JP2011216356A - Packaging material for electrochemical cell, and electrochemical cell using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packaging material for electrochemical cell which exhibits a stable insulation performance.SOLUTION: The packaging material 110 for electrochemical cell is constructed by laminating at least a base material layer 111, a metal foil layer 112, an acid modified polyolefin layer 114, and a thermally adhesive resin layer 115 in order. A cover film 116 is installed on the upper side of the outermost layer of the base material layer 111 through an adhesive layer 117.

Description

  The present invention relates to an electrochemical cell packaging material and an electrochemical cell using the same, and more particularly to an electrochemical cell packaging material having stable insulation.

  The lithium ion battery is also referred to as a lithium secondary battery, and includes a liquid, gel-like, or polymer-polymer electrolyte solution, and a positive electrode / negative electrode active material made of a polymer polymer. The configuration of the lithium ion battery is composed of a battery body composed of a positive electrode current collector / positive electrode active material layer / electrolyte layer / negative electrode active material layer / negative electrode current collector and an exterior body that wraps the battery body to form an exterior body. A multilayer film is used as a packaging material.

  FIG. 2 is a cross-sectional view showing a layer structure of a conventional electrochemical cell packaging material. As shown in FIG. 2, the conventional electrochemical cell packaging material 210 includes a base material layer 211, an aluminum foil layer 212, an acid layer. An adhesive layer 214 made of a modified polyolefin resin and a thermal adhesive resin layer 215 are sequentially laminated, and the base material layer 211 is made of a single-layer or multilayer heat-resistant polymer film, for example, a polyester film or a polyamide film is used. (Patent Document 1).

  FIG. 3 is a perspective view of a conventional embossed type lithium ion battery 221. The lithium ion battery 221 is sandwiched with the metal terminal 224 protruding outside the exterior body 220, and the peripheral portion including the sandwiched portion is heated. The lithium ion battery main body 222 containing the electrolytic solution is hermetically stored in the exterior body 220 by sealing.

  Conventionally, lithium ion batteries have been used for small electric appliances such as mobile phones and laptop computers, but in recent years, there has been a tendency to use them for electric bicycles, automobiles, etc. It tends to increase output.

JP 2007-134304 A

  However, when the base material layer 211 is a single polyamide film layer, the insulating property of the lithium ion battery 221 may be lowered because the insulating property of the polyamide film itself is low. In addition, even when the base material layer 211 is a single layer of polyethylene terephthalate film or two layers of polyethylene terephthalate film and polyamide film from the outside, if the surface of the polyethylene terephthalate film is shallowly scratched, the insulating property of the lithium ion battery 221 may be reduced. There is. Therefore, when a plurality of lithium ion batteries 221 are used side by side in a stack, when the insulation of some of the lithium ion batteries 221 is lowered and discharged, other adjacent lithium ion batteries 221 may be destroyed.

  Then, in view of the said problem, this invention aims at providing the packaging material for electrochemical cells which prevents the crack generation | occurrence | production of the base-material layer surface, and shows the stable insulation.

  In order to achieve the above object, the first configuration of the present invention is an electrochemical cell configured by laminating at least a base material layer, a metal foil layer, an adhesive layer, and a thermal adhesive resin layer sequentially. Packaging material, comprising an adhesive layer on the upper surface of the outermost layer of the base material layer and a cover film covering the adhesive layer, and the adhesive strength between the adhesive layer and the cover film is the adhesion between the adhesive layer and the base material layer It is characterized by higher than strength.

  According to this configuration, since the cover film is provided in advance on the surface of the base material layer of the packaging material for electrochemical cells, it is possible to prevent the surface of the base material layer from being damaged in the manufacturing process of the electrochemical cell. In addition, after the electrochemical cell is completed, the electrochemical cell is mounted on an electronic device, and then the cover film is peeled off, so that the base material layer can be protected up to the final product stage to ensure the insulation of the electrochemical cell. . Moreover, since the adhesive strength between the adhesive layer and the cover film is higher than the adhesive strength between the adhesive layer and the base material layer on the surface of the base material layer, the cover film can be easily formed without leaving the adhesive layer on the base material layer side. Can be peeled off.

