JP2013084607A - Battery packaging material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a battery packaging material excellent in productivity, low temperature sealing performance, sealing performance, and resistance to contents while adhesion strength between a metal foil layer and a heat seal layer is ensured in a laminate laminated by a dry lamination method.SOLUTION: A battery packaging material is formed by laminating in order at least a substrate layer 12 of the outermost layer, a barrier layer 13 made of an aluminum foil, a chemical conversion treatment layer 13a, a fluorine-based resin layer 8 and a heat seal layer 14 of the innermost layer. The heat seal layer 14 is configured of at least a first polypropylene layer and a second polypropylene layer, and the second polypropylene layer is arranged on more to the innermost layer side than the first polypropylene layer and has a lower melting point and a higher melt index than those of the first polypropylene layer.

Description

  The present invention relates to a battery packaging material that exhibits stable sealing properties, moisture resistance, and moldability with the packaging material.

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 outermost layer, a barrier layer, a heat seal layer in the innermost layer, and an adhesive layer that adheres the respective 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. 6A is a perspective view of a pouch-type lithium ion battery using the pillow-shaped exterior body 10, and FIG. 6B is a perspective view showing a state in which the lithium ion battery is disassembled. As shown in FIGS. 6A and 6B, 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. 7 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 10 including a tray 10a and a sheet 10b in 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 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. 8 shows the structure of a male type 21 and female type 22 press machine showing molding in an embossed type. 8A is a perspective view of the outer package 10 before pressing, and FIG. 8B is a perspective view of the outer package formed into a concave shape after pressing. Here, in the case of the embossed type exterior body 10, as shown in FIG. 8A or FIG. 8B, 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, as described above, the layer structure of the laminate is composed of a base material layer, a barrier layer made of a metal foil such as aluminum, and an inner heat seal layer. A lithium hexafluorophosphate solution is used, which reacts with water vapor to generate hydrofluoric acid, which permeates the inner layer of the laminate, reduces the adhesion between the metal foil and the inner layer, and peels off. Therefore, there is a problem that the battery life is shortened, and the laminate used for the lithium battery needs to block water vapor entering from the outside air. For this reason, the inner layer side of the metal foil needs to be made of a material having less water vapor transmission, and the total thickness of the inner layer side of the metal foil is also surely sealed from the meaning of suppressing water vapor transmission from the end face as much as possible. It is designed to be thick enough to be able to.

  The lamination method of the metal foil and the inner layer 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 method is excellent in productivity, the water vapor 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. It reacts with the electrolytic solution to produce hydrofluoric acid, which has the problem of causing the metal foil and the inner layer to peel off over time, and because the thermal lamination method does not use an adhesive, Water vapor transmission can be much better than dry lamination, but in terms of productivity, dry lamination There is a problem that it is inferior compared to the ® down method.

  Therefore, in order to solve these problems, adopt a highly productive dry lamination method, and develop a laminate having an excellent water vapor barrier property, conventionally, an aminated phenol polymer on the inner layer side surface of the metal foil layer, Adhesion with an adhesive layer using a fluorine-based resin formed by a fluorine-based polyol and an isocyanate-based curing agent provided with a chemical conversion layer formed by a chemical conversion treatment liquid containing a chromium trioxide compound, a phosphorus compound, and carbodiimide The laminated body (patent document 1) which raised the intensity | strength was proposed.

Japanese Patent Application No. 2005-285728

  However, when the laminate proposed in Patent Document 1 is used as a battery packaging material as shown in FIGS. 6 and 7, a low-temperature seal cannot obtain a sufficient seal strength, and a seal is required to increase the seal strength. It was necessary to lengthen the time. Therefore, although the laminate of Patent Document 1 can efficiently produce a laminate having excellent water vapor barrier properties by the dry lamination method, there is a problem that the productivity of lithium batteries is inferior as a battery packaging material. .

  In addition, after heat sealing, the resin is not sufficiently filled in the metal terminal holding portion of the laminate, and sufficient sealing performance may not be ensured. As a result, water vapor may enter from the periphery of the metal terminal and cause delamination of the laminate.

  Therefore, in view of the above problems, the present invention has productivity while maintaining the adhesive strength between the metal foil layer and the heat seal layer in the laminate laminated by the dry lamination method, and has a low temperature sealing property and a hermetic sealing property. An object of the present invention is to provide a battery packaging material having excellent content resistance.

  In order to achieve the above object, the first configuration of the present invention is that at least a base material layer that is an outermost layer, a barrier layer made of aluminum foil, a chemical conversion treatment layer, a fluorine-based resin layer, and a heat seal layer that is an innermost layer are at least sequentially. In the laminated battery packaging material, the heat seal layer includes at least a first polypropylene layer and a second polypropylene layer, and the second polypropylene layer is disposed on the innermost layer side of the first polypropylene layer, and the first A battery packaging material having a lower melting point and a higher melt index than a polypropylene layer.

