JP2007294381A - Packaging material for battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a packaging material for a battery having stable sealing performance, heat resistance, insulating performance, and molding performance. <P>SOLUTION: The packaging material for the battery is formed by laminating in order at least a substrate layer 12 of the outermost layer, a metal foil layer 13 having a chemical conversion treatment layer on at least one side, and a heat seal layer 14 of the inner most layer, and the metal foil layer is aluminum foil having a thickness of 80-120 μm, and the heat seal layer 14 is made of a layer 16 containing an ethylene-propylene random copolymer layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

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 includes at least a base material layer in the outer layer, a barrier layer composed of a metal foil layer, a heat seal layer in the inner layer, and an adhesive layer that bonds the respective layers in view of necessary physical properties, workability, economy, etc. Consists of. 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. 8A is a perspective view of a pouch-type lithium ion battery using the pillow-shaped exterior body 5, and FIG. 8B is a perspective view showing a state in which the lithium ion battery is disassembled. As shown in FIGS. 8A and 8B, the lithium ion battery 1 is composed of a lithium ion battery body 2 and an exterior body 5, and the lithium ion battery body 2 housed in the exterior body 5 is By sealing the periphery, moisture resistance is secured.

  FIG. 9 is a perspective view of an embossed type lithium ion battery in which the lithium ion battery main body 2 is hermetically housed using the exterior body 5 including the tray 5a and the sheet 5b in which the 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 tab (metal terminal) 4 that is connected to a positive electrode and a negative electrode in the cell 3 and has a tip projecting outside the exterior body 5.

  FIG. 10 shows the structure of a press for forming an embossed type exterior body. FIG. 10A is a perspective view of the male mold 21 and the female mold 22 and the outer package 10 before pressing, and FIG. 10B is a perspective view of the outer package molded into a concave shape after pressing. Here, in the case of the embossed type exterior body 10, as shown in FIG. 10A or FIG. 10B, it is necessary to form a recess for housing the lithium ion battery body by press molding or the like.

  Also, in any of the above types, when the lithium ion battery main body is sealed with the packaging material, the metal terminal connected to each of the positive electrode and the negative electrode of the lithium battery main body is protruded to the outside and the metal terminal is sandwiched with the packaging material. It is necessary to seal by thermal bonding in the state. For this purpose, the inner layer of the packaging material is heat-adhered and sealed with a heat-adhesive resin having good adhesion to the metal, for example, an acid-modified olefin resin graft-modified with an unsaturated carboxylic acid, or Using an ordinary olefin-based resin that is inferior in adhesiveness to metal for the inner layer, the metal terminal sealing adhesive film made of the above-mentioned acid-modified olefin resin having good adhesiveness to the metal is used as the metal terminal and the inner layer. Generally, a method of interposing between them and sealing them by thermal bonding is generally used.

  By the way, since the lithium ion battery enclosed in the exterior body which consists of a laminated body has low impact resistance etc. compared with the lithium battery comprised by a metal can, it is normally accommodated and used for a plastic case. However, even with a drop impact or the like, the lithium battery may hit the inner wall of the plastic case, and pinholes and cracks may be generated in the exterior body.

  Usually, it is common to use a metal foil such as an aluminum foil having a thickness of about 50 μm as the barrier layer provided in the laminate. This is because the aluminum foil is lightweight and easy to process and is easy to process. In order to improve the impact resistance of the body, it seems to be sufficient to provide a thick aluminum foil.

  However, when the lithium ion battery is stored in a plastic case after heat sealing, the outer periphery of the heat-sealed outer package may be bent. At this time, if the aluminum foil is thicker than a predetermined thickness, distortion will occur during bending. Increases, delamination occurs between the aluminum foil and the heat seal layer, and cracks tend to occur in the heat seal layer.

  In addition to the distortion caused by the thickness of the aluminum foil, it takes time until the heat retained in the aluminum foil is dissipated due to the thickness of the aluminum foil. Cracks may occur during partial folding.

  Then, the electrolyte comes into contact with the metal foil layer through the crack, the metal foil layer is energized, and the insulating property of the lithium-in battery exterior body is lost.

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

  In order to achieve the above object, the first configuration of the present invention includes a base material layer that is an outermost layer, a metal foil layer having a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, and a heat that is an innermost layer. In the battery packaging material in which at least a seal layer is sequentially laminated, the metal foil layer is an aluminum foil having a thickness of 80 μm or more and 120 μm or less, and the heat seal layer is a layer including an ethylene / propylene random copolymer film layer. A battery packaging material characterized by the following.

  The battery packaging material of the second configuration of the present invention is a second polypropylene layer having a lower melting point and a higher melt index on the inner layer side of the layer including the ethylene / propylene random copolymer film layer than the ethylene / propylene random copolymer film layer. Is provided.

