Battery packaging materials

Abstract

To provide a packaging material for a battery in which a seal strength is reduced at a temperature at which flammable gas caused by an electrolyte is generated, and a case is opened.SOLUTION: A packaging material 1 for a battery includes a base material layer 13 as an outside layer, a sealant layer 20 as an inside layer, and a barrier layer 11 arranged therebetween, in which the sealant layer 20 is composed of a single layer or multi-layers, the first sealant layer 21 as the innermost layer is composed of a propylene-based resin containing an ethylene-propylene copolymer, and the ethylene-propylene copolymer has a ratio Mw / Mn of a weight average molecular weight Mw to a number average molecular weight Mn measured by gel permeation chromatography (GPC) of 1-7, a melt flow rate measured at 230°C and a load of 2.16 kg according to JIS K 7210 of 5 g / 10 min to 30 g / 10 min, and a melting point calculated by differential scanning calorimetry of 120-135°C.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a battery packaging material and related technologies suitable for use as a case for secondary batteries, particularly small portable lithium ion secondary batteries, for example, in vehicles, stationary batteries, notebook computers, mobile phones, and cameras. [Background technology]

[0002] Energy storage devices, such as lithium-ion batteries, can be manufactured into a variety of shapes and are even thinner and lighter by using laminated packaging materials, which consist of aluminum cans or cases with resin layers bonded to both sides. In energy storage devices that use laminated packaging materials, as the internal temperature of the battery rises as the device's capacity increases, gas is generated due to the volatilization of the electrolyte, etc., causing the internal pressure to rise and the case to expand or even burst. Furthermore, if the gas is flammable, there is a risk of fire. For this reason, measures are taken to gently release the gas to prevent bursting of the device's case (see Patent Documents 1 and 2).

[0003] Patent document 1 describes a preventive measure based on the structure of the case, and discloses a valve mechanism that reduces the pressure inside the case when the pressure inside the case rises, and an air vent that guides the gas inside the case to the valve mechanism.

[0004] Patent Document 2 describes a preventive measure using case materials, disclosing technology in which the heat-sealable resin layer (sealant layer) of the laminate material is made of a resin with a peak melting temperature of 130°C or less, thereby suppressing expansion of the battery when exposed to a high-temperature environment and allowing the battery to be opened gently. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6540871 [Patent Document 2] JP 2019-29300 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the preventive measures described in Patent Document 1 require additional components such as a valve mechanism and a ventilation path, which increases both material and manufacturing costs. Furthermore, the laminate material described in Patent Document 2 controls the opening temperature based on the peak melting temperature of the sealant layer, so it must be designed to be opened at a low temperature range to ensure it can be opened before rupture occurs. This creates the risk of opening the battery even at operating temperatures where gas is not generated. [Means for solving the problem]

[0007] In view of the above-mentioned technical background, the present invention provides a battery packaging material in which the seal strength is reduced at a temperature at which flammable gas originating from the electrolyte is generated, thereby allowing the case to be opened.

[0008] That is, the present invention has the configurations described in the following [1] to [8].

[0009] [1] A battery packaging material including a substrate layer as an outer layer, a sealant layer as an inner layer, and a barrier layer disposed between these two layers, The sealant layer is composed of a single layer or multiple layers, and the first sealant layer, which is the innermost layer, is composed of a propylene-based resin including an ethylene-propylene copolymer; The ethylene-propylene copolymer has a ratio Mw / Mn of weight average molecular weight Mw to number average molecular weight Mn of 1 to 7 as measured by gel permeation chromatography (GPC), a melt flow rate of 5 g / 10 min to 30 g / 10 min as measured at 230°C under a load of 2.16 kg according to JIS K7210, and a melting point of 120°C to 135°C as calculated by differential scanning calorimetry.

[0010] [2] The battery packaging material according to the above item 1, wherein the ethylene-propylene copolymer is a copolymer derived from a methacerone catalyst.

