Battery case and battery for non-aqueous electrolyte secondary battery

Abstract

To provide a battery case for a non-aqueous electrolyte secondary battery that is light in weight and excellent in flame retardancy.SOLUTION: A battery case for a non-aqueous electrolyte secondary battery that includes an expanded graphite layer and a fiber-reinforced resin layer, the fiber-reinforced resin layer containing 10 to 60 mass % of at least one of carbon fiber and glass fiber relative to a total mass of the fiber-reinforced resin layer. A battery for a non-aqueous electrolyte secondary battery includes the battery case for a non-aqueous electrolyte secondary battery.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a battery case for a non-aqueous electrolyte secondary battery and a battery for a non-aqueous electrolyte secondary battery.

Background Art

[0002] In order to reduce CO2 emissions during vehicle operation and increase the driving range of electric vehicles and the like, weight reduction of vehicles has been required more than ever. From the perspective of improving weight reduction, it is conceivable to reduce the amount of metal used in battery packs and battery modules or to resinify the materials used. On the other hand, the safety of electric vehicles has also been required to be improved more than ever. For example, in various batteries typified by lithium batteries, the battery may catch fire due to internal short circuit, overcharging, external foreign object penetration, external overheating, abnormal heat generation, etc.

[0003] As a non-aqueous electrolyte secondary battery capable of suppressing heat generation of the battery during an abnormality such as an internal short circuit, for example, in Patent Document 1, a battery case is provided, and an expanded graphite layer and a high thermal conductivity layer are disposed in the battery case. The expanded graphite layer is composed of 70% by mass or more of expanded graphite and 30% by mass or less of a binder, and the thermal conductivity in the plane direction of the high thermal conductivity layer is higher than the thermal conductivity in the plane direction of the battery case and the thermal conductivity in the plane direction of the expanded graphite layer. A non-aqueous electrolyte secondary battery is disclosed.

[0004] Further, as a battery cell housing case capable of achieving both weight reduction and fire resistance, for example, in Patent Document 2, a bottom plate on which a plurality of battery cells are placed, side plates erected around the bottom plate, and a top plate provided at the upper end of the erected side plates so as to face the bottom plate. A battery cell housing case having a top plate, the top plate having a first top plate constituent layer and a second top plate constituent layer inside the first top plate constituent layer, the first top plate constituent layer being either an aluminum layer having a thickness of 0.5 to 5.0 mm or a non-foamed resin layer, and the second top plate constituent layer being a polyurethane foam layer containing a flame retardant. A battery cell housing case is disclosed.

[0005] As a resin battery cell housing that satisfies the requirements for both chemical resistance and water permeability resistance, and also offers excellent productivity, for example, Patent Document 3 discloses a battery cell housing comprising at least a resin molded body and a metal layer formed on its surface. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-181519 [Patent Document 2] Japanese Patent Publication No. 2021-002420 [Patent Document 3] Japanese Patent Publication No. 2007-227121 [Overview of the project] [Problems that the invention aims to solve]

[0007] The battery case disclosed in Patent Document 1 is made of aluminum, so further weight reduction of the battery case is required to achieve vehicle weight reduction. The battery cases described in Patent Documents 2 and 3 are made of resin, and although they are lighter than metal cases, resin battery cases require further improvement in flame retardancy.

[0008] One embodiment of the present invention aims to solve the problem of providing a battery case for a non-aqueous electrolyte secondary battery that is lightweight and has excellent flame retardancy. Furthermore, another embodiment of the present invention aims to solve the problem of providing a lightweight and flame-retardant battery for a non-aqueous electrolyte secondary battery. [Means for solving the problem]

[0009] The means for solving the above problems include the following embodiments. <1> It comprises an expanded graphite layer and a fiber-reinforced resin layer, The fiber-reinforced resin layer contains at least one of carbon fibers and glass fibers in an amount of 10% to 60% by mass relative to the total mass of the fiber-reinforced resin layer. Battery case for non-aqueous electrolyte rechargeable batteries. <2> The expanded graphite content in the expanded graphite layer is 50% by mass or more of the total mass of the expanded graphite layer. <1> A battery case for non-aqueous electrolyte secondary batteries as described above. <3> The fiber-reinforced resin layer comprises a polypropylene resin or a polyamide resin. <1> A battery case for non-aqueous electrolyte secondary batteries as described above. <4> The aforementioned expanded graphite layer is located on the inside of the battery case. <1> A battery case for non-aqueous electrolyte secondary batteries as described above. <5> Further including an electromagnetic wave shielding layer, <1> A battery case for non-aqueous electrolyte secondary batteries as described above. <6> The aforementioned fiber-reinforced resin layer contains an electromagnetic wave shielding filler. <1> A battery case for non-aqueous electrolyte secondary batteries as described above. <7> <1> ~ <6> A battery for non-aqueous electrolyte secondary batteries, comprising a battery case for non-aqueous electrolyte secondary batteries as described in any one of the following. [Effects of the Invention]

[0010] According to one embodiment of the present invention, a battery case for a non-aqueous electrolyte secondary battery that is lightweight and has excellent flame retardancy is provided. According to one embodiment of the present invention, a battery for a non-aqueous electrolyte secondary battery that is lightweight and has excellent flame retardancy is provided. [Modes for carrying out the invention]

[0011] The contents of the present invention will be described in detail below. The description of the constituent elements described below may be based on representative embodiments of the present invention, but the present invention is not limited to such embodiments. In this specification, the term "polymer" includes homopolymers and copolymers. In this specification, the "~" symbol indicating a numerical range is used to mean that the numbers before and after it are included as the lower and upper limits, respectively. In this specification, the "~" indicating a numerical range means that the unit described on either side thereof indicates the same unit unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. Hereinafter, the present invention will be described in detail.

