Packaging material for battery and case for battery

Abstract

To provide a packaging material for a battery which gradually lowers its seal strength accompanying temperature rise, and is gently opened.SOLUTION: A packaging material 1 for a battery includes a base material layer 13 as an outside layer, a sealant layer 20A as an inside layer, and a barrier layer 11 arranged between both of the layers. The sealant layer 20A is composed of one or more layers, and has a first sealant layer 21 arranged on the innermost side of the sealant layer 20A. A resin constituting the first sealant layer 21 contains a polybutene copolymer A containing at least one or more of a butene-ethylene copolymer, a butene-propylene copolymer and a copolymer of α-olefin having 5 or more carbon atoms and butene-1.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery packaging material and a battery case that are suitably used as cases for secondary batteries, for example, for in-vehicle, stationary, notebook computers, mobile phones, and cameras, in particular small, portable lithium ion secondary batteries. [Background technology]

[0002] Lithium-ion secondary batteries, as a representative example, can be made into various shapes by using laminate-type packaging materials in which resin layers are bonded to both sides of aluminum cans and cases, and they can also be made thinner and lighter. In a power storage device that uses a laminate material as a packaging material, when the temperature inside the battery rises as the capacity of the device increases, gas is generated due to the volatilization of the electrolyte, etc., and the internal pressure rises, causing the case to expand and, in some cases, to burst. In addition, if the gas is flammable, there is a risk of fire. For this reason, measures are taken in the case of the power storage device to prevent bursting and slowly release the gas (see Patent Documents 1 to 3).

[0003] For example, JIS C8714 (2007) "Safety test for lithium-ion batteries for portable electronic devices" is an example of a safety standard for preventing fire. In this safety test, the battery is heated from 5±2°C to 130°C±2°C and held for 10 minutes to ensure the safety of the battery by confirming that the battery does not ignite or explode. Batteries that pass the safety test are safe because the seal of the case does not peel off within the normal operating temperature range. On the other hand, when the battery is overheated, gas generated from the battery body increases the internal pressure of the case, but when the temperature exceeds a certain level, the seal peels off and the case is opened, allowing the gas to escape outside the case, preventing the case from exploding due to the increase in internal pressure.

[0004] The electricity storage device of Patent Document 1 takes preventive measures based on the structure of the case, and is equipped with a valve mechanism that reduces the pressure inside the case when the pressure increases, and an air passage that guides gas inside the case to the valve mechanism.

[0005] The above-mentioned Patent Documents 2 and 3 relate to a technology for opening the sealed portion of the case at high temperatures by defining the battery packaging material. Patent Document 2 discloses a technology for opening the case when exposed to a high-temperature environment of about 90°C to 120°C by defining the peak melting temperature of the heat-sealable resin layer (sealant layer). Patent Document 3 discloses a technology for opening the case at high temperatures by defining the heat seal strength between heat-sealable resin layers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6540871 [Patent Document 2] Patent No. 7019991 [Patent Document 3] WO 2021 / 201293 A1 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the preventive measures described in Patent Document 1 require additional components such as a valve mechanism and a vent path, which increases both material and manufacturing costs. Patent Documents 2 and 3 do not require additional components such as a valve device, but they have the problem that when exposed to high temperatures, the seal strength decreases, causing the seal to suddenly open, which can cause a large amount of gas to instantly erupt.

[0008] The present invention has been made in consideration of the above problems, and aims to provide a battery packaging material and a battery case in which the seal strength gradually decreases as the temperature increases, allowing the sealed portion to be opened gently. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention has the following means.

[0010] [1] A packaging material for a battery comprising a base material layer as an outer layer, a sealant layer as an inner layer, and a barrier layer disposed between these layers, The sealant layer is composed of one or more layers, and a first sealant layer is disposed on the innermost side of the sealant layer; A battery packaging material, characterized in that the resin constituting the first sealant layer includes a polybutene copolymer A containing at least one of a butene-ethylene copolymer, a butene-propylene copolymer, and a copolymer of an α-olefin having 5 or more carbon atoms and butene-1.

[0011] [2] The battery packaging material according to item 1, wherein the resin constituting the first sealant layer contains 30% by mass to 50% by mass of the polybutene copolymer A and 50% by mass to 70% by mass of a propylene random copolymer.

[0012] [3] The battery packaging material according to item 1 or 2 above, wherein the polybutene copolymer A has a melting point of 120° C. or lower.

[0013] [4] The sealant layer has a multilayer structure including the first sealant layer, a third sealant layer closest to the barrier layer, and a second sealant layer provided between the first and third sealant layers; 4. The battery packaging material according to any one of items 1 to 3 above, wherein the second sealant layer is a polypropylene-based resin containing a propylene block copolymer and a propylene random copolymer.

[0014] [5] The sealant layer has a multi-layer structure including the first sealant layer and a third sealant layer closest to the barrier layer; 5. The battery packaging material according to any one of items 1 to 4 above, wherein the third sealant layer contains a propylene random copolymer having a melting point higher than that of the first sealant layer.

[0015] [6] The packaging material for batteries according to any one of items 1 to 5, wherein when the sealant layers are heat-sealed together, the heat-sealed portion has a seal strength of 20 N / 15 mm width or more in an environment of 100°C.

