JP7048834B1 - Manufacturing method of heat insulating sheet for assembled battery and manufacturing method of assembled battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain excellent heat insulating property in a wide temperature range from a temperature in normal use of a battery to a high temperature of 500 ° C. or higher, and preferably even when the compressive stress on the heat insulating sheet increases. Provided are a heat insulating sheet for assembled batteries capable of maintaining excellent heat insulating properties, and an assembled battery in which a heat insulating sheet for assembled batteries is interposed between battery cells. A heat insulating sheet 10 of the present invention is a heat insulating sheet for an assembled battery interposed between the battery cells in an assembled battery in which a plurality of battery cells are connected in series or in parallel, and is composed of silica nanoparticles. The content of the first particles includes the first particles 21 and the second particles 22 made of a metal oxide, and the content of the first particles is 60% by mass or more and 95 with respect to the total mass of the first particles and the second particles. It is less than mass%. [Selection diagram] Fig. 1

Description

The present invention relates to a heat insulating sheet for assembled batteries interposed between battery cells of an assembled battery and an assembled battery in which a heat insulating sheet for assembled batteries is interposed between battery cells.

Conventionally, in order to suppress heat transfer from a heating element to another object, a heat insulating sheet used in close proximity to the heating element or at least partially in contact with the heating element has been used.

Further, in recent years, from the viewpoint of environmental protection, the development of electric vehicles or hybrid vehicles driven by electric motors has been actively promoted. This 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 a driving electric motor.

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

Also in the field of assembled batteries as described above, various heat insulating sheets interposed between battery cells in order to suppress heat propagation from a battery cell causing thermal runaway to an adjacent battery cell and prevent a chain of thermal runaway. Has been proposed. For example, Patent Document 1 discloses a power storage device in which two plate materials are arranged facing each other between two adjacent power storage elements, and the space formed between these plate materials functions as a low thermal conductive layer. There is. In the power storage device, for example, a dammer material or the like in which mica pieces are collected and bonded is used as a plate material.

By the way, in an assembled battery, thermal expansion is caused by repeated charging and discharging of individual battery cells, and a pressing force repeatedly acts between adjacent battery cells. In the heat transfer suppressing sheet described in Patent Document 1, since the low thermal conductive layer is an air layer, it cannot be said that the mechanical strength against such repeatedly acting pressing force is sufficient.

Further, since the battery cell that caused the thermal runaway expands greatly, in that case, the pressing force on the adjacent battery cell becomes excessive, and in the power storage device described in Patent Document 1, when the thermal runaway occurs. There is also a concern that the plate material made of damma material or the like may be damaged by a large pressing force.

Therefore, Patent Document 2 proposes a heat insulating material having a composite layer of a fiber sheet and silica airgel having a nano-sized porous structure as a heat insulating material mounted between adjacent battery cells. In the battery unit using the heat insulating material, the fiber sheet can absorb the stress even when the battery cell repeatedly expands and contracts and compressive stress is applied to the heat insulating material. As a result, the destruction of the silica airgel can be suppressed, and the deterioration of the heat insulating properties of the silica airgel can be prevented.

JP-A-2015-210113 Japanese Unexamined Patent Publication No. 2018-204708

However, even when the heat insulating material described in Patent Document 2 is used, there is a problem that the heat insulating property in a high temperature region is not sufficiently obtained. When the battery cells reach high temperatures, if the insulation is not functioning well, multiple cells will thermally expand and the insulation placed in the same battery case will be further compressed and the density of the insulation. May rise significantly. As a result, the thermal conductivity of the heat insulating material is further increased, and the desired heat insulating property cannot be maintained. Furthermore, if the heat insulating effect of the heat insulating material is reduced, it may not be possible to suppress problems such as burning and explosion of the battery when the battery causes abnormal heat generation. Therefore, in particular, there is a demand for the development of a heat insulating sheet for an assembled battery having excellent heat insulating properties even in a high temperature region of 500 ° C. or higher.

The present invention has been made in view of the above-mentioned situation, and excellent heat insulating properties can be obtained in a wide temperature range from the temperature in normal use of the battery to a high temperature of 500 ° C. or higher, and it is preferable to set the battery. Provided are a heat insulating sheet for assembled batteries capable of maintaining excellent heat insulating properties even when the compressive stress on the heat insulating sheet for batteries increases, and an assembled battery in which a heat insulating sheet for assembled batteries is interposed between battery cells. The purpose is to do.

The above object is achieved by the following (1) heat insulating sheet for assembled battery according to the present invention.
(1) A heat insulating sheet for an assembled battery interposed between the battery cells in an assembled battery in which a plurality of battery cells are connected in series or in parallel.
It contains a first particle made of silica nanoparticles and a second particle made of a metal oxide.
The content of the first particles is 60% by mass or more and 95% by mass or less with respect to the total mass of the first particles and the second particles.

