Battery packaging materials and battery cases

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 two or more layers, and includes a first sealant layer 21 arranged on the innermost side of the sealant layer 20A, and a second sealant layer laminated on the outer surface of the first sealant layer 21. A resin constituting the first sealant layer 21 is a resin containing a propylene random copolymer having an MFR (230°C / load of 2.16 kg) obtained by JIS K 7210-2 (2014) of 3 g / 10 min to 10 g / 10 min. A resin constituting the second sealant layer 22 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, for example, as cases for secondary batteries for in-vehicle use, stationary use, notebook computers, mobile phones, cameras, and particularly small-sized portable lithium-ion secondary batteries.

Background Art

[0002] Power storage devices represented by lithium-ion secondary batteries can be processed into various shapes by using a laminate-type packaging material in which resin layers are laminated on both sides of aluminum from cans or cases, and can be further made thinner and lighter. In a power storage device using a laminate material as a packaging material, when the temperature inside the battery rises with the increase in the capacity of the device, gas is generated due to volatilization of the electrolyte or the like, the internal pressure rises, the case expands, and in some cases, it ruptures. In addition, there is also a risk of ignition if it is a flammable gas. For this reason, measures are taken to prevent rupture and gently release gas in the case of the power storage device (see Patent Documents 1 to 3).

[0003] As a safety standard for ignition, for example, there is JIS C8714(2007) "Safety Tests for Single Cells and Battery Packs of Lithium-Ion Batteries for Portable Electronic Devices". This safety test ensures the safety of the battery by raising the temperature from 5±2°C to 130°C±2°C and holding it for 10 minutes to confirm that ignition and rupture do not occur. The battery that has passed the above safety test has its case seal portion not peeled off within the normal use temperature range, ensuring safety. On the other hand, when the temperature rises excessively, the gas generated from the battery body increases the internal pressure of the case, but when it exceeds a certain temperature, the seal portion peels off and the case is opened, and the gas can escape outside the case to prevent the case from rupturing due to the increase in internal pressure.

[0004] The power storage device of Patent Document 1 is a preventive measure based on the structure of the case, and includes a valve mechanism that reduces the pressure when the internal pressure of the case rises, and a ventilation path that guides the gas inside the case to the valve mechanism.

[0005] Patent documents 2 and 3 mentioned above relate to techniques for opening the seal portion of a battery case at high temperatures by defining the packaging material for the battery. Reference document 2 describes a technique for opening the seal when exposed to a high-temperature environment of about 90°C to 120°C by defining the melting peak temperature of the heat-fusible resin layer (sealant layer). Reference document 3 describes a technique for opening the seal at high temperatures by defining the heat seal strength between heat-fusible 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 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, the preventative measures described in Patent Document 1 require additional components such as valve mechanisms and vents, which increases both material and manufacturing costs. Patent Documents 2 and 3 do not require additional components such as valve devices, but they have the problem that exposure to high temperatures can reduce the seal strength, causing the seal to open rapidly and potentially releasing a large amount of gas instantaneously.

[0008] This invention has been made in view 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 rises, causing the sealed portion to open slowly. [Means for solving the problem]

[0009] To achieve the above objective, the present invention has the following means.

[0010] [1] A battery packaging material comprising a base layer as an outer layer, a sealant layer as an inner layer, and a barrier layer disposed between these two layers, The sealant layer consists of two or more layers, and includes a first sealant layer located on the innermost part of the sealant layer, and a second sealant layer laminated on the outer surface of the first sealant layer. The resin constituting the first sealant layer is a resin containing a propylene random copolymer having an MFR (230℃ / 2.16kg load) of 3g / 10min to 10g / 10min obtained according to JIS K7210-2(2014), The battery packaging material is characterized in that the resin constituting the second sealant layer contains a polybutene copolymer A which includes 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 aforementioned 2 The battery packaging material according to item 1 above, wherein the resin constituting the sealant layer contains 30% to 50% by mass of the polybutene copolymer A and 50% to 70% by mass of the propylene random copolymer.

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

[0013] [4] The battery packaging material according to any one of items 1 to 3 above, wherein the thickness of the first sealant layer is 2 μm to 5 μm.

[0014] [5] The sealant layer has a multilayer structure including a fourth sealant layer closest to the barrier layer and a third sealant layer provided between the second and fourth sealant layers. The battery packaging material according to any one of the preceding paragraphs 1 to 4, wherein the third sealant layer is a polypropylene resin containing a propylene block copolymer and a propylene random copolymer.

[0015] [6] The sealant layer includes a fourth sealant layer closest to the barrier layer, The battery packaging material according to any one of the preceding paragraphs 1 to 5, wherein the fourth sealant layer comprises a propylene random copolymer having a higher melting point than the second sealant layer.

[0016] [7] A battery packaging material according to any one of items 1 to 6 above, wherein, when the sealant layers are heat-sealed to each other, the seal strength at the heat-sealed portion in a 100°C environment is 20 N / 15 mm width or more.

[0017] [8] A battery case formed by heat-sealing the sealant layers of the battery packaging material described in any one of paragraphs 1 to 6 above, A battery case characterized by having a heat-sealed portion with a sealing strength of 20 N / 15 mm width or more at a 100°C environment. [Effects of the Invention]

[0018] According to the battery packaging material of the invention [1], since the first sealant layer is a resin containing a propylene random copolymer with a specific MFR and the second sealant layer is a resin containing polybutene copolymer A containing a butene-1 component, when the sealant layers are heat-sealed to each other, the first and second sealant layers form a heat-welded part. In this heat-sealed part, since the second sealant layer contains polybutene copolymer A containing a butene-1 component, the side chain becomes bulkier compared to polypropylene and polyethylene, and the effect of lowering the crystallinity of the resin due to steric hindrance occurs, resulting in a lower melting point. Therefore, when the temperature of the battery case manufactured by heat-sealing the sealant layers rises excessively, when the gas generated in the battery body inside the case accumulates and the internal pressure rises, the low-melting-point component softens due to the temperature rise, the seal strength decreases, and the seal part is gradually unsealed, so that the gas inside the battery case can be efficiently released to the outside, and problems such as rupture of the packaging material due to the increase in the internal pressure of the battery case can be prevented. In addition, since the second sealant layer is easily softened, in a high-temperature environment, although it is likely to cause stickiness and blocking of the battery packaging material, since the first sealant layer with a specific MFR is arranged inside the second sealant layer, during heat-sealing, while sufficiently ensuring the fluidity of the resins of the first and second sealant layers, the flow of the resin of the second sealant layer can be appropriately suppressed in a high-temperature environment, and the occurrence of the above-mentioned stickiness and blocking can be prevented.

