Resin film for terminal and power storage device using the same

Abstract

To provide a resin film for a terminal having excellent adhesion to the terminal under a room temperature environment and a high temperature environment after contacting with an electrolyte even when the film is thickened.SOLUTION: A resin film for a terminal disposed so as to cover an outer peripheral surface of a part of a metal terminal electrically connected to a power storage device body constituting a power storage device, the resin film for a terminal having the following A layer and a laminated structure, the laminated structure being formed by laminating the following B layer, the following C layer, and the following B layer in this order: The layer A is a layer formed by using a resin composition containing an acid-modified polyolefin resin having a melting point of 100 °C or more and 170 °C or less. The layer B is a layer formed by using a resin composition containing a first polyolefin resin having a melting point of 100 °C or higher and lower than 160 °C and a second polyolefin resin having a melting point of 160 °C or higher and 170 °C or lower. A layer formed by using a resin composition containing a polyolefin resin having a melting point of 160 °C or higher and 170 °C or lower.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention 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 equipped 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 and 2). Typically, the terminal resin film is fused to the metal terminal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6706014 [Patent Document 2] Patent No. 6402844 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, metal terminals have become thicker as batteries have become larger in capacity, and this has led to a trend toward thicker terminal resin films. However, if a conventional thin terminal resin film is simply made thicker, the adhesion of the terminal resin film to the metal terminal is likely to decrease after contact with an electrolyte solution at room temperature or at high temperatures, which can easily lead to peeling.

[0007] The present disclosure has been made in consideration of the problems associated with the above-described conventional technologies, and aims to provide a resin film for terminals that has excellent adhesion to terminals in room temperature and high temperature environments after contact with an electrolyte solution, even when the film is thickened, and an electricity 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 arranged to cover the outer peripheral surface of a portion of a metal terminal that is electrically connected to a main body of an electricity storage device that constitutes an electricity storage device, the resin film for a terminal having a layer A described below and a laminated structure, and the laminated structure is formed by laminating a layer B described below, a layer C described below, and a layer B described below in this order. Layer A: A layer formed using a resin composition containing an acid-modified polyolefin resin having a melting point of 100°C or higher and 170°C or lower. Layer B: A layer formed using a resin composition containing a first polyolefin resin having a melting point of 100°C or more and less than 160°C, and a second polyolefin resin having a melting point of 160°C or more and 170°C or less. Layer C: A layer formed using a resin composition containing a polyolefin resin having a melting point of 160°C or higher and 170°C or lower.

[0009] According to the above-mentioned resin film for terminals, because the resin film for terminals has the above-mentioned A layer and the above-mentioned laminated structure, even if the resin film for terminals is made thick, it is possible for the resin film to have excellent adhesion to the terminals in room temperature and high temperature environments after coming into contact with the electrolyte.

[0010] In the resin film for terminals, the mass ratio R of the first polyolefin resin to the second polyolefin resin in the layer B is preferably 0.1 to 9. When the mass ratio R is 0.1 or more, the adhesion of the resin film for terminals to terminals in a room temperature environment after contact with an electrolytic solution can be further improved. Furthermore, when the mass ratio R is 9 or less, the adhesion of the resin film for terminals to terminals in a high temperature environment after contact with an electrolytic solution can be further improved.

[0011] In the resin film for terminals, it is preferable that in Layer B, the first polyolefin resin has a tensile modulus of 550 MPa to less than 1000 MPa and a tensile yield stress of 15 MPa to less than 23 MPa, and the second polyolefin resin has a tensile modulus of 1000 MPa to 1500 MPa and a tensile yield stress of 23 MPa to 35 MPa. Having the tensile moduli of the first polyolefin resin and the second polyolefin resin each equal to or greater than the lower limit can further improve the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolytic solution. Having the tensile yield stresses of the first polyolefin resin and the second polyolefin resin each equal to or greater than the lower limit can further improve the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolytic solution. Furthermore, having the tensile modulus of the first polyolefin resin less than 1000 MPa can further improve the adhesion of the resin film for terminals to terminals in a room-temperature environment after contact with an electrolytic solution. When the second polyolefin resin has a tensile modulus of 1500 MPa or less, the adhesion of the resin film for terminals to the terminals in a room temperature environment after contact with the electrolyte can be further improved. When the first polyolefin resin has a tensile yield stress of less than 23 MPa, the adhesion of the resin film for terminals to the terminals in a room temperature environment can be further improved. When the second polyolefin resin has a tensile yield stress of 35 MPa or less, the adhesion of the resin film for terminals to the terminals in a room temperature environment can be further improved.

[0012] In the resin film for terminal, the first polyolefin resin in the layer B has a strength of 885 kg / m 3More than 895kg / m 3 and the second polyolefin resin has a density of less than 895 kg / m 3 More than 910kg / m 3 It is preferable that the resin film for a terminal has a density of 1000 to 2000 kJ / cm2 or less. When the densities of the first polyolefin resin and the second polyolefin resin are each equal to or greater than the above-mentioned lower limit, the adhesion of the resin film for a terminal to a terminal in a high-temperature environment after contact with an electrolytic solution can be further improved. When the density of the first polyolefin resin is less than the above-mentioned upper limit, the adhesion of the resin film for a terminal to a terminal in a room temperature environment after contact with an electrolytic solution can be further improved. When the density of the second polyolefin resin is equal to or less than the above-mentioned upper limit, the adhesion of the resin film for a terminal to a terminal in a room temperature environment after contact with an electrolytic solution can be further improved.