Further, the heat insulating sheet for an assembled battery of the present invention is preferably the following (2) to (9).
(2) The heat insulating sheet for an assembled battery according to (1), wherein the first particles have an average particle diameter of 1 nm or more and 100 nm or less.
(3) The heat insulating sheet for an assembled battery according to (1) or (2), wherein the second particle is at least one selected from titania, zirconia, zircon, barium titanate, zinc oxide, and alumina.
(4) The heat insulating sheet for an assembled battery according to any one of (1) to (3), wherein the second particle is titania.
(5) The heat insulating sheet for an assembled battery according to any one of (1) to (4), wherein the second particle has an average particle diameter of 0.1 μm or more and 50 μm or less.
(6) Contains a binder consisting of at least one selected from fibers, binders and heat resistant resins.
The heat insulating sheet for assembled batteries according to any one of (1) to (5), wherein the content of the binder is 10% by mass or more and 60% by mass or less with respect to the total mass of the heat insulating sheet for assembled batteries.
(7) The heat insulating sheet for assembled batteries according to any one of (1) to (6), which contains 60% by mass or less of an inorganic balloon with respect to the total mass of the heat insulating sheet for assembled batteries.
(8) The heat insulating sheet for an assembled battery according to (7), wherein the inorganic balloon is at least one selected from a shirasu balloon, a silica balloon, a fly ash balloon, a bar light balloon, and a glass balloon.
(9) The heat insulating sheet for an assembled battery according to (7) or (8), wherein the inorganic balloon has an average particle diameter of 1 μm or more and 100 μm or less.

The above object is achieved by the assembled battery of the following (10) according to the present invention.
(10) A plurality of battery cells are arranged via the heat insulating sheet for assembled batteries according to any one of (1) to (9), and the plurality of battery cells are connected in series or in parallel. ..

According to the present invention, excellent heat insulating properties can be obtained in a wide temperature range from the temperature in normal use of the battery to a high temperature of 500 ° C. or higher, and the compressive stress on the heat insulating sheet for assembled batteries is preferably increased. Even in this case, it is possible to provide a heat insulating sheet for assembled batteries capable of maintaining excellent heat insulating properties, and an assembled battery in which a heat insulating sheet for assembled batteries is interposed between battery cells.

FIG. 1 is a schematic view showing the configuration of a heat insulating sheet for an assembled battery according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing an embodiment of the assembled battery according to the present invention. FIG. 3 is a graph showing the change in thermal conductivity depending on the mass ratio of the first particle and the second particle in the heat insulating sheet for assembled batteries when the vertical axis is the thermal conductivity and the horizontal axis is the temperature. FIG. 4 is a graph showing changes in thermal conductivity depending on the density of the heat insulating sheet for assembled batteries when the vertical axis is the thermal conductivity and the horizontal axis is the temperature.

The inventors of the present application can obtain excellent heat insulating properties in a wide temperature range from the temperature during normal use of the battery to a high temperature of 500 ° C. or higher (hereinafter, also referred to as "heat insulating sheet"). Diligently studied to provide. As a result, the heat insulating sheet contains the first particle composed of silica nanoparticles and the second particle composed of metal oxide, and the mass ratio of the first particle to the second particle is appropriately adjusted. It has been found that excellent heat insulating properties can be obtained even in a high temperature region.

The silica nanoparticles contained as the first particles in the heat insulating sheet have an excellent heat insulating property of suppressing conduction heat transfer because of their low density and further suppressing convection heat transfer because the voids are finely dispersed. Therefore, it is possible to suppress heat conduction between adjacent silica nanoparticles when using a battery in a normal normal temperature range. However, since the first particles have a low density and a small particle diameter, the light shielding effect is small, and the effect of suppressing radiant heat transfer is small. Therefore, further, by containing a metal oxide having a high refractive index and a strong effect of diffusely reflecting light as the second particles, radiant heat transfer can be suppressed particularly in a high temperature region such as abnormal heat generation. Therefore, by containing silica nanoparticles and metal oxides in an appropriate ratio in the heat insulating sheet, excellent heat insulating properties can be obtained in a wide temperature range from the temperature during normal use of the battery to a high temperature of 500 ° C. or higher. can.

Further, the inventors of the present application use silica nanoparticles having a small average particle diameter in the heat insulating sheet, and even when the heat insulating sheet is compressed due to swelling of the battery or the like and the density of the heat insulating sheet is increased, the heat insulating sheet can be used. It was found that the increase in conduction heat transfer can be suppressed.
It is considered that this is because the silica nanoparticles are an insulator, so that fine voids are likely to be formed between the particles due to the repulsive force due to static electricity, and the particles are filled so as to have a low bulk density and a cushioning property. That is, when the heat insulating sheet contains silica nanoparticles having an average particle diameter of 1 nm or more and 100 nm or less, even if compressive stress is applied, the voids remaining between the silica nanoparticles and the contacts between many particles are conducted. It is possible to suppress heat transfer and maintain the heat insulating property of the heat insulating sheet.

