JP5516692B2 - Flat type electrochemical cell metal terminal sealing adhesive sheet - Google Patents

Description

  The present invention relates to a packaging material for packaging a flat electrochemical cell body containing an electrolyte (liquid or solid electrolyte), represented by a battery or a capacitor, and more specifically, a packaging body for packaging a flat electrochemical cell body. And between the positive electrode and the negative electrode of the flat electrochemical cell main body and a metal terminal protruding from the package body, the package body, the metal terminal, and the package body The present invention relates to an adhesive sheet for sealing a flat electrochemical cell metal terminal part.

  One of the flat electrochemical cells is a lithium battery. A lithium battery is also called a lithium secondary battery, which is made of a solid polymer, a gel polymer, a liquid, etc. as an electrolyte, and generates electricity by the movement of lithium ions. Is included. The configuration of the lithium secondary battery is as follows: positive electrode current collector (aluminum) / positive electrode active material layer (polymeric positive electrode material such as metal oxide, carbon black, metal sulfide, electrolyte, polyacrylonitrile) / electrolyte (propylene carbonate, ethylene Carbonate electrolyte such as carbonate, dimethyl carbonate, ethylmethyl carbonate, inorganic solid electrolyte composed of lithium salt, gel electrolyte) / negative electrode active substance layer (lithium metal, alloy, carbon, electrolyte, polyacrylonitrile, etc. polymer negative electrode material ) / A lithium battery main body made of a negative electrode current collector (copper) and a packaging body for packaging them. Lithium secondary batteries are used for personal computers, portable terminals (cell phones, PDAs, etc.), video cameras, electric vehicles, energy storage batteries, robots, satellites, and the like. In the present specification, the positive electrode current collector and the positive electrode active material layer are referred to as a positive electrode, and the negative electrode current collector and the negative electrode active material layer are referred to as a negative electrode.

  As the package of the lithium battery, a metal can formed by pressing a metal into a cylindrical or rectangular parallelepiped container, or a laminate in which a metal foil such as a plastic film or aluminum is laminated is processed into a bag shape or the like. A bag body (hereinafter referred to as a packaging body) or the like is used.

  By the way, since the package made of a metal can is rigid, and the shape of the battery itself is thereby determined, for example, when this is used for a mobile phone, the size of the mobile phone body is determined by the shape of the battery, There is a problem that the shape of the mobile phone cannot be freely designed. Therefore, the packaging body tends to be used because the shape of the mobile phone body can be freely designed to some extent in order to have flexibility. Furthermore, the reason why the package tends to be used is that, when the battery is used at a high temperature and the internal pressure is abnormally increased, the package made of a metal can is packaged until explosion or ignition occurs. There is a problem that it is dangerous to endure. On the other hand, the package sealed by the heat bonding part functions as a safety valve that releases the internal pressure by peeling off the heat bonding part, but the function as a battery is lost, but the package is made of a metal can. This is because the risk of explosion and ignition can be reduced compared to.

As the package, in view of necessary physical properties, workability, economy, etc. as a lithium battery, as shown in FIG. 2, at least a base layer A1, a barrier layer A2 made of a metal foil such as aluminum, a thermal adhesive resin layer A laminate A in which A3 is laminated is used. And this laminated body A is made into a bag shape as shown in FIG. 3 (a) (in FIG. 3 (a), it is a pillow type packaging bag, but it may be a packaging bag of a three-way type, a four-way type, etc.). The lithium battery main body and the metal terminal 31 connected to each of the positive electrode and the negative electrode of the lithium battery main body are processed and housed in a state of protruding outward, and the opening is thermally bonded and sealed, or the laminate A As shown in FIG. 4 (a), a concave portion is formed by press molding so that the thermal adhesive resin layer is located inside, and the lithium battery body and the positive and negative electrodes thereof are connected to the concave portion. The metal terminal 31 is stored in a state of protruding outward, and the concave portion is formed so that the thermally adhesive resin layer of the sheet-like laminate A (not shown) prepared separately is located on the concave side. And thermally bond the periphery By sealing, FIG. 3 (b), the or is used as a lithium battery 10 shown in Figure 4 (b). Reference sign S indicates a thermal bonding portion.

  The thermal adhesive resin layer A3 constituting the package (the laminated body A) is projected from the lithium battery main body to the outside of the package together with the thermal adhesiveness between the thermal adhesive resin layers A3. An acid-modified polyolefin resin that requires thermal adhesion to the metal terminal 31 and is excellent in adhesion to metal, such as polyolefin resin graft-modified with unsaturated carboxylic acid, ethylene or propylene and acrylic acid, or methacrylic acid Copolymers or metal cross-linked polyolefin resins have been used.

  However, when the acid-modified polyolefin-based resin is used for the heat-adhesive resin layer A3 constituting the package (the laminate A), a general polyolefin-based resin (a linear or divided resin composed of carbon and hydrogen) is used. This refers to a branched olefin-based resin, which is referred to as a general polyolefin-based resin, and is less slippery and wrinkles when processed into a bag, or press-molded to form a recess. There is a problem that pinholes and cracks may occur. Therefore, as an alternative, the heat-adhesive resin layer A3 uses a general polyolefin-based resin, and can be thermally bonded to both the general polyolefin-based resin and the metal terminal 31, as described above. A lithium battery metal terminal sealing adhesive sheet (hereinafter sometimes referred to as an adhesive sheet) composed of a single layer of resin or a multilayer formed of at least one surface layer of the resin, the metal terminal and the thermal bonding A method has been adopted in which the resin layer is interposed between the resin layer and thermally sealed to be sealed.