[0011] [3] The battery packaging material according to the above item 1 or 2, wherein the propylene-based resin is a mixture of an ethylene-propylene copolymer and polyethylene, and the polyethylene content in the mixture is 7% by mass to 20% by mass.

[0012] [4] The battery packaging material according to the preceding paragraph 3, wherein 70% by mass or more of the polyethylene is polyethylene derived from a metallocene catalyst.

[0013] [5] The sealant layer is a multilayer structure in which the first sealant layer, one or more second sealant layers, and a third sealant layer are laminated in this order from the inside of the battery packaging material toward the barrier layer side, the third sealant layer is made of an ethylene-propylene random copolymer, 5. The battery packaging material according to any one of items 1 to 4 above, wherein the melt flow rate of the resin constituting at least one of the second sealant layers is lower than the melt flow rate of the ethylene-propylene copolymer constituting the first sealant layer.

[0014] [6] A battery case characterized in that the battery packaging material according to any one of the preceding paragraphs 1 to 5 is joined together with the sealant layers facing inward, and the edges are heat-sealed to form a battery element chamber for accommodating a battery element.

[0015] [7] The battery case according to item 6, wherein the seal strength of the edge of the battery element chamber is 60 N / 15 mm or more at room temperature, 25 N / 15 mm or more at 100°C, and 6 N / 15 mm to 12 N / 15 mm at 130°C.

[0016] [8] A battery characterized in that a battery element is housed in the battery element chamber of the battery case described in the preceding paragraph 6 or 7. [Effects of the Invention]

[0017] In the battery packaging material described in [1] above, the first sealant layer of the innermost sealant layer is composed of a propylene-based resin containing an ethylene-propylene copolymer with specified properties, and therefore the seal strength drops sharply between 110°C and 130°C. As the battery temperature rises, gas is generated due to the volatilization of the electrolyte, etc., and the pressure inside the case rises and the case begins to expand at around 130°C. However, in a battery using a case made from the battery packaging material, the seal strength drops and the seal comes off and the battery is opened at 110°C to 130°C, which is lower than the temperature at which the case begins to expand, and the gas is gently released, preventing the case from bursting or catching fire.

[0018] The battery packing material described in [2] above can reduce the seal strength at the targeted temperature because the ethylene-propylene copolymer in the sealant layer is a copolymer derived from a metallocene catalyst.

[0019] The battery packaging material described in [3] above has a sealant layer made of a propylene-based resin containing a predetermined amount of polyethylene, and is therefore highly effective in reducing the seal strength at the desired temperature.

[0020] In the battery packaging material described in [4] above, 70% by mass or more of the polyethylene in the propylene-based resin constituting the sealant layer is derived from a metallocene catalyst, which makes it easy to disperse in polypropylene and improves the effect of controlling the temperature at which the seal strength decreases to the desired temperature.

[0021] The battery packaging material described in [5] above has a sealant layer that is a multilayer structure consisting of a first sealant layer, a second sealant layer, and a third sealant layer. The third sealant layer is made of an ethylene-propylene random copolymer, which provides a strong adhesive force to the barrier layer. The second sealant layer is made of a resin with a lower melting point than the ethylene-propylene copolymer of the first sealant layer, which allows the packing to be opened at the seal between the first sealant layers.

[0022] According to the battery case described in [6] above, the effects of the battery packaging material described above can be obtained.

[0023] The battery case described in [7] above can be opened at 110°C to 130°C when the seal on the edge of the battery element chamber comes off.