[0013] In the resin film for terminals, it is preferable that in Layer B, the first polyolefin resin has an MFR of 1.0 to 10.0 g / 10 min at 230°C, and the second polyolefin resin has an MFR of 0.05 g / 10 min or more and less than 1.0 g / 10 min. Having a first polyolefin resin with an MFR of 1.0 g / 10 min or more at 230°C can further improve the adhesion of the resin film for terminals to terminals in a room temperature environment after contact with an electrolytic solution. Having a first polyolefin resin with an MFR of 10.0 g / 10 min or less at 230°C can further improve the adhesion of the resin film for terminals to terminals in a high temperature environment after contact with an electrolytic solution. Having a second polyolefin resin with an MFR of 0.05 g / 10 min or more at 230°C can further improve the adhesion of the resin film for terminals to terminals in a room temperature environment after contact with an electrolytic solution. Furthermore, when the second polyolefin resin has an MFR of less than 1.0 g / 10 min at 230° C., the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolyte can be further improved.

[0014] The resin film for a terminal is preferably formed by laminating, in this order, the Layer A, the laminated structure, and the Layer A. In this case, the Layer A is formed using a resin composition containing an acid-modified polyolefin resin, which further improves the adhesion between the metal terminal and the resin film for a terminal.

[0015] The resin film for a terminal may have a thickness of 160 μm or more.

[0016] 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 that sandwiches the metal terminal and houses the electricity storage device main body; and a resin film for terminals of the present disclosure that covers a portion of the outer peripheral surface of the metal terminal and is disposed between the metal terminal and the exterior material.

[0017] According to this electricity storage device, even if the terminal resin film is thickened, after coming into contact with the electrolyte, it has excellent adhesion to the terminal at room temperature and at high temperature, thereby preventing leakage of the electrolyte at room temperature and at high temperature. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide a resin film for terminals that has excellent adhesion to terminals in room temperature and high temperature environments after contact with an electrolyte solution, even when the film is thickened, and an electricity storage device using the same. [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] 1 is a schematic cross-sectional view showing one embodiment of a resin film for a terminal. [Figure 5] FIG. 2 is a schematic diagram illustrating a method for preparing a sample for measuring heat seal strength to aluminum foil 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] [Energy storage devices] 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 power storage device body 11 is a battery body that charges and discharges. The exterior material 13 covers the surface of the power storage device body 11 and is disposed so as to come into contact with part of the resin film 16 for terminals.

[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 the following Layer A and a laminated structure, and the laminated structure is formed by laminating the following Layer B, the following Layer C, and the following Layer B in this order. Layer A: A layer formed using a resin composition containing an acid-modified polyolefin resin having a melting point of 100°C or higher and 170°C or lower. Layer B: A layer formed using a resin composition containing a first polyolefin resin having a melting point of 100°C or more and less than 160°C, and a second polyolefin resin having a melting point of 160°C or more and 170°C or less. Layer C: A layer formed using a resin composition containing a polyolefin resin having a melting point of 160°C or higher and 170°C or lower.

[0041] The melting points of Layers A, B, and C are values ​​measured using a differential scanning calorimeter (DSC) in accordance with ASTM D2117, and can be determined by reading the temperature at the peak top, which is the peak with the greatest heat of dissolution. If multiple melting peaks exist, the temperature at the peak with the greatest heat of dissolution is referred to.

[0042] Fig. 4 is a schematic cross-sectional view showing one embodiment of the resin film for a terminal according to the present embodiment. The resin film for a terminal 16 shown in Fig. 4 is formed by laminating an A layer 1, a laminate structure 8, and an A layer 7 in this order, and the laminate structure 8 is formed by laminating a B layer 2, a C layer 4, and a B layer 6 in this order from the A layer 1 side. That is, the resin film for a terminal 16 has a structure in which an A layer 1, a B layer 2, a C layer 4, a B layer 6, and an A layer 7 are laminated in this order. Below, the A layer, the B layer, and the C layer will each be described.

[0043] Layer A is formed using a resin composition containing an acid-modified polyolefin resin. Examples of acid-modified polyolefin resins include graft-modified resins obtained by graft-modifying polyolefin resins with maleic anhydride, carboxylic acid, sulfonic acid, and derivatives thereof, and copolymer resins obtained by copolymerizing olefins with maleic anhydride, carboxylic acid, sulfonic acid, and derivatives thereof. Among these, graft-modified resins are preferred from the viewpoint of adhesion to metal terminals. Acid-modified polyolefin resins modified with maleic anhydride are preferred because they tend to have improved heat seal strength compared to resins modified with other groups. Examples of the polyolefin resin include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymers; homo-, block-, or random polypropylene; propylene-α-olefin copolymers; polybutene; polymethylpentene; and polynorbornene. Among these, the polyolefin resin preferably contains polypropylene from the viewpoints of heat resistance, processability, and adhesion to the exterior material. The acid-modified polyolefin resin is preferably an acid-modified random polypropylene copolymer. These polyolefin resins may be used alone or in combination. The resin composition used to form the A layer may or may not contain a resin other than the acid-modified polyolefin resin.

