Packaging material for a battery

Abstract

The present invention relates to a battery packaging material. The object is to provide a battery packaging material which is sealed at a temperature at which flammable gas is generated due to an electrolyte, and the seal strength is reduced and the case is opened. The battery packaging material (1) comprises a base material layer (13) as an outer layer, a sealing layer (20) as an inner layer, and a barrier layer (11) disposed between the two layers, the sealing layer (20) is formed by a single layer or multiple layers, the first sealing layer (21) as the innermost layer is composed of a propylene resin comprising an ethylene-propylene copolymer, for the ethylene-propylene copolymer, 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 melt flow rate measured based on JIS K7210 at 230°C under a load of 2.16 kg is 5 g / 10 minutes to 30 g / 10 minutes, and the melting point calculated from differential scanning calorimetry is 120°C to 135°C.

Description

Technical Field

[0001] This invention relates to battery packaging materials and related technologies suitable for use as casings for secondary batteries, such as those for vehicles, stationary batteries, laptops, mobile phones, and cameras, especially small portable lithium-ion secondary batteries. Background Technology

[0002] For energy storage devices, such as lithium-ion batteries, various shapes can be manufactured using laminated packaging materials, such as canisters, casings, and resin layers bonded to both sides of aluminum. Furthermore, thinness and lightweight designs are possible. In energy storage devices using laminated packaging materials, if the internal temperature of the battery rises with increasing capacity, gas is generated due to electrolyte evaporation, leading to increased internal pressure and potentially causing the casing to expand or rupture. Additionally, if the gas is flammable, there is a fire hazard. Therefore, measures have been taken to prevent rupture and ensure a smooth release of gas from the casing (see Patent Documents 1 and 2).

[0003] Patent document 1 describes a preventive measure based on the shell structure, which discloses a valve mechanism that reduces the pressure when the pressure inside the shell rises and a ventilation path that guides the gas inside the shell to the valve mechanism.

[0004] Patent document 2 describes a preventive measure based on the casing material, which discloses a heat-fusible resin layer (sealing layer) of a laminate material composed of a resin with a melting peak temperature of less than 130°C, thereby suppressing battery expansion and allowing the battery to be opened smoothly when exposed to high temperature environments.

[0005] [Existing Technical Documents]

[0006] [Patent Literature]

[0007] [Patent Document 1] Japanese Patent No. 6540871

[0008] [Patent Document 2] Japanese Patent Application Publication No. 2019-29300 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, the preventative measures described in Patent Document 1 require additional components such as valve mechanisms and venting paths, thus increasing both material and manufacturing costs. Furthermore, for the laminated material described in Patent Document 2, since the opening temperature is controlled by the melting peak temperature of the sealing layer, it needs to be designed to open in a low-temperature region to reliably open before rupture. Therefore, even at the practical temperature of a battery where no gas is generated, there is a possibility of opening.

[0011] Methods for solving problems

[0012] In view of the above-mentioned technical background, the present invention provides a battery packaging material in which the sealing strength decreases at temperatures caused by the generation of flammable gases due to electrolytes, allowing the casing to open.

[0013] That is, the present invention has the structure described in [1] to [8] below.

[0014] [1] A battery packaging material comprising a substrate layer as an outer layer, a sealing layer as an inner layer, and a barrier layer disposed between the two layers, characterized in that...

[0015] The sealing layer is formed of a single layer or multiple layers, and the innermost first sealing layer is composed of a propylene resin containing an ethylene-propylene copolymer.

[0016] For the ethylene-propylene copolymer, the weight-average molecular weight Mw to number-average molecular weight Mn ratio Mw / Mn determined by gel permeation chromatography (GPC) is 1 to 7, the melt flow rate determined based on JIS K7210 at 230°C and 2.16 kg load is 5 g / 10 min to 30 g / 10 min, and the melting point calculated by differential scanning calorimetry is 120°C to 135°C.

[0017] [2] The battery packaging material as described in item 1 above, wherein the ethylene-propylene copolymer is a copolymer derived from a metallocene catalyst.

[0018] [3] The battery packaging material as described in item 1 above, wherein the propylene resin is a mixture of ethylene-propylene copolymer and polyethylene, wherein the polyethylene content in the mixture is 7% to 20% by mass.