[0016] [7] A battery case formed by heat-sealing the sealant layers of the battery packaging material according to any one of items 1 to 6 above, A battery case characterized in that the heat-sealed portion has a seal strength of 20 N / 15 mm width or more in an environment of 100°C. Effect of the Invention

[0017] According to the battery packaging material of the invention [1], the resin constituting the first sealant layer, which is the innermost layer of the sealant layers, contains polybutene copolymer A containing a butene-1 component, so that the side chains are bulkier than those of polypropylene or polyethylene, and steric hindrance has the effect of lowering the crystallinity of the resin, resulting in a lower melting point. Therefore, when the temperature of a battery case produced by heat-sealing the first sealant layers rises excessively, gas generated in the battery body inside the case accumulates and the internal pressure rises, the low melting point component softens due to the rise in temperature, the seal strength decreases, and the seal is gradually opened, so that the gas inside the battery case is efficiently released to the outside, and defects such as the rupture of the packaging material due to the rise in internal pressure of the battery case can be prevented.

[0018] According to the battery packaging material of invention [2], the content of polybutene copolymer A and the content of propylene random copolymer in the resin constituting the first sealant layer are specified within prescribed ranges. This prevents inadvertent peeling of the sealed portion at low temperatures, while at the same time allowing the sealed portion to be properly opened when the internal pressure increases due to overheating, so that the gas inside the battery case can be reliably released to the outside, thereby more reliably preventing defects such as rupture of the packaging material due to an increase in internal pressure of the battery case.

[0019] According to the battery packaging material of invention [3], the melting point of the polybutene copolymer A contained in the first sealant layer is 120°C or lower, making it easier to control the melting point of the first sealant layer, and the first sealant layers of the battery packaging material can be reliably fused to each other to produce a battery case, while also making it possible to more efficiently release gas from within the battery case in the event of excessive heating.

[0020] According to the battery packaging material of invention [4], since the second sealant layer contains a heat-resistant block copolymer, the second sealant layer remains in place during heat sealing when the battery case is produced, leaving a sufficient space (layer thickness). This ensures that insulation is maintained by the remaining second sealant layer, and ensures that only the first sealant layers are fused together. As a result, when the internal pressure increases due to excessive heating, the desired gas discharge function can be adequately exerted in the relatively low temperature range, making it possible to more reliably prevent malfunctions caused by increased internal pressure in the battery case.

[0021] According to the battery packaging material of the invention [5], since the third sealant layer has a higher melting point than the first sealant layer, the first sealant layers can be heat-sealed more reliably before the third sealant layer melts during sealing. Therefore, the remaining third sealant layer can maintain insulation more reliably, and only the first sealant layers can be fused more reliably, which further prevents defects caused by an increase in the internal pressure of the battery case. Furthermore, since the third sealant layer contains a propylene random copolymer, it has a small elastomer component and is less likely to generate voids, and has a small steric hindrance due to its structure, so that it has good adhesion with the adhesive layer. Even if liquid bite occurs during heat sealing, it is possible to prevent electrolyte erosion, and it is possible to prevent interfacial peeling between adhesive layers, for example, between the adhesive layer and the metal foil or between the adhesive layer and the sealant layer, and it is possible to increase the possibility of peeling occurring reliably between the first sealant layers during excessive heating, which also prevents defects caused by an increase in the internal pressure of the battery case.

[0022] According to the battery packaging material of invention [6] and the battery case of invention [7], the sealed portion can reliably maintain an appropriate sealed state until a predetermined overtemperature range is reached, and inadvertent peeling of the sealed portion at low temperatures can be prevented. [Brief description of the drawings]

[0023] [Figure 1] FIG. 1 is a cross-sectional view showing an example of the battery packaging material of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing another example of the battery packaging material of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view showing still another example of the battery packaging material of the present invention. [Figure 4] FIG. 4 is a cross-sectional view of a battery equipped with a battery case made from the battery packaging material of FIGS. [Diagram 5] FIG. 5 is an enlarged cross-sectional view showing a portion surrounded by a dashed line in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] 1 to 3 show three embodiments of the battery packaging material of the present invention.

[0025] In the following description, layers with the same reference numerals denote the same or equivalent parts, and duplicated descriptions will be omitted.

[0026] The battery packaging materials 1, 2, and 3 have a base material layer 13 bonded to one surface (outer surface) of a barrier layer 11 via a first adhesive layer 12, and sealant layers 20A, 20B, and 20C bonded to the other surface (inner surface) via a second adhesive layer 14.

[0027] 4 and 5, a battery case 50 using the battery packaging materials 1, 2, and 3 is produced by heat-sealing the periphery of the battery packaging materials 1, 2, and 3 with the sealant layers 20A, 20B, and 20C facing each other, and a bare cell (battery body) 51 is enclosed in the battery case 50. In the produced battery case 50, the base layer 13 is the outer layer, and the sealant layers 20A, 20B, and 20C are the inner layers. In the present invention, when describing the positions of the layers constituting the battery packaging materials 1, 2, and 3 in terms of directions, the direction of the base layer 13 is referred to as the outer side, and the direction of the sealant layers 20A, 20B, and 20C is referred to as the inner side.

