JP2012234816A - Cell pouch having explosion safety and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cell pouch suppressing an explosion risk by releasing heat and pressure generated from a cell to an outside to be removed, and a method for manufacturing the cell pouch.SOLUTION: There are provided: a cell pouch including a gas barrier layer and a sealant layer which includes a sealing resin and a thermal expansion microcapsule expanding due to heat to form a pore; and a method for manufacturing the cell pouch. In the cell pouch, heat, pressure and the like generated from a cell are released to an outside through the pore formed due to the thermal expansion of the microcapsule, so that an explosion risk can be suppressed.

Description

  The present invention relates to a cell pouch and a method for manufacturing the same, and more specifically, when there is an explosion risk due to heat or pressure, the heat or pressure is released from the pores formed in the sealant layer to the outside. The present invention relates to a safety pouch and a method for manufacturing the same.

Generally, a battery such as a lithium ion secondary battery is built in a metal can. The metal can is mainly made of aluminum (Al) and has a cylindrical shape or a rectangular shape (a rectangular parallelepiped or the like) by press working.
However, since the outer wall of the metal can is hard, there is a restriction that the shape of the cell itself is determined by the shape of the metal can. Flexible cell pouches have been developed and used to overcome such limitations. In general, a cell pouch is manufactured in a multilayer structure in consideration of gas barrier properties (gas barrier properties), electrolyte solution resistance, and the like.

FIG. 1 is a diagram showing a cross-sectional configuration (laminated structure) of a cell pouch according to the prior art.
Referring to FIG. 1, generally, the cell pouch P includes a gas barrier layer 1 and a sealant layer 2. Moreover, the surface protective layer 3 may further be included as the outermost layer formed on the gas barrier layer 1.
The gas barrier layer 1 is for blocking gas in and out, and is mainly composed of an aluminum thin film (Al foil). The sealant layer 2 is located in the innermost layer and contacts the contents, that is, the cells. The surface protective layer 3 is mainly made of nylon resin in consideration of wear resistance and heat resistance.
The cell pouch P is formed by processing a film having a laminated structure as described above into a bag shape, and is incorporated after cell components such as an anode, a cathode, and a separator are impregnated in an electrolytic solution. After the cell components are incorporated in this manner, as shown in FIG. 1, the sealant layers 2 are thermally bonded (heat sealed) at the entrance of the cell pouch P and sealed. At this time, the sealant layer 2 must have an insulating property and an electrolytic solution resistance in order to come into contact with the cell components, and must have a high sealing property for sealing with the outside. In other words, the sealing portion where the sealant layers (2) are thermally bonded must have excellent thermal bonding strength (sealing property). Generally, the sealant layer 2 is made of a polyolefin resin such as polypropylene (PP) or polyethylene (PE). In particular, polypropylene (PP) is excellent in mechanical properties such as tensile strength, rigidity, surface hardness, impact strength, and electrolytic solution resistance, and is mainly used for the sealant layer 2 of the serpouch P.

However, the self-pouch P according to the prior art has a problem that there is no safety in relation to the explosion risk. Generally, in a cell, heat and pressure are generated in the process of generating / releasing (charging / discharging) electricity (oxidation-reduction reaction, etc.). At this time, the reason for overcharge or short due to abnormal reaction inside the cell May generate high heat and pressure. Such a high heat and pressure may cause explosion of the cell pouch P. However, the conventional cell pouch P has no technical means to suppress the explosion risk, and is exposed to the explosion risk. There is a problem.
Further, the cell pouch P according to the prior art has a problem that the thermal adhesive strength (sealing property) of the sealant layer 2 is not good and the interlayer adhesion is weak. In particular, the gas barrier layer 1 is made of a metal such as Al, but there is a problem that the interlayer adhesion between the gas barrier layer 1 and the sealant layer 2 of the metal is weak.

Korean Patent Application Publication No. 2009-0076280

  Therefore, the present invention is for solving the above-mentioned problems of the prior art, and by expelling and removing the heat and pressure generated from the cell to the outside, there is a risk of explosion due to heat and pressure. It is providing the self-pouch which suppressed the property, and its manufacturing method. Moreover, this invention is excellent in the heat bond strength (sealing property) of a sealant layer, and is providing the cell pouch which the interlayer adhesive force improved, and its manufacturing method.