[0012] (Battery case for non-aqueous electrolyte secondary battery) The battery case for a non-aqueous electrolyte secondary battery according to the present invention includes an expanded graphite layer and a fiber-reinforced resin layer, and the fiber-reinforced resin layer contains at least one of carbon fiber and glass fiber in an amount of 10% to 60% by mass based on the total mass of the fiber-reinforced resin layer. The battery case for a non-aqueous electrolyte secondary battery according to the present invention (hereinafter, also simply referred to as "battery case") has the above configuration, and thus is lightweight and excellent in flame retardancy. Although the reason is not clear, it is presumed as follows. Since the above battery case includes an expanded graphite layer, for example, when the battery catches fire, it is presumed that the expanded graphite layer expands due to contact with the flame of the expanded graphite layer, and the expanded graphite layer becomes a heat insulating layer, exhibiting a fireproof and flame retardant effect. Further, since the above battery case includes a fiber-reinforced resin layer, it is lighter than a conventional battery case provided with a metal layer. Hereinafter, details of each component of the battery case will be described.

[0013] <Fiber-reinforced resin layer> The battery case according to the present invention includes a fiber-reinforced resin layer. The fiber-reinforced resin layer is a layer containing a resin and at least one of carbon fiber and glass fiber, and examples of the resin contained in the fiber-reinforced resin layer include a thermoplastic resin or a thermosetting resin.

[0014] <<Resin>> Examples of the thermoplastic resin include polycarbonate, styrene resin, polyamide resin, polyester resin, polyphenylene sulfide (PPS resin), modified polyphenylene ether (modified PPE resin), polyacetal (POM resin), liquid crystal polyester, polyarylate, acrylic resins such as polymethyl methacrylate resin (PMMA), vinyl chloride, polyimide (PI), polyamideimide (PAI), polyetherimide (PEI), polysulfone, polyethersulfone, polyketone, polyetherketone, polyetheretherketone (PEEK), polyolefin resins such as polyethylene and polypropylene, modified polyolefin resins, phenolic resins, and phenoxy resins. Among these, from the viewpoints of light weight and excellent flame retardancy, the thermoplastic resin is preferably an acrylic resin and a polyolefin resin, more preferably a polyamide, a polyester, and a polypropylene resin, and still more preferably a polyamide resin and a polypropylene resin.

[0015] Examples of the thermosetting resin include epoxy resin, thermosetting unsaturated polyester resin, and phenolic resin.

[0016] From the viewpoints of light weight and excellent flame retardancy, the resin contained in the fiber reinforced resin layer is preferably a thermoplastic resin, more preferably an acrylic resin and a polyolefin resin, still more preferably a polyamide, a polyester, and a polypropylene resin, and particularly preferably a polyamide resin and a propylene resin.

[0017] - Propylene resin - The above propylene resin may be an unmodified propylene resin or a propylene resin containing a carboxylic acid structure or a carboxylate structure by a method such as modification. When both an unmodified resin and a propylene resin containing a carboxylic acid or a carboxylate structure are used, the preferred mass ratio is the ratio of unmodified / modified, which is 99 / 1 to 80 / 20, more preferably 98 / 2 to 85 / 15, and still more preferably 97 / 3 to 90 / 10.

[0018] Propylene resin is a propylene polymer, such as homopolypropylene, random polypropylene, block polypropylene, or modified polypropylene. Propylene resin is a polymer containing structural units derived from propylene. Preferably, it is a copolymer containing structural units derived from propylene and structural units derived from an olefin other than propylene, selected from the group consisting of α-olefins, conjugated dienes, and unconjugated dienes.

[0019] Examples of α-olefins include α-olefins with 2 to 20 carbon atoms, excluding propylene, such as ethylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 1-nonene, 1-octene, 1-heptene, 1-hexene, 1-decene, 1-undecene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Among these, 1-butene, ethylene, 4-methyl-1-pentene, and 1-hexene are preferred, and 1-butene and 4-methyl-1-pentene are more preferred. Examples of conjugated and unconjugated dienes include butadiene, ethylidene norbornene, dicyclopentadiene, and 1,5-hexadiene.

[0020] Two or more α-olefins, conjugated dienes, and unconjugated dienes may be used in combination. In particular, the propylene resin is preferably a copolymer of propylene and α-olefin. Examples of such copolymers include ethylene-propylene copolymer, propylene-1-butene copolymer, and ethylene-propylene-1-butene copolymer.

[0021] From the viewpoint of the mechanical strength of the resulting battery case, the proportion of structural units derived from propylene in the propylene resin is preferably 50 to 100 mol%, more preferably 60 to 100 mol%, and particularly preferably 70 to 100 mol%, relative to the total constituent units of the propylene resin.

[0022] Propylene resin may have a structure that includes, for example, elements from groups 15 to 17 of the periodic table. Examples of structures that include elements from groups 15 to 17 of the periodic table include functional groups such as carboxylic anhydrides, carboxylic acid groups, amino groups, acid amide groups, and halogen groups. Such structures can be introduced by known methods such as radical graft reactions. Examples of Group 17 elements include halogen atoms such as chlorine atoms. Examples of Group 16 elements include oxygen atoms and sulfur atoms, with oxygen atoms being preferred. Examples of Group 15 elements include nitrogen atoms, with oxygen atoms being preferred. In other words, structures containing Group 15 to 17 elements of the periodic table can preferably be carboxylic acids (salts). Carboxylic acids (salts) are preferably carboxylic acid groups or carboxylic anhydride groups, more preferably groups having a maleic anhydride structure.

[0023] When the propylene resin has a structure containing elements from groups 15 to 17 of the periodic table, the content of those elements is preferably 0.0003 to 5% by mass, more preferably 0.0005 to 4.5% by mass, even more preferably 0.0008 to 4.3% by mass, and particularly preferably 0.001 to 4% by mass, relative to the total mass of the propylene resin.