[0028] (Configuration of sealant layer) The battery packaging material of the present invention is characterized by the material of the sealant layer that is the inner layer. The sealant layer provides excellent chemical resistance against highly corrosive electrolytes and the like, and also provides the battery packaging materials 1, 2, and 3 with heat sealability.

[0029] The sealant layer is composed of one or more layers and may be either a single layer or multiple layers. However, the material of the first sealant layer, which is the innermost layer of the battery packaging material, i.e., the material of the layers that come into contact with each other when the battery packaging materials arranged face to face are heat-sealed, is specified, and if necessary, the materials of layers other than the first sealant layer are further specified.

[0030] 1 has a three-layer structure in which the first sealant layer 21, the second sealant layer 22, and the third sealant layer 23 are laminated in this order from the inside of the battery packaging material 1 toward the barrier layer 11. The first sealant layer 21 is the innermost layer of the battery packaging material 1 that is farthest from the barrier layer 11, the third sealant layer 23 is the layer that is closest to the barrier layer 11 and in contact with the second adhesive layer 14, and the second sealant layer 22 is an intermediate layer between the first sealant layer 21 and the third sealant layer 23.

[0031] The sealant layer 20B of the battery packaging material 2 in Fig. 2 has a two-layer structure consisting of a first sealant layer 21, which is the innermost layer, and a third sealant layer 23, which is closest to the barrier layer 11. The sealant layer 20C of the battery packaging material 3 in Fig. 3 is a single layer consisting of the first sealant layer 21, which is the innermost layer.

[0032] In the present invention, regardless of the number of sealant layers 20A, 20B, 20C, the innermost layer is referred to as the first sealant layer 21. The first sealant layer 21 is an essential layer in the present invention. In the sealant layers 20A, 20B having two or more layers, the layer closest to the barrier layer 11 is referred to as the third sealant layer 23. In the sealant layer 20A having three or more layers, all layers between the first sealant layer 21 and the third sealant layer 23 are referred to as the second sealant layer 22. Therefore, in a sealant layer having four or more layers (not shown), the second sealant layer 22 is composed of two or more layers.

[0033] (First sealant layer) In the present invention, the first sealant layer 21 must be made of a resin containing polybutene copolymer A containing at least one of butene-ethylene copolymer, butene-propylene copolymer, and copolymer of butene-1 and an α-olefin having 5 or more carbon atoms (C). Examples of polybutene copolymer A include resins containing at least one of butene-ethylene copolymer, butene-propylene copolymer, and copolymer of butene-1 and an α-olefin having 5 or more carbon atoms (C). In the present invention, since the resin constituting the first sealant layer contains polybutene copolymer A containing a butene-1 component, the side chains are bulkier than those of polypropylene or polyethylene, and steric hindrance has the effect of lowering the crystallinity of the resin, resulting in a lower melting point. Therefore, when the temperature of a battery case produced by heat-sealing the first sealant layers rises excessively, gas generated in the battery body inside the case accumulates and the internal pressure rises, the low melting point component softens due to the rise in temperature, the seal strength decreases, and the seal is gradually opened, allowing the gas inside the battery case to be efficiently released to the outside, preventing problems such as rupture of the packaging material due to an increase in the internal pressure of the battery case.

[0034] In the present invention, the polybutene copolymer A contained in the first sealant layer is preferably 30% by mass to 50% by mass. That is, since the content of polybutene copolymer A is 30% by mass or more, gas can be efficiently discharged when the internal pressure rises during excessive heating of the battery case produced by heat-sealing the first sealant layers, while the content of polybutene copolymer A is 50% by mass or less, sufficient seal strength can be maintained up to about 100°C, and inadvertent peeling of the sealed portion at low temperatures can be prevented. In addition, in the present invention, it is preferable to use polybutene copolymer A having a melting point in the range of 80°C to 120°C, and more preferably, one having a melting point in the range of 105°C to 115°C. That is, when this configuration is adopted, inadvertent peeling of the sealed portion at low temperatures can be more reliably prevented, while gas can be more reliably discharged during excessive heating. In the present invention, by using a mixture of the above-mentioned polybutene copolymer A and the following propylene random copolymer B as the resin constituting the first sealant layer, gas inside the battery case can be more appropriately released when the temperature rises excessively, and defects caused by an increase in the internal pressure of the battery case can be more reliably prevented.

[0035] Examples of the propylene random copolymer B include resins containing at least one selected from the group consisting of propylene-ethylene random copolymers, propylene-butene random copolymers, propylene-ethylene-butene random copolymers, propylene produced using a metallocene catalyst, and propylene compounds produced using a metallocene catalyst.

[0036] The blending ratio of the polybutene copolymer A to the propylene random copolymer B is preferably set to 30:70 to 50:50, and more preferably 35:65 to 50:50. In other words, when this configuration is adopted, gas release during excessive temperature rise can be carried out more effectively.

[0037] Furthermore, the propylene random copolymer B preferably has a melting point in the range of 80° C. to 120° C., more preferably in the range of 90° C. to 110° C. That is, when this configuration is adopted, the above-mentioned effects can be obtained more reliably.

[0038] The first sealant layer 21 containing the polybutene copolymer A may contain, in addition to the propylene random copolymer B, other resins.

