Resin film for terminals and power storage device using same

Abstract

This terminal resin film is disposed so as to cover a part of the outer circumferential surface of a metal terminal electrically connected to a power storage device body constituting a power storage device. The terminal resin film has a layer containing an ultrahigh molecular weight polyolefin having a weight-average molecular weight of 2.0×105-1.0×106.

Description

[Technical Field]

[0001] The present disclosure relates to a resin film for a terminal and an electricity storage device using the same. [Background technology]

[0002] In recent years, there has been an increasing demand for miniaturization of mobile devices and effective utilization of natural energy sources, and research and development is being conducted on lithium-ion secondary batteries (a type of energy storage device) that can produce higher voltages and have higher energy densities.

[0003] Conventionally, metal cans have been widely used as packaging materials for the lithium ion secondary batteries. However, in response to demands for thinner and more diverse products to which the batteries are applied, packaging materials in the form of a bag made of a laminate of a metal layer (e.g., aluminum foil) and a resin film have come to be widely used because of their low manufacturing costs.

[0004] Laminated lithium-ion secondary batteries, in which a battery body is housed and sealed inside the packaging material, are provided with current extraction terminals called tabs. The tabs are connected to the negative or positive electrode of the battery body and include a metal terminal (sometimes called a "tab lead") that extends outside the packaging material (exterior material), and a terminal resin film (sometimes called a "tab sealant") that covers part of the outer periphery of each metal terminal (see, for example, Patent Documents 1 to 3). Typically, the terminal resin film is fused to the metal terminal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-4316 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-218766 [Patent Document 3] Japanese Patent Application Laid-Open No. 2009-259739 Summary of the Invention [Problem to be solved by the invention]

[0006] Recently, as the capacity of batteries has increased, metal terminals have become thicker, which tends to increase the time required to fuse the terminal resin film to the metal terminal. Longer fuse times between the terminal resin film and the metal terminal are undesirable because they reduce the battery manufacturing efficiency. On the other hand, shortening the fuse time to improve battery manufacturing efficiency can result in a problem of reduced adhesion between the terminal resin film and the metal terminal. Furthermore, depending on the material used, gel may form in the terminal resin film, resulting in poor appearance such as fisheyes.

[0007] The present disclosure aims to provide a resin film for terminals that has an excellent appearance and has excellent adhesion to metal terminals even when the time required to fuse the resin film for terminals to the metal terminals is short (for example, within 5 seconds), and an energy storage device using the same. [Means for solving the problem]

[0008] In order to achieve the above object, the present disclosure provides a resin film for a terminal that is disposed so as to cover a part of the outer peripheral surface of a metal terminal that is electrically connected to a main body of an electricity storage device, the resin film having a weight-average molecular weight of 2.0 × 10 5 ~1.0×10 6 The present invention provides a resin film for a terminal, which has a layer containing an ultra-high molecular weight polyolefin of the formula (I).

[0009] As a result of intensive research by the inventors, it was found that the resin film for terminals has a weight average molecular weight of 2.0 × 10 5 ~1.0×10 6 It has been found that by having a layer containing an ultra-high molecular weight polyolefin, the appearance of the resin film for terminals is excellent, and the adhesion to the metal terminal is excellent even when the time required to fuse the resin film for terminals to the metal terminal is short (for example, within 5 seconds).

[0010] In the resin film for terminals, the content of the ultra-high molecular weight polyolefin may be 5 to 50% by mass based on the total amount of the resin film for terminals. By having the content of the ultra-high molecular weight polyolefin be 5 to 50% by mass based on the total amount of the resin film for terminals, the appearance of the resin film for terminals becomes more excellent, and the adhesion between the resin film for terminals and the metal terminals becomes more excellent.

[0011] In the resin film for terminal, the ultra-high molecular weight polyolefin may contain polypropylene, which improves the appearance of the resin film for terminal and improves the adhesion between the resin film for terminal and the metal terminal.

[0012] The resin film for a terminal may have a plurality of layers, at least one of which contains the ultra-high molecular weight polyolefin. The resin film for a terminal may have an innermost layer disposed on the surface facing the metal terminal, an outermost layer disposed on the surface opposite the innermost layer, and an intermediate layer disposed between the innermost layer and the outermost layer. The intermediate layer and / or the outermost layer may contain the ultra-high molecular weight polyolefin. Of the innermost layer, the outermost layer, and the intermediate layer, only the intermediate layer may contain the ultra-high molecular weight polyolefin. When the intermediate layer and / or the outermost layer contains the ultra-high molecular weight polyolefin, the appearance of the resin film for a terminal is improved and the adhesion between the resin film for a terminal and the metal terminal is improved. When only the intermediate layer contains the ultra-high molecular weight polyolefin, the appearance of the resin film for a terminal is further improved and the adhesion between the resin film for a terminal and the metal terminal is further improved.

[0013] In the resin film for a terminal, the innermost layer may contain a resin having a polar group. When the innermost layer contains a resin having a polar group, the adhesion between the resin film for a terminal and the metal terminal is more excellent.

[0014] In the resin film for terminal, the innermost layer has a melt flow rate MFR1 at 230°C, the outermost layer has a melt flow rate MFR2 at 230°C, and the intermediate layer has a melt flow rate MFR3 at 230°C. The MFR3 may be 0.1 to 2.5 g / 10 min, and the difference between MFR1 and MFR3 (MFR1-MFR3) and the difference between MFR2 and MFR3 (MFR2-MFR3) are both 5 to 30 g / 10 min. When the MFR3 is 0.1 to 2.5 g / 10 min and the difference between MFR1-MFR3 and MFR2-MFR3 are both 5 to 30 g / 10 min, the insulating properties of the intermediate layer, the processability of the resin film for terminal, and the adhesion between the resin film for terminal and a metal terminal are improved.

[0015] In the resin film for a terminal, the innermost layer has a melting point Tm1, the outermost layer has a melting point Tm2, ​​and the intermediate layer has a melting point Tm3, the melting point Tm3 may be 150 to 200° C., and the difference between Tm3 and Tm1 (Tm3-Tm1) and the difference between Tm3 and Tm2 (Tm3-Tm2) may be 10 to 100° C. When Tm3 is 150 to 200° C. and Tm3-Tm1 and Tm3-Tm2 are 10 to 100° C., the insulating properties of the intermediate layer, the processability of the resin film for a terminal, and the adhesion between the resin film for a terminal and a metal terminal are more excellent.

[0016] The resin film for a terminal may be formed by an inflation molding method.

[0017] The present disclosure also provides an electricity storage device comprising: an electricity storage device main body, a metal terminal electrically connected to the electricity storage device main body, an exterior material sandwiching the metal terminal and housing the electricity storage device main body, and a resin film for terminals of the present disclosure covering a part of the outer circumferential surface of the metal terminal and disposed between the metal terminal and the exterior material. In such an electricity storage device, the resin film for terminals has an excellent appearance, and exhibits excellent adhesion to the metal terminals even when the time required for fusing the resin film for terminals to the metal terminals is short (for example, within 5 seconds). [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide a resin film for a terminal that has excellent appearance and excellent adhesion to a metal terminal even when the time for fusing the resin film for a terminal to the metal terminal is short (for example, within 5 seconds).Furthermore, according to the present disclosure, it is possible to provide an electricity storage device using the resin film for a terminal. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a perspective view showing a schematic configuration of an electricity storage device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing an example of a cut surface of the exterior packaging material shown in FIG. [Figure 3] 2 is a cross-sectional view of the resin film for terminal and the metal terminal shown in FIG. 1 taken along the line AA. [Figure 4] FIG. 2 is a schematic diagram illustrating a method for preparing a sample for measuring heat seal strength in the examples. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional ratios of the drawings are not limited to those shown in the drawings.