  Specifically, as shown in FIG. 5, a metal terminal 31 [see FIG. 3 (b), FIG. 4 (b)] protrudes from the lithium battery main body 30 before injecting the electrolyte to the outside of the package, For example, the metal terminal part sealing adhesive sheet 1 ′ composed of the acid-modified polyolefin resin single layer described above is fixed to both surfaces of the metal terminal 31 by temporary sealing. Then, the lithium battery main body 30 is housed in the concave portion of the laminate A shown in FIG. 4 (a) formed by press molding, and the laminate A (not shown) prepared separately is used. The three peripheral edges including the peripheral edge including the metal terminal 31 of the lithium battery main body 30 covering the concave portion are thermally bonded, and then an electrolyte is injected from the peripheral edge of one non-adhered part, and then the non-adhered part The lithium battery 10 shown in FIG. 4B is obtained by thermally bonding and sealing.

  By the way, the metal terminal 31 of the lithium battery 10 is thermally bonded in a state where the metal terminal 31 is sandwiched between the packaging body (the laminated body A) at a portion provided with the adhesive sheet 1 ′. At this time, the metal terminal 31 has a thickness of at least about 50 μm and a width of at least about 2.5 mm. In order to fill the gaps on both sides of the metal terminal 31 with the adhesive sheet 1 ′ and the thermal adhesive resin layer A3 of the package (the laminated body A) to ensure a sealed state, it is necessary to perform thermal bonding. Therefore, the adhesive sheet 1 ′ and the thermal adhesive resin layer A3 of the package (the laminated body A) are extruded out of the pressurizing part, so that the pressurizing part is There was a problem of becoming thin. Further, when the metal terminals are cut into small widths on both side ends in general, burrs of several μm to several tens of μm are generated, and this is caused by a metal foil such as aluminum of the package (the laminated body A). There was also a problem that the barrier layer A2 and the metal terminal 31 contacted and short-circuited.

Moreover, in order to improve this problem, as said adhesive sheet 1 'used on both surfaces of the said metal terminal 31, 3 layers which coat | covered both surfaces of the heat resistant resin film with the film which can be heat-sealed to the inner surface film of a battery packaging material. A battery terminal covering material (corresponding to the above-mentioned adhesive sheet for sealing a metal terminal portion) made of a laminated film having a structure has been proposed (see, for example, Patent Document 1). However, when the covering material for battery terminals described in Patent Document 1 is used, the phenomenon of short-circuiting described above is improved as compared with that of an acid-modified polyolefin resin single layer, but a heat-resistant resin film and a battery The interlayer adhesive strength between the film and the heat sealable film on the inner film of the packaging material is not sufficient. For this reason, when the battery element abnormally generates heat, gas is generated inside the battery, and the internal pressure of the battery rises, the heat-resistant resin film and the battery are caused by the stress that separates the battery packaging material and the metal terminal at the metal terminal extraction portion. There is a possibility that the inner film of the packaging material may be peeled off at the interface with the heat-sealable film. Note that the above problem also occurs when a capacitor and an electric double layer capacitor are housed in addition to the lithium battery housing the lithium battery body.

JP 2000-208112 A

  Therefore, the present invention has been made in view of the above-described problem, in which a metal terminal connected to each of a positive electrode and a negative electrode is sandwiched in a state of protruding outward and is thermally bonded to an inner layer sealed by a peripheral heat bonding portion. In a package including at least a polyolefin resin (general polyolefin resin) having a barrier layer made of metal foil and a barrier layer made of metal foil such as aluminum of the package to prevent a short circuit Flat type electrochemical cell metal terminal sealing adhesiveness that can be sealed in a stable state, has high interlayer adhesion strength (hereinafter referred to as laminate strength), and is less likely to degrade battery performance due to moisture ingress. Is to provide a sheet.

  In order to solve the above-described problems, the present invention accommodates an electrochemical element having a positive electrode and a negative electrode by a packaging material having at least an inner layer made of a polyolefin resin having thermal adhesion and a barrier layer made of a metal foil. In addition, the metal terminals connected to the positive electrode and the negative electrode are sandwiched between the inner layer and the metal terminal in the metal terminal extraction portion of the flat electrochemical cell that is sandwiched in a protruding state and sealed with a peripheral thermal bonding portion. An adhesive sheet for sealing a flat electrochemical cell metal terminal part to be interposed, wherein the adhesive sheet for sealing a flat electrochemical cell metal terminal part adheres a fibrous sheet or a porous sheet to the inner layer and the metal terminal An adhesive sheet for sealing a flat electrochemical cell metal terminal portion, which is coated with an acid-modified polyolefin resin layer having

  By comprising in this way, the barrier layer which consists of metal foils, such as aluminum of a package, and the metal terminal can be prevented from short circuit and can be sealed in a stable state, and the interlayer adhesive strength (hereinafter referred to as laminate strength and A flat type electrochemical cell metal terminal sealing adhesive sheet can be obtained. As a result, even when the battery element abnormally generates heat, gas is generated inside the battery, and the internal pressure of the battery rises, due to the stress that peels off the battery packaging material and the metal terminal at the metal terminal extraction part, A flat electrochemical cell having a high level of safety can be provided by preventing the phenomenon that the inner surface film of the battery packaging material is peeled off at the interface with the heat-sealable film.

  In the flat electrochemical cell metal terminal part sealing adhesive sheet having the above-described configuration, the present invention is characterized in that the fibrous sheet is made of natural fibers or synthetic resin chemical fibers having a melting point of 200 ° C. or higher. It is characterized by. By comprising in this way, when pinching and heat-bonding a metal terminal, a short circuit with the barrier layer which consists of metal foils, such as aluminum of a package, and a metal terminal can be prevented suitably.