[0024] The above content can be calculated, for example, from the charging ratio of each component in a graft reaction. It can also be determined using an elemental analyzer (e.g., varioELIII: manufactured by Elemental).

[0025] The propylene resin preferably contains both unmodified propylene resin and acid-modified propylene resin.

[0026] The melt flow rate (MFR) of propylene resin, measured under conditions of 230°C and a 2.16 kg load, is typically 3 to 100 g / 10 min, preferably 15 to 100 g / 10 min. It is determined by the measurement method described in the examples below.

[0027] <<Carbon Fiber>> Various known carbon fibers can be used as the carbon fiber, including, for example, polyacrylonitrile-based, rayon-based, pitch-based, polyvinyl alcohol-based, regenerated cellulose-based, and pitch-based carbon fibers manufactured from mesophase pitch. The carbon fiber may be a general-purpose fiber or a high-strength fiber. Furthermore, the carbon fiber may be a long fiber, a short fiber, or a recycled fiber. The fiber diameter of the carbon fiber is preferably 3 to 30 μm, more preferably 4 to 10 μm.

[0028] <<Glass fiber>> There are no particular restrictions on the glass fibers, and examples include fibers made from glass compositions such as A glass, C glass, D glass, E glass, and S glass. Among these, fibers made from the glass composition of E glass (alkali-free glass) are particularly preferred.

[0029] Carbon fibers and glass fibers may be short fibers or long fibers. Short fibers may be chopped fiber (cut fiber) type short fibers or pulp-type short fibers containing fibrils. Furthermore, carbon fibers and glass fibers may be single fibers or multiple single fibers twisted together.

[0030] The average fiber length of the carbon fibers and glass fibers is preferably 0.01 mm or more, more preferably 0.1 mm or more, even more preferably 1 mm or more, preferably 100 mm or less, more preferably 50 mm or less, and even more preferably 30 mm or less. When the average fiber length is within the above range, the reinforcing effect of the mechanical properties by the carbon fibers and glass fibers tends to be fully expressed, and the dispersion of carbon fibers and glass fibers in the fiber-reinforced resin layer is improved, resulting in a good appearance. The proportion of fibers with a fiber length of less than 0.1 mm to the total number of carbon fibers and glass fibers is preferably 18% or less.

[0031] The average fiber diameter of the carbon fibers and glass fibers is preferably 1 μm or more, more preferably 5 μm or more, preferably 30 μm or less, and more preferably 20 μm or less. In this configuration, the reinforcing fibers are less likely to break during molding, the impact strength of the resulting molded article tends to be higher, the appearance of the molded article is improved, and sufficient reinforcement effect is obtained for the mechanical properties of the molded article, such as rigidity and heat resistance.

[0032] The average fiber length and average fiber diameter can be determined, for example, by taking photographs of the reinforcing fibers with an optical microscope, measuring the length or diameter of 100 randomly selected reinforcing fibers in the resulting photographs, and taking the arithmetic mean of each measurement.

[0033] Among the above, preferred forms of glass fibers include, for example, "glass roving" which is made by continuously winding single fibers or multiple strands twisted together, "chopped strands" which have an average fiber length of 1 to 10 mm, and "milled fibers" which have been crushed to an average fiber length of about 10 to 500 μm.

[0034] The carbon fibers and glass fibers may be untreated fibers (hereinafter referred to as "fibers (C0)") or surface-treated fibers (hereinafter referred to as "surface-treated fibers (C1)").

[0035] For example, the "surface-treated fiber (C1)" may be a fiber that has been surface-treated using various sizing agents (hereinafter referred to as "sizing agent-treated fiber (C1A)"). The "sizing agent-treated fiber (C1A)" often includes the fiber (C0) and a sizing agent that coats the fiber (C0). Examples of stimulants include acrylic stimulants, urethane stimulants, and acid copolymer stimulants. Among these, acid copolymer stimulants are preferred as the converging agent.

[0036] Here, if the "sizing agent treated fiber (C1A)" is a glass fiber roving surface-treated with a sizing agent (hereinafter referred to as "sizing agent treated glass fiber roving"), then an acid copolymer-based sizing agent is preferred for the sizing agent included in the "sizing agent treated glass fiber roving" in order to ensure sufficient impregnation of the resin component into the sizing agent treated fiber. Acrylic-based sizing agents are also a suitable sizing agent.

[0037] On the other hand, if the "sizing agent treated fiber (C1A)" is a fiber other than "sizing agent treated glass fiber roving," for example, a chopped strand surface-treated with a sizing agent (hereinafter referred to as "sizing agent treated chopped strand"), the sizing agent contained in the "sizing agent treated chopped strand" is not limited to acid copolymer-based sizing agents, but may also be sizing agents other than acid copolymer-based sizing agents, such as acrylic-based sizing agents or urethane-based sizing agents. Even if a "sizing agent treated chopped strand" contains a sizing agent other than such an acid copolymer-based sizing agent, it is preferable because the resin component impregnation is sufficient, similar to a "sizing agent treated chopped strand" containing an acid copolymer-based sizing agent.

[0038] Carbon fibers and glass fibers may be treated with silane coupling agents, titanate coupling agents, aluminum coupling agents, zirconium coupling agents, borane coupling agents, curing catalysts, lubricants, fillers, thixotropic agents, tackifiers, waxes, heat stabilizers, light stabilizers, fluorescent whitening agents, foaming agents, pH adjusters, leveling agents, gelling inhibitors, dispersion stabilizers, antioxidants, radical scavengers, and heat-resistant agents as needed. It may contain one or more components selected from the following: agents, inorganic fillers, organic fillers, plasticizers, reinforcing agents, antibacterial agents, antifungal agents, rust inhibitors, thermoplastic resins, thermosetting resins, pigments, dyes, conductivity imparters, antistatic agents, moisture permeability enhancers, water repellents, oil repellents, hollow foams, water-containing compounds, flame retardants, water absorbents, moisture absorbents, deodorants, foam stabilizers, defoamers, antifungal agents, preservatives, antialgal agents, pigment dispersants, blocking inhibitors, and hydrolysis inhibitors.