[0021] Fig. 1 is a perspective view showing a schematic configuration of an electricity storage device according to this embodiment. In Fig. 1, a lithium ion secondary battery is illustrated as an example of an electricity storage device 10, and the following description will be given. The lithium ion secondary battery configured as shown in Fig. 1 may be called a battery pack, a battery cell, or the like.

[0022] The electricity storage device 10 shown in FIG. 1 is a lithium ion secondary battery, and includes an electricity storage device body 11, an exterior material 13, a pair of metal terminals 14 (tab leads), and a terminal resin film 16 (tab sealant).

[0023] The electricity storage device main body 11 is a battery main body that charges and discharges. The exterior material 13 sandwiches the metal terminals 14 and houses the electricity storage device main body 11. The exterior material 13 covers the surface of the electricity storage device main body 11 and is arranged so as to be in contact with a part of the terminal resin film 16.

[0024] Fig. 2 is a cross-sectional view showing an example of a cut surface of the exterior packaging material shown in Fig. 1. In Fig. 2, the same components as those in the structure shown in Fig. 1 are denoted by the same reference numerals.

[0025] An example of the configuration of the exterior packaging material 13 will be described with reference to Fig. 2. The exterior packaging material 13 has a seven-layer structure in which, from the inside in contact with the electricity storage device body 11, an inner layer 21, an inner layer-side adhesive layer 22, a corrosion prevention treatment layer 23-1, a barrier layer 24, a corrosion prevention treatment layer 23-2, an outer layer-side adhesive layer 25, and an outer layer 26 are laminated in this order.

[0026] The inner layer 21 is a sealant layer that provides heat-sealing properties to the exterior material 13, and is a layer that is placed on the inside and heat-sealed (thermally fused) when assembling the electricity storage device 10. Examples of the base material for the inner layer (sealant layer) 21 include polyolefin resins and acid-modified polyolefin resins obtained by graft-modifying polyolefin resins with maleic anhydride or the like. Examples of the polyolefin resin that can be used include low-density, medium-density, and high-density polyethylenes; ethylene-α-olefin copolymers; homo-, block-, or random polypropylenes; and propylene-α-olefin copolymers. Among these, it is preferable that the polyolefin resin contains polypropylene. These polyolefin resins can be used alone or in combination of two or more.

[0027] The inner layer 21 may be a single-layer film or a multilayer film in which multiple layers are laminated, depending on the required function. Specifically, it may be a multilayer film in which a resin such as an ethylene-cyclic olefin copolymer or polymethylpentene is interposed to impart moisture resistance. The inner layer 21 may contain various additives (such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier).

[0028] The thickness of the inner layer 21 is preferably 10 to 150 μm, and more preferably 30 to 80 μm. When the thickness of the inner layer 21 is 10 μm or more, sufficient heat seal adhesion between the exterior materials 13 and sufficient adhesion to the terminal resin film 16 is achieved. Furthermore, when the thickness of the inner layer 21 is 150 μm or less, the cost of the exterior material 13 can be reduced.

[0029] The inner adhesive layer 22 can be appropriately selected from known adhesives such as dry lamination adhesives and acid-modified heat-fusible resins.

[0030] As shown in Figure 2, it is preferable from a performance standpoint that the corrosion prevention treatment layers 23-1 and 23-2 are formed on both sides of the barrier layer 24, but from the standpoint of reducing costs, the corrosion prevention treatment layer 23-1 may be placed only on the surface of the barrier layer 24 located on the inner layer side adhesive layer 22 side.

[0031] The barrier layer 24 may be a conductive metal layer. Examples of materials for the barrier layer 24 include aluminum and stainless steel, with aluminum being preferred from the standpoints of cost, mass (density), and the like.

[0032] The outer adhesive layer 25 may be a polyurethane adhesive containing polyester polyol, polyether polyol, acrylic polyol, or the like as a main component.

[0033] The outer layer 26 may be a single layer or a multilayer film made of nylon, polyethylene terephthalate (PET), or the like. Like the inner layer 21, the outer layer 26 may contain various additives (such as a flame retardant, a slip agent, an antiblocking agent, an antioxidant, a light stabilizer, and a tackifier). The outer layer 26 may have a protective layer formed by laminating a resin insoluble in the electrolyte solution or coating the outer layer with a resin component insoluble in the electrolyte solution to prevent leakage of the electrolyte solution.

[0034] Fig. 3 is a cross-sectional view of the resin film for terminal and the metal terminal in the direction of line AA shown in Fig. 1. In Fig. 3, the same components as those in the structure shown in Fig. 1 are denoted by the same reference numerals.

[0035] 1 and 3, a pair (two in the case of FIG. 1) of metal terminals 14 includes a metal terminal body 14-1 and a corrosion prevention layer 14-2. Of the pair of metal terminal bodies 14-1, one metal terminal body 14-1 is electrically connected to the positive electrode of the electricity storage device body 11, and the other metal terminal body 14-1 is electrically connected to the negative electrode of the electricity storage device body 11. The pair of metal terminal bodies 14-1 extend in a direction away from the electricity storage device body 11, and a portion thereof is exposed from the exterior material 13. The shape of the pair of metal terminal bodies 14-1 may be, for example, a flat plate shape.

[0036] The material of the metal terminal body 14-1 can be a metal, and the metal to be used for the metal terminal body 14-1 can be determined in consideration of the structure of the electricity storage device body 11, the materials of each component of the electricity storage device body 11, etc.

[0037] When the electricity storage device 10 is a lithium ion secondary battery, aluminum can be used as the positive electrode current collector, and copper can be used as the negative electrode current collector. When the electricity storage device 10 is a lithium ion secondary battery, the material of the metal terminal body 14-1 connected to the positive electrode of the electricity storage device body 11 is preferably aluminum. Furthermore, from the viewpoint of corrosion resistance to the electrolyte, the material of the metal terminal body 14-1 connected to the positive electrode of the electricity storage device body 11 is more preferably an aluminum material with a purity of 97% or more, such as 1N30. Furthermore, when the metal terminal body 14-1 is to be bent, it is preferable to use an O material that has been tempered by sufficient annealing in order to add flexibility. The material of the metal terminal body 14-1 connected to the negative electrode of the electricity storage device body 11 is preferably copper with a nickel plating layer formed on its surface, or nickel.

[0038] The thickness of the metal terminal body 14-1 can be determined depending on the size and capacity of the lithium ion secondary battery. In the case of a small lithium ion secondary battery, the thickness of the metal terminal body 14-1 may be 50 μm or more. In the case of a large lithium ion secondary battery for power storage, vehicle use, etc., the thickness of the metal terminal body 14-1 can be appropriately set within the range of 100 to 500 μm.

[0039] The corrosion prevention layer 14-2 is disposed so as to cover the surface of the metal terminal body 14-1. In the case of a lithium-ion secondary battery, the electrolyte contains a corrosive component such as LiPF6. The corrosion prevention layer 14-2 is a layer for preventing corrosion of the metal terminal body 14-1 due to the corrosive component such as LiPF6 contained in the electrolyte.