  In the flat electrochemical cell metal terminal sealing adhesive sheet having the above-described configuration, the present invention is characterized in that the fibrous sheet is mainly composed of wholly aromatic polyester fibers. With this configuration, the wholly aromatic polyester fiber not only has a high melting point due to its molecular skeleton and excellent heat resistance, but also has chemical resistance (particularly electrolyte resistance) and low moisture absorption. It is excellent, and it is possible to prevent a short circuit between the barrier layer made of a metal foil such as aluminum of the package and the metal terminal, and to prevent delamination in the electrolytic solution.

  In the flat electrochemical cell metal terminal sealing adhesive sheet having the above-described configuration, the present invention is characterized in that the wholly aromatic polyester fiber is made of a melt anisotropic wholly aromatic polyester fiber. By constituting in this way, the melt-anisotropic wholly aromatic polyester is an aromatic polyester that exhibits optical anisotropy (liquid crystallinity) in the molten state, and the fiber obtained by spinning this further has optical anisotropy ( As liquid crystallinity advances, not only is it excellent in mechanical strength, heat resistance and chemical resistance (electrolytic solution resistance), but the acid-modified polyolefin resin penetrates into the gaps formed by dividing and subdividing, so the interlayer An adhesive sheet having extremely high strength can be obtained.

  Further, the present invention is the flat electrochemical cell metal terminal sealing adhesive sheet having the above-described configuration, wherein the fibrous sheet made of the wholly aromatic polyester fiber is in an environment of 25 ° C. and 65% RH. The moisture absorption is 0.1% or less. By comprising in this way, it can suppress that a water | moisture content penetrate | invades inside a nonwoven fabric comprised with the said melt-anisotropic wholly aromatic polyester fiber. Thereby, it can prevent that water vapor | steam penetrate | invades into the inside of a flat type electrochemical cell from the metal terminal extraction part through the end surface of an adhesive sheet, and can obtain a highly safe flat electrochemical cell.

  In the flat electrochemical cell metal terminal sealing adhesive sheet having the above-described configuration, the present invention is characterized in that the porous sheet is made of a synthetic resin having a melting point of 200 ° C. or higher. By comprising in this way, when pinching and heat-bonding a metal terminal, a short circuit with the barrier layer which consists of metal foils, such as aluminum of a package, and a metal terminal can be prevented suitably.

  Further, the present invention provides the flat electrochemical cell metal terminal sealing adhesive sheet having the above-described structure, wherein the polyolefin resin forming the inner layer is made of polypropylene, and the acid-modified polyolefin resin is graft-modified with an unsaturated carboxylic acid. It is characterized by being polypropylene. By comprising in this way, it can prevent that water vapor | steam penetrate | invades into the inside of a flat type electrochemical cell through the end surface of an adhesive sheet from a metal terminal extraction part, and obtains a highly safe flat electrochemical cell. be able to.

  The present invention can prevent a short circuit between a barrier layer made of a metal foil such as aluminum of a package and a metal terminal, which has been a problem in the past, and also has an interlayer strength (laminate) excellent in sealing property and water vapor barrier property. A flat electrochemical cell metal terminal part sealing adhesive sheet having high strength can be provided. Moreover, in the adhesive sheet using the nonwoven fabric which consists of a wholly aromatic polyester fiber, while being excellent in mechanical strength, heat resistance, and electrolyte solution resistance, an adhesive sheet with extremely high interlayer strength can be provided.

These are figures which show typically the typical layer structure of the adhesive sheet for flat electrochemical cell metal terminal part sealing concerning this invention. These are figures which show the basic layer structure of the package used for a flat type electrochemical cell schematically. These are figures explaining one Example of the package used for a flat type electrochemical cell. These are figures explaining the other Example of the package used for a flat type electrochemical cell. These are the figures explaining an example of how to provide the adhesive sheet for metal terminal part sealing used for the metal terminal part of a flat type electrochemical cell.

  First, a flat electrochemical cell package for use in the present invention will be described. As the package, use is made of a laminate A in which at least a base layer A1, a barrier layer A2 made of a metal foil such as aluminum, and a heat-adhesive resin layer A3 made of a general polyolefin resin are laminated as shown in FIG. it can. Examples of the base material layer A1 include a biaxially stretched polyester film, a biaxially stretched nylon film, and a laminate thereof, and the thickness is about 6 to 30 μm. Examples of the barrier layer A2 include metal foils such as aluminum, nickel, and stainless steel, and the thickness is approximately 15 to 80 μm. Examples of the general polyolefin resin forming the heat-adhesive resin layer A3 include low-density polyethylene, medium-density polyethylene, high-density polyethylene, linear low-density polyethylene, ethylene-butene copolymer, and other ethylene-based resins. A propylene resin such as polypropylene, ethylene-propylene copolymer, and ethylene-propylene-butene copolymer may be used alone or as a mixture, and the thickness is generally 20 to 100 μm.

  Next, the present invention will be described in detail below with reference to the drawings and the like, but the form of the flat electrochemical cell battery is the same as the form described in the prior art, and will be explained using the drawings of the prior art. It shall be.

  FIG. 1 is a diagram schematically showing a typical layer structure of an adhesive sheet for sealing a flat electrochemical cell metal terminal according to the present invention, and FIG. 2 is a basic layer of a package used in the flat electrochemical cell. FIG. 3 is a diagram illustrating the configuration, FIG. 3 is a diagram illustrating an embodiment of a package used in a flat electrochemical cell, and FIG. 4 is a diagram illustrating another embodiment of the package used in the flat electrochemical cell. FIG. 5 is a diagram for explaining an example of a method of providing a metal terminal portion sealing adhesive sheet used for a metal terminal portion of a flat electrochemical cell. In the figure, 1 and 1 'are flat electrochemical cell metal terminal sealing adhesive sheets, 2 is a fibrous sheet or porous sheet, 3 is an acid-modified polyolefin resin layer, 10 is a flat electrochemical cell, and 30 is a flat electrochemical cell. A flat electrochemical cell main body, 31 is a metal terminal, A is a laminate, A1 is a base material layer, A2 is a barrier layer made of metal foil, and A3 is a thermoadhesive resin layer.

