JP2020165065A - Heat-resistant heat-insulation sheet and manufacturing method thereof, and battery pack - Google Patents

Abstract

To provide a heat-resistant heat-insulation sheet having excellent heat resistance and heat-insulation property, burning difficulty, and light weight, and a battery pack having this heat-resistant heat-insulation sheet inserted between cells.SOLUTION: The heat-resistant heat-insulation sheet 10 has a total thickness of 0.1-2.5 mm and a total combustion heat of 1MJ/m2 or under, and is assembled with a low-density layer 1 having a content a rate of a clay mineral occupying in the total content of an inorganic fiber and the clay mineral of lower than 50 mass%, and a first high-density layer 2 and a second high-density layer 3 respectively provided on both sides of the low-density layer 1; wherein the first high-density layer 2 and the second high-density layer 3 have 50 mass% or over of a content rate of the clay mineral occupying in the total content of the inorganic fiber and the clay mineral, and the thickness of the first high-density layer 2 and the second high-density layer 3 are lower than or equal to the thickness of the low-density layer 1 and 0.05 mm or over.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heat-resistant heat insulating sheet, a method for manufacturing the same, and an assembled battery.

In recent years, high-output, high-capacity rechargeable batteries such as lithium-ion batteries have come to be widely used in mobile devices, tools, automobiles, railways, aircraft, and the like. In these high-power, high-capacity rechargeable batteries, when a short circuit occurs due to damage or internal impurities, internal energy is instantaneously released as heat, which may accelerate the deterioration of the battery or cause ignition.

In particular, for applications such as automobiles that are equipped with a high-capacity storage capacity, a large number of cells are stacked because high voltage and high output are required, and the state of an assembled battery packed with adjacent cells (battery pack or It is often used in (sometimes called an aggregate). In that case, there is a concern that the failure of one cell may extend to adjacent batteries.
Therefore, Patent Document 1 proposes to detect an abnormality by measuring the temperature.
However, in Patent Document 1, although an abnormality can be detected, it is not possible to prevent a defect of one cell cell from reaching an adjacent battery.

In order to prevent the malfunction of one cell from extending to adjacent batteries, it is conceivable to arrange a nonflammable heat-resistant heat insulating sheet between the cells.
A candidate for the heat-resistant heat-insulating sheet is a thin metal plate that is nonflammable, but it has high thermal conductivity and cannot block the heat effect on adjacent cells. Further, since the metal has a high specific gravity and is a conductor, there are problems that it is necessary to take measures for insulation with the cell electrode and that the end face may damage the battery cell, so that the metal cannot be used.

Asbestos or asbestos-containing slate plates have been used as non-metal non-flammable heat-resistant heat insulating materials in the past, but asbestos is harmful to the human body and cannot be used at present.
Calcium silicate plates have been used in the field of building materials as a flame-retardant material to replace asbestos, but calcium silicate is highly alkaline and tends to cause problems such as corrosion when used in batteries and the like.

A non-combustible material obtained by forming a refractory cement material such as alumina cement into a plate shape has no problem in non-combustibility, but is not preferable because it has a high density and increases the weight of the battery pack. In addition, if it is made thin, it is easily damaged and dust is generated even when cutting, so specific work environment measures are required.
Glass wool (glass wool) made of glass fiber, glass paper, glass cloth, etc. are excellent materials as heat insulating materials near room temperature, but because they have good air permeability and low shielding property against gas, high temperature air, combustion gas, flames, etc. There is a problem that it passes through.

As the heat-resistant sheet, an inorganic fiber such as glass fiber containing an inorganic mineral, particularly a clay mineral, has been proposed (Patent Documents 2 and 3).
It is said that the heat-resistant sheets of Patent Documents 2 and 3 can be suitably used mainly for applications such as catalyst carriers.
However, the heat-resistant sheets disclosed in Patent Documents 2 and 3 are inferior in heat insulating properties and lack light weight. In addition, the heat-resistant sheet itself may burn when exposed to high temperatures.

Japanese Unexamined Patent Publication No. 2010-21192 JP-A-7-252794 Japanese Unexamined Patent Publication No. 2013-234410

In view of the above circumstances, it is an object of the present invention to provide a heat-resistant heat-insulating sheet having excellent heat resistance and heat-insulating properties, which is difficult to burn, and which is lightweight, and an assembled battery in which the heat-resistant heat-insulating sheet is inserted between cells. And.

In order to achieve the above problems, the present invention has adopted the following configuration.
[1] A heat-resistant heat-insulating sheet provided on at least one of a low-density layer and a first surface and a second surface of the low-density layer, and having a high-density layer having a higher density than the low-density layer.
The total thickness of the heat-resistant heat-insulating sheet is 0.1 to 2.5 mm.
The combustion heat of the entire heat-resistant heat insulating sheet is 1 MJ / m ² or less.
The low-density layer is a layer in which the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral is less than 50% by mass.
The high-density layer is a layer in which the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral is 50% by mass or more.
The heat insulation is characterized in that the thickness of the high-density layer per layer is equal to or less than the thickness of the low-density layer, and the thickness of at least one of the high-density layers is 0.05 mm or more. Sheet.
[2] The heat-resistant heat insulating sheet according to [1], wherein the inorganic fiber is at least one selected from glass fiber, carbon fiber, glass wool, rock wool, molten rock fiber, ceramic fiber, and silicon carbide fiber.
[3] The heat-resistant heat-insulating sheet according to [1] or [2], wherein the clay mineral is sepiolite.
[4] The heat-resistant heat-insulating sheet according to any one of [1] to [3], wherein the density of the low-density layer is 0.1 to 0.25 g / cm ³ .
[5] The heat-resistant heat-insulating sheet according to any one of [1] to [4], wherein the density of the high-density layer is 0.35 to 2.5 g / cm ³ .
[6] Any one of [1] to [5], wherein the content of the inorganic component in the low-density layer is 80% by mass or more, and the content of the inorganic component in the high-density layer is 90% by mass or more. Heat-resistant insulation sheet described in the section.
[7] The feature is that the plurality of stacked cells and the heat-resistant heat insulating sheet according to any one of [1] to [6] inserted between the plurality of cells are provided. Batteries to be assembled.
[8] Further, the heat-resistant heat insulating sheet according to any one of [1] to [6] is provided, which is arranged outside the cells laminated on the innermost outermost layer of the plurality of cells. ] The assembled battery described in.
[9] The method for producing a heat-resistant heat-insulating sheet according to any one of [1] to [6].
The first surface of the low-density sheet in which the total content of the inorganic fiber and the clay mineral is 80% by mass or more, and the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is less than 50% by mass. And on at least one of the second side,
The density is higher than that of the low-density sheet, the total content of inorganic fibers and clay minerals is 90% by mass or more, and the ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals is 50% by mass or more. A method for manufacturing a heat-resistant and heat-insulating sheet by laminating a certain high-density sheet.
[10] The method for producing a heat-resistant heat-insulating sheet according to any one of [1] to [6].
The first surface of a low-density sheet in which the total content of inorganic fibers and clay minerals is 80% by mass or more, and the ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals is less than 50% by mass. A method for producing a heat-resistant heat insulating sheet, which forms a clay mineral slurry layer on at least one of the second surface and the second surface.

The heat-resistant heat-insulating sheet of the present invention is excellent in heat resistance and heat-insulating properties, is hard to burn, and is lightweight. Further, the assembled battery in which the heat-resistant heat-insulating sheet is inserted between the cells can easily prevent the defect of one cell from extending to the adjacent batteries.

It is sectional drawing of the heat-resistant heat insulating sheet which concerns on 1st Embodiment. It is sectional drawing of the heat-resistant heat insulating sheet which concerns on 2nd Embodiment. It is a block diagram of the assembled battery which concerns on one Embodiment. It is an electron micrograph of the surface of the heat-resistant heat insulating sheet of Example 1. It is an electron micrograph of the vertical cross section of the heat-resistant heat insulating sheet of Example 1. It is the existence probability image of the magnesium element by the X-ray electron microanalyzer (XMA) with respect to the vertical cross section of the heat-resistant heat insulating sheet of Example 1. It is an electron micrograph of the surface of the heat-resistant heat-insulating sheet of Example 2. It is an electron micrograph of the vertical cross section of the heat-resistant heat insulating sheet of Example 2. It is an electron micrograph of the surface of the heat-resistant heat insulating sheet of Comparative Example 1. It is an electron micrograph of the surface of the heat-resistant heat insulating sheet of Comparative Example 3.

Hereinafter, the present invention will be described in detail. The description of the constituent elements described below may be based on typical embodiments or specific examples, but the present invention is not limited to such embodiments. In this specification, the numerical range represented by using "~" means a range including the numerical values before and after "~" as the lower limit value and the upper limit value.

