JP5668785B2 - Battery packaging materials - Google Patents

Description

  The present invention relates to a battery packaging material exhibiting stable sealing properties, insulating properties, and moldability.

The lithium ion battery is also referred to as a lithium secondary battery, and includes a battery having a liquid, gel-like, and polymer-like electrolyte, and a positive electrode / negative electrode active material made of a polymer. In this lithium ion battery, the lithium atom (Li) in the lithium transition metal oxide, which is the positive electrode active material, is charged as lithium ion (Li ⁺ ) during charging and enters the carbon layer of the negative electrode (intercalation). This is a battery in which charge / discharge reaction proceeds when ions (Li ⁺ ) are separated from the carbon layer (deintercalation) and move to the positive electrode to become the original lithium compound. From the nickel-cadmium battery and the nickel-hydrogen battery The output voltage is high, the energy density is high, and the apparent discharge capacity is reduced by repeating shallow discharge and recharging, so that there is no so-called memory effect. Therefore, in recent years, it has been widely used as a power source for portable devices such as mobile phones, notebook computers, digital cameras, and small video cameras.

  The composition of the lithium ion battery is as follows: positive electrode current collector (aluminum, nickel) / positive electrode active material layer (polymeric positive electrode material such as metal oxide, carbon black, metal sulfide, electrolyte, polyacrylonitrile) / electrolyte layer (propylene carbonate) , Carbonate electrolytes such as ethylene carbonate, dimethyl carbonate, ethylene methyl carbonate, inorganic solid electrolytes composed of lithium salts, gel electrolytes, etc.) / Anode active material layers (lithium metals, alloys, carbon, electrolytes, polyacrylonitrile, etc.) Molecular negative electrode material) / negative electrode current collector (copper, nickel, stainless steel) and an outer package for packaging them. As the exterior body, conventionally, a metal can obtained by pressing a metal into a cylindrical shape or a rectangular parallelepiped shape has been used.

  However, in the conventional metal can, since the outer wall of the container is rigid, the shape of the battery itself is determined. For this reason, since the hardware side is designed in accordance with the battery, the size of the hardware using the battery is determined by the battery, and there is no degree of freedom in shape.

  Therefore, in recent years, there is a tendency to use an exterior body (hereinafter referred to as an exterior body) made of a laminated body having a high degree of freedom in shape. The material structure of the exterior body is composed of at least a base material layer in the outer layer, a metal foil layer, a heat seal layer in the inner layer, and an adhesive layer that bonds the above layers in view of necessary physical properties, workability, economy, and the like as a battery. Further, there is a pouch type in which a pouch is formed from the exterior body configured as described above and the lithium ion battery main body is accommodated, or an embossed type in which the exterior body is pressed to form a recess and the lithium ion battery main body is accommodated in the recess. Has been developed.

FIG. 4A is a perspective view of a pouch-type lithium ion battery using the pillow-shaped exterior body 10, and FIG. 4B is a perspective view showing a state in which the lithium ion battery is disassembled. As shown in FIGS. 4A and 4B, the lithium ion battery 1 is composed of a lithium ion battery body 2 and an exterior body 10, and the lithium ion battery body 2 housed in the exterior body 10 is Moisture resistance is secured by sealing the periphery.

  FIG. 5 is a perspective view of an embossed type lithium ion battery in which the lithium ion battery main body 2 is hermetically housed using an exterior body 5 including a tray and a sheet on which an embossed portion is formed.

  The lithium ion battery body 2 includes a positive electrode composed of a positive electrode active material and a positive electrode current collector, a negative electrode composed of a negative electrode active material and a negative electrode current collector, and an electrolyte filled between the positive electrode and the negative electrode (none shown). And a metal terminal 4 that is connected to a positive electrode and a negative electrode in the cell 3 and has a tip protruding outside the exterior body 5.