  FIG. 1 is a diagram schematically showing a layer structure of a flat electrochemical cell battery terminal sealing adhesive sheet according to the present invention, and the flat electrochemical cell metal terminal sealing adhesive sheet 1 includes: The fiber sheet or porous sheet 2 is infiltrated with the heat-adhesive resin layer A3 (corresponding to the inner layer) and the metal terminal 31 and the acid-modified polyolefin resin having adhesiveness to fill the voids of the fiber sheet or porous sheet and both sides. Is a structure in which is coated.

Next, the fiber sheet and the porous sheet will be described. As described in the section of the prior art, the flat electrochemical cell metal terminal sealing adhesive sheet (sometimes referred to as an adhesive sheet) 1 is a metal at the peripheral thermal bonding portion of the flat electrochemical cell 10. It is interposed between the terminal 31 and the exterior film (corresponding to the laminated body A) and thermally bonded, and is not melted and crushed by heat (160 to 190 ° C.) and pressure (1.0 to 2.0 MPa) at the time of thermal bonding. Heat resistance and resistance to electrolytes are required. For this reason, as a fiber or resin constituting the fibrous sheet and the porous sheet, heat resistance and resistance to an electrolytic solution are required. Examples of the fiber include natural fibers such as cellulose, wool, silk, cotton, and hemp. Or glass fiber, carbon fiber, rock fiber, or chemical fiber obtained by fiberizing a known heat-resistant synthetic resin such as polyester, polyamide, polyimide, polymethylpentene, polyphenylene oxide, polysulfone, polyetheretherketone, polyphenylene sulfide, Alternatively, an unstretched sheet made of the well-known heat-resistant synthetic resin described above or a porous sheet stretched in a uniaxial or biaxial direction can be used.

  The fiber sheet is mainly composed of polyester fibers, particularly aromatic polyester fibers synthesized by changing the composition ratio by combining three monomers of aromatic diol, aromatic dicarboxylic acid and aromatic hydroxycarboxylic acid. It does not have an aliphatic hydrocarbon in the chain, and is a copolymer of P-hydroxybenzoic acid and 6-hydroxy-2-naphthoic acid (“Kectal” “Vectran”), P-hydroxybenzoic acid, terephthalic acid, 4, Nonwoven fabrics made of wholly aromatic polyester fibers such as 4′-dihydroxybisphenyl copolymer (“Sumikasuper” manufactured by Sumitomo Chemical) are preferred. In the fully aromatic polyester, molecular orientation (melting anisotropy) is observed in the molten state, and the fiber (melting anisotropic fully aromatic polyester fiber) obtained by spinning this is further advanced in molecular orientation. A heat-resistant non-woven fabric having high mechanical strength and low hygroscopicity can be obtained easily, and a heat-resistant non-woven fabric excellent in resin impregnation property can be obtained. Therefore, a heat-resistant nonwoven fabric made of melt anisotropic wholly aromatic polyester fiber is most suitable.

The nonwoven fabric composed of such melt-anisotropic wholly aromatic polyester fibers can be used to change the permeability of the acid-modified polyolefin resin applied and infiltrated in the molten state, and the thickness of the resin layer after infiltration. An amount of 5 to 25 g / m ² and a density of 0.15 to 0.45 g / cm ³ are preferable. If the basis weight is less than 5 g / m ² and the density is less than 0.15 g / cm ³ , the effect of preventing short circuit cannot be expected, and the nonwoven fabric has insufficient strength and may have poor processability. Further, when the basis weight is 25 g / m ² and the density exceeds 0.45 g / cm ³ , the acid-modified polyolefin resin layer that is melt-coated becomes difficult to penetrate, and the acid-modified polyolefin-based resin is restricted due to the total thickness of the adhesive sheet. Since the thickness of the resin layer becomes thin, there is a possibility that sufficient seal strength cannot be obtained due to seal thinning.

  Moreover, it is preferable that the nonwoven fabric comprised by the said melt-anisotropic wholly aromatic polyester fiber has a moisture absorption rate of 0.1% or less in an environment of 25 ° C. and 65% RH. By setting the moisture absorption rate to 0.1% or less, moisture can be prevented from penetrating through the nonwoven fabric composed of the melt-anisotropic wholly aromatic polyester fiber. As a result, water vapor can be further prevented from entering the inside of the flat electrochemical cell through the end face of the adhesive sheet from the metal terminal extraction part, and a highly safe flat electrochemical cell can be obtained. it can. In the present invention, the moisture absorption rate represents a change in weight from the start when the sample is stored under a constant temperature and humidity condition and the sample weight reaches equilibrium in terms of weight percentage.

  In addition, the nonwoven fabric composed of such melt-anisotropic wholly aromatic polyester fibers can be produced by either a wet method or a dry method, but the dry method is preferred from the viewpoint of cost, solvent resistance, etc. It is preferable to manufacture by the method. Specifically, the melt anisotropic fully aromatic polyester is melt-spun, and at the same time, the spun product is blown off with a high-temperature high-speed fluid to accumulate on the collecting surface to form a web, and the web is subjected to calendering and heat treatment. This is a non-woven fabric. As such a melt-anisotropic wholly aromatic polyester nonwoven fabric, for example, “Vecruz” made by Kuraray can be used.