[0039] Surface treatment methods for carbon fibers and glass fibers using a sizing agent include, for example, applying the sizing agent to the surface of the reinforcing fibers with an applicator, immersing the reinforcing fibers in the sizing agent, spraying the sizing agent onto the reinforcing fibers in a mist, and bringing the reinforcing fibers into contact with a roller to which the sizing agent is attached. Furthermore, the above surface treatment methods may be batch-type or continuous-type.

[0040] When carbon fibers and glass fibers are surface-treated with a sizing agent, the mass ratio of the sizing agent in the carbon fibers and glass fibers, i.e., the ignition loss, is preferably 0.1 to 1.5% by mass relative to the total mass of the carbon fibers and / or glass fibers. The mass ratio of the sizing agent (ignition loss) is measured for fibers obtained by applying the sizing agent to the reinforcing fibers using an applicator, for example, and drying them to completely volatilize the volatile substances. When the ignition loss of the sizing agent applied to the surface of the carbon fibers or glass fibers is 0.1% by mass or more, it is preferable because it can stabilize the interface between the resin and the carbon fibers and glass fibers as described above, and heat resistance can be exhibited. On the other hand, when the ignition loss of the sizing agent applied to the surface of the carbon fibers or glass fibers is 1.5% by mass or less, it is preferable because improvements in physical properties such as heat resistance can be observed.

[0041] The ignition loss of sizing agents in carbon fibers and glass fibers was measured according to JIS R 3420(2006)7.3.2. After surface treatment, the reinforcing fibers are bundled into a predetermined number of strands, wound up, and then cut and / or crushed as needed to be processed into chopped strands, milled fibers, yarn, roving, etc.

[0042] The fiber-reinforced resin layer may further contain fibers other than carbon fibers and glass fibers (hereinafter also referred to as "other fibers"), as long as it achieves the effects of the present invention. Other fibers include natural fibers such as cotton fibers, silk fibers, wood fibers, and cellulose fibers; and synthetic fibers made from synthetic resins such as all-aromatic polyamides (aramids), all-aromatic polyesters, all-aromatic polyesteramides, all-aromatic polyethers, all-aromatic polycarbonates, all-aromatic polyazomethine, polyphenylene sulfide, poly(para-phenylenebenzobisthiazole), poly(para-phenylenebenzobisthiazole), polybenzimidazole, polyetheretherketones, polyamideimides, polyimides, polytetrafluoroethylenes, polyvinyl alcohols, polyolefins, polyarylates, and fluorinated polymers.

[0043] The fiber-reinforced resin layer may contain carbon fibers and glass fibers, as well as fibers other than carbon fibers and glass fibers, and optionally any additives. Examples of optional additives include nucleating agents, antiblocking agents, pigments, fibers, fillers, dyes, lubricants, plasticizers, mold release agents, antioxidants, flame retardants, flame retardant aids, UV absorbers, antibacterial agents, surfactants, antistatic agents, weather stabilizers, heat stabilizers, anti-slip agents, foaming agents, crystallization aids, anti-fogging agents, anti-aging agents, hydrochloric acid absorbers, impact modifiers, crosslinking agents, co-crosslinking agents, crosslinking aids, adhesives, softeners, and processing aids. These additives may be used individually or in combination of two or more. Among these, flame retardants and flame retardant enhancers are preferred as additives.

[0044] There are no particular restrictions on the flame retardants used. Examples include halogenated flame retardants (e.g., halogenated aromatic compounds), phosphorus-based flame retardants (e.g., nitrogen-containing phosphate compounds, phosphate esters), nitrogen-based flame retardants (e.g., guanidine, triazine, melamine, and their derivatives), inorganic flame retardants (e.g., metal hydroxides), boron-based flame retardants, silicone-based flame retardants, sulfur-based flame retardants, and red phosphorus-based flame retardants. Examples of flame retardant additives include various antimony compounds, zinc-containing metal compounds, bismuth-containing metal compounds, magnesium hydroxide, and clayey silicates.

[0045] The flame retardant content is preferably 5% to 50% by mass, more preferably 10% to 45% by mass, and even more preferably 10% to 45% by mass, relative to the total mass of the fiber-reinforced resin layer.

[0046] The fiber-reinforced resin layer contains carbon fibers or glass fibers in an amount of 10% to 60% by mass relative to the total mass of the fiber-reinforced resin layer, preferably 10% to 60% by mass relative to the total mass of the fiber-reinforced resin layer, and more preferably 10% to 60% by mass relative to the total mass of the fiber-reinforced resin layer.

[0047] The density of the fiber-reinforced resin layer is preferably 0.9 to 1.8 g / cm³. 3 More preferably 1.0 to 1.7 g / cm³ 3 That is the case. The density of the fiber-reinforced resin layer is determined by the measurement method described in the examples below.

[0048] The thickness of the fiber-reinforced resin layer is preferably 500 to 40,000 μm, more preferably 1,000 to 30,000 μm, and even more preferably 1,000 to 20,000 μm.

[0049] <<Electromagnetic wave shielding filler>> From the viewpoint of preventing the leakage of electromagnetic noise generated from lithium-ion batteries and the like to the outside, it is preferable that the fiber-reinforced resin layer contains an electromagnetic shielding filler. The electromagnetic shielding filler is not particularly limited as long as it can shield electromagnetic waves, and any known and publicly available electromagnetic shielding filler can be used. As the electromagnetic shielding filler, a filler in which a conductive metal is coated on soft magnetic powder is preferred.