[0019] [4] The battery packaging material as described in item 3 above, wherein more than 70% by mass of the polyethylene is polyethylene derived from a metallocene catalyst.

[0020] [5] As described in item 1 above, the battery packaging material is a multilayer structure consisting of a first sealing layer, one or more second sealing layers, and a third sealing layer, sequentially stacked from the inside of the battery packaging material towards the barrier layer side.

[0021] The third sealing layer is formed of an ethylene-propylene random copolymer.

[0022] The melt flow rate of the resin constituting at least one layer of the second sealing layer is less than the melt flow rate of the ethylene-propylene copolymer of the first sealing layer.

[0023] [6] A battery casing, characterized in that it is formed by heat-sealing the edges of the battery packaging materials described in any one of the preceding items 1 to 5 in such a way that the sealing layers face each other inwards, thereby forming a battery element chamber for housing the battery element.

[0024] [7] The battery casing as described in item 6 above, wherein the sealing 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.

[0025] [8] A battery, characterized in that it is formed by housing battery elements in a battery element chamber of a battery casing as described in item 6 above.

[0026] Invention Effects

[0027] Regarding the battery packaging material described above [1], since the first sealing layer, which is the innermost sealing layer, is composed of an propylene resin containing an ethylene-propylene copolymer with specified characteristics, the sealing strength decreases sharply between 110°C and 130°C. When the battery temperature rises, gas is generated due to the evaporation of electrolyte, etc., and the pressure inside the casing rises around 130°C and begins to expand. However, for batteries using casings made of the aforementioned battery packaging material, the sealing strength can decrease at a temperature of 110°C to 130°C, which is lower than the temperature at which the casing begins to expand, thereby allowing the seal to be released and the gas to be released smoothly, thus preventing the casing from cracking and catching fire.

[0028] Regarding the battery packaging material described in [2] above, since the ethylene-propylene copolymer of the sealing layer is a copolymer derived from a metallocene catalyst, the sealing strength can be reduced at the target temperature.

[0029] Regarding the battery packaging material described in [3] above, since the sealing layer is made of propylene resin containing a specified amount of polyethylene, it has a significant effect on reducing the sealing strength at the target temperature.

[0030] Regarding the battery packaging material described in [4] above, since more than 70% by mass of the polyethylene in the propylene resin constituting the sealing layer is derived from a metallocene catalyst, it is easily dispersed in polypropylene, and the effect of controlling the temperature at which the sealing strength decreases to the target temperature is improved.

[0031] For the battery packaging material described above [5], the sealing layer is a multilayer of a first sealing layer, a second sealing layer and a third sealing layer. The third sealing layer is composed of an ethylene-propylene random copolymer, thereby obtaining a strong bonding force against the barrier layer. The second sealing layer is composed of a resin with a lower melt flow rate and a higher melting point than the ethylene-propylene copolymer of the first sealing layer, thereby enabling the sealing part between the first sealing layers to be opened.

[0032] According to the battery casing described in [6] above, the effects brought about by the above-mentioned battery packaging material can be obtained.

[0033] For the battery casing described above [7], the seal on the edge of the battery element chamber is released and opened at 110°C to 130°C.

[0034] According to the battery described in [8] above, the effects brought about by the above-mentioned battery packaging material can be obtained. Attached Figure Description

[0035] Figure 1 This is a cross-sectional view of an embodiment of the battery packaging material of the present invention.

[0036] Figure 2 To have the ability to be Figure 1 A cross-sectional view of a battery casing made of packaging materials.

[0037] [Explanation of reference numerals in the attached figures]

[0038] 1. Packaging materials for batteries

[0039] 11 barrier layers

[0040] 12 First adhesive layer

[0041] 13 Substrate Layer

[0042] 14 Second adhesive layer

[0043] 20 sealing layers

[0044] 21 First sealing layer

[0045] 22 Second sealing layer

[0046] 23 Third sealing layer Detailed Implementation

[0047] Figure 1 An embodiment of the battery packaging material of the present invention is shown in the figure.