[0019] According to the battery packaging material of the invention [2], since the content of polybutene copolymer A and the content of propylene random copolymer of the resin constituting the second sealant layer are specified within a defined range, while preventing accidental peeling of the seal part at low temperatures, when the internal pressure rises due to excessive temperature rise, the seal part can be appropriately unsealed and the gas inside the battery case can be reliably released to the outside, and problems such as rupture of the packaging material due to the increase in the internal pressure of the battery case can be more reliably prevented.

[0020] According to the battery packaging material of Invention [3], since the melting point of the polybutene copolymer A contained in the second sealant layer is 120°C or lower, it becomes easier to control the melting point of the second sealant layer. The second sealant layer of the battery packaging material can be surely fused with the first sealant layer to fabricate a battery case, and the gas in the battery case can be released more efficiently during overheating.

[0021] According to the battery packaging material of Invention [4], since the thickness of the first sealant layer is specified, it is possible to more surely suppress the occurrence of stickiness and blocking due to the second sealant layer in a high-temperature environment. On the other hand, during heat sealing, the first sealant layer can be heat-sealed without problems together with the second sealant layer, and the gas inside the battery case can be released more efficiently to the outside during overheating.

[0022] According to the battery packaging material of Invention [5], since the third sealant layer contains a heat-resistant block copolymer, when fabricating a battery case, the third sealant layer exists while leaving a sufficient space (layer thickness) during heat sealing. The insulation can be surely maintained due to the residue of the third sealant layer, and only the first and second sealant layers can be surely fused. When the internal pressure rises due to overheating, the desired gas discharge function can be appropriately exerted in a relatively low-temperature region, and problems due to the increase in the internal pressure of the battery case can be more surely prevented.

[0023] According to the battery packaging material of Invention [6], since the fourth sealant layer has a higher melting point than the second sealant layer, the first and second sealant layers can be more reliably heat-fused before the fourth sealant layer melts during sealing. As a result, insulation can be more reliably maintained by the residual fourth sealant layer, and only the first and second sealant layers can be more reliably fused, further preventing problems caused by increased internal pressure in the battery case. Furthermore, since the fourth sealant layer contains a propylene random copolymer, there is less elastomer component, making it less likely for voids to occur, and the structure has less steric hindrance, resulting in better adhesion with the adhesive layer. This prevents electrolyte erosion even if liquid entrapment occurs during heat sealing, prevents delamination at the interface between adhesive layers, for example, between the adhesive layer and the metal foil, or between the adhesive layer and the sealant layer, and increases the likelihood of delamination occurring reliably between sealant layers when the temperature rises too high, thus preventing problems caused by increased internal pressure in the battery case.

[0024] According to the battery packaging material of invention [7] and the battery case of invention [8], the sealing portion can reliably maintain an appropriate sealing state until it reaches a predetermined overheating temperature range, and can prevent the sealing portion from peeling off unintentionally at low temperatures. [Brief explanation of the drawing]

[0025] [Figure 1] Figure 1 is a cross-sectional view showing an example of the battery packaging material of the present invention. [Figure 2] Figure 2 is a cross-sectional view showing another example of the battery packaging material of the present invention. [Figure 3] Figure 3 is a cross-sectional view showing yet another example of the battery packaging material of the present invention. [Figure 4] Figure 4 is a cross-sectional view of a battery equipped with a battery case made from the battery packaging materials shown in Figures 1 to 3. [Figure 5] Figure 5 is a cross-sectional view showing an enlarged view of the area enclosed by the dashed line in Figure 4. [Modes for carrying out the invention]

[0026] Figures 1-3 show three embodiments of the battery packaging material of the present invention.

[0027] In the following explanation, layers with the same reference numeral represent the same or equivalent material, and redundant explanations are omitted.

[0028] In battery packaging materials 1, 2, and 3, a base material layer 13 is bonded to one side (outer surface) of a barrier layer 11 via a first adhesive layer 12, and sealant layers 20A, 20B, and 20C are bonded to the other side (inner surface) via a second adhesive layer 14.

[0029] As shown in Figures 4 and 5, the battery case 50 using the battery packaging materials 1, 2, and 3 is manufactured 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 inside the battery case 50. In the manufactured battery case 50, the base material layer 13 becomes the outer layer, and the sealant layers 20A, 20B, and 20C become the inner layers. In the present invention, when describing the position of each layer constituting the battery packaging materials 1, 2, and 3 in terms of direction, the direction of the base material layer 13 is referred to as the outside, and the direction of the sealant layers 20A, 20B, and 20C is referred to as the inside.

[0030] (Composition of the sealant layer) The battery packaging material of the present invention is characterized by the material of the inner sealant layer. The sealant layer provides excellent chemical resistance to highly corrosive electrolytes and other substances, and also plays a role in providing heat-sealability to the battery packaging materials 1, 2, and 3.

[0031] The sealant layer consists of two or more layers and has a multilayer structure. The material of the first sealant layer, which is the innermost layer of the battery packaging material, and the second sealant layer laminated on its outer surface, that is, the material of the two layers that face each other when heat-sealing battery packaging materials placed opposite each other, are specified, and if necessary, the material of the layers other than the first and second sealant layers is also specified.