The present invention relates to a cell pouch including a gas barrier layer and a sealant layer, wherein the sealant layer includes a sealing resin and a thermally expandable microcapsule that expands by heat to form pores.
At this time, it is preferable that the sealant layer further includes one or more resins selected from the group consisting of modified polyethylene, modified polypropylene, acrylic resin, and modified acrylic resin.

  The present invention also includes a step of forming a sealant layer on the gas barrier layer, and the step of forming the sealant layer is formed by extruding a sealant composition on the gas barrier layer, and the sealant composition is formed of a sealing resin. The present invention also relates to a method of manufacturing a ser pouch including thermally expandable microcapsules that expand by heat to form pores.

According to the present invention, the heat, pressure, and the like generated from the cell are removed from the pores formed by the thermal expansion of the microcapsules to the outside, and the explosion risk is suppressed.
Further, according to the present invention, the sealant layer has an excellent thermal adhesive strength (sealing property), and the interlayer adhesion between the gas barrier layer and the sealant layer is improved.

FIG. 1 is a cross-sectional view of a conventional cell pouch. FIG. 2 is a cross-sectional configuration diagram of the cell pouch according to the first embodiment of the present invention. FIG. 3 is a cut perspective view of a thermally expandable microcapsule used in an embodiment of the present invention. FIG. 4 is a schematic diagram showing the thermal expansion mechanism of the thermally expandable microcapsule used in the embodiment of the present invention. FIG. 5 is a cross-sectional configuration diagram of a cell pouch according to the second embodiment of the present invention. FIG. 6 is a cross-sectional configuration diagram of a cell pouch according to a third embodiment of the present invention. FIG. 7 is an electron micrograph before and after expansion of the thermally expandable microcapsule used in the example of the present invention. FIG. 8 is a graph showing the expansion ratio (times) at each temperature of the cell pouch manufactured according to the embodiment of the present invention, and a cross-sectional photograph and a surface photograph at each temperature.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
First, referring to FIG. 2, the cell pouch according to the first embodiment of the present invention includes a gas barrier layer 10 and a sealant layer 20. The sealant layer 20 may be formed on one side or both sides of the gas barrier layer 10. At this time, the sealant layer 20 may be formed in contact with the gas barrier layer 10 or may be formed with another layer interposed therebetween. For example, an intermediate layer 40 (see FIG. 6) may be further formed between the gas barrier layer 10 and the sealant layer 20.

The cell pouch according to the present invention includes a gas barrier layer 10 and a sealant layer 20 and has a multilayer structure of at least two layers. Further, the cell pouch according to the embodiment of the present invention may further include other layers in addition to the gas barrier layer 10 and the sealant layer 20. For example, as illustrated in FIG. 2, a resin layer 30 formed on the gas barrier layer 10 may be further included.
In addition, as illustrated in FIG. 6, an intermediate layer 40 formed between the gas barrier layer 10 and the sealant layer 20 may be further included.
FIG. 2 shows a laminated structure in which the sealant layer 20, the gas barrier layer 10, and the resin layer 30 are sequentially formed from the bottom according to the first embodiment of the present invention. The laminated structure shown in FIG. 2 can be used, for example, as an application that incorporates a small battery or the like.

  The gas barrier layer 10 is not particularly limited as long as it has gas barrier properties. Specifically, the gas barrier layer 10 only needs to be capable of blocking the entry and exit of external moisture, air, and gas generated inside. The gas barrier layer 10 only needs to include one or more selected from a gas-impermeable plastic film, a metal thin film, a vapor deposition layer, and the like. At this time, the metal thin film may be a metal foil having a thickness of 1 μm to 300 μm, for example, and may be bonded to the sealant layer 20 via an adhesive. The deposited layer is formed by depositing one or more selected from metals and metal oxides. The deposited layer is formed by vacuum deposition on the sealant layer 20 or separately. It may be formed by vacuum deposition on a plastic film such as polyethylene terephthalate (PET), polyethylene (PE) or polypropylene (PP). Furthermore, the vapor deposition layer may have a thickness of 1 nm to 300 μm, for example.