  The battery packaging material of the third configuration of the present invention is a polypropylene layer in which the second polypropylene layer is melt-extruded.

  The battery packaging material of the fourth configuration of the present invention is characterized in that the melt-extruded polypropylene 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 melt-extruded polypropylene layer has a melt index of 5 g / 10 min to 30 g / 10 min.

  The battery packaging material of the sixth configuration of the present invention is characterized in that the melting point of the heat seal layer excluding the second polypropylene layer is 140 ° C. or higher and 180 ° C. or lower.

  The battery packaging material of the seventh configuration of the present invention is characterized in that a lubricant is added to the resin of the second polypropylene layer.

  The battery packaging material of the eighth configuration of the present invention is characterized in that the surface of the base material layer is composed of a stretched polyester or a polybutylene terephthalate film.

  According to the first configuration of the present invention, the exterior body has an aluminum foil having a thickness of not less than 80 μm and not more than 120 μm, thereby improving impact resistance and puncture resistance.

  In addition, the heat seal portion of the exterior body may be folded to secure a storage space for the lithium ion battery, but the folding is performed by forming the heat seal layer with a layer including an ethylene / propylene random copolymer layer having excellent toughness. The generation of cracks in the part 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, when the second polypropylene layer having a low melting point and a high melt index is disposed on the innermost layer side, when the heat seal layer is overlapped and the seal portion is heated and pressurized, the second The polypropylene layer melts with a certain viscosity faster than the other polypropylene layers and is extruded toward the inside of the outer package. Therefore, after heat sealing, the second polypropylene layer forms a uniform heat seal layer in the vicinity of the boundary between the seal portion and the exterior body so that no resin pool is generated, and this suppresses a decrease in seal strength over time at the portion. it can. Therefore, the sealing performance of the exterior body can be ensured for a long time.

  According to the third configuration of the present invention, the heat sealing temperature can be lowered while maintaining the sealing strength by providing the polypropylene layer melt-extruded on the inner layer side of the layer including the ethylene / propylene random copolymer layer. Thereby, the lithium battery main body can be efficiently hermetically sealed in the battery packaging material, and the productivity of the lithium battery can be improved.

  In addition, when the heat-sealing polypropylene layer is melt-sealed, it seals and seals so as to cover the entire metal terminal clamping portion, thereby blocking external water vapor entering from the metal terminal clamping portion, Generation of hydrofluoric acid due to the reaction can be suppressed.

  According to the fourth configuration of the present invention, the melt-extruded polypropylene layer has a low temperature sealing property because the melting point of the melt-extruded polypropylene layer is 120 ° C. or higher and 150 ° C. or lower, and heat seals at a low temperature. Can do.

  According to the fifth configuration of the present invention, the seal strength can be increased by setting the melt index of the melt-extruded polypropylene layer to 5 g / 10 min or more and 30 g / 10 min or less.

  According to the sixth configuration of the present invention, since the melting point of the heat seal layer excluding the second polypropylene layer is 140 ° C. or more and 180 ° C. or less, an abnormal temperature rise occurs inside the exterior body due to overcharge, etc. Even when the metal terminals, electrodes, and current collectors generate heat and the second polypropylene layer melts, the heat seal layers other than the second polypropylene layer do not melt, and the metal terminals, electrodes, current collector, and metal foil layers To prevent contact. Thereby, generation | occurrence | production of an internal short circuit can be suppressed.

  According to the seventh configuration of the present invention, when the exterior body is embossed by emulsifying the exterior body by adding a lubricant into the resin of the melt-extruded polypropylene layer, the polypropylene layer ensures slipperiness and is molded. In addition, it is possible to further prevent the occurrence of wrinkles due to slipping defects and pinholes and cracks in the barrier layer.

  According to the eighth configuration of the present invention, by using a stretched polyester or polybutylene terephthalate film on the surface of the base material layer, when the electrolyte or acid adheres to the surface of the exterior body, it prevents whitening of the exterior body surface and deterioration of insulation. be able to.

  The present invention is a packaging material for a lithium ion battery that is excellent in low-temperature sealing properties, hermetic sealing properties, impact resistance, insulating properties, and moldability. 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.8, FIG.9, FIG.10 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 an aluminum foil layer 13 therebetween.

  The aluminum foil layer 13 and the heat seal layer 14 are laminated by firmly bonding the chemical conversion treatment layer 13 a applied to the surface of the aluminum foil 13 and the acid-modified polyolefin layer 8. Moreover, the base material layer 12 and the chemically treated aluminum foil layer 13 are bonded with an adhesive layer 15 by a dry laminating method. Further, a slip agent is applied to the surface of the base material layer 12 to form the slip layer 11, and a melt-extruded polypropylene layer 9 is additionally processed on the surface of the layer 16 including the ethylene / propylene random copolymer layer.