  The second configuration of the present invention is characterized in that, in the packaging material for electrochemical cells, the cover film is subjected to an easy adhesion treatment on the joint surface with the adhesive layer.

  According to this configuration, the cover film and the adhesive layer are firmly adhered by an easy adhesion treatment, and the cover film can be easily peeled without leaving the adhesive layer on the base material layer side.

  The third configuration of the present invention is characterized in that in the packaging material for electrochemical cells, the easy adhesion treatment is a corona treatment.

  According to this structure, an easy adhesion process can be easily performed to the cover film surface.

  According to a fourth aspect of the present invention, in the packaging material for electrochemical cells, the easy adhesion treatment is an anchor coat treatment.

  According to this structure, an easy adhesion process can be easily performed to the cover film surface.

  A fifth configuration of the present invention is characterized in that, in the packaging material for electrochemical cells, the cover film is formed of a polyethylene terephthalate film.

  According to this configuration, the strength of the cover film is increased, the base material layer can be stably protected, and the cover film can be easily adhered and peeled off.

  According to a sixth aspect of the present invention, in the electrochemical cell packaging material, the cover film is made of a nylon film.

  According to this structure, the base material layer can be protected and insulation can be ensured without lowering the embossability of the packaging material for electrochemical cells.

  According to a seventh aspect of the present invention, there is provided an electrochemical cell manufactured using the electrochemical cell packaging material.

  According to this configuration, an electrochemical cell exhibiting stable insulation can be provided.

These are sectional drawings which show the layer structure of the packaging material for electrochemical cells of this invention. These are sectional drawings which show the layer structure of the conventional packaging material for electrochemical cells. These are the perspective views of the lithium ion battery comprised with the exterior body formed using the conventional packaging material for electrochemical cells.

  The present invention is a packaging material for electrochemical cells having a stable insulating property, and will be described in more detail with reference to the drawings. In addition, the part which is common in FIG. 2, FIG.

  FIG. 1 is a cross-sectional view showing a layer structure of an electrochemical cell packaging material which is an example of an embodiment of the present invention. As shown in FIG. 1, the electrochemical cell packaging material 110 according to this embodiment is made of polyethylene terephthalate. A film (hereinafter referred to as PET film) 116, an acid-modified polyethylene 117, a stretched nylon film layer 111, an aluminum foil layer 112, an acid-modified polypropylene layer 114, and a polypropylene layer 115 are sequentially laminated. In addition, the packaging material 110 for electrochemical cells of the present invention includes the above-described layers and includes the case where different layers are interposed between the respective layers in the technical scope of the present invention. The PET film 116 is an example of the “cover film” in the present invention, the acid-modified polyethylene 117 is an example of the “adhesive layer” in the present invention, and the stretched nylon film layer 111 is the “base layer” in the present invention. The aluminum foil layer 112 is an example of the “metal foil layer” in the present invention, and the acid-modified polypropyne layer 114 and the polypropylene layer 115 are examples of the “thermal adhesive resin layer” in the present invention.

  Here, the PET film 116 protects the surface of the stretched nylon film layer 111. Thereby, when manufacturing the lithium ion battery 211 using the packaging material 110 for electrochemical cells, it is possible to prevent the surface of the stretched nylon film layer 111 from being scratched. Further, after the lithium ion battery 211 is completed, the surface of the stretched nylon film layer 111 is protected and the stretched nylon film layer 111 is protected until the final product stage by peeling the PET film 116 after the lithium ion battery is mounted on an electronic device. Therefore, it is possible to prevent the insulating property of the lithium ion battery 211 from being deteriorated due to the scratch.