[0040] [Resin film for terminals] 3, the terminal resin film 16 according to this embodiment is disposed so as to cover part of the outer peripheral surface of the metal terminal 14. The terminal resin film 16 has a weight average molecular weight of 2.0×10 5 ~1.0×10 6 The resin film for terminal 16 has a layer containing an ultra-high molecular weight polyolefin (hereinafter referred to as "ultra-high molecular weight polyolefin A") having a weight average molecular weight of 2.0×105 ~1.0×10 6 By having a layer containing ultra-high molecular weight polyolefin, the appearance of the resin film for terminal is excellent, and even if the time required to fuse the resin film for terminal 16 and the metal terminal 14 is short (for example, within 5 seconds), the resin film for terminal 16 has excellent adhesion to the metal terminal 14. Furthermore, by having a layer containing ultra-high molecular weight polyolefin, the resin film for terminal 16 can maintain adhesion to the metal terminal 14 even in a high temperature environment (for example, 80°C).

[0041] In this specification, ultra-high molecular weight polyolefin refers to a polyolefin having a molecular weight of 2.0 × 10 5 This refers to a polyolefin having a weight-average molecular weight of 200,000 or more. The weight-average molecular weight can be measured using a high-temperature gel permeation chromatography (GPC) device. For example, the weight-average molecular weight can be measured by passing an ultra-high molecular weight polyolefin mixed with o-dichlorobenzene or trichlorobenzene through a column at a temperature of 135 to 170°C, and can be calculated using a calibration curve using standard polystyrene or standard polyethylene.

[0042] Examples of the ultra-high molecular weight polyolefin A include ultra-high molecular weight linear polyolefins such as polyethylene and polypropylene, and ultra-high molecular weight cyclic polyolefins such as polynorbornene. From the viewpoint of improving the appearance of the resin film for terminals, the ultra-high molecular weight polyolefin A is preferably an ultra-high molecular weight linear polyolefin. The ultra-high molecular weight linear polyolefin may be linear or branched. The ultra-high molecular weight polyolefin A may be a homopolymer, a random copolymer, or a block copolymer. These ultra-high molecular weight polyolefins A may be used alone or in combination of two or more.

[0043] It is preferable that the ultra-high molecular weight polyolefin A contains polypropylene (ultra-high molecular weight polypropylene) from the viewpoints of suppressing the generation of gel, improving the appearance of the resin film for terminals, and improving the adhesion between the resin film for terminals and metal terminals at room temperature (25°C) and high temperature (80°C), as well as the adhesion between the resin film for terminals and exterior materials.

[0044] Examples of ultra-high molecular weight polypropylene include propylene homopolymers (homopolypropylenes), ethylene-propylene block copolymers (block polypropylenes), ethylene-propylene random copolymers (random polypropylenes), and copolymers of propylene with α-olefins other than ethylene and propylene (propylene-based copolymers). Examples of α-olefins that serve as monomers constituting propylene-based copolymers include 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 3-methyl-1-pentene, and 4-methyl-1-pentene. It is preferable that the ultra-high molecular weight polypropylene contain ultra-high molecular weight homopolypropylene, as this facilitates low-heat sealing (low temperature, short time) with metal terminals and improves battery production efficiency.

[0045] The weight average molecular weight of ultra-high molecular weight polyolefin A is set to 3.0 × 10 in order to suppress gel generation and improve the appearance of the resin film for terminals. 5 More than 4.0×10 is preferable. 5 More preferably, 5.0 x 10 5 More preferably, 6.0 x 10 5 The weight average molecular weight of the ultra-high molecular weight polyolefin A is particularly preferably 9.0 × 10 or less from the viewpoint of obtaining better adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and at a high temperature (80°C). 5 The following is preferable: 8.0 x 10 5 Less than 7.0 x 10 is preferable. 5 From these viewpoints, the weight average molecular weight of the ultra-high molecular weight polyolefin A is more preferably 3.0×10 5 ~9.0×10 5 is preferred, and 4.0 × 10 5 ~8.0×105 is more preferable, and 5.0 × 10 5 ~7.0×10 5 is more preferred.

[0046] The molecular weight distribution (Mw / Mn), which is the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of the ultra-high molecular weight polyolefin A, is preferably 5 or more, more preferably 6 or more, and even more preferably 8 or more, from the viewpoints of suppressing gel formation due to excellent compatibility with resins other than the ultra-high molecular weight polyolefin A (for example, the base resin described below) and improving the appearance of the resin film for terminal. The molecular weight distribution of the ultra-high molecular weight polyolefin A is preferably 12 or less, more preferably 10 or less, from the viewpoint of improving the adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and high temperature (80°C). From these viewpoints, the molecular weight distribution of the ultra-high molecular weight polyolefin A is preferably 5 to 12, more preferably 6 to 12, and even more preferably 8 to 10. The molecular weight distribution of the ultra-high molecular weight polyolefin A can be measured using a GPC device, as with the weight-average molecular weight.

[0047] The melting point (Tm) of the ultra-high molecular weight polyolefin A is preferably 130 to 220°C, more preferably 150 to 200°C, from the viewpoint of providing excellent insulating properties for the resin film for terminal and better adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and high temperature (80°C).

[0048] In this specification, the melting point of a resin can be determined by measuring with a differential scanning calorimeter (DSC) and reading the temperature at the top of the main peak, which is the peak with the greatest heat of dissolution.

[0049] The content of ultra-high molecular weight polyolefin A is preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, based on the total amount of the resin film for terminal, from the viewpoint of suppressing gel generation and thereby improving the appearance of the resin film for terminal.The content of ultra-high molecular weight polyolefin A is preferably 50% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, based on the total amount of the resin film for terminal, from the viewpoint of improving the adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and high temperature (80°C).From these viewpoints, the content of ultra-high molecular weight polyolefin A is preferably 2 to 50% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 30% by mass, based on the total amount of the resin film for terminal.

[0050] The resin film for terminals may contain a component other than the ultra-high molecular weight polyolefin A in the layer containing the ultra-high molecular weight polyolefin A. The component other than the ultra-high molecular weight polyolefin A may be a base resin composition (hereinafter also referred to as "base resin"). In other words, the resin film for terminals may have a layer containing the ultra-high molecular weight polyolefin A and the base resin.

[0051] Examples of the base resin include polyolefins such as polyethylene, polypropylene, polybutene, polymethylpentene, and polynorbornene. The polyolefins may be homopolymers, random copolymers, or block copolymers. These polyolefins may be used alone or in combination of two or more.

[0052] The base resin is preferably combined so as to have excellent compatibility with the ultra-high molecular weight polyolefin A. For example, when the ultra-high molecular weight polyolefin A is ultra-high molecular weight polypropylene, the base resin preferably contains polypropylene, and when the ultra-high molecular weight polyolefin A is ultra-high molecular weight polyethylene, the base resin preferably contains polyethylene.

[0053] The base resin preferably contains polypropylene from the viewpoints of improving heat resistance, flexibility, adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and at high temperature (80°C), and adhesion between the resin film for terminal and the exterior material. Examples of polypropylene that can be used include homopolypropylene, random polypropylene, and block polypropylene. These polypropylenes can be used alone or in combination of two or more.

[0054] The weight average molecular weight of the base resin is 1.0 x 10 4 Over 2.0 x 10 5 may be less than 1.2 x 10 5 ~1.7×10 5 The molecular weight distribution of the base resin may be 2-10, or may be 4-8.

