JP5565178B2 - Packaging container for electrochemical cell - Google Patents

Description

  The present invention relates to a packaging container for an electrochemical cell, and more particularly, to a packaging container for an electrochemical cell which shows a certain safety performance by slow leaking gas generated inside under high temperature conditions.

  8 is a perspective view of a conventional lithium ion battery, and FIG. 9 is a cross-sectional view taken along the line C-C ′ of the lithium ion battery of FIG. 8. The lithium ion battery 221 is also referred to as a lithium secondary battery, and includes a liquid, gel-like, or polymer polymer electrolyte, and a cathode / negative electrode active material made of a polymer polymer. The configuration of the lithium ion battery 221 includes a lithium ion battery main body 222 composed of a positive electrode current collector / positive electrode active material layer / electrolyte layer / negative electrode active material layer / negative electrode current collector, and a packaging container 220 for housing these. The packaging container 220 is formed of a multilayer film. Specifically, the packaging container 220 includes a lid portion 220a and a storage portion 220b. The lithium ion battery main body 222 is stored inside the storage portion 220b, and the lid portion 220a and the storage portion 220b are connected to a current collector. The peripheral portion 220s is thermally bonded while the metal terminal 224 is sandwiched. The multilayer film constituting the packaging container 220 is configured by sequentially laminating a base material layer 211, a metal foil layer 212, and a thermal adhesive resin layer 215, and the opposing thermal adhesive resin layer 215 is thermally bonded at the peripheral portion 220s. doing.

  In general, it is assumed that the lithium ion battery 221 is used in various environments. For example, when the lithium ion battery 221 is placed in a high temperature environment or when the lithium ion battery 221 itself generates heat, In some cases, gas was generated inside the ion battery 221, the thermal adhesive resin layer 215 was melted, a part of the peripheral portion 220c was peeled off, and the lid portion 220a and the storage portion 220b were separated and opened. At this time, if the opening degree of the lid part 220a and the storage part 220b is large, the internal electrolyte leaks out, and there is a possibility that damage to the devices arranged around the lithium ion battery 221 increases.

  On the other hand, if the peripheral portion 220c is not melted even when the temperature reaches a certain temperature, the gas generated in the lithium ion battery 221 increases the internal pressure of the packaging container 220, which may cause the packaging container 220 to burst.

JP 2007-134304 A

  Therefore, in view of the above problems, an object of the present invention is to provide an electrochemical cell packaging container that slowly leaks gas generated inside under high temperature conditions and exhibits a certain safety performance.

  In order to achieve the above object, the first configuration of the present invention is such that a base material layer, a metal foil layer, a second thermal adhesive resin layer, and a first thermal adhesive resin layer are sequentially laminated. A packaging container for an electrochemical cell, which is formed by facing a first thermal adhesive resin layer of a multilayer film to be configured and thermally bonding a peripheral portion thereof, wherein the melting point of the second thermal adhesive resin layer is the first heat It has a point seal portion that is higher than the melting point of the adhesive resin layer and that is thermally bonded to the opposing second thermal adhesive resin layer at a part of the peripheral edge.

  According to this structure, in the peripheral part of the packaging container for electrochemical cells, in the area | region where 1st thermoadhesive resin layers adhere | attached, the area | region (point seal part) which 2nd thermoadhesive resin layers adhered together. Even when the first heat-adhesive resin layer is melted and peeled off in a high-temperature environment, the second heat-adhesive resin layer having a high melting point remains adhered and partially opens the opening of the packaging container for electrochemical cells. Can be stopped. In addition, the gas generated inside the electrochemical cell packaging container is gradually released from the melted portion of the first thermoadhesive resin layer to suppress an increase in the internal pressure of the electrochemical cell packaging container.

  According to a second configuration of the present invention, in the packaging container for electrochemical cells, a plurality of point seal portions are formed at a peripheral portion.

  According to this configuration, the seal strength at the peripheral portion can be adjusted by the arrangement and number of point seal portions at the peripheral portion.

  According to a third configuration of the present invention, in the above electrochemical cell packaging container, the second thermal adhesive resin layer is composed of an acid-modified polyolefin resin, and the first thermal adhesive resin layer is composed of a polyolefin resin. It is characterized by.

  According to this configuration, since the acid-modified polyolefin resin is excellent in adhesiveness with the metal foil layer, the metal foil layer and the second thermally adhesive resin layer can be stably bonded.

  The 4th structure of this invention is a manufacturing method of the packaging container for electrochemical cells, Comprising: A base material layer, a metal foil layer, a 2nd thermoadhesive resin layer, and a 1st thermoadhesive resin layer are , At least sequentially laminated, and the second heat-adhesive resin layer has a melting point higher than that of the first heat-adhesive resin layer, the first heat-adhesive resin layer of the multilayer film is opposed, and the peripheral portion is thermally bonded. It has a 1st process and the 2nd process of thermally bonding the 2nd thermoadhesive resin layer which opposes in a part of peripheral part.

  According to this configuration, a packaging container for an electrochemical cell is manufactured that has a point seal portion to which the second heat-adhesive resin layer facing the heat-adhered part of the peripheral edge portion to which the first heat-adhesive resin layer is heat-adhered. be able to.

