JP2010086744A - Packing material for battery outer package - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packing material for an electro-chemical cell, applicable to an outer package for housing airtightly an electro-chemical cell body such as a lithium ion battery body, a capacitor and an electric double layered capacitor, and excellent in heat resistance, electrolyte solution resistance, anti-gas permeability and moldability. <P>SOLUTION: The packing material for the electro-chemical cell applicable to the outer package for housing airtightly by heat-sealing an peripheral part an electro-chemical cell body containing a cathode made of an cathode active material and a cathode collector, an anode made of an anode active material and an anode collector, and electrolyte filled between the cathode and the anode is formed and composed of at least a base material layer, a metal foil layer with a chemical-treated surface, an acid-denaturated polyolefin layer and a thermal adhesive resin layer, laminated in order. The acid-denaturated polyolefin layer is formed of an acid-denaturated polypropylene of a melting point 145-165°C and the thermal adhesive resin layer is formed of polypropylene. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a packaging material for battery chemical cells that exhibits stable heat resistance, electrolytic solution resistance, gas permeability resistance, and moldability.

  As electronic devices have become smaller, lighter, thinner, and portable, mobile information devices such as mobile phones and notebook computers have become popular in recent years. Accordingly, batteries used as power sources for these electronic devices are required to be smaller, lighter, thinner, and have higher performance.

  A high energy density secondary battery is suitable as a battery for electronic equipment. For this reason, the development of electrode active materials that have a large discharge capacity per unit weight and unit volume and enable a high voltage has been promoted, and non-aqueous electrolyte batteries such as lithium ion secondary batteries using non-aqueous electrolytes have been put to practical use. Has been done. In high-performance secondary batteries such as lithium ion secondary batteries, metal lithium or a material having the same potential is used for charging and discharging, so an aqueous electrolyte cannot be used. For example, a lithium salt is dissolved in an organic solvent. Nonaqueous electrolytes such as organic electrolytes are used. Such a high-performance secondary battery using a non-aqueous electrolyte is called a non-aqueous electrolyte battery.

  A typical lithium ion secondary battery as a nonaqueous electrolyte battery includes a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte, and generates a current by movement of lithium ions. The positive electrode and the negative electrode generally have a structure in which an active material layer is formed on a metal substrate such as a metal foil or expanded metal called a current collector.

  As the positive electrode, a layer made of a positive electrode active material such as a polymer positive electrode material such as metal oxide, carbon black, metal sulfide, polyacrylonitrile, etc. is formed on a positive electrode current collector formed of aluminum, nickel, or the like. Is used. As a negative electrode, a negative electrode current collector formed of copper, nickel, stainless steel, or the like, and a layer made of a negative electrode active material such as a polymer negative electrode material such as lithium metal, lithium alloy, carbon black, or polyacrylonitrile is formed. Is used.

  As a separator material, a polyethylene microporous film is mainly used in a lithium ion secondary battery using an organic electrolyte. For polymer batteries, gelled sheets obtained by impregnating polyvinylidene fluoride, polyethylene oxide, polyacrylate, polyacrylonitrile, or the like with an electrolytic solution are used. As the nonaqueous electrolyte, carbonate-based electrolytes such as propylene carbonate, ethylene carbonate, dimethyl carbonate, and diethyl carbonate; inorganic solid electrolytes composed of lithium salts; gel electrolytes, and the like are used.

  Nonaqueous electrolyte batteries are used as power sources for personal computers, mobile terminal devices (for example, mobile phones and PDAs), video cameras, electric vehicles, energy storage batteries, robots, and satellites.

  A nonaqueous electrolyte battery is a battery in which a positive electrode, a negative electrode, a separator, and a nonaqueous electrolyte are sealed in an outer package. Conventionally, as an exterior body, a metal can formed by pressing a metal into a cylindrical or rectangular parallelepiped container has been used. However, metal cans are limited in size, weight, and thickness, and because the outer wall of the container is rigid, the degree of freedom of the battery shape is small, and as a result, the shape of the electronic device that houses the battery is free. In recent years, multilayer films tend to be used as packaging materials in place of metal cans.