[Heat-resistant heat-insulating sheet]
(First Embodiment)
FIG. 1 is a cross-sectional view of the heat-resistant heat-insulating sheet according to the first embodiment. FIG. 1 emphasizes the thickness direction for convenience of explanation.
As shown in FIG. 1, the heat-resistant heat insulating sheet 10 of the present embodiment is opposite to the low-density layer 1, the first high-density layer 2 provided on the first surface of the low-density layer 1, and the first surface. It includes a second high-density layer 3 provided on a second surface, which is a side surface. The low-density layer 1, the first high-density layer 2, and the second high-density layer 3 are preferably integrated for convenience of handling, but may be simply laminated.

The boundary between the low-density layer 1 and the first high-density layer 2 and the boundary between the low-density layer 1 and the second high-density layer 3 are determined by the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral. Be done.
That is, the low-density layer 1 is the layer in which the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is less than 50% by mass, and the clay mineral in the total content of the inorganic fiber and the clay mineral. The layer having a content ratio of 50% by mass or more is the first high-density layer 2 or the second high-density layer 3.
The boundary between the low-density layer 1 and the first high-density layer 2 and the boundary between the low-density layer 1 and the second high-density layer 3 are parallel to the surface direction of the heat-resistant heat insulating sheet 10.

If a layer in which the content of clay minerals in the total content of inorganic fibers and clay minerals is 50% by mass or more and a layer containing no clay minerals are adjacent to each other, the boundary between the layers remains as it is. It is the boundary between the low-density layer and the high-density layer in the invention.
When the ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals gradually decreases from about 60% by mass to about 40% by mass in the thickness direction, the inorganic fibers and clay minerals The portion where the ratio of the clay mineral content to the total content of the clay mineral is 50% by mass is the end of the high-density layer, and the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral is 50. The portion of less than mass% is the end of the low density layer.

The ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals is determined by determining the abundance ratio of constituent elements using an X-ray microanalyzer, and the constituent elements of standard samples in which the contents of clay minerals and inorganic fibers are known. It is obtained by comparing with the abundance ratio.
The value obtained by the X-ray microanalyzer may be calibrated by the fluorescent X-ray analysis method or the value obtained by the atomic absorption spectrophotometer to further improve the accuracy.
If there is a variation in the ratio of the clay mineral content to the total content of the inorganic fibers and clay minerals on the surface parallel to the surface direction of the heat insulating sheet 10, it is parallel to the surface direction of the heat insulating sheet 10. The average value for the entire surface is taken as the ratio of the content in that surface.

Since the function of the low density layer is exerted by the low density and the function of the high density layer is exerted by the high density, the boundary between the low density layer and the high density layer is preferably as clear as possible. .. That is, it is preferable that the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral changes sharply with the boundary as a boundary. By having a clear boundary, the low-density layer and the high-density layer can easily exert their respective functions, and the overall thickness can be made thinner to exhibit high performance.

The content of the clay mineral contained in the low-density layer 1 is 10% by mass or less with respect to at least one of the contents of the clay mineral contained in each of the first high-density layer 2 and the second high-density layer 3. Is preferable. That is, most of the clay minerals are present in the first high-density layer 2 or the second high-density layer 3.

The ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals in the low density layer 1 is less than 50% by mass, preferably 40% by mass or less in order to achieve low density, and is preferably 30. It is more preferably mass% or less, further preferably 20 mass% or less, and particularly preferably 10 mass% or less. Most preferably, it is substantially zero mass%. The lower the density, the more the thermal conductivity can be suppressed.

The ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals in the first high-density layer 2 and the second high-density layer 3 is 50% by mass or more in order to achieve high density, and 55% by mass. It is preferably% or more, and may be 100% by mass. The higher the proportion of clay mineral content and the higher the density, the easier it is to suppress the permeation of flames and high-temperature gas.
The content of clay minerals contained in each layer is determined by integrating the content of clay minerals on each surface parallel to the surface direction of the heat-resistant heat insulating sheet 10 in the thickness direction.

The distance from the boundary between the low-density layer 1 and the first high-density layer 2 to the boundary between the low-density layer 1 and the second high-density layer 3 is the thickness of the low-density layer 1. Further, the distance from the boundary between the low-density layer 1 and the first high-density layer 2 to the surface of the first high-density layer 2 opposite to the low-density layer 1 is the thickness of the first high-density layer 2. Further, the distance from the boundary between the low-density layer 1 and the second high-density layer 3 to the surface of the second high-density layer 3 opposite to the low-density layer 1 is the thickness of the second high-density layer 3.

As for the thickness of each layer, if each layer is independent and can be easily separated, the pressure applied to the thickness of each layer is low and the layer thickness does not change. JIS L1086 specified non-woven fabric, constant pressure thickness gauge for woven fabric ( The measurement pressure is 0.35 N or less and the measurement diameter is 25.2 mm).
If it is difficult to separate the layers, the thickness of the region where the clay mineral content in the vertical cross-section X-ray microanalyzer image is 50% by mass or more is defined as the thickness of the high-density layer, and the thickness of the region less than 50% by mass is defined as the thickness of the high-density layer. Let this be the thickness of the low density layer.
If the boundary between the high-density layer and the low-density layer in the vertical cross section is clear from the observation image, the thickness of each layer may be measured directly from the observation image of the vertical cross section of the electron micrograph or the optical micrograph.
When the vertical cross section is produced, if there is a risk of changing the layer structure, a resin embedding method or a freeze-cutting method is used to obtain a vertical cross section while maintaining the layer structure and the thickness of each layer. ..

The thickness of the low-density layer 1 is not particularly limited, but it is preferably as thick as possible within the thickness range of the entire heat-resistant heat insulating sheet 10. That is, the thickness of the low-density layer 1 is preferably close to the thickness of the entire heat-resistant heat-insulating sheet 10.
Specifically, it is preferably 0.3 mm or more, and more preferably 0.5 mm or more, within a range of less than 0.05 mm thinner than the entire thickness of the heat-resistant heat insulating sheet 10.
It is easier to obtain a sufficient heat insulating effect when the thickness of the low density layer 1 is made as thick as possible. Further, the weight of the entire heat-resistant heat-insulating sheet 10 can be reduced, and by extension, the weight of the entire assembled battery using the heat-resistant heat-insulating sheet 10 can be reduced.

The thickness of the first high-density layer 2 and the second high-density layer 3 is equal to or less than the thickness of the low-density layer 1, respectively. By making the thickness of both the first high-density layer 2 and the second high-density layer 3 equal to or less than the thickness of the low-density layer 1, the thickness of the entire heat-resistant heat-insulating sheet 10 is reduced, and the entire heat-resistant heat-insulating sheet 10 is reduced. Mass can be suppressed. As a result, the thickness and mass of the entire assembled battery using the heat-resistant heat insulating sheet 10 can be reduced.

Further, the thickness of at least one of the first high-density layer 2 and the second high-density layer 3 is 0.05 mm or more. When the thickness of at least one of the first high-density layer 2 and the second high-density layer 3 is 0.05 mm or more, it is easy to suppress the permeation of flame and high-temperature gas.
The thickness of at least one of the first high-density layer 2 and the second high-density layer 3 is preferably 0.05 to 1 mm, more preferably 0.1 to 0.5 mm.
Both the first high-density layer 2 and the second high-density layer 3 preferably have a thickness of 0.05 mm or more, and both are preferably in the above-mentioned preferable thickness range.

The total thickness of the heat-resistant heat insulating sheet 10 is 0.1 to 2.5 mm. When the thickness of the entire heat-resistant heat-insulating sheet 10 is 0.1 mm or more, it is easy to obtain a sufficient heat-insulating effect. Further, when the thickness is 2.5 mm or less, the thickness of the entire assembled battery using the heat-resistant heat insulating sheet 10 can be reduced.
The total thickness of the heat-resistant heat insulating sheet 10 is preferably 0.1 to 2.5 mm, more preferably 0.5 to 1.5 mm.

The mass per unit area from the boundary between the low-density layer 1 and the first high-density layer 2 to the boundary between the low-density layer 1 and the second high-density layer 3 is the basis weight of the low-density layer 1. Further, the mass per unit area from the boundary between the low-density layer 1 and the first high-density layer 2 to the surface of the first high-density layer 2 opposite to the low-density layer 1 is the basis weight of the first high-density layer 2. Become. Further, the mass per unit area from the boundary between the low-density layer 1 and the second high-density layer 3 to the surface of the second high-density layer 3 opposite to the low-density layer 1 is the basis weight of the second high-density layer 3. Become.

