WO2019088195A1

WO2019088195A1 - Heat insulation sheet for battery pack, and battery pack

Info

Publication number: WO2019088195A1
Application number: PCT/JP2018/040577
Authority: WO
Inventors: 直己高橋; 清成畑中; 寿安藤
Original assignee: イビデン株式会社
Priority date: 2017-10-31
Filing date: 2018-10-31
Publication date: 2019-05-09
Also published as: JP7074455B2; JP2019083150A

Abstract

Provided is a heat insulation sheet for a battery pack, the heat insulation sheet being capable of effectively suppressing heat propagation between respective battery cells, when a battery pack is configured in which a plurality of battery cells are connected in series or in parallel. This heat insulation sheet (10), through which a plurality of battery cells are disposed and which is used for a battery pack configured by connecting the plurality of battery cells in series or in parallel, has: a heat insulation layer (12) composed of at least an inorganic fiber or an inorganic powder; and heat absorption layers (14) formed on the both surfaces of the heat insulation layer (12) and composed of at least an inorganic hydrate.

Description

Thermal insulation sheet for assembled battery and assembled battery

The present invention relates to, for example, a heat insulating sheet for a battery pack, which is suitably used for a battery pack serving as a power source of an electric motor for driving an electric vehicle or a hybrid vehicle.

BACKGROUND ART In recent years, development of an electric car or a hybrid car driven by an electric motor has been actively promoted from the viewpoint of environmental protection. In the electric car or the hybrid car, etc., there is mounted a battery pack in which a plurality of battery cells are connected in series or in parallel to be a power source of a driving electric motor.

This battery cell mainly uses a lithium ion secondary battery capable of high capacity and high output compared to lead storage battery and nickel hydrogen battery etc., but due to internal short circuit and overcharge of the battery etc. When thermal runaway occurs in one battery cell, the propagation of heat to the other adjacent battery cells may cause thermal runaway of the other battery cells.

As a technique for suppressing the propagation of thermal runaway as described above, for example, Patent Document 1 describes a power storage device including one or more power storage elements, which is one of the one or more power storage elements. A first plate and a second plate disposed laterally of the first storage element, the first plate and the second plate being disposed such that the surfaces of the first plate and the second plate face each other; By forming a low thermal conductive layer (for example, an air layer) which is a layer of a substance having a thermal conductivity lower than that of the first plate and the second plate between the two plate members, the first storage element is formed. The radiation heat from the first storage element or the radiation heat toward the first storage element is blocked by the two plate members, and the heat transfer from one of the two plate members to the other is suppressed by the low heat conduction layer. Achieve effective insulation between the object and other objects It is disclosed that it is.

Japanese Patent Laid-Open Publication 2015-211013

However, in Patent Document 1 described above, although it is possible to suppress the radiation heat from a certain storage element or the radiation heat toward a certain storage element and the heat transfer between the two plate members by the low heat conduction layer, it becomes a heat source When the amount of heat generated from each storage element is large, it can not always be said that the heat insulation effect is sufficient.

The present invention has been made in view of such circumstances, and in forming a battery pack in which a plurality of battery cells are connected in series or in parallel, the propagation of heat between the battery cells is effectively suppressed. It is an object of the present invention to provide a heat insulating sheet for a battery pack that can be

In order to achieve the above object, the gist of the heat insulating sheet for a battery assembly according to one aspect of the present invention is a set in which a plurality of battery cells are disposed via a heat insulating sheet and the plurality of battery cells are connected in series or in parallel. A heat insulating sheet for use in a battery, comprising: a heat insulating layer comprising at least inorganic fibers or inorganic powder; and an endothermic layer formed on both surfaces of the heat insulating layer and comprising at least inorganic hydrate.

In a preferred embodiment of the above-mentioned heat insulation sheet for battery pack, the heat insulation layer has lower thermal conductivity than the heat absorption layer.

In a preferred embodiment of the above-mentioned heat insulation sheet for battery assembly, the inorganic powder has a refractive index ratio (relative refractive index) to light of a wavelength of 1 μm or more at 1.25 or more.

In a preferred embodiment of the above-mentioned heat insulation sheet for battery pack, the inorganic powder contains TiO ₂ powder or SiO ₂ powder.

In a preferred embodiment of the above heat insulation sheet for battery pack, the inorganic powder is scale-like particles having anisotropy in thermal conductivity, and the plane direction of the scale-like particles is perpendicular to the thickness direction of the heat insulation sheet. It is oriented in the direction.