  The acid-modified polyethylene 117 has adhesiveness or pressure sensitivity, and the adhesion surface of the PET film 116 to the acid-modified polyethylene 117 is subjected to an easy adhesion treatment by corona treatment. The acid-modified polyethylene 117 and the PET film 116 Is higher than the adhesive strength between the acid-modified polyethylene 117 and the stretched nylon film layer 111. Thereby, when peeling PET film 116, it can peel without leaving the acid-modified polyethylene 117 on the stretched nylon film layer 111 side.

  The easy adhesion treatment applied to the PET film 116 is not limited to the corona treatment, and an anchor coat treatment may be performed.

  The PET film 116 only needs to have sufficient strength to protect the stretched nylon film layer 111. As the “cover film” in the present invention, in addition to polyethylene terephthalate, polyamide, polyethylene naphthalate (PEN), Non-stretched or stretched films such as polyphenylene sulfide (PPS), polymethylpentene (TPX (registered trademark)), polyacetal (POM), cyclic polyolefin, and polyethylene (PP) can be used. Polyethylene terephthalate is more desirable because it is inexpensive and has high strength, so that it can be easily handled in the bonding process.

  Moreover, the acid-modified polyethylene 117 contains a tackifying resin and has tackiness or pressure sensitivity. In this case, examples of the tackifying resin used include rosins (polymerized rosin, hydrogenated rosin, rosin ester, etc.), terpene resins, terpene phenol resins, coumarone indene resins, petroleum resins, and the like.

  Further, since the acid-modified polyethylene 117 has no residual solvent and is excellent in chemical resistance, water resistance and oil resistance, the adhesive strength can be maintained for a long time. Resins other than acid-modified polyethylene may also be used, such as polyolefin resins graft-modified with unsaturated carboxylic acids, copolymers of ethylene or propylene and acrylic acid, or methacrylic acid, or metal-crosslinked polyolefin resins. In addition, 5% or more of a butene component, an ethylene-propylene-butene copolymer, an amorphous ethylene-propylene copolymer, a propylene-α-olefin copolymer, etc. may be added as necessary. Also good.

  Moreover, you may use resin which mixed elastomer resin with these polyolefin resin, and a softness | flexibility, heat resistance, and impact resistance can be improved by mixing elastomer resin. In addition to the elastomer, a tackifier can be added to impart flexibility and the like to the polyolefin resin. Thereby, the moldability of the packaging material 110 for electrochemical cells can be improved. The “adhesive layer” in the present invention may use, for example, an adhesive such as an acrylic resin or an epoxy resin in addition to the acid-modified polyethylene containing a tackifier.

  The stretched nylon film layer 111 can use a stretched polyester other than the stretched nylon film, and examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, polycarbonate, and the like. It is done. Examples of nylon include polyamide resin, that is, nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), and the like.

  In addition, in order to improve the pinhole resistance and the insulation when the battery is used as a battery outer package, the base material layer can be laminated with films of different materials in addition to the polyester film or nylon film.

  The aluminum foil layer 112 is a layer for preventing water vapor from entering the inside of the lithium ion battery 121 from the outside, and stabilizes pinholes and processability (pouching, embossing formability) of the metal foil layer alone. In order to have pinhole resistance, aluminum having a thickness of 15 μm or more is used.

  In addition, in order to improve the generation of pinholes and to make the outer body type of the lithium ion battery an embossed type, the aluminum material used as the aluminum foil layer 112 is selected in order to prevent the occurrence of cracks in the embossing molding. It is desirable that the iron content is 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight.

  As a result, compared with aluminum that does not contain iron, aluminum has good spreadability, and the occurrence of pinholes due to bending as an exterior body is reduced, and the side wall can be easily formed when embossing the packaging material. it can. In addition, when the iron content is less than 0.3% by weight, effects such as prevention of pinholes and improvement of embossing formability are not observed, and the iron content of aluminum exceeds 9.0% by weight. In this case, the flexibility as aluminum is hindered, and the bag-making property as a packaging material is deteriorated.