Furthermore, the inventors of the present application have found that the size of the voids between the particles contained in the heat insulating sheet affects the heat insulating property of the heat insulating sheet. That is, if the voids formed between the particles are, for example, several hundred nm or more, convection is likely to act in the voids, and the heat insulating property of the heat insulating sheet may be deteriorated.
However, in the heat insulating sheet using silica nanoparticles having a small particle size as the first particles, the voids between the particles are as small as several tens of nm, for example, air movement in the voids is unlikely to occur, and convection heat transfer is generated. It is considered that it can be suppressed and the heat insulating property can be further improved.
It is important for the silica nanoparticles to form many fine voids and increase the number of contacts between the particles, and the silica nanoparticles may be contained as primary particles or aggregated secondary particles.

Although the present invention is based on such findings, the heat insulating sheet for an assembled battery and the assembled battery according to the embodiment of the present invention (the present embodiment) will be described in detail with reference to the drawings.

<Basic configuration of heat insulating sheet for assembled battery>
FIG. 1 is a schematic view showing the configuration of a heat insulating sheet for an assembled battery according to an embodiment of the present invention, and FIG. 2 is a cross section schematically showing an embodiment of an assembled battery using the heat insulating sheet for assembled battery shown in FIG. It is a figure. The heat insulating sheet 10 contains first particles 21 made of silica nanoparticles and second particles 22 made of titania (metal oxide).
As the silica nanoparticles, it is desirable to use particles having an average particle diameter of 1 nm or more and 100 nm or less as the primary particles.

As a specific usage pattern of the heat insulating sheet 10 for assembled batteries, as shown in FIG. 2, a plurality of battery cells 20 are arranged via the heat insulating sheet 10 for assembled batteries, and the plurality of battery cells 20 are in series with each other. Alternatively, the assembled battery 100 is configured by being stored in the battery case 30 in a state of being connected in parallel (the connected state is not shown).
As the battery cell 20, for example, a lithium ion secondary battery is preferably used, but the battery cell 20 is not particularly limited to this, and can be applied to other secondary batteries.

In the following description, it is assumed that the heat-generating battery cell 20 exists on one surface 10a side of the heat insulating sheet 10. In the heat insulating sheet configured as described above, when the battery cell 20 generates heat, a part of the heat incident from one surface 10a side of the heat insulating sheet 10 causes the first particles 21 in contact with each other as shown by the arrow 15a. As a medium, it is conducted (conducted heat transfer) toward the other surface 10b of the heat insulating sheet 10. At this time, since silica nanoparticles having heat insulating properties are used as the first particles 21, a high thermal resistance is high, a high temperature difference can be secured between the first particles 21 and the other surface 10b of the heat insulating sheet 10, and the amount of heat transfer is reduced. ..

Further, when the battery cell 20 generates heat and a part of the heat reaches the second particles 22 due to radiation, as shown by the arrow 15b, the second particles 22 which are metal oxides diffusely reflect the second particles. The presence of 22 can prevent heat from being propagated to the other surface 10b of the heat insulating sheet 10.

From the above, when thermal runaway occurs in a certain battery cell 20, heat propagation to other adjacent battery cells can be effectively suppressed, so that thermal runaway of other battery cells is suppressed. be able to.

In this embodiment, silica nanoparticles are used as the first particles 21, and the contact points between the particles are small. Therefore, the amount of heat conducted by the silica nanoparticles uses silica particles obtained by pulverization having a large particle diameter. It becomes smaller than the case where it is done. Further, since the bulk density of the silica nanoparticles generally obtained is about 0.1 g / cm ³ , for example, the battery cells 20 arranged on both sides of the heat insulating sheet 10 thermally expand, and the heat insulating sheet 10 is subjected to thermal expansion. Even when a large compressive stress is applied, the size (area) and number of contacts between the silica nanoparticles do not become significantly large, and the heat insulating property can be maintained.

Further, in the present embodiment, even when the silica nanoparticles are overlapped and exist in the heat insulating sheet 10, the voids formed between the particles remain at about several tens of nm, and small convection as shown by the arrow 15c occurs. The range of convection that only occurs and occupies the entire thickness is negligible. Therefore, heat transfer that penetrates the front and back of the heat insulating sheet 10 is less likely to occur. Therefore, when silica nanoparticles are used as the first particles 21, the heat insulating property of the heat insulating sheet 10 can be further improved.

<Details of heat insulating sheet for assembled battery>
Next, the first particles and the second particles constituting the heat insulating sheet for the assembled battery will be described in detail.

(Type of first particle)
In the present invention, silica nanoparticles are used as the first particles. As the silica nanoparticles, wet silica, dry silica, airgel and the like can be used.
Further, in the present invention, the silica nanoparticles are nanometer-order silica particles having a spherical or near-spherical average particle diameter of less than 1 μm.

(Average particle size of the first particle: 1 nm or more and 100 nm or less)
As described above, since the particle size of the first particle may affect the heat insulating property of the heat insulating sheet, further higher heat insulating property can be obtained by limiting the average particle size of the first particle to a predetermined range. can.
That is, when the average particle diameter of the first particles is 1 nm or more and 100 nm or less, convection heat transfer and conduction heat transfer of heat in the heat insulating sheet can be suppressed particularly in a temperature region of less than 500 ° C., and the heat insulating property is further improved. It can be further improved.
The average particle size of the first particles is more preferably 2 nm or more, and further preferably 3 nm or more. Further, the average particle size of the first particles is more preferably 50 nm or less, and further preferably 10 nm or less.