[0024] According to the battery described in [8] above, the effects of the battery packaging material described above can be obtained. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a cross-sectional view of an embodiment of a battery packaging material of the present invention. [Figure 2] 2 is a cross-sectional view of a battery equipped with a battery case made from the battery packaging material of FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0026] FIG. 1 shows one embodiment of the battery packaging material of the present invention. [Battery packaging material] The battery packaging material 1 has a base material layer 13 bonded to one surface of a barrier layer 11 via a first adhesive layer 12, and a multi-layer sealant layer 20 bonded to the other surface via a second adhesive layer 14. The battery packaging material 1 is arranged with the sealant layers 20 facing each other, and a battery case is produced by heat-sealing the periphery of the battery packaging material 1. In the produced battery case, the base material layer 13 becomes the outer layer, and the sealant layer 20 becomes the inner layer. [Sealant layer of battery packaging material] The battery packaging material of the present invention is characterized by the material of the sealant layer, which is the inner layer. The sealant layer provides excellent chemical resistance, even against highly corrosive electrolytes, and also serves to impart heat-sealability to the laminate material. The sealant layer may be either a single layer or multiple layers, but the material of the first sealant layer, which is the innermost layer, i.e., the layer that comes into contact when two battery packaging materials arranged face to face are heat-sealed, is specified as follows.

[0027] The sealant layer 20 in the illustrated example 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 third sealant layer 23 contacts 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 33.

[0028] The first sealant layer 21 is made of a propylene-based resin, which is a resin containing at least an ethylene-propylene copolymer containing ethylene and propylene as copolymerization components.

[0029] The ethylene-propylene copolymer may be any of a random copolymer, a block copolymer, and a block copolymer, but it must satisfy the following three conditions as essential properties. (1) The ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight Mn measured by gel permeation chromatography (GPC) is 1 to 7. The Mw / Mn is preferably 1.2 to 3.5, and more preferably 1.5 to 2.8. (2) The melt flow rate (MFR) measured in accordance with JIS K7210 at 230°C under a load of 2.16 kg is 5 g / 10 min to 30 g / 10 min, preferably 5 g / 10 min to 10 g / min. (3) The melting point calculated by differential scanning calorimetry is 120°C to 135°C, preferably 122°C to 133°C.

[0030] Ethylene-propylene copolymers that meet the above three conditions lose their seal strength at temperatures between 110°C and 130°C, making the seal more likely to come off, but maintain their seal strength at temperatures below these. As the battery temperature rises, gas is generated due to the volatilization of the electrolyte, and at around 130°C, the pressure inside the battery increases and the case begins to expand. The temperature range where the seal strength decreases is higher than the expected temperature range for battery use, but lower than the temperature at which expansion begins. Therefore, when the battery temperature rises suddenly and the internal pressure begins to increase due to gas generation, the seal comes off and the case is opened. When the case is opened, the gas is gently released, preventing the case from bursting or catching fire.

[0031] Ethylene-propylene copolymers that satisfy the above three conditions can be obtained, for example, by copolymerizing the copolymerization components ethylene and propylene using a metallocene catalyst. Ethylene-propylene copolymers derived from a methacelone catalyst tend to have high molecular weight uniformity and satisfy the above three conditions, and are highly effective in reducing seal strength at the desired temperature.

[0032] Furthermore, the propylene-based resin is preferably a mixture of an ethylene-propylene copolymer and polyethylene, and the polyethylene content in the mixture is preferably 7% by mass to 20% by mass. By setting the polyethylene content within the above range, the effect of reducing the seal strength at a targeted temperature is significant. A particularly preferred ethylene content is 10% by mass to 15% by mass. Furthermore, it is preferred that 70% by mass or more of the polyethylene is metallocene-catalyzed polyethylene polymerized using a metallocene catalyst. Metallocene-catalyzed polyethylene is easily dispersed in polypropylene, improving the effect of controlling the temperature at which the seal strength decreases to a targeted temperature. A particularly preferred content of methacerone-catalyzed polyethylene is 85% by mass or more.

[0033] It is preferable that the first sealant layer 21 contains a lubricant and an antiblocking agent.

[0034] 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.

[0035] The saturated fatty acid amide is not particularly limited, but examples thereof include lauric acid amide, Palmitic acid amide , stearic acid amide, behenic acid amide, hydroxystearic acid amide, etc.

[0036] The unsaturated fatty acid amide is not particularly limited, but examples thereof include oleic acid amide and erucic acid amide.