[0055] The melting point (Tm) of the base resin is preferably 130 to 220°C, more preferably 150 to 200°C, from the viewpoint of providing excellent insulating properties for the resin film for terminal and better adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and high temperature (80°C).

[0056] The content of the base resin may be 50 to 98 mass %, 50 to 95 mass %, or 70 to 90 mass % based on the total mass of the resin film for a terminal.

[0057] The resin film for terminals may be a single layer or may have multiple layers. When the resin film for terminals is a single layer, it consists only of a layer containing ultra-high molecular weight polyolefin A. When the resin film for terminals has multiple layers, at least one of the multiple layers may be a layer containing ultra-high molecular weight polyolefin A, and all of the layers may be layers containing ultra-high molecular weight polyolefin A. From the viewpoints of achieving better insulation, adhesion between the resin film for terminals and metal terminals at room temperature (25°C) and high temperature (80°C), and adhesion between the resin film for terminals and exterior materials, it is preferable that the resin film for terminals have multiple layers.

[0058] 3, the resin film for terminal 16 may have an innermost layer 31 (also referred to as a "first adhesive layer") that contacts the outer peripheral side surface of the metal terminal 14, an outermost layer 32 (also referred to as a "second adhesive layer") that contacts the exterior material 13, and an intermediate layer 33 disposed between the innermost layer 31 and the outermost layer 32. The resin film for terminal 16 may be three layers consisting of the innermost layer 31, the outermost layer 32, and the intermediate layer 33, or may be four or more layers including another layer.

[0059] The innermost layer 31 is disposed so as to cover the outer peripheral surface of the metal terminal 14, thereby sealing the metal terminal 14 in the circumferential direction and enabling the terminal resin film 16 to adhere closely to the metal terminal 14. Furthermore, the outermost layer 32 is fused to the exterior packaging material 13, thereby enabling the interior of the exterior packaging material 13 to be sealed.

[0060] In order to improve the appearance of the resin film for terminals and to improve the adhesion between the resin film for terminals and the metal terminals at room temperature (25°C) and high temperature (80°C), it is preferable that the intermediate layer and / or the outermost layer contain ultra-high molecular weight polyolefin A, and it is more preferable that, of the innermost layer, outermost layer and intermediate layer, only the intermediate layer contains ultra-high molecular weight polyolefin A.

[0061] [Innermost layer] The innermost layer 31 is a layer disposed on the surface of the resin film for terminal on the metal terminal side. From the viewpoint of achieving better adhesion to the metal terminal at room temperature (25°C) and high temperature (80°C), the innermost layer 31 preferably contains a resin having a polar group (hereinafter also referred to as "polar resin").

[0062] Examples of the polar group include a hydroxyl group, a glycidyl group, an amide group, an imino group, an oxazoline group, an acid anhydride group, a carboxyl group, an ester group, etc. From the viewpoint of reactivity, the polar group is preferably an acid anhydride group, and the acid anhydride group is more preferably a group derived from maleic anhydride.

[0063] Examples of polar resins include modified polyolefins having polar groups, polyhydroxypolyolefin oligomers, and ethylene / acrylic acid / glycidyl methacrylate copolymers. From the viewpoint of reactivity, preferred polar resins include polyolefins modified with acid anhydrides such as maleic anhydride. Examples of polyolefins include polypropylene, polyethylene, polybutene, polymethylpentene, and polynorbornene. The polyolefin preferably contains polypropylene from the viewpoints of heat resistance, flexibility, and superior adhesion to metal terminals at room temperature (25°C) and high temperature (80°C). These polar resins may be used alone or in combination of two or more.

[0064] Examples of polypropylene include homopolypropylene, random polypropylene, block polypropylene, low-order polypropylene, and modified polypropylene. Modified polypropylene is polypropylene having the polar group described above. Among these, random polypropylene, low-order polypropylene, and modified polypropylene are preferred from the viewpoints of heat resistance, flexibility, and superior adhesion to metal terminals at room temperature (25°C) and high temperature (80°C). As the modified polypropylene, acid-modified polypropylene is preferred, and acid-modified random polypropylene is more preferred, from the viewpoints of heat resistance, flexibility, and superior adhesion to metal terminals at room temperature (25°C) and high temperature (80°C).

[0065] Specific examples of polar resin products include polar resins having hydroxy groups such as "Poval" manufactured by Kuraray Co., Ltd. and "Mersen H" manufactured by Tosoh Corporation, polar resins having glycidyl groups such as "Modiper" manufactured by NOF Corporation and "LOTADER" and "BONDINE" manufactured by Arkema Inc., polar resins having amide groups such as "APOLHYA" manufactured by Arkema Inc., polar resins having imino groups such as "Admer IP" manufactured by Mitsui Chemicals Inc., and polar resins having oxazoline groups such as "Epocross" manufactured by Nippon Shokubai Co., Ltd. These polar resins can be used alone or in combination of two or more.

[0066] The melting point of the polar resin is preferably 80 to 180°C, more preferably 100 to 170°C, and even more preferably 120 to 165°C, from the viewpoint of excellent embeddability and heat resistance.

[0067] In order to obtain better adhesion to the metal terminal at room temperature (25°C) and at high temperature (80°C), the content of the polar resin in the innermost layer is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of the innermost layer. The content of the polar resin in the innermost layer may be substantially 100% by mass, based on the total amount of the innermost layer.

[0068] The innermost layer may contain a resin other than a polar resin. Examples of resins other than polar resins include polyolefins such as polypropylene, polyethylene, and polybutene. The innermost layer may contain ultra-high molecular weight polyolefin A and a base resin. These resins other than polar resins may be used alone or in combination of two or more.

[0069] In the innermost layer, the content of resins other than polar resins may be 50% by mass or less, based on the total amount of the innermost layer, and from the viewpoint of suppressing a decrease in cohesive force and maintaining sufficient adhesion with the metal terminal, it is preferably 40% by mass or less, and more preferably 20% by mass.

[0070] The innermost layer may contain additives other than the above components. Examples of additives include antioxidants, slip agents, flame retardants, light stabilizers, dehydrating agents, coloring pigments, tackifiers, and fillers. These additives may be used alone or in combination of two or more. Examples of coloring pigments include carbon black, quinacridone pigments, polyazo pigments, and isoindolinone pigments.

[0071] The thickness of the innermost layer is preferably 10 to 100 μm, and more preferably 15 to 50 μm. When the thickness of the innermost layer is 10 μm or more, the adhesion to the metal terminal is superior at room temperature (25°C) and at high temperature (80°C). Furthermore, when the thickness of the innermost layer is 100 μm or less, the cost of the resin film for terminals can be reduced.

[0072] The innermost layer may be a layer containing ultra-high molecular weight polyolefin A and a base resin. When the innermost layer is a layer containing ultra-high molecular weight polyolefin A, the content of ultra-high molecular weight polyolefin A may be 1 to 50 mass % or 1 to 20 mass % based on the total amount of the innermost layer.

[0073] [Outermost layer] The outermost layer 32 is a layer disposed on the surface of the resin film for terminal opposite to the innermost layer. That is, the innermost layer 31 is a layer disposed on the surface of the resin film for terminal facing the exterior material. The outermost layer 32 preferably contains the above-mentioned polar resin from the viewpoint of excellent adhesion to the exterior material. As the polar resin, polyolefin having a polar group is preferred, and polypropylene having a polar group is more preferred, from the viewpoint of excellent adhesion to the exterior material. Specific examples of polar resin products include the above-mentioned polar resins.