[0032] The sealant layer 20A of the battery packaging material 1 in Figure 1 has a four-layer structure in which the first sealant layer 21, the second sealant layer 22, the third sealant layer 23, and the fourth sealant layer 24 are stacked in 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, furthest from the barrier layer 11. The second sealant layer 22 is a layer stacked so as to be in contact with the outer surface of the first sealant layer 21. The fourth sealant layer 24 is the layer closest to the barrier layer 11 and in contact with the second adhesive layer 14. The third sealant layer 23 is an intermediate layer between the second sealant layer 22 and the fourth sealant layer 24.

[0033] The sealant layer 20B of the battery packaging material 2 in Figure 2 has a three-layer structure consisting of a first sealant layer 21 which is the innermost layer, a second sealant layer 22 which is laminated so as to be in contact with its outer surface, and a fourth sealant layer 24 which is closest to the barrier layer 11. The sealant layer 20C of the battery packaging material 3 in Figure 3 has a two-layer structure consisting of a first sealant layer 21 which is the innermost layer, and a second sealant layer 22 which is laminated so as to be in contact with its outer surface.

[0034] In the present invention, regardless of the number of sealant layers 20A, 20B, and 20C, the innermost layer is referred to as the first sealant layer 21, and the layer laminated on the barrier layer 11 side of the first sealant layer 21 is referred to as the second sealant layer 22. The first sealant layer 21 and the second sealant layer 22 are essential layers in the present invention. In sealant layers 20A and 20B with three or more layers, the layer closest to the barrier layer 11 is referred to as the fourth sealant layer 24. In sealant layers 20A with five or more layers, all layers between the second sealant layer 22 and the fourth sealant layer 24 are referred to as the third sealant layer 23. Therefore, in sealant layers with five or more layers (not shown), the third sealant layer 23 consists of two or more layers.

[0035] (First sealant layer) In the present invention, the first sealant layer 21 must be composed of a resin containing a propylene random copolymer having an MFR (230°C / 2.16 kg load) of 3 g / 10 min to 10 g / 10 min obtained according to JIS K7210-2 (2014), and more preferably composed of a resin with an MFR (230°C / 2.16 kg load) of 4 g / min to 7 g / 10 min.

[0036] This first sealant layer 21, together with the second sealant layer 22 described later, forms a heat-sealed portion (heat-fused portion) during heat sealing, which, as described later, allows gas inside the battery case to be efficiently released to the outside when the temperature rises too high, effectively preventing problems such as the rupture of the packaging material due to an increase in the internal pressure of the battery case.

[0037] The first sealant layer 21 is a resin containing a propylene random copolymer with an MFR of 33 g / 10 min to 103 g / 10 min, and therefore, as a battery packaging material, it can prevent stickiness and blocking. In other words, although the second sealant layer 22, described later, is prone to softening and can easily cause stickiness and blocking of the sheet (battery packaging material) in high-temperature environments (for example, transportation in midsummer or in an external warehouse), in the present invention, the first sealant layer 21 containing a resin with a specific MFR is laminated on the inner surface of the second sealant layer 22. Therefore, during heat sealing, sufficient fluidity of the resins in the first and second sealant layers can be ensured, while in high-temperature environments, the flow of the resin in the second sealant layer can be appropriately suppressed, thereby preventing the above-mentioned stickiness and blocking.

[0038] The thickness of the first sealant layer 21 is preferably adjusted to 2 μm to 5 μm. Specifically, by setting the thickness to 2 μm or more, it is possible to reliably suppress the occurrence of stickiness and blocking by the second sealant layer 22 in high-temperature environments. On the other hand, by setting the thickness to 5 μm or less, it is possible to heat seal together with the second sealant layer 22 without any problems during heat sealing, and gas inside the battery case can be released to the outside more efficiently when the temperature rises too high.

[0039] (Second sealant layer) In the present invention, the second sealant layer 21 must be composed of a resin containing a polybutene copolymer A which includes at least one of the following: a butene-ethylene copolymer, a butene-propylene copolymer, or a copolymer of an α-olefin having 5 or more carbon atoms and butene-1. Examples of polybutene copolymer A include a resin containing at least one of the following: a butene-ethylene copolymer, a butene-propylene copolymer, or a copolymer of an α-olefin having 5 or more carbon atoms and butene-1. In the present invention, since the second sealant layer 22 contains polybutene copolymer A containing butene-1 component, the side chains become bulkier compared to polypropylene and polyethylene, resulting in a steric hindrance that reduces the degree of crystallinity of the resin and lowers the melting point. Therefore, when a battery case manufactured by heat-sealing the second sealant layers together via the first sealant layer is overheated, gas generated in the battery body inside the case accumulates and the internal pressure rises. As a result, the low-melting-point component softens due to the temperature rise, the seal strength decreases, and the seal gradually opens. This allows the gas inside the battery case to be efficiently released to the outside, preventing problems such as the rupture of the packaging material due to the rise in internal pressure of the battery case.

[0040] Furthermore, in the present invention, it is preferable to include 30% to 50% by mass of the polybutene copolymer A in the second sealant layer. That is, since the content of polybutene copolymer A is 30% by mass or more, when the internal pressure rises during overheating of the battery case made by heat-sealing the second sealant layers together via the first sealant layer, gas can be efficiently discharged. On the other hand, since the content of polybutene copolymer A is 50% by mass or less, sufficient seal strength can be maintained up to around 100°C, and inadvertent peeling of the seal portion at low temperatures can be prevented. In addition, in the present invention, it is preferable to use polybutene copolymer A with a melting point in the range of 80°C to 120°C, and more preferably with a melting point in the range of 105°C to 115°C. That is, when this configuration is adopted, inadvertent peeling of the seal portion at low temperatures can be prevented more reliably, while gas can be discharged more reliably during overheating. 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 second sealant layer, gas inside the battery case can be released more appropriately when the temperature rises too high, and malfunctions caused by an increase in the internal pressure of the battery case can be prevented more reliably.

