Battery pack

Abstract

To provide a battery pack having excellent fire extinguishing performance against a fire occurring from a secondary battery.SOLUTION: A battery pack includes a housing, a secondary battery housed within the housing, and a fire extinguishing film disposed within the housing, the housing including an opening communicating the inside of the housing with the outside of the housing, and a value calculated by the following formula (1) being 15 or more. (C1-V1) / A1 (1). [In the formula, C1 represents the volume of the housing (unit: mm3), V1 represents the volume of the secondary battery (unit: mm3), and A1 represents the area of the opening (unit: mm2).]SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a battery pack.

Background Art

[0002] In recent years, with the progress of technology, our lives have become increasingly comfortable. On the other hand, a large amount of energy is required to create this comfort. High safety is required for energy handling in various scenarios such as filling, storing, transporting, and using large amounts of energy in a high density.

[0003] Taking automobiles as an example, when extracting fossil fuels, purifying gasoline from fossil fuels, transporting gasoline, or burning gasoline in an engine, there are potential risks of ignition and fire.

[0004] Taking electronics as an example, when moving electrical energy through wires, adjusting electrical energy at substations or transformers, using electrical energy in household or industrial electrical equipment, or temporarily storing it in a battery, there are similarly potential risks of ignition and fire.

[0005] It is known that a lithium-ion battery, which is a typical secondary battery, may short-circuit and cause a fire due to overcharging or a strong external impact. When a lithium-ion battery short-circuits or experiences thermal runaway, it releases a large amount of flammable gas, which can lead to a serious fire. Therefore, in recent years, there have been examples of installing functional materials in modules equipped with secondary batteries for the purpose of fire suppression.

[0006] For example, Patent Document 1 discloses a power storage module including a flame-retardant heat-insulating sheet. Patent Document 2 discloses a battery module characterized by arranging a fire-extinguishing sheet at a specific position.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2019-147357 [Patent Document 2] Japanese Unexamined Patent Application Publication No. 2022-145344 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] However, although the power storage module of Patent Document 1 can suppress smoldering, it cannot extinguish the flame generated from the battery cell, and cannot suppress the spread of a fire caused by ignition by high-temperature gas.

[0009] In addition, in the battery module of Patent Document 2, when a single battery catches fire, a large amount of high-temperature combustible gas is released from the inside. Therefore, the discharged fire extinguishing agent is pushed out of the battery module in an extremely short time. As a result, there is a possibility that the fire extinguishing is insufficient.

[0010] The present disclosure has been made in view of the above circumstances, and provides a battery pack having excellent fire extinguishing performance for a fire generated from a secondary battery. [Means for Solving the Problems]

[0011] In order to solve the above problems, the present disclosure provides the following battery pack. [1] A housing, A secondary battery housed in the housing, A fire extinguishing film disposed in the housing, and the housing has an opening communicating the inside and the outside of the housing, A battery pack in which the value calculated by the following formula (1) is 15 or more. (C1-V1) / A1 ··· (1) [In the formula, C1 represents the volume of the housing (unit: mm 3 ), V1 represents the volume of the secondary battery (unit: mm 3 ), and A1 represents the area of the opening (unit: mm 2 ).] The battery pack according to [1], wherein the value calculated by formula (1) is 100 or more. The battery pack according to [1] or [2], wherein the housing has only one opening. [4] The fire extinguishing film has a laminated structure including a base material and a fire extinguishing agent layer, The battery pack according to any one of [1] to [3], wherein the fire extinguishing agent layer contains a fire extinguishing chemical and a binder resin. [5] The battery pack according to [4], wherein the fire extinguishing chemical contains potassium citrate and potassium chlorate. [6] The battery pack according to any one of [1] to [5], wherein the opening is formed at a position satisfying the condition represented by the following inequality (a). L1>L2 ··· (a) [In the formula, L1 represents the shortest distance from the opening to the positive electrode of the secondary battery, and L2 represents the shortest distance from the opening to the negative electrode of the secondary battery.] [7] The battery pack according to any one of [1] to [6], wherein the fire extinguishing film is disposed at a position satisfying the condition represented by the following inequality (b). L3<L4 ··· (b) [In the formula, L3 represents the shortest distance from the fire extinguishing film to the positive electrode of the secondary battery, and L4 represents the shortest distance from the fire extinguishing film to the negative electrode of the secondary battery.] [8] A battery pack comprising: a housing; a secondary battery housed in the housing; a fire extinguishing film disposed in the housing; wherein the housing has a weakened portion that breaks under external pressure, and the value calculated by the following formula (1) is 15 or more. (C1 - V1) / A1 ··· (1) [In the formula, C1 represents the volume of the housing (unit: mm 3 ), V1 represents the volume of the secondary battery (unit: mm 3 ), and A1 represents the area of the opening (unit: mm 2 ).] [Advantages of the Invention]