The basis weight of each layer can be determined by taking out each layer independently by an appropriate method such as peeling, cutting, melting, etc., and measuring the mass. When it is difficult to take out each layer individually, the content of the constituent components in the layer is measured by chemical analysis or instrumental analysis, and calculated by the sum of the constituent masses.

Although there is no particular limitation on the basis weight of the low density layer 1 is preferably 10 to 300 g / ^{m 2,} more preferably from 15-280 / ^{m 2,} still to be 20 to 250 g / ^{m 2} preferable.
When the basis weight is not less than the lower limit of the preferable range, the heat insulating effect is easily exhibited, and the strength of the heat resistant heat insulating sheet 10 is also easy to be secured. Further, if it is not more than the upper limit of the preferable range, the thickness of the heat-resistant heat insulating sheet 10 does not become excessive.

Since the low density layer 1 has a low content ratio of clay minerals, it is easy to secure voids between the inorganic fibers, and the density tends to be low.
Density of the low density layer 1 is preferably 0.1~0.25g / cm ^3, more preferably 0.1~0.2g / cm ^3, 0.1~0.17g / cm It is more preferably ³ .
When the density of the low-density layer 1 is equal to or higher than the preferable lower limit value, convection in the layer can be easily suppressed. In addition, it is easy to secure the strength of the heat-resistant heat insulating sheet 10. Further, when the density of the low density layer 1 is not more than a preferable upper limit value, heat transfer can be easily suppressed.

The first high-density layer 2 and the second high-density layer 3 tend to have high densities due to the high content ratio of clay minerals. The first high-density layer 2 and the second high-density layer 3 each have a higher density than the low-density layer 1.
At least one of the density of the first dense layer 2 and the second high-density layer 3, it is preferably 0.3~2.5g / cm ^3, a 0.35~2.5g / cm ³ More preferably, it is 0.4 to 2.5 g / cm ³ .
Further, it is preferable that both the first high-density layer 2 and the second high-density layer 3 have the density in the above preferable range.
When the density of at least one of the first high-density layer 2 and the second high-density layer 3 is at least a preferable lower limit value, it is easy to suppress the permeation of flame and high-temperature gas. Further, when it is not more than the upper limit value, the weight of the entire heat-resistant heat insulating sheet 10 does not become excessive.

The content of the inorganic component in the low-density layer 1 is preferably 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more.
The content of the inorganic component in the first high-density layer 2 and the second high-density layer 3 is preferably 90% by mass or more, more preferably 94% by mass or more, and preferably 96% by mass or more. More preferably, it may be 100% by mass.
Due to the high content of inorganic components in each layer, nonflammability can be ensured.

The content of the inorganic component in each layer is determined by analyzing the amount of the contained inorganic substance by a fluorescent X-ray analysis method.
As for the content of the inorganic component in each layer, each layer may be dissolved and the amount of the contained inorganic substance may be quantified by an ICP analysis method. Further, it may be obtained by subtracting the mass reduction amount as the organic content and the water content by the heating weight loss method. However, if the result is different from the value obtained by the fluorescent X-ray analysis method, the value obtained by the fluorescent X-ray analysis method is regarded as positive.

As the inorganic fibers constituting the heat-resistant heat insulating sheet 10, molten rock fibers such as glass fibers, carbon fibers, glass wool, rock wool and basalt fibers, ceramic fibers such as alumina fibers, silicon carbide fibers and the like can be used. In particular, glass fiber is preferably used because it is inexpensive, does not have conductivity, and has little wear on the cutting blade when cutting a sheet.
As the inorganic fiber, one type may be used alone, or two or more types may be used in combination.

As the glass fiber, in addition to general E glass, high-strength S glass, C glass having excellent acid resistance, and the like can be used. From the viewpoint of cost, it is preferable to use inexpensive E-glass. The cross-sectional shape of the glass fiber is not particularly limited, and a circular or flat shape can be used.
When glass fiber is used as the inorganic fiber, one type of glass fiber may be used alone or two or more types may be used in combination.

The fiber diameter of the inorganic fiber is preferably 3 to 30 μm, more preferably 10 to 30 μm, still more preferably 20 to 30 μm.
When the fiber diameter of the inorganic fiber is not more than a preferable upper limit value, the voids between the inorganic fibers in the low density layer 1 are narrowed, convection in the voids and gas passage are less likely to occur, and a heat insulating effect can be easily obtained. Further, since it is easy to secure contact points and entanglement points between the inorganic fibers, the tensile strength of the entire heat-resistant heat insulating sheet 10 is increased, and handling is facilitated.
In addition, the skin irritation does not become too strong, and it is easy to suppress fluffing and powder falling during the cutting process. In addition, it is easy to avoid that the gaps between the fibers become too large and the passage of heated air and convection in the gaps are likely to occur.

On the other hand, when the fiber diameter of the inorganic fiber is less than 3 μm, “WHO inhalable fiber (a fibrous substance that is inhaled into the body by respiration and reaches the lungs, and has a length of more than 5 μm,” defined by the World Health Organization (WHO). (With a diameter of less than 3 μm and an aspect ratio of more than 3) ”, there are concerns about its impact on health, and there are restrictions on its use. Therefore, it is desirable that the fiber diameter of the inorganic fiber is 3 μm or more.

Further, when the fiber diameter of the inorganic fiber is at least a preferable lower limit value, it is easy to secure the ability to maintain the voids between the fibers in the low density layer 1. Therefore, it is easy to prevent the voids between the fibers from being crushed by the capillary force of the adsorbed water due to moisture absorption and water absorption. Further, it is easy to avoid that the thickness of the entire heat-resistant heat insulating sheet 10 is reduced due to the compressive force between the cells. Therefore, it is possible to suppress a decrease in heat insulating property due to a decrease in thickness of the low density layer 1, and it is possible to avoid an increase in contact points between fibers of the low density layer 1 and an increase in heat transfer coefficient.

As the inorganic fiber, it is also preferable to use an inorganic fiber having a fiber diameter of 3 μm or more and less than 10 μm and an inorganic fiber having a fiber diameter of 10 μm to 30 μm in combination.
By using a combination of inorganic fibers with different fiber diameters, the effect of improving the heat insulating effect and the surface smoothing effect by narrowing the voids between the inorganic fibers, and the improvement of tensile strength by securing the contact points and entanglement points between the inorganic fibers. While obtaining the effect, it is possible to secure the thickness of the low density layer 1 and maintain the voids between the fibers.

The fiber length of the inorganic fiber is preferably 1 to 25.2 mm, more preferably 3 to 20 mm, and even more preferably 5 to 15 mm.
When the fiber length of the inorganic fiber is at least the preferable lower limit value, the strength during the sheet manufacturing process can be ensured.
When the fiber length of the inorganic fiber is not more than the preferable upper limit value, binding does not occur due to twisting of the fiber, and the texture (uniformity of thickness and fiber density) can be kept good.

The clay mineral constituting the heat-resistant heat-insulating sheet 10 has a self-coating ability. Therefore, the first high-density layer 2 and the second high-density layer 3 containing a large amount of clay minerals are high-density layers.
Examples of clay minerals include layered hydrous silicate minerals, for example, hydroferosilicate minerals such as kaolinite, smectite, montmorillonite, sericite, illite, gloconite, chlorite, sepiolite, and talc, and mixtures thereof. ..
Of these, sepiolite is preferable because it has a high coating film-forming ability, has few cracks during drying, and has a high coating film strength after drying.

Sepiolite is a naturally occurring clay mineral that is a hydrous magnesium silicate with a unique chain-like particle structure.
Due to the difference in origin, sepiolite is subjected to hydrothermal action under high temperature and high pressure, has a high degree of crystallinity, and has long fibers and a clear fibrous morphology (conventionally called mountain bark) and shallow seabed. There is a β-type of short fibers (massive or clay-like morphology) with low crystallinity due to sedimentation on the bottom of the lake.

The α-type sepiolite contains a large amount of impurities and contains several to a dozen mass% of crystalline silica such as quartz, which is not preferable for safety to the human body. Therefore, as sepiolite, β-type having a relatively low impurity content is preferable.
Among β-type sepiolites, it is desirable to select and use sepiolites from production areas where the content of crystalline silica is low. Since crystalline silica accelerates the wear of the blade when cutting the sheet, it is preferable that the content of crystalline silica is small.

The content of crystalline silica can be quantified by X-ray powder diffraction by comparing the peak intensity of crystalline silica with the peak intensity of a standard sample.
The content of crystalline silica in the heat-resistant heat insulating sheet 10 is preferably 1% by mass or less, more preferably 0.5% by mass or less, and further preferably 0.2% by mass or less.