[0041] The above-mentioned propylene random copolymer B can be exemplified by a resin containing at least one of the following: propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-ethylene-butene random copolymer, propylene prepared using a metallocene catalyst, and propylene compounds prepared using a metallocene catalyst.

[0042] The mixing ratio of the above polybutene copolymer A to the above propylene random copolymer B is preferably set to 30:70 to 50:50, and a more preferable mixing ratio is 35:65 to 50:50. In other words, when this configuration is adopted, the gas release during overheating can be performed more effectively.

[0043] Furthermore, it is preferable to use a propylene random copolymer B with a melting point in the range of 80°C to 120°C, and more preferably one with a melting point in the range of 90°C to 110°C. In other words, by adopting this configuration, the above effects can be obtained even more reliably.

[0044] The first sealant layer 21 containing polybutene copolymer A may also contain other resins besides the propylene random copolymer B mentioned above.

[0045] (Third sealant layer) In the present invention, the third sealant layer 23 can be a polypropylene resin containing a propylene block copolymer and a propylene random copolymer. Specifically, the third sealant layer 23 can be at least one resin selected from propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-ethylene-butene random copolymer, propylene produced using a metallocene catalyst (metallocene-based propylene), propylene compounds produced using a metallocene catalyst (metallocene-based propylene compounds), propylene-ethylene block copolymer, propylene-butene block copolymer, and propylene-ethylene-butene block copolymer.

[0046] A particularly preferred melting point for the resin constituting the third sealant layer 23 is 130°C or higher.

[0047] In the present invention, since the third sealant layer contains a heat-resistant block copolymer, when manufacturing the battery case, the third sealant layer remains with sufficient space (layer thickness) during heat sealing. This ensures that insulation is reliably maintained by the residual third sealant layer, and that only the first and second sealant layers are reliably fused together. This allows for reliable gas release functionality in a desired temperature range at relatively low temperatures when internal pressure rises due to overheating, thereby more reliably preventing malfunctions caused by increased internal pressure in the battery case.

[0048] (Fourth sealant layer) In the present invention, a propylene random copolymer with a higher melting point than the second sealant layer 22 can be used as the fourth sealant layer 24. Specifically, the fourth sealant layer 24 can be at least one resin selected from propylene-ethylene random copolymer, propylene-butene random copolymer, propylene-ethylene-butene random copolymer, propylene produced using a metallocene catalyst, propylene compound produced using a metallocene catalyst, propylene-ethylene block copolymer, propylene-butene block copolymer, propylene-ethylene-butene block copolymer, and propylene homopolymer.

[0049] The resin constituting the fourth sealant layer 24 has a particularly preferred melting point of 130°C or higher, more preferably 140°C or higher. Furthermore, it is even more preferable that the fourth sealant layer 24 has a higher melting point than the third sealant layer 23.

[0050] In the present invention, since the fourth sealant layer has a higher melting point than the second sealant layer, the first and second sealant layers can be reliably heat-fused before the fourth sealant layer melts during sealing. As a result, insulation can be more reliably maintained by the residual fourth sealant layer, and only the first and second sealant layers can be more reliably fused, thereby appropriately preventing problems caused by increased internal pressure in the battery case. Furthermore, since the fourth sealant layer contains a propylene random copolymer, there is less elastomer component, making void formation less likely, and the structure has less steric hindrance, resulting in better adhesion to the adhesive layer. This prevents electrolyte erosion even if liquid entrapment occurs during heat sealing, prevents delamination at the interface between adhesive layers, for example, between the adhesive layer and the metal foil, or between the adhesive layer and the sealant layer, and improves the likelihood of delamination occurring between the first sealant layers when the temperature rises too high. In this respect as well, problems caused by increased internal pressure in the battery case can be prevented.

[0051] (Additives to the sealant layer, etc.) Each of the sealant layers 20A, 20B, and 20C may contain additives such as lubricants and antiblocking agents in addition to the resin described above. Lubricants and antiblocking agents have the effect of improving moldability by enhancing slipperiness.

[0052] Lubricants are not particularly limited, but examples include saturated fatty acid amides, unsaturated fatty acid amides, substituted amides, methylolamides, saturated fatty acid bisamides, unsaturated fatty acid bisamides, fatty acid ester amides, aromatic bisamides, etc.

[0053] Examples of saturated fatty acid amides include lauric acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, and hydroxystearic acid amide.

[0054] Examples of unsaturated fatty acid amides include oleic acid amide and erucic acid amide.

[0055] Examples of substituted amides include N-oleyl palmitate amide, N-stearyl stearate amide, N-stearyl oleate amide, N-oleyl stearate amide, and N-stearyl erucate amide.

[0056] Methylol stearate can be cited as an example of a methylolamide.

[0057] Examples of saturated fatty acid bisamides include methylenebisstearamide, ethylenebiscaprate, ethylenebislaurate, ethylenebisstearamide, ethylenebishydroxystearamide, ethylenebisbehenamide, hexamethylenebisstearamide, hexamethylenebisbehenamide, hexamethylenehydroxystearamide, N,N'-distearyladipamide, and N,N'-distearylsebacinamide.

[0058] Examples of unsaturated fatty acid bisamides include ethylenebisoleamide, ethylenebiserucamide, hexamethylenebisoleamide, N,N'-dioleyladipamide, and N,N'-dioleylsebacinamide.

[0059] Stearamidoethyl stearate can be cited as an example of a fatty acid ester amide.

[0060] Examples of aromatic bisamides include m-xylylenebisstearate, m-xylylenebishydroxystearate, and N,N'-distearyl isophthalamide.