[0012] According to the present disclosure, a battery pack is provided that has excellent fire extinguishing performance against a fire generated from a secondary battery.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present disclosure will be described in detail. However, the present disclosure is not limited to the following embodiments. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0015] [Battery Pack] 《First Embodiment》 Hereinafter, the battery pack according to the first embodiment will be described. FIG. 1 is a perspective view schematically showing the battery pack according to the present embodiment. FIG. 2 is a cross-sectional view taken at a position corresponding to the line a-a shown in FIG. 1. FIG. 3 is a cross-sectional view taken at a position corresponding to the line b-b shown in FIG. 1.

[0016] The battery pack 100 shown in FIGS. 1 to 3 includes a housing 10, a secondary battery 15 housed in the housing 10, and a fire extinguishing film 20 disposed in the housing. The housing 10 has an opening 10a that communicates the inside of the housing 10 with the outside of the housing 10. The value calculated by the following formula (1) of the battery pack 100 is 15 or more. (C1 - V1) / A1 ··· (1) [In the formula, C1 represents the volume of the housing (unit: mm 3 ) and V1 represents the volume of the secondary battery (unit: mm 3 ), and A1 represents the area of the opening (unit: mm 2 ).]

[0017] The battery pack 100 is excellent in fire extinguishing performance against a fire generated from the secondary battery. The inventors of the present invention surmise the reason for such an effect as follows. That is, when the secondary battery 15 ignites, high-temperature gas is generated. If an opening is provided in the housing to prevent an explosion caused by the gas, the fire extinguishing agent released from the fire extinguishing film 20 is pushed out of the battery pack. Since the value calculated by the above formula (1) of the battery pack 100 is within the above numerical range, the fire extinguishing agent is suppressed from being pushed out of the housing 10 by the generated gas. By the fire extinguishing agent remaining inside the housing 10, the battery pack 100 becomes excellent in fire extinguishing performance against a fire generated from the secondary battery.

[0018] The value calculated by the above formula (1) is preferably 20 or more, more preferably 40 or more, still more preferably 70 or more, and particularly preferably 100 or more. When the value calculated by the above formula (1) is equal to or greater than the above lower limit value, there is a tendency for the fire extinguishing performance to be further improved while preventing an explosion caused by gas. The value calculated by the above formula (1) may be, for example, 10000 or less, 1500 or less, or 150 or less.

[0019] In formula (1), the volume of the housing is the volume calculated assuming that the housing has no opening. The volume is calculated based on the inner dimensions of the housing. When the secondary battery is housed in an exterior package, in formula (1), the volume of the secondary battery is the volume of the exterior package. The volume is calculated based on the outer dimensions of the exterior package.

[0020] The battery pack 100 can be suitably used, for example, in various vehicles such as automobiles, bicycles, agricultural machines, and aircraft, electronic devices such as notebook personal computers and mobile phones, and other consumer devices using secondary batteries.

[0021] Hereinafter, the housing, the secondary battery, and the fire extinguishing film constituting the battery pack according to the present embodiment will be described in detail.

