Resin film for terminal, and power storage device using the same

Abstract

To provide a resin film for a terminal which can improve adhesion to an exterior material under high temperature condition, a strength at break and an elongation at break in a well-balanced manner, even when it is made thick.SOLUTION: A resin film for a terminal has 7 or more layers, in which at least the 7 layers correspond to at least one layer selected from the group consisting of the following layer A, layer B, layer C and layer D, and has a structure such that layer A / layer B / layer A / layer C or layer D / layer A / layer B / layer A are laminated in this order. Layer A: layer which is formed using a resin composition containing an acid-modified polyolefin resin and has an MFR of 2.0-50 g / 10 min. Layer B: layer which is formed using a resin composition containing a polyolefin resin and has an MFR of 0.05 g / 10 min or more and less than 2.0 g / 10 min. Layer C: layer which is formed using a resin composition containing a non-modified polyolefin resin and has an MFR of 0.05-50 g / 10 min. Layer D: adhesive layer containing a resin having a crosslinking structure.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 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] In recent years, metal terminals have become thicker due to the increasing capacity of batteries, and this has led to a trend toward thicker terminal resin films. However, if conventional thin terminal resin films are simply made thicker, their adhesion to the exterior material tends to decrease under high-temperature conditions, which can easily lead to peeling. Furthermore, if an attempt is made to maintain adhesion, the strength of the terminal resin film tends to decrease.

[0007] The present disclosure has been made in consideration of the problems associated with the above-described conventional technologies, and aims to provide a terminal resin film that, even when thickened, can achieve a balanced improvement in adhesion to exterior materials under high temperature conditions, as well as breaking strength and breaking elongation, compared to when a conventional terminal resin film is simply 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 seven or more layers, at least seven of which correspond to at least one layer selected from the group consisting of Layer A, Layer B, Layer C, and Layer D below, and at least a portion of the resin film for a terminal has a structure in which Layer A / Layer B / Layer A / Layer C or Layer D / Layer A / Layer B / Layer A are laminated in this order. Layer A: A layer formed using a resin composition containing an acid-modified polyolefin resin, and having a melt flow rate at 230°C of 2.0 to 50 g / 10 min. Layer B: A layer formed using a resin composition containing a polyolefin resin, having a melt flow rate at 230°C of 0.05 g / 10 min or more and less than 2.0 g / 10 min. Layer C: A layer formed using a resin composition containing an unmodified polyolefin resin, and having a melt flow rate at 230°C of 0.05 to 50 g / 10 min. Layer D: An adhesive layer containing a resin having a crosslinked structure.

[0009] According to the above-mentioned resin film for terminals, by satisfying the above-mentioned conditions regarding the layer structure, melt flow rate (MFR), whether or not acid modification is performed, and the structure of the adhesive layer, even when the film is made thick, it is possible to improve the adhesion to the packaging material under high temperature conditions, as well as the breaking strength and breaking elongation in a well-balanced manner, compared to when a conventional resin film for terminals is simply made thick. According to the above-mentioned resin film for terminals, by having a multilayer structure including the above-mentioned specific seven layers, it is possible to appropriately distribute stress even when the film is made thick, and it is possible to improve the breaking strength and breaking elongation while maintaining adhesion.

[0010] In the above-mentioned resin film for terminals, the melting point of the acid-modified polyolefin resin used in the A layer may be 100°C or higher and lower than 160°C, the melting point of the polyolefin resin used in the B layer may be 130 to 175°C, and the melting point of the unmodified polyolefin resin used in the C layer may be 160 to 175°C.

[0011] In the resin film for a terminal, the unmodified polyolefin resin used in the C layer may have a melting point equal to or higher than the melting point of the polyolefin resin used in the B layer.

[0012] All of the layers constituting the resin film for a terminal may correspond to at least one layer selected from the group consisting of the A layer, the B layer, and the C layer.

[0013] All of the layers constituting the resin film for a terminal may correspond to at least one layer selected from the group consisting of the A layer, the B layer, and the D layer.

[0014] In the above-mentioned resin film for terminals, the D layer may be a layer formed using an adhesive composition containing an acid-modified polyolefin resin and at least one curing agent selected from the group consisting of a polyfunctional isocyanate compound, a glycidyl compound, a compound having a carboxy group, and a compound having an oxazoline group.

