallel;
and a heat transfer suppressing sheet according to any one of claims 1 to 18 interposed between the plurality of battery cells. a battery case;
a plurality of battery cells stored in the battery case and connected in series or in parallel;
a heat transfer suppression sheet according to claim 4 interposed between the plurality of battery cells;
a heat transfer member provided between the plurality of battery cells and the battery case;
has
An assembled battery, wherein an end surface of the heat diffusion sheet and the heat transfer member are in contact with each other in the projecting portion.

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