In addition, as a method for forming the porous sheet, for example, a needle punch method for pressing a heated needle, an embossing roll method, a polishing roll, a grindstone, a polishing tape, or the like is used to draw an unstretched sheet or stretched in a uniaxial or biaxial direction. Hot melt punching method that melts and punches a sheet, physical punching method using a knife, cutter, or roll having a cutting edge (rotary die roll), laser beam processing, processing methods such as corona discharge, plasma discharge, etc. The method may be appropriately selected and used, or the heat-resistant synthetic resin kneaded with an inorganic material may be formed into a sheet and may be made into a porous sheet by a method of stretching. As the thickness of the adhesive sheet after the fiber sheet or porous sheet is coated with the acid-modified polyolefin resin, considering the burr of the metal terminal and the resin thinning after heat sealing the acid-modified polyolefin resin layer 50 to 120 μm is preferable.

  Next, a method for coating the both sides of the fibrous sheet or porous sheet 2 by coating and infiltrating an acid-modified polyolefin resin on both sides of the fibrous sheet or porous sheet 2 will be described. First, a sheet-like fibrous sheet or porous sheet is fed out, and a molten acid-modified polyolefin resin is extruded and coated on one side of the sheet, and then a molten acid-modified polyolefin resin is extruded on the other side of the sheet. It is formed by laminating with a coat.

  Next, the acid-modified polyolefin resin layer 3 will be described. The acid-modified polyolefin resin layer 3 is provided for thermal bonding with the metal terminal 31 (see FIG. 5) and the thermoadhesive resin layer A3 (see FIG. 2) made of a general polyolefin resin which is an inner layer of the package. It is a layer, and it is necessary to appropriately select and use it depending on the resin type used for the thermal adhesive resin layer A3 (see FIG. 2). As the acid-modified polyolefin resin layer 3, the acid-modified polyolefin resin described in the section of the prior art can be used. For example, a polyolefin resin graft-modified with an unsaturated carboxylic acid, ethylene or propylene, and Acrylic acid or a copolymer with methacrylic acid, or a metal-crosslinked polyolefin resin, etc., if necessary, butene component, ethylene-propylene-butene copolymer, amorphous ethylene-propylene copolymer, A propylene-α-olefin copolymer, an olefin-based elastomer or the like may be added by 5% or more. In consideration of moisture resistance and heat resistance, a polyolefin resin graft-modified with an unsaturated carboxylic acid, particularly a polypropylene resin graft-modified with an unsaturated carboxylic acid is preferred. Further, considering the above-described abnormal heat generation and durability due to an increase in internal pressure, a resin to which an olefin-based elastomer having no melting point is added at 120 ° C. or lower is suitable.

  The acid-modified polyolefin resin layer 3 is formed by heat-melting and extruding the acid-modified polyolefin resin described above onto the fibrous sheet or porous sheet 2 from a T-die extruder. The acid-modified polyolefin layer 3 has a thickness of 10 μm or more, preferably 20 to 60 μm. If it is less than 10 μm, sufficient heat resistance of the extruded molten resin is insufficient, so that sufficient laminate strength cannot be obtained, and it is difficult to obtain sufficient seal strength because the acid-modified polyolefin resin becomes insufficient in strength due to seal thinning. It is. If it exceeds 60 μm, the total thickness of the adhesive sheet increases, the water vapor barrier property from the end face decreases, and it is difficult to obtain a significant improvement effect in cost effectiveness (laminate strength, seal strength).

The acid-modified polyolefin resin layer 3 may be a colored layer by adding a pigment as necessary. As the pigment used for this, various inorganic pigments can be used, but it is a material generally used in the battery, there is no possibility of elution to the electrolyte, and the coloring effect is large and the adhesiveness is high. A sufficient coloring effect can be obtained with an addition amount that does not hinder, and the apparent melt viscosity of the added resin can be increased without melting by heat, and the pressure part is thin during thermal bonding (sealing) Carbon (carbon, graphite) is preferred for the reason that it is possible to prevent the deterioration of the seal strength by preventing the reduction of the seal strength. For example, when carbon black having an average particle size of about 0.03 μm is used, the amount added is preferably 0.05 to 0.3 parts by weight, more preferably 0.1 to 100 parts by weight with respect to 100 parts by weight of the resin. 0.2 parts by weight. Thus, by using the acid-modified polyolefin layer 3 as a colored layer, the presence or absence of the adhesive sheet 1 can be easily detected by a sensor, or can be easily inspected visually.

Next, the present invention will be described in more detail with reference to the following examples.
(Creation of laminated body for flat electrochemical cell)
One side of an aluminum foil (thickness 40 μm) and a thickness of 25 μm that have been subjected to chemical conversion treatment (phosphate chromate treatment) on both sides with a chemical conversion treatment solution consisting of three components of phenol resin, chromium fluoride (trivalent) compound and phosphoric acid in advance. The biaxially stretched nylon film is laminated via a urethane adhesive, and the other surface of the aluminum foil and the unstretched polypropylene film having a thickness of 30 μm are graft-modified with an acid-modified polypropylene resin (unsaturated carboxylic acid). (Laminated polypropylene) and heated to a temperature equal to or higher than the softening point of the acid-modified polypropylene resin with hot air to prepare a laminate for use in the examples.
(Creation of adhesive sheet for sealing flat electrochemical cell metal terminals)

Nonwoven fabric made of melt-anisotropic wholly aromatic polyester fibers (weighing 9 g / cm ² , thickness 40 μm, density 0.16 g / cm ³ , moisture absorption rate 0.1% or less (25 ° C., 65% RH), manufactured by Kuraray “Vecruz MBBK9F The maleic acid-modified polypropylene was extruded and applied to one side of 46) by a T-die extruder to a thickness of 46 μm, and then the maleic acid-modified polypropylene was extruded to a thickness of 46 μm by a T-die extruder on the other side of the nonwoven fabric. An adhesive sheet of the present invention having a thickness of 100 μm was obtained.