[0048] [Battery Packaging Materials]

[0049] In the battery packaging material 1, a substrate layer 13 is bonded to one side of the barrier layer 11 via a first adhesive layer 12, and multiple layers of sealing layers 20 are bonded to the other side via a second adhesive layer 14. For the battery packaging material 1, a battery casing is formed by heat-sealing the perimeter of the battery packaging material 1 by arranging the sealing layers 20 opposite to each other. In the formed battery casing, the substrate layer 13 serves as the outer layer, and the sealing layers 20 serve as the inner layer.

[0050] [Sealing layer of battery packaging material]

[0051] The battery packaging material of the present invention is characterized by the material of the sealing layer that serves as the inner layer. The sealing layer exhibits excellent chemical resistance even against highly corrosive electrolytes, and simultaneously imparts heat-sealing properties to the laminated material. The sealing layer can be a single layer or multiple layers, and the material of the innermost first sealing layer, which is the layer in contact with the opposing battery packaging materials during heat sealing, is specified as follows.

[0052] The sealing layer 20 shown in the figure is a three-layer structure formed by stacking the first sealing layer 21, the second sealing layer 22, and the third sealing layer 23 sequentially from the inside of the battery packaging material 1 towards the barrier layer 11. The third sealing layer 23 is in contact with the second adhesive layer 14, and the second sealing layer 22 is an intermediate layer between the first sealing layer 21 and the third sealing layer 23.

[0053] The first sealing layer 21 is composed of a resin (as an propylene-based resin) that contains at least an ethylene-propylene copolymer containing ethylene and propylene as copolymer components.

[0054] The ethylene-propylene copolymer can be any of random copolymers, block copolymers, or block copolymers, but it must meet the following three conditions as a required characteristic.

[0055] (1) The ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn) as determined by gel permeation chromatography (GPC), Mw / Mn, is 1 to 7. Preferably, Mw / Mn is 1.2 to 3.5, more preferably 1.5 to 2.8.

[0056] (2) The melt flow rate (MFR) measured according to JIS K7210 at 230℃ and 2.16kg load is 5g / 10min to 30g / 10min. The preferred melt flow rate (MFR) is 5g / 10min to 10g / 10min.

[0057] (3) The melting point calculated by differential scanning calorimetry is 120℃~135℃. The preferred melting point is 122℃~133℃.

[0058] The ethylene-propylene copolymer that meets the above three conditions experiences a decrease in sealing strength between 110°C and 130°C, making the seal easier to release, while maintaining sealing strength at temperatures below this range. When the battery temperature rises, gas is generated due to electrolyte evaporation, causing the internal pressure of the battery to rise around 130°C, and the casing to begin expanding. The temperature range where the sealing strength decreases is above the intended battery operating temperature range but below the temperature at which expansion begins. Therefore, when the battery temperature rises rapidly and the internal pressure begins to rise due to gas generation, the seal breaks and the casing is opened. When the casing is opened, the gas is released smoothly, preventing casing rupture and fire.

[0059] The ethylene-propylene copolymer that meets the above three conditions can be obtained, for example, by copolymerizing ethylene and propylene as copolymerizing components using a metallocene catalyst. Ethylene-propylene copolymers derived from metallocene catalysts tend to have high molecular weight uniformity, meet the above three conditions, and significantly reduce sealing strength at the target temperature.

[0060] Furthermore, the propylene-based resin is a mixture of ethylene-propylene copolymer and polyethylene, wherein the polyethylene content in the mixture is preferably 7% to 20% by mass. By setting the polyethylene content within the above range, the effect of reducing the sealing strength at the target temperature is significant. A particularly preferred ethylene content is 10% to 15% by mass. Further, 70% or more of the polyethylene is preferably polyethylene derived from a metallocene catalyst obtained by polymerization using a metallocene catalyst. Polyethylene derived from a metallocene catalyst is easily dispersed in polypropylene, thereby improving the effect of controlling the temperature at which the sealing strength decreases to the target temperature. A particularly preferred content of polyethylene derived from a metallocene catalyst is 85% or more by mass.

[0061] It is preferable to add lubricant and anti-adhesion agent to the first sealing layer 21.

[0062] As a lubricant, there are no particular limitations, and examples include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, hydroxymethyl amides, saturated fatty acid diamides, unsaturated fatty acid diamides, fatty acid ester amides, and aromatic diamides.

[0063] The saturated fatty acid amide is not particularly limited, and examples include lauryl amide, palmitamide, stearamide, benzyl amide, hydroxystearamide, etc.