  In any of the above types, when the lithium ion battery body is sealed with the exterior body, the metal terminal 4 connected to each of the positive electrode and the negative electrode of the lithium battery body is protruded to the outside and the metal terminal 4 is disposed with the exterior body. It is necessary to seal by heat sealing in the sandwiched state.

  However, after the exterior body is hermetically sealed by heat sealing, an abnormal temperature rise may occur inside the battery due to overcharging or the like, and the metal terminal 4 may generate heat. At this time, the metal terminal 4 may melt the heat seal layer and contact the metal foil layer 4 as a barrier layer to cause an internal short circuit.

  In general, the lithium ion battery 1 is housed and used in a plastic case. At this time, the lithium ion battery 1 is housed in a plastic case by bending the periphery of a heat-sealed outer package.

  However, in this folding step, the heat seal layer is once melted and recrystallized at the time of heat sealing, and therefore cracks are likely to occur when an excessive load is applied. And an electrolyte may contact with a metal foil layer through this crack, and a metal foil layer may energize. At this time, the output of the lithium ion battery is considered to be significantly reduced.

  In view of the above problems, an object of the present invention is to provide a battery packaging material that is excellent in heat resistance, hermetic sealing, insulation, and moldability.

  In order to achieve the above object, the first configuration of the present invention includes a base material layer, a metal foil layer provided with a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, a high melting point polypropylene layer, and ethylene / propylene random In a battery packaging material in which a heat seal layer composed of a copolymer layer is at least sequentially laminated, the high melting point polypropylene layer is disposed on the metal foil layer side from the ethylene / propylene random copolymer layer, and the melting point is 150 ° C. or higher. It is a packaging material for batteries characterized by being.

  The battery packaging material of the second configuration of the present invention is a three-layer structure comprising three layers of the acid-modified polyolefin layer, the high melting point polypropylene layer, and the ethylene / propylene random copolymer layer on the chemical conversion treatment surface of the metal foil layer. The coextruded film is laminated by a heat laminating method.

  The battery packaging material of the third configuration of the present invention is characterized in that the chemical conversion treated surface of the metal foil layer and the heat seal layer are laminated with a molten acid-modified polyolefin layer.

  The battery packaging material of the fourth configuration of the present invention is characterized in that the ethylene / propylene random copolymer layer has a melting point of 120 ° C. or higher and 150 ° C. or lower.

  The battery packaging material of the fifth configuration of the present invention is characterized in that the acid-modified polyolefin layer is made of acid-modified polypropylene.

  According to the first configuration of the present invention, by disposing a high melting point polypropylene layer having a melting point of 150 ° C. or more on the metal foil layer side from the ethylene / propylene random copolymer layer, an abnormal temperature inside the exterior body due to overcharge or the like. Even when the rise occurs, the metal terminal inside the exterior body generates heat, and the ethylene / propylene random copolymer layer as the inner layer melts, the high melting point polypropylene layer does not dissolve, and the metal terminal and the metal foil layer are in contact with each other. prevent. Thereby, generation | occurrence | production of an internal short circuit can be suppressed.

  In order to secure the storage space for the lithium ion battery, the heat seal part of the outer package may be bent, but by forming the heat seal layer with an ethylene / propylene random copolymer layer having excellent rigidity, cracks in the bent part can be obtained. Can be prevented. Thereby, it can prevent that the electrolyte inside an exterior body contacts a metal foil layer from the cracked part, and can ensure the insulation of an exterior body.

  According to the second configuration of the present invention, a three-layer coextruded film composed of three layers of an acid-modified polyolefin layer, a high melting point polypropylene layer, and an ethylene / propylene random copolymer layer is formed on the surface of the metal foil by chemical lamination. By laminating, a laminate having excellent interlayer adhesion strength can be provided.

  According to the third configuration of the present invention, a film composed of two layers of a high melting point polypropylene layer and an ethylene / propylene random copolymer layer is bonded to the chemical conversion treatment surface of the metal foil layer with a molten acid-modified polyolefin layer, A laminate having excellent content resistance and interlayer adhesion strength can be provided.

