Battery pack cover, battery pack unit, and electric mobility

Abstract

To provide a battery pack cover (3) having excellent flame-resistant properties, a battery pack unit (1) using this battery pack cover, and electric mobility using this battery pack unit.SOLUTION: A battery pack cover for use in a battery pack includes a cover base material (5) and an inorganic fiber molded body (4) having tensile strength of 20 N or more. There are also provided a battery pack unit using this battery pack cover, and electric mobility using this battery pack unit.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a battery pack cover, a battery pack unit, and electric mobility.

Background Art

[0002] A battery pack unit used in electric mobility such as an electric vehicle includes a housing having a partially open portion, a battery pack disposed within the housing, and a battery pack cover that closes the open portion (Patent Document 1: WO2012 / 167921). Paragraph 0081 of Patent Document 1 exemplifies aluminum, aluminum alloy, magnesium, magnesium alloy, AlSiC, titanium, titanium alloy, steel, stainless steel, and special steel as constituent materials of the battery pack cover.

[0003] In a battery module used in mobility such as an electric vehicle, a heat insulating material or a heat absorbing material may be provided between battery cells in order to countermeasures against thermal runaway of the battery.

[0004] Patent Document 2 (EP2506336A1) discloses a battery pack thermal management system as a thermal management system for minimizing the influence of thermal runaway, which includes a plurality of batteries and an airtight battery pack packaging. The battery pack packaging has a cavity and a gas discharge port on its outer wall, and is configured such that when at least one battery falls into thermal runaway, the gas discharge port allows gas to pass to the outside of the battery pack packaging.

[0005] Also known is a battery unit in which a mica sheet or the like is attached to the side surface of a battery pack cover covering a battery module in order to improve the fire resistance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] In order to increase the driving distance, the energy density of the battery module mounted on an electric vehicle tends to increase, and the requirements for the heat generation of the battery and the risk of thermal runaway are increasing. In the case of a heat insulating material or the like provided between battery cells, if ignition that cannot be suppressed occurs, in order to delay the spread of fire to the interior member, an object of the present invention is to provide a battery pack cover having excellent flame shielding properties. Furthermore, it is an object of the present invention to provide a battery pack unit using this battery pack cover and an electric mobility using this battery pack unit.

Means for Solving the Problems

[0008] Since a mica sheet is a hard and brittle mineral, it is easily damaged by vibrations during driving. In addition, when satisfying functions such as flame shielding properties, the vehicle body weight increases. On the other hand, if it is a lightweight flame shielding structure, it is easily blown away by the blast, and the flame shielding property for retaining the flame ejected from the battery pack is insufficient. Therefore, the present inventors focused on the fact that an inorganic fiber molded body having a tensile strength within a specific range can withstand the blast ejected during thermal runaway of the battery and prevent the penetration of the flame, and found that the flame shielding property of the battery pack cover can be improved without impairing the loadability. The gist of the present invention is as follows.

[0009] [1] A battery pack cover used for a battery pack, characterized by having a cover base material and an inorganic fiber molded body having a tensile strength of 20 N or more in the following tensile test.

[0010] <Tensile Test> A test piece with a width of 25 mm and a length of 160 mm is punched out from the inorganic fiber formed body, and the test piece is pulled in the longitudinal direction at a speed of 25 mm / min using a tensile testing machine. The maximum value of the measured load is defined as the tensile strength.

[0011] [2] The battery pack cover according to [1], wherein the cover base material is a metal base material.

[0012] [3] The battery pack cover according to [1] or [2], which is a laminate in which the cover base material and the inorganic fiber formed body are overlapped.

[0013] [4] The battery pack cover according to any one of [1] to [3], which does not penetrate by a flame test at a flame temperature of 1000 °C for 5 minutes.

[0014] [5] The battery pack cover according to any one of [1] to [4], wherein the inorganic fiber formed body is composed of inorganic fibers having an average fiber length of 3 mm or more.

[0015] [6] The battery pack cover according to any one of [1] to [5], wherein the inorganic fiber formed body is a woven fabric or a non-woven fabric.

[0016] [7] The battery pack cover according to any one of [1] to [6], wherein the inorganic fiber formed body is a needle punched blanket.

