Film for battery exterior body, battery exterior body, and secondary battery

Abstract

This film for a battery exterior body has a thickness of at least 10 μm and comprises a hot-melt tetrafluoroethylene-based polymer having at least 50 carbonyl group-containing groups per 106 main chain carbon atoms and having a fluorine content of 60 mass% to 75 mass%.

Description

Battery exterior film, battery exterior, and secondary battery

[0001] The present invention relates to a film for a battery exterior body, a battery exterior body, and a secondary battery.

[0002] It is known to use a combination of a metal layer and a resin layer as an exterior body (battery exterior body) for batteries such as lithium-ion secondary batteries. For example, heat resistance sufficient to withstand mounting on a substrate by reflow soldering and water resistance sufficient to prevent the penetration of moisture such as water vapor are required. Patent Document 1 discloses an exterior body made of a laminate film including a resin film layer containing a thermally adhesive resin having a melting point of 200°C or higher and a metal foil disposed within the resin film layer, and a solid-state battery equipped with the exterior body, in which at least a portion of the metal foil of the exterior body is exposed to form a contact portion with a positive electrode terminal or a negative electrode terminal, and another portion of the metal foil is exposed to form an extraction electrode portion. Meanwhile, Patent Document 2 discloses a heat-resistant resin layer to be combined with a metal layer, which has been subjected to corona discharge treatment or plasma discharge treatment and has an oxygen element ratio of a predetermined amount or more when the surface condition after heat treatment is measured with a scanning X-ray photoelectron spectroscopy analyzer, and which is said to have good adhesion to copper foil.

[0003] International Publication No. 2021 / 235451 Japanese Patent Application Laid-Open No. 2022-112028

[0004] Patent Document 1 lists polychlorotrifluoroethylene, polytetrafluoroethylene, polyphenylene sulfide, and polyamideimide as resins constituting the resin film layer. However, these resin films have difficulty balancing the adhesiveness to the metal layer with the physical properties required for battery packaging, such as chemical resistance, gas barrier properties, and the slipperiness and drawability of the resin film surface. The fluororesin film disclosed in Patent Document 2 exhibits adhesiveness to copper foil by surface modification using corona discharge treatment or plasma discharge treatment. However, surface modification of the fluororesin film by discharge treatment involves decomposition of the fluororesin near the film surface. Therefore, while initial adhesion to copper foil (lamination properties) tends to be improved, the long-term durability of the adhesion and the impact of this on the physical properties required for battery packaging tend to be significant. In other words, the relationship between the two is, so to speak, a trade-off. The inventors have discovered that when such a fluororesin film is used as a battery component, it is significantly susceptible to environmental changes, such as temperature changes associated with charging and discharging, and gas generation from the electrolyte solution or electrolyte. Furthermore, the present inventors have found that, since fluororesin is prone to linear expansion, an increase in the thickness of the fluororesin film also has a more pronounced effect on the physical properties.

[0005] The present inventors have discovered that, when applying a fluororesin film to a battery exterior, a film of a predetermined thickness made from a fluororesin that itself contains a predetermined amount or more of specific functional groups and has a fluorine content within a predetermined range has excellent chemical resistance and heat resistance, good adhesion to a metal layer, and excellent formability, such as the slipperiness and drawability, of the film surface, making it applicable to various battery exteriors. An object of the present invention is to provide a film for battery exteriors that has good adhesion to a metal layer and excellent formability, such as the slipperiness and drawability of the surface, and can be used to form a battery exterior member that has excellent chemical resistance, gas barrier properties, etc. Another object of the present invention is to provide a battery exterior including such a battery exterior film, and a secondary battery including such a battery exterior.