[0015] Of the layers constituting the resin film for a terminal, the total thickness of the layers corresponding to the A layer may be equal to or greater than the total thickness of the layers corresponding to the B layer.

[0016] The resin film for terminal may have a total thickness of 160 μm or more.

[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 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. [Effects of the Invention]

[0018] According to the present disclosure, it is possible to provide a resin film for terminals that can improve adhesion to exterior materials under high temperature conditions, as well as breaking strength and breaking elongation in a balanced manner, even when the film is thickened, compared to when a conventional resin film for terminals is simply thickened, and an energy 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-resistant heat seal strength to packaging materials 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 a portion of the outer peripheral surface of the metal terminal 14. The terminal resin film 16 has seven or more layers, and at least seven of the layers constituting the terminal resin film 16 correspond to at least one layer selected from the group consisting of Layer A, Layer B, Layer C, and Layer D below, and at least a portion of the terminal resin film 16 has a structure in which layers are laminated in the order of Layer A / Layer B / Layer A / Layer C or Layer D / Layer A / Layer B / Layer A. Layer A: A layer formed using a resin composition containing an acid-modified polyolefin resin, and having a melt flow rate at 230°C of 2.0 to 50 g / 10 min. Layer B: A layer formed using a resin composition containing a polyolefin resin, having a melt flow rate at 230°C of 0.05 g / 10 min or more and less than 2.0 g / 10 min. Layer C: A layer formed using a resin composition containing an unmodified polyolefin resin, and having a melt flow rate at 230°C of 0.05 to 50 g / 10 min. Layer D: An adhesive layer containing a resin having a crosslinked structure.

[0041] The melt flow rates (MFR) of the A, B, and C layers can be measured using a melt flow rate measuring device at a measurement temperature of 230° C. The MFR of the A, B, and C layers can be controlled to fall within a predetermined range by adjusting the type and molecular weight of the resin, additives, etc.

[0042] Fig. 4 is a schematic cross-sectional view showing one embodiment of a resin film for a terminal according to the present embodiment. The resin film for a terminal 16 shown in Fig. 4 has a structure in which each layer is laminated in the order of A Layer 1 / B Layer 2 / A Layer 3 / C Layer or D Layer 4 / A Layer 5 / B Layer 6 / A Layer 7. The resin film for a terminal 16 shown in Fig. 4 has a structure in which a three-layer film 8 consisting of A Layer 1 / B Layer 2 / A Layer 3 and a three-layer film 9 consisting of A Layer 5 / B Layer 6 / A Layer 7 are laminated via C Layer or D Layer 4. Each layer will be described below.

[0043] Layer A is formed using a resin composition containing an acid-modified polyolefin resin. Examples of acid-modified polyolefin resins include resins obtained by graft-modifying polyolefin resins with maleic anhydride, carboxylic acid, sulfonic acid, and derivatives thereof. Acid-modified polyolefin resins that are 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 seal strength and processability. These polyolefin resins may be used alone or in combination of two or more. The resin composition used to form Layer A may or may not contain resins other than the acid-modified polyolefin resin.

[0044] The degree of modification with acid of the polyolefin resin (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 preferably 100°C or higher and lower than 160°C, more preferably 110 to 150°C, and even more preferably 120 to 140°C. When the acid-modified polyolefin resin has a melting point of 100°C or higher, adhesion to packaging materials under high-temperature conditions can be further improved. Furthermore, when the acid-modified polyolefin resin has a melting point of lower than 160°C, the resin melts easily during heat sealing, and heat seal strength can be further improved.

[0046] 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.

[0047] 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.

[0048] Examples of color pigments include carbon black, quinacridone pigments, polyazo pigments, and isoindolinone pigments.

[0049] 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.

[0050] 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 the thickness of Layer A is 10 μm or more, the adhesion between the exterior packaging material and the resin film for terminals under high temperature conditions can be further improved. Furthermore, from the viewpoint of processability and the breaking strength of the film, the thickness of Layer A is preferably 150 μm or less.

[0051] 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.