[0050] The soft magnetic powder is preferably silicon steel, Sendust alloy, permalloy alloy, Co-based or Fe-based amorphous alloy powder, or ferritic oxide powder. The conductive metal is the same as the conductive metal in the filler made of conductive metal contained in the electromagnetic wave shielding layer described later, and the preferred embodiment is the same.

[0051] While known methods can be used for coating with a conductive metal, electroless plating is particularly preferred. This method allows for a uniform coating of a certain amount on the surface of the powder. Electroless plating can be carried out according to conventional methods; for example, soft magnetic powder pieces are washed to activate the surface, added to an aqueous solution containing a complexing agent and a reducing agent, and then a salt of the conductive metal is added dropwise. Examples of complexing agents include salts of ammonia water, ethylenediaminetetraacetic acid, nitrilotriacetic acid, and triethylenetetraminehexaacetic acid, while examples of reducing agents include formalin, hydrazine and its derivatives, tartaric acid, and glucose. These can be appropriately selected depending on the conductive metal used. Examples of conductive metal salts include nitrates and sulfates.

[0052] The preferred amount of conductive metal coating varies depending on the type of soft magnetic powder, its size, shape, and the type of conductive metal. For example, since ferrite oxides have a lower specific gravity than alloy powders, even for identically shaped powders with almost the same coating thickness, using ferrite powders results in a higher metal mass ratio (%) in the coated powder compared to using alloy powders. For example, when using iron-based soft magnetic alloy powders with an average particle size of 5 to 200 μm and an aspect ratio of 10 to 50, and coating them with silver, copper, or nickel, a suitable coating amount is approximately 5 to 75% by mass per unit mass of the coated powder, preferably 10 to 50% by mass, and more preferably 10 to 20% by mass.

[0053] <<Method for forming a fiber-reinforced resin layer>> The method for forming the fiber-reinforced resin layer is not particularly limited, and conventionally known methods can be employed. For example, if the resin component is a curable resin, it is preferable to use a prepreg in which the resin component is impregnated into at least one of the carbon fibers and glass fibers, or a semipreg in which the resin component is partially impregnated (partially impregnated) into at least one of the carbon fibers and glass fibers to control the amount of voids, and then cure it by heat or the like to form a fiber-reinforced resin layer.

[0054] If the resin component is a thermoplastic resin, the resin can be mixed with at least one of the carbon fibers and glass fibers, and then molded into a fiber-reinforced film, fiber-reinforced sheet, fiber-reinforced plate, etc., by extrusion molding, injection molding, vacuum forming, pressure forming, press molding, etc., to form a fiber-reinforced resin layer. Alternatively, a masterbatch-like pellet consisting of at least one of the carbon fibers and glass fibers and a thermoplastic resin can be mixed with thermoplastic resin pellets, and a fiber-reinforced resin layer can be formed by injection molding, etc. Alternatively, a mixed mat consisting of at least one of the carbon fibers and glass fibers and a thermoplastic resin can be used, and a fiber-reinforced resin layer can also be formed by press molding, etc., at a temperature above the flow start temperature of the thermoplastic resin.

[0055] <<Expanded Graphite Layer>> The expanded graphite layer is preferably a layer containing expanded graphite and a binder. Expanded graphite is a material in which the interlayers of the graphite crystal structure are expanded. Examples include graphite, such as natural graphite or synthetic graphite, intercalated with acids such as sulfuric acid or organic compounds. Expanded graphite can be obtained, for example, by immersing graphite material in an acid (such as sulfuric acid or nitric acid). As the graphite mentioned above, it is preferable to use flaky graphite. The temperature at which the expansion of expanding graphite begins is not particularly limited, but it may be, for example, 150°C to 220°C. The "expansion initiation temperature" refers to the temperature at which a volume change occurs in the expanded graphite. The expansion ratio of the expanded graphite is not particularly limited, but may be, for example, 150% to 400%. The "expansion ratio" is calculated by dividing the volume of the expanded graphite after thermal expansion by the volume of the expanded graphite before thermal expansion, and multiplying by 100. The particle size of the expanded graphite before expansion is not particularly limited, but may be, for example, 10 μm to 100 μm.

[0056] The binder included in the expanded graphite layer is not particularly limited and can be, for example, styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVdF), acrylic resin, aramid resin, polytetrafluoroethylene (PTFE), etc.

[0057] The content of expanded graphite in the expanded graphite layer is preferably 50% or more, more preferably 70% to 99.5% by mass, even more preferably 81% to 99.0% by mass, and particularly preferably 85% to 98% by mass, based on the total mass of the expanded graphite layer. The content of binder in the expanded graphite layer is preferably 0.5% to 30% by mass, more preferably 1% to 19% by mass, and even more preferably 2% to 15% by mass, based on the total mass of the expanded graphite layer. The expanded graphite layer preferably consists of expanded graphite at a concentration of 70% by mass or more relative to the total mass of the expanded graphite layer, and a binder at a concentration of 30% by mass or less relative to the total mass of the expanded graphite layer.

[0058] The thickness of the expanded graphite layer is preferably 50 μm to 5,000 μm, and more preferably 100 μm to 3,000 μm.

[0059] From the viewpoint of having excellent flame retardancy, it is preferable that the expanded graphite layer is located inside the battery case, and more preferably that the expanded graphite layer is located on the inner surface of the battery case. A battery case typically contains a non-aqueous electrolyte and electrode groupings inside. "The interior of the battery case" refers to the side of the battery case where the non-aqueous electrolyte and electrode groupings are housed. "The inner surface of the battery case" refers to the surface inside the battery case.