[0006] The present invention has the following aspects: <1> A carbonyl group-containing group is present at 10 carbon atoms in the main chain. ６<1> A film for battery outer casing, having a thickness of 10 μm or more, comprising a heat-meltable tetrafluoroethylene-based polymer having 50 or more carbon atoms per unit area and a fluorine content of 60% by mass or more and 75% by mass or less. <2> The film for battery outer casing of <1>, in which the heat-meltable tetrafluoroethylene-based polymer has an MFR of 10 g / 10 min or more and 60 g / 10 min or less. <3> The film for battery outer casing of <1> or <2>, in which the fluorine content is 60% by mass or more and 68% by mass or less. <4> The film for battery outer casing of any of <1> to <3>, in which the heat-meltable tetrafluoroethylene-based polymer is a copolymer containing tetrafluoroethylene units and ethylene units. <5> The film for battery outer casing of <1>, in which the number of carbonyl group-containing groups of the heat-meltable tetrafluoroethylene-based polymer is 10 ６<6> The film for a battery exterior according to any one of <1> to <5>, wherein the oxygen element ratio is less than 1.5 atomic % when the surface state of one or both sides of the film is measured by a scanning X-ray photoelectron spectroscopy analyzer (XPS / ESCA) after heat treatment at 180°C for 3 minutes. <7> A battery exterior comprising a soft metal layer and a film layer for a battery exterior according to any one of <1> to <6>. <8> The battery exterior according to <7>, wherein the film layer for a battery exterior is thicker than the soft metal layer. <9> The battery exterior according to <7> or <8>, wherein the soft metal constituting the soft metal layer is aluminum. <10> The battery exterior according to any one of <7> to <9>, wherein the film layer for a battery exterior, the soft metal layer, and the film layer for a battery exterior are arranged in this order. <11> The battery exterior according to any one of <7> to <10>, further comprising a resin film layer made of at least one resin selected from the group consisting of polyethylene, polypropylene, polyimide, polyamide, liquid crystal polymer, polyphenylene sulfide, polyethylene terephthalate, polybutylene terephthalate, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, and polybutadiene. <12> The battery exterior according to any one of <7> to <11>, further comprising a resin film layer made of a heat-meltable tetrafluoroethylene-based polymer having no carbonyl group-containing group. <13> The battery exterior according to <11> or <12>, wherein the battery exterior film layer is in contact with one surface of the soft metal layer, and the resin film layer is in contact with the other surface of the soft metal layer. <14> The battery exterior according to any one of <7> to <13>, wherein the adhesive strength between the soft metal layer and the battery exterior film layer is 100 N / m or more. <15> A secondary battery comprising the battery outer casing of any one of <7> to <14> and an electrolyte, wherein the film layer for a battery outer casing is located in a position that contacts the electrolyte when the battery is assembled.

[0007] According to the present invention, it is possible to provide a film for battery exterior bodies, a battery exterior body, and a secondary battery having such a battery exterior body, which can form a battery exterior member having excellent chemical resistance, gas barrier properties, etc., and which has good adhesion to a metal layer and excellent formability such as surface slipperiness and drawability.

[0008] 1 is a perspective view showing an example of a battery exterior body provided with a film layer for a battery exterior body of the present invention.

[0009] The following terms have the following meanings. The "melt flow rate (MFR) of a hot-melt tetrafluoroethylene-based polymer" is a value measured at 372°C under a 5 kg load in accordance with ASTM D3307. The "melting point of a polymer" is the temperature corresponding to the maximum value of the melting peak of the polymer measured by differential scanning calorimetry (DSC). The "glass transition temperature (Tg)" is a value measured by analyzing the polymer by dynamic mechanical analysis (DMA). The thickness of the film and metal layer is the average value of values ​​measured at five random locations at 25°C using a high-precision Digimatic Micrometer "MDH-25MB" manufactured by Mitutoyo Corporation. The "unit" in a polymer refers to an atomic group based on a monomer formed by polymerization of the monomer. The unit may be a unit formed directly by a polymerization reaction, or may be a unit in which a portion of the unit is converted into a different structure by processing the polymer. Hereinafter, a unit based on monomer a will also be referred to simply as a "monomer a unit."

[0010] In the present invention, the carbonyl group-containing group is a group having 10 carbon atoms in the main chain. ６The present invention relates to a battery exterior film (hereinafter also referred to as the "battery exterior film") having a thickness of 10 μm or greater, the film containing a heat-meltable tetrafluoroethylene-based polymer (hereinafter also referred to as the "F polymer") having 50 or more carbon atoms per unit area and a fluorine content of 60% to 75% by mass. The surface of the battery exterior film contains carbonyl-containing groups derived from the molecular structure of the F polymer itself, which is believed to facilitate the development of high adhesive properties. Furthermore, the fluorine content of the F polymer within a predetermined range is believed to reduce the surface tension of the battery exterior film while maintaining its chemical resistance and heat resistance, thereby improving its affinity with other substrates. As a result, a battery exterior comprising a soft metal layer and the battery exterior film, as described below, is believed to have excellent adhesive properties with the soft metal layer, as well as excellent barrier properties, surface slipperiness, drawability, and other moldability of the battery exterior. These properties are more likely to be developed significantly in a preferred embodiment of the battery exterior film, as described below.

[0011] The F polymer in the present invention is a heat-meltable polymer containing units (hereinafter also referred to as "TFE units") based on tetrafluoroethylene (hereinafter also referred to as "TFE"). Here, a heat-meltable polymer means a polymer that has a temperature at which the melt flow rate is 1 to 1000 g / 10 min under a load of 49 N. The melting point of the F polymer is preferably above 100°C, more preferably 180°C or higher, and even more preferably 200°C or higher. The melting point of the F polymer is preferably 325°C or lower, more preferably 320°C or lower. In this case, the present battery exterior body film is likely to have excellent heat resistance.