[0052] Layer B is formed using a resin composition containing a polyolefin resin. Examples of the 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 layer B may be an acid-modified polyolefin resin or an unmodified polyolefin resin, but from the viewpoint of insulating properties, an unmodified polyolefin resin is preferred. These polyolefin resins may be used alone or in combination of two or more. The resin composition used to form layer B may or may not contain other resins besides the polyolefin resin.

[0053] The melting point of the polyolefin resin used in Layer B is preferably 130 to 175°C, more preferably 150 to 170°C, and even more preferably 160 to 168°C. When the polyolefin resin has a melting point of 130°C or higher, adhesion to packaging materials under high-temperature conditions can be further improved. When the polyolefin resin has a melting point of 175°C or lower, the resin melts easily during heat sealing, further improving heat seal strength. Note that a blend of multiple resins with different melting points may also be used, for example, a blend of a resin with a melting point of 130°C and a resin with a melting point of 160°C.

[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 under high temperature conditions 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] The MFR of Layer B at 230°C is 0.05 g / 10 min or more and less than 2.0 g / 10 min, preferably 0.1 to 1.5 g / 10 min, and more preferably 0.5 to 1.0 g / 10 min. When Layer B 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 B has an MFR of less than 2.0 g / 10 min, the breaking strength of the resin film for terminals can be improved.

[0057] The C layer is formed using a resin composition containing an unmodified 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 unmodified polyolefin resin preferably contains polypropylene from the viewpoints of heat seal strength and processability. These unmodified polyolefin resins may be used alone or in combination of two or more. The resin composition used to form the C layer may or may not contain any resin other than the unmodified polyolefin resin. The resin composition used to form the C layer preferably contains only unmodified polyolefin resin as the polyolefin resin and does not contain acid-modified polyolefin resin from the viewpoint of adhesion between the exterior material and the terminal resin film under high-temperature conditions.

[0058] The melting point of the unmodified polyolefin resin used in Layer C is preferably 160 to 175°C, more preferably 160 to 170°C, and even more preferably 162 to 168°C. When the melting point of the unmodified polyolefin resin is 160°C or higher, adhesion to packaging materials under high-temperature conditions can be further improved. Furthermore, when the melting point of the polyolefin resin is 175°C or lower, the resin melts easily during heat sealing, and heat seal strength can be further improved.

[0059] The melting point of the unmodified polyolefin resin used in the C layer is Tm C (℃), the melting point of the polyolefin resin used in layer B is Tm B (℃), Tm C ≧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, the decrease in heat seal strength under high temperature conditions can be further suppressed. C -Tm B When the value is 25 (° C.) or less, the processability of the resin film for terminals can be improved.

[0060] 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.

[0061] 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 the thickness of Layer C is 2 μm or more, the adhesion between the packaging material and the resin film for terminals under high temperature conditions can be improved. Furthermore, from the viewpoint of processability and the breaking elongation of the film, the thickness of Layer C is preferably 150 μm or less.

[0062] The MFR of Layer C at 230°C is 0.05 to 50 g / 10 min, preferably 1.0 to 25 g / 10 min, and 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.

[0063] Layer D is an adhesive layer containing a resin having a crosslinked structure. Examples of resins having a crosslinked structure include crosslinked acrylic resins, epoxy resins, phenolic resins, urea resins, melamine resins, polyurethane resins, and acid-modified polyolefin resins crosslinked with isocyanate or epoxy. Among these, the resin having a crosslinked structure preferably contains a crosslinked acid-modified polyolefin resin. From the viewpoint of adhesion between sealant layers, Layer D is preferably a layer formed using an adhesive composition containing an acid-modified polyolefin resin and at least one curing agent selected from the group consisting of a polyfunctional isocyanate compound, a glycidyl compound, a compound having a carboxy group, and a compound having an oxazoline group. The resin having a crosslinked structure may be used alone or in combination of two or more.

[0064] The thickness of the D layer is preferably 1 to 10 μm, more preferably 2 to 5 μm, from the viewpoint of the heat seal strength of the resin film for a terminal.