[0060] <<Method for preparing an expanded graphite layer>> There are no particular restrictions on the method for producing the expanded graphite layer, and conventionally known production methods can be used. For example, the components contained in the expanded graphite layer can be melted and kneaded, and then the expanded graphite layer can be formed by conventionally known molding methods, such as injection molding or press molding. There are no particular restrictions on the melt-mixing method, and a method can be employed in which commonly used known mixers such as kneaders, roll mills, Banbury mixers, single-screw or twin-screw extruders are used to melt-mix the material at, for example, 180-250°C, followed by granulation or grinding.

[0061] <<Electromagnetic wave shielding layer>> The battery case according to the present invention may further include an electromagnetic wave shielding layer. The electromagnetic wave shielding layer is not particularly limited as long as it is a layer that shields electromagnetic waves, and a known and publicly available electromagnetic wave shielding layer can be used. The electromagnetic wave shielding layer is preferably a layer that includes, for example, a binder resin and the above-mentioned electromagnetic wave shielding filler. The above-mentioned electromagnetic wave shielding filler is synonymous with the electromagnetic wave shielding filler contained in the above-mentioned fiber-reinforced resin layer, and the preferred embodiment is the same. The electromagnetic shielding layer may be formed using a coating agent containing a conductive metal, or a conductive metal foil may be used as the electromagnetic shielding layer. There are no particular restrictions on the binder resin included in the electromagnetic wave shielding layer; examples include the resin included in the fiber-reinforced resin layer, and the same applies to preferred embodiments.

[0062] Examples of conductive metals constituting the electromagnetic wave shielding filler include copper, silver, iron, nickel, gold, palladium, chromium, or alloys thereof. Among these, the conductive metal is preferably composed of at least one metal selected from silver, nickel, copper, and stainless steel, and more preferably composed of at least one metal selected from copper and stainless steel. The electromagnetic wave shielding filler described above is preferably fibrous in shape. The diameter of the electromagnetic wave shielding filler is preferably 1 μm to 20 μm, and more preferably 4 μm to 8 μm. The length of the electromagnetic wave shielding filler is preferably 0.5 mm to 5.0 mm, and more preferably 1 mm to 2 mm. The content of the electromagnetic wave shielding filler is preferably 0.1% by mass or more and less than 30.0% by mass, more preferably 0.1% by mass to 10.0% by mass, and even more preferably 0.3% by mass to 5.0% by mass, relative to the total solid content of the electromagnetic wave shielding layer.

[0063] The thickness of the electromagnetic wave shielding layer is preferably 50 to 5,000 μm, more preferably 50 to 3,000 μm, and even more preferably 100 to 2,000 μm.

[0064] In the battery case, the expanded graphite layer and the fiber-reinforced resin layer may be laminated in contact with each other, or the electromagnetic wave shielding layer may be laminated between the expanded graphite layer and the fiber-reinforced resin layer. From the viewpoint of preventing the leakage of electromagnetic noise generated from lithium-ion batteries and the like to the outside, it is preferable that the electromagnetic shielding layer is laminated between the expanded graphite layer and the fiber-reinforced resin layer, and it is more preferable that the electromagnetic shielding layer is laminated between the expanded graphite layer and the fiber-reinforced resin layer, and that the expanded graphite layer and the fiber-reinforced resin layer are laminated in contact with each other. The battery case may further include other layers besides the electromagnetic shielding layer on the side opposite to the expanded graphite layer (i.e., above the fiber-reinforced resin layer). Other layers include, for example, a protective layer. An example of a protective layer is a layer made of the thermoplastic resin mentioned above.

[0065] <<Battery case for non-aqueous electrolyte secondary batteries>> The battery case according to the present invention is not particularly limited as long as it houses a battery for a non-aqueous electrolyte secondary battery, and for example, a case molded to house a lithium-ion battery can be used. When the battery case according to the present invention is applied to a battery pack for an electric vehicle, it is lighter than a metal case, so the driving range of the electric vehicle can be extended.

[0066] The shape of the battery case is not particularly restricted as long as it can accommodate a rechargeable battery; for example, it may be rectangular (flattened rectangular prism), cylindrical, or bag-shaped. The battery case may be equipped with external terminals, electrolyte injection holes, gas discharge valves, current interruption mechanisms (CID), etc.

[0067] <<How to make the case>> There are no particular restrictions on the method of forming the battery case, and known molding methods can be applied. For example, it can be formed by blow molding, injection molding, press molding, extrusion molding, extrusion blow molding, injection blow molding, vacuum molding, etc. Among the above molding methods, it is preferable that the battery case be formed by injection molding.

[0068] <Nonaqueous electrolyte secondary battery> The battery for a non-aqueous electrolyte secondary battery according to the present invention (hereinafter sometimes referred to as "non-aqueous electrolyte secondary battery") comprises the above-mentioned battery case for a non-aqueous electrolyte secondary battery. A non-aqueous electrolyte secondary battery can have the configuration of a conventionally known non-aqueous electrolyte secondary battery, as long as it includes the above-mentioned battery case. A conventionally known configuration of a non-aqueous electrolyte secondary battery includes, for example, an electrode body having a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrodes, and this electrode body is disposed in a battery case together with a non-aqueous electrolyte. As a non-aqueous electrolyte secondary battery, a lithium-ion secondary battery containing a non-aqueous electrolyte is a preferred example.

[0069] <<Positive electrode>> The positive electrode preferably includes a positive electrode current collector and a positive electrode composite layer formed on the main surface of the positive electrode current collector. The positive electrode current collector may be, for example, aluminum (Al) foil. The Al foil may be pure Al foil or Al alloy foil. The positive electrode current collector may have a thickness of, for example, 10 to 30 μm.

[0070] <<Positive electrode composite layer>> The positive electrode composite layer preferably contains a positive electrode active material, a conductive material, and a binder. The positive electrode composite layer may contain, for example, 80 to 98% by mass of positive electrode active material, 1 to 15% by mass or less of conductive material, and 1 to 5% by mass or less of binder. The positive electrode composite layer may have a thickness of, for example, 100 to 200 μm.