  The battery packaging material of the second configuration of the present invention is an adhesive comprising a fluorine-containing copolymer in which the fluorine-based resin layer contains a hydroxyl group and a curing agent that reacts with the hydroxyl group of the fluorine-containing copolymer. The first polypropylene layer is an unstretched polypropylene layer, and the second polypropylene layer is a melt-extruded polypropylene layer.

  The battery packaging material of the third 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 according to the fourth aspect 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.

  In the battery packaging material of the fifth configuration of the present invention, the chemical conversion treatment layer is formed of a chemical conversion treatment solution containing an aminated phenol polymer, a trivalent chromium compound, a phosphorus compound, and carbodiimide. Features.

  The battery packaging material according to the sixth aspect of the present invention is characterized in that the unstretched polypropylene layer has a melting point of 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 the unstretched polypropylene layer is a layer containing an ethylene / propylene random copolymer layer.

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

  The battery packaging material of the ninth configuration of the present invention is characterized in that a coating layer made of a slip agent is provided on the surface of the base material layer.

  According to the first configuration of the present invention, the heat seal layer is composed of a plurality of polypropylene layers, the second polypropylene layer having a low melting point and a high melt index is disposed on the innermost layer side, and the heat seal layer is overlapped and sealed. When the part is heated and pressurized, the second polypropylene layer melts with a certain viscosity earlier than the other polypropylene layers and is extruded toward the inside of the outer package. For this reason, after heat sealing, a smooth curved surface is formed by the second polypropylene layer in the vicinity of the boundary between the seal portion and the exterior body, and when the vicinity of the boundary portion is bent or gas is generated inside the exterior body, the exterior body expands. Even in this case, stress concentration in the portion can be prevented and stable seal strength can be ensured.

  According to the second configuration of the present invention, by providing a fluorine-based adhesive having a low water vapor permeability between the chemical conversion treated surface of the aluminum foil and the heat seal layer, a water vapor barrier property, an electrolytic solution can be obtained by a dry laminating method. Laminates excellent in heat resistance and corrosion resistance can be produced efficiently.

  Further, by providing a melt-extruded polypropylene layer on the surface of the unstretched polypropylene layer, the sealing temperature can be lowered while maintaining the sealing strength. Thereby, the lithium battery main body can be efficiently sealed at a low temperature in the battery packaging material, and the productivity of the lithium battery can be improved.

  In addition, the melt-extruded polypropylene layer having high fluidity is melt-sealed during heat sealing so as to hermetically seal so as to cover the entire metal terminal sandwiched portion, and blocks external water vapor that permeates from the metal terminal sandwiched portion. The production of hydrofluoric acid due to the reaction between water and water vapor can be suppressed.

  According to the third configuration of the present invention, the melt index of the polypropylene layer melt-extruded on the surface of the unstretched polypropylene layer, which is a heat seal layer, is set to 5 g / 10 min or more and 30 g / 10 min or less, so that the sealing strength and hermetic sealing performance are achieved. Can be increased.

  According to the fourth configuration of the present invention, the heat sealing temperature is maintained while maintaining the sealing strength by setting the melting point of the polypropylene layer melt-extruded to the surface of the unstretched polypropylene layer, which is a heat sealing layer, to 120 ° C. or more and 150 ° C. or less. Can be lowered.

  According to the fifth configuration of the present invention, the chemical conversion treatment layer is formed of a chemical conversion treatment solution containing an aminated phenol polymer, a trivalent chromium compound, a phosphorus compound, and a carbodiimide, thereby bonding the aluminum foil and the adhesive layer. Increase strength. In addition, the electrolyte can be stable over time. Here, since the adhesive layer is composed of a layer mainly composed of a fluorine-based resin, the water vapor barrier property has a further excellent performance. Moreover, the battery packaging material can be manufactured with high productivity by laminating by the dry lamination method.

  According to the sixth configuration of the present invention, since the melting point of the unstretched polypropylene layer is 140 ° C. or more and 180 ° C. or less, an abnormal temperature rise occurs inside the exterior body due to overcharge or the like, and the metal terminals and electrodes inside the exterior body Even when the current collector generates heat and the innermost melt-extruded polypropylene layer melts, the unstretched polypropylene layer does not melt, preventing contact between the metal terminal, electrode, current collector and the metal foil layer. . Thereby, generation | occurrence | production of an internal short circuit can be suppressed.

  According to the seventh configuration of the present invention, the heat-sealed portion of the outer package may be folded to secure a storage space for the lithium ion battery, but the unstretched polypropylene layer includes an ethylene / propylene random copolymer layer having excellent toughness. Thereby, generation | occurrence | production of the crack in the said bending 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 eighth configuration of the present invention, when the stretched polyester or layer is provided on the surface of the base material layer, the outer surface of the exterior body is whitened when the electrolyte leaks to the outside of the battery and adheres to the exterior body surface. Insulation deterioration can be prevented.