In a preferred embodiment of the above-mentioned heat insulation sheet for battery assembly, the inorganic hydrate is at least one of aluminum hydroxide and magnesium hydroxide.

In a preferred embodiment of the above heat insulation sheet for battery pack, the inorganic fibers are at least one of silica-alumina fibers, alumina fibers, silica fibers, rock wool, Alkaline Earth Silicate (AES) fibers and glass fibers. It is.

Further, the gist of an assembled battery according to one aspect of the present invention is characterized in that a plurality of battery cells are disposed via the above-described heat insulating sheet for battery assembly, and the plurality of battery cells are connected in series or in parallel. I assume.

ADVANTAGE OF THE INVENTION According to the heat insulation sheet | seat for assembled batteries which concerns on this invention, when comprising the assembled battery in which several battery cells were connected in series or in parallel, the propagation of the heat between each battery cell can be suppressed effectively.

FIG. 1 is a cross-sectional view schematically showing a configuration of a heat insulation sheet for a battery assembly according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a configuration of a heat insulating sheet for battery assembly according to another embodiment of the present invention. FIG. 3: is sectional drawing which shows typically the structure of the assembled battery which applied the heat insulation sheet for assembled batteries which concerns on one Embodiment of this invention. FIG. 4 is a graph in which the temperature change of the adjacent battery cell surface is plotted against the elapsed time when the heat insulation sheets of Examples 1 to 3 and Comparative Examples 1 to 6 are heated by a heater.

The present inventors provide a heat insulating sheet for a battery pack capable of effectively suppressing the propagation of heat between battery cells even when the amount of heat generated from each storage element serving as a heat source is large. In order to do so, we have conducted intensive studies.

As a result, a heat insulating sheet comprising a heat insulating layer comprising at least inorganic fibers or inorganic powder as an intermediate layer, and a heat absorbing layer comprising at least inorganic hydrate formed on both surfaces thereof is disposed in a battery assembly It has been found that the above problems can be solved by interposing between the battery cells.

That is, when the inorganic hydrate in the endothermic layer which is the outer layer is heated by the heat generated in a certain battery cell, the inorganic hydrate absorbs the heat and releases the water. The heat absorption effect of the battery cell can be effectively reduced by this heat absorption action. And since the reduced heat can effectively suppress the propagation of heat between the battery cells by the heat insulating layer which is the intermediate layer, even if the amount of heat generated from the battery cells is large. , Sufficient insulation effect can be obtained. As a result, when thermal runaway occurs in one battery cell, it is possible to effectively suppress the propagation of heat to other adjacent battery cells, thereby suppressing the occurrence of thermal runaway in the other battery cells. Can.

In addition, since heat transfer is suppressed by the heat insulating layer after reducing the amount of heat generated in the battery cell, the thickness of the heat insulating layer is extreme unlike that using only the heat insulating layer to suppress heat transfer. There is no need to thicken. For this reason, it is possible to reduce the thickness of the whole heat insulating sheet (for example, 5 mm or less), and as a result, it is possible to improve the volumetric energy density of the assembled battery while securing the safety of the assembled battery. Become.

Hereinafter, an embodiment (this embodiment) of the present invention will be described in detail with reference to the drawings. In the following, “to” means that the value is not less than the lower limit value and not more than the upper limit value.

<Basic Configuration of Thermal Insulation Sheet for Battery Pack>
FIG. 1 is a cross-sectional view schematically showing a configuration of a heat insulation sheet for a battery assembly according to an embodiment of the present invention. The heat insulating sheet 10 for a battery assembly according to the present embodiment has a heat insulating layer 12 containing at least inorganic fibers or inorganic powder as an intermediate layer, and a double layer in which the heat absorbing layer 14 made of at least inorganic hydrate is formed on both surfaces thereof. It consists of (laminated structure).

The heat insulating layer 12 is made of at least an inorganic fiber or an inorganic powder, and suppresses the transfer of heat generated in one battery cell to another adjacent battery cell. Also, the thermal conductivity of the heat insulating layer 12 is lower than the thermal conductivity of the endothermic layer 14.

The endothermic layer 14 is made of at least an inorganic hydrate, and when the inorganic hydrate in the endothermic layer is heated by the heat generated by a battery cell, the inorganic hydrate absorbs the heat and releases moisture. . This heat absorption action reduces the calorific value of the battery cell.