  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 8 side, the interlayer adhesion strength is further stabilized.

  2A is a schematic perspective view showing the lithium ion battery 1, and FIG. 2B 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. 2C is a cross-sectional view of the lithium ion battery 1 housed in the plastic case 19 as seen from the direction of the arrow x in FIG. 2B.

  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. In particular, when an aluminum foil having a thickness of 80 μm to 120 μm is used as in the case of the exterior body according to the present invention, the occurrence rate of cracks is increased due to the large distortion of the aluminum foil at the time of bending. Further, since the aluminum foil is thick, it takes time until the heat held in the aluminum foil at the time of heat sealing is dissipated, so that the crystallization of the resin of the heat seal layer proceeds and cracks are likely to occur when the seal portion is bent.

  In addition, due to this cracking, the electrolyte inside the outer package 10 may come into contact with the metal foil layer 13 (see FIG. 1), and the metal foil layer 13 may be energized. At this time, the output of the lithium ion battery is significantly reduced or the function of the battery is lost.

  Therefore, in the battery packaging material according to the present invention, the heat seal layer 14 is provided with a layer 16 including an ethylene / propylene random copolymer layer having excellent toughness to prevent cracking of the heat seal layer 14 and to ensure insulation of the outer package 10. ing.

  FIG. 3 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 slip layer 11, the chemical conversion treatment layer 13a, the acid-modified polyolefin 8, and the adhesive layer 15 shown in FIG. The outer package 10 has a laminated structure composed of a plurality of layers, and is heat-sealed in a state where the metal terminal 4 is sandwiched by the innermost melt-extruded polypropylene layer 9.

  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 (not shown), and the current collector (not shown) may generate heat. At this time, the sandwiched portion of the metal terminal 4 of the melt-extruded polypropylene layer 9 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 in contact with each other and short-circuited. May cause.

  However, as shown in the figure, when a layer 16 containing an ethylene / propylene random copolymer layer having a melting point of 150 ° C. or higher is provided between the metal foil 13 and the melt-extruded polypropylene layer 9, the melt-extruded polypropylene layer 9 Even when is melted, the layer 16 including the ethylene / propylene random copolymer layer does not melt easily because of its high melting point. Therefore, it can prevent that the metal terminal 4, an electrode, a collector, and the metal foil 13 contact and short-circuit.

  Further, when the layer 16 including the ethylene / propylene random copolymer layer is heat-sealed, it is necessary to apply heat and pressure near the melting point of the layer 16 including the ethylene / propylene random copolymer layer to the seal portion. However, heat sealing is performed at a temperature lower than the melting point of the layer 16 including the ethylene / propylene random copolymer layer by providing the melt-extruded polypropylene layer 9 having a melting point of 120 to 150 ° C. on the surface of the layer 16 including the ethylene / propylene random copolymer layer. can do. For this reason, the sealing time can be shortened, the heat sealing process can be simplified, and the production efficiency of the lithium ion battery can be increased.

  At this time, if a melt-extruded polypropylene layer 9 having a melt index of 5 g / 10 min or more and 30 g / 10 min or less is used, sufficient seal strength can be secured at the seal temperature.

  Further, when the lithium ion battery main body is sealed in the outer package 10 and the metal terminal 4 of the battery main body is sandwiched in a state of protruding outward and hermetically sealed, the melt-extruded polypropylene layer 9 has high fluidity, so that the metal terminal The opening of the exterior body 10 is hermetically sealed so as to cover the entire sandwiched portion. 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.

  4A is a cross-sectional view of a lithium ion battery 1 encapsulated using the battery packaging material according to the present invention, and FIGS. 4B and 4C are the vicinity of the inner edge of the seal portion of FIG. 4A. It is sectional drawing which expands and shows 10a. Here, FIG. 4 shows only the metal foil layer 13 and the heat seal layer 14, and the other layers are omitted for explanation. The heat seal layer 14 is composed of two layers, a second polypropylene layer 24 and a first polypropylene layer 25 arranged on the innermost layer side. The second polypropylene layer 24 is melt-extruded as described in FIGS. 1 and 3 above. The polypropylene layer 9 and the first polypropylene layer 25 correspond to the layer 16 including an ethylene / propylene random copolymer layer.

  Generally, the heat seal layer 14 is melted by heat and pressure applied at the time of heat sealing, and is extruded to the inside of the outer package. However, when the heat seal layer 14 is composed of two or more films, the temporal sealing strength after heat sealing differs depending on the arrangement of each film. In other words, by placing a film having a lower melting point and a higher melt index than the other films on the innermost layer side, a stable shape in which the resin reservoir 25a that causes distortion or cutting is not formed in the vicinity 10a of the inner edge of the sealed portion after sealing. Can be sealed.