[0012] The glass transition temperature of the F polymer is preferably 50°C or higher, more preferably 75°C or higher. The glass transition temperature of the F polymer is preferably 150°C or lower, more preferably 125°C or lower. The fluorine content of the F polymer is 60% by mass or higher and 75% by mass or lower, preferably 60% by mass or higher and 68% by mass or lower. In this case, the above-mentioned mechanism of action is more easily manifested. The fluorine content of the F polymer is determined as the ratio of fluorine atoms to all monomer units constituting the F polymer. The surface tension of the F polymer is preferably 16 to 26 mN / m. The surface tension of the F polymer can be measured by placing a droplet of a mixture for wetting tension testing specified in JIS K 6768 (manufactured by Wako Pure Chemical Industries, Ltd.) on a flat plate made of the F polymer.

[0013] Examples of F polymers include copolymers containing TFE units and units based on ethylene (ethylene units) [ETFE], copolymers containing TFE units and units based on propylene (propylene units), copolymers containing TFE units and units based on perfluoro(alkyl vinyl ether) (PAVE) (PAVE units) [PFA], copolymers containing TFE units and units based on hexafluoropropylene (HFP) (HFP units) [FEP], and copolymers containing TFE / ethylene units. Examples of the copolymer include an ethylene / HFP copolymer, a copolymer containing ethylene units and units based on chlorotrifluoroethylene (CTFE) (CTFE units) [ECTFE], a copolymer containing CTFE units and TFE units, a copolymer containing TFE units and units based on vinylidene fluoride (VdF) (VdF units) [VT], a copolymer containing TFE units, VdF units and CTFE units [VTC], and a copolymer containing TFE units, HFP units and VdF units.

[0014] Among them, F polymer is preferably one or more copolymers containing TFE unit and one or more units selected from the group consisting of PAVE unit, HFP unit, unit based on fluoroalkylethylene (FAE) (FAE unit) and ethylene unit.More specifically, F polymer is preferably the copolymer [ETFE] containing TFE unit and ethylene unit, the copolymer [FEP] containing TFE unit and HFP unit, the copolymer [PFA] containing TFE unit and PAVE unit, and more preferably ETFE.These copolymers may further contain units based on other comonomers.PAVE is preferably CF ２ = CFOCF ３ , C.F. ２ = CFOCF ２ CF ３ and CF ２ = CFOCF ２ CF ２ CF ３ (hereinafter also referred to as "PPVE") is preferred, and PPVE is more preferred. ２ =CH(CF ２ ) ２ F, CH ２ =CH(CF ２ ) ３ F, CH ２ =CH(CF ２ ) ４ F, CH ２ =CF(CF ２ ) ３ H and CH ２ =CF(CF ２ ) ４ H is preferred.

[0015] ETFE preferably contains 35 to 65 mol% of TFE units and 35 to 65 mol% of ethylene units, in that order, based on the total units. ETFE may further contain other units such as PAVE units, HFP units, and FAE units.

[0016] The F polymer has a carbonyl group-containing group at 10 carbon atoms in the main chain. ６ The number of carbonyl-containing groups in the F polymer is 10 main chain carbon atoms or more. ６The number of carbonyl group-containing groups in the F polymer is preferably 100 or more, and more preferably 200 or more, per unit area. ６ The number of oxygen-containing polar groups per unit area is preferably 5,000 or less, and more preferably 3,000 or less. The number of oxygen-containing polar groups in the F polymer can be quantified by the polymer composition or the method described in WO 2020 / 145133. When the F polymer has carbonyl group-containing groups within the above range, the film for the battery exterior body has excellent adhesion to the soft metal layer, and the battery exterior body comprising the soft metal layer and the film layer for the battery exterior body, as described below, has excellent barrier properties and formability such as surface slipperiness and drawability. Furthermore, it is easy to obtain a film for the battery exterior body that has excellent mechanical properties, heat resistance, and surface properties, as well as a small dimensional change rate. The carbonyl group-containing group is a carboxyl group, an alkoxycarbonyl group, an amide group, an isocyanate group, a carbamate group (-OC(O)NH ２ ), acid anhydride residue (-C(O)OC(O)-), imide residue (-C(O)NHC(O)-, etc.), formyl group, halogenoformyl group, urethane group (-NHC(O)O-), carbamoyl group (-C(O)-NH ２ ), ureido group (-NH-C(O)-NH ２ ), an oxamoyl group (—NH—C(O)—C(O)—NH ２ ) and carbonate group (—OC(O)O—), and acid anhydride residues are more preferred.

[0017] The carbonyl group-containing group may be contained in a unit derived from a monomer in the F polymer, or may be contained in a terminal group of the main chain of the F polymer. The latter embodiment includes an F polymer having a carbonyl group-containing group as a terminal group derived from a polymerization initiator, a chain transfer agent, etc. The monomer having a carbonyl group-containing group is preferably itaconic anhydride, citraconic anhydride, or 5-norbornene-2,3-dicarboxylic anhydride (hereinafter also referred to as "NAH"), and more preferably NAH.