[0064] The unsaturated fatty acid amide is not particularly limited, and examples include oleamide and erucamide.

[0065] The substituted amide is not particularly limited, and examples include N-oleyl palmitamide, N-stearyl stearamide, N-stearyl oleamide, N-oleyl stearamide, and N-stearyl erucamide.

[0066] The hydroxymethylamide is not particularly limited, and examples include hydroxymethylstearamide, etc.

[0067] The saturated fatty acid diamide is not particularly limited, and examples include methylene bis-stearamide, ethylene bis-decanoic acid amide, ethylene bis-lauric acid amide, ethylene bis-stearamide, ethylene bis-hydroxystearamide, ethylene bis-sorbic acid amide, hexamethylene bis-stearamide, hexamethylene bis-sorbic acid amide, hexamethylene hydroxystearamide, N,N'-distearate adipamide, N,N'-distearate sebacate amide, etc.

[0068] The unsaturated fatty acid diamide is not particularly limited, and examples include ethylene dioleamide, ethylene dierucamide, hexamethylene dioleamide, and N,N'-dioleenyl sebacate amide.

[0069] The fatty acid ester amide is not particularly limited, and examples include, for example, ethyl stearamide.

[0070] The aromatic diamide is not particularly limited, and examples include m-xylene-distearamide, m-xylene-dihydroxystearamide, and N,N'-distearate-isophthalamide.

[0071] The lubricant concentration in the first sealing layer 21 is preferably in the range of 100 ppm to 3000 ppm. If the lubricant concentration is less than 100 ppm, the moldability is insufficient, while adding 3000 ppm sufficiently improves the moldability. Therefore, adding large amounts exceeding this concentration is not ideal in terms of cost. A particularly preferred lubricant concentration is 500 ppm to 2000 ppm.

[0072] The anti-blocking agent is not particularly limited, and examples include particles of silica, acrylic resin, aluminum silicate, calcium carbonate, barium carbonate, titanium dioxide, talc, kaolin, etc. Regarding the particle size of the anti-blocking agent, it is preferably in the range of 0.1 μm to 10 μm in terms of average particle size, and more preferably in the range of 1 μm to 5 μm in terms of average particle size. The concentration of the anti-blocking agent is preferably set to 100 ppm to 5000 ppm, and particularly preferably 500 ppm to 4000 ppm.

[0073] By including the anti-adhesion agent (particles) in the first sealing layer 21 of the sealing layer 20 of the battery packaging material 1, tiny protrusions can be formed on the surface of the first sealing layer 21, thereby reducing the contact area between the films and suppressing adhesion between the sealing films. Furthermore, by including the anti-adhesion agent (particles) along with the lubricant, the sliding properties during molding can be further improved.

[0074] When the sealing layer is a single layer, it is a single layer of the first sealing layer 21 mentioned above.

[0075] When the sealing layer 20 is multi-layered, the preferred materials for the layers other than the first sealing layer 21 are as follows. It should be noted that the present invention does not limit the materials of the layers other than the first sealing layer 21.

[0076] For the third sealing layer 23, examples include ethylene-propylene copolymers and ethylene-propylene random copolymers with the same composition as the first sealing layer 21. Furthermore, since the third sealing layer 23 is used together with the second adhesive layer 14 to improve the adhesion between the barrier layer 11 and the sealing layer 20, it is preferable not to add lubricants or anti-blocking agents. However, from the viewpoint of ensuring the stability of the sealing layer 20 during film formation and preventing adhesion after winding the sealing layer 20, erucamide at 1000 ppm or less can be added as a lubricant and silica particles at 2000 ppm or less as an anti-blocking agent.

[0077] The second sealing layer 22 is an intermediate layer between the first sealing layer 21 and the third sealing layer 23. It can be any homopolymer of propylene, a copolymer containing propylene and other copolymer components in its copolymer composition, or a mixture of multiple polymers. Furthermore, when the same propylene-based resin as the first sealing layer 21 is mixed in, the adhesion between the second sealing layer 22 and the first sealing layer 21 improves. Additionally, the second sealing layer 22 can be any single layer or multiple layers.