  4 is a cross-sectional view showing a layer structure of a conventional packaging material 30. As shown in FIG. 4, the conventional packaging material 30 includes at least a base material layer 31, a metal foil layer 32, and a thermal adhesive resin layer 35. The chemical conversion treatment layer 33 is formed on the surface of the metal foil layer 32, and the metal foil layer 32 and the heat-adhesive resin layer 35 are bonded by an acid-modified polyolefin layer 34. Further, the base material layer 31 and the metal foil layer 32 are bonded by an adhesive layer 37. Also, there is a pouch type in which the packaging material 30 is formed in a bag shape and the battery body is accommodated, or an embossed type battery exterior body in which the packaging material 30 is pressed to form a recess and the battery body is accommodated in the recess. It is formed.

  FIG. 5 is a perspective view of a conventional pouch-type lithium ion battery 41, and FIG. 6 is an exploded perspective view showing the pouch-type lithium ion battery 41 shown in FIG. 5 in an exploded manner. As shown in FIGS. 5 and 6, the pouch-type lithium ion battery 41 has the innermost heat-adhesive resin layer 35 (see FIG. 4) overlapped with each other, and a heat seal portion 40 a that is a peripheral portion of the exterior body 40. The pouch-type exterior body 40 is formed by heat sealing, the lithium ion battery main body 42 is accommodated in the exterior body 40, the opening is heat sealed, and the lithium ion battery main body 42 is hermetically stored.

  FIG. 7 is a perspective view of a conventional embossed lithium ion battery 51, and FIG. 8 is an exploded perspective view of the embossed lithium ion battery 51 shown in FIG. As shown in FIGS. 7 and 8, the embossed type lithium ion battery 51 accommodates a lithium ion battery main body 52 inside a tray 50t in which an embossed portion is formed, and the thermoadhesive resin layer 35 between the tray 50t and the sheet 50s. (Refer to FIG. 4). The heat seal part 50a, which is the peripheral part of the outer package 50, is overlapped with each other and heat-sealed, so that the lithium ion battery main body 52 is placed inside the embossed outer package 50 composed of the tray 50t and the sheet 50s. Store sealed.

  The lithium ion battery bodies 42 and 52 include a positive electrode made of a positive electrode active material and a positive electrode current collector, a negative electrode made of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode (both A cell (power storage unit) including a cell (not shown), and metal terminals 44 and 54 that are connected to a positive electrode and a negative electrode in the cell and protrude from the exterior bodies 40 and 50 to the outside.

  9 is a perspective view of a conventional embossed lithium ion battery 61, and FIG. 10 is a cross-sectional view of the lithium ion battery 61 taken along the line B-B '. As shown in FIG. 10, the outer package 60 is bonded to the outer peripheral portion (heat seal portion 60 a) by superposing the innermost thermoadhesive resin layers 35 and heat-sealing the peripheral portion of the outer package 60. The lithium ion battery main body 62 is hermetically housed in the first region 60b other than the heat seal. However, in the first region 60 b, the lithium ion battery main body 62 generates heat due to long-term use or rapid charging of the lithium ion battery 61, and one of the thermoadhesive resin layers 35 disposed in the innermost layer of the exterior body 60. The part may melt. At this time, there has been a problem that the electrolyte filled in the exterior body 60 penetrates into the metal foil layer 32 from a part of the molten heat-adhesive resin layer 35 and the lithium ion battery 61 generates a short circuit.

On the other hand, when a resin having excellent heat resistance is used for the heat-adhesive resin layer 35 so that the heat-adhesive resin layer 35 is not easily melted, it is necessary to set a high temperature during heat sealing. There was a problem that the production efficiency was lowered. Therefore, in order to solve these problems, conventionally, an insulating resin layer made of 4-methyl-1-pentene resin having excellent heat resistance is interposed between the thermal adhesive resin layer 35 and the metal foil layer 32. Thus, even when the lithium ion battery main body 62 generates heat and a part of the heat-adhesive resin layer 35 disposed on the innermost layer of the outer package 60 is melted, the insulating resin layer is not melted and the outer package 60 is melted. There has been proposed a packaging material that prevents the lithium ion battery 61 from being short-circuited by penetrating the metal foil layer 32 from a part of the thermoplastic resin layer 35 in which the electrolyte filled therein is melted. (For example, Patent Document 1)
JP 2002-151023 A