[0039] (Second sealant layer) In the present invention, a polypropylene-based resin containing a propylene block copolymer and a propylene random copolymer can be used as the second sealant layer 22. Specifically, the second sealant layer 22 can be exemplified by at least one resin selected from a propylene-ethylene random copolymer, a propylene-butene random copolymer, a propylene-ethylene-butene random copolymer, a propylene produced using a metallocene catalyst (metallocene-based propylene), a propylene compound produced using a metallocene catalyst (metallocene-based propylene compound), a propylene-ethylene block copolymer, a propylene-butene block copolymer, and a propylene-ethylene-butene block copolymer.

[0040] The particularly preferred melting point of the resin constituting the second sealant layer 22 is 130° C. or higher.

[0041] In the present invention, since the second sealant layer contains a heat-resistant block copolymer, the second sealant layer remains with a sufficient space (layer thickness) when heat-sealing is performed to produce a battery case, so that the remaining second sealant layer reliably maintains insulation and reliably fuses only the first sealant layers together. When internal pressure increases due to excessive heating, the gas discharge function can be reliably performed in a desired, relatively low temperature range, and defects due to increased internal pressure in the battery case can be more reliably prevented.

[0042] (Third sealant layer) In the present invention, the third sealant layer 23 may be a propylene random copolymer having a melting point higher than that of the first sealant layer 21. Specific examples of the third sealant layer 23 include at least one resin selected from a propylene-ethylene random copolymer, a propylene-butene random copolymer, a propylene-ethylene-butene random copolymer, a propylene prepared using a metallocene catalyst, a propylene compound prepared using a metallocene catalyst, a propylene-ethylene block copolymer, a propylene-butene block copolymer, a propylene-ethylene-butene block copolymer, and a propylene homopolymer.

[0043] The particularly preferred melting point of the resin constituting the third sealant layer 23 is 130° C. or higher, and more preferably 140° C. or higher. Furthermore, it is even more preferred that the third sealant layer 23 has a higher melting point than the second sealant layer 22.

[0044] In the present invention, since the third sealant layer has a higher melting point than the first sealant layer, the first sealant layers can be reliably heat-sealed to each other before the third sealant layer melts during sealing, so that the remaining third sealant layer can more reliably maintain insulation, and the first sealant layers can be more reliably fused to each other, thereby appropriately preventing defects caused by an increase in the internal pressure of the battery case. Furthermore, since the third sealant layer contains a propylene random copolymer, it has a small elastomer component, making it difficult for voids to occur, and has a small steric hindrance due to its structure, so that it has good adhesion to the adhesive layer, and can prevent electrolyte erosion even if liquid biting occurs during heat sealing, and can prevent interfacial peeling between adhesive layers, for example, between the adhesive layer and the metal foil or between the adhesive layer and the sealant layer, and can reliably improve the possibility of peeling occurring between the first sealant layers when the temperature rises excessively, and in this respect, it is also possible to prevent defects caused by an increase in the internal pressure of the battery case.

[0045] (Sealant layer additives, etc.) In addition to the above-mentioned resin, additives such as lubricants, antiblocking agents, etc. can be blended into each of the sealant layers 20A, 20B, and 20C. The lubricants and antiblocking agents have the effect of increasing the slipperiness and improving the moldability.

[0046] The lubricant is not particularly limited, but examples thereof include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylol amides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, and aromatic bisamides.

[0047] Examples of the saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide.

[0048] Examples of the unsaturated fatty acid amide include oleic acid amide and erucic acid amide.

[0049] Examples of the substituted amides include N-oleyl palmitic acid amide, N-stearyl stearic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, and N-stearyl erucic acid amide.

[0050] Methylol amides include methylol stearic acid amide.

[0051] Examples of saturated fatty acid bisamides include methylene bisstearic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bisstearic acid amide, ethylene bishydroxystearic acid amide, ethylene bisbehenic acid amide, hexamethylene bisstearic acid amide, hexamethylene bisbehenic acid amide, hexamethylene hydroxystearic acid amide, N,N'-distearyl adipic acid amide, and N,N'-distearyl sebacic acid amide.

[0052] Examples of the unsaturated fatty acid bisamide include ethylene bis oleamide, ethylene bis erucamide, hexamethylene bis oleamide, N,N'-dioleyl adipamide, and N,N'-dioleyl sebacamide.

[0053] The fatty acid ester amide can include stearamidoethyl stearate.

[0054] Examples of aromatic bisamides include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, and N,N'-distearylisophthalic acid amide.

[0055] The antiblocking agent is not particularly limited, but examples thereof include particles of silica, acrylic resin, aluminum silicate, calcium carbonate, barium carbonate, titanium oxide, talc, kaolin, and the like.

[0056] The preferred concentrations of the various additives in the sealant layers 20A, 20B, and 20C are as follows: the lubricant concentration is 100 ppm to 3000 ppm, and the antiblocking agent concentration is 100 ppm to 5000 ppm.