[0017] [8] A battery pack unit having the battery pack cover according to any one of [1] to [7] and a battery pack.

[0018] [9] The battery pack unit according to [8], The battery pack unit in which the inorganic fiber formed body of the battery pack cover is arranged on the battery pack side.

[0019]

[10] An electric mobility equipped with the battery pack unit according to [8] or [9]. [Effects of the Invention]

[0020] The inorganic fiber molded body used in the present invention has a tensile strength of 20 N or more and is excellent in the property of preventing a flame from penetrating during thermal runaway of a battery. Therefore, a battery cover provided with this inorganic fiber molded body is excellent in flame shielding properties.

Brief Description of the Drawings

[0021]

Figure 1

Embodiments for Carrying Out the Invention

[0022] The battery pack cover of the present invention is used for a battery pack unit. The battery pack unit has a battery pack and a battery cover.

[0023] FIG. 1 is a schematic cross-sectional view showing an example of a battery pack unit. This battery pack unit 1 further has a housing 2 with a partially open portion 2a, a battery pack cover 3 that closes the open portion 2a, and a battery pack 10 and the like disposed inside the housing 2. However, the housing is not necessarily required.

[0024] The battery pack cover 3 has an inorganic fiber molded body 4 and a cover base material 5. Both the inorganic fiber molded body 4 and the cover base material 5 are plate-shaped and are overlapped. However, they may be adhered to each other with an adhesive. The inorganic fiber molded body 4 is disposed inside the battery pack unit 1 rather than the cover base material 5.

[0025] The battery pack 10 disposed inside the housing 2 includes a plurality of battery modules 11.

[0026] This battery pack unit 1 can improve the heat shielding property of the battery pack cover without impairing the loadability, and thus is preferably used for the batteries of electric mobility such as electric vehicles, electric motorcycles, and ships. The battery is not particularly limited, and examples thereof include secondary batteries such as lithium-ion batteries, nickel-hydrogen batteries, lithium-sulfur batteries, nickel-cadmium batteries, nickel-iron batteries, nickel-zinc batteries, sodium-sulfur batteries, lead storage batteries, and air batteries. Among these, a lithium-ion battery is preferable, and in particular, it is preferably used for suppressing thermal runaway of a lithium-ion battery.

[0027] [Cover base material] The cover base material 5 of the battery pack cover 3 is not particularly limited, and housing materials such as a metal base material and a reinforced resin base material can be used. From the viewpoint of heat shielding property, a metal base material is preferable, and aluminum, aluminum alloy, magnesium, magnesium alloy, titanium, titanium alloy, iron, stainless steel, etc. are preferable. The thickness of the metal base material 5 is preferably 0.1 to 10 mm, particularly preferably about 0.3 to 7 mm, but is not limited thereto.

[0028] [Inorganic fiber molded body] The inorganic fiber molded body used in the present invention has a tensile strength of 20 N or more, preferably 25 N or more, and particularly preferably 30 N or more. The higher the tensile strength of the inorganic fiber molded body, the more preferable it is, and there is no upper limit, but it is preferably 100 kN or less, particularly preferably 50 kN or less. The tensile strength is a value measured by the method described in the examples below.

[0029] The inorganic fiber constituting this inorganic fiber molded body is not particularly limited, and examples thereof include silica, alumina / silica, zirconia, spinel, titania, etc. containing these, alone or composite fibers. The inorganic fiber is preferably an alumina / silica-based fiber, and particularly preferably a crystalline alumina / silica-based fiber. The composition ratio (weight ratio) of alumina / silica of the alumina / silica-based fiber is preferably in the range of 60 to 95 / 40 to 5, more preferably in the range of 70 to 84 / 30 to 16, and particularly preferably in the range of 70 to 76 / 30 to 24.