In the embodiment of the present invention, the metal applied to the gas barrier layer 10, specifically the metal constituting the metal thin film or the vapor deposition layer, for example, aluminum (Al), copper (Cu), nickel (Ni), One or more selected from the group consisting of tin (Sn), zinc (Zn), indium (In), silver (Ag), tungsten (W), iron (Fe), etc. (single metal or single metal Or a mixture of two or more alloys selected from these, but is not necessarily limited thereto. The metal is preferably selected from aluminum (Al) or an aluminum alloy. Examples of the metal oxide that can be used for the vapor deposition layer include aluminum oxide (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), tin oxide (SnO ₂ ), indium oxide (In ₂ O ₃ ), and zinc oxide. Any material selected from (ZnO) and the like may be used.

The sealant layer 20 is sealed (heat-sealed) by heat after the cells are embedded (wrapped) to give a sealing property, which is a sealing resin according to the present invention. Includes thermally expandable microcapsules 25. At this time, the sealing resin provides thermal adhesiveness (sealing property), and the thermally expandable microcapsule 25 suppresses the risk of explosion due to heat or pressure generated from the cell.
The sealing resin can be melted and sealed by heat to give thermal adhesiveness (sealability), and is not particularly limited as long as it is an insulating resin. The sealing resin is preferably selected from low melting point resins that can be heat-sealed at low temperatures. The sealing resin may be, for example, a resin that is melted at 300 ° C. or less, preferably 270 ° C. or less, more specifically 120 to 270 ° C. and can be heat sealed. More specific examples of the sealing resin include one or more selected from polyolefins such as polypropylene (PP) and polyethylene (PE) and their derivatives, and ethylene vinyl acetate (EVA). Can be used. As another example of the sealing resin, a terpolymer (ter-polymer) such as a terpolymer of ethylene / propylene / butadiene having a low melting point and excellent sealing properties can be used. Use it.

The sealing resin preferably includes a polypropylene (PP) system, and specific examples thereof include homopolypropylene (homo PP), polypropylene copolymer (PP co-polymer), and polypropylene. Any material containing at least one polypropylene (PP) system selected from terpolymer (PP ter-polymer) and the like may be used. The polypropylene (PP) system has excellent sealing properties and insulating properties, and has excellent mechanical properties such as tensile strength, rigidity, and surface hardness, and chemical resistance such as electrolytic solution resistance. It can be usefully used in the invention.
The thermally expandable microcapsule 25 is for suppressing the risk of explosion, and is expanded by heat to form pores. Specifically, when the heat-expandable microcapsule 25 generates excessive heat or pressure more than necessary from the cell, the heat-expandable microcapsule 25 expands in volume due to heat and forms fine pores. At this time, the fine pores are formed in the sealant layer 20, more specifically, at a sealing portion that is thermally bonded to the sealant layers 20, that is, at the adhesion interface between the sealant layers 20. Danger of explosion due to absorption of heat, pressure, gas, etc. causing explosion, especially heat, pressure, gas etc. released from fine pores formed at the adhesive interface between sealant layers 20 Is suppressed.

FIG. 3 is a cut perspective view showing an example of the thermally expandable microcapsule 25 used in the present invention, and FIG. 4 shows the heat expansion mechanism of the thermally expandable microcapsule 25 used in the present invention. ).
The thermally expandable microcapsule 25 is not particularly limited as long as it can expand its volume and form pores by heat generated from the cell. The thermally expandable microcapsule 25 may have a circular or oval cross section, but is not limited thereto. 3 and 4 illustrate a thermally expandable microcapsule 25 having a circular cross section.
Referring to FIGS. 3 and 4, the thermally expandable microcapsule 25 is in the form of a capsule in which a thermally expandable material is collected, which is specifically a shell 25a as an outer membrane. And a core 25b formed inside the shell 25a, and a thermally expansible material is collected (filled) in the core 25b. At this time, the thermally expansible material may be any material that expands by heat and applies pressure to the shell 25a, and is preferably selected from hydrocarbons and the like. The hydrocarbon includes liquid and / or gas, and is preferably selected from liquefied hydrocarbons. Further, the shell 25a may be made of at least one selected from, for example, acrylic resin, polyurethane, polyethylene, and polypropylene as the thermoplastic polymer. As the shell 25a, a shell having a melting point different from that of the sealing resin may be used. Preferably, the shell 25a may be selected from those having a melting point higher than that of the sealing resin.