  A fifth configuration of the present invention uses a heat seal bar in which a protrusion protruding in the pressing direction is formed on a part of the pressing surface in the second step of the method for manufacturing the packaging container for electrochemical cells, The projection is characterized in that the second heat-adhesive resin layer is extruded from the base material layer side by the protrusion and is thermally bonded to the opposing second heat-adhesive resin layer.

  According to this structure, the 2nd thermoadhesive resin layer which opposes easily can be heat-bonded.

  According to a sixth aspect of the present invention, in the method for manufacturing an electrochemical cell packaging container, the first step and the second step are performed simultaneously.

  According to this configuration, the point seal portion where the opposing second thermal adhesive resin layer insulating layer is bonded to a part of the peripheral portion of the electrochemical cell packaging container to which the opposing first thermal adhesive resin layer is thermally bonded is provided. It can be formed efficiently.

These are the perspective views of the lithium ion battery which used the packaging container for electrochemical cells which is an example of embodiment of this invention for the exterior body. These are sectional drawings of the multilayer film which comprises the packaging container for electrochemical cells. FIG. 2 is a plan view of the lithium ion battery of FIG. 1. FIG. 2 is a cross-sectional view taken along line A-A ′ of the lithium ion battery in FIG. 1. FIG. 2 is a cross-sectional view taken along line B-B ′ of the lithium ion battery in FIG. 1. FIG. 3 is a perspective view of a lithium ion battery. These are the fragmentary sectional views of the lithium ion battery in the 1st process. These are the fragmentary sectional views of the lithium ion battery in the 2nd process. These are the fragmentary sectional views of a lithium ion battery in the case of performing a 1st process and a 2nd process simultaneously. FIG. 3 is a perspective view of a conventional lithium ion battery. FIG. 9 is a cross-sectional view taken along line C-C ′ of the lithium ion battery in FIG. 8.

  The present invention is an electrochemical cell packaging container that exhibits a certain safety performance under high temperature conditions, and will be described in more detail with reference to the drawings. Note that description of portions common to those in FIGS. 8 and 9 of the conventional example is omitted.

  FIG. 1 is a perspective view of a lithium ion battery using an electrochemical cell packaging container as an example of an embodiment of the present invention as an exterior body, and FIG. 2 is a cross-sectional view of a multilayer film constituting the electrochemical cell packaging container 3 is a plan view of the lithium ion battery of FIG. 1, FIG. 4 is a cross-sectional view taken along the line AA ′ of the lithium ion battery of FIG. 1, and FIG. FIG. As shown in these drawings, the electrochemical cell packaging container (hereinafter abbreviated as packaging container 120) is composed of a lid part 120a and a storage part 120b, and a lithium ion battery main body 122 is stored inside the storage part 120b. Then, while holding the metal terminal 124 between the lid part 120a and the storage part 120b, the peripheral part 120s including the holding part is thermally bonded to manufacture the lithium ion battery 121.

  At this time, the multilayer film 110 constituting the packaging container 120 is formed by sequentially laminating the base material layer 111, the metal foil layer 112, the second thermal adhesive resin layer 115a, and the first thermal adhesive resin layer 115b. The thermal adhesive resin layer 115a is made of a resin having a higher melting point than the first thermal adhesive resin layer 115b. In addition, the multilayer film 110 which comprises the packaging container 120 of this invention includes the said each layer, and also includes the case where a different layer is interposed between each layer in the technical scope of this invention. In the peripheral portion 120s, the first heat-adhesive resin layers 115b facing each other are thermally bonded to each other, and the point seal portions P are formed on the peripheral portion 120s at substantially equal intervals. The adhesive resin layers 115a are thermally bonded.

  FIG. 5 shows a cross-sectional structure of the point seal portion P. In the point seal portion P, a part of the second heat-adhesive resin layer 115a pushes away the first heat-adhesive resin layer 115b and the second heat-adhesive resin layer 115 is opposed. It is thermally bonded to the conductive resin layer 115a. Thereby, even when the first heat-adhesive resin layer 115b in the peripheral portion 120s melts and peels in a high-temperature environment, the second heat-adhesive resin layer 115a having a high melting point is adhered in the point seal portion P. The opening of the packaging container 120 can be partially retained. Further, the gas generated inside the packaging container 120 is gradually released to the outside from the portion where the first thermal adhesive resin layer 115b is melted, and an increase in the internal pressure of the packaging container 120 can be suppressed.

  Here, the point seal portion P may be provided at a plurality of locations in the peripheral portion 120s, but even if only one location is provided, the object of the present invention can be achieved. Further, by providing the point seal portions P at substantially equal intervals, the adhesive force of the entire peripheral portion 120s can be stabilized. In addition, the slow leak of the gas can be controlled by the arrangement configuration of the point seal portion P.