[0030] In addition, the inorganic fiber is preferably a fiber having an average fiber length of 1 mm or more, more preferably 2 mm or more, and still more preferably 3 mm or more. Further, the average fiber length is preferably 3.0×10 3 mm or less, more preferably 1.0×10 3 mm. The average fiber diameter of the inorganic fiber is preferably 3 to 10 μm, particularly preferably 5 to 8 μm. When the average fiber length and average fiber diameter of the inorganic fiber are within this range, it is preferable because the inorganic fiber molded body has high tensile strength. Further, when the average fiber length and average fiber diameter of the inorganic fiber are within this range, it is preferable because the amount of dust floating in the air can be suppressed. The average fiber length of the inorganic fiber is the average value of 300 fibers measured by microscopic observation. The average fiber diameter is the average value of 100 fibers measured by microscopic observation.

[0031] The production method and shape of the inorganic fiber molded body used in the present invention are not limited as long as it has a desired tensile strength. For example, it is preferably composed of inorganic fibers and is a woven fabric or a non-woven fabric. When the inorganic fiber molded body is a woven fabric composed of inorganic fibers, the production method thereof is not limited, and a method of weaving a known woven fabric can be applied. Further, even when the inorganic fiber molded body is a non-woven fabric composed of inorganic fibers, the production method thereof is not limited, but it is preferably a needle blanket subjected to needling treatment. By performing the needling treatment, needle marks are formed on the inorganic fiber molded body. The inorganic fiber molded body is in a mat shape having a predetermined thickness. The plane perpendicular to the thickness direction of the inorganic fiber molded body may be hereinafter referred to as a mat surface. Further, the side surface (surface in the thickness direction) perpendicular to the mat surface of the inorganic fiber molded body may be referred to as an end surface.

[0032] In one aspect of the present invention, the inorganic fiber molded body has needle marks. The needle mark density means the number of needle marks per unit area (1 cm 2 ) of the mat surface of the inorganic fiber molded body after firing.

[0033] When visible light is applied to the mat surface of the inorganic fiber formed body, the amount of transmitted light at the needle marks is larger than that in the regions other than the needle marks, so that the transmitted light is observed as light spots on the peeling surface. By counting the number of light spots due to the transmission to this peeling surface, the number of needle marks is determined.

[0034] In the present invention, the number of needle marks (needle mark density) per unit area (1 cm 2 ) of the mat surface of the inorganic fiber formed body is, as an average value of the entire mat surface, preferably 1 piece / cm 2 or more, more preferably 3 pieces / cm 2 or more, and preferably 100 pieces / cm 2 or less, more preferably 50 pieces / cm 2 or less.

[0035] The basis weight (mass per unit area) of the inorganic fiber formed body is 50 g / m 2 or more, preferably 80 g / m 2 or more, more preferably 100 g / m 2 or more, still more preferably 200 g / m 2 or more, particularly preferably 400 g / m 2 or more. Also, the basis weight of the inorganic fiber formed body is preferably 3000 g / m 2 or less, more preferably 2500 g / m 2 or less, particularly preferably 2000 g / m 2 or less.

[0036] The thickness of the inorganic fiber formed body is preferably 0.1 mm or more, more preferably 0.3 mm or more, particularly 0.5 mm or more. Also, the thickness of the inorganic fiber formed body is preferably 25 mm or less, more preferably 20 mm or less, particularly preferably 15 mm or less. When the basis weight and thickness of the inorganic fiber formed body are within this range, the tensile strength of the inorganic fiber formed body becomes an appropriate range, which is preferable. Also, it is preferable from the viewpoints of loadability and space efficiency in mobility.

[0037] The basis weight and thickness of the inorganic fiber formed body can be within the above ranges by adjusting the fiber amount per unit area when laminating the inorganic fiber aggregate constituting the inorganic fiber formed body with a folding device.

[0038] [Method for manufacturing inorganic fiber formed body] The inorganic fiber formed body can be manufactured by a method including a step of obtaining a mat-like aggregate of an inorganic fiber precursor by a sol-gel method, a step of subjecting the obtained mat-like aggregate of the inorganic fiber precursor to needling treatment, and a firing step of firing the needled mat-like aggregate of the inorganic fiber precursor to obtain an inorganic fiber formed body. However, the inorganic fiber formed body may be manufactured by other methods.

[0039] Hereinafter, an example of the method for manufacturing this inorganic fiber formed body will be illustrated and described by taking the method for manufacturing an alumina / silica-based fiber formed body as an example. However, the inorganic fiber formed body of the present invention is not limited to the alumina / silica-based fiber formed body at all. As described above, it may be a formed body made of silica, zirconia, spinel, titania, or composite fibers thereof.