[0078] The sealing layer 20 in the example diagram has a three-layer structure and can be obtained by producing a multilayer film using materials co-extruded from each layer. Furthermore, the sealing layer 20 is preferably a non-stretched film.

[0079] The thickness of the sealing layer 20 is preferably in the range of 20μm to 100μm, and more preferably 25μm to 85μm. Furthermore, in the example of the three-layer structure of the sealing layer 20 (including the case where the second sealing layer is multi-layered), the preferred thickness ratio of each layer is: first sealing layer 21: second sealing layer 22: third sealing layer 23 = 1–3: 4–8: 1–3.

[0080] When the sealing layer 20 is multi-layered, it is preferable to design the sealing layer 20 such that the casing is opened at the seal between the first sealing layers 21 of the two heat-sealed battery packaging materials 1, so that peeling within the sealing layer 20 does not occur before the seal between the first sealing layers 21 is released. If interlayer peeling occurs within the sealing layer 20, there is a possibility that gases generated inside the battery at high temperatures may become difficult to escape. Specifically, it is preferable that the third sealing layer 23 is composed of an ethylene-propylene random copolymer, and the second sealing layer 22 is composed of a resin with a melt flow rate lower than that of the ethylene-propylene copolymer of the first sealing layer 21 and a high melting point (at least one of them if the second sealing layer is multi-layered). By using an ethylene-propylene random copolymer to form the third sealing layer 23, a strong bonding force against the barrier layer 11 is obtained. Furthermore, the preferred characteristics of the material constituting the second sealing layer 22 are: a melt flow rate of 2 g / 10 min to 7 g / 10 min as measured by JIS K7210 at 230°C and a load of 2.16 kg, 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 three layers of material in this way, the casing is opened between the first sealing layer 21 of the sealing layers 20 of the two battery packaging materials 1.

[0081] [The layer outside the sealing layer of the battery packaging material]

[0082] In the battery packaging material of the present invention, the layers other than the sealing layer can be made of known materials, and the bonding method is not particularly limited. Preferred materials for the layers other than the sealing layer will be described below.

[0083] (Substrate layer)

[0084] For the substrate layer 13, a heat-resistant resin film that does not melt at the heat-sealing temperature when heat-sealing the battery packaging material 1 is used. As the heat-resistant resin, a heat-resistant resin having a melting point at least 10°C higher, preferably at least 20°C higher, than the resin constituting the sealing layer 20 is used. Examples of resins meeting this condition include, for example, polyamide films such as nylon films, polyester films, etc., and preferably stretched films of these. Particularly preferred materials for the substrate layer 13 are 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. The nylon film is not particularly limited, and examples include, for instance, nylon 6 films, nylon 6,6 films, and nylon MXD films. It should be noted that the substrate layer 13 can be formed by a single layer, or by a multilayer formed by, for example, polyester film / polyamide film (multilayer formed by PET film / nylon film, etc.).

[0085] The thickness of the substrate layer 13 is preferably 7μm to 50μm, which ensures sufficient strength as a packaging material and reduces stress during molding processes such as bulging and deep drawing, thereby improving formability. A further preferred thickness of the substrate layer 13 is 9μm to 30μm.

[0086] (Barrier layer)

[0087] The barrier layer 11 serves to provide gas barrier properties that prevent the intrusion of oxygen and moisture into the battery packaging material 1. The barrier layer 11 is not particularly limited and can be made of metal foils such as aluminum foil, SUS foil (stainless steel foil), copper foil, nickel foil, titanium foil, or coated foil. The thickness of the barrier layer 11 is preferably 20 μm to 100 μm. By making the thickness 20 μm or more, pinholes can be prevented during rolling when manufacturing the metal foil, and by making the thickness 100 μm or less, the stress during forming processes such as embossing and deep drawing can be reduced, thereby improving formability. A particularly preferred thickness of the barrier layer 11 is 25 μm to 85 μm.

[0088] Furthermore, for the barrier layer 11, it is preferable to perform a surface treatment such as chemical conversion treatment on at least the surface of the metal foil on the sealing layer 20 side. By performing such a chemical conversion treatment, corrosion of the metal foil surface caused by the contents (such as the electrolyte of the battery) can be effectively prevented.

