Inorganic powder sheet and method for manufacturing same

Abstract

Provided are: an inorganic powder sheet for which heat insulating properties are improved without increasing thickness; and a method for manufacturing said sheet. This inorganic powder sheet with heat insulating properties includes an inorganic powder and organic fibers. The thermal conductivity is 0.15 W / m∙K or less, and the average thickness is 0.06-0.30 mm. When one surface of the inorganic powder sheet is heated to approximately 1000°C as a heated surface, the front-to-back temperature difference between the heated surface and a back surface opposite the heated surface is 400-500°C. Due to this configuration, it is possible to realize a thin inorganic powder sheet.

Description

Inorganic powder sheet and manufacturing method thereof

[0001] The present disclosure relates to an inorganic powder sheet and a manufacturing method thereof, and more particularly to an inorganic powder sheet that can be used for insulating a lithium ion secondary battery, for example, and a manufacturing method thereof.

[0002] Heat insulating sheets for insulating heat-generating bodies are used in various applications. For example, in automotive or stationary power supply devices that stack multiple secondary battery cells, a large number of secondary battery cells are often used due to the demand for higher output and higher capacity. In such power supply devices, there is a concern that some secondary battery cells may become too hot (referred to as "thermal runaway" in this disclosure) for some reason, which could adversely affect adjacent secondary battery cells. Therefore, to protect surrounding secondary battery cells in the event of thermal runaway, it is necessary to thermally insulate adjacent secondary battery cells from each other. Specifically, sheet-like insulating materials called separators or spacers (referred to as "heat insulating sheets" in this disclosure) are interposed between the secondary battery cells.

[0003] However, as power supply devices become higher in output and capacity, the heat generated by individual cells (i.e., lithium-ion secondary batteries) also increases. This demands a corresponding increase in the insulating performance of the heat-insulating sheets. While increasing the thickness of the heat-insulating sheets or the number of sheets is one way to improve the insulating performance, both of these methods increase the overall thickness of the heat-insulating sheets, which increases the overall size and weight of the power supply device in proportion to the number of secondary battery cells. In particular, power supply devices for vehicles, such as those used in automobiles, are required to be smaller and lighter in order to improve fuel efficiency and secure cabin space. Therefore, to maintain the same overall size and weight as the previous power supply device, the volume occupied by the secondary battery cells must be reduced, resulting in a decrease in battery capacity.

[0004] Furthermore, when a secondary battery cell experiences thermal runaway, the abnormally heated secondary battery cell may cause an increase in internal pressure, or outgassing due to decomposition of the electrolyte, which may damage the insulating material. It would be even more useful to provide an insulating sheet with the functionality to prevent the aforementioned damage from occurring in insulating materials used in such applications.

[0005] Japanese Patent Publication No. 2023-504272 Japanese Patent No. 7132417 Japanese Patent Publication No. 2021-531631 Japanese Patent No. 7181179 International Publication No. W02024 / 038843 Japanese Patent Application Laid-Open No. 2024-91065

[0006] One object of the present disclosure is to provide an inorganic powder sheet and a manufacturing method thereof that improves thermal insulation without increasing thickness. Another object is to provide an inorganic powder sheet and a manufacturing method thereof that is lightweight. Yet another object is to provide an inorganic powder sheet with improved thermal insulation. Yet another object is to provide an insulating sheet that has increased burst strength and is less likely to break even if an adjacent secondary battery cell experiences thermal runaway while maintaining its insulating performance. Note that the description of these objects and objects of the present disclosure does not preclude the existence of other objects and objects. Furthermore, it is not necessary for one embodiment of the present disclosure to solve all of these objects. Furthermore, other objects can be extracted from the description of the specification, drawings, and claims of the present disclosure. Means for solving the problem and effects of the invention

[0007] An inorganic powder sheet according to one embodiment is an inorganic powder sheet having heat insulating properties, comprising inorganic powder and organic fibers, having a thermal conductivity of 0.10 W / m K to 0.18 W / m K, an average thickness of 0.06 mm to 0.30 mm, and when one side of the inorganic powder sheet is used as a heating surface and heated to approximately 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 400°C to 500°C. With the above configuration, a thin inorganic powder sheet can be realized.