  According to the ninth configuration of the present invention, by applying and coating a slip agent on the surface of the base material layer, slipping between the base material layer surface and the mold is ensured during emboss molding, and stable press molding is performed. be able to.

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 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 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. These are the schematic diagrams which show the conventional embossing process.

  The present invention is a packaging material for lithium ion batteries having excellent water vapor barrier properties, electrolytic solution resistance, corrosion resistance, hermetic sealing properties, low temperature sealing properties, and the like. 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.6, FIG.7, FIG.8 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 10 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 barrier layer 13 made of aluminum foil therebetween.

  The aluminum foil layer 13 and the heat seal layer 14 are firmly bonded by a dry laminating method using a chemical conversion treatment layer 13a and a fluorine resin layer 8 provided on the surface of the aluminum foil 13, and are laminated. 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. The surface of the base material layer 12 is coated with a slip agent to form a slip layer 11. In the heat seal layer 14, the polypropylene layer 9 melt-extruded on the surface of the unstretched polypropylene layer 16 is additionally processed.

  At this time, by forming the chemical conversion treatment layer 13a with a chemical conversion treatment solution containing an aminated phenol polymer, a trivalent chromium compound, a phosphorus compound, and carbodiimide, the adhesive strength between the aluminum foil 13 and the heat seal layer 14 is increased. The battery packaging material becomes stable with respect to the electrolyte over time. Moreover, by providing the fluororesin layer 8 as an adhesive layer, it also has a performance excellent in water vapor barrier properties. Furthermore, since it can be laminated | stacked by the dry lamination method excellent in productivity, it can manufacture efficiently.

  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 slip layer 11, the chemical conversion layer 13a, the fluorine resin layer 8, 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 in a state where the metal terminal 4 is sandwiched by the innermost melt-extruded polypropylene layer 9.

  Usually, when the heat seal layer 14 is heat sealed, it is necessary to apply heat and pressure near the melting point of the unstretched polypropylene layer 16 to the seal portion. However, by providing the melt-extruded polypropylene layer 9 on the surface of the unstretched polypropylene layer 16, heat sealing can be performed at a temperature lower than the melting point of the unstretched polypropylene layer 16.

  At this time, when a melt-extruded polypropylene layer 9 having a melt index of 5 g / 10 min to 30 g / 10 min and a melting point of 120 ° C. to 150 ° C. is used, sufficient sealing strength is secured. The sealing temperature can be lowered.

  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.

  Further, 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 come into contact with each other and are short-circuited. May cause.

  However, if the melting point of the unstretched polypropylene layer 16 between the metal foil 13 and the melt-extruded polypropylene layer 9 is 140 ° C. or more and 180 ° C. or less, even when the melt-extruded polypropylene layer 9 is melted, it is not stretched. Since the polypropylene layer 16 has a high melting point, it does not melt easily. Therefore, it can prevent that the metal terminal 4, an electrode, a collector, and the metal foil 13 contact and short-circuit.

  FIG. 3A is a cross-sectional view of a lithium ion battery 1 encapsulated using the battery packaging material according to the present invention, and FIGS. 3B and 3C are the vicinity of the seal portion 10a in FIG. It is sectional drawing which expands and shows. Here, FIG. 3 shows only the metal foil layer 13 and the heat seal layer 14, and the other layers are omitted for explanation. Further, the heat seal layer 14 is assumed to be composed of two layers of the second polypropylene layer 24 and the first polypropylene layer 25 arranged on the innermost layer side, and the second polypropylene layer 24 has been described with reference to FIGS. The melt-extruded polypropylene layer 9 and the first polypropylene layer 25 hit the unstretched polypropylene layer 16.

  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 time-lapse laminar strength after the heat seal differs depending on the arrangement of the films. That is, by disposing a film having a lower melting point and a higher melt index than the other films on the innermost layer side, the vicinity of the sealed portion 10a after sealing can be sealed in a stable shape with no distortion or incision.

  FIG. 3B is a diagram showing 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. 3B). For this reason, two substantially V-shaped cuts are formed in the vicinity of the seal portion 10a (see FIG. 3B). Thereby, when the force which peels an exterior body up and down acts, the fracture | rupture of the heat seal layer 14 will generate | occur | produce from the said notch | incision, and the fall of a seal strength will pose a problem.

  FIG. 3C 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 sealing 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 to the inside of the exterior body ahead of the first polypropylene layer 25. (See arrow in FIG. 3 (c)).

  For this reason, a smooth curved surface is formed by the second polypropylene layer 24 in the vicinity of the seal portion 10a after heat sealing. Therefore, stable seal strength can be ensured as compared with the vicinity of the seal portion 10a shown in FIG.