  FIG. 4B is a diagram illustrating the flow of the heat seal layer 14 when the second polypropylene layer 24 has a higher melting point than the first polypropylene layer 25 and a low melt index. In this case, since the first polypropylene layer 25 has a lower melting point and a higher melt index than the second polypropylene layer 24 at the time of heat sealing, the first polypropylene layer 25 tends to flow out to the inside of the exterior body. The second polypropylene layer 24 cannot follow the flow (see arrow in FIG. 4B). For this reason, the resin reservoir 25a is formed in the vicinity 10a of the seal portion inner edge, and the thickness of the heat seal layer 14 becomes nonuniform in the periphery of the resin reservoir 25a. Accordingly, immediately after heat sealing, the resin reservoir 25a adheres in the heat seal layer 14 and apparently shows a certain heat seal strength, but the electrolyte penetrates into the peripheral portion of the resin reservoir 25a with time and the portion peels off. As a result, the seal strength decreases. Therefore, the deterioration of the sealing performance of the exterior body over time becomes a problem.

  FIG. 4C shows the flow of the heat seal layer 14 when the innermost second polypropylene layer 24 has a lower melting point than the first polypropylene layer 25 and a higher melt index. When the seal portion is heated and pressurized, the innermost second polypropylene layer 24 has a lower melting point and a higher melt index than the first polypropylene layer 25, so that it will flow along the first polypropylene layer 25 to the inside of the outer package. (See arrow in FIG. 4 (c)).

  For this reason, after heat sealing, the uniform heat seal layer 14 is formed by the second polypropylene layer 24 in the vicinity 10a of the seal portion inner edge, and the resin pool 25a is not generated. Therefore, stable sealing performance is ensured in the vicinity of the inner edge 10a of the seal portion, and the deterioration of the seal strength with time is prevented as compared with the heat seal layer 14 in which the resin reservoir 25a shown in FIG. 4B is formed. Can do.

  Fig.5 (a) is a schematic perspective view which shows an example of the press work of the exterior body 10 which concerns on this invention. 21 is a male type, 10 is an outer package before pressing, and 22 is a female type. The exterior body 10 before pressing faces the surface on which the slip layer 11 is provided on the female die 22 side, and presses the surface of the heat seal layer 14 on which the polypropylene layer 9 is provided with the male die 21.

  FIG. 5B is a cross-sectional view showing the force acting on the exterior body 10 when the exterior body 10 is pressed. When pressed into a concave shape, as the depth of the side wall portion 22a of the female die 22 increases, the slipperiness between the surface of the base material layer 12 and the inner surface of the female die 22 becomes important. When a downward press is applied to the exterior body 10, a downward force x (arrow) due to the male die 21 acts on the heat seal layer 14 in the side wall portion 22 a, whereas an upward force due to friction acts on the base material layer 12. y (arrow) works. Therefore, a shearing force parallel to the interlayer adhesion surface of the outer package 10 acts on the outer package 10, and the work exerted on the outer package 10 by the shear force increases as the depth of the side wall portion 22a of the female die 22 increases. Causes delamination of the laminated structure or cracking of the barrier layer. Therefore, the slipperiness between the female die 22 and the base material layer 12 becomes important.

  On the other hand, when the slipperiness between the male mold 21 and the heat seal layer 14 is insufficient, the heat seal layer 14 is dragged to the male mold 21 during pressing, and the heat seal layer 14 may be wrinkled or torn. is there.

  Therefore, it is conceivable to coat the surface of the heat seal layer 14 with a slip agent in order to reduce the dynamic friction coefficient between the heat seal layer 14 and the male mold 21. However, in the exterior body 10 according to the present invention, the polypropylene layer 9 is additionally processed on the surface of the heat seal layer 14 and has a certain slip property. For this reason, it is not necessary to newly coat a slip agent on the heat seal layer, and the embossing can be performed stably.

  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.

In addition, the base material layer 12 can be laminated with films of different materials in addition to the polyester film and 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 cured in a film or liquid coating and dried)

  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 addition, aluminum having a thickness of 80 μm or more and 120 μm or less is used in order to have a pinhole resistance.

  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 during emboss molding, soft aluminum annealed according to the degree of molding can be used.

  Moreover, the adhesive strength with the acid-modified polyolefin layer 8 or the adhesive agent 15 improves by performing the chemical conversion treatment 13a to the aluminum which 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 8 will be described. The acid-modified polyolefin layer 8 is a layer provided for adhering the metal foil layer 13 and the heat seal layer 14 which is the inner layer of the outer package 10, and it is necessary to select and use it appropriately 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.

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, 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 state of protruding outward, and is thermally bonded and sealed.