  According to the 4th structure of this invention, a low temperature sealing property is securable by using a thing whose melting | fusing point is 120 to 150 degreeC for an ethylene propylene random copolymer layer. Even when the electrode is heated due to overcharge or the like, the high melting point polypropylene layer prevents a short circuit between the metal foil layer and the metal terminal.

According to the fifth configuration of the present invention, when acid-modified polypropylene is used for the acid-modified polyolefin layer, the material is the same material as the high melting point polypropylene layer, so the affinity is high, and the interlayer adhesion between both layers is improved, and more Delamination can be prevented.

These are schematic sectional drawings which show the layer structure of the packaging material for batteries of this invention. These are the expanded sectional views which show the structure of the metal terminal periphery of the lithium ion battery using the packaging material for batteries of this invention. These are the schematic perspective view and sectional drawing at the time of accommodating the lithium ion battery using the packaging material for batteries of this invention in the plastic case. FIG. 2 is a schematic perspective view showing a conventional pouch-type lithium ion battery in an exploded manner. FIG. 2 is a schematic perspective view showing a conventional embossed type lithium ion battery in an exploded manner.

  The present invention is a packaging material for a lithium ion battery excellent in low-temperature sealing properties, hermetic sealing properties, and insulation properties. The exterior body will be described in more detail with reference to the drawings. In addition, the same code | symbol is attached | subjected to the part which is common in FIG. 4, FIG. 5 of a prior art example, and description is abbreviate | omitted.

  The material which comprises each layer of the packaging material for batteries of this invention is demonstrated with reference to FIG. The outer package according to the present invention has a base material layer 12 as an outermost layer, a heat seal layer 14 as an innermost layer, and a metal foil layer 13 disposed therebetween.

The heat seal layer 14 includes a high melting point polypropylene layer 17 having a melting point of 150 ° C. or more and an ethylene / propylene random copolymer layer 18. The high melting point polypropylene layer 17 is disposed on the metal foil layer 13 side and is formed by the acid-modified polyolefin layer 16. The metal foil layer 13 is bonded.

  At this time, by providing the chemical conversion treatment layer 13a on the surface of the metal foil 13 on the acid-modified polyolefin layer 16 side, the interlayer adhesion strength is further stabilized. Moreover, the chemical conversion treatment layer 13a is provided also to the base material layer 12 side of the metal foil 13, and the base material layer 12 and the metal foil layer 13 are adhere | attached through the contact bonding layer 15 with the dry lamination method.

  FIG. 2 is an enlarged cross-sectional view showing the configuration around the positive electrode tab of the lithium ion battery. Portions common to FIG. 1 are denoted by the same reference numerals and description thereof is omitted. Further, the chemical conversion treatment layer 13a, the acid-modified polyolefin 16 and the adhesive layer 15 shown in FIG. 1 are omitted for simplification. The outer package 10 has a laminated structure composed of a plurality of layers, and is heat-sealed with the metal terminal 4 sandwiched between the innermost ethylene / propylene random copolymer layers 18.

  Although not shown in the figure, when the metal terminal 4 and the ethylene / propylene random copolymer layer 18 are heat-sealed through the battery metal terminal sealing adhesive film, the battery metal terminal sealing adhesive film is made of metal. On the other hand, the ethylene / propylene random copolymer layer 18 may have a heat sealing property, and may have a heat sealing property with respect to a metal.

  Lithium ion batteries are lithium ion batteries using a pouch type that uses a pillow-shaped exterior body 10 and an exterior body 10 that includes a tray and a sheet formed with an embossed portion, depending on the type of the exterior body that wraps the lithium ion battery body. There is an embossed type in which the battery body is hermetically stored, but the present invention can be applied to any type.