[0040] <Spinning step> To manufacture a mat-like aggregate of alumina / silica-based fibers by the sol-gel method, first, a spinning solution containing basic aluminum chloride, a silicon compound, an organic polymer as a thickener, and water is spun by a blowing method to obtain an aggregate of alumina / silica fiber precursors.

[0041] ≪Preparation of spinning solution≫ Basic aluminum chloride; Al(OH) 3-x Cl xIt can be prepared, for example, by dissolving metallic aluminum in an aqueous solution of hydrochloric acid or aluminum chloride. The value of x in the above chemical formula is usually from 0.45 to 0.54, preferably from 0.5 to 0.53. As the silicon compound, silica sol is preferably used, but other water-soluble silicon compounds such as tetraethyl silicate and water-soluble siloxane derivatives can also be used. As the organic polymer, for example, water-soluble polymer compounds such as polyvinyl alcohol, polyethylene glycol, and polyacrylamide are preferably used. The degree of polymerization of these is usually from 1000 to 3000.

[0042] The spinning solution preferably has a ratio of aluminum derived from basic aluminum chloride to silicon derived from the silicon compound, in terms of the weight ratio of Al2O3 to SiO2, usually from 99:1 to 65:35, preferably from 99:1 to 70:30, an aluminum concentration of 170 to 210 g / L, and an organic polymer concentration of 20 to 50 g / L.

[0043] When the amount of the silicon compound in the spinning solution is less than the above range, the alumina constituting the short fibers is likely to be α-aluminized, and moreover, embrittlement of the short fibers due to coarsening of the alumina particles is likely to occur. On the other hand, when the amount of the silicon compound in the spinning solution is more than the above range, the amount of silica (SiO2) produced together with mullite (3Al2O3·2SiO2) increases and the heat resistance is likely to decrease.

[0044] When the concentration of aluminum in the spinning solution is less than 170 g / L or the concentration of the organic polymer is less than 20 g / L, in either case, an appropriate viscosity of the spinning solution cannot be obtained, and the fiber diameter of the resulting alumina / silica-based fiber becomes small. That is, as a result of too much free water in the spinning solution, the drying rate during spinning by the blowing method is slow, stretching proceeds excessively, the fiber diameter of the spun precursor fiber changes, and short fibers with a predetermined average fiber diameter and a sharp fiber diameter distribution cannot be obtained. Moreover, when the concentration of aluminum is less than 170 g / L, productivity decreases. On the other hand, when the concentration of aluminum exceeds 210 g / L or the concentration of the organic polymer exceeds 50 g / L, in either case, the viscosity is too high to form a spinning solution. The preferred concentration of aluminum in the spinning solution is 180 - 200 g / L, and the preferred concentration of the organic polymer is 30 - 40 g / L.

[0045] The above-mentioned spinning solution is prepared by adding a silicon compound and an organic polymer in an amount that gives the above Al2O3:SiO2 ratio to an aqueous solution of basic aluminum chloride, and concentrating so that the concentrations of aluminum and the organic polymer are in the above ranges.

[0046] ≪Blowing≫ Spinning (fiberization of the spinning solution) is usually carried out by the blowing method of supplying the spinning solution into a high-speed spinning air stream, whereby an alumina short fiber precursor is obtained. The structure of the spinning nozzle used during the above spinning is not particularly limited. For example, as described in Japanese Patent No. 2602460, the air stream blown out from the air nozzle and the spinning solution stream extruded from the spinning solution supply nozzle are parallel flows, and moreover, a structure in which the parallel flow of air is sufficiently rectified and contacts the spinning solution is preferred.

[0047] Also, during spinning, first, under conditions where evaporation of moisture and decomposition of the spinning solution are suppressed, fibers sufficiently stretched from the spinning solution are formed, and then it is preferable that these fibers are dried promptly. For this purpose, it is preferable to change the atmosphere from a state where evaporation of moisture is suppressed to a state where evaporation of moisture is promoted in the process from when the fibers are formed from the spinning solution until they reach the fiber collector.