(Type of second particle)
In the present invention, a metal oxide is used as the second particle. As the metal oxide, titania, zirconia, zircon, barium titanate, zinc oxide, alumina and the like can be used. In particular, titania is a component having a higher refractive index than other metal oxides, and has a high effect of diffusely reflecting light in a high temperature region of 500 ° C. or higher to block radiant heat. Therefore, it is most preferable to use titania.

(Average particle size of the second particle: 0.1 μm or more and 50 μm or less)
Since the particle size of the second particle may affect the effect of reflecting radiant heat, further higher heat insulating property can be obtained by limiting the average particle size of the second particle to a predetermined range.
That is, when the average particle diameter of the second particles is 0.1 μm or more, it is sufficiently larger than the wavelength of light that contributes to heating, and the light is efficiently diffusely reflected, and the existence range (mass ratio) of the second particles in the present invention is achieved. ), The radiant heat transfer of heat in the heat insulating sheet is suppressed in a high temperature region of 500 ° C. or higher, and the heat insulating property can be further improved. On the other hand, when the average particle diameter of the second particle is 50 μm or less, the number of contacts and the number of contacts between the particles does not increase even when compressed, and it is difficult to form a conduction heat transfer path. The effect on the heat insulation of the area can be reduced.
The average particle size of the second particles is more preferably 1 μm or more, further preferably 5 μm or more. Further, the average particle size of the second particles is more preferably 30 μm or less, and further preferably 10 μm or less.
In the present invention, the average particle size can be obtained by observing the particles with a microscope, comparing them with a standard scale, and taking the average of 10 arbitrary particles.

(Contents of the first particle: 60% by mass or more and 95% by mass or less with respect to the total mass of the first particle and the second particle)
In the present invention, in order to improve the heat insulating property even in a high temperature region of 500 ° C. or higher, the heat insulating sheet contains the second particles, but the amount of the second particles added to the first particles is small. Even if there is, the effect of suppressing radiant heat transfer of heat can be obtained. Further, in order to obtain the effect of suppressing heat convection heat transfer and conduction heat transfer by the first particles, it is preferable to increase the amount of the first particles added to the second particles.
Since the first particle is a silica nanoparticle, the bulk density is low (about 0.1 g / cm ³ ), and the second particle has a larger average particle diameter than the first particle, so that there are few voids, and the bulk density of the second particle is high. It is 10 times or more that of the first particle, for example, about 40 times (about 4 g / cm ³ ) when titania is selected. Therefore, when expressed in volume ratio (compared to the case expressed in mass ratio), the ratio of the second particle is very small, but the second particle only needs to block light in order to suppress radiant heat transfer. It works well even in very small amounts. As described above, the mass ratio of the first particle to the second particle greatly affects the heat insulating property in the region from the normal temperature to the high temperature of 500 ° C. or higher. Therefore, in the present invention, the first particle and the second particle are used. It is necessary to properly adjust the mass ratio with.

When the content of the first particles of the heat insulating sheet for an assembled battery of the present invention is 60% by mass or more with respect to the total mass of the first particles and the second particles, the first particles occupy most of the volume. It suppresses convection heat transfer or conduction heat transfer of heat in the heat insulating sheet, and the heat insulating property becomes high even if it is compressed.
The content of the first particles of the heat insulating sheet for an assembled battery of the present invention is more preferably 70% by mass or more with respect to the total mass of the first particles and the second particles. When the content of the first particle is 70% by mass or more with respect to the total mass of the first particle and the second particle, the first particle further occupies most of the volume in the heat insulating sheet. Convection heat transfer or conduction heat transfer of heat is suppressed, and the heat insulating property is further improved.

On the other hand, when the content of the first particle is 95% by mass or less with respect to the total mass of the first particle and the second particle, the content of the second particle is 5% by mass or more, depending on the second particle. It becomes possible to exert the shielding effect of radiant heat. Therefore, in a high temperature region of 500 ° C. or higher, radiant heat transfer of heat in the heat insulating sheet can be suppressed and heat insulating properties can be exhibited.
The content of the first particles of the heat insulating sheet for an assembled battery of the present invention is more preferably 90% by mass or less with respect to the total mass of the first particles and the second particles. When the content of the first particle is 90% by mass or less with respect to the total mass of the first particle and the second particle, the content of the second particle is 10% by mass or more, and the radiant heat generated by the second particle. It will be possible to further exert the shielding effect of. Therefore, in a high temperature region of 500 ° C. or higher, radiant heat transfer of heat in the heat insulating sheet can be suppressed, and heat insulating properties can be exhibited even when further compressed.