  In this lithium ion battery, the temperature inside the outer package 10 rises due to overcharge or the like, and the metal terminal 4, the electrode, and the current collector may generate heat. At this time, the sandwiched portion of the metal terminal 4 of the ethylene / propylene random copolymer layer 18 which is the innermost layer is melted, and as a result, the metal foil layer 13 in the outer package 10 and the metal terminal 4, the electrode and the current collector are brought into contact and short-circuited. May cause.

  However, as shown in the figure, when a polypropylene layer 17 having a melting point of 150 ° C. or higher is provided between the metal foil 13 and the ethylene / propylene random copolymer layer 18, even when the ethylene / propylene random copolymer layer 18 is melted. The polypropylene layer 17 does not melt easily because of its high melting point. Therefore, it can prevent that the metal terminal 4 and the metal foil 13 contact and short-circuit.

  3A is a schematic perspective view showing the lithium ion battery 1, and FIG. 3B is a schematic perspective view showing the lithium ion battery 1 housed in a plastic case 19 indicated by a dotted line.

  After encapsulating the lithium ion battery body in the embossed outer package 10, the peripheral edge 10b is hermetically sealed to complete the lithium ion battery 1. However, when the lithium ion battery 1 is actually used, It is weak to impact and may cause cracking due to small scratches.

  Therefore, the lithium ion battery 1 is often stored and used in a plastic case 19. For example, when it is used for a mobile phone or the like, it is stored in a plastic case because it receives an impact when dropped.

  Here, in order to reduce the size of the lithium ion battery 1, it is necessary to fold the outer periphery seal portion 10 b of the lithium ion battery 1 and store it in the plastic case 19. FIG. 3C is a cross-sectional view of the lithium ion battery 1 housed in the plastic case 19 as viewed from the direction of the arrow x in FIG.

  In the bent portion 10c, which is the fold of the peripheral seal portion 10b, the heat seal layer is once melted at the time of heat sealing and then crystallized, so that cracking is likely to occur at the time of bending. Then, the cracking may cause the electrolyte inside the outer package 10 to come into contact with the metal foil layer 13 to energize the metal foil layer 13. At this time, the output of the lithium ion battery is significantly reduced or the function of the battery is lost.

  Therefore, the battery packaging material according to the present invention uses the ethylene / propylene random copolymer layer 18 having excellent rigidity for the heat seal layer 14 to prevent cracking of the heat seal layer 14 and ensure the insulation of the outer package 10.

  Further, when the lithium ion battery main body is sealed in the outer casing 10 and the metal terminal 4 of the battery main body is sandwiched and sealed in a projecting state, heat is applied to the step due to the sandwiched portion of the metal terminal 4 and the thickness of the metal terminal 4. If the resin of the sealing layer does not go around, complete sealing cannot be secured.

  Therefore, it is necessary to use a resin having moderate fluidity at the time of heat sealing. Here, by using an ethylene / propylene random copolymer layer 18 having a melting point of 120 ° C. or more and 150 ° C. or less, the ethylene / propylene random copolymer has appropriate fluidity during heat sealing, and the entire sandwiched portion of the metal terminal 4 The opening of the outer package 10 is hermetically sealed so as to cover. Therefore, the external water vapor | steam which permeate | transmits from the said metal terminal clamping part can be interrupted | blocked, and the production | generation of hydrofluoric acid by reaction of electrolyte and water vapor | steam can be suppressed.

  Here, when an ethylene / propylene random copolymer layer having a melting point lower than 120 ° C. is used, there is a possibility that the heat seal layer flows out completely during heat sealing. When the melting point is higher than 150 ° C., the heat seal layer does not melt during heat sealing, and the fluidity is low, so that the periphery of the sandwiched portion of the metal terminal cannot be hermetically sealed.