  Fig.4 (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. 4B 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 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.

  FIG. 5A is a schematic perspective view showing the lithium ion battery 1, and FIG. 5B 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. 5C 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 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.

  Moreover, the electrolyte inside the outer package 10 may come into contact with the metal foil layer 13 due to this cracking, 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.

  However, when the unstretched polypropylene layer 16 is made of an ethylene / propylene random copolymer layer having excellent toughness, cracking of the unstretched polypropylene layer 16 can be prevented and the insulation of the outer package 10 can be ensured.

  Next, each layer of the outer package 10 shown in FIG. 1 will be specifically described. The base material layer 12 needs to have a spreadability that can withstand a press during embossing. Generally, it consists of a stretched polyester or nylon film. At this time, examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, copolymerized polyester, and polycarbonate. Examples of nylon include polyamide resin, that is, nylon 6, nylon 6,6, a copolymer of nylon 6 and nylon 6,6, nylon 6,10, polymetaxylylene adipamide (MXD6), and the like.

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 polyester, 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.

  The barrier layer 13 is a layer for preventing water vapor from entering the inside of the lithium ion battery from the outside, stabilizing the pinhole and processability (pouching, embossing formability) of the barrier layer alone, and Examples of the barrier layer 13 include a metal having a thickness of 15 μm or more, such as aluminum or nickel, or a film on which an inorganic compound such as silicon oxide or alumina is deposited. 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 barrier layer 13 is: By making the iron content 0.3 to 9.0% by weight, preferably 0.7 to 2.0% by weight, the aluminum has good extensibility compared with aluminum not containing iron, and the exterior The generation of pinholes due to bending as a body is reduced, and the side wall can be easily formed when the embossed type 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 barrier layer 13.

  Next, the chemical conversion treatment layer 13a will be described. The chemical conversion treatment layer 13 a is formed on the surface of the aluminum foil 13 on the fluorine resin layer 15 side. Further, the chemical conversion treatment layer 13a can firmly bond the aluminum foil 13 and the fluorine resin layer 15 and prevent delamination of the aluminum foil 13 and the heat seal layer 14.

  Specifically, by preventing the delamination between the aluminum 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 the water vapor of 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 formed by chromium conversion treatment such as chromic chromate treatment, phosphoric acid chromate treatment, coating type chromate treatment, or non-chromium (coating type) chemical conversion treatment such as zirconium, titanium, zinc phosphate, etc. Although it is formed on the surface of the foil 13, it is firmly bonded to the fluororesin 8, is capable of continuous processing and does not require a water washing step, and can reduce processing costs. To coating type chemical conversion treatment, in particular, treatment with a treatment solution containing an aminated phenol polymer, a trivalent chromium compound, a phosphorus compound, and a carbodiimide (resin) is most preferred.

First, the aminated phenol polymer will be described. A well-known thing can be widely used as an aminated phenol polymer, for example, it consists of a repeating unit represented by the following formula (Chemical Formula 1), (Chemical Formula 2), (Chemical Formula 3), and (Chemical Formula 4). Mention may be made of aminated phenol polymers. X in the formula represents a hydrogen atom, a hydroxyl group, an alkyl group, a hydroxyalkyl group, an allyl group or a benzyl group. R ₁ and R ₂ represent a hydroxyl group, an alkyl group, or a hydroxyalkyl group, and may be the same group or different groups.

In the following formulas (Chemical Formula 1) to (Chemical Formula 4), examples of the alkyl group represented by X, R ₁ and R ₂ include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, and isobutyl. And a straight chain or branched alkyl group having 1 to 4 carbon atoms such as a tert-butyl group. Examples of the hydroxyalkyl group represented by X, R ₁ and R ₂ include a hydroxymethyl group, a 1-hydroxyethyl group, a 2-hydroxyethyl group, a 1-hydroxypropyl group, a 2-hydroxypropyl group, 3- C1-C4 straight or branched chain in which one hydroxy group such as hydroxypropyl group, 1-hydroxybutyl group, 2-hydroxybutyl group, 3-hydroxybutyl group, 4-hydroxybutyl group is substituted An alkyl group can be mentioned. In the following formulas (Chemical Formula 1) to (Chemical Formula 4), X is preferably any one of a hydrogen atom, a hydroxyl group, and a hydroxyalkyl group.

In addition, the aminated phenol polymer represented by the following formulas (Chemical Formula 1) and (Chemical Formula 3) has an amino acid content of about 80 mol% or less, preferably about 25 to about 55 mol% of repeating units. It is a modified phenol polymer. The number average molecular weight of the aminated phenol polymer is preferably about 500 to about 1 million, more preferably about 1000 to about 20,000. An aminated phenol polymer is produced, for example, by polycondensing a phenol compound or naphthol compound with formaldehyde to produce a polymer comprising repeating units represented by the following (Chemical Formula 1) to (Chemical Formula 3). It is produced by introducing a water-soluble functional group (—CH ₂ NR ₁ R ₂ ) into the coalescence using formaldehyde and an amine (R ₁ R ₂ NH). The aminated phenol polymer can be used singly or in combination of two or more.