[0008] In addition, the inorganic powder sheet according to another embodiment has a basis weight of 100 g / m 2 ~400g / m 2 is.

[0009] Furthermore, in the inorganic powder sheet according to another embodiment, in any one of the above embodiments, the content of the inorganic powder is 55% by weight or more.

[0010] Furthermore, in any one of the above-mentioned inorganic powder sheets according to another embodiment, the volume resistivity is 1.0×1012 Ω・cm~8.0×10 13 It is Ω·cm.

[0011] Furthermore, in any of the above-described inorganic powder sheets according to another embodiment, the burst strength is 100 kPa to 185 kPa. By increasing the burst strength in this manner, the sheet is less likely to be damaged by an increase in internal pressure, outgassing, or the like.

[0012] Furthermore, in another embodiment of the inorganic powder sheet, in any one of the above embodiments, the inorganic powder is at least one of silica, alumina, mica, titanium oxide, sepiolite, zeolite, kaolin, bentonite, talc, and vermiculite.

[0013] Furthermore, in another embodiment of the inorganic powder sheet, in any of the above embodiments, the organic fibers include one or more of para-aramid fibers, para-aramid pulp, meta-aramid pulp, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, flame-retardant rayon fibers, and natural fibers.

[0014] Furthermore, in the inorganic powder sheet according to another embodiment, in any one of the above embodiments, the inorganic powder sheet is a wetlaid paper sheet.

[0015] Furthermore, in any of the above-mentioned embodiments, the inorganic powder sheet according to another embodiment has a basis weight of 135 g / m 2 ~200g / m 2 The thickness is 0.10 mm to 0.18 mm, the thermal conductivity is 0.10 W / m K to 0.18 W / m K, and when one side is used as a heating surface and heated to approximately 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 415°C to 500°C.

[0016] Furthermore, in any of the above-described embodiments, the inorganic powder sheet according to another embodiment has a volume resistivity of 1.0×10 12 Ω・cm~8.0×10 13 It is Ω·cm.

[0017] Furthermore, in any of the above-mentioned embodiments, the inorganic powder sheet according to another embodiment has a basis weight of 135 g / m 2 ~200g / m 2The thickness is 0.11 mm to 0.18 mm, the thermal conductivity is 0.10 W / m K to 0.18 W / m K, when one side is used as a heating surface and heated to about 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 415°C to 460°C, and the volume resistivity is 1.0 × 10 12 Ω・cm~8.0×10 13 The sheet has a compressive strength of Ω·cm and a burst strength of 100 kPa to 185 kPa. This configuration makes it possible to realize an inorganic powder sheet that is lightweight and thin, yet has a large temperature difference between the front and back sides when heated with a 1000°C burner, and is resistant to damage due to internal pressure increases, outgassing, etc.

[0018] Furthermore, a method for producing an inorganic powder sheet according to another embodiment is a method for producing an inorganic powder sheet having heat insulating properties, and includes the steps of blending organic fibers with inorganic powder, dispersing the mixture in water to form a slurry, and wet-laid papermaking the slurry to obtain a sheet material, and thermally calendering the sheet material to a mean thickness of 0.06 mm to 0.30 mm, thereby realizing a thin inorganic powder sheet.

[0019] Furthermore, in another embodiment of the method for manufacturing an inorganic powder sheet, in any of the above embodiments, the thermal conductivity is 0.10 W / m·K to 0.18 W / m·K, and when one side of the inorganic powder sheet is used as a heating surface and heated to approximately 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 400°C to 500°C.

[0020] Furthermore, in another embodiment of the method for manufacturing an inorganic powder sheet, in any of the above embodiments, the inorganic powder is at least one of silica, alumina, mica, titanium oxide, sepiolite, zeolite, kaolin, bentonite, talc, and vermiculite.

[0021] Furthermore, in another embodiment of the method for manufacturing an inorganic powder sheet, in any of the above embodiments, the organic fibers include one or more of para-aramid fibers, para-aramid pulp, meta-aramid pulp, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, flame-retardant rayon fibers, and natural fibers.