[0057] The total thickness (T) of the sealant layers 20A, 20B, and 20C is preferably 20 μm to 100 μm, more preferably 20 μm to 80 μm. It is even more preferable that the total thickness is 25 μm to 50 μm. In the sealant layer 20B having a two-layer structure consisting of the first sealant layer 21 and the third sealant layer 23, when the total thickness (T) is 10, the ratio t1:t3 of the thickness (t1) of the first sealant layer 21 to the thickness (t3) of the third sealant layer 23 is preferably 2 to 8: 8 to 2, and even more preferably 4 to 8: 6 to 2. In addition, in the sealant layer 20A having a three-layer structure consisting of the first sealant layer 21, the second sealant layer 22, and the third sealant layer 23, when the total thickness (T) is taken as 10, the ratio t1:t2:t3 of the thickness (t1) of the first sealant layer 21, the thickness (t2) of the second sealant layer 22, and the thickness (t3) of the third sealant layer 23 is preferably distributed as 1-4:2-7:1-7, and even more preferably 2-4:2-4:3-6.

[0058] (Layer other than sealant layer of battery packaging material) In the battery packaging material of the present invention, well-known materials can be appropriately used for the layers other than the sealant layer, and the lamination method is not particularly limited. Preferred materials for the layers other than the sealant layer are described below.

[0059] (base material layer) The base layer 13 is made of a heat-resistant resin film that does not melt at the heat-sealing temperature when the battery packaging materials 1, 2, and 3 are heat-sealed. The heat-resistant resin is a heat-resistant resin having a melting point 10° C. or higher, preferably 20° C. or higher, than the melting point of the resin constituting the sealant layers 20A, 20B, and 20C. Examples of resins that satisfy this condition include polyamide films such as nylon films, polyester films, and the like, and stretched films thereof are preferably used. Among them, it is particularly preferable to use biaxially stretched polyamide films such as biaxially stretched nylon films, biaxially stretched polybutylene terephthalate (PBT) films, biaxially stretched polyethylene terephthalate (PET) films, or biaxially stretched polyethylene naphthalate (PEN) films as the base layer 13. The nylon film is not particularly limited, and examples thereof include 6 nylon film, 6,6 nylon film, and MXD nylon film. The base layer 13 may be formed of a single layer, or may be formed of a multi-layer structure made of, for example, a polyester film / polyamide film (such as a multi-layer structure made of a PET film / nylon film).

[0060] The thickness of the base layer 13 is preferably 9 μm to 50 μm, which can ensure sufficient strength as a packaging material and can improve formability by reducing stress during molding such as stretch molding and drawing molding. The more preferable thickness of the base layer 13 is 12 μm to 30 μm.

[0061] (Barrier layer) The barrier layer 11 plays a role of imparting gas barrier properties that prevent the intrusion of oxygen and moisture to the battery packaging materials 1, 2, and 3. The barrier layer 11 is not particularly limited, and examples thereof include metal foils such as aluminum foil, SUS foil (stainless steel foil), copper foil, nickel foil, titanium foil, and clad foil. The thickness of the barrier layer 11 is preferably 20 μm to 100 μm. When the thickness is 20 μm or more, the occurrence of pinholes during rolling in manufacturing the metal foil can be prevented, and when the thickness is 100 μm or less, stress during molding such as stretch molding and drawing can be reduced, thereby improving moldability. The particularly preferred thickness of the barrier layer 11 is 30 μm to 80 μm.

[0062] In addition, it is preferable that the barrier layer 11 is subjected to a base treatment such as a chemical conversion treatment at least on the surface of the metal foil on the side of the sealant layers 20A, 20B, and 20C. By performing such a chemical conversion treatment, corrosion of the metal foil surface due to the contents (such as a battery electrolyte) can be sufficiently prevented.

[0063] For example, the metal foil is subjected to a chemical conversion treatment by carrying out the following treatment.

[0064] A chemical conversion treatment is carried out by applying an aqueous solution of any one of the following 1) to 3) to the surface of the metal foil that has been subjected to a degreasing treatment, and then drying the applied solution. 1) An aqueous solution of a mixture containing phosphoric acid, chromic acid, and at least one compound selected from the group consisting of metal salts of fluorides and nonmetal salts of fluorides. 2) An aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, and at least one compound selected from the group consisting of chromic acid and chromium (III) salts. 3) An aqueous solution of a mixture containing phosphoric acid, at least one resin selected from the group consisting of acrylic resins, chitosan derivative resins, and phenolic resins, at least one compound selected from the group consisting of chromic acid and chromium (III) salts, and at least one compound selected from the group consisting of metal salts of fluorides and nonmetal salts of fluorides. The chemical conversion coating has a chromium coating weight (per side) of 0.1 mg / m 2 ~50mg / m 2 is preferred, and 2 mg / m 2 ~20mg / m 2 is preferred.

[0065] (First adhesive layer) The first adhesive layer 12 is not particularly limited, and examples thereof include an adhesive layer formed of a two-liquid curing adhesive. Examples of the two-liquid curing adhesive include a two-liquid curing adhesive composed of a first liquid (base agent) made of one or more polyols selected from the group consisting of polyurethane polyols, polyester polyols, polyether polyols, and polyester urethane polyols, and a second liquid (curing agent) made of isocyanate. Among them, it is preferable to use a two-liquid curing adhesive composed of a first liquid made of one or more polyols selected from the group consisting of polyester polyols and polyester urethane polyols, and a second liquid (curing agent) made of isocyanate. The preferred thickness of the first adhesive layer 12 is 1 μm to 5 μm, and more preferably 2 μm to 5 μm.