[0044] The modification rate of the polyolefin resin with an acid (for example, the mass of the portion derived from maleic anhydride relative to the total mass of maleic anhydride-modified polypropylene) is preferably 0.1 to 20 mass%, more preferably 0.3 to 5 mass%, from the viewpoint of improving heat seal strength.

[0045] The melting point of the acid-modified polyolefin resin used in Layer A is 100 to 170°C, more preferably 120 to 160°C, and even more preferably 130 to 150°C. When the melting point of the acid-modified polyolefin resin is 100°C or higher, the adhesion of the resin film for terminals to metal terminals in a high-temperature environment after contact with an electrolytic solution can be further improved. Furthermore, when the melting point of the acid-modified polyolefin resin is less than 170°C, the adhesion of the resin film for terminals to terminals in a room-temperature environment after contact with an electrolytic solution can be further improved.

[0046] The resin composition used to form Layer A may contain resin additives such as antioxidants, slip agents, flame retardants, light stabilizers, dehydrating agents, coloring pigments, tackifiers, fillers, and nucleating agents. These additives may be blended in combination. In particular, from the viewpoint of improving the visibility of the resin film for terminals, the resin composition may contain coloring pigments and fillers.

[0047] Examples of color pigments include carbon black, quinacridone pigments, polyazo pigments, and isoindolinone pigments.

[0048] 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.

[0049] The thickness of Layer A (thickness per layer) is preferably 10 to 150 μm, more preferably 15 to 100 μm, and even more preferably 20 to 50 μm. When Layer A has a thickness of 10 μm or more, the adhesion between the metal terminal or exterior material and the resin film for terminal in a high-temperature environment can be further improved after contact with the electrolyte. Furthermore, from the viewpoints of processability and the breaking strength of the film, the thickness of Layer A is preferably 150 μm or less.

[0050] The MFR of Layer A at 230°C is 2.0 to 50 g / 10 min, preferably 3.0 to 25 g / 10 min, and more preferably 5.0 to 15 g / 10 min. When Layer A has an MFR of 2.0 g / 10 min or more, the breaking elongation of the resin film for terminals can be improved. Furthermore, when Layer A has an MFR of 50 g / 10 min or less, the breaking strength of the resin film for terminals can be improved.

[0051] Layer B is formed using a resin composition containing a first polyolefin resin and a second polyolefin resin. Examples of the first polyolefin resin and the second polyolefin resin include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymer; homo-, block-, or random polypropylene; propylene-α-olefin copolymer; polybutene; polymethylpentene; and polynorbornene. Among these, the first polyolefin resin and the second polyolefin resin preferably contain polypropylene from the viewpoints of heat seal strength and processability. The first polyolefin resin and the second polyolefin resin used in layer B may be acid-modified polyolefin resins or unmodified polyolefin resins, but unmodified polyolefin resins are preferred from the viewpoint of insulating properties. The first polyolefin resin is preferably a random polypropylene copolymer, and the second polyolefin resin is preferably a block polypropylene copolymer. The first polyolefin resin and the second polyolefin resin may each be used alone or in combination of two or more types. The resin composition used to form layer B may or may not contain resins other than the first polyolefin resin and the second polyolefin resin.

[0052] The melting point of the first polyolefin resin used in Layer B is 100°C or higher and lower than 160°C, preferably 110 to 150°C, and more preferably 120 to 140°C. When the melting point of the first polyolefin resin is 100°C or higher, the adhesion of the resin film for terminals to metal terminals in a high-temperature environment after contact with an electrolytic solution can be further improved. Furthermore, when the melting point of the first polyolefin resin is 160°C or lower, the adhesion of the resin film for terminals to terminals in a room-temperature environment after contact with an electrolytic solution can be further improved.

[0053] The melting point of the second polyolefin resin used in Layer B is 160°C or higher and 170°C or lower, preferably 162°C or higher and 168°C or lower, and more preferably 163°C or higher and 166°C or higher. When the melting point of the second polyolefin resin is 160°C or higher, the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolytic solution can be further improved. Furthermore, when the melting point of the second polyolefin resin is 170°C or lower, the adhesion of the resin film for terminals to terminals in a room-temperature environment after contact with an electrolytic solution can be further improved.

[0054] The resin composition used to form Layer B may contain resin additives such as antioxidants, slip agents, flame retardants, light stabilizers, dehydrating agents, color pigments, tackifiers, fillers, and nucleating agents. These additives may be blended in combination. In particular, from the viewpoint of improving the visibility of the resin film for terminals, the resin composition may contain color pigments and fillers. Examples of color pigments and fillers include those similar to those used for Layer A.

[0055] The thickness of Layer B (thickness per layer) is preferably 10 to 150 μm, more preferably 15 to 100 μm, and even more preferably 20 to 50 μm. When the thickness of Layer B is 10 μm or more, the adhesion between the exterior packaging material and the resin film for terminals in a high-temperature environment can be further improved. Furthermore, from the viewpoint of processability and the breaking elongation of the film, the thickness of Layer B is preferably 150 μm or less.