  However, in a packaging material in which an insulating resin layer made of 4-methyl-1-pentene resin is interposed between the thermal adhesive resin layer 35 and the metal foil layer 32, 4-methyl-1-pentene resin is used. Is low in adhesiveness with polyolefin resin mainly used as a metal foil layer and a heat-adhesive resin layer. Therefore, an insulating resin layer made of 4-methyl-1-pentene resin is used as a metal with a heat-adhesive resin layer 35 and a metal. When interposed between the foil layer 32 and the adhesive layer, it is necessary to provide an adhesive comprising a polyolefin polyol and an isocyanate curing agent as an adhesive layer. In this case, the newly provided adhesive layer has a water vapor gas barrier property and electrolysis resistance. Since the liquidity is inferior, there has been a problem that it is impossible to impart stable water vapor gas barrier properties and electrolytic solution resistance to the entire packaging material. Further, when an insulating resin layer made of 4-methyl-1-pentene resin is interposed between the thermal adhesive resin layer 35 and the metal foil layer 32, the packaging material is press-molded to form a tray. The metal foil layer 32 and the insulating resin layer are different in stretchability, and the insulating resin layer does not have sufficient followability. Therefore, the metal foil layer 32 and the insulating resin layer cannot be molded to a predetermined depth, or the ridge and corners after molding are sharply formed. In some cases, this is not easy to occur, and the moldability deteriorates.

  In addition to the case where the lithium ion battery main body 42, 52, 62 is accommodated in the outer body 40, 50, 60, the same applies to the case where an electrochemical cell main body such as a capacitor or an electric double layer capacitor is accommodated and hermetically sealed. There was a problem.

  Therefore, in view of the above problems, the present invention is used in an exterior body for hermetically storing an electrochemical cell body such as a lithium ion battery body, a capacitor, and an electric double layer capacitor, and has heat resistance, electrolyte resistance, water vapor gas barrier property, It aims at providing the packaging material for electrochemical cells which is excellent in a moldability.

  In order to solve the above problems, in the packaging material for an electrochemical cell according to claim 1, a positive electrode comprising a positive electrode active material and a positive electrode current collector, a negative electrode comprising a negative electrode active material and a negative electrode current collector, the positive electrode and the positive electrode And an electrolyte filled between the negative electrodes, and is used in an exterior body that houses the electrochemical cell body in a sealed manner by heat-sealing the peripheral portion, and a base material layer on the surface. A packaging material for an electrochemical cell comprising a metal foil layer subjected to a chemical conversion treatment, an acid-modified polyolefin layer, and a heat-adhesive resin layer, which are sequentially laminated, wherein the acid-modified polyolefin layer has a melting point. Is made of acid-modified polypropylene having a temperature of 145 ° C. to 165 ° C., and the heat-adhesive resin layer is made of polypropylene. By comprising in this way, the acid-modified polyolefin which consists of acid-modified polypropylene whose melting | fusing point is 145 to 165 degreeC between the metal foil layer by which the chemical conversion treatment was performed on the surface, and the heat-adhesive resin layer which consists of polypropylene Because the layer is interposed, the heat-resistant acid-modified polyolefin layer may melt even when the electrochemical cell body containing the electrolyte generates heat inside the outer package and the innermost thermoadhesive resin layer melts. It is possible to prevent the metal foil layer from being exposed. For this reason, the heat-resistant acid-modified polyolefin resin layer blocks the electrolyte that is about to penetrate into the metal foil layer from a part of the molten heat-adhesive resin layer, and the electric current caused by the contact between the electrolyte and the metal foil layer Short circuit of the chemical cell can be prevented. Therefore, the packaging material for electrochemical cells of this configuration has excellent heat resistance, and the exterior body made using the packaging material for electrochemical cells of this configuration has excellent insulation against the heat generation inside the exterior body. Have

Moreover, compared with the case where a heat resistant resin film is interposed as an intermediate | middle layer like the past, it has little influence on the adhesiveness of a metal foil layer and a heat bondable resin layer. For this reason, the packaging material for electrochemical cells of this configuration can prevent the press formability from decreasing.
As described above, according to the present invention, an acid-modified polyolefin layer having high heat resistance is interposed between the metal foil layer subjected to chemical conversion treatment on the surface and the heat-adhesive resin layer. It is possible to provide a packaging material for an electrochemical cell excellent in liquidity, water vapor gas barrier property, and moldability.