Examples of the optional components other than the inorganic fibers and clay minerals constituting the heat-resistant heat insulating sheet 10 include various inorganic or organic binders for binding the inorganic fibers.
As the binder, a binder having binding property, heat resistance, and less corrosiveness to batteries, electrodes, and wiring is preferable.
Examples of the inorganic binder include various inorganic cements and various glasses.

As the organic binder, a thermosetting resin powder, a heat-sealing resin fiber, a resin emulsion, a resin solution, a thermosetting resin, and a thermoplastic resin can be used.
Among them, PVA fiber is preferably used because it is excellent in binding property in comparison with the amount of addition and the amount of heat generated is small. An acrylic resin emulsion or the like is also suitable from the viewpoint of water resistance. A core-sheath type binder fiber having a low melting point resin on the outside and a high melting point resin on the inside is also suitable.
Further, para-aramid fiber, aramid pulp, crystalline polyester, liquid crystal polyester, wood-derived pulp, grass-derived pulp and the like, which are not melt-adhesive but have a high ability to be finely fibrillated and entangled, can also be used. These organic binders may be used alone or in combination.

The greater the amount of the organic binder added, the higher the strength of the heat-resistant heat insulating sheet 10. However, if a large amount of an organic component is contained, the heat resistance is lowered, for example, shrinkage due to heat is likely to occur. Further, when heated by the heat generated by the cell, the organic component may generate heat by oxidation or generate decomposition gas. In that case, it may explode, ignite, or smoke.

The amount of the organic component such as the organic binder in the heat-resistant heat-insulating sheet 10 is such that the combustion heat of the entire heat-resistant heat-insulating sheet 10 is 1 MJ / m ² or less.
The heat of combustion of the entire heat-resistant heat insulating sheet 10 is the sum of the heat of combustion of each organic substance existing in the heat-resistant heat insulating sheet 10, and the heat of combustion of each organic substance is the heat of combustion per unit mass of the organic substance and the organic substance per unit area. It is a value multiplied by the mass of. The heat of combustion of an organic substance does not differ greatly even if the type of the organic substance is different, so that the heat of combustion is related to the amount of the organic component. That is, the heat of combustion is an index of the amount of organic components.

The amount of the organic component in the heat-resistant heat insulating sheet 10 is preferably an amount such that the heat of combustion is 0.75 MJ / m ² or less, and more preferably 0.5 MJ / m ² or less.
If the heat of combustion is controlled within the above range, it is difficult to generate heat or ignite even when exposed to high temperatures. Moreover, even if heat is generated, the amount of heat generated is small. Therefore, it is excellent in nonflammability, and even if one cell generates heat or ignites, it is easy to prevent the influence from affecting the adjacent cell.
The heat of combustion of the sheet is the heat of combustion measured by the measurement of the heat of combustion by the cone calorimeter defined in ISO 5660-1: 2002.

(Second Embodiment)
FIG. 2 is a cross-sectional view of the heat-resistant heat-insulating sheet according to the second embodiment. FIG. 1 emphasizes the thickness direction for convenience of explanation.
As shown in FIG. 2, the heat-resistant heat-insulating sheet 11 of the present embodiment includes a low-density layer 1 and a first high-density layer 2 provided on the first surface of the low-density layer 1. That is, it differs from the heat-resistant heat-insulating sheet 10 of the first embodiment in that the second high-density layer 3 does not exist.
The low-density layer 1 and the first high-density layer 2 are preferably integrated for convenience of handling, but may be simply laminated.

The boundary between the low-density layer 1 and the first high-density layer 2 is determined by the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral, as described in the first embodiment.
The method for determining the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral in each layer and the range of the preferable ratio are also the same as those described in the first embodiment.
Similarly, it is preferable that the boundary between the low-density layer 1 and the first high-density layer 2 is as clear as possible.

The distance from the boundary between the low-density layer 1 and the first high-density layer 2 to the surface of the low-density layer 1 opposite to the first high-density layer 2 is the thickness of the low-density layer 1. Further, the distance from the boundary between the low-density layer 1 and the first high-density layer 2 to the surface of the first high-density layer 2 opposite to the low-density layer 1 is the thickness of the first high-density layer 2.
The method of obtaining each thickness is the same as that described in the first embodiment.

The thickness of the low-density layer 1 is preferably as thick as possible within the range of the thickness of the entire heat-resistant heat-insulating sheet 11 as described in the first embodiment. Specifically, the upper limit is 0.05 mm thinner than the thickness of the entire heat-resistant heat insulating sheet 11, and the thickness is preferably 0.3 mm or more, and more preferably 0.5 mm or more.
The thickness of the first high-density layer 2 is equal to or less than the thickness of the low-density layer 1 and is 0.05 mm or more. The preferred thickness of the first high-density layer 2 is the same as that of the first embodiment.
The total thickness of the heat-resistant heat-insulating sheet 11 is 0.1 to 2.5 mm, and the preferable thickness is the same as that of the heat-resistant heat-insulating sheet 10 of the first embodiment.

The preferred basis weight of the low density layer 1 is the same as that of the first embodiment.
The method of obtaining the basis weight of each layer is the same as that described in the first embodiment.
The preferable densities of the low-density layer 1 and the first high-density layer 2 and the method for obtaining them are the same as those in the first embodiment.

The content of the inorganic component in the low-density layer 1 is preferably 80% by mass or more, preferably 85% by mass or more, and more preferably 90% by mass or more.
The content of the inorganic component in the first high-density layer 2 is preferably 90% by mass or more, more preferably 94% by mass or more, further preferably 96% by mass or more, and 100% by mass. There may be.
The method of determining the content of the inorganic component in each layer is the same as that described in the first embodiment.
As the inorganic fibers and clay minerals constituting the heat-resistant heat insulating sheet 11, the same inorganic fibers and clay minerals constituting the heat-resistant heat insulating sheet 10 can be used, and the preferred embodiment is also the same.

Examples of the components other than the inorganic fibers and clay minerals constituting the heat-resistant heat insulating sheet 11 include various inorganic or organic binders similar to those described in the first embodiment.
Further, the limitation regarding the ratio of the organic component in the heat-resistant heat-insulating sheet 11 is the same as the limitation regarding the ratio of the organic component in the heat-resistant heat-insulating sheet 10. The range of preferred combustion heat is similar.

The heat-resistant heat-insulating sheet 10 of the first embodiment and the heat-resistant heat-insulating sheet 11 of the second embodiment include at least one high-density layer having a thickness of 0.05 mm or more. Since clay minerals close the voids between the inorganic fibers, this high-density layer has a function of suppressing the permeation of flames and high-temperature gas.
Therefore, if the heat-resistant heat-insulating sheet 10 or the heat-resistant heat-insulating sheet 11 is inserted between the cells, it is easy to prevent the fire from spreading to the adjacent cells when one cell ignites.
Further, since the thickness of the high-density layer is limited to the thickness of the low-density layer or less, the total mass is not excessive.

In addition, it has a low-density layer having a thickness equal to or higher than the high-density layer, and there are few clay minerals present in the low-density layer. This low-density layer has a function as a heat insulating layer because the voids between the inorganic fibers are secured.
Therefore, excellent heat insulating properties can be obtained even though the overall thickness is suppressed.
Therefore, if the heat-resistant heat-insulating sheet 10 or the heat-resistant heat-insulating sheet 11 is inserted between the cells, even if one cell generates heat, it is easy to prevent the adjacent cell from deteriorating due to the influence of the heat. ..
Further, since the overall thickness is thin, the thickness of the entire assembled battery using the heat-resistant heat insulating sheet 10 can be suppressed.
Moreover, since it is mainly composed of inorganic components, it is easy to secure nonflammability.

[Manufacturing method of heat-resistant heat insulating sheet]
The method for producing the heat-resistant heat-insulating sheet of the present invention is not particularly limited, but for example, the following production methods 1 and 2 can be preferably applied.

(Manufacturing method 1)
In the production method 1, the total content of the inorganic fiber and the clay mineral is 80% by mass or more, and the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral is less than 50% by mass. The density is higher than that of the low-density sheet on at least one of the first surface and the second surface, and the total content of the inorganic fiber and the clay mineral is 90% by mass or more, which is the total content of the inorganic fiber and the clay mineral. This is a method of laminating high-density sheets having a clay mineral content of 50% by mass or more.