[0071] <<Positive electrode active material, conductive material, and binder>> The positive electrode active material, conductive material, and binder are not particularly limited. The positive electrode active material is, for example, LiCoO2, LiNiO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 It may also be O2 (NCM: nickel cobalt manganese oxide), LiMnO2, LiMn2O4, LiFePO4, etc. The conductive material may be, for example, acetylene black (AB), furnace black, vapor-grown carbon fiber (VGCF), graphite, etc. The binder may be, for example, PVDF (polyvinylidene fluoride), PTFE (polytetrafluoroethylene), etc.

[0072] <<Negative electrode>> The negative electrode preferably includes a negative electrode current collector and a negative electrode composite layer formed on the main surface of the negative electrode current collector. The negative electrode current collector may be, for example, a copper (Cu) foil. The negative electrode current collector may have a thickness of, for example, about 5 to 20 μm.

[0073] <<Negative electrode composite layer>> The negative electrode composite layer preferably contains a negative electrode active material and a binder. The negative electrode composite layer may contain, for example, 95 to 99% by mass of negative electrode active material and 1 to 5% by mass of binder. The negative electrode composite layer may have a thickness of, for example, about 50 to 150 μm.

[0074] <<Negative electrode active material and binder>> The negative electrode active material and binder are not particularly limited. The negative electrode active material may be, for example, graphite, easily graphitizable carbon, poorly graphitizable carbon, silicon, silicon oxide, tin, tin oxide, etc. These may also be coated with amorphous carbon. The binder may be, for example, carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), etc.

[0075] <<Non-aqueous electrolytes>> The non-aqueous electrolyte comprises a lithium salt, an additive, and a solvent. The lithium salt may be, for example, LiPF6, LiFSI, etc. The additive may be, for example, Li[B(C2O4)], LiPO2F2, vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), ethylene sulfite (ES), propanesalton (PS), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), LiBF2(C2O4), LiPF2(C2O4)2, etc. The solvent may be, for example, a mixture of cyclic carbonates and linear carbonates. The mixing ratio of cyclic carbonate to linear carbonate can be, in volume ratio, for example, cyclic carbonate:linear carbonate = 1:9 to 5:5. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of linear carbonates include dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), etc.

[0076] <<Separator>> Suitable separators include, for example, microporous membranes such as polyethylene (PE) and polypropylene (PP). The separator may have a single-layer structure of PE, or a three-layer structure in which a PP membrane, a PE membrane, and a PP membrane are laminated in that order. The thickness of the separator may be, for example, about 9 to 30 μm. If the separator has the above-mentioned three-layer structure, the thickness of the PE layer may be, for example, about 3 to 10 μm, and the thickness of the PP layer may be, for example, about 3 to 10 μm. The pore size and porosity of the separator can be adjusted as appropriate so that the air permeability reaches the desired value. The separator may also be made of multiple microporous films stacked together, or it may have a heat-resistant layer formed on its surface containing an inorganic filler and a binder. The inorganic filler in the heat-resistant layer may be, for example, alumina, boehmite, titania, zirconia, magnesia, etc. The binder in the heat-resistant layer may be, for example, PVdF, aramid, SBR, PTFE, etc. The amount of binder in the heat-resistant layer may be 2 to 30% by mass, and the thickness of the heat-resistant layer may be, for example, about 3 to 10 μm. [Examples]

[0077] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The methods for measuring various physical properties are as follows:

[0078] <<density>> The density of the resin was determined in accordance with JIS K 7112 (water displacement method). The density values ​​for the metals are general values.

[0079] <<Manufacturing Examples 1-6>> According to the raw material mixing ratios shown in Table 1, the thermoplastic resin, additive masterbatch, and fiber masterbatch were dry-blended and melt-kneaded in a 180t injection molding machine manufactured by Japan Steel Works, Ltd. (JSW) to prepare a fiber-reinforced resin layer composition, and flat test pieces (2 mm thick, 150 mm square) were molded. The molding conditions were as follows: barrel temperature 220-250°C, injection speed 10-100 mm / s, back pressure 2-5 MPa, and mold temperature 60-100°C.

[0080] <<Manufacturing Examples 7 and 8>> As flat test specimens, we prepared iron or aluminum plates that were 2 mm thick and 150 mm square.

[0081] [Table 1]

[0082] In Table 1, "PP" represents polypropylene resin, "CF" represents carbon fiber, and "GF" represents glass fiber. In Table 1, the thermoplastic resin "PP" used as a raw material is propylene homopolymer: (MFR 30g / 10 min: compliant with ASTM D1238, 230℃, 2.16kg).

[0083] • Additive Masterbatch: Brand name MB32B (Manufacturer: JLS Co.), Phosphorus-based flame retardant (Melamine polyphosphate: 39% by mass, Polyphosphoric acid salt, compound: 36% by mass): 75% by mass, PP: 25% by mass • Fiber masterbatch: Composition (mass%) shown in Table 2 below

[0084] [Table 2]

[0085] [GF: Glass Fiber] The following glass rovings from Central Fiberglass were used. Model number: ERS1150-820; Fiber diameter = 16 μm, Basis weight = 1150 g / 1000 m [CF: Carbon Fiber (CF)] We used a product manufactured by Toray Industries, Inc., model number: T700. [PP: Polypropylene resin (PP)] Propylene homopolymer (MFR 220g / 10 min: compliant with ASTM D1238, 230℃, 2.16kg) [Acid-modified PP: Acid-modified polypropylene] Polypropylene (manufactured by Prime Polymer, Inc.), propylene homopolymer (MFR (230℃, 2.16 kg) = 15 g / 10 min) per 100 parts by mass, dialkyl peroxide ( One part by mass of Perhexa® 25B (manufactured by NOF Corporation) and three parts by mass of powdered maleic anhydride (manufactured by NOF Corporation, CRYSTAL MAN®) were pre-mixed. This mixture was fed into a 30 mmφ twin-screw extruder heated to 190°C and melt-kneaded at 200 rpm. The resulting strand was cooled in a water bath to obtain maleic anhydride-modified polypropylene. To remove unmodified residual maleic anhydride, this maleic anhydride-modified polypropylene was vacuum-dried at 40°C for 2 hours. The maleic acid content of the obtained maleic anhydride-modified polypropylene was 2.5% by mass, and the MFR (230°C, 2.16 kg) was 800 g / 10 min. [PA12: Polyamide resin] We used a Ube Industries, Ltd. model number 3012U.