  In the present invention, a layer 16 including an ethylene / propylene random copolymer layer having excellent toughness is used as the heat seal layer 14.

  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 tough.

  Therefore, even when the aluminum foil having a thickness of 80 μm to 120 μm is used as in the exterior body according to the present invention and the exterior body is bent after heat sealing, generation of cracks in the heat seal layer 14 can be prevented. . This is because the ethylene / propylene random copolymer is a copolymer, so even when it is melted and solidified at the time of heat sealing, the ethylene and propylene molecules are not separated and solidified. It is to do. Therefore, the ethylene / propylene random copolymer is not easily crystallized even when the heat at the time of heat sealing is retained in the aluminum foil by providing the aluminum foil with a thickness. From the above, the ethylene / propylene random copolymer has a certain toughness even after heat sealing and can be suitably used as a heat sealing layer.

  Further, by adding an ethylene / propylene block copolymer layer having a high melting point to the ethylene / propylene random copolymer layer, the melting point of the layer 16 including the ethylene / propylene random copolymer layer can be increased to 140 to 180 ° C. As a result, in the lithium ion battery, the temperature inside the outer package 10 rises due to overcharge or the like, and the metal terminals, electrodes, and current collectors generate heat, and the metal terminals of the melt-extruded polypropylene layer 9 that is the innermost layer Even when the four sandwiched portions are melted, the layer 16 including the ethylene / propylene random copolymer layer does not melt easily because of its high melting point. Therefore, it can prevent that a metal terminal, an electrode, a collector, and metal foil contact and short-circuit.

  Next, the melt-extruded polypropylene layer 9 will be described. By additionally processing the polypropylene layer 9 melt-extruded on the inner layer side of the layer 16 including the ethylene / propylene random copolymer layer, the heat seal temperature can be lowered while ensuring a predetermined seal strength. This is presumably because the melt-extruded polypropylene layer 9 has a lower melting point and higher fluidity than the ethylene-propylene random copolymer layer of the heat seal layer 14 when heated.

  At this time, if a melt-extruded polypropylene layer 9 having a melt index of 5 g / 10 min or more and 30 g / 10 min or less is used, sufficient seal strength can be secured at the seal temperature.

  By using a melt-extruded polypropylene layer 9 having a melting point of 120 to 150 ° C., low-temperature sealability can be ensured. Further, when the lithium ion battery main body is sealed in the outer casing 10 and the metal terminal of the battery main body is sandwiched and sealed in a state of protruding outward, the melt-extruded polypropylene layer 9 has high fluidity so that the metal terminal is sandwiched. The opening of the outer package 10 is hermetically sealed so as to cover the entire portion. 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 the polypropylene layer 9 having a melting point lower than 120 ° C. is used, there is a possibility that the heat sealing 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.

  When the laminate 10 is embossed, the melt-extruded polypropylene layer 9 has a lower coefficient of dynamic friction than the ethylene / propylene random copolymer layer, so that the sliding property between the male mold and the heat seal layer is improved. 14 can be prevented from being wrinkled or broken, and can be stably press-formed.

  At this time, by adding a lubricant such as erucic acid to the molten polypropylene, the dynamic friction coefficient of the polypropylene layer to be melt-extruded is further reduced, and press molding can be performed more stably.

  Next, the slip layer 11 will be described. As the slip agent for forming the slip layer 11, a polydimethylsiloxane block copolymer produced by copolymerizing a vinyl copolymer with an azo group-containing polydimethylsiloxane amide as an initiator is used.

  A slip agent using a polydimethylsiloxane block copolymer is deposited and deposited on a molding die or a guide roll when continuously molding using a conventional fatty acid amide slip agent. There is no need to bake at a high temperature when a slip agent deposited on the film adheres to the film, or when a coating such as a slip agent of a fluororesin layer or a silicone resin layer is applied. Therefore, it is a material suitable as a slip agent.

The polydimethylsiloxane block copolymer has the following structure.
[1]. (A ¹ * a ² ) _l
[2]. a ¹ * (a ¹ * a ² ) _m
[3]. a ² * (a ¹ * a ² ) _n
Here, l, m, and n are integers of 1 to 10, a ¹ is a polydimethylsiloxane moiety represented by the following formula (Formula 1),

a ² is a vinyl polymer portion. First, a polymer initiator method is applied to synthesize the polydimethylsiloxane block copolymer. In the above polymer initiator method, for example, if a vinyl short monomer copolymerizable with a polymer having a polydimethylsiloxane moiety represented by the following formula (Chemical Formula 2) is copolymerized, the efficiency is improved. A block copolymer can be produced well.