[0048] An alumina / silica fiber precursor is collected and accumulated by an integrating device structured to install an endless belt made of wire mesh so as to be substantially perpendicular to the spinning air current, and to collide the spinning air current containing the alumina / silica fiber precursor against the endless belt while rotating the endless belt, and can be recovered as a continuous sheet-like integrated body (thin layer sheet) of the alumina / silica fiber precursor.

[0049] The basis weight of this thin layer sheet is preferably 10 to 200 g / m 2 and particularly preferably 30 to 100 g / m 2 although it is not limited thereto.

[0050] The thin layer sheet recovered from the above integrating device can be further laminated. Specifically, for example, an integrated body (thin layer sheet) of an inorganic fiber precursor is continuously drawn out and sent to a folding device, folded to a predetermined width and stacked while continuously moving in a direction perpendicular to the folding direction, thereby forming a laminated integrated body (laminated sheet) of the inorganic fiber precursor. By laminating the thin layer sheets in this way, the basis weight (areal weight) of the laminated sheet becomes uniform over the entire sheet. As the above folding device, those described in JP-A-2000-80547 can be used.

[0051] <Needling aid or anti-friction agent application step> A needling aid or an anti-friction agent is applied to the sheet surface of the thin layer sheet or the laminated sheet of the alumina / silica-based inorganic fiber precursor obtained by spinning as needed. The needling aid or the anti-friction agent is preferably applied to both sheet surfaces.

[0052] The needling aid is not particularly limited as long as it has the effect of strengthening the yarns near the mat surface of the inorganic fiber precursor aggregate, and various coating agents such as acrylic polymer coating agents can be used.

[0053] As the antifriction agent, a surfactant or an emulsion having an action of reducing the friction between the needle and the fiber can be used. The needling aid and the antifriction agent are attached by applying a solution or a dispersion (wet coating) or the like.

[0054] <Needling treatment step> After attaching a needling aid and / or an antifriction agent to the laminated sheet of the alumina / silica-based inorganic fiber precursor obtained by spinning, if necessary, a needling treatment is performed in which a needle having barbs is pierced into the laminated sheet. The needling treatment may be performed from only one surface of the laminated sheet or from both surfaces. Preferably, it is performed from both surfaces.

[0055] The needle is preferably pierced in a direction perpendicular to the sheet surface of the laminated sheet. The needle is pierced deeper than the center in the thickness direction of the laminated sheet. The needle may be pierced so as to penetrate the laminated sheet in the thickness direction.

[0056] In this way, by performing the needling treatment, needle marks are formed on the inorganic fiber molded body. That is, when a needling treatment of piercing a needle with barbs into the laminated sheet is performed, at least a part of the fibers are extended in a substantially thickness direction by the needle at the location where the needle is pierced. As a result, needle marks are formed on the surface of the inorganic fiber molded body. Inside the needling-treated inorganic fiber molded body, the yarns of the inorganic fibers extending in a substantially thickness direction are referred to as longitudinal yarns.

[0057] The needling treatment is performed to adjust the bulk density and the peel strength of the inorganic fiber molded body by forming longitudinal yarns.

[0058] The needle marks may penetrate the inorganic fiber molded body or may extend from one mat surface and penetrate without reaching the other mat surface.

[0059] <Firing step> The inorganic fiber formed body is preferably a fired body obtained by firing a needled inorganic fiber precursor. The firing is usually carried out at a temperature of 900 °C or higher, preferably 1000 to 1300 °C. If the firing temperature is 900 °C or higher, crystallization proceeds sufficiently and alumina / silica-based fibers excellent in strength can be obtained, which is preferable. Further, if the firing temperature is 1300 °C or lower, the grain growth of the crystals of the fibers does not proceed too much, and alumina / silica-based fibers having appropriate strength can be obtained, which is preferable.

[0060] [Example 1] <Manufacture of Inorganic Fiber Formed Body> Silica sol was added to an aqueous solution of basic aluminum chloride (aluminum content 165 g / L, Al / Cl = 1.8 (atomic ratio)) so that the composition of the finally obtained alumina fiber was Al2O3:SiO2 = 72:28 (weight ratio). Further, after adding polyvinyl alcohol, it was concentrated to prepare a spinning solution having a viscosity of 70 poise (25 °C) and an alumina·silica content of about 35% by weight.