  The present invention is an electrochemical packaging material excellent in heat resistance, gas permeability resistance and moldability. Below, the packaging material for electrochemical cells of this invention is demonstrated in detail using drawing.

FIG. 1 is a cross-sectional view showing a part of the layer structure of a packaging material 10 for an electrochemical cell according to the present invention, and the material of each layer constituting the packaging material 10 for an electrochemical cell of the present invention will be described with reference to FIG. To do. The packaging material 10 for an electrochemical cell of the present invention has a base material layer 11 as an outermost layer, a heat-adhesive resin layer 15 as an innermost layer, and a metal foil layer 12 disposed therebetween. The metal foil layer 12 is bonded via the acid-modified polyolefin layer 14. Moreover, the base material layer 11 and the metal foil layer 12 are bonded via an adhesive layer 17. In addition, the packaging material 10 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.
2 shows a lithium ion battery 21 in which a lithium ion battery main body 22 (not shown in FIG. 2) is housed in a pouch-type outer package 20 formed using the packaging material 10 for electrochemical cells of the present invention. FIG. 3 is a perspective view, and FIG. 3 is a cross-sectional view taken along line AA ′ of the lithium ion battery 21 in FIG. 2. As shown in FIGS. 2 and 3, the outer body 20 is in a state where the metal terminal 24 is sandwiched, and the peripheral portion including the sandwiched portion is heat-sealed (hereinafter, the heat-sealed portion is referred to as a heat-sealed portion 20 a). The lithium ion battery main body 22 containing the electrolyte is hermetically housed inside the outer package 20.

  Next, each layer which comprises the packaging material 10 for electrochemical cells which concerns on this invention shown in FIG. 1 is demonstrated concretely. The innermost heat-adhesive resin layer 15 is opposed to the lithium-ion battery by sandwiching the metal terminal 24 (see FIG. 2) of the lithium-ion battery main body 22 in a protruding state and thermally bonding at the peripheral edge. The main body 22 is sealed. Although not shown, a metal terminal sealing adhesive film having metal adhesion is interposed between the thermal adhesive resin layer 15 and the metal terminal 24. As an adhesive film for sealing metal terminals, a film having a three-layer structure in which polyethylene terephthalate or polyethylene naphthalate having excellent heat resistance and water vapor gas barrier properties is used for the intermediate layer, and acid-modified polyolefin layers are laminated on the front and back surfaces is used. can do.

  Note that polypropylene is used as the heat-adhesive resin layer 15 from the viewpoint of heat resistance. Polypropylene can be divided into random propylene, homopropylene, block propylene, and other types.

  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.

  Further, the heat-adhesive resin layer 15 according to the present invention may be multilayered by combining the above-mentioned types of polypropylene layers as appropriate.

Next, the acid-modified polyolefin layer 14 will be described. The acid-modified polyolefin layer 14 is a layer provided for bonding the metal foil layer 12 and the heat-adhesive resin layer 15 made of polypropylene, and the heat-adhesive resin layer 15 made of polypropylene and the acid-modified polypropylene having excellent adhesiveness are used. Polypropylene that is used and graft-modified with unsaturated carboxylic acid, a copolymer of propylene and acrylic acid, or methacrylic acid, and the like, butene component, ethylene-propylene-butene copolymer, propylene-α as necessary -An olefin copolymer etc. may be added 5% or more. As the acid-modified polyolefin layer, an acid-modified polypropylene having a melting point of 145 ° C. to 165 ° C. is used. If the melting point is less than 145 ° C., the electrochemical cell body containing the electrolyte generates heat inside the outer package, and the innermost layer polypropylene. When the heat-adhesive resin layer made of is melted, the acid-modified polyolefin layer is also melted, and when the melting point exceeds 165 ° C., the melt tension at the time of melt extrusion is small, resulting in poor thermal stability and molecular cutting. There are problems such as easy surging, large neck-in, and the like, and there is a possibility that hot melt extrusion becomes difficult and film formation at a predetermined thickness is not preferable.