Next, the trivalent chromium compound will be described. As the trivalent chromium compound, known compounds can be widely used. For example, chromium nitrate, chromium fluoride, chromium sulfate, chromium acetate, chromium oxalate, chromium biphosphate, chromic acetyl acetate, chromium chloride, sulfuric acid Potassium chromium etc. can be mentioned, Preferably they are chromium nitrate and chromium fluoride.

  Next, a phosphorus compound is demonstrated. As a phosphorus compound, a well-known thing can be used widely, For example, condensed phosphoric acids, such as phosphoric acid and polyphosphoric acid, these salts, etc. can be mentioned. Here, as said salt, alkali metal salts, such as ammonium salt, sodium salt, potassium salt, can be mentioned, for example.

  Next, carbodiimide (resin) will be described. The carbodiimide (resin) is generally produced by a condensation reaction of aromatic or aliphatic diisocyanate in the presence or absence of a terminal blocking agent in the presence of a carbodiimidization catalyst and decarbonization. A polycarbodiimide represented by the formula (Chemical Formula 5) produced by a condensation reaction involving decarbonization in the presence or absence of an aliphatic diisocyanate and a terminal blocking agent in the presence of a carbodiimidization catalyst An aqueous carbodiimide resin represented by the formula (Chemical Formula 6) in which polyethylene glycol is added to the resin can be used. The carbodiimide (resin) has a number average molecular weight of 1200 to 2500, preferably 1800 to 2200, as measured by GPC.

And as the chemical conversion treatment layer 13a formed using the processing liquid containing an aminated phenol polymer, a trivalent chromium compound, a phosphorus compound, and a carbodiimide (resin), the aminated phenol polymer is about 1 m ^2. 1 to about 200 mg, trivalent chromium compound is about 0.5 to about 50 mg in terms of chromium, phosphorus compound is about 0.5 to about 50 mg in terms of phosphorus, and carbodiimide (resin) is about 0.5 to about 200 mg The aminated phenol polymer is about 5 to about 150 mg, the trivalent chromium compound is about 1.0 to about 40 mg in terms of chromium, and the phosphorus compound is about 1.0 to about in terms of phosphorus. More preferably, about 40 mg and carbodiimide (resin) are contained in a proportion of about 1.0 to about 150 mg. In this case, the drying temperature is 150 to 250 ° C., preferably 170 to 250 ° C., and the heat treatment (baking treatment) is appropriate.

  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 aluminum 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.

  Next, the fluorine resin layer 8 will be described. The fluororesin layer 8 can bond the aluminum foil 13 and the heat seal layer by a dry lamination method. Further, since the fluorine resin layer 8 can suppress the water vapor permeability to the same level as that of the thermal lamination method, it is possible to provide a laminate excellent in physical properties such as electrolytic solution resistance and corrosion resistance with high productivity. .

  The fluorine-based resin layer 8 is a layer formed of a fluorine-containing copolymer containing a hydroxyl group and a curing agent that reacts with the fluorine-containing copolymer. The fluorine-containing copolymer containing a hydroxyl group is soluble in an organic solvent and has a crosslinking site in the molecule, and examples of the crosslinking site include an alcoholic hydroxyl group (OH group).

As such a fluorine-containing copolymer, for example,
1) a fluoroolefin monomer represented by the formula: CF ₂ = CFX [wherein X is a fluorine atom, a hydrogen atom or a trifluoromethyl group]
2) β-methyl-substituted α-olefin monomer represented by the formula: CH ₂ = CR (CH ₂ ), wherein R is an alkyl group having 1 to 8 carbon atoms,
3) a hydroxyl group-containing monomer represented by the formula: CH ₂ = CHR 1 (wherein R 1 is —OR ₂ or —CH ₂ OR ₂ (where R 2 is an alkyl group having a hydroxyl group)), and
4) Fluorine-containing copolymers derived from other monomers that do not have a crosslinkable functional group and can be copolymerized with the monomers 1), 2), and 3).

  Examples of the fluoroolefin monomer include tetrafluoroethylene, trifluoroethylene, hexafluoropropylene, and the like. Examples of the β-methyl substituted α-olefin monomer include isobutylene, 2-methyl-1-pentene, 2-methyl-1-hexene and the like. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 4-hydroxybutyl vinyl ether, and 5-hydroxypentyl. Examples include vinyl ether, 6-hydroxyhexyl vinyl ether, 2-hydroxyethyl allyl ether, 4-hydroxybutyl allyl ether, and the like.