[0074] The melting point of the polar resin is preferably 80 to 180°C, more preferably 100 to 170°C, and even more preferably 120 to 165°C, from the viewpoint of excellent embeddability and heat resistance.

[0075] In the outermost layer, the content of the polar resin is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on the total amount of the outermost layer, from the viewpoint of better adhesion to the metal terminal at room temperature (25°C) and high temperature (80°C). The content of the polar resin in the outermost layer may be substantially 100% by mass, based on the total amount of the outermost layer.

[0076] The outermost layer preferably contains polypropylene having a structure with long chain branches (hereinafter also referred to as "long-chain branched PP") and polypropylene not having a structure with long chain branches, from the viewpoint of achieving excellent adhesion to the packaging material in a room temperature environment and easily maintaining sufficient adhesion to the packaging material even when exposed to a high-temperature environment.

[0077] The long-chain branched PP refers to a polypropylene having a branched structure due to molecular chains with a main chain carbon number of several tens or more and an average molecular weight of several hundred or more. The polypropylene having a long-chain branched structure may be a propylene homopolymer or copolymer. In the case of a propylene copolymer, the comonomer is at least one olefin selected from the group consisting of ethylene and α-olefins having 4 to 10 carbon atoms, and the content of the comonomer in the long-chain branched PP is preferably 3% by mass or less. From the viewpoint of excellent heat resistance and rigidity, the long-chain branched PP is preferably a propylene homopolymer.

[0078] Long-chain branched PP can be produced by electronic crosslinking or by synthesis using a metallocene catalyst. From the viewpoint of suppressing gel formation and obtaining sufficient strength, it is preferable that the long-chain branched PP is synthesized using a metallocene catalyst. Whether the long-chain branched PP has been synthesized using a metallocene catalyst can be confirmed by analyzing catalyst residues using analytical techniques such as infrared spectroscopy (IR), NMR spectroscopy, mass spectroscopy (MS), X-ray analysis, and Raman spectroscopy.

[0079] The melting point of the long-chain branched PP is preferably from 100 to 170°C, more preferably from 130 to 160°C, from the viewpoint of excellent embeddability and heat resistance.

[0080] In the outermost layer, the content of the long-chain branched PP is preferably 1 to 50% by mass, more preferably 3 to 30% by mass, and even more preferably 5 to 20% by mass, based on the total amount of the outermost layer. When the content of the long-chain branched PP is 1% by mass or more, foaming in the outermost layer can be further suppressed. When the content of the long-chain branched PP is 50% by mass or less, the embeddability is improved, sufficient adhesion to the exterior packaging material can be maintained, and curling of the resin film for terminal can be suppressed.

[0081] The polypropylene having no long chain branches means a polypropylene that does not fall under the category of the polypropylene having long chain branches. The polypropylene having no long chain branches may be a homopolypropylene, a random polypropylene, a block polypropylene, a low regular polypropylene, or the like. The polypropylene having no long chain branches may be modified.

[0082] The melting point of the polypropylene having no long chain branched structure is preferably 80 to 155°C, more preferably 100 to 150°C, and even more preferably 105 to 145°C, from the viewpoint of excellent heat resistance and adhesion to the exterior material.

[0083] The outermost layer preferably contains a filler from the viewpoint of suppressing foaming in the outermost layer. Examples of the filler include inorganic fillers such as aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, calcium carbonate, zirconium silicate, zinc oxide, barium sulfate, copper oxide, cobalt oxide, titanium oxide, tin oxide, iron oxide, antimony oxide, boron nitride, aluminum nitride, and silicon nitride. These inorganic fillers can be used alone or in combination of two or more.

[0084] The average particle size of the filler is preferably 0.1 to 25 μm. The content of the filler is preferably 0.05 to 10 mass %, more preferably 0.1 to 5 mass %, based on the total amount of the outermost layer. When the filler content is 0.05 mass % or more, the decrease in adhesion to the exterior material can be further suppressed. When the filler content is 10 mass % or less, sufficient adhesion to the exterior material can be maintained.

[0085] The outermost layer may contain resins and additives other than those described above. Examples of additives include antioxidants, slip agents, flame retardants, light stabilizers, dehydrating agents, coloring pigments, and tackifiers. These additives may be used alone or in combination of two or more. Examples of coloring pigments include carbon black, quinacridone pigments, polyazo pigments, and isoindolinone pigments.

[0086] The thickness of the outermost layer is preferably 10 to 100 μm, and more preferably 15 to 50 μm. When the thickness of the outermost layer is 10 μm or more, the adhesion to the exterior material is superior. Furthermore, when the thickness of the outermost layer is 100 μm or less, the cost of the resin film for terminals can be reduced.

[0087] The outermost layer may be composed of the same components as the innermost layer, or may be composed of different components. The outermost layer may contain ultra-high molecular weight polyolefin A and a base resin. When the outermost layer is a layer containing ultra-high molecular weight polyolefin A, the content of ultra-high molecular weight polyolefin A may be 1 to 50 mass % or 1 to 20 mass % based on the total amount of the outermost layer.

[0088] [Middle layer] The intermediate layer 33 is a layer disposed between the innermost layer 31 and the outermost layer 32. One side of the intermediate layer 33 may be covered by the innermost layer 31, and the other side may be covered by the outermost layer 32.

[0089] The intermediate layer has an insulating layer. The insulating layer is a layer that prevents deterioration of insulation due to contact between the exposed metal layer of the exterior material and the metal terminal caused by the sealant (sealant layer of the exterior material and the innermost and outermost layers of the resin film for terminal) flowing out during heat sealing. The insulating layer is preferably a layer containing ultra-high molecular weight polyolefin A.

[0090] The resin constituting the insulating layer may be polyolefin, polyamide, polycarbonate, polyphenylene ether, etc. Among these, polyolefin is preferred, polypropylene is more preferred, and block polypropylene is even more preferred, from the viewpoints of providing a better appearance for the resin film for terminal and better adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and at high temperature (80°C). These resins may be used alone or in combination of two or more.

[0091] The insulating layer preferably contains a filler from the viewpoint of suppressing foaming in the intermediate layer. As the filler, an inorganic filler that can be used in the outermost layer can be used. The inorganic fillers can be used alone or in combination of two or more. The average particle size of the filler is preferably 0.1 to 25 μm. The content of the filler is preferably 0.1 to 30 mass % and more preferably 1 to 15 mass % based on the total amount of the intermediate layer. When the content of the filler is 0.1 mass % or more, a decrease in adhesion with the metal terminal can be suppressed, and when the content of the filler is 30 mass % or less, sufficient embeddability can be maintained.

[0092] The insulating layer may contain a coloring pigment from the viewpoint of improving the visibility of the resin film for terminals. By improving the visibility of the resin film for terminals, the accuracy of inspection of the resin film for terminals (specifically, inspection of whether the resin film for terminals is in close contact with the metal terminal, inspection of the attachment position of the resin film for terminals relative to the metal terminal, etc.) can be improved. Examples of the coloring pigment include copper oxide, cobalt oxide, zinc oxide, titanium oxide, carbon black, barium sulfate, quinacridone pigments, polyazo pigments, and isoindolinone pigments.

[0093] The intermediate layer may be a single layer consisting of only the insulating layer described above, or may have multiple layers. That is, the intermediate layer may have a multilayer structure in which a resin layer other than the insulating layer is provided via an adhesive or the like. Examples of layers other than the insulating layer include a layer containing a resin having a crosslinked structure (crosslinked layer), a layer containing a filler and / or fiber (reinforced layer), etc.