Further, the average particle size of the second particle is preferably 100 to 10,000 times the particle size of the first particle. Since both the first particle and the second particle are insulators, a repulsive force due to static electricity acts between the individual particles, and a certain void is formed. The finer the particle size, the higher the ratio of voids due to the influence of the repulsive force due to static electricity, and the lower the bulk density. When the average particle size of the second particle is 100 times or more the particle size of the first particle, the first particle contains many voids to ensure cushioning and heat insulating properties, and the second particle is light due to diffused reflection. A sufficient particle size can be secured for shielding, and heat insulation can be ensured in a wide temperature range even when compressed from the outside.
Further, when the average particle size of the second particle is 10,000 times or less the particle size of the first particle, it is difficult to form a path of conduction heat transfer, and in particular, the heat insulating property in the normal temperature range where the conduction heat transfer is dominant is obtained. The effect of can be reduced.

In the heat insulating sheet for an assembled battery of the present invention, it is preferable that the average particle size of the first particles is 1 nm or more and 100 nm or less, and the average particle size of the second particles is 0.1 μm or more and 50 μm or less.
When the average particle size of the first particles is 1 nm or more and 100 nm or less, many voids are formed and have cushioning properties. Therefore, even if a compressive force is applied from the outside, a wide temperature range is centered on the normal temperature range. Convection heat transfer and conduction heat transfer can be efficiently suppressed over the entire period.
Further, when the average particle diameter of the second particles is 0.1 μm or more and 50 μm or less, radiant heat transfer can be efficiently suppressed in a high temperature region of 500 ° C. or more. As a result, it is considered that high heat insulating properties can be obtained even when a compressive force is applied from the outside over a wide temperature range from the temperature in normal use of the battery to a high temperature of 500 ° C. or higher.

In the heat insulating sheet for an assembled battery of the present invention, the content of the first particles is 60% by mass or more and 95% by mass or less with respect to the total mass of the first particles and the second particles, and the content of the first particles is It is desirable that the average particle size is 1 nm or more and 100 nm or less, and the average particle size of the second particle is 0.1 μm or more and 50 μm or less.
When the average particle size of the first particles is 1 nm or more and 100 nm or less, many voids are formed and have cushioning properties. Therefore, even if a compressive force is applied from the outside, a wide temperature range is centered on the normal temperature range. Convection heat transfer and conduction heat transfer can be efficiently suppressed over the entire period.
When the average particle diameter of the second particles is 0.1 μm or more and 50 μm or less, radiant heat transfer can be efficiently suppressed in a high temperature region of 500 ° C. or higher.
When the content of the first particle is 60% by mass or more and 95% by mass or less with respect to the total mass of the first particle and the second particle, the amount of the second particle required for suppressing radiant heat transfer and the amount of the second particle. , The amount of first particles required for suppression of conduction / convection heat transfer and cushioning can be optimized.
As a result, it is considered that a well-balanced and high heat insulating property can be obtained over a wide temperature range from the temperature in normal use of the battery to a high temperature of 500 ° C. or higher even if a compressive force is applied from the outside.

In addition to the first particles and the second particles, the heat insulating sheet for an assembled battery may contain an inorganic balloon as a component that further enhances the heat insulating effect, and further, such as a binder and a colorant, may be contained. It may contain components necessary for molding into a heat insulating material. Hereinafter, other components will be described in detail.

(Inorganic balloon: 60% by mass or less)
The heat insulating sheet for an assembled battery according to the present invention may contain an inorganic balloon of 60% by mass or less with respect to the total mass of the heat insulating sheet.
When the heat insulating sheet contains an inorganic balloon in the range of 60% by mass or less, convection heat transfer or conduction heat transfer of heat in the heat insulating sheet can be suppressed in a temperature range of less than 500 ° C., and the heat insulating property of the heat insulating sheet can be suppressed. Can be further improved.
The mass of the inorganic balloon with respect to the total mass of the heat insulating sheet is more preferably 50% by mass or less. As the inorganic balloon, at least one selected from a shirasu balloon, a silica balloon, a fly ash balloon, a bar light balloon, and a glass balloon can be used.

(Average particle size of inorganic balloon: 1 μm or more and 100 μm or less)
When the heat insulating sheet for assembled batteries according to the present invention contains an inorganic balloon, when the average particle size of the inorganic balloon is appropriately adjusted, the battery cell thermally expands and compressive stress is applied to the heat insulating sheet. Even so, the effect of the change in density on the heat insulating property can be reduced.
That is, when the average particle size of the inorganic balloon is 1 μm or more and 100 μm or less, it is possible to further suppress the deterioration of the heat insulating property even if the densities of the first particles and the second particles in the heat insulating sheet change. .. Further, the average particle size of the inorganic balloon is more preferably 3 μm or more and 70 μm or less.

In the heat insulating sheet for assembled batteries according to the present invention, the total amount of the first particles, the second particles and the inorganic balloons functioning as heat insulating materials is 40% by mass or more and 95% by mass with respect to the total mass of the heat insulating sheet for assembled batteries. The following is preferable. Within this range, heat insulating properties can be easily obtained, strength as a sheet can be ensured, and scattering of particles can be suppressed. Further, the total amount of the first particles, the second particles and the inorganic balloons functioning as the heat insulating material is more preferably 50% by mass or more and 80% by mass or less with respect to the total mass of the heat insulating sheet for the assembled battery.