As described above, the heat insulating layer 12 having low thermal conductivity is provided as the intermediate layer, and the heat absorption layer 14 is disposed on both surfaces of the intermediate layer as the outer layer thereof, thereby reducing the amount of heat generated in the battery cell. The heat insulating layer 12 can suppress the propagation of heat, and can effectively suppress the propagation of heat to other adjacent battery cells.

As a specific usage of the heat insulation sheet 10 for a battery pack, as shown in FIG. 3, a plurality of battery cells 20 are disposed via the heat insulation sheet 10 for a battery pack, and the plurality of battery cells 20 are in series. Alternatively, the battery assembly 30 is configured to be stored in the battery case 30 in a state of being connected in parallel (the connected state is not shown). In addition, although the lithium ion secondary battery is used suitably, for example as the battery cell 20, it is not specifically limited to this.

<Details of thermal insulation sheet for battery pack>
Next, each component in the heat insulating sheet 10 for a battery assembly will be described in detail.

(Adiabatic layer)
The heat insulation layer 12 contains at least an inorganic fiber or an inorganic powder. That is, as a constituent material of the heat insulation layer 12, any one of inorganic fibers and inorganic powders may be included, and by including any one of these, it is possible to exhibit the effect as a heat insulation material. it can. However, by containing both the inorganic fiber and the inorganic powder, the inorganic powder can divide continuous voids in the structure formed by the intertwining of the inorganic fiber, so that the convective heat transfer in the heat insulating layer 12 is effectively made. It becomes possible to reduce and it can exhibit the heat insulation effect more effectively.

Examples of the inorganic fibers include silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkali earth silicate fibers, glass fibers, zirconia fibers and potassium titanate whisker fibers. These inorganic fibers are preferable in terms of heat resistance, strength, and availability. The inorganic fibers may be used alone or in combination of two or more. Among the above-mentioned inorganic fibers, in particular from the viewpoint of handleability, silica-alumina fibers, alumina fibers, silica fibers, rock wool, alkali earth silicate fibers and glass fibers are preferable.

The cross-sectional shape of the inorganic fiber is not particularly limited, and examples thereof include a circular cross-section, a flat cross-section, a hollow cross-section, a polygonal cross-section, and a core-sheath cross-section. Among them, a modified cross-section fiber having a hollow cross section, a flat cross section or a polygonal cross section can be suitably used because the heat insulation property is slightly improved.

The preferable lower limit of the average fiber length of the above-mentioned inorganic fiber is 0.1 mm, and the more preferable lower limit is 0.5 mm. On the other hand, the preferable upper limit of the average fiber length of the said inorganic fiber is 50 mm, and a more preferable upper limit is 10 mm. If the average fiber length of the inorganic fibers is less than 0.1 mm, entanglement of the inorganic fibers is unlikely to occur, and the mechanical strength of the resulting heat insulating layer 12 may be reduced. On the other hand, if it exceeds 50 mm, although the reinforcing effect can be obtained, the inorganic fibers can not be tightly intertwined, or only a single inorganic fiber is curled up, which makes it easy to form continuous voids, so it has thermal insulation. It may cause a decline.

The preferable lower limit of the average fiber diameter of the inorganic fiber is 1 μm, the more preferable lower limit is 2 μm, and the still more preferable lower limit is 3 μm. On the other hand, the preferable upper limit of the average fiber diameter of the said inorganic fiber is 10 micrometers, and a more preferable upper limit is 7 micrometers. If the average fiber diameter of the inorganic fiber is less than 1 μm, the mechanical strength of the inorganic fiber itself may be reduced. Further, from the viewpoint of the influence on the health of the human body, it is preferable that the average fiber diameter of the inorganic fiber is 3 μm or more. On the other hand, if the average fiber diameter of the above-mentioned inorganic fiber is larger than 10 μm, solid heat transfer with the inorganic fiber as a medium may increase to cause a decrease in heat insulation, and the formability of the heat insulation layer 12 may be deteriorated. There is.

Subsequently, examples of the inorganic powder include TiO ₂ powder, SiO ₂ powder, BaTiO ₃ powder, PbS powder, ZrO ₂ powder, SiC powder, NaF powder and LiF powder. These inorganic powders may be used alone or in combination of two or more.

When the above inorganic powders are used in combination, preferred combinations are a combination of TiO ₂ powder and SiO ₂ powder, a combination of TiO ₂ powder and BaTiO ₃ powder, a combination of SiO ₂ powder and BaTiO ₃ powder, or And combinations of TiO ₂ powder, SiO ₂ powder and BaTiO ₃ powder.