[0037] The substituted amide is not particularly limited, but examples thereof include: N-oleyl palmitic acid amide , N-stearyl stearamide, N-stearyl oleamide, N-oleyl stearamide, N-stearyl erucamide, and the like.

[0038] The methylol amide is not particularly limited, but examples thereof include methylol stearic acid amide.

[0039] The saturated fatty acid bisamide is not particularly limited, but examples thereof 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.

[0040] The unsaturated fatty acid bisamide is not particularly limited, but examples thereof include ethylene bisoleic acid amide, ethylene biserucic acid amide, hexamethylene bisoleic acid amide, and N,N'-dioleyl sebacate amide.

[0041] The fatty acid ester amide is not particularly limited, but examples thereof include stearamidoethyl stearate.

[0042] The aromatic bisamide is not particularly limited, but examples thereof include m-xylylene bisstearic acid amide, m-xylylene bishydroxystearic acid amide, N,N'-distearylisophthalamide etc.

[0043] The lubricant concentration in the first sealant layer 21 is preferably in the range of 100 ppm to 3000 ppm. If the lubricant concentration is less than 100 ppm, moldability is insufficient, but adding 3000 ppm sufficiently improves moldability, so adding a larger amount than that is not preferable from the standpoint of cost. A particularly preferred lubricant concentration is 500 ppm to 2000 ppm.

[0044] 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, etc. The particle size of the antiblocking agent is preferably in the range of 0.1 μm to 10 μm in average particle size, more preferably in the range of 1 μm to 5 μm in average particle size. The concentration of the antiblocking agent is preferably set to 100 ppm to 5000 ppm, and particularly preferably 500 ppm to 4000 ppm.

[0045] By incorporating the antiblocking agent (particles) into the first sealant layer 21 of the sealant layer 20 of the battery packaging material 1, minute protrusions are formed on the surface of the first sealant layer 21, reducing the contact area between films and suppressing blocking between sealant films. Furthermore, by incorporating the antiblocking agent (particles) together with the lubricant, it is possible to further improve the slipperiness during molding.

[0046] When the sealant layer is a single layer, it is the single layer of the first sealant layer 21 described above.

[0047] When the sealant layer 20 is a multi-layer structure, the preferred materials for the layers other than the first sealant layer 21 are as follows: Note that the present invention does not limit the materials for the layers other than the first sealant layer 21.

[0048] Examples of the third sealant layer 23 include an ethylene-propylene copolymer or an ethylene-propylene random copolymer having the same composition as the first sealant layer 21. Furthermore, since the third sealant layer 23, together with the second adhesive layer 14, is a layer for enhancing the bonding strength between the barrier layer 11 and the sealant layer 20, it is preferable that no lubricant or antiblocking agent is added to the third sealant layer 23. However, from the viewpoints of stability during film formation of the sealant layer 20 and prevention of blocking after winding up the sealant layer 20, 1000 ppm or less of erucic acid amide may be added as a lubricant and 2000 ppm or less of silica particles as an antiblocking agent.

[0049] The second sealant layer 22 is an intermediate layer between the first sealant layer 21 and the third sealant layer 23, and may be a propylene homopolymer, a copolymer containing propylene and a copolymer other than propylene as a copolymerization component, or a mixture of multiple polymers. Furthermore, the presence of the same propylene-based resin as that of the first sealant layer 21 improves the adhesion between the second sealant layer 22 and the first sealant layer 21. The second sealant layer 22 may be a single layer or multiple layers.

[0050] The sealant layer 20 in the illustrated example has a three-layer structure, which is obtained by producing a multi-layer film by co-extrusion of the materials of each layer, etc. Furthermore, the sealant layer 20 is preferably a non-stretched film.

[0051] The thickness of the sealant layer 20 is preferably in the range of 20 μm to 100 μm, and more preferably 25 μm to 85 μm. In the illustrated sealant layer 20 having a three-layer structure (including the case where the second sealant layer is a multi-layer), the preferred thickness ratio of each layer is first sealant layer 21:second sealant layer 22:third sealant layer 23=1-3:4-8:1-3.