[0061] Antiblocking agents are not limited to any specific type, but examples include particles of silica, acrylic resin, aluminum silicate, calcium carbonate, barium carbonate, titanium dioxide, talc, kaolin, etc.

[0062] 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.

[0063] The thickness of the sealant layers 20A, 20B, and 20C is preferably 20 μm to 100 μm in total thickness (T), and more preferably 20 μm to 80 μm. A total thickness of 25 μm to 50 μm is even more preferable. In a three-layer sealant layer 20B consisting of a first sealant layer 21, a second sealant layer 22, and a fourth sealant layer 24, the ratio t2:t4 of the thickness of the second sealant layer 22 (t2) and the thickness of the fourth sealant layer 24 (t4), when the total thickness (T) is 10, is preferably 2 to 8:8 to 2, and more preferably 4 to 8:6 to 2. Furthermore, in a four-layer sealant layer 20A consisting of a first sealant layer 21, a second sealant layer 22, a third sealant layer 23, and a fourth sealant layer 24, it is preferable to distribute the ratio t2:t3:t4 of the thickness of the second sealant layer 22 (t2), the thickness of the third sealant layer 23 (t3), and the thickness of the fourth sealant layer 24 (t4), when the total thickness (T) is 10, as 1~4:2~7:1~7, and even more preferable if it is 2~4:2~4:3~6.

[0064] (Layers other than the sealant layer of battery packaging material) In the battery packaging material of the present invention, the layers other than the sealant layer can be made of any known material as appropriate, and the bonding method is not particularly limited. Preferred materials for the layers other than the sealant layer are described below.

[0065] (base material layer) The base layer 13 uses a heat-resistant resin film that does not melt at the heat-sealing temperature when heat-sealing the battery packaging materials 1, 2, and 3. The heat-resistant resin used has a melting point that is 10°C or more, preferably 20°C or more, 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 film and polyester films, and stretched films of these are preferably used. In particular, the base layer 13 is preferably a biaxially oriented polyamide film such as biaxially oriented nylon film, a biaxially oriented polybutylene terephthalate (PBT) film, a biaxially oriented polyethylene terephthalate (PET) film, or a biaxially oriented polyethylene naphthalate (PEN) film. The nylon film is not particularly limited, but examples include 6 nylon film, 6,6 nylon film, and MXD nylon film. The base material layer 13 may be formed as a single layer, or it may be formed as a multilayer, for example, a polyester film / polyamide film (or a multilayer, such as a PET film / nylon film).

[0066] The thickness of the base material layer 13 is preferably 9 μm to 50 μm, which ensures sufficient strength as a packaging material and reduces stress during molding such as stretch molding and deep drawing, thereby improving moldability. A more preferable thickness for the base material layer 13 is 12 μm to 30 μm.

[0067] (Barrier layer) The barrier layer 11 plays a role in providing gas barrier properties to the battery packaging materials 1, 2, and 3, preventing the intrusion of oxygen and moisture. The barrier layer 11 is not particularly limited, but examples 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 prevents the occurrence of pinholes during rolling when manufacturing metal foil, while a thickness of 100 μm or less reduces stress during molding such as stretch molding and deep drawing, thereby improving moldability. A particularly preferred thickness of the barrier layer 11 is 30 μm to 80 μm.

[0068] Furthermore, it is preferable that the barrier layer 11 has undergone a surface treatment such as chemical conversion treatment on at least the surface of the metal foil facing the sealant layers 20A, 20B, and 20C. Such chemical conversion treatment can sufficiently prevent corrosion of the metal foil surface by the contents (such as the electrolyte of the battery).

[0069] For example, a chemical conversion treatment can be applied to metal foil by the following process.

[0070] After degreasing the metal foil, a chemical conversion treatment is performed by coating the surface with one of the aqueous solutions from 1) to 3) below and then drying it. 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 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 aforementioned chemical conversion coating has a chromium content of 0.1 mg / m² per side. 2 ~50mg / m 2 Preferably, 2 mg / m² 2 ~20mg / m 2 It is preferable.

[0071] (First adhesive layer) The first adhesive layer 12 is not particularly limited, but examples include an adhesive layer formed by a two-component curing adhesive. Examples of the two-component curing adhesive include a two-component curing adhesive composed of a first liquid (main component) consisting 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) consisting of isocyanate. In particular, it is preferable to use a two-component curing adhesive composed of a first liquid consisting of one or more polyols selected from the group consisting of polyester polyols and polyester urethane polyols, and a second liquid (curing agent) consisting of isocyanate. The preferred thickness of the first adhesive layer 12 is 1 μm to 5 μm, and a more preferred thickness is 2 μm to 5 microns.

[0072] (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 the following can be recommended: polyurethane resin, acrylic resin, epoxy resin, polyolefin resin, elastomer resin, fluororesin, or acid-modified polypropylene resin. Among these, an adhesive made of a polyurethane composite resin with acid-modified polyolefin as the main component is preferred. In the case of the sand lamination method or the heat lamination method, for example, a modified polyolefin resin such as acid-modified polypropylene resin or acid-modified polyethylene resin can be recommended. The preferred thickness of the second adhesive layer 14 varies depending on the lamination method, with 2 μm to 5 μm being preferred for the dry lamination method and 2 μm to 20 μm being preferred for the sand lamination method or the heat lamination method.

[0073] (Other lamination forms of 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; the base layer may be directly bonded to the barrier layer, or the sealant layer may be directly bonded to the barrier layer.

[0074] Furthermore, the battery packaging material of the present invention may also be configured by forming another layer on the outside of the base material layer, so that the outer layer consists of multiple layers including the base material layer. Examples of layers formed on the outside of the base material layer include a protective layer and a matte coat layer. These layers serve as the outermost layer of the battery packaging material, protecting the base material layer and providing good slipperiness to the surface, thereby improving moldability.