The TiO ₂ powder has a high refractive index to infrared rays, and has an effect of improving the heat insulation in a high temperature range. In addition, SiO ₂ powder has a low solid thermal conductivity, and it is easy to form fine voids with fine particles, so that it has an effect of suppressing the convection and improving the heat insulation in a low temperature range. Therefore, the combination of TiO ₂ powder and SiO ₂ powder can be expected to provide heat insulation in a wide temperature range from a low temperature range to a high temperature range, and a combination of these is particularly preferable.

Further, as shown in FIG. 2, using the scale-like particles 16 having anisotropy in thermal conductivity as the above-mentioned inorganic powder, the plane direction of the scale-like particles 16 is the thickness direction of the heat insulation sheet 10 for the assembled battery. It is preferable to orient in a direction perpendicular to (that is, in the thickness direction of the heat insulating layer 12). The scaly particles 16 made of inorganic powder have anisotropy in thermal conductivity, and the thermal conductivity of the scaly particles in the surface direction is very high compared to the thermal conductivity in the direction perpendicular to the surface direction. Excellent. For this reason, the heat propagation in the thickness direction of the heat insulation sheet 10 for the assembled battery is made more effective by orienting the surface direction of the scaly particles in the direction perpendicular to the thickness direction of the heat insulation sheet 10 for the assembled battery. Can be suppressed. Therefore, as shown in FIG. 3, when the battery assembly thermal insulation sheet 10 is interposed between a plurality of battery cells 20, the heat transfer from one battery cell 20 to another battery cell 20 is more effective. It is possible to Furthermore, by having the above configuration, the flexibility of the battery pack thermal insulation sheet 10 can be further enhanced.

When both inorganic fibers and inorganic powder are contained as a material which comprises the heat insulation layer 12, as a compounding quantity of the said inorganic fiber, a preferable upper limit is 50 mass% with respect to the total weight of the material which comprises the heat insulation layer 12 There is a further preferable upper limit is 40% by mass. On the other hand, the preferable minimum of the compounding quantity of the said inorganic fiber is 5 mass%, and a still more preferable minimum is 10 mass%. If the compounding amount is less than 5% by mass, the reinforcing effect by the inorganic fibers can not be obtained, and the handleability and mechanical strength of the heat insulating layer 12 may be reduced, and a good formability may not be obtained. . On the other hand, if the compounding amount exceeds 50% by mass, many continuous voids exist in the structure in which the inorganic fibers constituting the heat insulating layer 12 are intertwined, and convective heat transfer, molecular heat transfer and radiation heat transfer increase. Heat insulation properties may deteriorate.

When both inorganic fibers and inorganic powder are contained as a material which comprises the heat insulation layer 12, as a compounding quantity of the said inorganic powder, a preferable upper limit is 95 mass% with respect to the total weight of the material which comprises the heat insulation layer 12 A further preferable upper limit is 90% by mass. On the other hand, the preferable minimum of the compounding quantity of the said inorganic powder is 50 mass%, and a still more preferable minimum is 60 mass%. When the compounding amount of the inorganic powder is in the above range, a convective heat transfer reduction effect can be obtained by dividing continuous voids in the entangled structure of the inorganic fibers while maintaining the reinforcing effect by the inorganic fibers. .

The preferable lower limit of the average particle diameter of the inorganic powder is 0.5 μm, and the more preferable lower limit is 1 μm. On the other hand, the preferable upper limit of the average particle diameter of the inorganic powder is 20 μm, and the more preferable upper limit is 10 μm. If the average particle diameter of the inorganic powder is less than 0.5 μm, not only the production of the heat insulating layer 12 becomes difficult, but also the radiation heat scattering becomes insufficient, and the thermal conductivity of the heat insulating layer 12 increases (that is, the heat insulating property) May decrease). On the other hand, if the average particle diameter of the inorganic powder exceeds 20 μm, the air gaps formed in the heat insulating layer 12 become extremely large, so convective heat transfer and molecular heat transfer increase, and also in this case the thermal conductivity increases Resulting in.

The shape of the inorganic powder is not particularly limited as long as the average particle diameter is in the above range, and any shape such as a sphere, an ellipsoid, a polyhedron, or a shape or profile having irregularities or protrusions on the surface The shape of is mentioned.