The shell 25a may have a thickness T _{25a of} 0.01 to 50 μm. At this time, if it is less than the thickness T _25a of the shell 25a is 0.01 [mu] m, there is a possibility that the shell 25a during sealing is broken, the thermal expansion properties weaker for porosity generation rate is insignificant if it exceeds 50μm It can be a thing. Such points in mind, the shell 25a preferably has a thickness T _25a of 0.2 to 10 [mu] m, more preferably, it may have a 1~5μm thickness T _25a.
Further, the thermally expandable microcapsule 25 may have a size (outer diameter) of, for example, 0.1 to 200 μm. At this time, if the size T _{25 of} the thermally expandable microcapsule 25 is less than 0.1 μm, that is, if the outer diameter is too small, the size of the pores formed by thermal expansion is reduced, and the heat and pressure are reduced. Absorption and removal efficiency may be insignificant, and if it exceeds 200 μm and the size T ₂₅ is too large, the sealability (thermal adhesive strength) of the sealant layer 20 may be lowered. In consideration of such points, the size T _{25 of the} thermally expandable microcapsule ₂₅ , that is, the outer diameter is preferably 0.5 to 100 μm, and more preferably 2 to 50 μm.

In an exemplary embodiment, the thermally expandable microcapsule 25 has a particle size at 130 to 180 ° C. based on the particle size at normal temperature (25 ° C.) when considering the explosion stability of the secondary battery. Is preferably 1 to 5 times, and the particle size at 140 to 180 ° C. is preferably 2 to 5 times.
Further, as illustrated in FIG. 4, the thermally expandable microcapsule 25 expands to the maximum due to heat and then shrinks in volume due to breakage of the shell 25 a when further subjected to heat. Can be used. What is necessary is just to use what is marketed for the said thermally expansible microcapsule 25, for example, F-series products (F-36, F-48, F-50 made by Matsumoto Yushi Seiyaku Co., Ltd. in Japan). And F-85), M-series products (MS131, MS161, etc.) manufactured by Dongjin Semichem Co., Ltd. of Korea may be used.

  In an embodiment of the present invention, the sealant layer 20 includes the sealing resin and the thermally expandable microcapsule 25 as described above, and 1 to 40 weights of the thermally expandable microcapsule 25 with respect to 100 parts by weight of the sealing resin. Part is preferable. When the content of the heat-expandable microcapsules 25 is less than 1 part by weight, the pore generation rate is small, so that the heat and pressure absorption and removal efficiency may be insignificant. Moreover, when the content of the thermally expandable microcapsule 25 exceeds 40 parts by weight and becomes excessive, the thermal adhesive strength (sealing property) is lowered due to the relatively small content of the sealing resin, and the viscosity is increased. As a result, the processability (coating property, extrusion property, etc.) of the sealant layer 20 may deteriorate. The sealant layer 20 preferably includes 5 to 20 parts by weight of the thermally expandable microcapsule 25 with respect to 100 parts by weight of the sealing resin.

The sealant layer 20 may further contain other functional components in addition to the sealing resin and the thermally expandable microcapsule 25. The sealant layer 20 has, for example, a component capable of increasing thermal bond strength (sealing property); a component capable of increasing chemical resistance (electrolytic solution resistance); and an interlayer adhesion with the gas barrier layer 10. It may further include one or more selected from components that can be increased.
The sealant layer 20 is preferably a group consisting of a modified polyethylene (modified PE), a modified polypropylene (modified PP), an acrylic resin (such as acrylate), a modified acrylic resin (such as a modified acrylate), an epoxy resin, and a phenol resin. It may further contain one or more selected adhesive resins. The above-mentioned adhesive resin is included in the sealant layer 20 to increase thermal adhesive strength (sealing property), chemical resistance (electrolytic solution resistance, etc.) and / or interlayer adhesion with the gas barrier layer 10. . For example, in the case of the acrylic resin (or modified acrylic resin), the thermal adhesive strength and the interlayer adhesion can be increased, and in the case of the modified PE and modified PP, the interlayer adhesion and chemical resistance can be increased. Further, the above-mentioned adhesive resin has good compatibility with a sealing resin (particularly, a polyolefin type such as a polypropylene type). At this time, the modified resin in the above-mentioned adhesive resin is obtained by polymerizing (for example, grafting) an unsaturated carboxylic acid (and / or a derivative thereof) or a vinyl monomer on a base resin (PE, PP or acrylic resin). Polymerized) and modified, and may preferably be selected from those having a melting point lower than that of the sealing resin. Furthermore, the sealant layer 20 may include 0.1 to 40 parts by weight of the above-described adhesive resin with respect to 100 parts by weight of the sealing resin.