[0022] <Housing> The material constituting the housing 10 may be resin or metal. Examples of the metal include SUS (stainless steel), aluminum, iron, and high-tensile steel. Examples of the resin include PE (polyethylene), PP (polypropylene), PVC (vinyl chloride resin), PS (polystyrene), ABS resin, AS resin, PET (polyethylene terephthalate), PMMA (acrylic resin), PC (polycarbonate), PA (polyamide), POM (acetal resin), PBT (polybutylene terephthalate), phenolic resin, and epoxy resin. Further, from the viewpoint of heat resistance, it is preferable that one or more flame retardants are added to these resins. Examples of the flame retardant include halogen-based flame retardants, phosphorus-based flame retardants, inorganic flame retardants, nitrogen-based flame retardants, and silicone-based flame retardants.

[0023] The shape of the housing 10 is not particularly limited, and examples thereof include a cube, a rectangular parallelepiped, and a cylindrical shape.

[0024] The housing 10 has only one opening 10a that communicates the inside and the outside thereof. Since the number of the openings 10a is one, compared with the case where the number of the openings is two or more, the fire extinguishing agent discharged from the fire extinguishing film 20 stays, and it becomes easier to apply the fire extinguishing agent to the flame discharged from the opening 10a. Thereby, the battery pack 100 tends to have more excellent fire extinguishing performance.

[0025] The shape of the opening 10a is not particularly limited. For example, it may be a rectangular shape with a width of 0.5 to 200 mm and a height of 0.5 to 200 mm, or may be a circular shape with a diameter of 1 to 30 mm. A safety valve may be provided in the opening so that when the internal pressure of the housing 10 rises, gas can be discharged through the safety valve to reduce the pressure.

[0026] The position where the opening 10a is provided is not particularly limited, but it is preferable that the opening is formed at a position that satisfies the condition represented by the following inequality (a). L1>L2···(a) [In the formula, L1 indicates the shortest distance from the opening to the positive electrode of the secondary battery, and L2 indicates the shortest distance from the opening to the negative electrode of the secondary battery.]

[0027] According to the study by the present inventors, the flame from the secondary battery is likely to be discharged from the positive electrode side of the secondary battery. By selectively forming the opening at a position that satisfies the condition represented by the inequality (a), it is possible to suppress the flame from the secondary battery from jetting out to the outside of the battery pack. As shown in FIG. 3, in the present embodiment, the opening 10a is formed at a position far from the positive electrode 15p of the secondary battery 15 and close to the negative electrode 15n.

[0028] As described above, an example of the housing 10 has been described, but the housing is not limited to the above example. The housing may have, for example, in addition to the opening 10a, an opening on the surface opposite to the surface where the opening 10a is provided. That is, the housing may have two or more openings.

[0029] <Secondary battery> Although three secondary batteries are illustrated in FIG. 2, the number of secondary batteries is not limited thereto. The connection between the secondary batteries is not particularly limited and may be either in series or in parallel.

[0030] The shape of the secondary battery is not particularly limited, and examples thereof include a cylindrical shape, a rectangular shape, and a pouch shape. When there are a plurality of secondary batteries, the shapes of the secondary batteries may be the same or different.

[0031] Examples of the secondary battery include a lead storage battery, a lithium-ion battery, a nickel-metal hydride battery, and a nickel-cadmium battery. Since the secondary battery has a large capacity, it is preferably a lithium-ion battery. The orientation of the secondary battery is not limited to the top, bottom, left, or right of the housing.

[0032] <Fire extinguishing film> In the present embodiment, the fire extinguishing film 20 is disposed on the inner wall of the top surface of the housing 10 and the inner wall of the side surface facing the positive electrode 15p of the secondary battery. The position where the fire extinguishing film is disposed is not limited to these positions and can be appropriately adjusted according to the arrangement of the secondary battery 15. The fire extinguishing film 20 may be disposed, for example, on the inner wall of another side surface or the inner wall of the bottom surface of the housing 10. The fire extinguishing film 20 may be disposed at one location or at two or more locations.

[0033] The position where the fire extinguishing film is disposed is not particularly limited, but it is preferable that the fire extinguishing film is disposed at a position that satisfies the condition represented by the following inequality (b). L3 < L4 ··· (b) [In the formula, L3 represents the shortest distance from the fire extinguishing film to the positive electrode of the secondary battery, and L4 represents the shortest distance from the fire extinguishing film to the negative electrode of the secondary battery.]