[0094] The crosslinked layer contains a resin having a crosslinked structure. Examples of the resin having a crosslinked structure include crosslinked acrylic resin, epoxy resin, phenol resin, urea resin, melamine resin, polyurethane resin, and acid-modified polyolefin resin crosslinked with isocyanate or epoxy. These resins having a crosslinked structure can be used alone or in combination of two or more.

[0095] The reinforcing layer contains a filler and / or fiber and may be a layer in which the filler and / or fiber is dispersed in a polyolefin resin, a resin with a melting point of 200°C or higher, a resin with a crosslinked structure, or the like.

[0096] The filler may be any filler that can be used in the insulating layer, and the filler content may be 0.5 to 20 mass % based on the total mass of the reinforcing layer.

[0097] The fibers may be fibers containing cellulose resin, resins with a melting point of 200°C or higher, etc. These fibers may be used alone or in combination of two or more. The fiber width (fiber diameter) of the fibers may be 10 nm to 10 μm. The fiber content may be 0.5 to 70 mass% based on the total amount of the reinforcing layer. The fibers may form a nonwoven fabric.

[0098] The thickness of the intermediate layer (the total thickness of the intermediate layer when the intermediate layer has a multi-layer structure) may be 10 to 200 μm, or 20 to 100 μm. The thickness of the intermediate layer can be adjusted depending on the thickness of the metal terminal and the innermost layer, and if the innermost layer or the metal terminal is thick, the thickness of the intermediate layer 33 may also be increased accordingly.

[0099] The total thickness of the innermost layer, outermost layer, and intermediate layer (thickness of the resin film for terminals) is preferably 50 μm or more, more preferably 80 μm or more, from the viewpoints of excellent heat sealing properties, embeddability of metal terminals, and insulation properties, and is preferably 500 μm or less, more preferably 300 μm or less, from the viewpoints of reducing costs and achieving excellent sealing properties.

[0100] When the intermediate layer is an insulating layer, the thickness ratio of the innermost layer, intermediate layer, and outermost layer (innermost layer:intermediate layer:outermost layer) may be the same as that of the innermost layer and the outermost layer, such as 2:1:2, 1:2:1, 1:1:1, etc. Furthermore, the thickness ratio of the innermost layer, intermediate layer, and outermost layer (innermost layer:intermediate layer:outermost layer) may be such that the thickness of the innermost layer in contact with the metal terminal is thicker than that of the outermost layer, such as 3:1:1, 2:2:1, 5:3:2, etc., from the viewpoint of embeddability of the metal terminal, and may be such that the thickness of the outermost layer in contact with the exterior material is thicker than that of the innermost layer, such as 1:1:3, 1:2:2, 2:3:5, etc., from the viewpoint of adhesion to the exterior material.

[0101] When the innermost layer and the outermost layer have the same thickness, the ratio of their thicknesses to the thickness of the intermediate layer (innermost layer or outermost layer:intermediate layer) may be 1:3 to 3:1, or may be 1:2 to 2:1. When the innermost layer and the outermost layer have different thicknesses, the ratio of the innermost layer to the intermediate layer (innermost layer:intermediate layer) may be 4:1 to 1:1, or may be 3:1 to 1:1, and the ratio of the outermost layer to the intermediate layer (outermost layer:intermediate layer) may be 1:3 to 3:1, or may be 1:2 to 2:1. When the innermost layer and the outermost layer have different thicknesses, the ratio of the innermost layer to the outermost layer (innermost layer:outermost layer) is preferably 1:5 to 9:2, more preferably 3:10 to 7:2, and even more preferably 2:5 to 5:2, from the viewpoint of suppressing curling of the resin film for terminal. The ratio of the thickness of the innermost layer to the thickness of the outermost layer (innermost layer / outermost layer) is preferably 0.2 to 4.5, more preferably 0.3 to 3.5, and even more preferably 0.4 to 2.5, from the viewpoint of suppressing curling of the resin film for a terminal.

[0102] From the viewpoint of achieving superior insulation of the intermediate layer, processability of the resin film for terminals, and adhesion between the resin film for terminals and metal terminals at room temperature (25°C) and high temperature (80°C), the resin film for terminals preferably has a melt flow rate at 230°C of 0.1 to 2.5 g / 10 min for the innermost layer, a melt flow rate at 230°C of 0.1 to 2.5 g / 10 min for the outermost layer, and a melt flow rate at 230°C of 0.1 to 2.5 g / 10 min for the intermediate layer, and the difference between MFR1 and MFR3 (MFR1-MFR3) and the difference between MFR2 and MFR3 (MFR2-MFR3) are both 5 to 30 g / 10 min. The melt flow rates at 230°C can be measured in accordance with the method described in JIS K7121-1987.

[0103] The melt flow rate of the intermediate layer at 230°C is preferably 0.2 g / 10 min or more, and more preferably 0.5 g / 10 min or more, from the viewpoint of making the resin film for terminals easier to process, and is preferably 1.5 g / 10 min or less, and more preferably 1.0 g / 10 min or less, from the viewpoint of suppressing the flow of the intermediate layer and making it easier to maintain insulation properties.

[0104] The difference between the melt flow rate at 230°C of the innermost layer and the melt flow rate at 230°C of the intermediate layer, and the difference between the melt flow rate at 230°C of the outermost layer and the melt flow rate at 230°C of the intermediate layer are preferably 5.5 g / 10 min or more, and more preferably 6.0 g / 10 min or more, from the viewpoint of excellent embeddability of the metal terminal and better adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and high temperature (80°C); and from the viewpoint of excellent processability of the resin film for terminal, are preferably 20 g / 10 min or less, more preferably 15 g / 10 min or less, and even more preferably 10 g / 10 min or less.

[0105] From the viewpoint of improving the insulating properties of the intermediate layer, the processability of the resin film for terminals, and the adhesion between the resin film for terminals and the metal terminal at room temperature (25°C) and high temperature (80°C), it is preferable that the melting point (Tm1) of the innermost layer, the melting point (Tm2) of the outermost layer, and the melting point (Tm3) of the intermediate layer be 150 to 200°C, and that the difference between Tm3 and Tm1 (Tm3-Tm1) and the difference between Tm3 and Tm2 (Tm3-Tm2) be both 10 to 100°C.

[0106] The melting point of the intermediate layer is preferably 185°C or less, more preferably 170°C or less, from the viewpoint of making the terminal resin film easier to process, and is preferably 155°C or more, more preferably 160°C or more, from the viewpoint of suppressing the flow of the intermediate layer and making it easier to maintain insulation.

[0107] The difference between the melting point of the intermediate layer and the melting point of the innermost layer, and the difference between the melting point of the intermediate layer and the melting point of the innermost layer, are preferably 50°C or less, more preferably 35°C or less, from the viewpoint of excellent embeddability of the metal terminal and better adhesion between the resin film for terminal and the metal terminal at room temperature (25°C) and high temperature (80°C), and are preferably 15°C or more, more preferably 20°C or more, from the viewpoint of excellent processability of the resin film for terminal.

[0108] Although the preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to specific embodiments, and various modifications and changes are possible within the scope of the gist of the present disclosure described in the claims.

[0109] 3, the resin film for terminal 16 has been described as having a three-layer structure, but a second intermediate layer containing a resin such as ultra-high molecular weight polyolefin A or a base resin may be disposed between the intermediate layer 33 and the innermost layer 31, or between the intermediate layer 33 and the outermost layer 32. The second intermediate layer may be the above-mentioned cross-linked layer, reinforcing layer, or the like.