[0089] (First adhesive layer)

[0090] The first adhesive layer 12 is not particularly limited, and examples include adhesive layers formed using a two-component curing adhesive. Examples of the two-component curing adhesive include a first liquid (main agent) and a second liquid (curing agent) containing an isocyanate, wherein the first liquid (main agent) contains one or more polyols selected from the group consisting of polyurethane-based polyols, polyester-based polyols, polyether-based polyols, and polyester-polyurethane-based polyols. Preferably, a two-component curing adhesive is used, consisting of a first liquid containing one or more polyols selected from the group consisting of polyester-based polyols and polyester-polyurethane-based polyols, and a second liquid (curing agent) containing an isocyanate. The preferred thickness of the first adhesive layer 12 is 2 μm to 5 μm.

[0091] (Second adhesive layer)

[0092] The second adhesive layer 14 is not particularly limited, and examples include one or more adhesives selected from polyurethane resins, acrylic resins, epoxy resins, polyolefin resins, elastic resins, fluorinated resins, and acid-modified polypropylene resins. Adhesives comprising polyurethane composite resins with acid-modified polyolefins as the main agent are preferred. The preferred thickness of the second adhesive layer 14 is 2 μm to 5 μm.

[0093] (Other layering methods for battery packaging materials)

[0094] In the battery packaging material of the present invention, the first adhesive layer and the second adhesive layer are not necessary layers, the substrate layer can be directly bonded to the barrier layer, and the sealing layer can also be directly bonded to the barrier layer.

[0095] In addition, the battery packaging material of the present invention may form other layers on the outer side and / or inner side (barrier layer side) of the substrate layer, and the outer layer is composed of multiple layers including the substrate layer.

[0096] Examples include protective layers and matte coatings formed on the outside of the substrate layer. These layers form the outermost layer of the battery packaging material and protect the substrate layer, and also improve formability by providing good surface smoothness.

[0097] Examples of materials that can be used as the protective layer include phenoxy resins, polyurethane resins, epoxy resins, acrylic resins, polyolefin resins, and fluorinated resins. Furthermore, the matte coating is formed from a resin composition in which a matting agent is incorporated, and examples of the above-mentioned resins and inorganic particles such as silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, and calcium silicate, as well as resin beads such as acrylic beads, can be used as the matting agent.

[0098] The protective layer and matte coating can be formed by applying a liquid with solvent-adjusted flowability onto a substrate layer and allowing it to dry, or by adhering it as a film onto the substrate layer.

[0099] A coloring layer can be exemplified as a layer formed inside the substrate layer, that is, between the substrate layer and the first adhesive layer (or between the substrate layer and the barrier layer if the first adhesive layer is absent). When the substrate layer is transparent, since the layer formed inside it can be seen through the substrate layer, forming a coloring layer inside the substrate layer allows for the imparting of color (including achromatic) to the appearance of the battery packaging material. It should be noted that for battery packaging materials without the coloring layer, the color of the metal foil constituting the barrier layer becomes the appearance color.

[0100] Examples of coloring layers include cured films of coloring ink compositions incorporating coloring pigments into resin binders. Examples of resin binders include two-component curing polyester polyurethane resin binders based on a polyester resin as the main agent and a polyfunctional isocyanate compound as the curing agent. Examples of coloring pigments include inorganic pigments such as carbon black, calcium carbonate, titanium dioxide, zinc oxide, iron oxide, and aluminum powder, as well as organic pigments such as azo compounds, phthalocyanine compounds, and fused polycyclic aromatic hydrocarbons.

[0101] [Battery casing and battery]

[0102] Figure 2 The battery 2 has a battery casing 30 made of the battery packaging material of the present invention.

[0103] The battery casing 30 is manufactured as follows: by heat-sealing the edges of the sealing layers 20 of the battery packaging material 1 together with their inward-facing surfaces, a battery element chamber 31 is formed with the sealing layers 20 as its inner surface. It should be noted that... Figure 2 The enlarged view in the image omits illustrations of the first and second adhesive layers of the battery packaging material 1.

[0104] Furthermore, battery 2 is manufactured by housing a battery element, including a positive electrode, a negative electrode, a separator disposed between the positive and negative electrodes, and an electrolyte, within the battery element chamber 31 of the battery casing 30. For battery 2, before reaching the temperature at which gas is generated by the battery element, it reliably reduces the sealing strength of the sealing portion between the sealing layers 20 to open, safely releasing gas to the outside of the casing without increasing internal pressure, thus preventing battery rupture and fire.