[0034] Since it is assumed that the flame from the secondary battery is likely to be emitted from the positive electrode side of the secondary battery, by selectively forming the fire extinguishing film at a position that satisfies the condition represented by the inequality (b), the flame emitted from the secondary battery can be effectively extinguished.

[0035] FIG. 4 is a schematic cross-sectional view showing an example of the fire extinguishing film. As shown in FIG. 4, the fire extinguishing film 20 has a laminated structure including a base material 21 and a fire extinguishing agent layer 22. Hereinafter, each layer of the fire extinguishing film 20 will be described in detail.

[0036] (Base material) In view of the fact that the temperature of the flame is generally about 700°C to 900°C, a resin can be selected as the material of the base material 21. Examples of the resin include polyolefins (LLDPE, PP, COP, CPP, etc.), polyesters (PET, etc.), fluororesins (PTFE, ETFE, EFEP, PFA, FEP, PCTFE, etc.), PVC, PVA, acrylic resins, epoxy resins, polyamides, and polyimides. With these resins, holes can be formed by heat. Also, by selecting a transparent material, it becomes easier to inspect the appearance of the fire extinguishing film and confirm the replacement time. The base material may contain a fire extinguishing agent described later.

[0037] The thickness, breaking strength, etc. of the base material can be appropriately selected according to the amount of heat, impact, and allowable space at the time of fire outbreak. For example, if the base material is thick, strength and rigidity can be obtained, a highly planar form can be obtained, and handling becomes easy. Also, if the base material is thin, the fire extinguishing film can be arranged in a narrow space, and since holes are formed in a short time, the fire extinguishing start time can be shortened. The thickness of the base material can be, for example, 4.5 to 100 μm, and may be 12 to 50 μm. The base material may be a laminate of a plurality of base materials.

[0038] (Fire extinguishing agent layer) The fire extinguishing agent layer preferably contains a fire extinguishing agent and a binder resin for fixing the fire extinguishing agent.

[0039] As the fire extinguishing agent, those having the so-called four elements of fire extinguishing (removing action, cooling action, suffocating action, negative catalytic action) can be appropriately used according to the fire extinguishing target. Examples of the fire extinguishing agent include potassium salts, sodium salts, ammonium salts, etc. From the viewpoint of fire extinguishing performance in particular, potassium citrate, which is a potassium salt, is preferably used. Further, it is preferable that the fire extinguishing agent contains an oxidizing agent to promote the reaction of the agent, and potassium chlorate is preferably used from the viewpoint of oxidation performance in particular.

[0040] The content of the fire extinguishing agent may be 60% by mass or more, may be 90% by mass or more, or may be 100% by mass based on the total amount of the fire extinguishing agent layer. Thereby, the battery pack 100 tends to easily exhibit excellent fire extinguishing performance.

[0041] The ratio (%) of the amount of the fire extinguishing agent to the void in the housing calculated by the following formula (3) may be 0.015% or more, may be 0.55% or more, may be 1.5% or more, or may be 10% or less.

[0042] Ratio (%) = {Volume of the fire extinguishing agent contained in the fire extinguishing agent layer / (Volume of the housing - Volume of the secondary battery)} × 100 ··· (3)

[0043] As the binder resin, a thermoplastic resin and a thermosetting resin can be used. Examples of the thermoplastic resin include polyolefin resins such as polypropylene-based resins, polyethylene-based resins, poly(1-)butene-based resins, polypentene-based resins, polystyrene-based resins, acrylonitrile-butadiene-styrene-based resins, methyl methacrylate-butadiene-styrene resins, ethylene-vinyl acetate resins, ethylene-propylene resins, polycarbonate-based resins, polyphenylene ether-based resins, acrylic resins, polyamide-based resins, polyvinyl chloride-based resins, polyvinyl alcohol (PVA), and polyvinyl butyral (PVB).