  In addition, the heat-adhesive resin layer made of polypropylene and the acid-modified polyolefin made of acid-modified polypropylene prevent fine cracks from occurring in the cold forming process, heat sealing process, and bending process after heat sealing. Therefore, a low crystalline ethylene-butene copolymer having a density of 900 kg / m 3 or less, a low crystalline propylene-butene copolymer, an amorphous ethylene-propylene copolymer, or an amorphous propylene-ethylene A copolymer, an ethylene-butene-propylene copolymer (terpolymer), or the like can be added.

  Next, the base material layer 11 will be described. The base material layer 11 is generally made of stretched polyester or nylon film. At this time, examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized 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 11 can be laminated with films of different materials in addition to a polyester film or nylon film in order to improve pinhole resistance and insulation when used as a battery outer package. When making the base material layer 11 into a laminated body, a base material layer contains at least 1 resin layer of 2 or more layers, and the thickness of each layer is 6 micrometers or more, Preferably, it is 6-25 micrometers. Examples of laminating the base material layer include the following 1) to 7) although not shown.
1) Stretched polyethylene terephthalate / stretched nylon 2) Stretched nylon / stretched polyethylene terephthalate 3) Fluorine resin / stretched polyethylene terephthalate (Fluorine resin is formed into a film or dried after liquid coating)
4) Silicone resin / stretched polyethylene terephthalate (silicone resin is a film or formed by drying after liquid coating)
5) Fluorine-based resin / stretched polyethylene terephthalate / stretched nylon 6) Silicone-based resin / stretched polyethylene terephthalate / stretched nylon 7) Acrylic resin / stretched nylon (Acrylic resin is cured in a film or liquid coating and dried)

  As shown in 3) to 7), mechanical suitability of packaging materials (stability of conveyance in packaging machines and processing machines), surface protection (heat resistance and electrolyte resistance), secondary processing In order to protect the base material layer 11 when reducing the frictional resistance between the mold and the base material layer 11 at the time of embossing or when an electrolytic solution adheres when the exterior body 20 for a lithium ion battery is made an embossed type. In addition, the base material layer 11 is multilayered, and a protective layer such as a fluorine resin layer, an acrylic resin layer, a silicone resin layer, a polyester resin layer, and a blend layer thereof on the surface of the base material layer (in FIG. 1, (Not shown) is preferably provided.

  The same effect can be obtained when stretched polybutylene terephthalate or polyethylene naphthalate is used in place of the stretched polyethylene terephthalate. The base material layer 11 is bonded to the metal foil layer 12 via the adhesive layer 17 by a dry lamination method or the like.

  Next, the metal foil layer 12 will be described. The metal foil layer 12 is a layer for preventing water vapor from entering the inside of the lithium ion battery from the outside, and stabilizes pinholes and processability (pouching, embossing formability) of the metal foil layer alone, In addition, in order to provide pinhole resistance, a metal such as aluminum or nickel having a thickness of 15 μm or more, or a film on which an inorganic compound such as silicon oxide or alumina is vapor-deposited may be mentioned. The aluminum has a thickness of 20 to 80 μm.

  Moreover, in order to improve the generation of pinholes and to make the outer body type of the lithium ion battery an embossed type, the material of aluminum used as the metal foil layer 12 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. 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.

  That is, the annealing conditions may be appropriately selected in accordance with processability (pouching, embossing). For example, in order to prevent wrinkles and pinholes during emboss molding, soft aluminum annealed according to the degree of molding can be used.

  Moreover, by performing a chemical conversion treatment on the front and back surfaces of the aluminum that is the metal foil layer 12 to form the chemical conversion treatment layer 13, the adhesive strength with the adhesive can be improved.