  Further, if a polymeric initiator such as a peroxide type polymer initiator or an azo type polymer initiator is used, the polymerization can be carried out in two stages. For example, when an azo type polymer initiator is used, the polymerization is a two-stage polymerization represented by the following formulas (Chemical Formula 3) and (Chemical Formula 4):

Here, m, n, n ′ and l are integers of 1 or more, M ₁ is a macromonomer represented by the following formulas (Chemical Formula 5) and (Chemical Formula 6),

Here, M ₂ is a vinyl monomer copolymerizable with M ₁ , and, for example, R can be represented by the following formula (Formula 7).

and so on.

  Next, examples of the copolymerizable vinyl monomer used in the polymer initiator method include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, iso-propyl ( (Meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, t-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, Aliphatic or cyclic (meth) acrylate such as stearyl (meth) acrylate, theuryl (meth) acrylate, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, n-butyl vinyl ether, iso-butyl vinyl ether, etc. Nyl ethers, styrenes such as styrene and α-methylstyrene, nitrile monomers such as acrylonitrile and methacrylonitrile, aliphatic vinyls such as vinyl acetate and vinyl propionate, vinyl chloride, vinylidene chloride, vinyl fluoride, and fins , Dienes such as chloroprene, butadiene, acrylic acid, methacrylic acid, itaconic acid, maleic acid, maleic anhydride, α, β-unsaturated carboxylic acid such as crotonic acid, atropic acid, citraconic acid, acrylamide, methacrylamide, Amides such as N, N-methylolacrylamide, N, N-dimethylacrylamide, diacetoneacrylamide, methylacrylamide glycolate methyl ether, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminomethyl (Meta) Acry , Amino group-containing monomers such as N, N-dimethylaminopropyl (meth) acrylate, epoxy group-containing monomers such as glycidyl (meth) acrylate and glycidyl allyl ether, 2-hydroxyethyl (meth) acrylate, Reaction products of 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl acrylate, allyl alcohol, Cardura E with acrylic acid, methacrylic acid, itaconic acid, maleic acid, crotonic acid, etc., other vinylpyrrolidone, vinylpyridine, vinylcarbazole Further, vinyl monomers having hydrolyzable silyl groups include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, and γ-methacryloxy. Propyl methyl diethoxy silane, .gamma.-methacryloxypropyl methoxy silane, vinyl trimethoxy silane, can be used silane coupling agents such as vinyltriethoxysilane. The above monomers may be used alone or in combination of two or more. In this stage, (meth) acrylate is used in the meaning of acrylate or methacrylate.

  As a method for producing the polydimethylsiloxane block copolymer, it is produced by adding a vinyl monomer copolymerizable with the above-described polymer initiator into which polydimethylsiloxane is introduced and polymerizing it. The polymerization reaction is usually performed in a solution. In the above polymerization reaction, aromatic hydrocarbon solvents such as toluene and xylene, ketone solvents such as acetone, methyl ethyl ketone and methyl isobutyl ketone, ester solvents such as ethyl acetate, propyl acetate, butyl acetate and isobutyl acetate, methanol, It can be used alone or as a mixed solvent such as alcohol solvents such as ethanol, isopropanol, butanol and isobutanol.

  In the above polymerization reaction, a known polymerization initiator such as benzoyl peroxide, lauryl peroxide, cumene hydroperoxide, dicumyl peroxide or the like may be used in combination as necessary. . In the polydimethylsiloxane block copolymer thus obtained, the siloxane content ratio is 1 to 60% by weight, preferably 5 to 40% by weight, and the content ratio of other copolymerizable vinyl monomers is 99 to 40%. It is desirable that the vinyl monomer has an OH group or an epoxy group contained therein, preferably 95% to 60% by weight. The polydimethylsiloxane block copolymer thus obtained has a high compatibility with other synthetic resins and is extremely effective as a compatibilizer. For example, silicone resin, polyvinyl acetoacetal, polyvinyl butyral, etc. A synthetic resin such as the above may be used as a mixture.

When a polydimethylsiloxane block copolymer is used as a slip agent, a resin solution containing the polydimethylsiloxane block copolymer obtained by the above polymerization reaction in a solution is applied by a known coating method such as a gravure printing method. The slip agent layer 11 can be obtained by applying to the surface of the base material layer and drying. The coating amount of the polydimethylsiloxane block copolymer is 0.05 g / m ² or more after drying, preferably 0.08 to 0.5 g / m ² , more preferably 0.1 to 0.2 g / m. m ² . Is less than the coating amount is 0.05 g / m ^2, there is no stable sliding properties can be obtained (slipperiness varies) risk, even at 0.5 g / m ² greater, although the sufficient effect of the sliding property is obtained This is not preferable in terms of cost effectiveness.

  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.