[0061] The above spinning solution was spun by the blowing method. As the spinning nozzle, a spinning nozzle having the same structure as that described in FIG. 6 of Japanese Patent No. 2602460 was used. Further, at the time of collecting the fibers, an endless belt made of wire mesh was installed so as to be substantially perpendicular to the spinning air flow, and while rotating the endless belt, the spinning air flow containing the alumina / silica-based fiber precursor was collided with the endless belt, and the fibers were collected as a continuous sheet (thin layer sheet) by an integrating device having such a structure.

[0062] The thin layer sheet recovered from the integrating device was continuously drawn out after being coated with an antifriction agent by spraying, sent to a folding device, folded into a predetermined width and stacked, and continuously moved in a direction perpendicular to the folding direction to form a laminated sheet. As the above folding device, a folding device having the same structure as that described in JP-A-2000-80547 was used. The needling treatment was carried out by punching with a needle punching machine.

[0063] Thereafter, it was fired at 1200 °C, and the basis weight was 900 g / m 2(Thickness: 5.6 mm, bulk density: 0.16 g / cm 3 ) An inorganic fiber molded body 1 made of crystalline alumina / silica-based fibers was obtained. The firing was carried out in an electric furnace by heating up to 1200 °C at a rate of 5 °C / min, holding at 1200 °C for 30 minutes, and then cooling naturally.

[0064] The composition ratio of the crystalline alumina / silica-based fibers was alumina / silica = 72 / 28 (weight ratio). The average fiber diameter (average value of 100 fibers) of the crystalline alumina / silica-based fibers measured by microscopic observation of the inorganic fiber molded body was 5.5 μm.

[0065] [Manufacture of Battery Pack Cover] The obtained inorganic fiber molded body and an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) as a cover base material were overlapped to form a laminate, and the battery pack cover 1 of Example 1 was manufactured.

[0066] [Example 2] In Example 1, an inorganic fiber molded body with a reduced fiber amount per unit area, having a basis weight of 600 g / m 2 (Thickness: 4.8 mm, bulk density: 0.12 g / cm 3 ) was used. An inorganic fiber molded body 2 was manufactured in the same manner as in Example 1, and it was overlapped with an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) to form a laminate, and the battery pack cover 2 of Example 2 was manufactured. The composition ratio of the crystalline alumina / silica-based fibers was alumina / silica = 72 / 28 (weight ratio). The average fiber diameter (average value of 100 fibers) of the crystalline alumina / silica-based fibers measured by microscopic observation of the inorganic fiber molded body was 5.5 μm.

[0067] [Example 3] In Example 1, the bulk density was reduced by reducing the needle mark density, and a basis weight of 900 g / m 2 (Thickness: 6.3 mm, bulk density: 0.14 g / cm 3An inorganic fiber molded body 3 was produced in the same manner as in Example 1 except for the above, and it was stacked with an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) to form a laminate, and the battery pack cover 3 of Example 3 was produced. The composition ratio of this crystalline alumina / silica-based fiber was alumina / silica = 72 / 28 (weight ratio), and the average fiber diameter (average value of 100 fibers) of the crystalline alumina / silica-based fiber measured by microscopic observation of the inorganic fiber molded body was 5.5 μm.

[0068] [Example 4] As the inorganic fiber molded body 4, Denka Co., Ltd.'s Arsen NBK80-10 was used.

[0069] The composition ratio of this crystalline alumina / silica-based fiber was alumina / silica = 80 / 20 (weight ratio), and the average fiber diameter (average value of 100 fibers) of the crystalline alumina / silica-based fiber measured by microscopic observation of the inorganic fiber molded body was 4.4 μm. The inorganic fiber molded body 4 and an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) were stacked to form a laminate, and the battery pack cover 4 of Example 4 was produced.

[0070] [Example 5] As the inorganic fiber molded body 5, ITM Co., Ltd. (currently Isolite Industry Co., Ltd.)'s FMX16 blanket LXS150 was used. The composition ratio of this crystalline alumina / silica-based fiber was alumina / silica = 72 / 28 (weight ratio), and the average fiber diameter (average value of 100 fibers) of the crystalline alumina / silica-based fiber measured by microscopic observation of the inorganic fiber molded body was 4.1 μm. The inorganic fiber molded body 5 and an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) were stacked to form a laminate, and the battery pack cover 5 of Example 5 was produced.