[0056] In Layer B, the mass ratio R of the first polyolefin resin to the second polyolefin resin is preferably 0.1 to 9, more preferably 0.3 to 8, and even more preferably 0.5 to 7. When R is 0.1 or more, the adhesion of the resin film for a terminal to a terminal in a room temperature environment after contact with an electrolytic solution can be further improved. Furthermore, when R is 9 or less, the adhesion of the resin film for a terminal to a terminal in a high temperature environment after contact with an electrolytic solution can be further improved.

[0057] In Layer B, the first polyolefin resin preferably has a tensile modulus of 550 MPa or more and less than 1000 MPa and a tensile yield stress of 15 MPa or more and less than 23 MPa, and the second polyolefin resin preferably has a tensile modulus of 1000 MPa or more and less than 1500 MPa and a tensile yield stress of 23 MPa or more and less than 35 MPa. Having the tensile moduli of the first polyolefin resin and the second polyolefin resin each equal to or greater than the above-mentioned lower limits further improves the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolytic solution. Having the tensile yield stresses of the first polyolefin resin and the second polyolefin resin each equal to or greater than the above-mentioned lower limits further improves the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolytic solution. Furthermore, having the tensile modulus of the first polyolefin resin less than 1000 MPa further improves the adhesion of the resin film for terminals to terminals in a room-temperature environment after contact with an electrolytic solution. When the second polyolefin resin has a tensile modulus of 1500 MPa or less, the adhesion of the resin film for terminals to the terminals in a room temperature environment after contact with the electrolyte can be further improved. When the first polyolefin resin has a tensile yield stress of less than 23 MPa, the adhesion of the resin film for terminals to the terminals in a room temperature environment can be further improved. When the second polyolefin resin has a tensile yield stress of 35 MPa or less, the adhesion of the resin film for terminals to the terminals in a room temperature environment can be further improved.

[0058] The tensile modulus of the first polyolefin resin is more preferably 570 to 750 MPa, and even more preferably 600 to 700 MPa. The tensile yield stress of the first polyolefin resin is more preferably 16 MPa or more and 22 MPa or less, and even more preferably 17 to 21 MPa.

[0059] The second polyolefin resin has a tensile modulus of preferably 1100 to 1450 MPa, and more preferably 1300 to 1400 MPa, and a tensile yield stress of preferably 23 to 32 MPa, and more preferably 25 to 30 MPa.

[0060] In the B layer, the first polyolefin resin is 885 kg / m 3 More than 895kg / m 3 and the second polyolefin resin has a density of less than 895 kg / m 3 More than 910kg / m 3 When the densities of the first polyolefin resin and the second polyolefin resin are each equal to or greater than the lower limit, the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolytic solution can be further improved. 3 When the density of the second polyolefin resin is less than 910 kg / m, the adhesion of the resin film for terminals to the terminals in a room temperature environment after contact with the electrolyte can be further improved. 3 By satisfying this condition, the adhesiveness of the resin film for terminals to the terminals in a room temperature environment after contact with the electrolytic solution can be further improved.

[0061] The density of the first polyolefin resin is 885 to 893 kg / m 3 More preferably, it is 887 to 891 kg / m 3 The density of the second polyolefin resin is more preferably 897 to 905 kg / m 3 It is more preferable that:

[0062] Preferably, the first polyolefin resin of Layer B has an MFR of 1.0 to 10.0 g / 10 min at 230°C, and the second polyolefin resin of Layer B has an MFR of 0.05 g / 10 min or more and less than 1.0 g / 10 min. Having a first polyolefin resin with an MFR of 1.0 g / 10 min or more at 230°C further improves the adhesion of the resin film for a terminal to a terminal in a room temperature environment after contact with an electrolytic solution. Having a first polyolefin resin with an MFR of 10.0 g / 10 min or less at 230°C further improves the adhesion of the resin film for a terminal to a terminal in a high temperature environment after contact with an electrolytic solution. Having a second polyolefin resin with an MFR of 0.05 g / 10 min or more at 230°C further improves the adhesion of the resin film for a terminal to a terminal in a room temperature environment after contact with an electrolytic solution. Furthermore, when the second polyolefin resin has an MFR of less than 1.0 g / 10 min at 230° C., the adhesion of the resin film for terminals to terminals in a high-temperature environment after contact with an electrolyte can be further improved.

[0063] The MFR at 230°C of the first polyolefin resin of Layer B is more preferably 1.0 to 3.0 g / 10 min, and even more preferably 1.2 to 2.0 g / 10 min. The MFR of the second polyolefin resin of Layer B is more preferably 0.1 g / 10 min or more but less than 1.0 g / 10 min, and even more preferably 0.3 to 0.8 g / 10 min.