  A chemical conversion treatment is performed on both surfaces of aluminum (thickness 100 μm), 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 treatment is applied to the other chemical conversion treatment surface. Modified polypropylene (hereinafter abbreviated as acid-modified PP) is melt-extruded at a thickness of 15 μm and a sealant film made of an ethylene / propylene random copolymer film (thickness: 30 μm) is laminated to obtain a battery packaging material according to the present invention 1. It was.

At this time, in each chemical conversion treatment, an aqueous solution composed of a phenol resin, a chromium fluoride compound, and phosphoric acid was used as a treatment solution, and the coating was applied by a roll coating method and baked under a condition where the film temperature was 180 ° C. or higher. The amount of chromium applied was 10 mg / m ² (dry weight).

  Further, a laminate obtained by using a homopolypropylene film (thickness: 30 μm) as a sealant film instead of the ethylene / propylene random copolymer film by the same method as above was used as Comparative Example 1.

  Next, the battery packaging material according to the present invention 1 and the comparative example 1 is cut into 60 mm (MD direction) × 120 mm (TD direction) strip pieces, the two strip pieces are overlapped, and two opposing sides are 7 mm. A bag with an opening on one side was created by heat sealing with a width. At this time, the heat sealing was performed under conditions of a surface pressure of 1.0 MPa, a sealing temperature of 190 ° C., and a sealing time of 3.0 seconds.

  FIG. 6 is a schematic plan view of the lithium ion battery in this example. As shown in FIG. 6, in the case of a four-side seal pouch-type exterior body, the case where it is folded 180 ° so that the BB ′ on the heat seal section can be folded is used as a method for evaluating the insulation at the exterior body folded portion. The direction fold was performed, and the case where the sheet was folded 180 ° so that a fold line was formed at AA ′ was defined as the MD fold. The lithium ion battery main body was sealed from the opening, the electrolyte was put and hermetically sealed, and then the TD direction folding and the MD direction folding were repeated five times.

  Next, the positive electrode terminal 26a was set in the electrolytic solution so that the tip of the negative electrode terminal 26b reached the aluminum foil of the outer package, and a voltage of 25V was applied by the voltmeter 27 for 5 seconds to measure the resistance value. In this evaluation method, six samples according to the present invention 1 and comparative example 1 were prepared, and the TD direction folding and the MD direction folding were each evaluated three times. The results are shown in Table 1.

[Table 1]

  As described above, as is clear from Table 1, when a crease was made in the MD direction, which is the orientation direction of the heat seal resin, cracks did not occur regardless of the type of the heat seal resin. It was found that when a crease was made in the TD direction that is perpendicular to the direction, cracks occurred in the heat seal layer using the unstretched polypropylene film, and the aluminum foil was energized. On the other hand, it was found that when an ethylene / propylene random copolymer film having excellent toughness was used for the heat seal layer, cracks did not occur and insulation of the outer package was ensured.

  Next, in Example 2, in the heat seal layer composed of a multilayer film, the seal strength that changes with time depending on the melting point and the melt index of the formed film was evaluated.

  First, both surfaces of aluminum (thickness: 100 μm) are subjected to chemical conversion treatment, and a biaxially stretched nylon film (thickness: 25 μm) is pasted on one chemical conversion treatment surface by a dry laminating method via a two-component curable polyurethane adhesive. Combined. Next, acid-modified PP (thickness 15 μm) is melt-extruded on the other chemical conversion treatment surface, and a three-layer coextruded film (thickness) comprising an ethylene / propylene random copolymer film and an ethylene / propylene block copolymer film sandwiched therebetween. 30 μm) was laminated, and a polypropylene layer was melt-extruded to a thickness of 20 μm on the surface of the three-layer coextruded film layer to obtain a battery packaging material according to the present invention 2.

  The melting point Mp and the melt index Mi of the three-layer coextruded film constituting the heat seal layer and the melt-extruded polypropylene layer are Mp = 143 ° C., Mi = 1.0 g / 10 min for ethylene / propylene random copolymer film, ethylene The propylene block copolymer film has Mp = 165 ° C., Mi = 15 g / 10 min, and the melt-extruded polypropylene has Mp = 139 ° C., Mi = 20 g / 10 min. Therefore, the heat-sealed layer constituting the battery packaging material according to the second aspect of the present invention is provided with a melt-extruded polypropylene having the lowest melting point and the highest melt index as the innermost layer.

  Further, a battery packaging material in which a polypropylene layer was not melt-extruded on the three-layer coextruded film was prepared as Comparative Example 2.

Moreover, the chemical conversion treatment layer was coated with a treatment liquid composed of a phenol resin, a chromium fluoride compound, and phosphoric acid by a roll coating method, and baked under conditions where the film temperature was 90 ° C. or higher. The amount of chromium applied was 10 mg / m ² (dry weight).