  Examples of other monomers that can be copolymerized with the fluoroolefin monomer, the β-methyl-substituted α-olefin monomer, and the hydroxyl group-containing monomer include vinyl acetate, vinyl propionate, (iso ) Carboxylic acid vinyl esters such as vinyl butyrate, vinyl caproate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl xafluoropropionate, vinyl trifluoroacetate, maleic acid or dimethyl fumarate, diethyl, dipropyl, dibutyl, Alkyl vinyl such as diester of maleic acid or fumaric acid such as ditrifluoromethyl, ditrifluoromethyl, dihexafluoropropyl, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, iso-butyl vinyl ether, tert-butyl vinyl ether In addition to ruethers, cycloalkyl vinyl ethers such as cyclopentyl vinyl ether and cyclohexyl vinyl ether, vinyl ethers having aromatic groups such as benzyl vinyl ether, or fluoroalkyl vinyl ethers such as perfluoroethyl vinyl ether and perfluoropropyl vinyl ether, etc. Vinyl acetate, maleic acid, styrene and the like.

  The fluorine-containing copolymer having a hydroxyl group can be obtained by copolymerizing the monomers of the above formulas 1) to 4) by a known method such as emulsion polymerization, solution polymerization, suspension polymerization or the like. The fluorine-containing copolymer having a hydroxyl group has a number average molecular weight measured by GPC of 1,000 to 500,000, preferably 3,000 to 100,000.

  As the curing agent, an organic polyisocyanate compound having high reactivity with a hydroxyl group as a crosslinking site is suitable, for example, 2,4-tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, xylylene diisocyanate. , Isophorone diisocyanate, lysine methyl ester diisocyanate, methylcyclohexyl diisocyanate, trimethylhexamethylene diisocyanate, hexamethylene diisocyanate, n-pentane-1,4-diisocyanate, and trimers thereof, adducts and burettes thereof, or Examples of these polymers include those having two or more isocyanate groups, and blocked isocyanates.

  Such a fluorine-containing copolymer containing a hydroxyl group is reacted with a curing agent to form a fluorine resin. For example, the fluorine-containing copolymer is dissolved in a solvent, and 0.3 equivalents or more, preferably 0.5 to 2.0 equivalents, based on 1 equivalent of a hydroxyl group (—OH group) in the fluorine-containing copolymer. It is appropriate to add the curing agent. When it is less than 0.3 equivalent, the laminate strength cannot be obtained, and when it exceeds 2.0 equivalent, a large amount of unreacted isocyanate groups may remain and the laminate strength may be lowered.

  Next, the heat seal layer 14 will be described. As the heat seal layer 14, a metal terminal connected to each of the positive electrode and the negative electrode of the lithium battery body is sandwiched in a state of protruding outward, and is thermally bonded to be sealed between the heat seal layer 14 and the metal terminal. The resin type differs depending on whether or not the metal terminal sealing adhesive film is interposed. 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, the graph is modified with unsaturated carboxylic acid. A film made of the acid-modified olefin resin may be used.

  Polypropylene is preferably used as the heat seal layer 14, but a single layer or a single layer or a multilayer of linear low density polyethylene or medium density polyethylene, or a blend resin of linear low density polyethylene or medium density polyethylene, or It can also be used as a multilayer film.

  For each type of polypropylene, that is, random propylene, homopropylene, block propylene, and linear low density polyethylene, medium density polyethylene, low crystalline ethylene-butene copolymer, low crystalline propylene-butene copolymer, A terpolymer composed of a three-component copolymer of ethylene, butene, and propylene, silica, zeolite, an antiblocking agent (AB agent) such as acrylic resin beads, a fatty acid amide slip agent, and the like may be added.

  In addition, it is particularly desirable that the multilayer polypropylene layer contains an ethylene / propylene random copolymer having excellent toughness in the lamination. 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 exterior body is bent after heat sealing, the occurrence of cracks in the heat sealing 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 using an unstretched polypropylene layer having a melting point of 140 to 180 ° C., as described above, in the lithium ion battery, the temperature inside the outer package 10 rises due to overcharge or the like, and the metal terminal generates heat. Even when the sandwiched portion of the metal terminal 4 of the melt-extruded polypropylene layer 9 which is the innermost layer is melted, it is possible to prevent the metal terminal and the metal foil from contacting and short-circuiting.

  Next, the melt-extruded polypropylene layer 9 will be described. By additionally processing the polypropylene layer 9 melt-extruded on the surface of the unstretched polypropylene layer that is the heat seal layer of the outer package 10, 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 unstretched polypropylene layer 16 when heated.

  Usually, when the unstretched polypropylene layer 16 is heat-sealed, it is necessary to apply heat and pressure near the melting point (about 190 ° C.) of the unstretched polypropylene layer to the seal portion. However, by providing the melt-extruded polypropylene layer 9 having a melting point of 120 to 150 ° C. on the surface of the unstretched polypropylene layer, heat sealing can be performed at a temperature lower than the melting point of the unstretched polypropylene layer.