Nonwoven fabric made of melt-anisotropic wholly aromatic polyester fibers (weight per unit: 14 g / cm ² , thickness: 50 μm, density: 0.21 g / cm ³ , moisture absorption: 0.1% or less (25 ° C., 65% RH), manufactured by Kuraray “Vecruz MBBK14F The maleic acid-modified polypropylene is extruded and coated to a thickness of 44 μm using a T-die extruder on one side of “)”, and then the maleic acid-modified polypropylene is extruded and coated to a thickness of 44 μm using a T-die extruder on the other side of the nonwoven fabric. An adhesive sheet of the present invention having a thickness of 100 μm was obtained.

Nonwoven fabric made of melt-anisotropic wholly aromatic polyester fibers (weighing 22 g / cm ² , thickness 89 μm, density 0.28 g / cm ³ , moisture absorption rate 0.1% or less (25 ° C., 65% RH), Kuraray “Vecruz MBBK22F The maleic acid-modified polypropylene is extruded and applied to one side of 38) by a T-die extruder, and then the maleic acid-modified polypropylene is extruded and applied to the other side of the nonwoven fabric to a thickness of 38 μm by a T-die extruder. An adhesive sheet of the present invention having a total thickness of 100 μm was obtained.

After extruding and coating maleic acid-modified polypropylene to a thickness of 44 μm with a T-die extruder on one side of a nonwoven fabric made of polyethylene terephthalate fibers (weighing 15.0 g / cm ² , thickness 35 μm, density 0.22 g / cm ³ ) On the other side of the nonwoven fabric, maleic acid-modified polypropylene was extruded and applied to a thickness of 44 μm with a T-die extruder to obtain an adhesive sheet of the present invention having a total thickness of 100 μm.

Nonwoven fabric made of melt-anisotropic wholly aromatic polyester fibers (weight per unit: 14 g / cm ² , thickness: 50 μm, density: 0.21 g / cm ³ , moisture absorption: 0.1% or less (25 ° C., 65% RH), manufactured by Kuraray “Vecruz MBBK14F The maleic acid-modified polyethylene is extruded and coated to a thickness of 44 μm using a T-die extruder on one side of “)”, and then the maleic acid-modified polyethylene is extruded and coated to a thickness of 44 μm using a T-die extruder on the other side of the nonwoven fabric. An adhesive sheet of the present invention having a total thickness of 100 μm was obtained.

(Comparative Example 1)
One side of PET (12 μm) subjected to double-sided corona discharge treatment was coated with 50 mg / m ² of an isocyanate-based adhesion promoter as a solid content, and maleic acid-modified polypropylene (hereinafter referred to as PPa) was T-die extruder And then coated with maleic acid-modified polypropylene on the other side of PET (12 μm) to a thickness of 44 μm using a T-die extruder, followed by aging at 45 ° C. for 72 hours for comparison. The adhesive sheet of Example 1 was obtained.

(Comparative Example 2)
A 100 μm thick maleic acid-modified polypropylene film of 100 μm was used as an adhesive sheet.

  Using the adhesive sheets of Examples 1 to 5 and Comparative Examples 1 and 2 prepared above, the initial laminate strength, the laminate strength after immersion in the electrolyte (electrolytic solution laminate strength), the initial seal strength, and the electrolyte encapsulation The subsequent seal strength (electrolytic solution seal strength), insulation, water vapor barrier properties, heat shrinkage, and leakage were evaluated by the following evaluation methods. The results are summarized in Table 1.

  (1) Initial laminate strength: The adhesive sheet was cut to a width of 15 mm, partially peeled from the end face while applying ethyl acetate to the adhesive interface, then measured with a Tensilon at a pulling speed of 50 mm / min, and the average strength at that time was The measured value was used. In the case of partial peeling, the film was broken due to cohesive failure between the resin layers and the laminate strength could not be measured.

  (2) Electrolytic solution laminating strength: The adhesive sheet was cut into a 30 × 70 mm rectangular shape, and this was immersed in an electrolytic solution (1 mol / liter lithium hexafluorophosphate solution) at 60 ° C. for 7 days. After taking out later and trimming both ends by 7.5 mm to 15 × 70 mm, after partially peeling in the same manner as the initial laminate strength described above, the tensile strength was measured with a Tensilon at 50 mm / min, and the average strength at that time was The measured value was used. In the case of partial peeling, the film was broken due to cohesive failure between the resin layers and the laminate strength could not be measured.

  (3) Initial sealing strength: An aluminum foil (metal terminal) treated with phosphoric acid chromate having a width of 4 mm, a length of 30 mm, and a thickness of 100 μm is composed of two adhesive sheets (width 8 mm, length 15 mm). While sandwiched between them, seal with a hot plate of 25 mm width in a direction orthogonal to the length direction of the aluminum foil (sealing conditions: 190 ° C., 0.5 MPa, 3 seconds twice) A sample sandwiched between two adhesive sheets (hereinafter referred to as a metal terminal sample with an adhesive sheet) was prepared. Cut the laminated body to be the above-mentioned packaging body to produce two 60 × 75 mm laminated body test samples and superimpose them so that the sealant film surfaces face each other, and on the end side of 60 mm length as described above After inserting the prepared metal terminal sample with an adhesive sheet and sealing the edge with the metal sheet sample with the adhesive sheet with a hot plate (sealing conditions: 190 ° C., 1.0 MPa, 3 seconds), an aluminum terminal And an initial seal strength measurement sample having a width of 4 mm and a length of 30 mm, in which the adhesive sheet and the laminate were integrated on both surfaces of the aluminum foil, was prepared. Each of the laminates on both sides of the metal terminal of the sample for initial seal strength measurement was fixed to a jig, and the seal strength was measured with an autograph at a pulling speed of 300 mm / min. The average strength at that time was taken as a measured value. The obtained measured value was converted into seal strength per 15 mm width to obtain initial seal strength.