[0110] In this way, by placing a second intermediate layer between the intermediate layer 33 and the innermost layer 31, or between the intermediate layer 33 and the outermost layer 32, to form a multi-layer structure of four or more layers, the insulation between the intermediate layer 33 and the barrier layer 24 (metal layer) that constitutes the outer casing material 13, and the insulation between the intermediate layer 33 and the metal terminal 14 can be further improved.

[0111] A method for manufacturing the resin film for terminal 16 according to this embodiment will be described. The method for manufacturing the resin film for terminal 16 is not limited to the following. The resin film for terminal 16 can be manufactured using a film extrusion manufacturing device having a die such as a round die used in the inflation molding method or a T-die used in the push die method. The inflation molding method is preferred from the viewpoint of suppressing unevenness in the film thickness of the resin film for terminal.

[0112] As an example of a method for manufacturing the terminal resin film 16, a method for manufacturing the terminal resin film 16 by inflation molding (that is, a method using an inflation molding device) will be described.

[0113] First, base materials for the innermost layer 31, outermost layer 32, and intermediate layer 33 are prepared. Next, the base materials for the innermost layer 31, outermost layer 32, and intermediate layer 33 are supplied to an inflation molding machine. Next, the above three base materials are extruded from the extrusion section of the inflation molding machine to form a three-layer structure (a structure in which the innermost layer 31, outermost layer 32, and intermediate layer 33 are laminated), while air is supplied from inside the extruded three-layer laminate.

[0114] Then, while conveying the cylindrically inflated resin film for terminals 16, a guide section deforms the film into a flat shape, and a pair of pinch rolls folds the resin film for terminals 16 into a sheet. Both ends of the woven tube are slit, and the pair (two strips) of film are wound into a roll around a winding core, thereby producing the rolled resin film for terminals 16.

[0115] The extrusion temperature is preferably in the range of 130 to 300°C, more preferably 130 to 250°C. When the extrusion temperature is 130°C or higher, the resin constituting each layer is sufficiently melted, reducing the melt viscosity and stabilizing extrusion from the screw. When the extrusion temperature is 300°C or lower, oxidation and deterioration of the resin constituting each layer are suppressed, and deterioration in the quality of the resin film for terminal 16 can be prevented.

[0116] The screw rotation speed, blow ratio, take-up speed, etc. can be set appropriately taking into account the film thickness. The film thickness ratio of each layer of the resin film for terminal 16 can be adjusted by changing the rotation speed of each screw.

[0117] The resin film for terminal 16 according to this embodiment may be produced by dry lamination using an adhesive or by laminating formed insulating layers (insulating films) together by sandwich lamination.

[0118] 3, a description will be given of a fusion process for melt-bonding the resin film for terminal 16 and the exterior packaging material 13 according to this embodiment. In the fusion process, the resin film for terminal 16 and the exterior packaging material 13 are thermally fused together while simultaneously melting the outermost layer 32 by heating and bonding the outermost layer 32 to the exterior packaging material 13 by applying pressure.

[0119] In the fusion treatment, from the viewpoint of obtaining sufficient adhesion and sealing properties between the resin film for terminal 16 and the exterior packaging material 13, it is preferable to heat to a temperature equal to or higher than the melting point of the resin constituting the outermost layer 32.

[0120] The heating temperature of the terminal resin film 16 may be, for example, 140 to 170°C. The treatment time (total time of heating time and pressure application time) can be determined taking into consideration the adhesion to the exterior material and productivity. The treatment time can be set appropriately within the range of, for example, 1 to 60 seconds.

[0121] From the viewpoint of improving the production takt time (productivity) of the terminal resin film 16, heat fusion may be performed by shortening the pressurizing time at a temperature exceeding 170° C. In this case, the heating temperature may be, for example, higher than 170° C. and 230° C. or less, and the pressurizing time may be, for example, 3 to 20 seconds.

[0122] 3, a fusion process for melt-bonding the terminal resin film 16 and the metal terminal 14 according to this embodiment will be described. In the fusion process, the terminal resin film 16 and the metal terminal 14 are thermally fused together while simultaneously melting the innermost layer 31 by heating and bonding the innermost layer 31 and the metal terminal 14 by applying pressure.

[0123] In the fusion treatment, it is preferable to heat the terminal resin film 16 to a temperature equal to or higher than the melting point of the resin constituting the innermost layer 31 in order to obtain sufficient adhesion and sealing properties between the terminal resin film 16 and the metal terminal 14 .

[0124] The heating temperature of the terminal resin film 16 may be, for example, 140 to 170°C. The treatment time (total time of heating time and pressure application time) can be determined taking into consideration the adhesion to the metal terminal and productivity. The treatment time can be set appropriately within the range of, for example, 1 to 60 seconds.

[0125] From the viewpoint of improving the production takt time (productivity) of the terminal resin film 16, heat fusion may be performed at a temperature exceeding 170° C. for a short pressurizing time. In this case, the heating temperature may be, for example, higher than 170° C. and 230° C. or less, and the pressurizing time may be, for example, 3 to 20 seconds. [Example]

[0126] Hereinafter, the present disclosure will be specifically described based on examples and comparative examples, but the present disclosure is not limited to the following examples.

[0127] [Materials used] The materials used in the examples and comparative examples are shown in Table 1. In Table 1, PP means polypropylene, Mw means weight average molecular weight, Mw / Mn (weight average molecular weight / number average molecular weight), MFR means melt flow rate at 230°C, and Tm means melting point. [Table 1]

[0128] [Production of resin film for terminals] (Examples 1 to 20 and Comparative Examples 1 to 9) The components shown in Tables 2 and 3 were blended in the amounts shown in the tables (unit: mass%, abbreviated as "%" in the tables) and dry-blended to prepare the base material for each layer. The melt flow rate (MFR) of each layer was measured at 230°C according to the method described in JIS K7121-1987. Tables 2 and 3 show the MFR of the intermediate layer, the difference between the MFR of the outermost layer and the MFR of the intermediate layer, and the difference between the MFR of the innermost layer and the MFR of the intermediate layer. Furthermore, the heat of fusion of each layer was measured by DSC, and peaks corresponding to the melting points of each resin component were detected. Tables 2 and 3 show the melting point of the intermediate layer, the difference between the melting points of the intermediate layer and the outermost layer, and the difference between the melting points of the intermediate layer and the innermost layer.

[0129] Next, the outermost layer base material, the middle layer base material, and the innermost layer base material were set in an inflation film extrusion manufacturing apparatus (Co-OI type) manufactured by Sumitomo Heavy Industries Modern Co., Ltd., and the above three base materials were extruded using the film extrusion manufacturing apparatus to produce a resin film for terminals with a three-layer structure of outermost layer / middle layer / innermost layer (however, Example 19 and Comparative Example 9 were resin films for terminals with a single-layer structure consisting only of the middle layer). The melting temperature of each base material was 210°C. The thickness of each layer in the resin film for terminals in each Example was as shown in "Thickness (μm) outer / middle / inner" in Tables 2 and 3. Note that "outer / middle / inner" in Tables 2 and 3 means outermost layer (outer) / middle layer (middle) / innermost layer (inner).