[0075] Recommended materials for the protective layer include phenoxy resins, urethane resins, epoxy resins, acrylic resins, polyolefin resins, fluororesins, and the like. The matte coat layer consists of a resin composition in which a matting agent is blended with the resin. Recommended materials for the matting agent include the above-mentioned resin and inorganic fine particles such as silica, alumina, calcium oxide, calcium carbonate, calcium sulfate, and calcium silicate, as well as resin beads such as acrylic beads.

[0076] (Battery construction) As shown in Figures 4 and 5, the perimeter of the battery packaging materials 1, 2, and 3, which are molded as needed, is heat-sealed with the bare cells (battery bodies) 51 housed inside the packaging materials, thereby creating a battery (energy storage device) in which the bare cells 51 are sealed inside the battery case 50.

[0077] In the present invention, it is preferable that the battery case 50 has a heat-sealed portion with a seal strength of 20 N / 15 mm width or more at a 100°C environment. In this case, the desired seal state can be reliably maintained in the heat-sealed portion until a predetermined overheating temperature range is reached, preventing inadvertent peeling of the seal at low temperatures, and resulting in a high-quality, high-performance battery product. [Examples]

[0078] The following describes examples that include the gist of the present invention, and comparative examples that demonstrate its effects.

[0079] [Table 1]

[0080] [Table 2]

[0081] [Table 3]

[0082] [Table 4]

[0083] Battery packaging materials for Examples 1-22 and Comparative Examples 1-7 were prepared. As shown in Battery Packaging Materials 1, 2, and 3 in Figures 1-3, these battery packaging materials have a base layer 13 bonded to one side of a barrier layer 11 via a first adhesive layer 12, and sealant layers 20A, 20B, and 20C bonded to the other side via a second adhesive layer 14. The barrier layer 11, base layer 13, first adhesive layer 12, and second adhesive layer 14 are common to all of the battery packaging materials, but the layer structure and materials of the sealant layers 20A, 20B, and 20C differ.

[0084] The sealant layer 20C of the battery packaging material in Examples 1 and 2 has a two-layer structure consisting of a first sealant layer 21 and a second sealant layer 22 (see Figure 3). The sealant layer 20B of Examples 3 and 4 has a three-layer structure consisting of a first sealant layer 21, a second sealant layer, and a fourth sealant layer 24 (see Figure 2). 5 The sealant layer 20A of ~22 and Comparative Examples 1~7 has a four-layer structure consisting of a first sealant layer 21, a second sealant layer 22, a third sealant layer 23, and a fourth sealant layer (see Figure 1).

[0085] For each example of battery packaging, a multi-layer sealant film was prepared using the materials and methods described later. The sealant film was then laminated to a laminated film (substrate layer, first adhesive layer, and barrier layer) made from materials common to all examples, via a second adhesive. Details of the sealant film for each example and the method of preparing the battery packaging are as follows.

[0086] <Example 1> A resin composition for the first sealant layer was prepared using polypropylene-ethylene random copolymer (rPP) with an MFR of 7 g / 10 min, a melting point of 132°C, and a thickness of 3 μm, as shown in Table 1. Furthermore, a resin composition for the second sealant layer was prepared by miscible the resin A (polybutene copolymer A), which is 1-butene-propylene copolymer (melting point 110°C), and the resin B (propylene random copolymer B), which is propylene-1-butene copolymer (melting point 130°C), as shown in Table 1, at the content (mass%) shown in Table 1. To this mixed resin, 1000 ppm of erucic acid amide was added as a lubricant and 2000 ppm of silica particles as an antiblocking agent.

[0087] A 33 μm thick sealant layer film was fabricated by co-extruding the resin compositions for the first and second sealant layers using a T-die so that they were laminated together, resulting in a two-layer structure with a 3 μm thick first sealant layer and a 30 μm thick second sealant layer laminated in that order.

[0088] <Example 2> A resin composition for the first sealant layer was prepared in the same manner as above using the resin for the first sealant layer shown in Table 1, and a resin composition for the second sealant layer was prepared in the same manner as above using resins A and B for the second sealant layer shown in Table 1. A two-layer sealant film was made using the resin compositions for the first and second sealant layers in the same manner as above.

[0089] <Example 3> A resin composition for the first sealant layer was prepared in the same manner as above using rPP, the resin for the first sealant layer shown in Table 1. A resin composition for the second sealant layer was prepared in the same manner as above using resins A and B for the second sealant layer shown in Table 1. A resin composition for the fourth sealant layer was prepared by blending 1000 ppm of erucamide (lubricant) and 2000 ppm of silica particles (antiblocking agent) with propylene-ethylene random copolymer (melting point 142°C), the resin for the fourth sealant layer shown in Table 3. The resin compositions for the first, second, and fourth sealant layers were co-extruded using a T-die so that they were laminated together to produce a 3-layer sealant film with a thickness of 3 μm, consisting of a 3 μm thick first sealant layer, a 15 μm thick second sealant layer, and a 15 μm thick fourth sealant layer, laminated in this order.

[0090] <Example 4> A resin composition for the first sealant layer was prepared in the same manner as above using the resin for the first sealant layer shown in Table 1, and a resin composition for the second sealant layer was prepared in the same manner as above using resins A and B for the second sealant layer shown in Table 1. Furthermore, a resin composition for the fourth sealant layer was prepared in the same manner as above using the resin for the fourth sealant layer shown in Table 3. A three-layer sealant film was prepared in the same manner as above using the resin compositions for the first, second, and fourth sealant layers.

[0091] <Example 5> A resin composition for the first sealant layer was prepared in the same manner as above using the resin for the first sealant layer shown in Table 1, and a resin composition for the second sealant layer was prepared in the same manner as above using resins A and B for the second sealant layer shown in Table 1. Furthermore, a resin composition for the third sealant layer was prepared by blending 1000 ppm of erucamide (lubricant) and 2000 ppm of silica particles (antiblocking agent) into a mixed resin (melting point 135°C) of rPP (propylene-ethylene random copolymer) and bPP (propylene-ethylene block copolymer), which are the resins for the third sealant layer shown in Table 3. Furthermore, a resin composition for the fourth sealant layer was prepared in the same manner as above using the resin for the fourth sealant layer shown in Table 3.