[0064] The C layer is formed using a resin composition containing a polyolefin resin. Examples of the unmodified polyolefin resin include low-density, medium-density, and high-density polyethylene; ethylene-α-olefin copolymer; homo-, block-, or random polypropylene; propylene-α-olefin copolymer; polybutene; polymethylpentene; and polynorbornene. Among these, the polyolefin resin preferably contains polypropylene from the viewpoints of heat seal strength and processability. The polyolefin resin used in the C layer may be an acid-modified polyolefin resin or an unmodified polyolefin resin, but is preferably an unmodified polyolefin resin from the viewpoint of insulating properties. The polyolefin resin is preferably a block polypropylene copolymer. These polyolefin resins may be used alone or in combination of two or more. Furthermore, from the viewpoint of interlayer adhesion between the C layer and the B layer, the polyolefin resin used in the C layer is preferably the same as the second polyolefin resin used in the B layer. Furthermore, the resin composition used to form the C layer may or may not contain resins other than the polyolefin resin. In addition, it is preferable that the resin composition used to form layer C contains only unmodified polyolefin resin as the polyolefin resin and does not contain acid-modified polyolefin resin, from the viewpoint of adhesion between the metal terminal and the terminal resin film in a high-temperature environment after contact with the electrolyte.

[0065] The melting point of the polyolefin resin used in Layer C is 160 to 170° C., and more preferably 160 to 165° C. When the melting point of the polyolefin resin is 160° C. or higher, the adhesion to the metal terminal 14 in a high-temperature environment after contact with the electrolyte can be further improved. Furthermore, when the melting point of the polyolefin resin is 170° C. or lower, the adhesion of the resin film for terminal to the terminal in a room-temperature environment after contact with the electrolyte can be further improved.

[0066] The melting point of the polyolefin resin used in the C layer is Tm C (℃), the melting point of the polyolefin resin used in layer B is Tm B (℃), TmC ≧Tm B It is preferable that the condition of Tm C -Tm B The value of Tm is more preferably 1 to 25 (°C), and even more preferably 2 to 15 (°C). C ≧Tm B By satisfying the above condition, it is possible to further suppress the decrease in heat seal strength in a high temperature environment after contact with the electrolyte. C -Tm B When the value is 25 (° C.) or less, the processability of the resin film for terminals can be improved.

[0067] The resin composition used to form Layer C may contain resin additives such as antioxidants, slip agents, flame retardants, light stabilizers, dehydrating agents, color pigments, tackifiers, fillers, and nucleating agents. These additives may be blended in combination. In particular, from the viewpoint of improving the visibility of the resin film for terminals, the resin composition may contain color pigments and fillers. Examples of color pigments and fillers include those similar to those used for Layer A.

[0068] The thickness of Layer C (thickness per layer) is preferably 2 to 150 μm, more preferably 3 to 100 μm, and even more preferably 4 to 50 μm. When Layer C has a thickness of 2 μm or more, the adhesion between the packaging material and the resin film for terminal in a high-temperature environment after contact with the electrolyte can be improved. Furthermore, from the viewpoints of processability and the breaking elongation of the film, the thickness of Layer C is preferably 150 μm or less.

[0069] The MFR of Layer C at 230°C is preferably 0.05 to 50 g / 10 min, more preferably 1.0 to 25 g / 10 min, and even more preferably 2.0 to 15 g / 10 min. When Layer C has an MFR of 0.05 g / 10 min or more, the breaking elongation of the resin film for terminals can be improved. Furthermore, when Layer C has an MFR of 50 g / 10 min or less, the breaking strength of the resin film for terminals can be improved.

[0070] The total thickness of the resin film for a terminal may be 160 μm or more, 175 μm or more, or 200 μm or more. The upper limit of the total thickness of the resin film for a terminal is not particularly limited, but may be, for example, 1000 μm or less.

[0071] Among the layers that make up the resin film for terminals, the total thickness of the layers that correspond to layer A is T A (μm), the total thickness of the layers corresponding to layer B is T B (μm), T A ≧T B It is preferable to satisfy the condition T A / T B The value of T is more preferably 1.0 to 1.5. A / T B When the value is within the above range, the heat seal strength can be further improved.

[0072] The thickness of the laminated structure (B layer / C layer / B layer) accounts for preferably 25 to 75% of the total thickness of the resin film for terminal, and more preferably 35 to 65%. When the thickness of the laminated structure accounts for 25% or more, the adhesion of the resin film for terminal to the terminal in a room temperature environment after contact with an electrolytic solution can be further improved. When the thickness of the laminated structure accounts for 75% or less, the adhesion of the resin film for terminal to the terminal in a high temperature environment after contact with an electrolytic solution can be further improved.

[0073] The total thickness ratio of the layer B in the laminate structure is preferably 30 to 80%, more preferably 40 to 70%. When the total thickness ratio of the layer B in the laminate structure is 30% or more, the adhesion of the resin film for a terminal to a metal terminal in a room temperature environment after contact with an electrolytic solution can be further improved. When the total thickness ratio of the layer B in the laminate structure is 80% or less, the adhesion of the resin film for a terminal to a metal terminal in a high temperature environment after contact with an electrolytic solution can be further improved.

[0074] In the resin film for terminal of this embodiment, the multiple A layers may be layers formed using the same resin or layers formed using different resins. The multiple A layers may be layers formed using the same resin composition or layers formed using different resin compositions. Furthermore, the thickness, melting point, and MFR of the multiple A layers may be the same or different. From the viewpoint of processability and curl suppression of the resin film for terminal, it is preferable that the above-mentioned configurations of the multiple A layers are all the same.

[0075] In the resin film for terminals of this embodiment, the multiple B layers may be layers formed using the same resin or different resins. The multiple B layers may be layers formed using the same resin composition or different resin compositions. Furthermore, the thickness, melting point, and MFR of the multiple B layers may be the same or different. From the viewpoint of processability and curl suppression of the resin film for terminals, it is preferable that the above-described configurations of the multiple B layers are all the same.