  Next, the battery packaging material according to the present invention 2 and comparative example 2 is cut into strips of 60 mm (MD direction) × 120 mm (TD direction), folded in half in the TD direction, and the two opposing sides are 7 mm. A bag having an opening on one side is prepared by heat sealing with a width, and 3 g of electrolytic solution [mixed solution of lithium hexafluorophosphate [ethylene carbonate / diethyl carbonate / dimethyl carbonate = 1/1/1 (volume Ratio)] and a 1 mol / L lithium hexafluorophosphate solution] is injected, and the opening is 7 mm wide, the seal temperature is 190 ° C., the surface pressure is 1.0 MPa, and the seal time is 3.0 seconds. Heat-sealed and cut the heat-sealed part of the opening of the sample stored for 0, 72, 168, 336, 504 hours in a 60-degree thermostatic oven into a 15 mm wide strip and pull it Test machine (manufactured by Shimadzu Corporation, AGS-50D (trade name)) pulled at at 300 mm / min, the seal strength at each storage time was measured the results are summarized in Graph 1. The unit of seal strength is N / 15 mm width.

[Graph 1]

  Next, the seal part of the sample concerning this invention 2 and the comparative example 2 heat-sealed on the said conditions is cut | disconnected, the cross-sectional view is observed with a microscope, The cross-sectional photograph is shown in FIG. 7A is a cross-sectional photograph of the exterior body according to Comparative Example 2, and FIG. 7B is a cross-sectional photograph of the exterior body according to the first aspect of the present invention.

  As described above, from the results shown in [Graph 1], it was found that the exterior body according to the second aspect of the present invention maintains a high seal strength even when time passes as compared with the exterior body according to Comparative Example 2. Further, from the cross-sectional photograph of FIG. 7, the vicinity of the seal part of the exterior body according to the present invention 2 forms a parabolic surface and is stably sealed, whereas the vicinity of the inner edge of the seal part of the exterior body according to Comparative Example 2 As a result, a resin reservoir was formed, and it was confirmed that the heat seal layer was cut. Therefore, it can be presumed that this resin pool is one of the causes that the seal strength of the exterior body according to Comparative Example 2 is lower than the seal strength of the exterior body according to the present invention 2.

  TECHNICAL FIELD The present invention relates to a battery packaging material suitable for use as a power source for energy storage or electric vehicles and used in a lithium ion battery having high durability and safety.

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. These are sectional drawings of the packaging material for batteries which concerns on the flow of the heat seal layer at the time of heat sealing which concerns on this invention. These are the schematic perspective views which show the process of embossing the packaging material for batteries of this invention. These are the schematic plan views of the lithium ion battery in the Example of this invention. These are the cross-sectional photographs of the exterior body in Example 2. FIG. 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. These are the schematic diagrams which show the conventional embossing process.

Explanation of symbols

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 7 Clamping part 8 Acid-modified polyolefin layer 9 Melt-extruded propylene layer 10 Exterior body 10a Near edge of seal part 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 Heat Seal Layer 15 Adhesive Layer 16 Ethylene / Propylene Random Copolymer Layer 19 Plastic Case 20 Press Molded Part 21 Male Part 22 Female 22a Side Wall Part 23 Cavity 24 Second Polypropylene Layer 25 First Polypropylene Layer 25a Resin Pool

Claims (8)

In a battery packaging material in which a base material layer that is an outermost layer, a metal foil layer having a chemical conversion treatment layer on at least one surface, an acid-modified polyolefin layer, and a heat seal layer that is an innermost layer are sequentially laminated,
The metal foil layer is an aluminum foil having a thickness of 80 μm or more and 120 μm or less,
The battery packaging material, wherein the heat seal layer comprises a layer including an ethylene / propylene random copolymer film layer.   The second polypropylene layer having a lower melting point and a higher melt index than the ethylene / propylene random copolymer film layer is provided on the inner layer side of the layer including the ethylene / propylene random copolymer film layer. Battery packaging material.   The battery packaging material according to claim 2, wherein the second polypropylene layer is a melt-extruded polypropylene layer.   The battery packaging material according to claim 3, wherein the melt-extruded polypropylene layer has a melting point of 120 ° C or higher and 150 ° C or lower.   5. The battery packaging material according to claim 3, wherein the melt-extruded polypropylene layer has a melt index of 5 g / 10 min to 30 g / 10 min.   6. The battery packaging material according to claim 2, wherein a melting point of the heat seal layer excluding the second polypropylene layer is 140 ° C. or higher and 180 ° C. or lower.   The battery packaging material according to any one of claims 2 to 6, wherein a lubricant is added to the resin of the second polypropylene layer.   The battery packaging material according to any one of claims 1 to 7, wherein the surface of the base material layer is composed of a stretched polyester or a polybutylene terephthalate film.