[0071] [Example 6] In Example 1, as an inorganic fiber molded body with a reduced fiber amount per unit area, a basis weight of 432 g / m 2 (thickness 3.5 mm, bulk density 0.12 g / cm 3An inorganic fiber molded body 6 was produced in the same manner as in Example 1 except for the above, and laminated with an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) to form a laminate, and the battery pack cover 6 of Example 6 was produced. The composition ratio of this crystalline alumina / silica-based fiber was alumina / silica = 72 / 28 (weight ratio), and the average fiber diameter (average value of 100 fibers) of the crystalline alumina / silica-based fiber measured by microscopic observation of the inorganic fiber molded body was 5.6 μm.

[0072] [Comparative Example 1] The inorganic fiber molded body 1 obtained in Example 1 was crushed using a dry defibrator and short-fibered, and water was added to 92.4% by weight of the inorganic fiber to obtain a dispersion. To this dispersion, 6.0% by weight of a modified acrylate copolymer (latex), 0.5% by weight of an anionic acrylic resin (paper strength enhancer), 1.0% by weight of aluminum sulfate, and 0.1% by weight of a polymer flocculant were added, and the mixture was aggregated and stirred to adjust the slurry. The slurry was adjusted using a paper-making machine so that the basis weight after drying was 700 g / m 2 (thickness 5.3 mm, bulk density 0.13 g / cm 3 ) and the suction speed and the supply speed of the slurry were adjusted to obtain an inorganic fiber molded body. Then, the inorganic fiber molded body and an aluminum alloy plate (Al alloy plate A5052, thickness 0.8 mm) were overlapped to form a laminate, and the battery pack cover of Comparative Example 1 was produced.

[0073] ≪Measurement of Physical Properties of Inorganic Fiber Molded Body≫ For the inorganic fiber molded bodies obtained in the above Examples and Comparative Examples, the tensile strength, fiber length, thickness, and needle mark density were measured as follows. The results are shown in Table 1.

[0074] ·Tensile Strength Measurement Test Method It was measured using a tensile testing machine. The size of the parallel part (effective part) of the test piece was 25 mm × 100 mm, and the overall size was 25 mm × 160 mm. The inorganic fiber molded body in the product state was cut out to the above size using a punching die, attached to the tensile testing machine, pulled at a speed of 25 mm / min, and the maximum value of the load was defined as the tensile strength.

[0075] ·Method for measuring average fiber length Measurement was carried out using an optical microscope. 2 g of a sample was collected from the inorganic fiber formed body with tweezers and put into a 1000 ml beaker together with 800 ml of water. Ultrasonic dispersion was performed using a device manufactured by Tokyo Rika Kikai Co., Ltd. (Model: USC-200Z38S-23). Then, a sample solution was prepared by taking 20 - 25 ml of the dispersed liquid and putting it into a 200 ml beaker containing 150 ml of water. The sample solution was vigorously stirred with a stirrer, 1 - 2 ml was collected and dropped onto a slide glass, a cover glass was placed on it, and observation was carried out with an optical microscope. The length of the fibers projected onto the monitor for the microscope was read at 1 mm intervals. The number of samples was 300, and the fiber length for each was calculated using the following conversion formula.

[0076] Conversion formula: Fiber length (μm) = Measured value (mm) ÷ Magnification × 1000 ·Method for measuring thickness Measurement was carried out using a digital dial gauge. The measurement load was 4.9 kPa (50 g / cm 2 ), and the minimum memory for measurement was 0.01 mm. Test pieces cut out by the method described in the flame test method to be described later were randomly measured for thickness at 5 points using the said measurement jig, and the average value of the 5 points was taken as the representative value of the measurement.

[0077] ·Method for measuring needle mark density The number of needle marks per unit area was taken as the average value of the number of needle marks on one peeled surface peeled off from the center of the thickness of the inorganic fiber formed body cut out per unit area and the number of needle marks on the other peeled surface. Note that the portions where the warp threads exist were counted as needle marks.