[0022] 1 is an exploded perspective view showing a power supply device according to a first embodiment of the present disclosure; FIG. 2 is a schematic diagram showing a burner test at 1000° C.; FIG. 3 is a schematic diagram showing a burner test at 600° C.;

[0023] Embodiments of the present disclosure will be described below with reference to the drawings. However, the embodiments described below are merely examples for embodying the technical concepts of the present disclosure, and the present disclosure is not limited to the following. Furthermore, this specification does not in any way specify the components set forth in the claims as components of the embodiments. The dimensions, materials, shapes, relative positions, etc. of components described in the embodiments are not intended to limit the scope of the present disclosure, and are merely illustrative unless otherwise specified. The size and relative positions of components shown in the drawings may be exaggerated for clarity. Furthermore, in the following description, the same names and symbols indicate identical or similar components, and detailed descriptions will be omitted as appropriate. Furthermore, the elements constituting the present disclosure may be configured with the same component, with one component serving multiple functions, or conversely, the function of one component may be shared by multiple components. In this disclosure, the indefinite prime tone (e.g., "a" or "an") is not excluded from being plural when translated. [Embodiment 1]

[0024] The inorganic powder sheet according to an embodiment of the present disclosure uses a lightweight, thin paper sheet made by a wet papermaking process while incorporating a high content of inorganic powder, resulting in a heat-insulating sheet with high heat-insulating performance. Such an inorganic powder sheet can be used appropriately in applications requiring heat insulation and preventing fire spread. For example, it is suitable for applications such as lithium-ion secondary batteries, where prevention of fire spread is required from a safety perspective when high temperatures are reached, such as during thermal runaway. Here, we describe an example in which an inorganic powder sheet is used as a spacer between adjacent secondary battery cells in a power supply device in which multiple rectangular secondary battery cells are stacked and connected in series or parallel. Such power supply devices are used as power sources for electric vehicles, hybrid vehicles, electric buses, trains, electric carts, and other electric vehicles, as backup power sources for factories and base stations, and even as home storage batteries.

[0025] FIG. 1 shows an exploded perspective view of a power supply device according to a first embodiment. The power supply device 100 shown in this figure includes multiple secondary battery cells 20 and an inorganic powder sheet 10 interposed between the secondary battery cells 20. The secondary battery cells 20 have rectangular exterior cans 21 with a bottom, and multiple cells are stacked with their main surfaces facing each other. The stacking is performed, for example, by covering both end faces of a battery stack 25 formed by stacking the secondary battery cells 20 with end plates 30 and fastening the end plates 30 together with fastening members. The battery stack 25 is also fixed to a base plate 40 as needed. The base plate 40 can function as a cooling plate, for example, by circulating a refrigerant therethrough.

[0026] Each secondary battery cell 20 houses an electrode assembly inside an outer can 21, and the open end is sealed with a sealing plate 22. In FIG. 1 , the sealing plate 22, which is located on the top surface of the outer can 21, is provided with a pair of electrodes 23 and an explosion-proof valve 24. The multiple secondary battery cells 20 are electrically connected to each other in series and / or parallel by connecting the electrodes 23 to each other with bus bars. The explosion-proof valve 24 is a component that opens when it detects an increase in the internal pressure of the outer can 21 and discharges high-pressure gas from inside the outer can 21. Each explosion-proof valve 24 is connected to a gas duct for guiding high-pressure gas to the outside as necessary.

[0027] An inorganic powder sheet 10 is interposed between adjacent secondary battery cells 20. The inorganic powder sheet 10 is also called a spacer or separator, and provides insulation to prevent short-circuiting of the outer casings 21 between adjacent secondary battery cells 20. (Inorganic Powder Sheet 10)

[0028] The inorganic powder sheet has heat insulating properties and electrical insulation properties. As an indicator of insulation properties, the volume resistivity is 1.0×10 12 Ω・cm~8.0×10 13 The resistance is Ω·cm. Heat resistance will be described later. The inorganic powder sheet is a wet-laid paper sheet. This inorganic powder sheet contains inorganic powder and organic fibers. The inorganic fibers function as a filler, and the organic fibers function as a binder. (Inorganic Powder)

[0029] Examples of inorganic powders that can be used include silica, alumina, mica, titanium oxide, sepiolite, zeolite, kaolin, bentonite, talc, and vermiculite. Kaolin is preferred. It is also preferred to increase the kaolin content to produce an inorganic powder sheet with a high kaolin content.