[0044] Examples of the thermosetting resin include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), 1,2-polybutadiene rubber (1,2-BR), styrene-butadiene rubber (SBR), chloroprene rubber (CR), nitrile rubber (NBR), butyl rubber (IIR), ethylene-propylene rubber (EPR, EPDM), chlorosulfonated polyethylene (CSM), acrylic rubber (ACM, ANM), epichlorohydrin rubber (CO, ECO), highly vulcanized rubber (T), silicone rubber (Q), fluororubber (FKM, FZ), urethane rubber (U), etc., polyurethane resin, phenol resin, epoxy resin, and polyvinyl ether (PMVE)-maleic anhydride resin, etc.

[0045] The content of the binder resin may be 30% by mass or less, may be 15% by mass or less, or may be 13% by mass or less based on the total amount of the fire extinguishing agent layer.

[0046] The binder resin may contain a curing agent component. Further, from the viewpoint of property stability, the binder resin may contain any additives such as a surfactant, a silane coupling agent, and an anti-blocking agent.

[0047] The fire extinguishing agent layer 22 may contain other components in addition to the fire extinguishing agent and the binder resin. Examples of the other components include a curing agent. Also, from the viewpoint of property stability, examples of the other components include a surfactant, a silane coupling agent, and an anti-blocking agent.

[0048] The fire extinguishing agent layer 22 may be formed, for example, by molding a composition containing a fire extinguishing agent and a binder resin. The above composition may further contain a liquid medium in addition to the fire extinguishing agent and the binder resin.

[0049] Examples of the liquid medium include organic solvents. Examples of the organic solvents include water-soluble solvents, such as alcohols like methanol, ethanol, isopropyl alcohol, and n-propyl alcohol; ketones like acetone and methyl ethyl ketone; glycols like ethylene glycol and diethylene glycol; glycol ethers like N-methylpyrrolidone (NMP), tetrahydrofuran, and butyl cellosolve. From the perspective that organic salts and inorganic salts have deliquescence, the liquid medium may be an alcohol-based solvent, and specifically, it may be ethanol.

[0050] The fire extinguishing agent layer 22 is formed, for example, by coating the above composition on the base material 21 to form a coating film and drying the coating film. The coating can be performed by a wet coating method. Examples of the wet coating method include a gravure coating method, a comma coating method, a dip coating method, a curtain coating method, a spin coating method, a sponge roll method, and a die coating method.

[0051] Although an example of the fire extinguishing film has been described above, the fire extinguishing film is not limited to the above example. The fire extinguishing film may further include an adhesive layer, for example, on the surface of the base material 21 opposite to the fire extinguishing agent layer 22.

[0052] (Adhesive layer) As the material of the adhesive layer, known materials as adhesives can be appropriately applied. For example, acrylic adhesives, urethane adhesives, silicone adhesives, and rubber adhesives can be used. The thickness of the adhesive layer is preferably 1 μm to 100 μm.

[0053] (Packaging material) The base material 21 and the fire extinguishing agent layer 22 may be enclosed in the packaging material 24. FIG. 5 is a plan view schematically showing an example of the fire extinguishing film. FIG. 6 is a schematic cross-sectional view taken along line II-II of the fire extinguishing film shown in FIG. 5. The fire extinguishing film 20 includes a peripheral portion 20a. As shown in FIG. 6, the packaging material 24 includes a resin film 24a, a water vapor barrier layer 24b, and an adhesive layer 24c. The peripheral portion 20a is formed by a sealing portion between the adhesive layers 24c of the pair of packaging materials 24. Hereinafter, each layer of the packaging material 24 will be described in detail.

[0054] Examples of the material of the resin film 24a include polyolefin resins, polyester resins, fluororesins, vinyl resins, acrylic resins, epoxy resins, polyamides, polyimides, urethane resins, styrene resins, polycarbonates, ketone resins, sulfone resins, and cellulose resins.

[0055] Examples of the water vapor barrier layer 24b include inorganic metal oxide vapor deposition layers such as alumina vapor deposition layers and silica vapor deposition layers, and metal foils such as aluminum foils. When the water vapor barrier layer is an inorganic metal oxide vapor deposition layer, the inorganic metal oxide vapor deposition layer may be disposed on the main surface of the resin film on the side of the fire extinguishing agent layer.