  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 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.

  When the laminate 10 is embossed, the melt-extruded polypropylene layer 9 has a lower coefficient of dynamic friction than the unstretched propylene film. It is possible to prevent the occurrence of wrinkles and tears and to perform stable press molding.

  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 fluororesin layer or silicone resin layer slip agent 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 7),

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 8) 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 9) and (Chemical Formula 10):

Here, m, n, n ′, and l are integers of 1 or more, M ₁ is a macromonomer represented by the following formulas (Chemical Formula 11) and (Chemical Formula 12),

Here, M ₂ is a vinyl monomer copolymerizable with M _1. If R is exemplified, it is represented by the following formula (Chemical Formula 13).

などがある。

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, atropaic 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 In addition, vinyl monomers having a hydrolyzable silyl group include γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacrylo Shi 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 is highly compatible with other synthetic resins and is extremely effective as a compatibilizing agent. For example, silicone resin, polyvinyl acetoacetal, polyvinyl butyral 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 ² . a 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 battery packaging material of the present invention will be specifically described in Examples.

  One side of an aluminum foil (thickness 40 μm) having a chemical conversion treatment layer formed on both sides by chemical conversion treatment on both sides with a chemical conversion treatment solution containing an aminated phenol polymer, a chromium trioxide compound, a phosphorus compound, and a carbodiimide resin And a 25 μm thick biaxially stretched nylon film (base material layer) were laminated via a two-component curable polyurethane adhesive.

Next, an adhesive solution in which 1.1 equivalents of IPDI nurate and IPDI are added to 1 equivalent of a hydroxyl group (—OH group) of a fluorine-based polyol is dried on the other chemical conversion layer surface, and then the adhesive layer is dried. As a result, it was applied and dried to 3.0 g / m ² and an unstretched polypropylene layer having a thickness of 30 μm was heated and compressed on the surface of the adhesive layer to obtain a laminate. (Dry lamination method)

  Next, a polypropylene layer having a melting point of 139 ° C. and a melt index of 20 g / 10 min was melt-extruded to a thickness of 20 μm on the surface of the unstretched polypropylene layer of the laminate to obtain a laminate of the present invention 1.

  Further, the laminate of the present invention 2 is obtained by melt-extruding polypropylene having a melting point of 139 ° C. and a melt index of 20 g / 10 min to a thickness of 50 μm on the surface of the unstretched polypropylene layer of the laminate obtained in the same manner as described above. It was.

  Moreover, the laminated body before carrying out melt extrusion of the polypropylene on the surface of the said unstretched polypropylene layer was made into the comparative example.

  The laminates of the present invention 1, the present invention 2, and the comparative example obtained above were evaluated by the following evaluation methods, and the relationship between the seal temperature, the seal strength, and the amount of crushing was summarized in graphs 1 and 2. Further, the relationship between the sealing time, the sealing strength, and the amount of crushing is summarized in graphs 3 and 4.

[Graph 1]

[Graph 2]

[Graph 3]

[Graph 4]

  As an evaluation method for showing the relationship between the seal temperature and the seal strength, the laminate thus produced is cut into strips of 60 mm (MD direction) × 120 mm (TD direction), folded in half in the TD direction, and facing 2 The side was heat-sealed with a width of 7 mm to produce a bag having an opening on one side, and the opening was heat-sealed with a width of 7 mm, a surface pressure of 1.0 MPa, and a sealing time of 3.0 seconds. At this time, samples sealed under different conditions such as 150 ° C., 170 ° C., 190 ° C., and 210 ° C. were produced for each of the laminates.

  Next, the heat seal part at the opening of these samples was cut into a strip of 15 mm width, and this was pulled at a rate of 300 mm / min with a pulling machine (manufactured by Shimadzu Corporation, AGS-50D (trade name)), and heat seal strength Was measured. The unit is N / 15 mm width.

  As an evaluation method showing the relationship between the sealing temperature and the amount of crushing, a bag having an opening is prepared in the same manner as the above method, the opening is 7 mm wide, the surface pressure is 1.0 MPa, and the sealing time is 3.0 seconds. did. At this time, samples sealed under different conditions such as 150 ° C., 170 ° C., 190 ° C., and 210 ° C. were produced for each of the laminates. Next, the total thickness of the laminated body in the opening part before heat sealing of these samples and after heat sealing was measured.

  As an evaluation method showing the relationship between the sealing time and the sealing strength, a bag having an opening was prepared in the same manner as described above, and the opening was heat sealed at a width of 7 mm, a surface pressure of 1.0 MPa, and a sealing temperature of 190 ° C. At this time, a sample was prepared for each of the above laminates by changing the sealing time under the above conditions to 3 seconds, 6 seconds, and 9 seconds.