  Next, a lamination method in the exterior body 10 according to the present invention will be described. The lamination method of the metal foil layer 13 and the heat seal layer 14 is roughly classified into a dry lamination method using a known dry lamination adhesive such as polyester and a thermal lamination method performed without using an adhesive. Although the dry lamination method is excellent in productivity, the moisture permeability from the cross section of the adhesive layer is high even though the thickness of the adhesive layer is about 3 to 5 μm, and the moisture infiltrated from the cross section is the inner layer. This causes a problem that hydrofluoric acid is generated by reacting with the electrolytic solution and this causes the metal foil layer and the heat seal layer 14 to peel off over time.

  Therefore, in the present invention, a method of laminating a co-pressing film comprising the acid-modified polyolefin layer 16 and the heat seal layer 14 on the metal foil layer 13 by a heat laminating method, and the molten acid-modified polyolefin is heat-sealed with the metal foil layer 13. A sandwich lamination method in which the layer 14 is sandwiched and laminated is used. Any of these methods is a lamination method that is superior in content resistance and durability as compared with the dry lamination method.

  The thermal lamination method has a high adhesive strength and a high sealing performance. Specifically, acid modification of a three-layer coextruded film consisting of three layers of an acid-modified polyolefin layer, a high melting point polypropylene layer, and an ethylene / propylene random copolymer layer on the chemical treatment surface of a metal foil layer such as aluminum subjected to chemical conversion treatment Laminate the layers of the polyolefin layer and heat laminate.

  The sandwich lamination method is a method in which an acid-modified polyolefin such as acid-modified polypropylene is extruded as an adhesive resin on the chemical conversion treatment surface of the metal foil layer 13 such as aluminum, and the heat seal layer 14 is sandwich-laminated. In addition, when the acid-modified polypropylene is extrusion-laminated, the obtained laminate is heated to the softening point or higher of the acid-modified polypropylene (post-heating), or in the extrusion process of the acid-modified polypropylene, the aluminum surface is acid-modified polypropylene. By heating above the softening point (preheating), a laminate having adhesive strength capable of withstanding the content resistance and moldability as a lithium ion battery exterior body becomes possible.

  In addition, as a specific method of the heating, there are methods such as a hot roll contact method, a hot air method, a near or far infrared ray, and any heating method may be used in the present invention. What is necessary is just to be able to heat more than the softening point temperature.

  Next, each layer of the outer package 10 shown in FIG. 1 will be specifically described. The base layer 12 is generally made of stretched polyester or nylon film. In this case, examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, and polycarbonate. 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.

The base material layer 12 may be laminated with films of different materials in addition to the 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 12 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 12-25 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 Mechanical suitability of packaging materials (stability of conveyance in packaging machines and processing machines), surface protection (heat resistance, electrolyte resistance) When making the exterior body for a lithium ion battery as an embossed type as a secondary process, the base material layer is formed for the purpose of reducing the frictional resistance between the mold and the base material layer during embossing or when an electrolytic solution adheres. In order to protect, it is preferable that the base material layer is multi-layered and the surface of the base material layer is provided with a fluorine resin layer, an acrylic resin layer, a silicone resin layer, a polyester resin layer, and a blended material layer thereof.
For example,
3) Fluorine resin / stretched polyethylene terephthalate (Fluorine resin is a film or formed by drying 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 film-like or cured after drying by liquid coating)

  The same effect can be obtained when stretched polybutylene terephthalate or polyethylene naphthalate is used in place of the stretched polyethylene terephthalate.

  Here, the base material layer 12 is bonded to the metal foil layer 13 by the adhesive layer 15 using a dry laminating method.

  Next, the metal foil layer 13 will be described. The metal foil layer 13 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 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 is 20 to 80 μm.