  Next, the manufacturing method of the packaging container 120 which concerns on this invention is demonstrated. FIG. 6 is a perspective view of the lithium ion battery, FIG. 7A is a partial sectional view of the lithium ion battery in the first step, and FIG. 7B is a partial sectional view of the lithium ion battery in the second step. FIG. 7C is a partial cross-sectional view of the lithium ion battery when the first step and the second step are performed simultaneously. In addition, the arrow in a figure shows a pressing direction. As shown in FIGS. 6 and 7 (a), the packaging container 120 is overlapped with the storage portion 120b press-formed in a concave shape and the first thermal adhesive resin layer 115b of the film-like lid portion 120a facing each other. In the first step, the peripheral portion 120s is heated from the base material layer 111 side while being sandwiched by the pressing surface 140a of the first heat seal bar 140. Thereby, the 1st thermoadhesive resin layer 115b which opposes is heat-bonded. Next, as shown in FIG. 7B, in the second step, a part of the peripheral portion 120 s is sandwiched by using the protruding second heat seal bar 150 having a narrower seal width than the first heat seal bar 140. While pressing the second thermal adhesive resin layer 115a from the base material layer 111 side, the second thermal adhesive resin layer 115 is pushed out in the pressing direction while retracting the first thermal adhesive resin layer 115b. Thereby, the 2nd thermoadhesive resin layer 115a which opposes is heat-bonded, and the point seal | sticker part P is formed. Through these steps, the lithium ion battery main body 122 can be hermetically housed inside the packaging container 120 while providing the point seal portion P in a part of the peripheral portion 120s.

  In addition, as shown in FIG.7 (c), by forming the protrusion part 141 which protrudes toward a pressing direction in a part of pressing surface 140a of the 1st heat seal bar 140 used for a 1st process, the pressing surface 140a. Then, the first step is performed, and the second step is performed on the protrusion 141, so that the first step and the second step can be performed simultaneously by one press heating step. Thereby, the point seal | sticker part P can be efficiently formed in a part of peripheral part 120s which the 1st thermoadhesive resin layer 115b which opposes thermally bonded. In the above description, the method of thermally bonding only one side of the peripheral portion 120s has been described. However, a heat seal bar is produced according to the shape of the peripheral portion 120s to be thermally bonded, and all sides are thermally bonded at once. It is also possible to do.

  Next, each layer constituting the multilayer film 110 will be described. The second thermal adhesive resin layer 115a is made of a resin having a melting point higher than that of the first thermal adhesive resin layer 115b. In order to stably bond the aluminum foil layer 112 and the first thermal adhesive resin layer 115b. Acid-modified polypropylene is preferably used. In addition, it is necessary to appropriately select and use the resin type used for the first heat-adhesive resin layer 115b. When an acid-modified polyolefin resin other than acid-modified polypropylene is used, a polyolefin resin graft-modified with an unsaturated carboxylic acid, ethylene or There are copolymers of propylene and acrylic acid or methacrylic acid, or metal cross-linked polyolefin resins, butene components, ethylene-propylene-butene copolymers, amorphous ethylene-propylene copolymers as required A blend, 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.

  Polypropylene is suitably used for the first thermal adhesive resin layer 115b, but polyolefin having thermal adhesiveness can be used in addition to polypropylene. 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 metal 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, when the generation of pinholes is improved and the type of the outer package of the lithium ion battery is an embossed type, the material of aluminum used as the metal 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, but the aluminum used in the present invention is harder than the non-annealed hard-treated product. Aluminum which tends to be soft with some or complete annealing is preferred.

  Stretched polyester or nylon film can be used for the base material layer 111, and examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymer polyester, and polycarbonate. 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, the base material layer 111 can be laminated with films of different materials in addition to a polyester film or a nylon film in order to improve pinhole resistance and insulation when used as a battery outer package.

  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, 210 Multilayer film 111, 211 Base material layer 112, 212 Metal foil layer 115a First thermal adhesive resin layer 115b Second thermal adhesive resin layer 120, 220 Packaging container for electrochemical cell (packaging container)
120s, 220s Peripheral part 120a Lid part 120b Storage part 121, 221 Lithium ion battery 122, 222 Lithium ion battery main body 124, 224 Metal terminal 140 First heat seal bar 140a Press surface 141 Protrusion part 150 Second heat seal bar

Claims (3)

A base material layer, a metal foil layer, a second heat-adhesive resin layer, and a first heat-adhesive resin layer are at least sequentially laminated, and the melting point of the second heat-adhesive resin layer is the first A first step in which the first thermal adhesive resin layer of the multilayer film having a melting point higher than that of the first thermal adhesive resin layer is opposed to the peripheral portion and thermally bonded;
A second step of thermally bonding the opposing second thermal adhesive resin layer in a part of the peripheral edge;
The manufacturing method of the packaging container for electrochemical cells characterized by having. In the second step, using a heat seal bar in which a protrusion protruding in the pressing direction is formed on a part of the pressing surface, the second heat-adhesive resin layer is formed from the base material layer side by the protrusion. The method for producing a packaging container for an electrochemical cell according to claim 1, wherein the second thermoadhesive resin layer is extruded and opposed to the second heat-adhesive resin layer. The method for producing a packaging container for an electrochemical cell according to claim 2, wherein the first step and the second step are performed simultaneously.

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