  Next, the heat seal part at the opening of these samples was cut into a strip of 15 mm width, and this was pulled at a rate of 300 mm / min with a pulling machine (manufactured by Shimadzu Corporation, AGS-50D (trade name)), and heat seal strength Was measured. The unit is N / 15 mm width.

  As an evaluation method showing the relationship between the sealing time and the amount of crushing, a bag having an opening was prepared in the same manner as described above, and the opening was heat sealed at a width of 7 mm, a surface pressure of 1.0 MPa, and a sealing temperature of 190 ° C. At this time, a sample was prepared for each of the above laminates by changing the sealing time under the above conditions to 3 seconds, 6 seconds, and 9 seconds. Next, each total thickness in the opening part before heat sealing of these samples and after heat sealing was measured.

  As can be seen from the graph 1, it was found that the sealing strength is improved by providing the melt-extruded polypropylene layer on the surface of the unstretched polypropylene layer. Further, the present invention 1 and the present invention 2 were compared, and it was found that the adhesive strength was improved by increasing the thickness of the polypropylene layer to be melt-extruded. From these facts, it was found that even when the sealing temperature was lowered, sufficient sealing strength could be ensured by melt extrusion of the polypropylene layer.

  Further, as is apparent from graph 2, it was found that the collapse amount of the laminate during heat sealing increases by providing a melt-extruded polypropylene layer on the surface of the unstretched polypropylene layer. By comparing with the amount of crushing in Comparative Example 1, it can be seen that this is mainly due to the crushing of the melt-extruded polypropylene layer. Therefore, by the fluidity of the melt-extruded polypropylene layer, it can be hermetically sealed so as to cover the entire metal terminal sandwiched portion, shuts off external water vapor that permeates from the metal terminal sandwiched portion, and reacts with the reaction between the electrolyte and water vapor. It is thought to suppress the production of hydrofluoric acid.

  Further, as is apparent from graphs 3 and 4, it was found that by increasing the sealing time, the amount of crushing increases, but the sealing strength does not change so much. Therefore, in order to reinforce the sealing strength, it is considered that it is more effective to provide a melt-extruded polypropylene layer rather than lengthening the sealing time. Further, when the sealing time is lengthened, not only the melt-extruded polypropylene layer but also the unstretched polypropylene layer may be crushed, and the metal terminal and the aluminum foil may be thinned to cause a short circuit. For this reason, it is considered that the sealing time is most preferably about 3 seconds.

  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.

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 Fluorine-based resin layer 9 Melt extruded polypropylene layer 10 Exterior body 10a Near 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)
DESCRIPTION OF SYMBOLS 14 Heat seal layer 15 Adhesive layer 16 Unstretched polypropylene layer 19 Plastic case 20 Press molding part 21 Male part 22 Female type | mold 22a Side wall part 23 Cavity 24 2nd polypropylene layer 25 1st polypropylene layer

Claims (9)

In the battery packaging material in which the base material layer that is the outermost layer, the barrier layer made of aluminum foil, the chemical conversion treatment layer, the fluorine resin layer, and the heat seal layer that is the innermost layer are sequentially laminated,
The heat seal layer has at least a first polypropylene layer and a second polypropylene layer,
The second polypropylene layer is disposed on the innermost layer side from the first polypropylene layer,
A battery packaging material having a lower melting point and a higher melt index than the first polypropylene layer. The fluorine-based resin layer is an adhesive comprising a fluorine-containing copolymer containing a hydroxyl group and a curing agent that reacts with the hydroxyl group of the fluorine-containing copolymer;
The first polypropylene layer comprises an unstretched polypropylene layer;
The battery packaging material according to claim 1, wherein the second polypropylene layer is a melt-extruded polypropylene layer.   The battery packaging material according to claim 2, wherein the melt-extruded polypropylene layer has a melt index of 5 g / 10 min to 30 g / 10 min.   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 chemical conversion treatment layer according to any one of claims 1 to 4, wherein the chemical conversion treatment layer is formed of a chemical conversion treatment solution containing an aminated phenol polymer, a trivalent chromium compound, a phosphorus compound, and a carbodiimide. The packaging material for a battery as described.   6. The battery packaging material according to claim 2, wherein the unstretched polypropylene layer has a melting point of 140 ° C. or higher and 180 ° C. or lower.   The battery packaging material according to any one of claims 2 to 6, wherein the unstretched polypropylene layer is a layer containing an ethylene / propylene random copolymer layer.   The battery packaging material according to any one of claims 1 to 7, wherein the substrate layer surface is a stretched polyester layer or a polybutylene terephthalate layer.   The battery packaging material according to any one of claims 1 to 8, wherein a coating layer made of a slip agent is provided on the surface of the base material layer.

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