[0052] When the sealant layer 20 is a multilayer structure, it is preferable to design the sealant layer 20 so that the case can be opened at the seal between the first sealant layers 21 of the two heat-sealed battery packaging materials 1, and to prevent delamination within the sealant layer 20 before the seal between the first sealant layers 21 is released. If delamination occurs within the sealant layer 20, it may be difficult for gas generated inside the battery to escape in a high-temperature environment. Specifically, it is preferable that the third sealant layer 23 be made of an ethylene-propylene random copolymer, and the second sealant layer 22 (or at least one of the layers if the second sealant layer is a multilayer structure) be made of a resin with a melt flow rate lower than that of the ethylene-propylene copolymer of the first sealant layer 21 and a high melting point. By using an ethylene-propylene random copolymer to form the third sealant layer 23, a strong adhesive strength to the barrier layer 11 can be obtained. Furthermore, preferred properties of the material constituting the second sealant layer 22 are a melt flow rate of 2 g / 10 min to 7 g / 10 min measured at 230°C under a load of 2.16 kg according to JIS K7210, and a melting point of 120°C to 165°C calculated by differential scanning calorimetry. A particularly preferred melt flow rate is 2 g / 10 min to 5 g / 10 min, and a particularly preferred melting point is 140°C to 165°C. By setting the materials for the three layers in this way, the case is opened between the first sealant layers 21 of the sealant layers 20 of the two battery packaging materials 1. [Layers other than the sealant layer of battery packaging material] In the battery packaging material of the present invention, well-known materials can be used appropriately 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. (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 material 1 is heat-sealed. The heat-resistant resin has a melting point that is at least 10°C higher, preferably at least 20°C higher, than the melting point of the resin constituting the sealant layer 20. Examples of resins that satisfy this condition include polyamide films such as nylon films and polyester films, and oriented films of these are preferred. Among these, biaxially oriented polyamide films such as biaxially oriented nylon films, biaxially oriented polybutylene terephthalate (PBT) films, biaxially oriented polyethylene terephthalate (PET) films, and biaxially oriented polyethylene naphthalate (PEN) films are particularly preferred for the base layer 13. Examples of nylon films include, but are not limited to, nylon 6 film, nylon 6,6 film, and MXD nylon film. The base layer 13 may be formed as a single layer or as a multilayer structure, such as a polyester film / polyamide film (e.g., a multilayer structure consisting of a PET film / nylon film).

[0053] The thickness of the base material layer 13 is preferably 7 μm to 50 μm, which ensures sufficient strength as a packaging material and improves formability by reducing stress during molding such as stretch molding and drawing.The more preferable thickness of the base material layer 13 is 9 μm to 30 μm. (barrier layer) The barrier layer 11 serves to impart gas barrier properties that prevent the penetration of oxygen and moisture into the battery packaging material 1. The barrier layer 11 is not particularly limited, but 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. A thickness of 20 μm or more can prevent the occurrence of pinholes during rolling in the production of the metal foil, and a thickness of 100 μm or less can reduce stress during forming such as stretch forming and drawing, thereby improving formability. A particularly preferred thickness of the barrier layer 11 is 25 μm to 85 μm.