(4) Electrolyte-resistant seal strength: Cut the laminated body to be the above-prepared packaging body to produce two 60 × 75 mm laminated body test samples and superimpose them so that the sealant film faces face each other, and 60 mm Insert the metal sheet sample with an adhesive sheet created above on the end side of the length, insert the metal terminal sample with the adhesive sheet, the opposite end sides, and the metal terminal sample with the adhesive sheet. The edge opposite to the inserted edge is sealed with a hot plate (sealing conditions: 190 ° C., 1.0 MPa, 3 seconds), and the edge inserted with the metal terminal sample with the adhesive sheet and the edge A heat-bonding portion having a width of 7 mm is formed on the opposite end sides, and a heat-welding portion having a width of 10 mm is formed on both opposite sides orthogonal to the end side where the metal terminal sample with the adhesive sheet is inserted. We have created a four-side sealed packaging bag to form a part. In the packaging bag, 1 g of an electrolytic solution [lithium hexafluorophosphate was dissolved in a mixed solution [ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1/1/1 (volume ratio) and 1 mol / liter What was made into a lithium hexafluorophosphate solution] was sealed. Then, after storing the packaging bag in a constant temperature and humidity chamber at 60 ° C. and 90% RH for 7 days so that the edge thermal bonding part into which the metal terminal sample with the adhesive sheet is inserted is below, the removed packaging bag is The sample was cut along an aluminum terminal, and a 4 mm wide and 30 mm long anti-electrolytic solution sealing strength measurement sample in which an adhesive sheet and a laminate were integrated on both sides of an aluminum foil was prepared. Each of the laminates on both sides of the metal terminal of the sample for measuring anti-electrolytic solution seal strength is fixed to a jig, and the seal strength is measured with an autograph at a pulling speed of 300 mm / min, and the average strength at that time is taken as a measured value. The measured value was converted into seal strength per 15 mm width to obtain anti-electrolytic solution seal strength.

  (5) Insulating property: The laminate and the adhesive sheet, which were the above-prepared packages, were cut to prepare a 60 mm square test sample. The laminate is disposed with the sealant film surfaces of the laminate facing each other, and a nickel foil (metal terminal) having a width of 4 mm, a length of 80 mm, and a thickness of 100 μm is sandwiched between two adhesive sheets. Inserted between the laminates in a sandwiched state and connected to the nickel foil and the aluminum foil of the laminate, a tester terminal is connected, and in this state, a hot plate having a width of 7 mm in a direction perpendicular to the length direction of the nickel foil (Sealing conditions: 190 ° C., 1.0 MPa, 3 seconds). For such a sample, the time until the nickel foil and the aluminum foil of the laminate are short-circuited is measured, and 120 seconds or more are indicated as ◎, and 15 seconds or more and less than 120 seconds are indicated as good insulation. The mark is indicated by a mark, the mark of 8 seconds or more and less than 15 seconds is indicated by a mark Δ, and the mark of less than 8 seconds is indicated by a mark x, indicating that the insulation is inferior.

  (6) Water vapor barrier property: The laminate prepared as above is cut to produce a 100 × 120 mm laminate test sample, and the adhesive sheet is cut to obtain a 15 × 120 mm adhesive sheet test sample. Was made. The laminate test sample is folded in two so that the sealant film surfaces of the laminate face each other, and the two adhesive sheet test samples are inserted into the end side of 120 mm in length, and then face each other. Both end sides and the end side where the adhesive sheet test sample is inserted are sealed with a hot plate (sealing conditions: 190 ° C., 1.0 MPa, 3 seconds), and 10 mm wide thermal bonding portions are respectively provided on the opposite end sides. A three-sided sealed packaging bag was formed which was formed and formed with a 7 mm-wide heat-bonding portion on the edge where the adhesive sheet test sample was inserted. In addition, 3 g of a mixed solution [ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1/1/1 (volume ratio)] was sealed in the packaging bag. After that, the packaging bag trimmed so that the 7 mm width thermal bonding portion becomes 3 mm width is stored in a constant temperature and humidity chamber at 60 ° C. and 90% RH for 7 days, and the amount of water increase in the mixed solution is measured. A water increase of less than 100 ppm is indicated by ◎ as an excellent water vapor barrier property, a water increase of 100 ppm or more and less than 140 ppm is indicated by a circle as a water vapor barrier property, and a water increase of 140 ppm or more and less than 200 ppm is used in the water vapor barrier property. △ is marked as acceptable.

(7) Heat-resistant shrinkage: The laminate and the adhesive sheet, which were the package prepared above, were cut to prepare a 60 mm square test sample. The laminate is disposed with the sealant film surfaces of the laminate facing each other, and a nickel foil (metal terminal) having a width of 4 mm, a length of 80 mm, and a thickness of 100 μm is sandwiched between two adhesive sheets. In the sandwiched state, the adhesive sheet is inserted between the laminates so as to protrude 2 mm from the laminate, and in this state, sealed with a 7 mm wide hot plate in a direction perpendicular to the length direction of the nickel foil (seal Conditions: 190 ° C., 1.0 MPa, 3 seconds). Then, the corrugation of the protruding portion of the adhesive sheet is visually evaluated and the degree of contraction of the metal terminal portion toward the seal portion of the adhesive sheet is evaluated, and the heat shrinkage of less than 1 mm without the corrugation of the adhesive sheet. Is marked with ○ as good heat shrinkage resistance, and when the adhesive sheet is wavy and heat shrinkage of 1 mm or more is shown as x with poor heat shrinkage resistance, but the adhesive sheet is wavy but less than 1 mm In the case of heat shrinkage, the Δ mark indicates that it can be used.