[0030] The content of inorganic powder is 55% by weight or more, preferably 80% by weight or more. For example, kaolin is contained in an amount of 60% by weight, more preferably 80% by weight. (Organic Fiber)

[0031] Examples of organic fibers that can be used include para-aramid fibers, para-aramid pulp, meta-aramid pulp, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, flame-retardant rayon fibers, and natural fibers. Examples of natural fibers that can be used include natural cellulose fibers such as wood (coniferous or broadleaf) pulp and cotton linters. The fiber form is not limited, and it may be fibrillated. JIS P 8121 (2012) Canadian Standard Freeness Method can be suitably used to determine the degree of fiber fibrillation. The organic fiber content is preferably 0 to 40% by weight, more preferably 5 to 20% by weight. A content below the upper limit of the above range tends to suppress deformation during compression and reduce deterioration in heat resistance. It is also preferable to use organic fibers with excellent flame retardancy or organic fibers containing a flame retardant.

[0032] The basis weight is 100 g / m 2 ~400g / m 2 , preferably 135 g / m 2 ~200g / m 2 Let's say.

[0033] The inorganic powder sheet has an average thickness of 0.06 mm to 0.30 mm, preferably 0.10 mm to 0.18 mm. By forming the inorganic powder sheet into a thin film in this way, it can be used in a space-saving manner, and when used as a heat insulating sheet for a power supply device, for example, it is possible to avoid an increase in the size of the device when the inorganic powder sheet is interposed between multiple secondary battery cells and stacked.

[0034] Furthermore, by maintaining a certain level of density, deformation can be suppressed, and in particular, deterioration of thermal insulation performance due to changes in thickness can be suppressed. In particular, when the inorganic powder sheet is interposed between secondary battery cells, the secondary battery cells expand during use. The expansion presses the inorganic powder sheet, resulting in a decrease in thickness and a decrease in thermal insulation performance. Therefore, by increasing the density of the inorganic powder sheet according to this embodiment, such changes in thickness can be suppressed, allowing the inorganic powder sheet to exhibit thermal insulation performance even when the secondary battery cells expand.

[0035] Furthermore, it is preferable that the inorganic powder sheet is not subjected to a treatment such as a coating on its surface. In particular, if a coating that hardens the surface of the inorganic powder sheet is applied, the inorganic powder sheet loses its flexibility, making it difficult to wind into a roll, and reducing productivity and handling. Therefore, the inorganic powder sheet according to this embodiment is not subjected to a coating treatment that hardens the surface, making it easy to provide in a large area, such as in a roll shape, and improving handling properties suitable for management, transportation, etc. (Thermal insulation performance)

[0036] The thermal conductivity of the inorganic powder sheet is 0.18 W / m K or less, preferably 0.15 W / m K or less and 0.05 W / m K or more, and more preferably 0.14 W / m K or less and 0.10 W / m K or more. For example, the improved unsteady plane heat source method can be used to measure thin film materials with low thermal conductivity.

[0037] Furthermore, the inorganic powder sheet may be formed as a single layer or may have a laminated structure of multiple layers. This allows different properties to be added. For example, an additional layer having flame retardancy or flame resistance may be added. By adding a material with excellent flame retardancy in this way, it is possible to suppress the spread of fire at high temperatures. For example, the additional layer may be made of inorganic fillers such as silicate minerals, metal oxides, and graphite, inorganic fibers such as glass fibers, organic fibers with excellent flame retardancy such as aramid, and organic fibers containing flame retardants. (Heating Test)