[0078] Actually, when visible light is applied to one surface of the inorganic fiber formed body, transmitted light is observed on the peeled surface. By counting the number of light spots due to transmission to this peeled surface and the number of warp threads, the number of all needle marks per unit area can be counted.

[0079] As a result of measuring the needle mark density of Example 1 and Example 2 by the above method, they were 27.3 pieces / cm 2 and 19.3 pieces / cm 2 respectively.

[0080] ≪Flame Test Method≫ The inorganic fiber molded bodies 1 to 8 of Examples 1 to 7 and Comparative Example 1 were cut out into a size of 3600 mm 2 using a punching die. The cut-out inorganic fiber molded bodies were used as test pieces by overlapping them with each aluminum alloy plate (3600 mm 2 , thickness 0.8 mm), and the following flame test was conducted.

[0081] The test piece was sandwiched and fixed with a stainless steel jig, and the test piece was placed at a position 70 mm away from the tip of the torch burner. The test piece was arranged with the inorganic fiber molded body side facing the burner and the mat surface of the inorganic fiber molded body substantially perpendicular to the burner axis direction.

[0082] To this torch burner (Sakaguchi Seisakusho: WT-01, nozzle diameter 1.2 mm), O2 0.5 MPa, C2H2 0.02 MPa, and air pressure of 0.2 MPa from the air nozzle (discharge port diameter 3.0 mm, arranged at a position 100 mm away from the test piece so that the mat surface of the inorganic fiber molded body is substantially perpendicular to the air nozzle axis direction) were supplied for 5 minutes, and a flame with a temperature of 1000 °C was sprayed toward the test piece.

[0083] At the time when 5 minutes had elapsed since the start of irradiating the flame toward the inorganic fiber molded body of the test piece, the test piece was removed, and it was visually confirmed whether or not the inorganic fiber molded body had been penetrated by the flame. The results are shown in Table 1.

[0084]

Table 1

[0085] <Discussion> As shown in Table 1, the battery pack cover of the present invention has excellent flame shielding properties as the flame does not penetrate the inorganic fiber molded body.

[0086] Although the present invention has been described in detail using specific embodiments, it will be apparent to those skilled in the art that various changes can be made without departing from the spirit and scope of the present invention.

[0087] This application is based on Japanese Patent Application No. 2020-206897 filed on December 14, 2020, the entire disclosure of which is incorporated herein by reference.

Explanation of Reference Numerals

[0088] 1 Battery Pack Unit 2 Housing 3 Battery Pack Cover 4 Inorganic Fiber Formed Body 5 Cover Base Material 10 Battery Pack 11 Battery Module

Claims

1. A battery pack cover for use in a battery pack, comprising: A battery pack cover comprising a cover substrate and an inorganic fiber molded body having a tensile strength of 20 N or more in the following tensile test. <Tensile Test> A test piece measuring 25 mm wide x 160 mm long was cut out from the inorganic fiber molded product, and pulled in the longitudinal direction at a speed of 25 mm / min using a tensile tester. The maximum load measured was taken as the tensile strength.

2. The battery pack cover according to claim 1 , wherein the cover substrate is a metal substrate.

3. 3. The battery pack cover according to claim 1, wherein the cover base material and the inorganic fiber molded body are laminated together.

4. 4. The battery pack cover according to claim 1, which is not penetrated by a flame test at a flame temperature of 1000° C. for 5 minutes.

5. 5. The battery pack cover according to claim 1, wherein the inorganic fiber molding is made of inorganic fibers having an average fiber length of 3 mm or more.

6. 6. The battery pack cover according to claim 1, wherein the inorganic fiber molded body is a woven fabric or a nonwoven fabric.

7. The battery pack cover according to claim 1 , wherein the inorganic fiber molding is a needle blanket.

8. A battery pack unit comprising the battery pack cover according to any one of claims 1 to 7 and a battery pack.

9. 9. The battery pack unit according to claim 8, A battery pack unit in which the inorganic fiber molding of the battery pack cover is disposed on the battery pack side.

10. An electric mobility device comprising the battery pack unit according to claim 8 or 9.

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