  Next, the chemical conversion treatment layer 13 will be described. As shown in FIG. 1, the chemical conversion treatment layer 13 is formed on at least the surface of the metal foil layer 12 on the heat-adhesive resin layer 15 side. The chemical conversion treatment layer 13 can stably adhere the acid-modified polyolefin layer 14 and the metal foil layer 12 and prevent delamination of the metal foil layer 12 and the heat-adhesive resin layer 15. The chemical conversion treatment layer 13 also has a function of preventing the metal foil layer 12 from being corroded.

  Specifically, delamination between the metal foil layer 12 and the heat-adhesive resin layer 15 during embossing by forming an acid-resistant film such as phosphate, chromate, fluoride, triazine thiol compound, etc. And hydrogen fluoride produced by the reaction between the electrolyte and water in the lithium ion battery prevents the aluminum surface from being dissolved and corroded, especially the aluminum oxide present on the aluminum surface from being dissolved and corroded. Surface adhesion (wetting) can be improved.

  The chemical conversion treatment layer 13 is made of a metal by chromium conversion treatment such as chromate chromate treatment, phosphoric acid chromate treatment, coating chromate treatment, or non-chromium (coating type) chemical conversion treatment such as zirconium, titanium, and zinc phosphate. Although it is formed on the surface of the foil layer 12, it is firmly bonded to the fluororesin, the point that it can be continuously processed and the water washing step is unnecessary, and the processing cost can be reduced. It is most preferable to treat with a treatment solution containing a coating type chemical conversion treatment, particularly an aminated phenol polymer, a trivalent chromium compound, and a phosphorus compound.

  Moreover, as a formation method of the chemical conversion treatment layer 13, what is necessary is just to select and shape | mold a process liquid, selecting well-known coating methods, such as a barcode method, a roll coat method, a gravure coat method, and an immersion method. Moreover, before forming the chemical conversion treatment layer 13, the surface of the metal foil layer 12 is previously treated by a known degreasing treatment method such as an alkali dipping method, an electrolytic washing method, an acid washing method, an acid activation method, or the like. However, it is preferable because the function of the chemical conversion treatment layer 13 can be expressed to the maximum and can be maintained for a long time.

  In addition, for each of the above layers, corona treatment, blast treatment, and oxidation treatment are appropriately performed for the purpose of improving and stabilizing film forming properties, lamination processing, and final product secondary processing (pouching, embossing). Surface activation treatment such as ozone treatment may be performed.

  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.

  Hereinafter, the operation and effect of the present invention will be specifically described with reference to examples. Example 1 evaluated the heat resistance and insulation in a packaging material for an electrochemical cell in which an acid-modified polyolefin layer made of acid-modified polypropylene having a melting point of 150 ° C. was laminated between a metal foil layer and a heat-adhesive resin layer. Is.

  The manufacturing method of the packaging material for electrochemical cells used in the present example is as follows. First, one surface of aluminum is subjected to chemical conversion treatment, and a stretched nylon film is applied to the surface not subjected to chemical conversion treatment with a two-component curable polyurethane adhesive. And bonded together by a dry laminating method. Next, an acid-modified polypropylene (hereinafter abbreviated as acid-modified PP) shown below is melt-extruded on the surface subjected to chemical conversion treatment, and a polypropylene film (hereinafter abbreviated as PP film, thickness 23 μm) is laminated by a sandwich lamination method. 1 packaging material for an electrochemical cell was obtained.

In this example, the base layer is made of stretched nylon film (thickness 25 μm), the metal foil layer is made of aluminum (thickness 40 μm), and the chemical conversion treatment is a treatment comprising a phenol resin, a chromium fluoride compound, and phosphoric acid. The liquid was applied to the aluminum surface by a roll coating method, and baked under the condition that the film temperature was 90 ° C. or higher. Here, the coating amount of chromium was 10 mg / m ² (dry weight), and the acid-modified PP was laminated by a melt extrusion method so as to be 30 μm.

Next, in place of the acid-modified polypropylene of Example 1 above, the same procedure as in Example 1 was conducted except that acid-modified polypropylene having the following melting points was 30 μm by the melt extrusion method. Examples 2 to 5 and Comparative Examples 1 and 2 The electrochemical cell packaging material was obtained.