[0092] By co-extruding the resin compositions for the first to fourth sealant layers using a T-die so that they are laminated, a 33 μm thick sealant layer film with a four-layer structure was produced, consisting of a 3 μm thick first sealant layer, a 6 μm thick second sealant layer, an 18 μm thick third sealant layer, and a 6 μm thick fourth sealant layer, laminated in this order.

[0093] <Examples 6-10> A resin composition for the first sealant layer was prepared in the same manner as above using the resin for the first sealant layer shown in Table 1, and a resin composition for the second sealant layer was prepared in the same manner as above using resins A and B for the second sealant layer shown in Table 1. Resin compositions for the third and fourth sealant layers were prepared in the same manner as above using the resins for the third and fourth sealant layers shown in Table 3. A four-layer sealant film was made using these resin compositions for the first to fourth sealant layers in the same manner as above.

[0094] <Example 11> A resin composition for the first sealant layer was prepared in the same manner as above, using the resin for the first sealant layer shown in Table 1. A resin composition for the second sealant layer was prepared by blending 1000 ppm of erucamide (lubricant) and 2000 ppm of silica particles (antiblocking agent) with a mixed resin of resins A to C shown in Table 1. Furthermore, resin compositions for the third and fourth sealant layers were prepared in the same manner as above, using the resins for the third and fourth sealant layers shown in Table 3. A four-layer sealant film was prepared in the same manner as above using these resin compositions for the first to fourth sealant layers.

[0095] <Examples 12-22> Using the resins for the first sealant layer shown in Tables 1 and 2, a resin composition for the first sealant layer was prepared in the same manner as described above. Similarly, using resins A and B for the second sealant layer shown in Tables 1 and 2, a resin composition for the second sealant layer was prepared in the same manner as described above. Using the resins for the third and fourth sealant layers shown in Tables 3 and 4, resin compositions for the third and fourth sealant layers were prepared in the same manner as described above. Using these resin compositions for the first to fourth sealant layers, a four-layer sealant film was fabricated in the same manner as described above.

[0096] <Comparative Examples 1-6> A resin composition for the first sealant layer was prepared in the same manner as above using the resin for the first sealant layer shown in Table 2, and a resin composition for the second sealant layer was prepared in the same manner as above using resins A, B, or resin A for the second sealant layer shown in Table 2. Resin compositions for the third and fourth sealant layers were prepared in the same manner as above using the resins for the third and fourth sealant layers shown in Table 4. A four-layer sealant film was made using these resin compositions for the first to fourth sealant layers in the same manner as above.

[0097] <Comparative Example 7> Using resins A and B for the second sealant layer shown in Table 2, resin compositions for the second sealant layer were prepared in the same manner as described above. Using resins for the third and fourth sealant layers shown in Table 4, resin compositions for the third and fourth sealant layers were prepared in the same manner as described above. Using these resin compositions for the second to fourth sealant layers, a three-layer sealant film without the first sealant layer was prepared in the same manner as described above.

[0098] (Method for measuring melting point) The melting points of each resin used in the above examples and comparative examples are the peak temperature Tpm measured by differential operation calorimetry (DSC) at a heating rate of 10°C / min in accordance with JIS K7121.

[0099] (Manufacturing of battery packaging materials) As the barrier layer 11, a chemical conversion treatment solution consisting of polyacrylic acid (acrylic resin), chromium(III) salt compound, water, and alcohol was applied to both sides of an aluminum foil made of A8079 with a thickness of 40 μm, and then dried at 150°C to form a chemical conversion film. The amount of chromium deposited on this chemical conversion film was 5 mg / m² per side. 2 Furthermore, a biaxially oriented nylon 6 film with a thickness of 15 μm was used as the base layer 13.

[0100] A two-component curing urethane adhesive (first adhesive layer) was applied to one side (outer surface) of the barrier layer 11 to form a first adhesive layer 12 with a thickness of 3 μm, and the base material layer 13 was dry laminated.

[0101] 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 with a thickness of 2 μm, and the sealant layer films of the above examples and comparative examples were dry-laminated. At this time, the second sealant layer 22 was in contact with the second adhesive layer 14 for the two-layer sealant layer film, and the fourth sealant layer 24 was in contact with the second adhesive layer 14 for the three- or four-layer sealant layer film.

[0102] Then, the laminate sheet with all layers bonded together was sandwiched between a rubber nip roll and a laminate roll heated to 100°C and pressed to complete the dry lamination process. After that, the battery packaging materials for the example and comparative example were obtained by aging (heating) at 40°C for 10 days.

[0103] (Evaluation of battery packaging materials) The following items were measured and evaluated for each example of battery packaging material that was prepared. The results are shown in Tables 3 and 4.

[0104] (Seal strength) Multiple test specimens were prepared by cutting battery packaging material to a width of 15 mm and a length of 150 mm. Two of the test specimens were stacked so that the sealant layers 20A, 20B, and 20C faced each other, and heat-sealed by heating one side using a heat sealing device (Tester Industries Co., Ltd., TP-701-A) under the conditions of heat sealing temperature: 180°C, sealing pressure: 0.3 MPa (gauge indicated pressure), and sealing time: 4 seconds. These were used as test specimens for seal strength measurement. Three of these test specimens were prepared for each example.

[0105] Three test specimens for measuring seal strength were left standing for 24 hours at three different temperatures: 25°C, 100°C, and 130°C. After that, the seal strength was measured at each temperature.

[0106] The seal strength was measured in accordance with JIS Z0238-1998, using a Shimadzu Strograph (AGS-5kNX) tensile testing machine. One end of the test specimen was clamped and fixed with one chuck of the tensile testing machine, while the other end of the test specimen was grasped with the other chuck. The peel strength was measured when the specimen was peeled in a T-shape at a tensile speed of 100 mm / min, and this was defined as the seal strength (N / 15 mm width).