The low-density sheet may be composed of only inorganic fibers, or may contain an optional component such as a binder in addition to the inorganic fibers. Further, the clay mineral may be contained in a range in which the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is less than 50% by mass. In the low-density sheet, the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is preferably low, preferably 40% by mass or less, and more preferably 30% by mass or less. It is more preferably 20% by mass or less, and particularly preferably 10% by mass or less. Most preferably, it does not contain clay minerals. However, since the amount of the organic binder used can be reduced by including the clay mineral, the content of the clay mineral is appropriately adjusted in consideration of the tensile strength of the sheet, the holding power of the fiber, and the like.

The total content of the inorganic fiber and the clay mineral in the low-density sheet (the content of the inorganic fiber when the clay mineral is not contained) is 80% by mass or more, preferably 85% by mass or more. When using an organic binder to facilitate the strength of the low density sheet, the total content of the inorganic fiber and clay mineral in the low density sheet (or the content of the inorganic fiber if the clay mineral is not contained) is It may be 90% by mass or less.

Since the low-density sheet is mainly a portion constituting the low-density layer 1 in the heat-resistant heat insulating sheet 10 or the heat-resistant heat insulating sheet 11, the preferable thickness, basis weight, density of the low-density sheet, and the inorganic fibers constituting the low-density sheet. , A preferred embodiment of the constituent material such as a binder is the same as that described for the low density layer 1 in the embodiment of the heat resistant heat insulating sheet.

The low density sheet can be produced by forming a non-woven fabric of inorganic fibers by a dry method or a wet method. Of these, the wet method is preferable because it is less likely to break the inorganic fibers and it is easy to form a sheet having a good texture.
In the wet method, a non-woven fabric of inorganic fibers can be obtained by papermaking a slurry containing inorganic fibers and, if necessary, an optional component such as a binder.
Examples of the optional component other than the binder include a dispersant, a liquid retaining agent, a viscosity regulator, a pH regulator, a filler and the like.

The inorganic fibers in the obtained non-woven fabric can be bonded by a thermal bond method when a heat-melt type binder is contained.
When the heat-melting type binder is not included, a sheet can be formed by entwining the fibers by adding fibrillated fibers, adding fine fibers, needle punching, water flow entanglement by a water jet, or the like.

The high-density sheet may be composed of only inorganic fibers and clay minerals, or may contain optional components such as a binder in addition to the inorganic fibers and clay minerals. The ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals is 50% by mass or more.
The total content of the inorganic fiber and the clay mineral in the high-density sheet is 90% by mass or more, and may be 100% by mass.
Examples of the optional component other than the binder include a dispersant, a liquid retaining agent, a viscosity regulator, a pH regulator, a filler and the like.

Since the high-density sheet is mainly a portion constituting the first high-density layer 2 or the second high-density layer 3 in the heat-resistant heat insulating sheet 10 or the heat-resistant heat insulating sheet 11, the preferred thickness, basis weight, and density of the high-density sheet are determined. The preferred embodiment of the constituent materials such as the inorganic fibers, clay minerals, and binders constituting the high-density sheet is the same as that described for the first high-density layer 2 or the second high-density layer 3 in the embodiment of the heat-resistant heat insulating sheet. is there.

The high-density sheet can be produced by forming a non-woven fabric sheet of inorganic fibers by a dry method or a wet method, and then impregnating, applying, and printing a slurry of clay minerals.
In order to form a non-woven fabric, the wet method is preferable because the inorganic fibers are less likely to be broken and a sheet having a good texture is easily formed.
In the wet method, a non-woven fabric of inorganic fibers can be obtained by papermaking a slurry containing inorganic fibers and, if necessary, an optional component such as a binder.
Examples of the optional component other than the binder include a dispersant, a liquid retaining agent, a viscosity regulator, a pH regulator, a filler and the like.
A known paper machine can be used in the step of wet-making the inorganic fiber slurry. Examples of the paper machine include a circular net paper machine, an inclined paper machine, a long net paper machine, and a short net paper machine, and the same type or a different type of these paper machines may be combined to perform multi-layer paper making.

The inorganic fibers in the obtained non-woven fabric can be bonded by a thermal bond method when a heat-melt type binder is contained.
When the heat-melting type binder is not included, a sheet can be formed by entwining the fibers by adding fibrillated fibers, adding fine fibers, needle punching, water flow entanglement by a water jet, or the like.

In the production method 1, it is preferable to uniformly impregnate the obtained non-woven fabric sheet with the clay mineral slurry. Therefore, the viscosity of the clay mineral slurry at 25 ° C. by the Brookfield type (B type) viscometer is preferably 1 to 1000 mPa · s, and more preferably 10 to 200 mPa · s.

In order to obtain the required clay mineral carrying amount while maintaining the above-mentioned preferable viscosity, for example, when the clay mineral is β-type sepiolite, the solid content concentration of the slurry is preferably 1 to 30% by mass, preferably 5 to 20% by mass. More preferably.
Dispersants, liquid retention agents, viscosity regulators, pH regulators, organic binders, inorganic binders, fillers and the like may be added to the clay mineral slurry as necessary.

It is preferable that the obtained high-density sheet is stacked on the low-density sheet in an undried state and then heat-dried. The low-density sheet and the high-density sheet can be integrated by stacking them on the low-density sheet and then drying them.
For drying, a general contact or non-contact drying method can be used. Specifically, hot air drying, infrared drying, induction drying, multi-cylinder dryer drying, cylinder dryer drying and the like can be used. The drying temperature is preferably 100 to 180 ° C, more preferably 100 to 150 ° C. The drying time is appropriately adjusted depending on the amount of water in the clay mineral slurry and the drying means, but is preferably 0.5 to 30 minutes, more preferably 1 to 10 minutes.
The heat-resistant heat-insulating sheet 10 can be obtained by laminating the high-density sheets on both sides of the low-density sheet. Further, if the high-density sheet is laminated only on one surface, the heat-resistant heat-insulating sheet 11 can be obtained.

(Manufacturing method 2)
In the production method 2, the total content of the inorganic fiber and the clay mineral is 80% by mass or more, and the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is less than 50% by mass. This is a method of forming a clay mineral slurry layer on at least one of the first surface and the second surface.

The low-density sheet may be composed of only inorganic fibers, or may contain an optional component such as a binder in addition to the inorganic fibers. Further, the clay mineral may be contained in a range in which the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is less than 50% by mass. In the low-density sheet, the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is preferably low, preferably 40% by mass or less, and more preferably 30% by mass or less. It is more preferably 20% by mass or less, and particularly preferably 10% by mass or less. Most preferably, it does not contain clay minerals. However, since the amount of the organic binder used can be reduced by including the clay mineral, the content of the clay mineral is appropriately adjusted in consideration of the tensile strength of the sheet, the holding power of the fiber, and the like.

The total content of the inorganic fiber and the clay mineral in the low-density sheet (the content of the inorganic fiber when the clay mineral is not contained) is 80% by mass or more, preferably 85% by mass or more. In order to facilitate the strength of the low density sheet using the organic binder, the total content of the inorganic fiber and clay mineral in the low density sheet (or the content of the inorganic fiber if the clay mineral is not contained) is 90. It is preferably mass% or less.
Examples of the optional component other than the binder include a dispersant, a liquid retaining agent, a viscosity regulator, a pH regulator, a filler and the like.

Since the low-density sheet is a part constituting the low-density layer 1 in the heat-resistant heat-insulating sheet 10 or the heat-resistant heat-insulating sheet 11, the preferable basis weight and density of the low-density sheet are the low-density layer 1 in the embodiment of the heat-resistant heat insulating sheet. It is the same as explained.
However, when the clay mineral slurry is impregnated in the low-density sheet, the thickness of the low-density layer 1 becomes slightly thinner than the thickness of the low-density sheet, depending on the degree of impregnation.

The inorganic fiber used in the low-density sheet of the production method 2 preferably contains an inorganic fiber having a fiber diameter of 10 μm or less, and more preferably contains an inorganic fiber having a fiber diameter of 3 to 10 μm.
By containing the inorganic fibers having a fiber diameter of 10 μm or less, the voids between the inorganic fibers are narrowed, so that the slurry layer of the clay mineral to be formed tends to stay near the surface of the low-density sheet.
When the slurry layer stays near the surface of the low-density sheet, the slurry layer tends to have a high density, and a high-density layer having a high shielding ability can be easily obtained.
Other preferred embodiments of the constituent materials such as the inorganic fibers and binders constituting the low-density sheet are the same as the preferred embodiments of the constituent materials of the low-density layer 1.
The low-density sheet can be obtained in the same manner as the low-density sheet of Production Method 1.