[0054] Furthermore, it is preferable that the barrier layer 11 is subjected to a surface treatment such as chemical conversion treatment at least on the surface of the metal foil facing the sealant layer 20. By performing such a chemical conversion treatment, corrosion of the metal foil surface due to the contents (such as the electrolyte of a battery) can be sufficiently prevented. (First adhesive layer) The first adhesive layer 12 is not particularly limited, and examples thereof include an adhesive layer formed of a two-component curing adhesive. Examples of the two-component curing adhesive include a two-component curing adhesive composed of a first component (base) 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 component (curing agent) made of an isocyanate. Among these, it is preferable to use a two-component curing adhesive composed of a first component made of one or more polyols selected from the group consisting of polyester polyols and polyester urethane polyols, and a second component (curing agent) made of an isocyanate. The preferred thickness of the first adhesive layer 12 is 2 μm to 5 μm. (Second adhesive layer) The second adhesive layer 14 is not particularly limited, but may be, for example, an adhesive containing one or more of polyurethane resin, acrylic resin, epoxy resin, polyolefin resin, elastomer resin, fluorine resin, or acid-modified polypropylene resin. Among these, an adhesive made of a polyurethane composite resin containing acid-modified polyolefin as a main component is preferred. The second adhesive layer 14 preferably has a thickness of 2 μm to 5 μm. (Other laminated forms of battery packaging) 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 material layer may be directly bonded to the barrier layer, or the sealant layer may be directly bonded to the barrier layer.

[0055] Furthermore, the battery packaging material of the present invention can also be configured such that the outer layer is composed of multiple layers including the substrate layer by forming another layer on the outside and / or inside (barrier layer side) of the substrate layer.

[0056] Examples of layers formed on the outside of the base material layer include a protective layer and a matte coating layer. These layers serve as the outermost layer of the battery packaging material to protect the base material layer and also have the effect of imparting good slip properties to the surface, thereby improving formability.

[0057] As the material of the protective layer, phenoxy resin, urethane resin, epoxy resin, acrylic resin, polyolefin resin, fluorine resin, etc. are recommended. The matte coat layer is made of a resin composition in which a matting agent is blended with a resin, and as the matting agent, inorganic particles such as silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, calcium silicate, etc., resin beads such as acrylic beads, etc. are recommended.

[0058] The protective layer and matte coating layer can be formed by applying a liquid having its fluidity adjusted with a solvent to the base layer and drying it, or by laminating the layer as a film to the base layer.

[0059] An example of a layer formed inside the base material layer, i.e., a layer formed between the base material layer and the first adhesive layer (or between the base material layer and the barrier layer if the first adhesive layer is not present), is a colored layer. If the base material layer is transparent, the layer formed behind it can be seen through the base material layer, so by forming a colored layer inside the base material layer, it is possible to impart color (including achromatic colors) to the appearance of the battery packaging material. Note that in battery packaging materials on which the colored layer is not formed, the color of the metal foil that constitutes the barrier layer becomes the appearance color.

[0060] The colored layer can be a cured film of a colored ink composition containing a resin binder and a colored pigment. Examples of the resin binder include a two-component curing polyester urethane resin binder containing a polyester resin as a base and a polyfunctional isocyanate compound as a curing agent. Examples of the colored pigment include inorganic pigments such as carbon black, calcium carbonate, titanium oxide, zinc oxide, iron oxide, and aluminum powder, and organic pigments such as azo compounds, phthalocyanine compounds, and condensed polycyclic compounds. [Battery case and battery] The battery 2 in FIG. 2 is equipped with a battery case 30 made from the battery packaging material of the present invention.

[0061] The battery case 30 is produced by joining the sealant layers 20 of the battery packaging material 1 together with their inner surfaces facing inward, and heat-sealing the edges to form a battery element chamber 31 with the sealant layers 20 as the inner surface. Note that the partial enlarged view in Figure 2 omits the illustration of the first adhesive layer and second adhesive layer of the battery packaging material 1.

[0062] The battery 2 is provided in the battery element chamber 31 of the battery case 30 with a positive electrode, a negative electrode, and a Separator to be placed The battery 2 is fabricated by housing battery elements containing a battery cell and an electrolyte. The battery 2 is opened before the temperature reaches a temperature at which gas is generated by the battery elements, as the seal strength of the seal between the sealant 20 layers is reliably reduced, and the gas is safely released outside the case without increasing internal pressure, preventing the battery from exploding or catching fire.