Further, in the above-mentioned inorganic powder, it is preferable that the ratio of the refractive index to light with a wavelength of 1 μm or more (the relative refractive index) is 1.25 or more. The inorganic powder has a very important role as a scattering material of radiant heat, and the radiant heat can be scattered more effectively as the refractive index is larger. The relative refractive index is extremely important for the suppression of phonon conduction, and the larger the value, the better the suppression effect.

As materials capable of suppressing phonon conduction, generally, substances having lattice defects in crystals or substances having complex structures are known. The aforementioned TiO ₂ , SiO ₂ , and BaTiO ₃ tend to have lattice defects and have a complex structure, and therefore are considered to be effective not only for radiation heat scattering but also phonon scattering.

Further, as the above-mentioned inorganic powder, an inorganic powder having a reflectance of 70% or more to light having a wavelength of 10 μm or more can be suitably used. The light having a wavelength of 10 μm or more is light in the so-called infrared to far infrared wavelength region, and the radiation heat transfer can be more effectively reduced by the reflectance to light in this wavelength region being 70% or more.

The solid thermal conductivity of the inorganic powder is preferably 20 W / m · K or less at room temperature. When an inorganic powder whose solid thermal conductivity at room temperature is larger than 20 W / m · K is used as a raw material, solid heat transfer becomes dominant in the heat insulating layer 12, and the thermal conductivity increases (the thermal insulation property decreases). There is a risk of

In the present specification, the inorganic fiber refers to an inorganic material having an aspect ratio of 3 or more. On the other hand, the inorganic powder refers to an inorganic material having an aspect ratio of less than 3. Further, the aspect ratio means the ratio (b / a) of the major axis b to the minor axis a of the substance.

The heat insulation layer 12 may contain an inorganic binder for the purpose of maintaining the strength at high temperature. Examples of the inorganic binder include colloidal silica, synthetic mica, montmorillonite and the like. The above inorganic binders may be used alone or in combination of two or more.

This inorganic binder can be used as needed in the range of 1 to 10% by mass with respect to the total weight of the constituent materials of the heat insulation layer 12. As a usage aspect of the said inorganic binder, it can be used, for example, mixing in a raw material, or impregnating to the obtained heat insulating material.

Furthermore, an organic elastic material may be used as a constituent material of the heat insulating layer 12 as needed. This organic elastic material is useful in providing flexibility to the heat insulating layer 12, and for example, synthetic rubber latex binders such as natural rubber emulsion, acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), etc. are suitably used. It can be used. In particular, when the heat insulation layer 12 of the present embodiment is manufactured by a wet molding method, the flexibility can be improved by using the organic elastic material.

The compounding amount of the organic elastic material is preferably in the range of 0 to 5% by mass with respect to the total weight of the constituent materials of the heat insulation layer 12. The organic elastic material burns away when used in a high temperature range of 700 ° C. or more when the compounding amount exceeds 5% by mass, and the voids significantly increase, so the heat insulation may be deteriorated. There is.

The thickness of the heat insulation layer 12 is not particularly limited, but is preferably in the range of 0.1 to 4.0 mm. When the thickness of the thermal insulation layer 12 is less than 0.1 mm, sufficient mechanical strength can not be imparted to the thermal insulation layer 12. On the other hand, when the thickness of the heat insulation layer 12 exceeds 4.0 mm, there is a possibility that the volume energy density of the assembled battery may be lowered.

The inorganic powder constituting the heat insulation layer 12 does not easily escape to the outside of the heat insulation layer 12, but for the purpose of preventing the escape of the inorganic powder, part or all of the heat insulation layer 12 is densified as needed. May be In the heat insulation layer 12 of the present embodiment, the inorganic powder constituting the heat insulation layer 12 is included in the structure in which the inorganic fibers are intertwined, and therefore does not easily escape from the inorganic fibers to the outside. However, depending on the use environment, strong impact may be applied to the heat insulation layer 12 and the inorganic powder may escape into the air, so the structure of the inorganic fiber in the portion including the inorganic powder is densified, The inorganic powder may be prevented from escaping.

As a method of densifying the heat insulating layer 12, for example, there is a method of heating so as to melt only the surface in the entangled structure of inorganic fibers, or a method of covering the surface of the heat insulating layer 12 with a heat resistant film etc. The method is not particularly limited as long as the powder does not escape.