[0018] The F polymer is preferably a copolymer containing TFE units and ethylene units and having a carbonyl group-containing group. Such ETFE includes polymers containing TFE units, ethylene units, and units based on a monomer having a carbonyl group-containing group, and containing these units in the following order, based on the total units. Specific examples of such ETFE include the polymers described in WO 2006 / 134764 and JP 2012-106494 A.

[0019] The MFR of the F polymer contained in the present battery exterior body film is preferably more than 10 g / 10 min and not more than 60 g / 10 min, more preferably 15 g / 10 min or more and 50 g / 10 min or less. When the MFR is within this range, the present battery exterior body film is likely to exhibit properties such as chemical resistance and heat resistance based on the F polymer while ensuring flexibility. In the present battery exterior body film, one type of F polymer may be used alone, or two or more types may be used in combination.

[0020] The F polymer may contain other components than the F polymer, as long as the effects of the present invention are not impaired. Examples of other components include known resin additives and other hot-melt heat-resistant resins other than the F polymer, such as polyimide and polyether ether ketone.

[0021] When the surface condition of one or both sides of the present battery outer casing film is measured using a scanning X-ray photoelectron spectroscopy (XPS / ESCA) after heat treatment at 180°C for 3 minutes, the oxygen element ratio is preferably less than 1.5 atomic%, more preferably 1.0 atomic% or less. The oxygen element ratio is preferably 0.1 atomic% or more. In this case, the chemical resistance and gas barrier properties of the present battery outer casing film are likely to be improved. Furthermore, even when the oxygen element ratio is within the above range, the F polymer contained in the present battery outer casing film tends to have excellent surface properties and excellent adhesion to the soft metal layer. The oxygen atomic ratio is a value obtained by placing a test piece for XPS / ESCA measurement made from the present battery outer casing film on a metal tray, heat-treating it in an electric furnace at 180°C for 3 minutes in an air atmosphere, and then measuring the surface condition of one or both sides using XPS / ESCA.

[0022] Furthermore, the absolute value of the dimensional change rate of the present battery exterior film before and after the heat treatment, measured after heat treatment at 180° C. for 10 minutes and then cooling to 25° C., is preferably 2% or less, and more preferably 1.8% or less. The dimensional change rate is a value calculated from the change in the gauge intervals before and after the heat treatment, by cutting a 300 mm square test piece from the present battery exterior film, marking it with gauge marks at 180 mm intervals, heat treating it in an electric furnace in an air atmosphere at 180° C. for 10 minutes without applying a load, and then cooling it to 25° C., measuring the gauge intervals in the longitudinal and transverse directions of the test piece.

[0023] The present film for battery exterior packaging can be formed, for example, by melt-extruding the F polymer using an extruder having a T-die. The melt-extrusion of the F polymer may be carried out continuously after melt-kneading the F polymer, or may be carried out while melt-kneading in the extruder. Furthermore, after melt-extrusion, the F polymer may be uniaxially or biaxially stretched, or may not be stretched. The melt-extrusion conditions are usually preferably set to a temperature 20°C or higher than the melting point of the F polymer. The thickness of the present film for battery exterior packaging can be controlled by appropriately adjusting the clearance of the T-die, the take-up speed, the amount of F polymer applied, and the like. The present film for battery exterior packaging can also be obtained by preparing a solution or dispersion containing the F polymer, applying it to a substrate, heating it, and then separating it from the substrate.

[0024] The thickness of the film for a battery exterior body is 10 μm or more, and is preferably 60 μm or less, more preferably 50 μm or less, from the viewpoint of easily achieving excellent formability, such as the slipperiness and drawability, of the battery exterior body of the present invention described below, while ensuring properties such as chemical resistance and heat resistance. Furthermore, the total thickness of the battery exterior body of the present invention described below, which includes the soft metal layer and the film layer for a battery exterior body, is preferably 50 μm or more and 200 μm or less, more preferably 60 μm or more and 150 μm or less, and even more preferably 70 μm or more and 125 μm or less. Due to the above-described mechanism of action, when the thickness of the film for a battery exterior body is within the above range, the battery exterior body is more excellent in chemical resistance and heat resistance, and, in combination with the soft metal layer, is easily able to achieve excellent formability, such as slipperiness and drawability.

[0025] This battery exterior film has excellent barrier properties and heat resistance, making it suitable for use as an exterior for a variety of batteries. Examples of batteries include all-solid-state batteries such as sulfide-based, oxide-based, and all-resin batteries; semi-solid batteries such as gel polymer-type semi-solid batteries, clay-type semi-solid batteries, liquid-added semi-solid batteries, and aggregate-state batteries; lithium-ion batteries such as lithium-sulfur batteries (Li-S batteries), lithium manganese iron phosphate batteries (LMFP batteries), and lithium iron phosphate ion batteries (e.g., the "M3P battery" manufactured by Contemporary Amperex Technology Co., Ltd.); and solar cells. This battery exterior film can also be used for components such as tab leads and separators in the various batteries mentioned above.