[0063] The battery case 30 must maintain a seal strength that prevents it from being opened until it reaches a predetermined intended opening temperature, even when the battery temperature rises. When the intended opening temperature is 110°C to 130°C, the desirable seal strength of the edge of the battery chamber 31 is 60 N / 15 mm or more at room temperature, 25 N / 15 mm or more at 100°C, and 6 N / 15 mm to 12 N / 15 mm at 130°C. It is even more preferable if the seal strength at 130°C is 6 N / 15 mm to 10 N / 15 mm. [Example]

[0064] As Examples 1 to 7 and Comparative Examples 1 to 5, a sealant layer 20 having a three-layer structure and a battery packaging material 1 shown in FIG. 1 were produced.

[0065] Examples 1 to 7 and Comparative Examples 1 to 5 have the same materials, except for the material of the first sealant layer 21 of the sealant layer 20. The materials of the barrier layer 11, the base material layer 13, the first adhesive layer 12, and the second adhesive layer 14 are as follows.

[0066] The barrier layer 11 was prepared 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 a 35 μm-thick aluminum foil made of A8079, followed by drying at 150° C. The chromium deposition amount of this chemical conversion film was 5 mg / m per side. 2 is.

[0067] As the base layer 13, a biaxially oriented nylon 6 film having a thickness of 25 μm was used.

[0068] As the first adhesive layer 12, a two-component curing urethane adhesive was used.

[0069] As the second adhesive layer 14, a two-component curing maleic acid modified propylene adhesive was used. (Preparation of three-layer film for sealant layer) A sealant layer 20 in which a first sealant layer 21, a second sealant layer 22 and a third sealant layer 23 are laminated was produced by co-extrusion.

[0070] The first sealant layer 21 is made of a resin composition obtained by adding 1000 ppm of erucic acid amide as a lubricant and 2000 ppm of silica particles as an antiblocking agent to a mixture of an ethylene-propylene random copolymer and polyethylene. Whether or not a methacron catalyst was used in the polymerization process of the ethylene-propylene random copolymer is shown in Table 1. Table 1 also shows the weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw / Mn) of the ethylene-propylene copolymer used in each example, the melt flow rate (MFR) measured according to JIS K7210 (230°C / 2.16 kg load), and the melting point (°C) calculated by differential scanning calorimetry. The polyethylene content relative to the total of the ethylene-propylene random copolymer and polyethylene, and the content of metallocene-catalyzed polyethylene in the polyethylene, are also shown in Table 1.

[0071] The second sealant layer 22 is made of a resin composition in which 2500 ppm of erucic acid amide is added as a lubricant to an ethylene-propylene block copolymer.

[0072] The third sealant layer 23 is made of a resin composition in which 1000 ppm of erucic acid amide as a lubricant and 2000 ppm of silica particles as an antiblocking agent are added to an ethylene-propylene random copolymer.

[0073] The resin compositions constituting the first sealant layer 21, second sealant layer 22, and third sealant layer 23 were co-extruded to extrude a film with a three-layer structure. The thickness of each layer was 6 μm for the first sealant layer 21, 28 μm for the second sealant layer 22, and 6 μm for the third sealant layer 23, resulting in a sealant film with a total thickness of 40 μm. Each layer of the sealant layer 20 was an unstretched film.

[0074] An adhesive was then applied to one surface of the barrier layer 11 to form a 3 μm-thick first adhesive layer 12, and the base material layer 13 was dry-laminated, and an adhesive was applied to the other surface of the barrier layer 11 to form a 2 μm-thick second adhesive layer 14, and the third sealant layer 23 of the sealant layer 20 was dry-laminated together. Furthermore, this laminate sheet was dry-laminated by being sandwiched between a rubber nip roll and a laminating roll heated to 100°C and pressure-bonded, and then aged (heated) at 40°C for 10 days to obtain a battery packaging material 1 (see FIG. 1).

[0075] The battery packaging material was (25℃) The seal strength at three temperatures, 130°C and 100°C, was evaluated by the following method.