The bulk density of the heat insulating layer 12 is not particularly limited, but is preferably in the range of 0.1 to 1.0 g / cm ³ . The bulk density can be obtained as a value obtained by dividing the mass by the apparent volume (see JIS A 0202_2213). If the bulk density is less than 0.1 g / cm ³ , convective heat transfer and molecular heat transfer will increase, while if the bulk density exceeds 1.0 g / cm ³ , the heat transfer will increase due to the increase of solid heat transfer. In either case, the thermal insulation will be reduced.

(Endothermic layer)
The endothermic layer contains at least anhydrous hydrate. Examples of the anhydrous hydrate include aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), dawsonite (NaAl (OH)) and the like. These inorganic hydrates may be used alone or in combination of two or more. Among the above-mentioned inorganic hydrates, aluminum hydroxide or magnesium hydroxide is particularly preferable from the viewpoint of good endothermic properties.

For example, in the case of aluminum hydroxide, about 35% of crystal water is contained in aluminum hydroxide, and as shown in the following formula, it is possible to exhibit an anti-inflammatory function by releasing crystal water at the time of thermal decomposition. it can.
2Al (OH) ₃ → Al ₂ O ₃ + 3H ₂ O
By this function, the heat generated in the battery cell 20 can be absorbed, and the calorific value of the battery cell can be reduced.

As a compounding quantity of the said inorganic hydrate, a preferable upper limit is 90 mass% with respect to the total weight of the material which comprises the endothermic layer 14, and a still more preferable upper limit is 80 mass%. On the other hand, the preferable minimum of the compounding quantity of the said inorganic powder is 30 mass%, and a still more preferable minimum is 50 mass%. If this compounding amount is less than 30% by mass, there is a possibility that good endothermic characteristics can not be obtained. On the other hand, if the compounding amount exceeds 90% by mass, there is a possibility that the heat absorption layer can not be formed.

The heat absorption layer 14 may contain inorganic fibers or pulp fibers for the purpose of improving the strength at the time of molding. As said inorganic fiber, the thing similar to the inorganic fiber used for the heat insulation layer 12 demonstrated above can be used.

These inorganic fibers and pulp fibers can be used as needed in the range of 10 to 70% by mass with respect to the total weight of the materials constituting the endothermic layer 14.

An organic binder may be used as a material of the endothermic layer 14 if necessary. This organic binder is useful for the purpose of improving the strength at the time of molding, and for example, a polymer flocculant or an acrylic emulsion can be suitably used.

The compounding amount of the organic binder can be used as needed in the range of 0.5 to 5.0% by mass with respect to the total weight of the materials constituting the endothermic layer 14.

The thickness of the heat absorption layer 14 is not particularly limited, but is preferably in the range of 0.1 to 4.0 mm. When the thickness of the endothermic layer 14 is less than 0.1 mm, sufficient mechanical strength can not be imparted to the endothermic layer 14. On the other hand, when the thickness of the heat absorption layer 14 exceeds 4.0 mm, there is a possibility that the formation of the heat absorption layer 14 itself becomes difficult.

<Method of Manufacturing Insulation Sheet for Battery Pack>
Then, the manufacturing method of the heat insulation sheet 10 for assembled batteries is demonstrated in detail.

(Production method of thermal insulation layer)
The heat insulating layer 12 according to the present embodiment is manufactured by molding a material composed of at least inorganic fibers or inorganic powder by a dry molding method or a wet molding method. Below, the manufacturing method in the case of obtaining the heat insulation layer 12 by each shaping | molding method is demonstrated.

[When manufacturing using dry molding method]
First, in the dry molding method, at least one of inorganic fibers and inorganic powders and, if necessary, an inorganic binder and an organic elastic material are charged into a mixer such as a V-type mixer at a predetermined ratio. After thoroughly mixing the materials introduced into the mixer, the mixture is introduced into a predetermined mold and pressed to obtain the heat insulating layer 12. At the time of pressing, heating may be performed as needed.

The pressing pressure is preferably in the range of 0.98 to 9.80 MPa. In the heat insulation layer 12 obtained as a press pressure is less than 0.98 Mpa, there exists a possibility that it may collapse without being able to maintain intensity. On the other hand, if the pressing pressure exceeds 9.80 MPa, the processability is lowered due to excessive compression, and the bulk density is further increased, so that the solid heat transfer may be increased and the heat insulation may be lowered.

[When manufacturing using a wet molding method]
Subsequently, in the wet molding method, at least any one of inorganic fibers and inorganic powders, and optionally, an inorganic binder, is mixed and stirred in water to be sufficiently dispersed, and then a coagulant is added, A primary aggregate obtained by attaching an inorganic powder and an inorganic binder to inorganic fibers is obtained. Next, after adding an emulsion of an organic elastic material or the like into the water within a predetermined range as necessary, a polymer flocculant is added to obtain a slurry containing aggregates.