Next, a positive electrode terminal is set on a nickel tab, a negative electrode terminal is set on aluminum constituting the packaging material for electrochemical cells, a voltage of 25 V is applied, and the seal temperature is 7 mm wide including a portion sandwiching the nickel tab. Sealing was performed at 170 ° C. and a sealing pressure of 0.5 MPa, and the time during which the resistance value was 1000 MΩ or less (hereinafter referred to as dielectric breakdown time) was measured. In this evaluation method, two samples each of Examples 1 to 4, Comparative Example 1, and Comparative Example 2 were prepared, and each evaluation was performed by the above evaluation method as a packaging material for an electrochemical cell. The results are shown in Table 1.

Next, the positive electrode terminal is set on the nickel tab, the negative electrode terminal is set on the aluminum constituting the packaging material for electrochemical cells, and the time when the voltage is 25 V and the resistance value is 1000 MΩ or less (hereinafter referred to as dielectric breakdown time and Measured). In this evaluation method, two samples each of Comparative Example 1 and Inventions 1 and 2 were prepared, and each evaluation was performed by the above evaluation method as a packaging material for an electrochemical cell. The results are shown in Table 1.

  As shown in Table 2, the packaging material for electrochemical cells according to Examples 1 to 4 using acid-modified polypropylene having a melting point of 145 ° C. to 165 ° C. as the acid-modified polyolefin layer uses acid-modified polypropylene having a melting point of 140 ° C. It was found that the insulating material was superior in insulation property as compared with the packaging material for electrochemical cells according to Comparative Example 1 and Comparative Example 2 using acid-modified polypropylene having a melting point of 120 ° C.

  From this, it is thought that the exterior body produced using the packaging material for electrochemical cells using the acid-modified polypropylene having a melting point of 145 ° C. to 165 ° C. as the acid-modified polyolefin layer is excellent in heat resistance.

Sectional drawing which shows the layer structure of the packaging material for electrochemical cells of this invention The perspective view of the lithium ion battery which used the packaging material for electrochemical cells of this invention for the exterior body Sectional drawing in A-A 'of the lithium ion battery shown in FIG. Sectional drawing which shows the layer structure of the conventional packaging material for electrochemical cells A perspective view of a lithium ion battery using a conventional packaging material for electrochemical cells as an exterior body FIG. 5 is an exploded perspective view of the lithium ion battery shown in FIG. A perspective view of a lithium ion battery using a conventional packaging material for electrochemical cells as an exterior body FIG. 7 is an exploded perspective view of the lithium ion battery shown in FIG. A perspective view of a lithium ion battery using a conventional packaging material for electrochemical cells as an exterior body Sectional drawing in B-B 'of the lithium ion battery shown in FIG.

Explanation of symbols

10, 30 Electrochemical cell packaging material 11, 31 Base layer 12, 32 Metal foil layer 13, 33 Chemical conversion layer 14, 34 Acid-modified polyolefin layer 15, 35 Thermal adhesive resin layer 17, 37 Adhesive layer 20, 40, 50, 60 Exterior body 20a, 40a, 50a, 60a Heat seal portion 20b, 60b First region 20c Second region 21, 41, 51, 61 Lithium ion battery 22, 42, 52, 62 Lithium ion battery body 24, 44, 54, 64 Metal terminal (tab)

Claims (1)

A peripheral portion containing an electrochemical cell body including a positive electrode made of a positive electrode active material and a positive electrode current collector, a negative electrode made of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode Is used for an exterior body that hermetically seals and stores the electrochemical cell body therein, a base material layer, a metal foil layer subjected to chemical conversion treatment on the surface, an acid-modified polyolefin layer, and thermal adhesiveness A packaging material for an electrochemical cell constituted by laminating at least a resin layer sequentially,
The packaging material for an electrochemical cell, wherein the acid-modified polyolefin layer is formed of an acid-modified polypropylene having a melting point of 145 ° C to 165 ° C, and the thermal adhesive resin layer is formed of polypropylene. .

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