  In order to further improve the generation of pinholes and make the outer body type of the lithium ion battery an embossed type, in order to prevent the occurrence of cracks in the embossing molding, the material of the aluminum used as the metal foil layer 13 is By making the iron content 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight, compared with aluminum not containing iron, aluminum has good extensibility, The generation of pinholes due to bending as the exterior body is reduced, and the side wall can be easily formed when the embossed exterior body is molded. 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 the aluminum exceeds 9.0% by weight. In this case, the flexibility as aluminum is hindered, and the bag-making property as an exterior body 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. The degree of flexibility, waist strength, and hardness of aluminum, that is, the conditions for annealing, may be appropriately selected in accordance with processability (pouching, embossing). For example, in order to prevent wrinkles and pinholes at the time of emboss molding, annealed soft aluminum according to the degree of molding can be used.

  Moreover, the adhesive strength with the adhesive 15 improves by performing the chemical conversion treatment 13a on the front and back surfaces of the aluminum that is the metal foil layer 13.

  Next, the chemical conversion treatment layer 13a will be described. The chemical conversion treatment layer 13a is formed on at least the surface of the metal foil 13 on the heat seal layer 14 side. The chemical conversion treatment layer 13a can stably adhere the acid-modified polyolefin layer 8 and the metal foil 13 and prevent delamination of the metal foil 13 and the heat seal layer 14. It also has the function of preventing aluminum corrosion.

  Specifically, by preventing the delamination between the metal foil layer 13 and the heat seal layer 14 during embossing by forming an acid-resistant film such as phosphate, chromate, fluoride, triazine thiol compound, etc. The 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. Adhesion (wetting) can be improved.

  The chemical conversion treatment layer 13a is made of metal by chromium chemical conversion treatment such as chromate chromate treatment, phosphoric acid chromate treatment, and coating type 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 13, it is firmly bonded to the fluororesin 15, and a continuous process is possible and a 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 13a, a known coating method such as a barcode method, a roll coating method, a gravure coating method, a dipping method or the like may be selected to form the processing liquid. Moreover, before forming the chemical conversion treatment layer 13a, the surface of the metal foil 13 is preliminarily treated by a known degreasing method such as an alkali dipping method, an electrolytic cleaning method, an acid cleaning method, or an acid activation method. In addition, the chemical conversion treatment layer 13a is preferable in that it can exhibit the function 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.

  Next, the acid-modified polyolefin layer 16 will be described. The acid-modified polyolefin layer 16 is a layer provided for adhering the metal foil layer 13 and the heat seal layer 14 that is the inner layer of the outer package 10, and it is necessary to select and use as appropriate depending on the resin type used for the heat seal layer 14. However, it is possible to use an acid-modified polyolefin resin, a polyolefin resin graft-modified with an unsaturated carboxylic acid, a copolymer of ethylene or propylene and acrylic acid, or methacrylic acid, or a metal-crosslinked polyolefin resin, 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 in an amount of 5% or more.

  In the present invention, since the acid-modified polyolefin layer 16 adheres to the high melting point polypropylene layer in the heat seal layer, it is preferable to use acid-modified polypropylene. Since acid-modified polypropylene is the same quality as high melting point polypropylene as an adhesive, it has high affinity. Therefore, by using acid-modified polypropylene as the adhesive layer, it is possible to provide the outer package 10 that is more excellent in content resistance and adhesive strength.

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.
The acid-modified polypropylene includes a low crystalline ethylene-butene copolymer having a density of 900 kg / m ³ or less, a low crystalline propylene-butene copolymer, or an amorphous ethylene-propylene copolymer, Add 5% or more of amorphous propylene-ethylene copolymer or ethylene-butene-propylene copolymer (terpolymer) to give flexibility, improve bending resistance, and prevent cracking during molding You may go.

  Next, the heat seal layer 14 will be described. As the heat seal layer 14, when the metal terminal 4 connected to each of the positive electrode and the negative electrode of the lithium battery main body is sandwiched in a protruding state and thermally bonded and sealed, the heat seal layer 14 and the metal terminal 4 The resin type differs depending on whether or not a metal terminal sealing adhesive film is interposed between them. When an adhesive film for sealing metal terminals is interposed, a film made of a propylene-based resin alone or a mixture may be used. When an adhesive film for sealing metal terminals is not interposed, it is graft-modified with an unsaturated carboxylic acid. A film made of an acid-modified olefin resin may be used.