[0038] A heating test was conducted to measure the thermal insulation performance of an inorganic powder sheet. Specifically, as shown in FIGS. 2 and 3, one side (first side; right side in the figure) of an inorganic powder sheet 100 was used as the heating surface, and the sheet was heated to approximately 1000°C or approximately 600°C using a heating device BN. In the 1000°C heating test shown in FIG. 2, the inorganic powder sheet 100 was held vertically, while in the 600°C heating test shown in FIG. 3, the inorganic powder sheet 100 was held at a 45° inclination. A burner can be used as the heating device BN. The heating surface is heated by the heating device BN, and the heating temperature is measured by a temperature sensor TS1. Meanwhile, a temperature sensor TS2 is placed on the temperature measurement surface (second side; left side in the figure) behind the heating surface. Thermocouples or the like can be used as the temperature sensors TS1 and TS2. The thermocouple is fixed with a clamp or the like and physically contacts the temperature measurement surface. In this state, the first surface is heated by the heating means BN, and while the temperature sensor TS1 confirms that the heating temperature is being maintained, the temperature of the second surface is measured by the temperature sensor TS2. Then, the temperature difference ΔT between the first surface and the second surface 10 minutes after the start of the test is calculated. The higher this temperature difference, the better the heat insulating performance. In the inorganic powder sheet according to this embodiment, the temperature difference ΔT between the first surface and the second surface is set to 400°C to 500°C, preferably 415°C to 500°C.

[0039] In the burner test, since it is difficult to confirm significant differences due to the blending of thin sheets, the test is conducted after the thickness is increased to 0.3 mm or more by stacking multiple inorganic powder sheets as necessary. The stacked sheets are physically fixed by pressing the corners with clamps or the like. [Method for manufacturing inorganic powder sheets]

[0040] Wet papermaking can be used to produce such inorganic powder sheets. For example, inorganic powders and organic fibers are dispersed in water to form a papermaking slurry, which is then dehydrated and dried on a wire mesh to obtain a wet papermaking sheet. Known papermaking machines can be used, including Fourdrinier papermaking machines, cylinder papermaking machines, tilted short wire papermaking machines, and twin-wire papermaking machines. Furthermore, the density of the sheet can be adjusted as needed using equipment such as a wet press or touch press.

[0041] The precursor sheet thus obtained by wet-laid papermaking of inorganic powder and organic fiber is then subjected to heat and pressure processing. For example, to increase the density of the wet-laid precursor sheet, a calendering process may be further performed. In this case, the calendering process may be continuous with or independent of the wet-laid papermaking process. Known calendering devices may be used, such as metal rolls, resin rolls, rubber rolls, and double-belt presses. The calendering device may be heated to increase density and processing efficiency. Preferably, the calendering process is performed at a temperature below the melting point of the organic fiber to be blended. This results in an inorganic powder sheet that maintains high thermal insulation and heat resistance while exhibiting minimal compression deformation.

[0042] By combining inorganic powder and organic fibers in this way, it is possible to improve the heat insulating performance and easily impart flame retardancy. Combining only inorganic materials raises concerns about breakage during expansion of the secondary battery cell and a decrease in heat insulating performance due to thickness changes. Furthermore, flexibility is insufficient, making it difficult to provide a large area such as a roll shape in terms of strength. In contrast, the inorganic powder sheet according to this embodiment combines inorganic powder and organic fibers, which allows it to maintain a certain degree of flexibility to accommodate a roll shape, while suppressing thickness changes and exhibiting high heat insulating performance. [Example]

[0043] Using the above manufacturing method, inorganic powder sheets according to Examples 1 to 5 were produced. In addition, inorganic powder sheets according to Comparative Examples 1 to 4 were produced. The compositions and manufacturing methods of the inorganic powder sheets according to these examples are shown in Tables 1 and 2.

[0044]

[0045]

[0046] The basis weight of each example was measured in accordance with JIS P 8124 (2011). The thickness and density of the inorganic powder sheet were measured in accordance with JIS P 8118 (2014). Furthermore, thermal conductivity measurements were performed using the improved unsteady plane heat source method in accordance with ASTM D7984 (2016). A C-Therm TCi thermal conductivity measuring device was used. A sample sheet was placed on a sensor unit equipped with a built-in heater, and a 500 g weight was placed on the sample. Heating was initiated at a steady output in this state, and the change in sensor temperature over time was measured. The thermal effusivity and thermal conductivity were measured using the following equation (1).