[0065] The total thickness of the resin film for terminals is preferably 150 μm or more, more preferably 160 μm or more, and even more preferably 200 μm or more. When the total thickness of the resin film for terminals is increased so that it falls within the above range, adhesion to the packaging material under high temperature conditions tends to decrease. However, the resin film for terminals of this embodiment can improve adhesion to the packaging material under high temperature conditions, as well as breaking strength and breaking elongation in a well-balanced manner. The upper limit of the total thickness of the resin film for terminals is not particularly limited, but may be, for example, 1000 μm or less.

[0066] 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.

[0067] It is preferable that the total thickness of the A layer is 75% or less, the total thickness of the B layer is 60% or less, the total thickness of the C layer is 60% or less, and the total thickness of the D layer is 10% or less of the total thickness of the resin film for terminal. By satisfying these conditions, it is possible to improve the adhesion to the exterior material under high temperature conditions, and the breaking strength and breaking elongation in a well-balanced manner.

[0068] In the resin film for a terminal of this embodiment, Layer B may or may not additionally satisfy the conditions of Layer C. Furthermore, Layer C may or may not additionally satisfy the conditions of Layer B.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] In the resin film for terminal of this embodiment, when a plurality of D layers are present, the plurality of D layers may be layers formed using the same adhesive composition or layers formed using different adhesive compositions. Furthermore, the thicknesses of the plurality of D layers may be the same or different. From the viewpoints of processability and curl suppression of the resin film for terminal, it is preferable that the above-mentioned configurations of the plurality of D layers are all the same.

[0073] When the resin film for a terminal of this embodiment has a laminated structure of Layer A / Layer B / Layer A / Layer C / Layer A / Layer B / Layer A, the layers may be the same thickness or different thicknesses. The thickness ratio of the layers in the laminated structure may be, for example, 1:2:1:1:1:2:1, 4:2:2:1:2:2:4, 5:3:2:1:2:3:5, 5:10:5:1:5:10:5, etc. It is preferable that Layer C be thinner than Layer A and Layer B.

[0074] The resin film for a terminal of this embodiment may include layers other than layer A, layer B, layer C, and layer D (layers that do not fall under any of layer A, layer B, layer C, and layer D), but preferably does not include any other layers. That is, 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, layer C, and layer D. Also, all of the layers constituting the resin film for a terminal may fall under at least one layer selected from the group consisting of layer A, layer B, and layer C, or may fall under at least one layer selected from the group consisting of layer A, layer B, and layer D. Also, the resin film for a terminal may include all of layer A, layer B, layer C, and layer D.

[0075] 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.

[0076] 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.

[0077] For example, Figure 4 shows a seven-layered resin film for terminals in which a three-layer film 8 and a three-layer film 9 are laminated via a C layer or a D layer 4, but the seven-layered resin film for terminals may also be laminated with a further three-layer film 8 via a C layer or a D layer 4 to form an 11-layered resin film for terminals.

[0078] [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.

[0079] When the resin film for terminal 16 has a seven-layer structure of A layer / B layer / A layer / C layer / A layer / B layer / A layer, the seven 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 / A layer may be formed in advance, and then two three-layer films may be laminated by sandwich lamination using the resin composition that constitutes Layer C.

[0080] Furthermore, when the terminal resin film 16 has a seven-layer structure of A layer / B layer / A layer / D layer / A layer / B layer / A layer, a three-layer film consisting of A layer / B layer / A layer may be formed in advance, and then two three-layer films may be laminated by dry lamination using an adhesive composition constituting Layer D. Alternatively, a three-layer film consisting of A layer / B layer / A layer may be formed in advance, and then the three-layer film may be attached to a three-layer film in which A layer / B layer / A layer and Layer D have been formed in advance by Neelam lamination.

[0081] 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.

[0082] Even when the resin film for terminal 16 has eight or more layers, it can be produced by appropriately using the above-mentioned production method.

[0083] As an example of a method for manufacturing the terminal resin film 16, a method will be described in which a three-layer film is first formed by an inflation method, and then two three-layer films are laminated using the resin composition that constitutes layer C or the adhesive composition that constitutes layer D.

[0084] First, base materials for layers A, B, and A are prepared. Next, the base materials for layers A, B, and A are fed into 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 layers A, B, and A are laminated), while air is supplied from inside the extruded three-layer laminate.