  In the present invention, as the heat seal layer 14, a high melting point polypropylene layer having a melting point of 150 ° C. or more and an ethylene / propylene random copolymer having excellent rigidity are arranged on the metal foil layer 13 side and the innermost layer side, respectively.

  Ethylene / propylene random copolymer is a copolymer of ethylene and propylene, and is an irregular polymerized arrangement of ethylene and propylene repeating units, so it is compared with blended resins that only melted ethylene resin and propylene resin. And very excellent rigidity.

  Therefore, even when the exterior body is bent after heat sealing, the occurrence of cracks in the heat sealing layer can be prevented. This is because the ethylene-propylene random copolymer is a copolymer, so when it is once melted and solidified during heat sealing, the ethylene repeating unit and the propylene repeating unit are separated and do not solidify. It is for solidifying uniformly.

In addition to the base material layer 12, the metal foil layer 13, the adhesive layer 15, and the heat seal layer 14 (polypropylene or polyethylene), between the metal foil layer 13 and the heat seal layer 14, 2 such as polyimide and polyethylene terephthalate are used. An intermediate layer made of an axially stretched film or the like may be provided. An intermediate | middle layer can prevent the short circuit by contact with the tab and metal foil layer at the time of the heat sealing of a lithium ion battery exterior body at the time of the heat improvement of a lithium ion battery exterior body as a packaging material for lithium ion batteries.

  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. The base material layer was a stretched nylon film (thickness 25 μm), and the barrier layer was aluminum 40 μm. In each of the chemical conversion treatments, an aqueous solution composed of a phenol resin, a chromium fluoride compound, and phosphoric acid was used as a treatment solution, applied by a roll coating method, and baked under conditions where the film temperature was 180 ° C. or higher. The application amount of chromium is 10 mg / m ² (dry weight). Acid-modified polypropylene (hereinafter abbreviated as acid-modified PP) was applied by a roll coating method and baked under conditions where the aluminum temperature was 180 ° C. or higher. The coating amount of the acid-modified PP was 3 g / m ² (dry weight).

  A chemical conversion treatment is performed on both sides of aluminum, and one side of the chemical conversion treatment surface is bonded with a stretched nylon film by a dry laminating method via a two-component curable polyurethane adhesive, and the other chemical conversion treatment surface is roll-coated with acid-modified PP. Applying and baking by the method, acid-modified polypropylene film (thickness 10 μm), high melting point polypropylene film (thickness 30 μm), and ethylene-propylene random copolymer film (thickness 20 μm) by heat laminating on the acid-modified PP surface A three-layer coextruded film consisting of three layers was laminated to obtain a battery packaging material of the present invention.

  A chemical conversion treatment is performed on both surfaces of aluminum, and a stretched nylon film is bonded to one chemical conversion treatment surface by a dry laminating method via a two-component curable polyurethane adhesive, and an acid-modified PP (thickness) is applied to the other chemical conversion treatment surface. 10 μm) was melt extruded and a sealant film composed of a high melting point polypropylene film (thickness 30 μm) and an ethylene / propylene random copolymer film (thickness 20 μm) was laminated to obtain a battery packaging material of the present invention.

  The battery packaging material obtained in Example 1 and Example 2 was made into a single-sided embossed type exterior body, the embossed part for that was 55 mm × 30 mm, the depth was 3.5 mm, the embossed sheet, and the lithium ion battery body Was sealed and hermetically sealed with a seal width of 5 mm.

  When the hermetically sealed lithium ion battery was bent at a location where the seal width was 3 mm and overcharging was repeated to change the temperature of the tab, no short circuit occurred in any of the examples. From the above, it was found that the sealing property of the outer package at the pinched portion of the tab and the insulating property at the seal portion are ensured.