[0026] The present invention also provides a battery exterior (hereinafter also referred to as "the battery exterior") comprising a soft metal layer and a film layer for the battery exterior. The battery exterior has excellent barrier properties due to the soft metal layer, and excellent heat resistance due to the film layer for the battery exterior, which has excellent adhesion to the soft metal layer, and peeling of the fluororesin-containing layer from the metal layer is suppressed even when the laminate is heated. Because the battery exterior has these properties, when used as an exterior for various secondary batteries, it tends to have excellent barrier properties and heat resistance even after repeated charge and discharge, and to maintain battery characteristics such as charge and discharge capacity.

[0027] In the present battery exterior, the soft metal layer may be a foil-shaped or plate-shaped soft metal, and a soft metal foil is more preferred. Examples of the soft metal constituting the soft metal support include at least one selected from the group consisting of aluminum, stainless steel, and copper. Aluminum is preferred as the soft metal from the viewpoint of further improving the mechanical properties, barrier properties, and chemical resistance (corrosion resistance) of the present swing member film. Aluminum may be a simple metal or an alloy. In the latter case, an aluminum alloy with an aluminum content of 80% by mass or more is preferred. In other words, it is more preferred that the soft metal support be aluminum foil.

[0028] In the present battery exterior body, the adhesive strength between the soft metal layer and the film layer for the present battery exterior body is preferably 100 N / m or more. The upper limit of the adhesive strength is 1000 N / m. When the adhesive strength is within the above range, the heat resistance of the present battery exterior body and formability such as surface slipperiness and drawability are likely to be further improved. The adhesive strength between the soft metal layer and the film layer for the present battery exterior body is a value obtained by measuring the peel strength as described in the examples below.

[0029] The water vapor permeability of the soft metal layer is 1 g / m ２ ・day or less is preferable, 0.1 g / m ２ ・day or less is more preferable, 0.01 g / m ２The water vapor permeability is measured using a differential pressure gas / water vapor permeability tester (GC method) at 40°C and 90% RH in accordance with JIS K7129-1:2019. The oxygen permeability of the soft metal layer is 1 g ml / m or less. ２ ·day·atm or less is preferable, and 0.1 g·ml / m ２ ·day·atm or less is more preferable, and 0.01 g·ml / m ２ The oxygen permeability is measured at 23°C using a differential pressure gas / water vapor permeation tester (GC method) in accordance with JIS K7126-2:2006. The surface of the soft metal layer may be surface-treated.

[0030] The thickness of the soft metal layer is preferably 10 μm to 60 μm, and more preferably 15 μm to 50 μm, from the viewpoint of improving the mechanical properties of the battery exterior and further improving formability such as barrier properties, chemical resistance (corrosion resistance), slipperiness, and drawability. Furthermore, from the viewpoint of improving the chemical resistance, heat resistance, and the like of the battery exterior and further improving formability such as slipperiness and drawability, the thickness of the soft metal layer is preferably in the range of more than 25% to 200% of the thickness of the film layer for the battery exterior, and more preferably the film layer for the battery exterior is thicker than the soft metal layer. The thickness of the soft metal layer is more preferably 40% to 150% of the thickness of the film layer for the battery exterior. When the battery exterior is configured to include multiple film layers for the battery exterior, the total thickness of the film layers for the battery exterior is defined as the thickness of the film layer for the battery exterior.

[0031] The battery outer casing may further include a resin film layer (hereinafter also referred to as "resin film layer A") made of at least one resin selected from the group consisting of polyethylene, polypropylene, polyimide, polyamide, liquid crystal polymer, polyphenylene sulfide, polyethylene terephthalate, polybutylene terephthalate, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, and polybutadiene.

[0032] The battery outer casing may further include a resin film layer (hereinafter also referred to as "resin film layer B") made of a heat-fusible tetrafluoroethylene-based polymer that does not have a carbonyl group-containing group. The heat-fusible tetrafluoroethylene-based polymer that does not have a carbonyl group-containing group is a polymer having a carbonyl group-containing group content of 10 carbon atoms in the main chain. ６ Examples of such copolymers include copolymers having ethylene units and TFE units (ETFE), copolymers containing TFE units and PAVE units (PFA), polymers having vinylidene fluoride units (PVDF), and polymers having vinyl fluoride units (PVF), each of which has less than 50 units per unit.

[0033] When the battery outer casing has either or both of the resin film layer A and the resin film layer B, the thicknesses of the resin film A and the resin film B are not limited as long as the effects of the present invention are not impaired, and are typically preferably in the range of 1 to 50 μm. The resin film layer A and the resin film layer B may further contain other components such as various additives and inorganic fillers, as long as the effects of the present invention are not impaired. Furthermore, each resin film layer may be in contact with the soft metal layer via an adhesive layer.