[0085] The cylindrically inflated three-layer film is then conveyed and flattened by a guide, after which the three-layer film is folded into a sheet by a pair of pinch rolls. Both ends of the woven tube are slit, and the pair of films (two strips) are wound into a roll around a winding core, producing a roll of three-layer film.

[0086] 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 three-layer film.

[0087] 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 three-layer film can be adjusted by changing the rotation speed of each screw.

[0088] Next, two of the obtained three-layer films are prepared and laminated together by sandwich lamination using the resin composition constituting layer C, or by dry lamination using the adhesive composition constituting layer D.

[0089] When laminating using the sandwich lamination method, a molten resin composition is extruded onto one three-layer film, and then the other three-layer film is supplied on top of it and laminated together to obtain a seven-layer resin film for terminals.

[0090] When laminating by dry lamination, an adhesive composition is applied to one three-layer film, dried, and then the other three-layer film is placed on top and thermocompressed to obtain a seven-layer resin film for terminals. Drying can be performed at 80 to 140°C for 30 seconds to 5 minutes. After lamination, aging can be performed at 30 to 80°C for 24 to 240 hours.

[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 terminal resin film 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 shown 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. MFR is the melt flow rate of each layer formed using each material, measured in accordance with JIS K7210 using a melt flow rate meter (manufactured by Toyo Seiki Seisaku-sho, measurement temperature: 230°C). In this example, layers that do not satisfy the requirements of layer A, layer B, layer C, or layer D of the present disclosure in terms of whether or not they are acid-modified, whether or not they have a crosslinked structure, or MFR, are also conveniently classified as layer A, layer B, layer C, or layer D for comparison purposes.

[0102] [Table 1]

[0103] [Production of resin film for terminals] Resin films for terminals were produced by laminating layers of the thicknesses shown in Tables 2 and 3 in the order shown in the tables using the materials shown in Tables 2 and 3. The specific production method is as follows.

[0104] (Examples 1 to 6, Comparative Examples 1 and 2) Two three-layer films were produced by laminating three layers of A / B / A using the inflation method. The two three-layer films were then laminated using the sandwich lamination method with the material of Layer C to obtain a seven-layer resin film for terminals with a layer A / B / A / C / A / B / A structure.

[0105] (Examples 7 to 14, Comparative Examples 3 to 8) Two three-layer films were produced by laminating three layers of A / B / A using the inflation method. The two three-layer films were then laminated using the dry lamination method with the material of Layer D to obtain a seven-layer resin film for terminals with a Layer A / B / A / D / A / B / A structure.

[0106] Example 15 Three three-layer films were produced by laminating three layers of A / B / A using the inflation method. The three three-layer films were then laminated using the sandwich lamination method with the material of Layer C to obtain a resin film for terminals with an 11-layer structure of A / B / A / C / A / B / A / C / A / B / A.

[0107] Example 16 Three three-layer films were produced by laminating three layers of A / B / A using the inflation method. The three three-layer films were then laminated using the dry lamination method with the material of Layer D to obtain a resin film for terminals with an 11-layer structure of A / B / A / D / A / B / A / D / A / B / A / A.

[0108] Example 17 Three three-layer films were produced by laminating three layers of A / B / A using the inflation method. Two of the three-layer films were laminated using the sandwich lamination method with the material for Layer C to produce a seven-layer film. Next, the seven-layer film and the three-layer film were laminated using the material for Layer D using the dry lamination method to obtain a resin film for terminals with an 11-layer structure: A / B / A / D / A / B / A / C / A / B / A (on the exterior material side) and (on the tab lead side).

[0109] (Comparative Example 9) Five layers of A layer / B layer / A layer / B layer / A layer were laminated by an inflation method to obtain a resin film for terminals with a five-layer structure.

[0110] (Comparative Examples 10 to 11) Two two-layer films were produced by laminating two layers, A and B, using the inflation method. The two two-layer films were then laminated using the sandwich lamination method with the material for layer C, with the B layers facing each other, to obtain a five-layer resin film for terminals with a layer A / layer B / layer C / layer B / layer A structure.