Next, the slurry containing the above aggregates is introduced into a predetermined mold to obtain the heat insulating layer 12 which is wetted. By drying the obtained heat insulation layer 12, the target heat insulation layer 12 is obtained.

As described above, the heat insulating layer 12 can be obtained by either a dry molding method or a wet molding method, but it is preferable to use the wet molding method in terms of the ease of integral molding and the mechanical strength.

(Method of manufacturing endothermic layer)
The endothermic layer 14 according to this embodiment is manufactured by molding a material composed of at least an inorganic hydrate by a dry molding method or a wet molding method. About the detailed conditions of the manufacturing method of an endothermic layer, it is the same as that of the manufacturing method of the said heat insulation layer except changing an inorganic fiber and inorganic powder into an inorganic hydrate.

(Joining of heat insulation layer and heat absorption layer)
About the method of joining the heat insulation layer 12 and the endothermic layer 14 and forming the heat insulation sheet 10 for assembled batteries, the heat insulation layer 12 and the endothermic layer 14 press the adhesive in the wet state in the wet state, or after drying these members The method of using and adhering can be mentioned.

Hereinafter, examples of the heat insulating sheet for battery assembly according to the present embodiment will be described, but the present invention is not limited to these examples.

Example 1
As inorganic powder, 50% by mass of TiO ₂ powder (average particle diameter: 8 μm) and 50% by mass of SiO ₂ powder (average particle diameter: 15 nm) were added and thoroughly mixed. The above mixture was molded into a mold to obtain a heat insulating layer (heat insulating sheet) having a thickness of 1 mm, and then the heat insulating layer was dried at 110 ° C. for 8 hours.

Subsequently, 45% by mass of aluminum hydroxide (Al (OH) ₃ ) powder (average particle diameter: 1 μm), 45% by mass of rock wool as inorganic fiber, 8% by mass of pulp fiber, 1.5% by mass of inorganic binder %, And 0.5% by mass of a polymer flocculant, and the mixture was sufficiently stirred and mixed to prepare a slurry. The slurry was formed into a sheet to obtain a heat absorbing layer (heat absorbing sheet) having a thickness of 1 mm.

By laminating the produced heat insulation layer and endothermic layer, the heat insulation sheet for assembled batteries was obtained.

Example 2
After molding an alumina-silica fiber (AF: Alumina Fiber) as an inorganic fiber by molding to obtain a heat insulation layer (heat insulation sheet) having a thickness of 1 mm, the heat insulation layer was dried under the condition of 110 ° C. × 8 hours.

Subsequently, 45% by mass of aluminum hydroxide powder (average particle diameter: 1 μm), 45% by mass of rock wool as inorganic fiber, 8% by mass of pulp fiber, 1.5% by mass of inorganic binder, and polymer aggregate The slurry was prepared by adding 0.5% by mass and thoroughly stirring and mixing. The slurry was formed into a sheet to obtain a heat absorbing layer (heat absorbing sheet) having a thickness of 1 mm.

Example 3
60 mass% of alumina-silica fiber (AF) as inorganic fiber, 20 mass% of TiO ₂ powder (average particle size: 8 μm) as inorganic powder, and 20 mass% of SiO ₂ powder (average particle size: 15 nm) Mix well. The above mixture was molded into a mold to obtain a heat insulating layer (heat insulating sheet) having a thickness of 1 mm, and then the heat insulating layer was dried at 110 ° C. for 8 hours.

Comparative Example 1
Under the same conditions and procedure as in Example 1, a heat insulating layer having a thickness of 2 mm was produced to obtain a heat insulating sheet for a battery pack. In the comparative example 1, the heat insulation sheet for assembled batteries is comprised only with the heat insulation layer in Example 1, and a heat absorption layer does not exist.

Comparative Example 2
Under the same conditions and procedure as in Example 2, a heat insulating layer having a thickness of 2 mm was produced to obtain a heat insulating sheet for a battery pack. In the comparative example 2, the heat insulation sheet for assembled batteries is comprised only with the heat insulation layer in Example 2, and a heat absorption layer does not exist.