Examples of the method for forming the clay mineral slurry layer include a method of directly applying and printing the clay mineral slurry, or a method of transferring the once formed clay mineral slurry coating layer.
As a method of applying and printing a clay mineral slurry on a low-density sheet, general coating such as spray coating, curtain coating, roll coating, bar coating, blade coating, flexographic printing, gravure printing, screen printing, offset printing, etc. , Printing method can be mentioned.
When the coating layer of the clay mineral slurry once formed is transferred, the coating layer of the clay mineral slurry can be once formed by coating the clay mineral slurry on the release sheet.
As the release sheet, a polyester film, a polyethylene film, a polypropylene film, a fluororesin film, a silicon resin film, a release paper and the like can be preferably used.
As a method of applying a clay mineral slurry on a release sheet, general coating and printing such as spray coating, curtain coating, roll coating, bar coating, blade coating, flexographic printing, gravure printing, screen printing, offset printing, etc. The method can be mentioned.

The clay mineral slurry layer preferably stays only on the surface of the low density sheet. Therefore, the viscosity of the coating layer at 25 ° C. by a rotating cone-plate rheometer during coating, printing, or transfer is preferably 20 to 100,000 mPa · s, more preferably 100 to 10,000 mPa · s.

In order to obtain the above-mentioned preferable viscosity, it is preferable that the solid content concentration of the clay mineral is high. For example, when the clay mineral is β-type sepiolite, the solid content concentration of the slurry is preferably 10 to 40% by mass, more preferably 15 to 30% by mass.
However, it is also possible to obtain the above-mentioned preferable viscosity by setting the solid content concentration of the slurry to less than 10% by mass and adding an appropriate amount of the viscosity modifier to the slurry.
Further, the coating layer formed on the release sheet may be allowed to stand once to reduce the fluidity, and then transferred onto the low-density sheet. Furthermore, the applied slurry may be semi-dried to increase its viscosity before transfer.
Dispersants, liquid retention agents, viscosity regulators, pH regulators, organic binders, inorganic binders, fillers and the like may be added to the clay mineral slurry as necessary.

It is preferable that the coating layer obtained by transfer is laminated on a low-density sheet in an undried state or in a semi-dried state, then heat-dried, and then the release sheet is peeled off. The coating layer is transferred to the low-density sheet by stacking it on the low-density sheet and then drying it.
The preferred drying conditions are the same as the drying conditions in the production method 1.
The heat-resistant heat-insulating sheet 10 can be obtained by forming a clay mineral slurry layer on both sides of the low-density sheet by transfer or the like. Further, if a clay mineral slurry layer is formed on only one surface by transfer or the like, the heat-resistant heat insulating sheet 11 can be obtained.

(Other manufacturing methods)
In addition, a method of simply stacking a low-density sheet and a high-density sheet, and a method of adhering the low-density sheet and the high-density sheet with an adhesive can be mentioned.

[Battery set]
FIG. 3 is a configuration diagram of the assembled battery 100 according to the embodiment. In the assembled battery of the present embodiment, as shown in FIG. 3, a heat-resistant heat insulating sheet 10 is inserted between a plurality of laminated cell batteries 20. Further, a heat-resistant heat insulating sheet 11 is arranged on the outside of the laminated cell 20 (laminated cell 20 laminated on the outermost layer) of the lowermost layer and the uppermost layer. The heat-resistant heat-insulating sheet 11 is arranged so that the first high-density layer 2 is on the side of the laminated cell 20.
The assembled battery 100 is housed in a metal outer body or the like to form a battery pack.

The laminated cell 20 is a known laminated cell in which an electrode group and an electrolytic solution are housed in a laminate film. As shown in FIG. 3, the positive electrode tab 21 and the negative electrode tab 22 are provided outside the laminated film.
The heat-resistant heat-insulating sheet 10 is inserted so as to block between the laminated cell cells 20 over the entire surface direction, but the positive electrode tab 21 and the negative electrode tab 22 are led out to the outside of the heat-resistant heat-insulating sheet 10. There is.

Since the heat-resistant heat-insulating sheet 10 is inserted between the laminated batteries 20 in the assembled battery 100, even if a problem such as heat generation occurs in one laminated battery 20, the problem is adjacent to the laminated battery 100. It is possible to prevent or delay the adverse effect on the battery 20.
Further, even if a defect such as heat generation occurs in the lowermost layer or the uppermost layer laminated cell 20, it is possible to prevent or delay the defect from adversely affecting other battery packs.

The assembled battery of the present embodiment has an embodiment in which the cell is a laminated cell 20. However, the cell is not limited to the laminated cell, and the electrode group and the electrolytic solution are housed in, for example, a metal case. It may be a single battery. However, since the laminated cell is easily affected by heat, it is preferable to use the laminated cell from the viewpoint of further utilizing the effects of the present invention.

Further, in the present embodiment, one heat-resistant heat-insulating sheet 10 is inserted between each laminated cell 20, but one heat-resistant heat-insulating sheet 11 may be inserted.
However, it is easier to suppress the permeation of flames and high-temperature gas when the heat-resistant heat-insulating sheet 10 is used, even if a problem occurs in the laminated cell 20 on either side. When one heat-resistant heat-insulating sheet 11 is inserted, the effect of suppressing the permeation of flame or high-temperature gas tends to be weakened when a problem occurs in the laminated cell 20 on the side in which the low-density layer 1 is in contact.

A plurality of stacked heat-resistant heat insulating sheets may be inserted between the laminated cell batteries 20. When a plurality of sheets are stacked, only the heat-resistant heat-insulating sheet 10 may be stacked, only the heat-resistant heat-insulating sheet 11 may be stacked, or the heat-resistant heat-insulating sheet 10 and the heat-resistant heat-insulating sheet 11 may be stacked.
From the viewpoint of suppressing the thickness of the entire assembled battery 100, it is preferable to insert only one heat-resistant heat-insulating sheet, and when a plurality of heat-resistant heat-insulating sheets are stacked, it is preferable to stack two heat-resistant heat-insulating sheets 11. When two heat-resistant heat-insulating sheets 11 are stacked, it is preferable to stack them so that the low-density layers 1 are on the inside.

A heat-resistant heat-insulating sheet 10 may be arranged in place of the heat-resistant heat-insulating sheet 11 on the outside of the lowermost layer and the uppermost layer of the laminated cell 20. Further, a plurality of heat-resistant heat-insulating sheets may be arranged. From the viewpoint of suppressing the thickness of the entire assembled battery 100, it is preferable to arrange only one heat-resistant heat-insulating sheet.
Further, it is not necessary to arrange the heat-resistant heat insulating sheet on the outside of the laminated cell 20 of the lowermost layer and the uppermost layer.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples. In addition,% is mass% unless otherwise specified.

[Measurement method, evaluation method]
(Determining the position of the interface between the low-density layer and the high-density layer)
In the heat-insulating heat-insulating sheet of each example, the boundary between the high-density layer and the low-density layer was clear in the electron micrograph of the vertical cross section. It was determined.

(Basis weight, thickness, density)
A precision slicer was used to delaminate the interface between the low-density layer and the high-density layer to separate the low-density layer and the high-density layer.
The basis weight of each separated layer is measured according to the method specified in JIS P 8124: 2011, and then the thickness of the same layer is measured for non-woven fabrics and woven fabrics (measured pressure 0.35 N or less) specified in JIS L1086. , Measurement diameter 25.2 mm). The value obtained by dividing the basis weight by the thickness was defined as the density.
For the high-density layer, the average value of the two high-density layers separated from the low-density layer was used.
The basis weight and thickness of the entire heat-resistant heat-insulating sheet were taken as the total value of each layer, and the density of the entire heat-resistant heat-insulating sheet was taken as the value obtained by dividing the total basis weight by the total thickness.

(Amount of inorganic fiber, clay mineral, and organic binder)
The amounts of inorganic fibers, clay minerals, and organic binders in each layer were calculated from the formulation and the measured basis weight values.
The amounts of inorganic fibers, clay minerals, and organic binders in the entire heat-resistant heat-insulating sheet were the total amount of values obtained for each layer.

(Heat of combustion)
Measured by a cone calorimeter as defined in ISO 5660-1: 2002.

(Measurement of heat shielding property against flame)
Using the heat-resistant heat-insulating sheet of each example as a test piece, the "heat transfer (flame exposure) test" specified in ISO 9151: 1995, JIS T 8021: 2005 was performed. That is, with the surface of the test piece exposed to a flame of a constant heat flux (80 kW / m ² ), the temperature rise is measured by a sensor installed on the back of the test piece, and the test is performed based on the measured temperature rise data. The time (seconds) until the temperature of the back surface of the piece rises from 32 ° C. to 56 ° C. was determined, and the heat transfer index (HTI24) was determined. HTI24 was divided by the thickness of the sample to determine the heat shielding property against flame (HTI24 / thickness: seconds / mm).