[0066] (Second adhesive layer) The second adhesive layer 14 is not particularly limited, but in the case of the dry lamination method, for example, an adhesive containing one or more of polyurethane resin, acrylic resin, epoxy resin, polyolefin resin, elastomer resin, fluorine resin, and acid-modified polypropylene resin is recommended. Among them, an adhesive made of a polyurethane composite resin mainly composed of acid-modified polyolefin is preferable. In addition, in the case of the sand lamination method or the thermal lamination method, for example, a modified polyolefin resin such as an acid-modified polypropylene resin or an acid-modified polyethylene resin is recommended. The preferred thickness of the second adhesive layer 14 varies depending on the lamination method, and in the case of the dry lamination method, it is preferably 2 μm to 5 μm, and in the case of the sand lamination method or the thermal lamination method, it is preferably 2 μm to 20 μm.

[0067] (Other lamination forms for battery packaging materials) In the battery packaging material of the present invention, the first adhesive layer and the second adhesive layer are not essential layers, and the base layer may be bonded directly to the barrier layer, or the sealant layer may be bonded directly to the barrier layer.

[0068] In addition, the battery packaging material of the present invention may be configured such that the outer layer is composed of a plurality of layers including the substrate layer by forming another layer on the outer side of the substrate layer. Examples of the layer formed on the outer side of the substrate layer include a protective layer and a matte coat layer. These layers are the outermost layers of the battery packaging material and protect the substrate layer, and also have the effect of imparting good slip properties to the surface to enhance moldability.

[0069] As the material of the protective layer, phenoxy resin, urethane resin, epoxy resin, acrylic resin, polyolefin resin, fluorine resin, etc. can be recommended. The matte coat layer is made of a resin composition in which a matte agent is mixed with a resin, and as the matte agent, inorganic particles such as silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, calcium silicate, etc., resin beads such as acrylic beads, etc. can be recommended.

[0070] (Battery Construction) As shown in Figures 4 and 5, the battery packaging materials 1, 2, and 3, which have been formed as necessary, are heat-sealed around the periphery with a bare cell (battery body) 51 housed inside the packaging material, thereby producing a battery (energy storage device) in which the bare cell 51 is sealed inside a battery case 50.

[0071] In the present invention, the battery case 50 is preferably adjusted so that the seal strength of the heat-sealed portion in an environment of 100° C. is 20 N / 15 mm width or more. In other words, in this case, the heat-sealed portion can reliably maintain a desired sealed state until a predetermined excessive temperature range is reached, and inadvertent peeling of the sealed portion at low temperatures can be prevented, resulting in a high-quality, high-performance battery product. EXAMPLES

[0072] Examples including the gist of the present invention and comparative examples for demonstrating the effects of the present invention will be described below.

[0073] [Table 1]

[0074] [Table 2]

[0075] Battery packaging materials were produced in Examples 1 to 16 and Comparative Examples 1 to 3. As shown in battery packaging materials 1, 2, and 3 in Figures 1 to 3, these battery packaging materials have a base layer 13 bonded to one surface of a barrier layer 11 via a first adhesive layer 12, and sealant layers 20A, 20B, and 20C bonded to the other surface via a second adhesive layer 14. The battery packaging materials have the barrier layer 11, base layer 13, first adhesive layer 12, and second adhesive layer 14 in common, but the layer configurations and materials of the sealant layers 20A, 20B, and 20C are different.

[0076] The sealant layer 20C of the battery packaging material of Example 1 has a single-layer structure of a first sealant layer 21 (see FIG. 3). The sealant layer 20B of Example 2 has a two-layer structure of a first sealant layer 21 and a third sealant layer 23 (see FIG. 2). The sealant layers 20A of Examples 3 to 16 and Comparative Examples 1 to 3 have a three-layer structure of a first sealant layer 21, a second sealant layer 22, and a third sealant layer 23 (see FIG. 1).

[0077] For the battery packaging material of each example, a single-layer or multi-layer sealant layer film was prepared using the materials and method described below, and the sealant layer film was attached to a laminate film (laminate film) of a base layer, a first adhesive layer, and a barrier layer prepared using materials common to each example, via a second adhesive. Details of the sealant layer film of each example and the method of preparing the battery packaging material are as follows.

[0078] <Example 1> A 1-butene-propylene copolymer (melting point 110°C) which is the resin A (polybutene copolymer A) of the first sealant layer shown in Table 1, and a propylene-1-butene copolymer (melting point 130°C) which is the resin B (propylene random copolymer B) of the first sealant layer shown in Table 1 were mixed at the content (mass%) shown in Table 1, and 1000 ppm of erucic acid amide as a lubricant and 2000 ppm of silica particles as an antiblocking agent were blended into the mixed resin to prepare a resin composition for the first sealant layer. This composition was extruded through a T-die to produce a film for the sealant layer having a single layer structure and a thickness of 30 μm.