[0076] In the resin film for terminal of this embodiment, when multiple C layers are present, the multiple C layers may be layers formed using the same resin or layers formed using different resins. Furthermore, the multiple C layers may be layers formed using the same resin composition or layers formed using different resin compositions. Furthermore, the thickness, melting point, and MFR of the multiple C layers may be the same or different. From the viewpoint of processability and curl suppression of the resin film for terminal, it is preferable that the above-mentioned configurations of the multiple C layers are all the same.

[0077] When the resin film for a terminal of this embodiment has a laminated structure of A layer / B layer / C layer / B layer / A layer, the layers may be the same thickness or different thicknesses. The thickness ratio of the layers in the laminated structure may be, for example, 2:1:1:1:24:2:1:2:4, with the A layer being thicker than the B and C layers. From the viewpoint of filling the gap between the metal terminal and the resin film for a terminal, the thickness ratio of the layers in the laminated structure may be, for example, 1:1:1:1:3, with one of the A layers (the A layer on the metal terminal side) being thicker. It is preferable that the C layer be thinner than the A and B layers.

[0078] The resin film for a terminal of this embodiment may contain layers other than Layer A, Layer B, and Layer C (layers that do not fall under any of Layer A, Layer B, and Layer C), but it is preferable that it does not contain any other layers. In other words, it is preferable that all of the layers constituting the resin film for a terminal fall under at least one layer selected from the group consisting of Layer A, Layer B, and Layer C.

[0079] In the resin film for terminal of this embodiment, from the viewpoint of adhesion, it is preferable that at least the outermost layer on the metal terminal side is Layer A. On the other hand, the outermost layer on the exterior packaging material side does not have to be Layer A and may be, for example, a layer using an unmodified polyolefin resin, but from the viewpoint of handling the resin film for terminal and suppressing curling, it is preferable that the outermost layers on both sides are Layer A.

[0080] 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.

[0081] [Method of manufacturing resin film for terminals] Next, a method for manufacturing the terminal resin film 16 according to this embodiment will be described. The method for manufacturing the terminal resin film 16 is not limited to the following.

[0082] When the resin film for terminal 16 has a five-layer structure of A layer / B layer / C layer / B layer / A layer, the five layers may be laminated by coextrusion, or some of the layers may be formed in advance and then laminated by sandwich lamination. For example, a three-layer film consisting of A layer / B layer / C layers and the A layer may be formed in advance, and then the three-layer film and the A layer may be laminated by sandwich lamination using a resin composition constituting the B layer, or a three-layer film consisting of A layer / B layer / C layers may be formed in advance, and then a two-layer film consisting of B layer / A layer may be extruded and laminated on top of it.

[0083] Alternatively, a three-layer film consisting of Layer A, Layer B, and Layer C may be formed in advance, and two sheets of the three-layer film may be laminated together by dry lamination using an adhesive composition. From the viewpoint of interlayer adhesion between the C layers of the three-layer film, it is preferable to use an adhesive composition containing a resin of the same type as the polyolefin resin in the resin composition constituting Layer C. The resin of the same type refers to an unmodified polyolefin resin when the polyolefin resin in the resin composition constituting Layer C is an unmodified polyolefin resin, and to an acid-modified polyolefin resin when the polyolefin resin is an acid-modified polyolefin resin.

[0084] The three-layer film or the like that is formed in advance can be produced using a co-extrusion method such as a T-die extrusion method or an inflation method, but from the viewpoint of film thickness stability, it is preferable to produce it using an inflation method.

[0085] Even when the resin film for terminal 16 has six or more layers, it can be produced by appropriately using the above-mentioned production method.

[0086] As an example of a method for producing the resin film for terminal 16, a method for producing a five-layer film by an inflation method will be described.

[0087] First, base materials for layers A, B, C, B, and A are prepared. Next, the base materials for layers A, B, C, B, and A are supplied to an inflation molding machine. Next, the five base materials are extruded from the extrusion section of the inflation molding machine to form a five-layer structure (a structure in which layers A, B, C, B, and A are laminated), while air is supplied from inside the extruded five-layer laminate.

[0088] The cylindrically inflated five-layer film is then conveyed and flattened by a guide, after which the five-layer film is folded into a sheet by a pair of pinch rolls. Both ends of the folded tube are slit, and the pair of films (two strips) are wound into a roll around a winding core, producing a roll of five-layer film. In this way, the resin film for terminal 16 is produced.

[0089] 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 resins constituting each layer are 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 resins constituting each layer are suppressed, preventing deterioration in the quality of the five-layer film.

[0090] 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 in a five-layer film can be adjusted by changing the rotation speed of each screw.

[0091] [Method for fusing resin film for terminals] A fusion process for melt-bonding the resin film for terminal 16 and the exterior packaging material 13 shown in Fig. 4 will be described below. The case where the layer A 1 of the resin film for terminal 16 shown in Fig. 4 is arranged to face the metal terminal side and the layer A 7 to face the exterior packaging material side will be described below.