[0056] The water vapor permeability of the packaging material 24 can be 2×10 2 / m 2 / day or less, and may be 1×10 2 g / m 2 / day or less. The water vapor permeability is measured in accordance with JIS K 7129 under the conditions of 40°C and 90% RH.

[0057] Examples of the material of the adhesive layer 24c include heat seal materials, adhesives, and pressure-sensitive adhesives.

[0058] The peripheral portion 20a is formed by a sealing portion. The sealing portion prevents the fire extinguishing agent layer 22 from coming into contact with air, and can suppress deterioration of the property stability. When the adhesive layer 24c has heat sealability, the sealing portion may be formed by heat fusion.

[0059] The adhesion strength between the packaging materials 24 in the sealing portion may be 5 N / 15 mm or more, may be 7 N / 15 mm or more, or may be 10 N / 15 mm or more from the viewpoint of stably enclosing the fire extinguishing agent layer. The adhesion strength can be varied by adjusting the resin layer painter, the adhesive, the heat seal conditions (heat seal temperature, pressure, and time), and the like.

[0060] The adhesion strength between the packaging materials 24 is measured as follows. That is, a sample in which a pair of packaging materials 24 are bonded together is prepared. The sealing portion of this sample is cut out to a width of 15 mm, and T-peel is performed at a peeling speed of 300 mm / min with a tensile tester placed in an environment at room temperature of 23°C in accordance with JIS K6854-3. The average strength from the start of peeling until the sealing portion of the packaging material 24 is separated is defined as the adhesion strength between the packaging materials 24.

[0061] The packaging material shown in FIG. 6 is provided with a water vapor barrier layer, but the packaging material may not be provided with a water vapor barrier layer. The fire extinguishing film shown in FIG. 6 is provided with a base material, but the fire extinguishing film may not be provided with a base material.

[0062] 《Second Embodiment》 Hereinafter, the battery pack according to the second embodiment will be described. FIG. 7 is a cross-sectional view schematically showing the battery pack 200 according to the present embodiment. The battery pack 200 is different from the battery pack 100 in that it has a fragile portion 10b that breaks due to external pressure to form an opening instead of an opening portion. Other points may be the same as those of the battery pack 100 according to the first embodiment.

[0063] The fragile portion 15b may break due to external pressure because its thickness is thinner than other portions of the housing. The thickness of the fragile portion 15b may be, for example, 30% or less, 20% or less, 10% or less, or 5% or less based on the thickness of other portions of the housing. The fragile portion 15b may be a door that opens due to external pressure.

[0064] The housing 10 has one weak part 10b. Since the number of weak parts 10b is one, compared with the case where the number of openings is two or more, the fire extinguishing agent discharged from the fire extinguishing film 20 stays, and it becomes easier to apply the fire extinguishing agent to the flame discharged from the weak part 10b. As a result, the battery pack 200 tends to have even better fire extinguishing performance.

[0065] As described above, the embodiments of the present disclosure have been described in detail, but the present disclosure is not limited to the above embodiments.

Example

[0066] The present disclosure will be described in more detail with reference to the following examples, but the present disclosure is not limited to these examples.

[0067] <Production of Fire Extinguishing Film> Potassium chlorate (KClO 3 ) and tripotassium citrate were pulverized in an agate mortar so that the average particle diameter D50 was 12 μm or less to prepare a fire extinguishing agent. A composition for forming a fire extinguishing agent layer was obtained by mixing this fire extinguishing agent with various materials at the following mixing ratios.

[0068] · 87.4 parts by mass of a mixture of tripotassium citrate and potassium chlorate · 39.4 parts by mass of an ether-based urethane resin solution · 87 parts by mass of ethanol

[0069] A polyethylene terephthalate (PET) film was prepared as a base material. The composition for forming a fire extinguishing agent layer was applied onto the PET film by an applicator to form a coating film. The coating film was dried in an oven at 75°C for 7 minutes. As a result, a fire extinguishing film having a fire extinguishing agent layer (thickness: 150 μm) formed on the base material was obtained.

[0070] <Production of First to Third Members> First to third members were produced in which a pair of opposing surfaces out of the six surfaces of a rectangular parallelepiped were open. The first to third members constitute a part of the housing.