[0079] <Example 2> Resins A and B for the first sealant layer shown in Table 1 were used to prepare a resin composition for the first sealant layer in the same manner as above, and a film for a sealant layer having a single layer structure was produced in the same manner as above.

[0080] <Examples 3 and 4> A resin composition for the first sealant layer was prepared in the same manner as above using resins A and B for the first sealant layer shown in Table 1. Furthermore, a resin composition for the third sealant layer was prepared by blending 1000 ppm of erucic acid amide (lubricant) and 2000 ppm of silica particles (antiblocking agent) with the resin for the third sealant layer (propylene-ethylene random copolymer: melting point 142°C) shown in Table 2. The resin compositions for the first and third sealant layers were co-extruded using a T-die so that they were laminated, thereby producing a two-layered film for the sealant layer having a thickness of 30 μm, in which a first sealant layer having a thickness of 15 μm and a third sealant layer having a thickness of 15 μm were laminated.

[0081] <Example 5> A resin composition for the first sealant layer was prepared in the same manner as above using resins A and B for the first sealant layer shown in Table 1. Furthermore, a resin composition for the second sealant layer was prepared by blending 1000 ppm of erucic acid amide (lubricant) and 2000 ppm of silica particles (antiblocking agent) with a mixed resin (melting point 135°C) of rPP (propylene-ethylene random copolymer) and bPP (propylene-ethylene block copolymer) which is the resin for the second sealant layer shown in Table 2. Furthermore, a resin composition for the third sealant layer was prepared in the same manner as above using a propylene-ethylene random copolymer which is the resin for the third sealant layer shown in Table 2.

[0082] The resin compositions for the first to third sealant layers were co-extruded using a T-die so that they were laminated, to produce a 30 μm-thick film for sealant layers having a three-layer structure in which a first sealant layer having a thickness of 6 μm, a second sealant layer having a thickness of 18 μm, and a third sealant layer having a thickness of 6 μm were laminated in this order.

[0083] <Examples 6 to 10, 12 to 16> A resin composition for the first sealant layer was prepared in the same manner as above using resins A and B for the first sealant layer shown in Table 1. Furthermore, resin compositions for the second and third sealant layers were prepared in the same manner as above using resins for the second and third sealant layers shown in Table 2. Then, films for sealant layers were produced in the same manner as above using the resin compositions for the first to third sealant layers.

[0084] <Example 11> A resin composition for the first sealant layer was prepared in the same manner as above using resins A, B, and C for the first sealant layer shown in Table 1. Furthermore, resin compositions for the second and third sealant layers were prepared in the same manner as above using resins for the second and third sealant layers shown in Table 2. Then, films for sealant layers were produced in the same manner as above using the resin compositions for the first to third sealant layers.

[0085] <Comparative Examples 1 to 3> A resin composition for the first sealant layer was prepared in the same manner as above using resin A, B or resin A for the first sealant layer shown in Table 1. Furthermore, resin compositions for the second and third sealant layers were prepared in the same manner as above using resins for the second and third sealant layers shown in Table 2. Then, films for sealant layers were produced in the same manner as above using the resin compositions for the first to third sealant layers.

[0086] (Method of measuring melting point) The melting point of each resin used in the above Examples and Comparative Examples is the temperature Tpm at the top of the peak measured by differential scanning calorimetry (DSC) at a heating rate of 10° C. / min in accordance with JIS K7121.

[0087] (Production of packaging materials for batteries) The barrier layer 11 was made by applying a chemical conversion treatment solution consisting of polyacrylic acid (acrylic resin), a chromium (III) salt compound, water, and alcohol to both sides of an aluminum foil made of A8079 with a thickness of 40 μm, and then drying the coating at 150° C. The chromium deposition amount of the chemical conversion coating was 5 mg / m per side. 2 In addition, a biaxially oriented nylon 6 film having a thickness of 15 μm was used as the base layer 13.

[0088] A two-component curing urethane adhesive (first adhesive layer) was applied to one surface (outer surface) of the barrier layer 11 to form a first adhesive layer 12 having a thickness of 3 μm, and the base material layer 13 was dry laminated thereon.

[0089] Next, a two-component curing maleic acid-modified propylene adhesive (second adhesive) was applied to the other surface (inner surface) of the barrier layer 11 to form a second adhesive layer 14 having a thickness of 2 μm, and each of the films for sealant layers of the above Examples and Comparative Examples was dry laminated onto the film. At this time, the first sealant layer 21 was in contact with the second adhesive layer 14 for the single-layer sealant layer film, and the third sealant layer 23 was in contact with the second adhesive layer 14 for the two- or three-layer sealant layer film.

[0090] The laminate sheet with all layers bonded together was then sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressed to complete the dry lamination, after which it was aged (heated) at 40°C for 10 days to obtain the battery packaging materials of the examples and comparative examples.

[0091] (Evaluation of battery packaging materials) The battery packaging materials of each example prepared were measured and evaluated for the following items. The results are shown in Table 2.

[0092] (Seal strength) The battery packaging material was cut to a width of 15 mm and a length of 150 mm to prepare a plurality of test pieces. Two test pieces were stacked so that the sealant layers 20A, 20B, and 20C faced each other, and heat-sealed by heating on one side using a heat-sealing device (manufactured by Tester Sangyo Co., Ltd., TP-701-A) under the conditions of heat-sealing temperature: 180°C, sealing pressure: 0.3 MPa (gauge pressure), and sealing time: 4 seconds, to prepare a test piece for seal strength. Three test pieces for measuring the seal strength were prepared for each example.