[0092] In the fusion process, the A layer 7 is melted by heating and the A layer 7 and the exterior material 13 are adhered to each other by applying pressure, thereby thermally fusing the terminal resin film 16 and the exterior material 13 together.

[0093] 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 A layer 7.

[0094] 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.

[0095] 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.

[0096] 3, a fusion process for melt-bonding the resin film for terminal 16 and the metal terminal 14 according to this embodiment will be described. In the fusion process, the resin film for terminal 16 and the metal terminal 14 are thermally fused together while simultaneously melting the A layer 1 by heating and bonding the A layer 1 to the metal terminal 14 by applying pressure.

[0097] In the fusion treatment, from the viewpoint of obtaining sufficient adhesion and sealing properties between the resin film for terminal 16 and the metal terminal 14, it is preferable to heat to a temperature equal to or higher than the melting point of the resin constituting the A layer 1.

[0098] 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.

[0099] 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]

[0100] 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.

[0101] [Materials used] The materials used in the examples and comparative examples are listed in Table 1. In Table 1, PP refers to polypropylene, acid-modified refers to maleic anhydride-modified, and melting point refers to the melting point of the resin used in each layer. The melting point is a value measured in accordance with ASTM D2117. When multiple melting peaks are present, the melting point refers to the temperature at the peak with the greatest heat of dissolution. The tensile modulus and tensile yield stress were measured using a resin film for terminals in accordance with JIS K7162 (test piece: 5B type test piece specified in JIS K7162, tensile speed: 50 mm / min). The density was measured in accordance with ISO 1183. The MFR was measured using a melt flow rate tester (manufactured by Toyo Seiki Seisakusho, Ltd., measurement temperature: 230°C) in accordance with JIS K7210. Note that in Table 1, B1-1 to B1-10 are sometimes collectively referred to as "B1." B2-1 to B2-10 are sometimes collectively referred to as "B2."

[0102] [Table 1]

[0103] [Production of resin film for terminals] Using the materials shown in Tables 2 to 5, layers having the thicknesses shown in the tables were laminated in the order shown in the tables to prepare resin films for terminals. The specific preparation method is as follows. In Tables 2 to 5, layers that do not satisfy the requirements of Layer A, Layer B, or Layer C of the present disclosure in terms of the presence or absence of acid modification or melting point are also classified as Layer A, Layer B, or Layer C for the sake of comparison. In each example and comparative example, the upper row indicates the constituent materials, and the lower row indicates the thickness of each layer. For Layer B, when the constituent materials include a first polyolefin resin and a second polyolefin resin, the mass contents of the first polyolefin resin and the second polyolefin resin are also listed in parentheses below the upper row.

[0104] (Examples 1 to 23) The five layers, A / B / C / B / A, were co-extruded and laminated by the inflation method to obtain a resin film for terminals with a five-layer structure of A / B / C / B / A, at an extrusion temperature of 220°C.

[0105] (Comparative Example 1) A resin film for terminals having a five-layer structure of layer A / layer B / layer C / layer B / layer A was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, layer B was changed to a layer consisting only of B1-1.

[0106] (Comparative Example 2) A resin film for terminals having a three-layer structure of A layer / B layer / A layer was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, the three layers of B layer / C layer / B layer were changed to a single layer consisting of B1-1.

[0107] (Comparative Example 3) A resin film for terminals having a three-layer structure of A layer / B layer / A layer was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, the three layers of B layer / C layer / B layer were changed to a single layer consisting of B2-1.

[0108] Comparative Example 4 A resin film for terminals having a five-layer structure of A layer / B layer / C layer / B layer / A layer was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, Layer A was changed to a layer consisting of A6.

[0109] (Comparative Example 5) A resin film for terminals having a five-layer structure of Layer A / Layer B / Layer C / Layer B / Layer A was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, Layer A was changed to a layer consisting of A7.

[0110] (Comparative Example 6) When co-extrusion was performed by the inflation method, a resin film for terminals having a five-layer structure of A layer / B layer / C layer / B layer / A layer was obtained in the same manner as in Example 1, except that B1-1 in B layer was changed to B1-10.

[0111] (Comparative Example 7) A resin film for terminals having a five-layer structure of A layer / B layer / C layer / B layer / A layer was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, B2-1 in one of the two B layers was changed to B1-10, and B2-1 in the other B layer was changed to B2-2.

[0112] (Comparative Example 8) A resin film for terminals having a five-layer structure of A layer / B layer / C layer / B layer / A layer was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, the C layer was changed from B2-1 to B1-5.

[0113] (Comparative Example 9) A resin film for terminals having a five-layer structure of A layer / B layer / C layer / B layer / A layer was obtained in the same manner as in Example 1, except that when co-extrusion was performed by the inflation method, the C layer was changed from B2-1 to B2-10.