Comparative Example 3
Under the same conditions and procedure as in Example 3, a heat insulating layer having a thickness of 2 mm was produced to obtain a heat insulating sheet for a battery pack. In the comparative example 3, the heat insulation sheet for assembled batteries is comprised only with the heat insulation layer in Example 3, and a heat absorption layer does not exist.

Comparative Example 4
A sheet of 2 mm in thickness made of alkali earth silicate (AES) fiber was prepared and used as a heat insulating sheet for battery pack.

Comparative Example 5
A thermal insulation sheet for a battery pack was obtained by stacking a 1 mm thick mica sheet and a 1 mm thick alumina-silica fiber (AF) sheet.

Comparative Example 6
Under the same conditions and procedure as in Example 1, a heat absorption layer having a thickness of 2 mm was produced to obtain a heat insulating sheet for a battery pack. In Comparative Example 6, only the heat absorption layer in Example 1 constitutes a heat insulating sheet for a battery assembly, and no heat insulating layer is present.

A heater was disposed on one side of the heat insulation sheet for a battery pack obtained in each of Examples 1 to 3 and Comparative Examples 1 to 6, and a metal plate simulating a battery cell adjacent to the other side was disposed on the other side. Furthermore, a thermocouple was placed on the metal plate, and the heater temperature was heated to 700 ° C., and the temperature change of the surface of the adjacent battery cell (metal plate) with respect to elapsed time was measured.

The graph which plotted the temperature change of the adjacent battery cell surface with respect to elapsed time in each Example and each comparative example is shown in FIG. Moreover, the maximum surface temperature of each Example and each comparative example is shown below.
Example 1: 336 ° C.
Example 2: 349 ° C.
Example 3: 343 ° C
Comparative Example 1: 367 ° C.
Comparative example 2: 448 ° C.
Comparative example 3: 427 ° C
Comparative Example 4: 478 ° C.
Comparative example 5: 403 ° C.
Comparative Example 6: 385 ° C.

As shown in FIG. 4, it can be seen that the temperature of the surface of the adjacent battery cell is kept low compared to Comparative Examples 1 to 6 in the heat insulation sheets for battery packs of Examples 1 to 3. From the above, it has been shown that the heat insulating sheet for a battery pack according to this example can effectively suppress the propagation of heat between the battery cells.

Although various embodiments have been described above with reference to the drawings, it goes without saying that the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the appended claims, and of course these also fall within the technical scope of the present invention. It is understood. In addition, the components in the above-described embodiment may be arbitrarily combined without departing from the scope of the invention.

This application is based on Japanese Patent Application (Japanese Patent Application No. 2017-210668) filed on October 31, 2017, the contents of which are incorporated into the present application as a reference.

DESCRIPTION OF SYMBOLS 10 Thermal insulation sheet for assembled batteries 12 Thermal insulation layer 14 Heat absorption layer 16 scale-like particle 20 battery cell 30 battery case 100 assembled battery

Claims

A heat insulating sheet for use in a battery pack in which a plurality of battery cells are disposed via a heat insulating sheet, and the plurality of battery cells are connected in series or in parallel,
A thermal insulation layer consisting of at least inorganic fiber or inorganic powder,
A heat insulating sheet for battery assembly characterized in that it has an endothermic layer formed on both sides of the heat insulating layer and made of at least inorganic hydrate.
The heat insulation sheet according to claim 1, wherein the heat insulation layer has a thermal conductivity lower than that of the heat absorption layer.
The heat insulation sheet according to claim 1 or 2, wherein the inorganic powder has a refractive index ratio (relative refractive index) to light having a wavelength of 1 μm or more.
The heat insulating sheet according to any one of claims 1 to 3, wherein the inorganic powder comprises TiO 2 powder or SiO 2 powder.
The inorganic powder is scale-like particles having anisotropy in thermal conductivity, and the plane direction of the scale-like particles is oriented in the direction perpendicular to the thickness direction of the heat insulation sheet. The heat insulation sheet for assembled batteries according to any one of the above.
6. The heat insulating sheet according to any one of claims 1 to 5, wherein the inorganic hydrate is at least one of aluminum hydroxide and magnesium hydroxide.
The heat insulation according to any one of claims 1 to 6, wherein the inorganic fiber is at least one of silica-alumina fiber, alumina fiber, silica fiber, rock wool, alkali earth silicate fiber and glass fiber. Sheet.
An assembled battery in which the plurality of battery cells are disposed via the heat insulating sheet for a battery assembly according to any one of claims 1 to 7, and the plurality of battery cells are connected in series or in parallel.