[0071] (The first member) Two stainless steel plates with a thickness of 1.5 mm were prepared. Each stainless steel plate was bent at two places by 90° to obtain a pair of U-shaped (or U-shaped) members. By screwing the pair of U-shaped members together, a first member (inner dimensions: 80 mm × 80 mm × 40 mm) with a set of opposite faces of the six faces of a rectangular parallelepiped open was obtained.

[0072] (The second member) A second member was obtained in the same manner as the first member, except that the inner dimensions were 80 mm × 110 mm × 45 mm.

[0073] (The third member) Two stainless steel plates with a thickness of 2.0 mm were prepared. Each stainless steel plate was bent at two places by 90° to obtain a pair of U-shaped (or U-shaped) members. By screwing the pair of U-shaped members together, a third member (inner dimensions: 93 mm × 184 mm × 50 mm) with a set of opposite faces of the six faces of a rectangular parallelepiped open was obtained.

[0074] <Fabrication of the battery pack> (Example 1)

[0075] The battery pack 100 shown in FIGS. 1 to 3 was obtained. Specifically, three cylindrical lithium-ion batteries (ternary type, rated 3.7 V, capacity 3600 mA) were prepared. The total volume of the three lithium-ion batteries is 49621 mm 3It was. Three lithium-ion batteries were placed inside the first member. Also, a fire extinguishing film was attached to the top surface of the first member and the side surface facing the positive electrode of the lithium-ion battery of the first member. Transparent acrylic plates were respectively arranged on the two open surfaces of the first member. On one of the two open surfaces of the first member, the installation position of the acrylic plate was adjusted, and a slit (opening 10a, size: width 74 mm × height 10 mm) was formed between the top surface of the first member and the acrylic plate. As a result, a housing (rectangular parallelepiped shape, inner dimensions: 80 mm × 80 mm × 40 mm) having one opening and consisting of a rectangular parallelepiped member and an acrylic plate was obtained. Also, as a result, a battery pack including the housing, the secondary battery, and the fire extinguishing film was obtained. The opening is formed at a position satisfying the condition represented by the above inequality (a). The fire extinguishing film is arranged at a position satisfying the condition represented by the above inequality (b).

[0076] (Example 2) A battery pack was obtained in the same manner as in Example 1, except that slits (size: width 74 mm × height 5 mm) were formed between the top surface and the acrylic plate on each of the two opposing side surfaces of the housing.

[0077] (Example 3) A battery pack was obtained in the same manner as in Example 2, except that the sizes of the two slits formed in the housing were width 74 mm × height 3 mm.

[0078] (Example 4) A battery pack was obtained in the same manner as in Example 2, except that a second member was used instead of the first member and the sizes of the two slits formed in the housing were width 74 mm × height 2 mm.

[0079] (Example 5) A battery box (size: 75 mm × 170 mm × 90 mm) having a 7×4 array of battery storage holes in a staggered pattern was prepared. Twenty-eight cylindrical lithium-ion batteries (ternary type, rated voltage 3.7 V, capacity 3600 mA) were stored in the battery box. The battery box was put into a plastic bag and placed inside the third member. The volume of the battery box is 1147500 mm3 It was. Also, a fire extinguishing film was attached to the top surface of the third member and the side surface facing the positive electrode of the lithium-ion battery of the third member. Transparent acrylic plates were respectively arranged on the two open surfaces of the third member. At the two open surfaces of the third member, the installation positions of the acrylic plates were adjusted, and a slit (opening 10a, size: width 83 mm × height 10 mm) was formed between the top surface of the third member and the acrylic plate. As a result, a housing (rectangular parallelepiped shape, inner dimensions: 93 mm × 184 mm × 50 mm) having two openings and composed of a rectangular parallelepiped member and an acrylic plate was obtained. Also, thereby, a battery pack including the housing, the secondary battery, and the fire extinguishing film was obtained.

[0080] (Comparative Example 1) A battery pack was obtained in the same manner as in Example 2, except that the sizes of the two slits formed in the housing were width 74 mm × height 40 mm.