(Binding material: 10% by mass or more and 60% by mass or less)
The heat insulating sheet for assembled batteries according to the present invention can be formed by sintering or the like even if it does not contain a binder, but particularly when the heat insulating sheet for assembled batteries contains silica nanoparticles as the first particles. It is preferable to add a binder in an appropriate content in order to maintain the shape of the heat insulating sheet. In the present invention, the binder may be any material that is held together to hold the first particle and the second particle, and is a binder with adhesion, a fiber that physically entangles the particles, and an adhesive force. It does not matter what form it is, such as the heat-resistant resin that adheres to it.

As the binder, an organic binder, an inorganic binder, or the like can be used. The present invention is not particularly limited to these types, but as the organic binder, a polymer flocculant, an acrylic emulsion or the like can be used, and as the inorganic binder, for example, silica sol, alumina sol, aluminum sulfate band or the like can be used. can. These function as an adhesive when a solvent such as water is removed.

As the fiber, organic fiber, inorganic fiber and the like can be used. The organic fiber is not particularly limited, but synthetic fiber, natural fiber, pulp and the like can be used. The inorganic fiber is not particularly limited, but it is preferable to use alumina fiber, silica-alumina fiber, silica fiber, glass fiber, glass wool, rock wool and the like.

On the other hand, since the binder is composed of components having higher thermal conductivity than the first particles and the second particles, the binder is present in the voids formed in the heat insulating sheet to the extent that convection heat transfer does not occur. Then, the suppression of convection heat transfer and conduction heat transfer by the first particle will be affected. Therefore, in the heat insulating sheet for assembled batteries of the present invention, the content of the binder is preferably 60% by mass or less, more preferably 50% by mass or less, based on the total mass of the heat insulating sheet. In the heat insulating sheet for an assembled battery of the present invention, the content of the binder is preferably 10% by mass or more, more preferably 20% by mass or more, based on the total mass of the heat insulating sheet.

(Average fiber diameter of inorganic fiber: 0.1 μm or more and 20 μm or less)
The inorganic fiber is a linear or needle-shaped fiber, and contributes to the improvement of mechanical strength and shape retention against the compressive stress from the battery cell of the heat insulating sheet.
In order to obtain such an effect, when an inorganic fiber is used as a binder, the average fiber diameter thereof is preferably 0.1 μm or more, and more preferably 2 μm or more. However, if the inorganic fiber is too thick, the moldability and processability on the heat insulating sheet may deteriorate, so the thickness is preferably 20 μm or less, and more preferably 15 μm or less.

(Average fiber length of inorganic fiber: 0.1 mm or more and 20 mm or less)
When an inorganic fiber is used as a binder, the fibers are suitably entangled with each other when molded as a heat insulating sheet, and a sufficient surface pressure can be obtained.
In order to obtain such an effect, when an inorganic fiber is used, the average fiber length thereof is preferably 0.1 mm or more, and more preferably 0.5 mm or more. However, if the average fiber length of the inorganic fibers is too long, the entanglement between the inorganic fibers may become too strong when preparing a slurry solution in which the inorganic fibers are dispersed in water in the papermaking process. May be more likely to accumulate unevenly.
Therefore, the average fiber length of the inorganic fiber is preferably 20 mm or less, and more preferably 10 mm or less.
The fiber diameter and fiber length of the inorganic fiber can be measured by extracting the inorganic fiber from the molded sheet without breaking it using tweezers, observing it with a microscope, and comparing it with a standard scale. The fiber diameter and fiber length of the inorganic fiber are obtained from the average value of 10 arbitrary fibers.

(Thickness of heat insulating sheet: 0.1 mm or more and 30 mm or less)
The thickness of the heat insulating sheet for an assembled battery according to the present invention is not particularly limited, but is preferably in the range of 0.1 mm or more and 30 mm or less. When the thickness of the heat insulating sheet is within the above range, sufficient mechanical strength can be obtained and molding can be easily performed.

(Manufacturing method of heat insulating sheet for assembled battery)
Subsequently, a method for manufacturing a heat insulating sheet for an assembled battery according to the present invention will be described in detail.

The heat insulating sheet according to the present embodiment can be manufactured by molding a material for a heat insulating sheet containing the first particles and the second particles by a wet molding method, a dry molding method, or a wet molding method, or by an extrusion molding method. May be manufactured by The manufacturing method when the heat insulating sheet is obtained by each molding method will be described below.

[Manufacturing method of heat insulating sheet by wet papermaking method]
In the wet papermaking method, first, the first and second particles, and if necessary, the inorganic fiber, the organic fiber, or the organic binder as a binder are mixed in water and stirred with a stirrer to prepare a mixed solution. Prepare. Then, the obtained mixed liquid is poured into a molding machine having a mesh for filtration formed on the bottom surface, and the mixed liquid is dehydrated through the mesh to prepare a wet sheet. Then, by heating and pressurizing the obtained wet sheet, a heat insulating sheet can be obtained. Before the heating and pressurizing steps, hot air may be aerated through the wet sheet to dry the sheet, but this aeration-drying treatment may not be carried out, and the wet sheet may be heated and heated in a wet state. You may pressurize.