[0114] [Adhesion to aluminum foil at room temperature after contact with electrolyte] A sample of a resin film for terminals, cut to a size of 50 mm (TD) × 100 mm (MD), was folded in half so that a 50 mm × 50 mm piece of chemically treated aluminum foil was sandwiched between the two. The edge opposite the fold was heat-sealed at 185°C / 0.6 MPa / 10 seconds across a 10 mm width. A 15 mm-wide sample was then cut out from the longitudinal center of the heat-sealed portion (see Figure 5) to prepare a sample for heat-seal strength measurement. In this evaluation, laminate 100 in Figure 5 is a laminate consisting of a resin film for terminals / aluminum foil / resin film for terminals. This sample was immersed in an electrolyte solution and aged for one week at 85°C. The electrolyte solution used was a mixture of ethylene carbonate / diethyl carbonate / dimethyl carbonate (1 / 1 / 1 by mass) with LiPF6 adjusted to a concentration of 1M. Thereafter, a T-peel test was performed between the aluminum foil and the resin film for terminal using a tensile tester (manufactured by Shimadzu Corporation) at room temperature (25°C) and a tensile speed of 50 mm / min. From the obtained results, the heat seal strength (burst strength) to the aluminum foil (AL foil) was evaluated based on the following evaluation criteria. This evaluation result was used as an index of the adhesion of the resin film for terminal to the terminal in a room temperature environment after contact with the electrolyte. A rating of A, B, or C indicates pass, and D indicates fail. The results are shown in Tables 2 to 5. A: Heat seal strength is 30N / 15mm or more B: Heat seal strength is 20N / 15mm or more and less than 30N / 15mm C: Heat seal strength is 15N / 15mm or more and less than 20N / 15mm D: Heat seal strength is less than 15N / 15mm

[0115] [Adhesion to aluminum foil in a high-temperature environment after contact with electrolyte] A sample of a resin film for terminals, cut to a size of 50 mm (TD) × 100 mm (MD), was folded in half so that a 50 mm × 50 mm piece of chemically treated aluminum foil was sandwiched between the two. The edge opposite the fold was heat-sealed over a 10 mm width at 185 / 0.6 MPa for 10 seconds. A 15 mm-wide sample was then cut out from the longitudinal center of the heat-sealed portion (see Figure 5) to prepare a sample for heat-seal strength measurement. In this evaluation, laminate 100 in Figure 5 is a laminate consisting of a resin film for terminals / aluminum foil / resin film for terminals. This sample was immersed in an electrolyte solution and aged for one week at 85°C. The electrolyte solution used was a mixture of ethylene carbonate / diethyl carbonate / dimethyl carbonate (1 / 1 / 1 by mass) with LiPF6 adjusted to a concentration of 1M. Thereafter, a T-peel test was performed between the aluminum foil and the resin film for terminal using a tensile tester (manufactured by Shimadzu Corporation) under conditions of an 80°C environment and a tensile speed of 50 mm / min. From the obtained results, the heat seal strength (burst strength) to the aluminum foil (AL foil) was evaluated based on the following evaluation criteria. This evaluation result was used as an index of the adhesion of the resin film for terminal to the terminal in a high-temperature environment after contact with the electrolyte. A rating of A, B, or C was considered pass, and D was considered fail. The results are shown in Tables 2 to 5. A: Heat seal strength is 15N / 15mm or more B: Heat seal strength is 12.5N / 15mm or more and less than 15N / 15mm C: Heat seal strength is 7N / 15mm or more and less than 12.5N / 15mm D: Heat seal strength is less than 7N / 15mm

[0116] [Table 2]

[0117] [Table 3]

[0118] [Table 4]

[0119] [Table 5] [Explanation of symbols]

[0120] 1,7...Layer A, 2,6...Layer B, 4...Layer C, 8...Laminated structure, 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...Resin film for terminal, 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.

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, the resin film for terminal has a laminated structure with the following layer A, which is an outermost layer arranged on the metal terminal side, The resin film for a terminal, wherein the laminated structure is formed by laminating the following layer B, the following layer C, and the following layer B in this order: Layer A: A layer formed using a resin composition made of an acid-modified polyolefin resin having a tensile modulus of elasticity of 620 MPa or more and 645 MPa or less. Layer B: A layer formed using a resin composition consisting of a first polyolefin resin having a tensile modulus of 550 MPa or more and less than 1000 MPa and a tensile yield stress of 18 MPa or more and 20 MPa or less, and a second polyolefin resin having a tensile modulus of 1000 MPa or more and less than 1500 MPa and a tensile yield stress of 23 MPa or more and 29 MPa or less. Layer C: A layer formed using a resin composition made of a polyolefin resin having a melting point of 160°C or higher and 170°C or lower.

2. 2. The resin film for terminals according to claim 1, wherein in the layer B, the mass ratio of the first polyolefin resin to the second polyolefin resin is 0.1 to 9.

3. In the layer B, the first polyolefin resin has a density of 885 kg / m or more and less than 895 kg / m, The resin film for a terminal according to claim 1 or 2, wherein the second polyolefin resin has a density of 895 kg / m 3 or more and 910 kg / m 3 or less.

4. In the layer B, the first polyolefin resin has an MFR at 230°C of 1.0 to 10.0 g / 10 min, The resin film for a terminal according to any one of claims 1 to 3, wherein the MFR of the second polyolefin resin is 0.05 g / 10 min or more and less than 1.0 g / 10 min.

5. A resin film for terminals described in any one of claims 1 to 4, which is formed by laminating the A layer, which is the outermost layer arranged on the metal terminal side, the laminated structure, and the A layer in this order.

6. The resin film for a terminal according to any one of claims 1 to 5, having a thickness of 160 µm or more.

7. 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; 7. 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.

Images