[0081] (Comparative Example 2) A battery pack was obtained in the same manner as in Example 2, except that a fire extinguishing film was not attached to the top surface of the first member and the side surface facing the positive electrode of the lithium-ion battery of the first member, and the sizes of the two slits formed in the housing were width 74 mm × height 5 mm.

[0082] The values calculated by the above formula (1) were obtained for the battery packs obtained in each example and comparative example. The results are shown in Table 1.

[0083] <Fire Extinguishing Test> The nail penetration test was carried out indoors at a temperature of 25 ± 5°C and a humidity of 30 - 80%. That is, a nail was pierced from the outside of the housing towards the lithium-ion battery inside the housing. As the nail, one with a sufficiently sharp tip (an N65 nail made of stainless steel, 65 mm in length, and a body diameter of approximately 3.05 mm) was used. The nail penetration speed was 40 mm / second. The depth of nail penetration into the lithium-ion battery was set to 18 mm or more. That is, the nail penetrated through the fire extinguishing film attached to the housing and the top surface side and the lithium-ion battery, and the tip of the nail was stabbed into the bottom surface of the housing. As a result, thermal runaway of the lithium-ion battery occurred and the lithium-ion battery caught fire. Then, it was confirmed whether the fire extinguishing agent of the fire extinguishing film could react and extinguish the fire, and the evaluation was carried out according to the following criteria. The results are shown in Table 1.

[0084] (Criterion) A: Fire extinguished B: Fire not extinguished

[0085] Also, the order of the fire extinguishing time was confirmed in each example. The group that could extinguish the fire in the shortest time was designated as "1", the group that could extinguish the fire in the next shortest time was designated as "2", and the group that could extinguish the fire in the longest time was designated as "3", and the results are shown in Table 1.

[0086]

Table 1

Explanation of Symbols

[0087] 10… Housing, 10a… Opening, 10b··· Weak part, 15… Secondary battery, 20… Fire extinguishing film, 100, 200… Battery pack.

Claims

1. A housing, a secondary battery housed in the housing, a fire extinguishing film disposed in the housing, comprising: the housing having an opening that communicates between the inside and the outside of the housing, a battery pack in which the value calculated by the following formula (1) is 15 or more. (C1 - V1) / A1...(1) [wherein, C1 represents the volume of the housing (unit: mm ３ ), V1 represents the volume of the secondary battery (unit: mm ３ ), and A1 represents the area of the opening (unit: mm ２ ).]

2. The battery pack according to claim 1, wherein the value calculated by the formula (1) is 100 or more.

3. The battery pack according to claim 1 or 2, wherein the housing has only one opening.

4. The fire extinguishing film has a laminated structure including a base material and a fire extinguishing agent layer, The battery pack according to claim 1 or 2, wherein the fire extinguishing agent layer contains a fire extinguishing chemical and a binder resin.

5. The battery pack according to claim 4, wherein the fire extinguishing chemical contains potassium citrate and potassium chlorate.

6. The battery pack according to claim 1 or 2, wherein the opening is formed at a position satisfying the condition represented by the following inequality (a). L1 > L2...(a) [In the formula, L1 represents the shortest distance from the opening to the positive electrode of the secondary battery, and L2 represents the shortest distance from the opening to the negative electrode of the secondary battery.]

7. The battery pack according to claim 1 or 2, wherein the fire extinguishing film is disposed at a position satisfying the condition represented by the following inequality (b). L3 < L4...(b) [In the formula, L3 represents the shortest distance from the fire extinguishing film to the positive electrode of the secondary battery, and L4 represents the shortest distance from the fire extinguishing film to the negative electrode of the secondary battery.]

8. A housing, a secondary battery housed in the housing, a fire extinguishing film disposed in the housing, comprising: the housing having a vulnerable part that breaks due to external pressure to form an opening, a battery pack in which the value calculated by the following formula (1) is 15 or more. (C1 - V1) / A1...(1) [In the formula, C1 represents the volume of the housing (unit: mm ３ ), V1 represents the volume of the secondary battery (unit: mm ３ ), and A1 represents the area of the opening (unit: mm ２ ).]

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