  (8) Presence / absence of leakage: The laminate produced as the above package is cut to produce a 60 × 160 mm laminate test sample, and the adhesive sheet is cut to obtain a 15 × 60 mm adhesive sheet test sample. Was made. The laminate test sample is folded in two so that the sealant film surfaces of the laminate face each other, and the nitric acid-cleaned nickel having a width of 4 mm, a length of 20 mm, and a thickness of 100 μm on the end side of the 60 mm length Insert the foil (metal terminal) and the aluminum foil (metal terminal) treated with phosphoric acid chromate with the same dimensions in a state of being sandwiched between two adhesive sheets in a state of being separated so as not to contact, Three end sides were sealed with a hot plate (sealing conditions: 190 ° C., 1.0 MPa, 3 seconds) to prepare a three-side sealed packaging bag having a 7 mm-wide heat-bonded portion. In the packaging bag, 3 g of electrolytic solution [lithium hexafluorophosphate was dissolved in a mixed solution [ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1/1/1 (volume ratio) and 1 mol / liter What was made into a lithium hexafluorophosphate solution] was sealed. Then, this packaging bag was stored for 7 days in a 60 degreeC thermostat, and the presence or absence of the electrolyte solution leakage from a metal terminal and an adhesive sheet was evaluated visually.

  As is clear from Table 1, the adhesive sheets of Examples 1 to 5 and Comparative Example 1 showed excellent performance in initial laminate strength. However, in the laminate strength after electrolytic solution immersion (electrolytic solution laminate strength), Comparative Example 1 showed a decrease in laminate strength, while Examples 1 to 5 showed no decrease in laminate strength. On the other hand, the adhesive sheets of Examples 1 to 5 and Comparative Example 2 showed high seal strengths both in the initial seal strength and the seal strength after electrolytic solution encapsulation (electrolytic solution seal strength). On the other hand, the adhesive sheet of Comparative Example 1 had a low initial seal strength, and the result that the seal strength after electrolytic solution immersion (electrolytic solution seal strength) was further reduced was obtained. Further, in terms of insulation, Examples 2, 3, 5 and Comparative Example 1 were the best, followed by Examples 1 and 4. In Comparative Example 2, there was practically no insulating effect. The water vapor barrier properties were good results in Examples 1 to 5 and Comparative Example 2, but Comparative Example 1 was clearly inferior. In the heat shrinkability, Examples 1 to 5 and Comparative Example 1 showed excellent performance, but Comparative Example 2 was clearly inferior.

From the above, the adhesive sheets of Examples 1 to 5 are high in both laminate strength and seal strength, have no decrease in interlayer strength (laminate strength) before and after immersion in the electrolyte, and have metal terminals even after the electrolyte is enclosed and stored. It can be seen that there is no decrease in the sealing strength at the sandwiched thermal bonding portion, and the sealing performance is very excellent. The heat shrinkage is related to the undulation and heat shrinkage of the adhesive sheet. Usually, the adhesive sheet is thermally bonded in a state of protruding about 2 mm from the edge of the package. When folding and using the battery pack side of the lithium battery, there is a risk of short circuit due to contact between the barrier layer made of the metal foil exposed on the end face of the package and the metal terminal when waving or heat shrinkage occurs in the adhesive sheet, The performance which can prevent this is shown.

1,1 'flat electrochemical cell metal terminal sealing adhesive sheet 2 fibrous sheet or porous sheet 3 acid-modified polyolefin resin layer 10 flat electrochemical cell 30 flat electrochemical cell body 31 metal terminal A laminate A1 Base material layer A2 Barrier layer made of metal foil A3 Thermal adhesive resin layer

Claims (2)

A packaging material having at least an inner layer made of a polyolefin-based resin having thermal adhesion and a barrier layer made of a metal foil, and containing an electrochemical element having a positive electrode and a negative electrode, and a metal connected to the positive electrode and the negative electrode, respectively Flat electrochemical cell metal terminal portion sealed between the inner layer and the metal terminal in the metal terminal extraction portion of a flat electrochemical cell sandwiched in a state where the terminal protrudes outward and sealed by a peripheral thermal bonding portion Adhesive sheet for
該扁flat electrochemical cell metal terminal portion sealing adhesive sheet basis weight 5 to 25 g / m ^2, the fibrous sheet for the density 0.15~0.45g / cm ³ and the inner layer and the metal terminal adhesion An adhesive sheet for sealing a flat electrochemical cell metal terminal portion, which is coated with an acid-modified polyolefin-based resin layer. The fiber constituting the fibrous sheet is a natural fiber of cellulose, wool, silk, cotton, or hemp, or glass fiber, carbon fiber, rock fiber, or polyester, polyamide, polyimide, polymethylpentene, polyphenylene. A chemical fiber obtained by fiberizing one of oxide, polysulfone, polyether ether ketone, and polyphenylene sulfide, or an unstretched sheet or a stretched sheet stretched in a uniaxial or biaxial direction. 2. The adhesive sheet for sealing a flat electrochemical cell metal terminal portion according to claim 1, wherein the adhesive sheet is one made porous.

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