[0130] [Evaluation of gel (appearance)] Fisheyes occurring during the production of resin films for terminals were evaluated according to the following criteria. Grades A, B, and C were considered acceptable, while grade D was considered unacceptable. The results are shown in Tables 2 and 3. A: The number of fish eyes with a major diameter of 0.5 μm or more is 2 / m 2 The following is the result. B: The number of fish eyes with a major diameter of 0.5 μm or more is 3 to 5 per m 2 is. C: The number of fish eyes with a major diameter of 0.5 μm or more is 6 to 8 per m 2 is. D: Number of fish eyes with a major diameter of 0.5 μm or more is 9 / m 2 That's all.

[0131] [Measurement of initial heat seal strength against lead (room temperature)] A sample of a resin film for terminals, cut to a size of 50 mm (TD) x 100 mm (MD), was folded in half to sandwich a 50 mm x 50 mm piece of chemically treated aluminum foil. The edge opposite the folded portion was heat-sealed over a 10 mm width at 150°C / 0.6 MPa / 5 seconds. A 15 mm-wide sample was then cut from the longitudinal center of the heat-sealed portion (see Figure 4) to prepare a sample for heat-seal strength measurement. In this evaluation, laminate 100 in Figure 4 is a laminate consisting of a resin film for terminals / aluminum foil / resin film for terminals. A T-peel test between the aluminum foil (lead) and the resin film for terminals was performed on the heat-sealed portion of this sample using a tensile tester (manufactured by Shimadzu Corporation) at room temperature (25°C) and a tensile speed of 50 mm / min in accordance with JIS Z1713. The initial heat-seal strength to the lead was evaluated based on the results obtained and the following evaluation criteria. The heat seal strength was measured by plotting the displacement (peel distance) on the horizontal axis and the peel strength on the vertical axis, and the first maximum value of the peel strength was used. Grades A, B, and C were considered to be pass, and D was considered to be fail. The results are shown in Tables 2 and 3. A: Heat seal strength is 25N / 15mm or more B: Heat seal strength is 20N / 15mm or more and less than 25N / 15mm C: Heat seal strength is 15N / 15mm or more and less than 20N / 15mm D: Heat seal strength is less than 15N / 15mm

[0132] [Measurement of heat seal strength against lead (80℃)] A sample of a resin film for terminals, cut to a size of 50 mm (TD) x 100 mm (MD), was folded in half to sandwich a 50 mm x 50 mm piece of chemically treated aluminum foil. The edge opposite the folded portion was heat-sealed over a 10 mm width at 150°C / 0.6 MPa / 5 seconds. A 15 mm-wide sample was then cut out from the longitudinal center of the heat-sealed portion (see Figure 4) to prepare a sample for heat-seal strength measurement. In this evaluation, laminate 100 in Figure 4 is a laminate consisting of a resin film for terminals / aluminum foil / resin film for terminals. A T-peel test between the aluminum foil (lead) and the resin film for terminals was performed on the heat-sealed portion of this sample using a tensile tester (manufactured by Shimadzu Corporation) at 80°C and a tensile speed of 50 mm / min in accordance with JIS Z1713. The heat-seal strength to the lead was evaluated based on the results obtained and the following evaluation criteria. The heat seal strength was measured by plotting the displacement (peel distance) on the horizontal axis and the peel strength on the vertical axis, and the first maximum value of the peel strength was used. Grades A, B, and C were considered to be pass, and D was considered to be fail. The results are shown in Tables 2 and 3. A: Heat seal strength is 12.5N / 15mm or more B: Heat seal strength is 10N / 15mm or more and less than 12.5N / 15mm C: Heat seal strength is 7.5N / 15mm or more and less than 10N / 15mm D: Heat seal strength is less than 7.5N / 15mm

[0133] [Insulation evaluation] The insulation between the negative electrode lead of the battery pack prepared above and the exterior material was measured using a tester. The insulation was evaluated based on the number of specimens that shorted out of 200 specimens, and the evaluation criteria below. A, B, or C was considered pass, and D was considered fail. The results are shown in Tables 2 and 3. A: Less than two short samples B: 2 or more but less than 4 short samples C: 4 or more but less than 6 short samples D: 6 or more short samples

[0134] [Table 2]

[0135] [Table 3] [Explanation of symbols]

[0136] 10...electricity storage device, 11...electricity storage device main body, 13...exterior material, 14...metal terminal, 14-1...metal terminal main body, 14-2...corrosion prevention layer, 16...terminal resin film, 21...inner layer, 22...inner layer side adhesive layer, 23-1, 23-2...corrosion prevention treatment layer, 24...barrier layer, 25...outer layer side adhesive layer, 26...outer layer, 31...innermost layer, 32...outermost layer, 33...intermediate layer

Claims

1. A resin film for a terminal is disposed so as to cover a part of an outer peripheral surface of a metal terminal electrically connected to an electricity storage device main body that constitutes an electricity storage device, Weight average molecular weight is 3.0 × 10 ５ ~1.0 x 10 ６ A resin film for a terminal, comprising a layer containing an ultra-high molecular weight polyolefin.

2. The resin film for terminals according to claim 1, wherein the content of the ultra-high molecular weight polyolefin is 5 to 50 mass% based on the total amount of the resin film for terminals.

3. The resin film for a terminal according to claim 1 or 2, wherein the ultra-high molecular weight polyolefin comprises polypropylene.

4. The resin film for a terminal according to any one of claims 1 to 3, which has a plurality of layers, at least one of which contains the ultra-high molecular weight polyolefin.

5. an innermost layer disposed on a surface on the metal terminal side, an outermost layer disposed on a surface opposite to the innermost layer, and an intermediate layer disposed between the innermost layer and the outermost layer; The resin film for a terminal according to any one of claims 1 to 4, wherein the intermediate layer and / or the outermost layer contains the ultra-high molecular weight polyolefin.

6. The resin film for a terminal according to claim 5 , wherein, of the innermost layer, the outermost layer, and the intermediate layer, only the intermediate layer contains the ultra-high molecular weight polyolefin.

7. The resin film for a terminal according to claim 5 or 6, wherein the innermost layer contains a resin having a polar group.

8. Melt flow rate MFR of the innermost layer at 230°C １ , the melt flow rate MFR of the outermost layer at 230°C ２ and the melt flow rate MFR of the intermediate layer at 230°C ３ Regarding The MFR ３ is 0.1 to 2.5 g / 10 min, The MFR １ and the MFR ３ Difference from (MFR １ -MFR ３ ), and the MFR ２ and the MFR ３ Difference from (MFR ２ -MFR ３ 8. The resin film for a terminal according to claim 5, wherein each of the values ​​of the linear strength, linear strength, and compressive strength is 5 to 30 g / 10 min.

9. The melting point Tm of the innermost layer １ , the melting point Tm of the outermost layer ２ and the melting point Tm of the intermediate layer ３ Regarding The Tm ３ is 150 to 200°C, The Tm ３ and the Tm １ The difference between ３ -Tm １ ), and the Tm ３ and the Tm ２ The difference between ３ -Tm ２ 9. The resin film for a terminal according to claim 5, wherein each of the temperatures is 10 to 100°C.

10. A method for producing a resin film for terminals according to any one of claims 1 to 9, comprising: A manufacturing method comprising forming the resin film for terminal by an inflation molding method.

11. a power storage device body; a metal terminal electrically connected to the electricity storage device body; an exterior material that holds the metal terminals and houses the electricity storage device main body; 10. An electricity storage device comprising: the terminal resin film according to claim 1 , which covers a part of the outer peripheral surface of the metal terminal and is disposed between the metal terminal and the exterior material.

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