The obtained measured values were evaluated according to the following criteria.
◯: The heat shielding property (HTI24) against flame is 7.0 seconds / mm or more.
X: The heat shielding property (HTI24) against flame is less than 7.0 seconds / mm.

(Measurement of high temperature heat shielding property)
Using the heat-resistant heat-insulating sheet of each example as a test piece, ISO 12127-1 “heat transfer test by contact heat” was performed. That is, a cylinder heated to 300 ° C. is brought into contact with the front surface of the test piece, the temperature rise is measured by a sensor installed on the back surface of the test piece, and the temperature of the back surface of the test piece is 10 based on the measured temperature rise data. The time (seconds) until the temperature rises was determined, and the heat shielding property against high temperature (seconds / mm) was determined by dividing by the thickness of the sample.

The obtained measured values were evaluated according to the following criteria.
◯: Heat shielding property against high temperature is 10.0 seconds / mm or more.
X: Heat shielding property against high temperature is less than 10.0 seconds / mm.

(Heat-resistant)
After the measurement of the high-temperature heat-shielding property, when the cylinder sandwiching the heat-resistant heat-insulating sheet was removed, the one that maintained the shape of the sheet was marked with ◯, and the one that collapsed was marked with x.

[Example 1]
(Creation of low density sheet)
88 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 6 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) as a binder component, and core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) 6 parts by mass was put into water.

Further, polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fibers so as to have a solid content of 0.5%, and the glass fibers were dispersed by stirring. A glass fiber slurry containing glass fibers at a concentration of 1.0% was obtained.
The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a low-density sheet. The obtained low-density sheet had a thickness of 0.68 mm, a basis weight of 100 g / m ² , and a density of 0.15 g / cm ³ .

(Formation of high-density sheet)
44 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 44 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 6 μm and a fiber length of 10 mm, polyvinyl as a binder component 6 parts by mass of alcohol fiber (manufactured by Kuraray) and 6 parts by mass of core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) were put into water.

Further, polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fibers so as to have a solid content of 0.5%, and the glass fibers were dispersed by stirring. A glass fiber slurry containing glass fibers at a concentration of 1.0% was obtained.

The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a precursor sheet. The obtained precursor sheet had a thickness of 0.2 mm, a basis weight of 30.9 g / m ² , and a density of 0.15 g / cm ³ .
A 15% slurry of β-type sepiolite (crystalline silica detection limit (0.1%) or less) produced in Spain (viscosity 38 mPa · s by a B-type viscometer at 25 ° C.) was applied to the precursor sheet at 25 ° C. By impregnating 252 g per 1 m ^{2 of the} precursor sheet, an undried high-density sheet was obtained.

(Lamination of low-density sheet and high-density sheet)
The obtained undried high-density sheet was laminated on both sides of the low-density sheet one by one, dried with warm air at 110 ° C. for 10 minutes, and heat-insulated in Example 1 having high-density layers on both surface layers. I got a sheet.

FIG. 4 shows an electron micrograph of the surface of the heat-resistant heat-insulating sheet of Example 1. It can be seen that sepiolite closes most of the voids between the glass fibers.
Further, FIG. 5 shows an electron micrograph of a cross section of the heat-resistant heat-insulating sheet of Example 1. It can be seen that the inside has a low density, and both sides thereof are high-density layers having a thickness of 0.16 mm.

Further, FIG. 6 shows an image of the existence probability of magnesium element by an X-ray electron microanalyzer (XMA) with respect to the cross section of the heat-resistant heat-insulating sheet of Example 1. Since Mg contained in sepiolite is unevenly distributed in the high-density layer on the surface and its thickness is 0.16 mm, sepiolite is unevenly distributed in the high-density layer on the surface, which is a gap between glass fibers. It can be seen that the

[Example 2]
(Creation of low density sheet)
88 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 6 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) as a binder component, and core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) 6 parts by mass was put into water.

Further, polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fibers so as to have a solid content of 0.5%, and the glass fibers were dispersed by stirring. A glass fiber slurry containing glass fibers at a concentration of 1.0% was obtained.
The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a low-density sheet. The obtained low-density sheet had a thickness of 1.0 mm, a basis weight of 150 g / m ² , and a density of 0.15 g / cm ³ .

(Formation of high-density layer)
A thickener (SN Thickener 929 (manufactured by San Nopco)) having a solid content of Sepiolite of 0.005% by mass was added to a 15% slurry of β-type sepiolite produced in Spain (within the detection limit of crystalline silica (0.1%)). The viscosity of the obtained coating material was 12 Pa · s as measured in a 25 ° C. environment with a rotating cone-flat rheometer. This paint was applied with an applicator so as to have a coating amount of 1000 g / m ^2, and a coating layer of sepiolite was formed.

The polyester film on which the coating layer was formed was laminated on both sides of the low-density sheet so that the coating layer was in contact with the low-density sheet, and then dried with warm air at 110 ° C. for 10 minutes. Then, the polyester film was peeled off to form high densities on both surface layers of the low-density sheet to obtain the heat-resistant heat-insulating sheet of Example 2.
Ta.

FIG. 7 shows an electron micrograph of the surface of the heat-resistant heat-insulating sheet of Example 2. It can be seen that the surface is closed with a smooth coating layer of sepiolite.
Further, FIG. 8 shows an electron micrograph of a cross section of the heat-resistant heat-insulating sheet of Example 2. It can be seen that the inside is a low-density layer, and high-density layers with a thickness of 0.085 mm are formed on both surface layers.

[Example 3]
(Creation of low density sheet)
80 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 10 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) as a binder component, and core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) A low-density sheet was obtained in the same manner as in Example 1 except that 10 parts by mass was put into water. The obtained low-density sheet had a thickness of 0.68 mm, a basis weight of 100 g / m ² , and a density of 0.15 g / cm ³ .

(Formation of high-density sheet)
In addition, 40 parts by mass of E glass fiber (manufactured by Owens Corning) having a fiber diameter of 10 μm and a fiber length of 10 mm, 40 parts by mass of E glass fiber (manufactured by Owens Corning) having a fiber diameter of 6 μm and a fiber length of 10 mm, and a binder component. A precursor sheet was obtained in the same manner as in Example 1 except that 10 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) and 10 parts by mass of core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) were used.
The obtained precursor sheet had a thickness of 0.2 mm, a basis weight of 30.9 g / m ² , and a density of 0.15 g / cm ³ .
A 15% slurry of β-type sepiolite (crystalline silica detection limit (0.1%) or less) produced in Spain (viscosity 38 mPa · s by a B-type viscometer at 25 ° C.) was applied to the precursor sheet at 25 ° C. By impregnating 252 g per 1 m ^{2 of the} precursor sheet, an undried high-density sheet was obtained.

(Lamination of low-density sheet and high-density sheet)
The obtained undried high-density sheet was laminated on both sides of the low-density sheet one by one, dried with warm air at 110 ° C. for 10 minutes, and heat-insulated in Example 1 having high-density layers on both surface layers. I got a sheet.

[Example 4]
Examples except that the basalt fiber CBF15-12 (manufactured by Yamanishi Basalt Technology) having a fiber diameter of 15 μm and a fiber length of 13 mm was used instead of the E glass fiber (manufactured by Owens Corning) having a fiber diameter of 10 μm and a fiber length of 10 mm. A low density sheet was obtained in the same manner as in 1.
The obtained low-density sheet had a thickness of 0.70 mm, a basis weight of 100 g / m ² , and a density of 0.14 g / cm ³ .

Further, an undried high-density sheet was prepared in the same manner as in Example 1, one by one was laminated on both sides of the low-density sheet in the same manner as in Example 1, and then dried with warm air at 110 ° C. for 10 minutes. , A heat-resistant heat insulating sheet of Example 1 having high-density layers on both surface layers was obtained.

[Comparative Example 1]
90 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 6 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) as a binder component, and core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) 6 parts by mass was put into water.

Further, polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fibers so as to have a solid content of 0.5%, and the glass fibers were dispersed by stirring. A glass fiber slurry containing glass fibers at a concentration of 1.0% was obtained.
The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a heat-resistant heat-insulating sheet of Comparative Example 1 having a low density as a whole.
The obtained heat-resistant heat-insulating sheet had a thickness of 1.2 mm, a basis weight of 200 g / m ² , and a density of 0.17 g / cm ³ .

FIG. 9 shows an electron micrograph of the surface of the heat-resistant heat-insulating sheet of Comparative Example 1. It can be seen that since the clay mineral such as sepiolite is not used, the voids between the glass fibers are not closed and are opened as they are.

[Comparative Example 2]
90 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 6 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) as a binder component, and core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) 6 parts by mass was put into water.