[0111] (Comparative Examples 12 to 13) Three layers of A layer / B layer / A layer were laminated by the inflation method to obtain a resin film for terminals with a three-layer structure.

[0112] (Comparative Examples 14 to 15) Two two-layer films were produced by laminating two layers, A and B, using the inflation method. The two two-layer films were then laminated using the dry lamination method with the material for layer D, with the B layers facing each other, to obtain a five-layer resin film for terminals with a layer A / layer B / layer D / layer B / layer A structure.

[0113] [Heat seal strength against exterior materials] A sample of the terminal resin film, 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 at 165°C / 0.6 MPa / 10 seconds over a 10 mm width. The sample was then folded in half so that the sealant layer of the exterior material, which had a laminated structure of nylon film (25 μm thick), adhesive, aluminum foil (40 μm thick), and a polypropylene sealant layer (80 μm thick), was in contact with the terminal resin film. The edge opposite the folded portion (the same area where the terminal resin film and aluminum foil were heat-sealed) was heat-sealed at 190°C / 0.5 MPa / 5 seconds over a 10 mm width. A 15 mm wide sample was then cut from the center of the heat-sealed portion (see Figure 5) to prepare a sample for heat-seal strength measurement. In this evaluation, laminate 100 in FIG. 5 is a laminate consisting of exterior material / resin film for terminal / aluminum foil / resin film for terminal / exterior material. A T-peel test was performed between the exterior material and the resin film for terminal on the heat-sealed portion of this sample using a tensile tester (manufactured by Shimadzu Corporation) in an environment of 60°C and at a tensile speed of 50 mm / min. From the obtained results, the heat-resistant heat seal strength (burst strength) to the exterior material was evaluated based on the following evaluation criteria. A rating of A, B, or C was considered pass, and D was considered fail. The results are shown in Tables 2 and 3. A: Heat seal strength is 50N / 15mm or more B: Heat seal strength is 40N / 15mm or more and less than 50N / 15mm C: Heat seal strength is 30N / 15mm or more and less than 40N / 15mm D: Heat seal strength is less than 30N / 15mm

[0114] [Breaking strength and breaking elongation] The resin film for terminals was subjected to a tensile test in accordance with JIS K6251 (specimen shape: dumbbell No. 5 (width 6 mm) as specified in JIS K6251, gauge length: 25 mm, chuck distance: 50 mm, tensile speed: 100 mm / min) to measure the breaking strength and breaking elongation in the MD direction. A tensile tester (manufactured by Shimadzu Corporation) was used for the tensile test. The breaking elongation was calculated using the following formula. Breaking elongation (%) = {(gauge line distance at break (mm) - 25 (mm)) / 25 (mm)} x 100 The breaking strength and breaking elongation were evaluated based on the obtained results according to the following evaluation criteria. A rating of A, B, or C indicates passing, and D indicates failing. The results are shown in Tables 2 and 3. (breaking strength) A:45MPa or more B: 40 MPa or more, less than 45 MPa C: 35 MPa or more, less than 40 MPa D: Less than 35 MPa (breaking elongation) A: Over 600% B: 550% or more, less than 600% C: 500% or more, less than 550% D: Less than 500%

[0115] [Table 2]

[0116] [Table 3] [Explanation of symbols]

[0117] 1, 3, 5, 7...Layer A, 2, 6...Layer B, 4...Layer C or D, 8, 9...3-layer film, 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

[Claim 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 seven or more layers, At least seven layers among the layers constituting the resin film for terminal correspond to at least one layer selected from the group consisting of the following layer A, layer B, layer C, and layer D, At least a part of the resin film for a terminal has a structure in which layers A, B, A and C or D, A, B and A are laminated in this order. Layer A: A layer formed using a resin composition containing an acid-modified polyolefin resin, having a melt flow rate at 230°C of 2.0 to 50 g / 10 min. Layer B: A layer formed using a resin composition containing a polyolefin resin, having a melt flow rate at 230°C of 0.05 g / 10 min or more and less than 2.0 g / 10 min. Layer C: A layer formed using a resin composition containing an unmodified polyolefin resin, having a melt flow rate at 230° C. of 0.05 to 50 g / 10 min. Layer D: An adhesive layer containing a resin having a crosslinked structure.

Images