[0047]

[0048] Furthermore, the tensile strength was measured in accordance with JIS P 8113 (2006).

[0049] Furthermore, the volume resistivity was measured in accordance with JIS K6911 "General testing methods for thermosetting plastics" (room temperature, applied voltage of 500 V). The dielectric breakdown strength AC was measured in accordance with JIS C2110-1 "Solid electrical insulating materials - Testing methods for dielectric breakdown strength - Part 1: Testing by application of commercial frequency AC voltage", and the dielectric breakdown strength DC was measured in accordance with JIS C2110-2 "Solid electrical insulating materials - Testing methods for dielectric breakdown strength - Part 2: Testing by application of DC voltage" (room temperature, application time of each voltage: 100 [V / sec]).

[0050] Furthermore, the bursting strength was tested in accordance with JIS P8112 "Paper - Bursting strength test method."

[0051] Specifically, in Example 1, 80 wt% of kaolin as inorganic powder, 10 wt% of aramid fiber as organic fiber, and 10 wt% of PET fiber were dispersed in water to form a papermaking slurry. The obtained papermaking slurry was subjected to wet papermaking to obtain an inorganic powder precursor sheet. The obtained inorganic powder precursor sheet was subjected to thermal calendering by passing it between a pair of metal rolls to obtain a basis weight of 180 g / m. 2 Thus, an inorganic powder sheet according to Example 1 having a thickness of 0.12 mm was obtained.

[0052] Similarly, in Example 2, 80 wt % of talc, 10 wt % of aramid fiber, and 10 wt % of PET fiber were used as inorganic powders, and these were dispersed in water to form a papermaking slurry. The obtained papermaking slurry was wet-processed to obtain an inorganic powder precursor sheet. The obtained inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 188 g / m. 2 Thus, an inorganic powder sheet according to Example 2 having a thickness of 0.11 mm was obtained.

[0053] Furthermore, in Example 3, 60 wt % of vermiculite and 20 wt % of silica were used. Furthermore, 10 wt % of aramid fiber and 10 wt % of PET fiber were used as organic fibers. These were dispersed in water to form a papermaking slurry. The obtained papermaking slurry was subjected to wet papermaking to obtain an inorganic powder precursor sheet. The obtained inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 171 g / m. 2 Thus, an inorganic powder sheet according to Example 3 having a thickness of 0.11 mm was obtained.

[0054] In Example 4, 60% by weight of kaolin, 30% by weight of aramid fiber, and 10% by weight of PET fiber were dispersed in water to form a papermaking slurry, and the resulting papermaking slurry was subjected to wet papermaking to obtain an inorganic powder precursor sheet. The resulting inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 150 g / m. 2 Thus, an inorganic powder sheet according to Example 4 having a thickness of 0.13 mm was obtained.

[0055] In Example 5, 60 wt % of kaolin, 30 wt % of aramid fiber, and 10 wt % of PET fiber were dispersed in water to form a papermaking slurry, and the resulting papermaking slurry was subjected to wet papermaking (however, the papermaking speed was slower than in Example 4) to obtain an inorganic powder precursor sheet. The resulting inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 182 g / m. 2 Thus, an inorganic powder sheet according to Example 5 having a thickness of 0.16 mm was obtained.

[0056] On the other hand, in Comparative Example 1, 50 wt% of kaolin, 20 wt% of aramid fiber, and 30 wt% of PET fiber were used. These were dispersed in water to form a papermaking slurry, and the resulting papermaking slurry was wet-processed to obtain an inorganic powder precursor sheet. The resulting inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 142 g / m. 2 Thus, an inorganic powder sheet according to Comparative Example 2 having a thickness of 0.12 mm was obtained.