[0107] (Opening test) A rectangular test specimen was prepared by cutting battery packaging material to a width of 100 mm and a length of 200 mm. This rectangular test specimen was folded in half lengthwise, with the sealant layers 20A, 20B, and 20C facing inward. Two sides following the fold were heated on one side under the following conditions: seal width: 5 mm, heat seal temperature: 180°C, seal pressure: 0.3 MPa (gauge indicated pressure), and seal time: 4 seconds, creating a bag with an opening on the opposite side of the fold. Next, 2.0 g of water was added to the opening of the bag, and the opening was heat-sealed under the same conditions as the other two sides to seal the bag, which was then used as the test specimen for the opening test.

[0108] The test specimens for the opening test were placed in an oven and heated from 25°C to 130°C at a heating rate of 5°C / min. After reaching 130°C, they were held at 130°C for 30 minutes. The opening state from the start of heating until the end of the 30-minute period at 130°C was observed and evaluated according to the following criteria. Criteria A to D below indicate a pass, while X and Y indicate a fail. A: The container was opened while the temperature was rising from 100°C to 130°C, allowing the gas to escape slowly. B: The container was not opened during the heating process up to 130°C, but was opened while the temperature was maintained at 130°C, allowing the gas to escape slowly. C: The container was opened while the temperature was being raised from 100°C to 130°C, and the gas escaped rapidly. D: The container was not opened during the heating process to 130°C, and the gas rapidly escaped while the temperature was maintained at 130°C. X: The package was not opened even while being stored at 130°C. Y: Opened during the heating process up to 100℃.

[0109] This test was based on the external heating test (JIS C8714), but while JIS C8714 specifies a holding time of 130°C for 10 minutes after reaching 130°C, this test set the holding time at 130°C to 30 minutes, thus performing heating under more stringent conditions.

[0110] (Blocking test) Ten square test pieces measuring 100 mm wide x 100 mm long were cut from the battery packaging material for each example and comparative example, and these ten pieces were stacked together for each example and comparative example. At this time, the test pieces were arranged so that the sealant layer and the base material layer were in contact with each other vertically.

[0111] The stacked test specimens (laminated test specimens) were sandwiched between two 150mm x 150mm, 2mm thick SUS plates (approximately 350g each) and placed in a constant temperature chamber, with a 2kg weight placed on top of the SUS plates. After leaving them in the constant temperature chamber at 60°C for one day, the laminated test specimens were removed and, at room temperature (25°C), tesa tape (77610) was applied to the top test specimen (packaging material). This tape was then used to separate the top test specimen (sheet) from the subsequent sheets. The blocking was then evaluated according to the following criteria. In the evaluation criteria, "○" and "△" indicate a pass, and "×" indicates a fail. ○: The top test specimen (sheet) peeled off without resistance. △: A sound was heard when peeling off the top sheet. ×: When peeling off the top sheet, the subsequent sheets also lifted up, or the tape peeled off the sheet, making it impossible to peel off the top sheet.

[0112] (Evaluation results) From the evaluation results in Tables 3 and 4, it was confirmed that the battery packaging material of the example maintained high seal strength below 100°C, and gradually decreased seal strength between 100°C and 130°C, resulting in a gradual opening.

[0113] Furthermore, it was confirmed that the battery packaging material in the embodiment could be smoothly removed one sheet at a time even when stacked, and that stickiness and blocking could be suppressed. [Industrial applicability]

[0114] The battery packaging material of the present invention can be suitably used as a case material for rechargeable batteries for vehicles, stationary devices, laptop computers, mobile phones, and cameras, and especially for small portable lithium-ion rechargeable batteries. [Explanation of symbols]

[0115] 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 24…Fourth sealant layer 50...Battery case

Claims

1. A battery packaging material comprising a base layer as an outer layer, a sealant layer as an inner layer, and a barrier layer disposed between these two layers, The sealant layer consists of two or more layers, and includes a first sealant layer disposed on the innermost part of the sealant layer and a second sealant layer laminated on the outer surface of the first sealant layer. The resin constituting the first sealant layer is a resin containing a propylene random copolymer having an MFR (230°C / 2.16 kg load) of 3 g / 10 min to 10 g / 10 min obtained according to JIS K7210-2 (2014). The battery packaging material is characterized in that the resin constituting the second sealant layer contains a polybutene copolymer A which includes 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 battery packaging material according to claim 1, wherein the resin constituting the second sealant layer contains 30% to 50% by mass of the polybutene copolymer A and 50% to 70% by mass of the propylene random copolymer.

3. The battery packaging material according to claim 1 or 2, wherein the melting point of the polybutene copolymer A is 120°C or lower.

4. The battery packaging material according to claim 1 or 2, wherein the thickness of the first sealant layer is 2 μm to 5 μm.

5. The sealant layer has a multilayer structure including a fourth sealant layer closest to the barrier layer and a third sealant layer provided between the second and fourth sealant layers. The battery packaging material according to claim 1 or 2, wherein the third sealant layer is a polypropylene resin comprising a propylene block copolymer and a propylene random copolymer.

6. The sealant layer includes a fourth sealant layer closest to the barrier layer. The battery packaging material according to claim 1 or 2, wherein the fourth sealant layer comprises a propylene random copolymer having a higher melting point than the second sealant layer.

7. The battery packaging material according to claim 1 or 2, wherein, when the sealant layers are heat-sealed together, the seal strength at the heat-sealed portion in a 100°C environment is 20 N / 15 mm width or more.

8. A battery case formed by heat-sealing the sealant layers of the battery packaging material described in claim 1 or 2, A battery case characterized by having a seal strength of 20 N / 15 mm width or more at a 100°C environment in the heat-sealed portion.

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