[0076] The test material for measuring the seal strength was prepared by cutting two test pieces of the battery packaging material 1 to a width of 15 mm and a length of 150 mm, joining the two test pieces with the sealant layers 20 facing inward, and heat sealing the two pieces by heating on one side using a heat sealing device (TP-701-A, manufactured by Tester Sangyo Co., Ltd.) under the following conditions: heat sealing temperature: 200°C, sealing pressure: 0.2 MPa (gauge display pressure), sealing time: 2 seconds. (room temperature strength) The seal strength was measured in accordance with JIS Z0238-1998 using a Strograph (AGS-5kNX) manufactured by Shimadzu Access Co., Ltd., when the sealant layers 20 of the sealed portions of the test material were T-peeled together at a tensile speed of 100 mm / min, and this was taken as the seal strength (N / 15 mm width).

[0077] For the room temperature seal temperature, the peel strength was measured using the method described above for the test material at room temperature. For the 130°C and 100°C seal strength, the test material was left to stand at each temperature for 24 hours, and then the peel strength was measured using the method described above under each temperature environment. The seal strength at each temperature is shown in Table 1.

[0078] [Table 1]

[0079] From Table 1, it was confirmed that the seal strength can be reduced at a desired temperature by specifying the properties of the outermost layer of the sealant layer. [Industrial Applicability]

[0080] The battery packaging material of the present invention can be suitably used as a case material for secondary batteries for in-vehicle, stationary, notebook computers, mobile phones, and cameras, particularly small, portable lithium-ion secondary batteries. [Explanation of symbols]

[0081] 1...Battery packaging material 11...Barrier layer 12...First adhesive layer 13...Base material layer 14...Second adhesive layer 20...Sealant layer 21...First sealant layer 22...Second sealant layer 23...Third sealant layer

Claims

1. A battery packaging material including a substrate layer as an outer layer, a sealant layer as an inner layer, and a barrier layer disposed between these two layers, The sealant layer is composed of a single layer or multiple layers, and the first sealant layer, which is the innermost layer, is composed of a propylene-based resin including an ethylene-propylene copolymer; The ethylene-propylene copolymer has a ratio Mw / Mn of weight average molecular weight Mw to number average molecular weight Mn measured by gel permeation chromatography (GPC) of 1 to 7, a melt flow rate measured in accordance with JIS K7210 at 230°C under a load of 2.16 kg of 5 g / 10 min to 30 g / 10 min, and a melting point calculated by differential scanning calorimetry of 120°C to 135°C.

2. 2. The battery packaging material according to claim 1, wherein the ethylene-propylene copolymer is a copolymer derived from a methacerone catalyst.

3. 3. The battery packaging material according to claim 1, wherein the propylene-based resin is a mixture of an ethylene-propylene copolymer and polyethylene, and the polyethylene content in the mixture is 7% by mass to 20% by mass.

4. 4. The battery packaging material according to claim 3, wherein 70% by mass or more of the polyethylene is polyethylene derived from a metallocene catalyst.

5. the sealant layer is a multilayer structure in which the first sealant layer, one or more second sealant layers, and a third sealant layer are laminated in this order from the inside of the battery packaging material toward the barrier layer side, the third sealant layer is made of an ethylene-propylene random copolymer, 5. The battery packaging material according to claim 1, wherein the melt flow rate of the resin constituting at least one of the second sealant layers is lower than the melt flow rate of the ethylene-propylene copolymer constituting the first sealant layer.

6. A battery case, characterized in that the battery packaging material according to any one of claims 1 to 5 is joined together with the sealant layers facing inward, and the edges are heat-sealed to form a battery element chamber for accommodating a battery element.

7. 7. The battery case according to claim 6, wherein the seal strength of the edge of the battery element chamber is 60 N / 15 mm or more at room temperature, 25 N / 15 mm or more at 100°C, and 6 N / 15 mm to 12 N / 15 mm at 130°C.

8. A battery comprising a battery element housed in a battery element chamber of the battery case according to claim 6 or 7.

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