[0034] The battery exterior preferably has a configuration in which a film layer for the battery exterior is in contact with one surface of the soft metal layer. The battery exterior more preferably has a configuration in which a film layer for the battery exterior, a soft metal layer, and a film layer for the battery exterior are in this order, and even more preferably has a configuration in which film layers for the battery exterior are in contact with both surfaces of the soft metal layer. In this case, the film layers for the battery exterior in contact with both surfaces of the soft metal layer may be battery exterior films containing the same type of F polymer, or may be two types of battery exterior films containing different F polymers.

[0035] When the battery exterior further includes one or both of the resin film layer A and the resin film layer B, the resin film layer is preferably configured to be in contact with one side of the soft metal layer, or in contact with the side of the battery exterior film layer that is in contact with one or both sides of the soft metal layer, opposite the soft metal layer. When the battery exterior film layer is in contact with both sides of the soft metal layer, the resin film layer may be configured to be present on the outside of one of the battery exterior film layers that is in contact with the soft metal layer, or on the outside of both of the battery exterior film layers. When there are multiple resin film layers, the types of the resin film layers may be the same or different. More preferably, the battery exterior is configured such that the battery exterior film layer is in contact with one side of the soft metal layer, and the resin film layer (resin film layer A or resin film layer B) is in contact with the other side of the soft metal layer. In this case, it is preferable to configure the battery so that the battery exterior film layer side of the battery exterior is in contact with the electrolyte, from the viewpoint of maximizing the chemical resistance, heat resistance, and barrier properties of the battery exterior.

[0036] The battery exterior can be obtained, for example, by a method of heat-pressing a soft metal layer, the battery exterior film, and, if necessary, a resin film layer (thermal lamination method). Alternatively, the battery exterior can be obtained by a method of preliminarily preparing a laminate consisting of the battery exterior film and a resin film (resin film A or resin film B) by a thermal lamination method or the like, and then heat-pressing a soft metal layer onto the surface of the laminate facing the battery exterior film.

[0037] The present battery outer casing can be used for battery packaging without any particular limitations, and may be, for example, a bag-shaped battery outer casing (hereinafter also referred to as a "battery pouch"). A battery pouch using the present battery outer casing can be obtained, for example, by heat-sealing a portion of the periphery of one or more present battery outer casings to form a pouch. Examples of the battery pouch include a three-sided sealed pouch in which one present battery outer casing is folded back and overlapped, and the first layers of the overlapping edges of the three overlapping edges are heat-sealed together; and a four-sided sealed pouch in which two present battery outer casings are overlapped and the first layers of the overlapping edges of the four overlapping edges are heat-sealed together. Such a battery pouch has excellent barrier properties and heat resistance, and even in high-temperature environments, it suppresses interfacial peeling between the seals and the layers of the battery pouch. These battery pouches can be used for the various batteries described above and are applicable to battery cells of various shapes, such as laminated, pouch, cylindrical, and rectangular.

[0038] FIG. 1 shows an example of an all-solid-state battery in which the exterior of an all-solid-state battery cell is formed using the present battery exterior. The all-solid-state battery 40 includes an all-solid-state battery cell 42 and a present battery exterior 10 that exteriorizes the all-solid-state battery cell 42. The bag 30 is a three-sided sealed bag formed by folding the present battery exterior 10 midway and overlapping it, and then heat-sealing the edges of the overlapping three sides to form a three-sided seal 32. A positive electrode terminal 44 and a negative electrode terminal 46 protruding from the exterior formed by the present battery exterior 10 are sealed while sandwiched between two sheets of the present battery exterior 10. Because the all-solid-state battery configured in this manner is exteriorized with the present battery exterior, it has excellent barrier properties and heat resistance, and is less likely to peel at the seals of the exterior laminate and at the interfaces between the layers of the laminate when exposed to high temperatures. Therefore, the decrease in charge / discharge capacity when exposed to high temperatures is more suppressed than before.

[0039] The present invention also provides a secondary battery having the present battery exterior and an electrolyte, wherein the film layer for the present battery exterior in the present battery exterior is located in a position that contacts the electrolyte when the battery is assembled. This configuration provides the battery exterior with excellent chemical resistance, heat resistance, etc., against the electrolyte, and also excellent barrier properties. Examples of secondary batteries include the various batteries described above, and the electrolyte may be liquid or solid.

[0040] Although the present battery exterior film and the battery exterior formed from the present battery exterior film have been described above, the present invention is not limited to the configurations of the above-described embodiments. For example, the present battery exterior film and the battery exterior formed from the present battery exterior film may have any other configuration added to the configurations of the above-described embodiments, or may be replaced with any configuration that exhibits the same function.