[0057] Furthermore, in Comparative Example 2, 60 wt% of kaolin, 20 wt% of silica, 10 wt% of aramid fiber, and 10 wt% of PET fiber were used and dispersed in water to form a papermaking slurry, and the obtained papermaking slurry was subjected to wet papermaking to obtain an inorganic powder precursor sheet. The obtained inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 137 g / m. 2 Thus, an inorganic powder sheet according to Comparative Example 3 having a thickness of 0.14 mm was obtained.

[0058] Similarly, in Comparative Example 3, 80 wt% of vermiculite as inorganic powder, 10 wt% of aramid fiber as organic fiber, and 10 wt% of PET fiber were dispersed in water to form a papermaking slurry. The obtained papermaking slurry was subjected to wet papermaking to obtain an inorganic powder precursor sheet. The obtained inorganic powder precursor sheet was subjected to thermal calendering in the same manner as in Example 1 to obtain a sheet having a basis weight of 176 g / m. 2 Thus, an inorganic powder sheet according to Comparative Example 4 having a thickness of 0.11 mm was obtained.

[0059] In Comparative Example 4, a mica sheet WW-FMS-L manufactured by Wide Work Co., Ltd. was used. This mica sheet is said to contain mica and a few percent of silicone adhesive. The basis weight is 656 g / m 2 The thickness was 0.33 mm.

[0060] Heating tests were also conducted on the inorganic powder sheets according to each Example and Comparative Example. In the first heating test at 1000°C, three inorganic powder sheets according to Examples 1 to 3 were stacked to match the thickness of the inorganic powder sheet used in Comparative Example 1 (0.33 mm). Furthermore, since measurements were impossible for Comparative Example 4 (due to insufficient heat resistance and deformation of the thermocouple due to the heat from the burner, making accurate temperature measurements impossible), a second heating test was also conducted at a heating temperature of approximately 600°C. In the second heating test, one inorganic powder sheet according to Examples 1 to 3 was used.

[0061] The properties of the inorganic powder sheets according to the examples and comparative examples and the results of the heating test are shown in Tables 3 and 4.

[0062]

[0063]

[0064] As shown in Tables 3 and 4, it was confirmed that the inorganic powder sheets according to Examples 1 to 5 exhibited high heat resistance. In particular, the temperature difference ΔT between the front and back surfaces in the first heating test, in which the sheets were heated at approximately 1000°C, was approximately 415°C or higher, confirming that the sheets exhibited extremely high heat resistance. Furthermore, in the 600°C burner test, Examples 1 to 5 exhibited high heat resistance even when compared to the mica sheet of Comparative Example 4, even when the thickness was about 1 / 2 to 1 / 3 of that of the mica sheet. For this reason, the inorganic powder sheets according to Examples 1 to 3 are advantageous in that they can be easily formed into a roll shape with increased flexibility, are excellent in portability and handling, and can be provided in larger areas.

[0065] Furthermore, although Examples 4 and 5 have inferior burst strength compared to Comparative Example 1, they exhibit a high front-to-back temperature difference ΔT in the 1000°C burner test and the 600°C burner test. Therefore, when a secondary battery cell experiences thermal runaway, it is possible to provide an inorganic powder sheet that suppresses heat propagation to adjacent secondary battery cells and is less likely to be damaged by internal pressure increases, outgassing, etc.

[0066] Even when compared to Comparative Example 4, the burst strength is inferior, but the basis weight is small, making it possible to reduce the weight and thickness, and when placing secondary battery cells in a power supply device with a certain volume, more secondary battery cells can be placed, making it possible to increase the capacity of the power supply device.

[0067] The inorganic powder sheet and its manufacturing method disclosed herein can be used as a heat insulating sheet sandwiched between heat generating elements. For example, the inorganic powder sheet can be used as a heat insulating spacer between secondary battery cells or secondary battery cell modules, a buffer sheet between an explosion-proof valve and a gas duct, or a heat insulating material to protect drive circuits such as an ECU. It can also be used in construction applications as a heat insulating material to prevent fires from spreading, a heat-resistant material, and other building materials.