[0105] For the battery casing 30, it is necessary to maintain an unopenable seal strength even as the battery temperature rises until a predetermined opening temperature is reached. When the predetermined opening temperature is 110°C to 130°C, the ideal seal strength at the edge of the battery element 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. A more preferred seal strength at 130°C is 6 N / 15 mm to 10 N / 15 mm.

[0106] In Examples 1-7 and Comparative Examples 1-5, preparations were made Figure 1 The three-layer structure shown includes the sealing layer 20 and the battery packaging material 1.

[0107] For Examples 1-7 and Comparative Examples 1-5, only the material of the first sealing layer 21 of the sealing layer 20 is different, while the other materials are common. The materials of the barrier layer 11, the substrate layer 13, the first adhesive layer 12, and the second adhesive layer 14 are shown below.

[0108] The following layer is used as barrier layer 11: A chemical conversion treatment solution containing polyacrylic acid (acrylic resin), chromium (III) salt compound, water, and alcohol is coated on both sides of an aluminum foil with a thickness of 35 μm formed of A8079, and then dried at 150°C to form a chemical conversion coating. The chromium deposition of this chemical conversion coating is 5 mg / m² per side. 2 .

[0109] A biaxially stretched nylon 6 film with a thickness of 25 μm was used as the substrate layer 13.

[0110] A two-component curable polyurethane adhesive is used as the first adhesive layer 12.

[0111] A two-component curing maleic acid-modified propylene adhesive is used as the second adhesive layer 14.

[0112] (Fabrication of a 3-layer membrane for sealing layer)

[0113] A sealing layer 20, consisting of a first sealing layer 21, a second sealing layer 22, and a third sealing layer 23, is produced by co-extrusion.

[0114] The first sealing layer 21 is formed from a resin composition in which 1000 ppm of erucamide is added as a lubricant and 2000 ppm of silica particles as an anti-blocking agent to a mixture of ethylene-propylene random copolymer and polyethylene. The use of a metallocene catalyst in the polymerization process of the ethylene-propylene random copolymer is shown in Table 1. Furthermore, the weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw / Mn), melt flow rate (MFR) measured based on JIS K7210 (230°C / 2.16 kg load), and melting point (°C) calculated by differential scanning calorimetry for each example of the ethylene-propylene random copolymer used are shown in Table 1. Additionally, the content of polyethylene relative to the total of the ethylene-propylene random copolymer and polyethylene, and the content of polyethylene derived from the metallocene catalyst in that polyethylene, are shown in Table 1.

[0115] The second sealing layer 22 is formed from a resin composition in which 2500 ppm of erucamide is added as a lubricant in an ethylene-propylene block copolymer.

[0116] The third sealing layer 23 is formed from a resin composition in which 1000 ppm of erucamide as a lubricant and 2000 ppm of silica particles as an anti-blocking agent are added to an ethylene-propylene random copolymer.

[0117] The resin composition constituting the first sealing layer 21, the second sealing layer 22, and the third sealing layer 23 described above was co-extruded to obtain a three-layer film. The thickness of each layer is 6 μm for the first sealing layer 21, 28 μm for the second sealing layer 22, and 6 μm for the third sealing layer 23, resulting in a sealing film with a total thickness of 40 μm. It should be noted that each layer of the sealing layer 20 is an unstretched film.

[0118] Subsequently, an adhesive is applied to one side of the barrier layer 11 to form a first adhesive layer 12 with a thickness of 3 μm, the substrate layer 13 is dry-laminated, and an adhesive is applied to the other side of the barrier layer 11 to form a second adhesive layer 14 with a thickness of 2 μm. The third sealing layer 23 of the sealing layer 20 is then dry-laminated together. Further, the laminated sheet is dry-laminated by pressing it between a rubber roller and a laminating roller heated to 100°C, and then aged (heated) at 40°C for 10 days to obtain battery packaging material 1 (see...). Figure 1 ).

[0119] The sealing strength of the battery packaging material was evaluated under three temperature conditions: room temperature (25℃), 130℃, and 100℃, using the following methods.