[0041] The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. Preparation of each component [Film of heat-meltable tetrafluoroethylene-based polymer (F polymer)] F film 1: TFE unit, ethylene unit, CH ２ =CH(CF ２ ) ２ The copolymer contains 58.0 mol %, 38.6 mol %, 3.1 mol %, and 0.3 mol % of F-based units and NAH units, respectively, and has a carbonyl group-containing group between 10 main chain carbon atoms. ６ Film (thickness: 25 μm, oxygen atom ratio: 0.8 atomic%) of ETFE (fluorine content: 64 mass%, MFR: 27.0 g / 10 min, melting point 237° C.) having 3000 units per unit. F Film 2: A film containing 97.9 mol%, 2.0 mol%, and 0.1 mol% of TFE units, PPVE units, and NAH units, in this order, and having a carbonyl group-containing group with a main chain carbon number of 1×10 ６ F Film 3: A film (thickness: 25 μm, oxygen atom ratio: 0.5 atomic%) of PFA (fluorine content: 75 mass%, MFR: 11.0 g / 10 min, melting temperature: 300° C.) having 1,000 units per unit. F Film 4: A film (thickness: 25 μm, oxygen atom ratio: 0.5 atomic%) of PFA containing TFE units and PPVE units, in which the number of carbon atoms in the main chain of the carbonyl group-containing group is 1×10 ６ PFA film (fluorine content: 75% by mass, melting temperature: 305°C) with less than 10 particles per film (thickness: 25 μm, oxygen atomic ratio: less than 0.1 atomic%). F film 4: While nitrogen gas containing 0.50% by volume of vinyl acetate was flowed near the discharge electrode and roll-shaped ground electrode of a corona discharge device, F film 3 was continuously passed along the roll-shaped ground electrode, and a discharge amount of 1000 W·min / m was obtained. ２F film (thickness: 25 μm, oxygen atomic ratio: 10 atomic%) that had been subjected to the above corona discharge treatment. F film 5: a film (thickness: 25 μm) of PVDF (fluorine content: 59 mass%), which is a homopolymer of vinylidene fluoride. Note that F film 1 and F film 2 correspond to the battery exterior film of the present invention. [Soft metal layer] Metal layer 1: aluminum alloy foil (aluminum alloy foil based on JIS H 4160:1994, alloy part number 8079, thickness: 40 μm, length: 30 cm, width: 30 cm)

[0042] 2. Preparation of Battery Exterior Body Example 1 F film 1 was laminated on both sides of metal layer 1, and release films (polyimide film "Kapton (registered trademark) 200H / V" manufactured by DuPont-Toray Co., Ltd., thickness 50 μm) were laminated on the outer sides of both sides. This laminate was pressed using a vacuum press under conditions of 240°C, 15 minutes, and 10 MPa, then removed and left to cool in a 25°C atmosphere for 5 minutes. After cooling, the release films on both sides were peeled off to obtain battery exterior body 1.

[0043] Example 2 An F film 2 was laminated on both sides of a metal layer 1, and release films similar to those in Example 1 were further laminated on the outer sides of both sides. This laminate was pressed using a vacuum press under conditions of 305°C, 1 MPa for 15 minutes, and then removed and allowed to cool in an atmosphere of 25°C for 5 minutes. After cooling, the release films on both sides were peeled off to obtain a battery exterior body 2.

[0044] Example 3 An F film 3 was laminated on both sides of a metal layer 1, and release films similar to those in Example 1 were further disposed and laminated on the outer sides of both sides. This laminate was pressed under the same conditions as in Example 2, then removed and allowed to cool in an atmosphere of 25°C for 5 minutes. After cooling, the release films on both sides were peeled off to obtain a battery exterior body 3.

[0045] Example 4 An F film 4 was laminated on both sides of a metal layer 1, and release films similar to those in Example 1 were further disposed and laminated on the outer sides of both sides. This laminate was pressed under the same conditions as in Example 2, then removed and allowed to cool in an atmosphere of 25°C for 5 minutes. After cooling, the release films on both sides were peeled off to obtain a battery exterior body 4.

[0046] Example 5 An F film 5 was laminated on both sides of a metal layer 1, and release films similar to those in Example 1 were further disposed and laminated on the outer sides of both of the F films. This laminate was pressed under the same conditions as in Example 1, then removed and allowed to cool in an atmosphere of 25°C for 5 minutes. After cooling, the release films on both sides were peeled off to obtain a battery exterior body 5.

[0047] 3. Evaluation of Battery Exterior Body 3-1. Adhesion (Durability to Hydrogen Sulfide Gas) The battery exterior body prepared in each example was placed between the upper and lower parts of a separable flask equipped with vents at the top and bottom, and allowed to stand for 48 hours under an environment of 23±5°C. Nitrogen gas was passed through the upper vent at a rate of 50 ml / min, and nitrogen gas with a hydrogen sulfide gas concentration of 20±5 ppm was passed through the lower vent at a rate of 50 ml / min. The battery exterior body was then removed and cut to a width of 1 cm. The battery exterior body film layer on the side exposed to nitrogen gas containing hydrogen sulfide and the aluminum layer were peeled from one end in the longitudinal direction to a position 50 mm, and then peeled at 90° using a tensile tester at 25°C and a pulling rate of 100 mm / min. The average load measured from a measurement distance of 20 mm to 80 mm was taken as the peel strength (N / cm), and the peel strength of battery exterior body 1 after exposure to nitrogen gas containing hydrogen sulfide was taken as 100. Adhesion was evaluated by assigning a "good" to battery exterior bodies 2 to 4 when the relative value of the peel strength after exposure to hydrogen sulfide was 100 or more, a "fair" to battery exterior bodies 2 to 4 when the relative value was 75 or more but less than 100, and an "unacceptable" to battery exterior body 3 when the relative value was less than 75. Note that the peel strength of battery exterior body 3, measured in the same manner using a tensile tester before exposure to nitrogen gas containing hydrogen sulfide, was in the "unacceptable" range, and therefore adhesion evaluation was not performed.