[0068] REFERENCE SIGNS LIST 100: inorganic powder sheet 10: inorganic powder sheet 20: secondary battery cell 21: outer can 22: sealing plate 23: electrode 24: explosion-proof valve 25: battery stack 30: end plate 40: base plate BN: heating means TS1, TS2: temperature sensors

Claims

1. An inorganic powder sheet having heat insulating properties, comprising inorganic powder and organic fiber, having a thermal conductivity of 0.10 W / m K to 0.18 W / m K, an average thickness of 0.06 mm to 0.30 mm, and when one side of the inorganic powder sheet is used as a heating surface and heated to approximately 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 400°C to 500°C.

2. The inorganic powder sheet according to claim 1, having a basis weight of 100 g / m 2 ~400g / m 2 An inorganic powder sheet.

3. An inorganic powder sheet according to claim 1, wherein the content of the inorganic powder is 55% by weight or more.

4. The inorganic powder sheet according to claim 1, wherein the volume resistivity is 1.0 x 10 12 Ω・cm~8.0×10 13 Inorganic powder sheet with a resistance of Ω·cm.

5. The inorganic powder sheet according to claim 1, wherein the burst strength is 100 kPa to 185 kPa.

6. An inorganic powder sheet according to claim 1, wherein the inorganic powder is at least one of silica, alumina, mica, titanium oxide, sepiolite, zeolite, kaolin, bentonite, talc, and vermiculite.

7. An inorganic powder sheet according to any one of claims 1 to 6, wherein the organic fibers comprise one or more of para-aramid fibers, para-aramid pulp, meta-aramid pulp, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, flame-retardant rayon fibers, and natural fibers.

8. An inorganic powder sheet according to any one of claims 1 to 6, wherein the inorganic powder sheet is a wet-laid paper sheet.

9. The inorganic powder sheet according to any one of claims 1 to 6, having a basis weight of 135 g / m 2 ~200g / m 2 an inorganic powder sheet having a thickness of 0.10 mm to 0.18 mm, a thermal conductivity of 0.10 W / m·K to 0.18 W / m·K, and when heated to approximately 1000°C using one side as a heating surface, a temperature difference between the heating surface and the back side of the heating surface is 415°C to 500°C.

10. The inorganic powder sheet according to claim 9, wherein the volume resistivity is 1.0 x 10 12 Ω cm to 8.0 x 10 13 Inorganic powder sheet with a resistance of Ω·cm.

11. The inorganic powder sheet according to any one of claims 1 to 6, having a basis weight of 135 g / m 2 ~200g / m 2 a thickness of 0.11 mm to 0.18 mm; a thermal conductivity of 0.10 W / m K to 0.18 W / m K; when one side is used as a heating surface and heated to approximately 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 415°C to 460°C; and a volume resistivity of 1.0 x 10 12 Ω・cm~8.0×10 13 An inorganic powder sheet having a compressive strength of Ω·cm and a burst strength of 100 kPa to 185 kPa.

12. A method for producing an inorganic powder sheet having heat insulating properties, comprising the steps of: blending organic fibers with inorganic powder, dispersing the mixture in water to form a slurry, and wet-laid papermaking the slurry to obtain a sheet material; and heat-calendering the sheet material to reduce the average thickness to 0.06 mm to 0.30 mm.

13. A method for producing an inorganic powder sheet according to claim 12, wherein the inorganic powder sheet has a thermal conductivity of 0.10 W / m·K to 0.18 W / m·K, and when one side of the inorganic powder sheet is used as a heating surface and heated to approximately 1000°C, the temperature difference between the heating surface and the back side of the heating surface is 400°C to 500°C.

14. A method for producing an inorganic powder sheet according to claim 12 or 13, wherein the inorganic powder is at least one of silica, alumina, mica, titanium oxide, sepiolite, zeolite, kaolin, bentonite, talc, and vermiculite.

15. A method for producing an inorganic powder sheet according to claim 12 or 13, wherein the organic fibers comprise one or more of para-aramid fibers, para-aramid pulp, meta-aramid pulp, polyphenylene sulfide fibers, PET fibers, flame-retardant PET fibers, flame-retardant rayon fibers, and natural fibers.

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