Further, polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fibers so as to have a solid content of 0.5%, and the glass fibers were dispersed by stirring. A glass fiber slurry containing glass fibers at a concentration of 1.0% was obtained.

The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a precursor sheet. The obtained precursor sheet had a thickness of 1.24 mm, a basis weight of 211 g / m ² , and a density of 0.17 g / cm ³ .
A 15% slurry of β-type sepiolite (crystalline silica detection limit (0.1%) or less) produced in Spain (viscosity 38 mPa · s by a B-type viscometer at 25 ° C.) was applied to the precursor sheet at 25 ° C. 1713 g per 1 m ^{2 of the} precursor sheet was impregnated. Then, it was dried with warm air at 130 ° C. for 10 minutes to obtain a heat-resistant heat-insulating sheet of Comparative Example 2 having a high density as a whole.
The obtained heat-resistant heat-insulating sheet had a thickness of 1.1 mm, a basis weight of 468 g / m ² , and a density of 0.43 g / cm ³ .

[Comparative Example 3]
Instead of 44 parts by mass of E glass fiber (manufactured by Owens Corning) having a fiber diameter of 10 μm and a fiber length of 10 mm and 44 parts by mass of E glass fiber (manufactured by Owens Corning) having a fiber diameter of 6 μm and a fiber length of 10 mm. A precursor sheet was obtained in the same manner as in Example 1 except that 88 parts by mass of E glass fiber (manufactured by Owens Corning) having a diameter of 10 μm and a fiber length of 10 mm was used. The obtained precursor sheet had a thickness of 0.2 mm, a basis weight of 30.9 g / m ² , and a density of 0.15 g / cm ³ .
A 15% slurry of β-type sepiolite (crystalline silica detection limit (0.1%) or less) produced in Spain (viscosity 38 mPa · s by a B-type viscometer at 25 ° C.) was applied to the precursor sheet at 25 ° C. 126 g per 1 m ^{2 of the} precursor sheet was impregnated to obtain an undried, slightly high-density low-density sheet.

(Lamination of low-density sheet and slightly high-density low-density sheet)
The obtained undried, slightly high-density low-density sheet was laminated on both sides of the low-density sheet prepared in the same manner as in Example 1, and then dried with warm air at 110 ° C. for 10 minutes on both surface layers. A heat-resistant heat insulating sheet having a slightly high-density low-density layer was obtained.

FIG. 10 shows an electron micrograph of the surface of the heat-resistant heat-insulating sheet of Comparative Example 3. Since the amount of sepiolite and the like is small, it can be seen that the gaps between the glass fibers are only partially closed and some parts are open as they are.

[Comparative Example 4]
(Creation of low density sheet)
88 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 6 parts by mass of polyvinyl alcohol fiber (manufactured by Kuraray) as a binder component, and core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) 6 parts by mass was put into water, and polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fiber so as to have a solid content of 0.5%, and the mixture was stirred. The glass fibers were dispersed to obtain a glass fiber slurry containing glass fibers at a concentration of 1.0%.

The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a low-density sheet. The obtained low-density sheet had a thickness of 0.31 mm, a basis weight of 45 g / m ² , and a density of 0.15 g / cm ³ .

(Formation of high-density sheet)
44 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 10 μm and a fiber length of 10 mm, 44 parts by mass of E glass fiber (manufactured by Owens Corning) with a fiber diameter of 6 μm and a fiber length of 10 mm, polyvinyl as a binder component 6 parts by mass of alcohol fiber (manufactured by Kuraray) and 6 parts by mass of core-sheath heat-sealed polyester fiber Sofit N720 (manufactured by Kuraray) were put into water.

Further, polyoxyethylene monostearate (manufactured by Kao, "Emanone 3199") dissolved in water was added to the glass fibers so as to have a solid content of 0.5%, and the glass fibers were dispersed by stirring. A glass fiber slurry containing glass fibers at a concentration of 1.0% was obtained.

The obtained glass fiber slurry was wet-made with an inclined wire machine, heated with a cylinder dryer at 130 ° C. for 2 minutes and dried to obtain a precursor sheet. The obtained precursor sheet had a thickness of 0.4 mm, a basis weight of 67.5 g / m ² , and a density of 0.17 g / cm ³ .
A 15% slurry of β-type sepiolite (crystalline silica detection limit (0.1%) or less) produced in Spain (viscosity 38 mPa · s by a B-type viscometer at 25 ° C.) was applied to the precursor sheet at 25 ° C. By impregnating 545 g per 1 m ^{2 of the} precursor sheet, an undried high-density sheet was obtained.

(Lamination of low-density sheet and high-density sheet)
The obtained undried high-density sheet was laminated on both sides of the low-density sheet one by one, dried with warm air at 110 ° C. for 10 minutes, and heat-insulated in Comparative Example 4 having high-density layers on both surface layers. I got a sheet.

The characteristics of each layer of each example and the evaluation results are shown in Tables 1 and 2. The characteristics of the slightly high-density low-density layer in Example 3 are described in the column of high-density layer for convenience.
As shown in Table 1, the heat-resistant heat-insulating sheet of the example had good evaluation results of heat-shielding property against flame, heat-shielding property against high temperature, and heat resistance. On the other hand, the heat-resistant heat-insulating sheet of the comparative example was inferior in the evaluation result of any one or more of the heat-shielding property against flame, the heat-shielding property against high temperature, and the heat resistance.

1 ... low density layer, 2 ... first high density layer, 3 ... second high density layer, 10 ... heat resistant heat insulating sheet,
11 ... Heat resistant heat insulating sheet,
20 ... Laminated cell, 21 ... Positive electrode tab, 22 ... Negative electrode tab, 100 ... Assembly battery

Claims (10)

A heat-resistant heat-insulating sheet provided on at least one of a low-density layer and a first surface and a second surface of the low-density layer, and provided with a high-density layer having a higher density than the low-density layer.
The total thickness of the heat-resistant heat-insulating sheet is 0.1 to 2.5 mm.
The combustion heat of the entire heat-resistant heat insulating sheet is 1 MJ / m ² or less.
The low-density layer is a layer in which the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral is less than 50% by mass.
The high-density layer is a layer in which the ratio of the clay mineral content to the total content of the inorganic fiber and the clay mineral is 50% by mass or more.
The heat insulation is characterized in that the thickness of the high-density layer per layer is equal to or less than the thickness of the low-density layer, and the thickness of at least one of the high-density layers is 0.05 mm or more. Sheet. The heat-resistant heat insulating sheet according to claim 1, wherein the inorganic fiber is at least one selected from glass fiber, carbon fiber, glass wool, rock wool, molten rock fiber, ceramic fiber, and silicon carbide fiber. The heat-resistant heat-insulating sheet according to claim 1 or 2, wherein the clay mineral is sepiolite. The heat-resistant heat-insulating sheet according to any one of claims 1 to ³ , wherein the density of the low-density layer is 0.1 to 0.25 g / cm ³ . The heat-resistant heat-insulating sheet according to any one of claims 1 to 4, wherein the density of the high-density layer is 0.35 to 2.5 g / cm ³ . The heat resistance according to any one of claims 1 to 5, wherein the content of the inorganic component in the low-density layer is 80% by mass or more, and the content of the inorganic component in the high-density layer is 90% by mass or more. Insulation sheet. An assembled battery comprising a plurality of stacked cells and a heat-resistant heat insulating sheet according to any one of claims 1 to 6, which is inserted between the plurality of cells. The set according to claim 7, further comprising the heat-resistant heat insulating sheet according to any one of claims 1 to 6, which is arranged outside the cells laminated on the innermost outermost layer of the plurality of cells. battery. The method for manufacturing a heat-resistant heat-insulating sheet according to any one of claims 1 to 6.
The first surface of the low-density sheet in which the total content of the inorganic fiber and the clay mineral is 80% by mass or more, and the ratio of the content of the clay mineral to the total content of the inorganic fiber and the clay mineral is less than 50% by mass. And on at least one of the second side,
The density is higher than that of the low-density sheet, the total content of inorganic fibers and clay minerals is 90% by mass or more, and the ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals is 50% by mass or more. A method for manufacturing a heat-resistant and heat-insulating sheet by laminating a certain high-density sheet. The method for manufacturing a heat-resistant heat-insulating sheet according to any one of claims 1 to 6.
The first surface of a low-density sheet in which the total content of inorganic fibers and clay minerals is 80% by mass or more, and the ratio of the content of clay minerals to the total content of inorganic fibers and clay minerals is less than 50% by mass. A method for producing a heat-resistant heat insulating sheet, which forms a clay mineral slurry layer on at least one of the second surface and the second surface.