[0120] The test material for measuring the sealing strength is prepared as follows: Two test pieces are prepared by cutting the battery packaging material 1 into pieces 15mm wide and 150mm long. The two test pieces are joined together with the sealing layer 20 facing inwards, and heat-sealed by heating one side using a heat-sealing device (TESTER SANGYO Co., Ltd., TP-701-A) at a heat-sealing temperature of 200°C, a sealing pressure of 0.2MPa (gauge pressure), and a sealing time of 2 seconds.

[0121] (Standard temperature strength)

[0122] For sealing strength, according to JIS Z0238-1998 and using the STROGRAPH (AGS-5kNX) manufactured by Shimadzu Access, the peel strength of the sealing layer 20 of the sealing part of the test material was measured when it was T-shaped peeled off from each other at a tensile speed of 100 mm / min, and this was taken as the sealing strength (N / 15 mm width).

[0123] For sealing at room temperature, the peel strength of the test material at room temperature was determined using the method described above. Furthermore, for sealing strength at 130°C and 100°C, the test material was allowed to stand for 24 hours at its respective temperature, and then the peel strength was determined using the method described above at its respective temperature. The sealing strength under each temperature condition is shown in Table 1.

[0124] [Table 1]

[0125]

[0126] Table 1 confirms that by specifying the characteristics of the outermost layer of the sealing layer, the sealing strength can be reduced under the desired temperature conditions.

[0127] This application claims priority to Japanese Patent Application No. 2020-139411, filed on August 20, 2020, and Japanese Patent Application No. 2021-110499, filed on July 2, 2021, the disclosures of which directly constitute a part of this application.

[0128] The terms and expressions used herein are for illustrative purposes and not for limiting interpretation, and do not exclude any equivalents of the features disclosed and described herein, and should be understood to allow for various modifications within the scope claimed by the invention.

[0129] [Industry availability]

[0130] The battery packaging material of the present invention can be suitably used as a casing material for secondary batteries for vehicles, stationary batteries, laptops, mobile phones, and cameras, especially for small portable lithium-ion secondary batteries.

Claims

1. A battery packaging material comprising a substrate layer as an outer layer, a sealing layer as an inner layer, and a barrier layer disposed between the two layers, characterized in that, The sealing layer is formed of a single layer or multiple layers, and the innermost first sealing layer is composed of a propylene resin containing an ethylene-propylene copolymer. For the ethylene-propylene copolymer, the weight-average molecular weight (Mw) to number-average molecular weight (Mn) ratio (Mw / Mn) determined by gel permeation chromatography (GPC) is 1~7, the melt flow rate determined based on JIS K7210 at 230℃ and 2.16 kg load is 5 g / 10 min~30 g / 10 min, and the melting point calculated by differential scanning calorimetry is 120℃~135℃. The ethylene-propylene copolymer is a copolymer derived from a metallocene catalyst. The propylene resin is a mixture of ethylene-propylene copolymer and polyethylene, wherein the polyethylene content in the mixture is 7% to 20% by mass. 65-95% by mass of the polyethylene is polyethylene derived from a metallocene catalyst.

2. The battery packaging material as described in claim 1, wherein, 70-95% by mass of the polyethylene is polyethylene derived from a metallocene catalyst.

3. The battery packaging material as described in claim 1, wherein, The sealing layer is a multi-layered structure consisting of a first sealing layer, one or more second sealing layers, and a third sealing layer, sequentially stacked from the inside of the battery packaging material towards the barrier layer side. The third sealing layer is formed of an ethylene-propylene random copolymer. The melt flow rate of the resin constituting at least one layer of the second sealing layer is less than the melt flow rate of the ethylene-propylene copolymer of the first sealing layer.

4. A battery casing, characterized in that, It is formed by heat-sealing the edges of the battery packaging materials according to any one of claims 1 to 3 with the sealing layers facing each other inward, thereby forming a battery element chamber for housing battery elements.

5. The battery casing as described in claim 4, wherein, The sealing strength of the edge of the battery element chamber is above 60 N / 15 mm at room temperature, above 25 N / 15 mm at 100°C, and between 6 N / 15 mm and 12 N / 15 mm at 130°C.

6. A battery, characterized in that, It is formed by housing the battery element in the battery element chamber of the battery casing as described in claim 4.

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