DESCRIPTION OF SYMBOLS 1 Lithium ion battery 2 Lithium ion battery main body 3 Cell (electric storage part)
4 Metal terminal (tab)
DESCRIPTION OF SYMBOLS 5 Exterior body 7 Clamping part 8 Positive electrode collector 10 Exterior body 10b Outer body peripheral part 10c Bending part 12 Base material layer 13 Metal foil layer 13a Chemical conversion treatment layer (metal foil layer surface)
14 Innermost layer (heat seal layer)
15 Adhesive layer 16 Acid-modified polyolefin layer 17 High melting point polypropylene layer 18 Ethylene / propylene random copolymer layer 19 Plastic case

Claims (5)

A battery in which a base material layer, a metal foil layer provided with a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, a heat-seal layer comprising a high-melting-point polypropylene layer and an ethylene / propylene random copolymer layer are laminated at least in sequence. For packaging materials,
The high melting point polypropylene layer is disposed on the metal foil layer side from the ethylene / propylene random copolymer layer, has a melting point of 150 ° C. or higher, and the ethylene / propylene random copolymer layer has a melting point of 120 ° C. or higher and 150 ° C. or lower (130 ° C. And a three-layer coextruded film comprising three layers of the acid-modified polyolefin layer, the high-melting-point polypropylene layer, and the ethylene / propylene random copolymer layer on the chemical treatment surface of the metal foil layer. A battery packaging material characterized by being laminated by a thermal laminating method. A battery in which a base material layer, a metal foil layer provided with a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, a heat-seal layer comprising a high-melting-point polypropylene layer and an ethylene / propylene random copolymer layer are laminated at least in sequence. For packaging materials,
The high melting point polypropylene layer is disposed on the metal foil layer side from the ethylene / propylene random copolymer layer, has a melting point of 150 ° C. or higher, and the ethylene / propylene random copolymer layer has a melting point of 120 ° C. or higher and 150 ° C. or lower (130 ° C. 3 except for the acid-modified polyolefin layer, the high-melting-point polypropylene layer, and the ethylene / propylene random copolymer layer on the acid-modified polypropylene surface formed on the chemical conversion treatment surface of the metal foil layer. A battery packaging material, wherein a three-layer coextruded film comprising layers is laminated by a thermal laminating method. A battery in which a base material layer, a metal foil layer provided with a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, a heat-seal layer comprising a high-melting-point polypropylene layer and an ethylene / propylene random copolymer layer are laminated at least in sequence. For packaging materials,
The high melting point polypropylene layer is disposed on the metal foil layer side from the ethylene / propylene random copolymer layer, has a melting point of 150 ° C. or higher, and the ethylene / propylene random copolymer layer has a melting point of 120 ° C. or higher and 150 ° C. or lower (130 ° C. And the acid-modified polyolefin layer and the high-melting-point polypropylene are formed on the surface of the acid-modified polypropylene formed by applying and baking acid-modified polypropylene on the chemical conversion surface of the metal foil layer by a roll coating method. A battery packaging material, wherein a three-layer coextruded film composed of three layers of an ethylene / propylene random copolymer layer is laminated by a heat laminating method. The battery packaging material according to any one of claims 1 to 3, wherein the acid-modified polyolefin layer is made of acid-modified polypropylene . A three-layer coextruded film comprising a base material layer, a metal foil layer provided with a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, a high melting point polypropylene layer, and an ethylene / propylene random copolymer layer in this order from the metal foil layer side Is a method for designing a battery packaging material laminated at least in sequence, wherein acid-modified polypropylene is selected as the acid-modified polyolefin layer, polypropylene having a melting point of 150 ° C. or higher is selected as the high-melting-point polypropylene layer, A method for designing a battery packaging material, wherein an ethylene / propylene random copolymer having a melting point of 120 ° C. or higher and 150 ° C. or lower (excluding 130 ° C. or higher and 135 ° C. or lower) is selected as the ethylene / propylene random copolymer layer.

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