[0093] The three test pieces for measuring the seal strength were left to stand for 24 hours at three different temperatures, 25°C, 100°C, and 130°C, and then the seal strength was measured at each temperature.

[0094] The seal strength was measured in accordance with JIS Z0238-1998 using a tensile tester, Strograph (AGS-5kNX) manufactured by Shimadzu Corporation. One end of a test piece of the test material was clamped and fixed with one chuck of the tensile tester, while the other end of the test piece was gripped with the other chuck, and the peel strength was measured when T-peeling was performed at a tensile speed of 100 mm / min, and this was taken as the seal strength (N / 15 mm width).

[0095] (Opening test) The battery packaging material was cut to a width of 100 mm and a length of 200 mm to prepare a rectangular test material. This rectangular test material was folded in half at the center in the longitudinal direction with the sealant layers 20A, 20B, and 20C on the inside, and the two sides following the fold were heated on one side under the conditions of a seal width of 5 mm, a heat seal temperature of 180°C, a seal pressure of 0.3 MPa (gauge pressure), and a seal time of 4 seconds to form a bag with an opening on the side opposite the fold. Next, 2.0 g of water was poured into the opening of the bag, and the opening side was heat sealed under the same conditions as the other two sides to seal the bag, which was used as a test specimen for the opening test.

[0096] The specimen for the opening test was placed in an oven, heated from 25°C to 130°C at a temperature increase rate of 5°C / min, and after reaching 130°C, held at 130°C for 30 minutes. The opening condition was observed from the time of temperature increase until the time of holding at 130°C for 30 minutes was completed, and evaluated according to the following criteria. The following criteria A to D are acceptable, and X and Y are unacceptable. A: The container was opened while the temperature was rising from 100℃ to 130℃, and gas escaped slowly. B: The container was not opened while the temperature was rising to 130°C, and was opened while the temperature was maintained at 130°C, allowing gas to escape slowly. C: The container was opened while the temperature was rising from 100°C to 130°C, and gas escaped rapidly. D: The container was not opened while the temperature was rising to 130°C, and gas escaped rapidly while the temperature was held at 130°C. X: The container was not opened even when kept at 130°C. Y: Opened while heating up to 100°C.

[0097] This test was based on the external heating test (JIS C8714), but while JIS C8714 requires a 130°C retention time of 10 minutes after reaching 130°C, this test required a 130°C retention time of 30 minutes, performing heating under more severe conditions.

[0098] From the results in Table 2, it was confirmed that the battery packaging materials of the Examples maintained high seal strength at temperatures below 100°C, and the seal strength gradually decreased between 100°C and 130°C, allowing for gentle opening. [Industrial Applicability]

[0099] The battery packaging material of the present invention can be suitably used as a case material for secondary batteries for vehicle-mounted, stationary, notebook computers, mobile phones, and cameras, in particular small, portable lithium-ion secondary batteries. [Explanation of symbols]

[0100] 1, 2, 3…Battery packaging material 11...Barrier layer 13...Base material layer 20A, 20B, 20C…Sealant layer 21…First sealant layer 22…Second sealant layer 23…Third sealant layer 50…Battery case

Claims

1. A packaging material for a battery comprising a substrate layer as an outer layer, a sealant layer as an inner layer, and a barrier layer disposed between these layers, The sealant layer is composed of one or more layers, and a first sealant layer is disposed on the innermost side of the sealant layer; The battery packaging material is characterized in that the resin constituting the first sealant layer includes a polybutene copolymer A including at least one of a butene-ethylene copolymer, a butene-propylene copolymer, and a copolymer of an α-olefin having 5 or more carbon atoms and butene-1.

2. The resin constituting the first sealant layer contains 30% by mass to 50% by mass of the polybutene copolymer A and 50% by mass to 70% by mass of a propylene random copolymer. The battery packaging material according to claim 1.

3. 3. The battery packaging material according to claim 1, wherein the polybutene copolymer A has a melting point of 120° C. or lower.

4. the sealant layer has a multi-layer structure including the first sealant layer, a third sealant layer closest to the barrier layer, and a second sealant layer provided between the first and third sealant layers; 3. The battery packaging material according to claim 1, wherein the second sealant layer is a polypropylene-based resin containing a propylene block copolymer and a propylene random copolymer.

5. the sealant layer is a multi-layer structure including the first sealant layer and a third sealant layer closest to the barrier layer; 3. The battery packaging material according to claim 1, wherein the third sealant layer contains a propylene random copolymer having a melting point higher than that of the first sealant layer.

6. 3. The battery packaging material according to claim 1, wherein the sealant layers are heat-sealed together, and the heat-sealed portion has a seal strength of 20 N / 15 mm width or more in an environment of 100°C.

7. A battery case formed by heat-sealing the sealant layers of the battery packaging material according to claim 1 or 2, A battery case, characterized in that the heat-sealed portion has a seal strength of 20 N / 15 mm width or more in an environment of 100°C.

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