[Manufacturing method of heat insulating sheet by dry molding method]
In the dry molding method, first, the first particles and the second particles, and if necessary, inorganic fibers, organic fibers, or organic binders as a binder are charged into a mixer such as a V-type mixer at a predetermined ratio. Then, after the materials charged in the mixer are sufficiently mixed, the mixture is charged into a predetermined mold and pressed to obtain a heat insulating sheet. At the time of pressing, it may be heated if necessary.

The press pressure is preferably in the range of 0.98 to 9.80 MPa. If the press pressure is less than 0.98 MPa, the obtained heat insulating sheet may not be able to maintain its strength and may collapse. On the other hand, if the press pressure exceeds 9.80 MPa, the workability may be lowered due to excessive compression, and the bulk density may be increased, so that the solid heat transfer may be increased and the heat insulating property may be lowered.

[Manufacturing method of heat insulating sheet by extrusion molding method]
In the extrusion molding method, a paste is prepared by first adding water to the first and second particles and, if necessary, an inorganic fiber, an organic fiber, or an organic binder as a binder and kneading them with a kneader. .. Then, the obtained paste is extruded from a slit-shaped nozzle using an extruder and further dried to obtain a heat insulating sheet for an assembled battery. As the organic binder, methyl cellulose, water-soluble cellulose ether and the like are preferably used, but any organic binder generally used when an extrusion molding method is used can be used without particular limitation.

[Battery set]
In the assembled battery according to the present invention, as illustrated in FIG. 2, a plurality of battery cells are arranged via the above-mentioned heat insulating sheet for assembled batteries, and the plurality of battery cells are connected in series or in parallel. ..

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

The following group 1st particles, 2nd particles, and a binder were prepared, and these materials were sufficiently stirred and mixed to prepare a slurry. Using the obtained slurry, a heat insulating sheet was formed by a papermaking method.

Silica nanoparticles (average particle diameter 5 nm) are 56% by mass for the first particles, and titania (average particle diameter 8 μm) is 24% by mass for the second particles (first particles: second particles = 70% by mass: 30% by mass). ) As a binder, add 11% by mass of glass fibers (average fiber diameter 10 μm, average fiber length 5 mm), 8% by mass of pulp fibers, and 1% by mass of polymer agglomerates, and thoroughly stir and mix to prepare a slurry. bottom. The above slurry was made into a heat transfer suppressing sheet (insulation sheet No. 1).
The drying was carried out at 110 ° C., and the size of the obtained heat insulating sheet was 80 mm in width, 80 mm in length and 1 mm in thickness.

Regarding the heat insulating sheet in which the mass ratio of the first particle and the second particle is variously changed, a plurality of points ranging from the temperature during normal use of the battery (about 30 ° C.) to the high temperature of 500 ° C. or higher (about 850 ° C.). In, the thermal conductivity was measured. The thermal conductivity was measured by the transient hot wire method in accordance with the JIS method (R2616).

The content of the first particle (mass% with respect to the total amount of the first particle and the second particle) in each heat insulating sheet is shown in Table 1 below, and the thermal conductivity of the heat insulating sheet at each temperature is shown in FIG. In addition, the numbers 1 to 6 in FIG. 3 are the heat insulating sheet No. 1 shown in Table 1. Corresponds to 1 to 6 respectively. Further, in Table 1 and FIG. 3 below, the heat insulating sheet No. No. 6 is an example in which silica airgel is used as the first particle, and does not contain the binder shown in Table 1 above.

Insulation sheet for assembled battery No. 1 to 4 contain a metal oxide (titania) as the second particles, and the content of the first particles with respect to the total mass of the first particles and the second particles is within the scope of the present invention. Therefore, excellent heat insulating properties can be obtained in the temperature range from the temperature during normal use of the battery (about 30 ° C.) to the high temperature of 500 ° C. or higher (about 850 ° C.). In particular, as the content of the second particles increases, the thermal conductivity in a high temperature region of 500 ° C. or higher decreases, and the heat insulating property is improved.

On the other hand, the heat insulating sheet No. Since the second particles are not contained in 5 and 6, the thermal conductivity is high in the high temperature region of 500 ° C. or higher. In addition, the heat insulating sheet No. Both 5 and 6 do not contain the second particle, but the heat insulating sheet No. Due to the influence of the magnesium silicate fiber contained in 5, the heat insulating sheet No. It is considered that the thermal conductivity in the high temperature region of 500 ° C. or higher was lowered as compared with 6.