  In addition, aluminum produced by cold rolling changes its flexibility, waist strength, and hardness under annealing (so-called annealing treatment) conditions. Aluminum which tends to be soft with some or complete annealing is preferred.

  The acid-modified polypropylene layer 114 is a layer provided for stably bonding the aluminum foil layer 112 and the polypropylene layer 115, and it is necessary to appropriately select and use the resin type used for the polypropylene layer 115. When using acid-modified polyolefin resins other than acid-modified polypropylene, there are polyolefin resins graft-modified with unsaturated carboxylic acids, copolymers of ethylene or propylene and acrylic acid, or methacrylic acid, or metal-crosslinked polyolefin resins. If necessary, a butene component, an ethylene-propylene-butene copolymer, an amorphous ethylene-propylene copolymer, a propylene-α-olefin copolymer, or the like may be added by 5% or more.

When using acid-modified polypropylene,
(1) A homotype having a bigat softening point of 115 ° C or higher and a melting point of 150 ° C or higher,
(2) A copolymer of ethylene-propylene having a bigat softening point of 105 ° C or higher and a melting point of 130 ° C or higher (random copolymer type)
(3) A simple substance or a blended product obtained by acid-modified polymerization using an unsaturated carboxylic acid having a melting point of 110 ° C. or higher can be used.

  As the polypropylene layer 115, polypropylene is preferably used, but polyolefin having thermal adhesiveness can be used. For example, a linear low density polyethylene, a medium density polyethylene single layer or a multilayer, or a linear low density polyethylene, a blend resin of medium density polyethylene can be used. Polypropylene can be classified into random propylene, homopropylene, block propylene and the like.

  Each of the above types of polypropylene, ie, random polypropylene, homopolypropylene, and block polypropylene, includes a low crystalline ethylene-butene copolymer, a low crystalline propylene-butene copolymer, and a three-component copolymer of ethylene, butene, and propylene. An antiblocking agent (AB agent) such as a polymer terpolymer, silica, zeolite, or acrylic resin beads, a fatty acid amide slip agent, or the like may be added. Also, the above-mentioned types of polypropylene layers may be combined in a timely manner to form a multilayer.

  The present invention is not limited to the above-described embodiments, and various modifications are possible. Embodiments obtained by appropriately combining technical means disclosed in different embodiments are also included in the present invention. Included in the technical scope.

110 Packaging material for electrochemical cells 111 Stretched nylon film layer (base material layer)
112 Aluminum foil layer (metal foil layer)
114 acid-modified polypropylene layer (thermal adhesive resin layer)
115 Polypropylene layer (thermal adhesive resin layer)
116 PET film (cover film)
117 acid-modified polyethylene (adhesive layer)
211 Base material layer 212 Aluminum foil layer 214 Adhesive layer 215 Thermal adhesive resin layer 220 Exterior body 221 Lithium ion battery 222 Lithium ion battery body 224 Metal terminal

Claims (7)

A packaging material for an electrochemical cell constituted by laminating at least a base material layer, a metal foil layer, and a thermal adhesive resin layer,
An adhesive layer on the outermost layer upper surface of the base material layer, and a cover film covering the adhesive layer,
A packaging material for an electrochemical cell, wherein an adhesive strength between the adhesive layer and the cover film is higher than an adhesive strength between the adhesive layer and the base material layer.   The packaging material for an electrochemical cell according to claim 1, wherein the cover film is subjected to an easy adhesion treatment on a joint surface with the adhesive layer.   The packaging material for an electrochemical cell according to claim 2, wherein the easy adhesion treatment is a corona treatment.   The packaging material for an electrochemical cell according to claim 2, wherein the easy adhesion treatment is an anchor coat treatment.   The packaging material for an electrochemical cell according to any one of claims 1 to 4, wherein the cover film is made of a polyethylene terephthalate film.   The packaging material for an electrochemical cell according to any one of claims 1 to 4, wherein the cover film is made of a nylon film.   An electrochemical cell produced using the packaging material for an electrochemical cell according to any one of claims 1 to 6.

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