[0048] 3-2. Sliding Property and Drawability The battery exterior bodies used for the evaluation of "3-1. Adhesion" were further subjected to one-stage deep drawing using a straight forming die with a forming depth of 5 mm [made of carbon steel (only the punch radius was chrome-plated), punch: 33.3 mm x 53.9 mm, die: 80 mm x 120 mm, corner radius: 2 mm, punch radius: 1.3 mm, die radius: 1 mm] at a calculated blank holding pressure of 0.7 MPa, and the formed bodies were visually inspected for whitening and cracks. Cases where neither whitening nor cracks were observed during forming were rated "Good," cases where whitening was observed in the formed body were rated "Fair," and cases where cracks were observed in the formed body were rated "Poor." Note that Battery Exterior Body 5 was not evaluated for sliding property and drawability because the above-described adhesion evaluation did not yield satisfactory results. The evaluation results are shown in Table 1.

[0049]

[0050] The disclosures of Japanese Patent Applications Nos. 2023-120103, 2023-194606, and 2024-034259 are incorporated herein by reference in their entirety. All documents, patent applications, and technical standards in this disclosure are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

[0051] 10 Battery outer casing 30 Bag body 32 Sealing portion 40 All-solid-state battery 42 All-solid-state battery cell 44 Positive electrode terminal 46 Negative electrode terminal

Claims

1. A carbonyl-containing group is attached to 10 carbon atoms of the main chain. ６ A film for battery exteriors, comprising a heat-fusible tetrafluoroethylene-based polymer having a fluorine content of 60% by mass or more and 75% by mass or less, and having a thickness of 10 μm or more.

2. The film for battery exterior packaging according to claim 1, wherein the MFR of the heat-meltable tetrafluoroethylene polymer is 10 g / 10 min or more and 60 g / 10 min or less.

3. The film for battery exterior packaging according to claim 1, wherein the fluorine content is from 60% by mass to 68% by mass.

4. The film for battery exterior packaging according to claim 1, wherein the heat-fusible tetrafluoroethylene polymer is a copolymer containing tetrafluoroethylene units and ethylene units.

5. The number of the carbonyl group-containing groups of the heat-fusible tetrafluoroethylene polymer is 10 or less. ６ The film for battery exterior bodies according to claim 1 , wherein the number of particles per unit area is 200 or more.

6. A film for battery exterior packaging as described in claim 1, in which the oxygen element ratio is less than 1.5 atomic % when the surface condition of one or both sides is measured by a scanning X-ray photoelectron spectroscopy / chemical analysis (XPS / ESCA) after heat treatment at 180°C for 3 minutes.

7. A battery exterior body comprising a soft metal layer and the film layer for battery exterior bodies according to any one of claims 1 to 6.

8. The battery exterior body according to claim 7, wherein the thickness of the film layer for a battery exterior body is greater than the thickness of the soft metal layer.

9. The battery exterior body according to claim 7, wherein the soft metal is aluminum.

10. A battery exterior body as described in claim 7, comprising, in this order, the film layer for a battery exterior body, the soft metal layer, and the film layer for a battery exterior body.

11. The battery outer casing according to claim 7, further comprising a resin film layer made of at least one resin selected from the group consisting of polyethylene, polypropylene, polyimide, polyamide, liquid crystal polymer, polyphenylene sulfide, polyethylene terephthalate, polybutylene terephthalate, cycloolefin polymer, polystyrene, epoxy resin, bismaleimide, polyphenylene oxide, polyphenylene ether, and polybutadiene.

12. The battery outer casing according to claim 7, further comprising a resin film layer made of a heat-fusible tetrafluoroethylene polymer having no carbonyl group-containing group.

13. A battery exterior according to claim 11 or 12, wherein the battery exterior film layer is in contact with one surface of the soft metal layer, and the resin film layer is in contact with the other surface of the soft metal layer.

14. The battery exterior body according to claim 7, wherein the adhesive strength between the soft metal layer and the film layer for battery exterior body is 100 N / m or more.

15. A secondary battery comprising the battery exterior body and an electrolyte as defined in claim 12, said film layer for battery exterior body being located in a position in contact with the electrolyte when the battery is assembled.

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