Next, the heat insulating sheet No. Insulation sheets having various densities were formed by the papermaking method with the same components and contents as in No. 1, and the change in thermal conductivity due to the density of the insulation sheet was measured by the above-mentioned transient hot wire method. The types and densities of the heat insulating sheets are shown in Table 2 below, and the thermal conductivity of the heat insulating sheets having different densities at each temperature is shown in FIG. Numbers 11 to 15 in FIG. 4 are heat insulating sheet Nos. Nos. 11 and 15 shown in Table 2. It corresponds to 11 to 15 respectively. In addition, the heat insulating sheet No. 11 and 12 are examples in which the content of the first particles (silica nanoparticles) is 70% by mass with respect to the total mass of the first particles and the second particles. In addition, the heat insulating sheet No. 13 and 14 are examples in which aluminum hydroxide powder was used instead of silica nanoparticles and titania, and the heat insulating sheet No. 13 and 14 were used. Reference numeral 15 is an example using airgel.

As shown in Table 2 and FIG. 4, the heat insulating sheet No. Nos. 11 and 12 contain silica and titania in an appropriate ratio, and the heat insulating sheet No. 11 and 12 are made of aluminum hydroxide powder. Compared with 13 and 14, the thermal conductivity was lower in any temperature range. In addition, the heat insulating sheet No. using airgel. Compared with 15, it was possible to obtain excellent heat insulating properties, especially in the temperature range of about 400 ° C. or higher. Further, the heat insulating sheet No. Since the first particles of 11 and 12 use silica nanoparticles having an extremely small particle diameter, the compressive stress on the heat insulating sheet increases, and even when the density increases, the particles are not easily affected by the increase in density. , Both were able to obtain excellent heat insulating properties.

On the other hand, the heat insulating sheet No. As represented by 13 and 14, the increase in density from 1.00 (g / cm ³ ) to 1.50 (g / cm ³ ) resulted in a significant increase in thermal conductivity over all temperature ranges. From these facts, even when the battery cells arranged on both sides of the heat insulating sheet thermally expand and compressive stress is applied to the heat insulating sheet, the silica nano having an average particle diameter of 1 nm to 100 nm as the first particles. It has been shown that excellent heat insulating properties can be maintained by using particles.

10 Insulation sheet 10a, 10b side 20 Battery cell 21 First particle 22 Second particle 30 Battery case 100 sets Battery

Claims (10)

A first particle composed of silica nanoparticles, a second particle consisting of at least one selected from titania, zirconia, zircone, barium titanate, zinc oxide, and alumina, and linear or needle-like inorganic fibers. A method for manufacturing a heat insulating sheet for an assembled battery, which is manufactured by molding a material for a heat insulating sheet containing, etc. by a wet method .
The silica nanoparticles are wet silica and are contained in aggregated secondary particles, and the repulsive force due to static electricity forms fine voids between the silica nanoparticles.
A method for manufacturing a heat insulating sheet for an assembled battery, wherein the content of the first particles is 60% by mass or more and 90% by mass or less with respect to the total mass of the first particles and the second particles. A first particle composed of silica nanoparticles, a second particle consisting of at least one selected from titania, zirconia, zircon, barium titanate, zinc oxide, and alumina, and linear or needle-like inorganic fibers. A step of preparing a mixed solution by mixing and stirring a material for a heat insulating sheet containing, in water, and
The step of dehydrating the mixed solution to prepare a wet sheet and
The step of heating and pressurizing the wet sheet and
Is a method for manufacturing a heat insulating sheet for an assembled battery by a wet papermaking method.
The silica nanoparticles are wet silica and are contained in aggregated secondary particles, and the repulsive force due to static electricity forms fine voids between the silica nanoparticles.
A method for manufacturing a heat insulating sheet for an assembled battery, wherein the content of the first particles is 60% by mass or more and 90% by mass or less with respect to the total mass of the first particles and the second particles. The method for manufacturing a heat insulating sheet for an assembled battery according to claim 1 or 2, wherein the material for the heat insulating sheet further contains at least one of an organic fiber and an organic binder. The method for manufacturing a heat insulating sheet for an assembled battery according to any one of claims 1 to 3, wherein the first particles have an average particle diameter of 1 nm or more and 100 nm or less. The method for manufacturing a heat insulating sheet for an assembled battery according to any one of claims 1 to 4 , wherein the second particle is titania. The method for manufacturing a heat insulating sheet for an assembled battery according to any one of claims 1 to 5 , wherein the second particles have an average particle diameter of 0.1 μm or more and 50 μm or less. The method for manufacturing a heat insulating sheet for assembled batteries according to any one of claims 1 to 6 , which comprises 60% by mass or less of an inorganic balloon with respect to the total mass of the heat insulating sheet for assembled batteries. The method for manufacturing a heat insulating sheet for an assembled battery according to claim 7 , wherein the inorganic balloon is at least one selected from a shirasu balloon, a silica balloon, a fly ash balloon, a bar light balloon, and a glass balloon. The method for manufacturing a heat insulating sheet for an assembled battery according to claim 7 or 8 , wherein the inorganic balloon has an average particle size of 1 μm or more and 100 μm or less. A plurality of battery cells are arranged via the heat insulating sheet for assembled batteries obtained by the method for manufacturing a heat insulating sheet for assembled batteries according to any one of claims 1 to 9 , and the plurality of battery cells are arranged in series or in parallel. How to make a battery pack to connect to .

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