[0086] <<Method for preparing a fiber masterbatch>> A resin mixture of polypropylene resin (PP), polyamide 12 (PA12), and acid-modified polypropylene (acid-modified PP) was mixed in the proportions shown in Table 2 and molten in an extruder. This molten material was then used to impregnate fibers (GF or CF) inserted into an impregnation die to produce resin-impregnated fibers. These resin-impregnated fibers were then cooled and cut with a pelletizer to produce a masterbatch.

[0087] (Examples 1-6 and Comparative Examples 7 and 8) For the "fiber-reinforced resin layer," flat test pieces or metal plates prepared in manufacturing examples 1 to 6 above were cut to a thickness of 2 mm and a size of 150 mm square. When an "expanded graphite layer" was to be provided, Fiblock (product name, 2 mm thick), described later, was cut to a size of 150 mm square with scissors, and the "fiber-reinforced resin layer" and the "expanded graphite layer" were bonded together to create an evaluation test piece (4 mm thick, 150 mm x 150 mm). Note that Fiblock (product name) is self-adhesive and can therefore be attached.

[0088] (Comparative Examples 1-6) As the "fiber-reinforced resin layer," the flat test pieces prepared in manufacturing examples 1 to 6 above were cut to a thickness of 2 mm and a size of 150 mm square to be used as evaluation test pieces.

[0089] <<Rating>> The evaluation specimens prepared as described above were used to perform the following evaluations. The results are shown in Table 3.

[0090] [Flame retardancy: UL94 5V test] A combustion test was conducted using the flat plate test specimen described above, in accordance with the UL94 5V standard. The center of the expanded graphite layer of the evaluation specimen was exposed to flame, and it was checked whether a hole was created. In comparative examples 1-6, which lacked an expanded graphite layer, the center of the evaluation test piece (fiber-reinforced resin layer) was exposed to flame to check for any holes. If no holes appeared, it was considered a pass (OK); if holes appeared, it was considered a fail (NG).

[0091] [Flame retardancy: Burner test] A burner test, a more stringent method for evaluating flame retardancy than the above test, was further conducted. The burner flame was applied to the expanded graphite layer or the fiber-reinforced resin layer, and the expanded graphite layer and / or fiber-reinforced resin layer were observed 5 minutes after the start of flame application, and the flame retardancy was evaluated according to the following criteria. If, after 5 minutes from the start of flame application, the expanded graphite layer or the fiber-reinforced resin layer burns or develops holes, or if, although neither the expanded graphite layer nor the fiber-reinforced resin layer develops holes, deformation is observed in the fiber-reinforced resin layer and the amount of deformation in the direction of deformation is 2 mm or more, the sample is deemed to have failed (NG). If neither the expanded graphite layer nor the fiber-reinforced resin layer develops any deformation, or if deformation is observed in the fiber-reinforced resin layer, but the amount of deformation in the direction of deformation is less than 2 mm, the sample is deemed to have passed (OK).

[0092] [Lightweighting] The density of the fiber-reinforced resin layer was measured using the method described above, and the results are shown in Table 2.

[0093] [Table 3]

[0094] The ingredients listed in Table 3 are as follows: • Fiblock: Expanded graphite-containing butyl rubber sheet, 2mm thick, manufactured by Sekisui Chemical Co., Ltd.

[0095] As shown in Table 3, the battery cases for non-aqueous electrolyte secondary batteries according to the present invention in Examples 1 to 6 are lighter and have superior flame retardancy compared to the battery cases for non-aqueous electrolyte secondary batteries in Comparative Examples 1 to 8. Example 1, which contains carbon fiber, showed flame retardancy even in the burner test, which is a rigorous evaluation of flame retardancy. In Examples 3 to 6, which contain glass fiber, it is possible to show flame retardancy even in the burner test, which is a rigorous evaluation of flame retardancy, by using a flame retardant in combination.

Claims

1. It comprises an expanded graphite layer and a fiber-reinforced resin layer, The fiber-reinforced resin layer contains at least one of carbon fibers and glass fibers in an amount of 10% to 60% by mass relative to the total mass of the fiber-reinforced resin layer. Battery case for non-aqueous electrolyte rechargeable batteries.

2. The battery case for a non-aqueous electrolyte secondary battery according to claim 1, wherein the expanded graphite content in the expanded graphite layer is 50% by mass or more of the total mass of the expanded graphite layer.

3. The battery case for a non-aqueous electrolyte secondary battery according to claim 1, wherein the fiber-reinforced resin layer comprises a polypropylene resin or a polyamide resin.

4. The battery case for a non-aqueous electrolyte secondary battery according to claim 1, wherein the expanded graphite layer is arranged on the inside of the battery case.

5. The battery case for a non-aqueous electrolyte secondary battery according to claim 1, further comprising an electromagnetic wave shielding layer.

6. The battery case for a non-aqueous electrolyte secondary battery according to claim 1, wherein the fiber-reinforced resin layer contains an electromagnetic wave shielding filler.

7. A battery for a non-aqueous electrolyte secondary battery, comprising a battery case for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6.

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