In addition, the above-mentioned adhesive resin may be included in a separate layer in the cell pouch according to the embodiment of the present invention. For example, the above-mentioned adhesive resin is formed as a separate layer between the gas barrier layer 10 and the sealant layer 20 to improve the interlayer adhesion between the gas barrier layer 10 and the sealant layer 20, It can be formed on the surface 20 (the lower surface in FIG. 2) to improve the thermal bonding strength (sealing property) and chemical resistance.
As described above, the resin layer 30 may be further formed on the gas barrier layer 10, but at this time, the resin layer 30 may be anything that can protect the gas barrier layer 10, For example, a resin having characteristics such as heat resistance, cold resistance, pinhole resistance, insulation, and / or solvent resistance may be included. Specifically, the resin layer 30 may include one or more resins selected from nylon resin, polyethylene terephthalate (PET), polyolefin (PE, PE, etc.), and the like. The resin layer 30 is formed by coating (or extruding) a composition containing the resin as mentioned above on the gas barrier layer 10, or a film containing the resin as mentioned above is formed on the gas barrier layer 10. One layer or two or more layers may be bonded (adhered) to each other.

  The resin layer 30 may preferably include one or more selected from nylon resin and polyethylene terephthalate (PET). For example, the resin layer 30 may be composed of a nylon resin layer, a polyethylene terephthalate (PET) layer, or a composite layer thereof. At this time, the resin layer 30 may be formed on the gas barrier layer 10 by coating or coextrusion. Further, a separate adhesive layer for the interlayer adhesion may be formed between the resin layer 30 and the gas barrier layer 10.

FIG. 5 is a diagram showing a cross-sectional configuration of the cell pouch according to the second embodiment of the present invention. Referring to FIG. 5, a cell pouch according to an embodiment of the present invention includes a sealant layer 20, a gas barrier layer 10 formed on the sealant layer 20, and a resin layer 30 formed on the gas barrier layer 10. The resin layer 30 may have a multilayer structure of two or more layers.
For example, the resin layer 30 includes a first resin layer 31 formed on the gas barrier layer 10 as shown in FIG. 5 and a second resin as the outermost layer formed on the first resin layer 31. Layer 32 may be included. At this time, according to a preferred embodiment, the first resin layer 31 includes a nylon resin, and the second resin layer 32 is selected from polyethylene terephthalate (PET) and polyolefin (PE, PE, etc.). One or more resins may be included. More specifically, the first resin layer 31 may be composed of a nylon resin layer, and the second resin layer 32 may be composed of a polyethylene terephthalate (PET) layer. The laminated structure shown in FIG. 5 can be used, for example, for a purpose of incorporating a medium-sized battery or a large battery.

  FIG. 6 is a diagram showing a cross-sectional configuration of a cell pouch according to the third embodiment of the present invention. As shown in FIG. 6, the cell pouch according to the embodiment of the present invention may further include an intermediate layer 40 formed between the gas barrier layer 10 and the sealant layer 20. As a specific example, as shown in FIG. 6, the sealant layer 20, the intermediate layer 40 formed on the sealant layer 20, the gas barrier layer 10 formed on the intermediate layer 40, and the gas barrier layer 10 are formed. The laminated resin layer 30 may be included. Further, according to another embodiment, the intermediate layer 40 may be formed between the gas barrier layer 10 and the resin layer 30.

  The intermediate layer 40 may include, for example, a resin having characteristics such as insulation, heat resistance, cold resistance, and / or chemical resistance (electrolytic solution resistance, etc.). Preferably, the intermediate layer 40 may include a resin that can enhance the adhesion between the gas barrier layer 10 and the sealant layer 20. As a specific example, the intermediate layer 40 includes one or more selected from nylon resin, polyethylene terephthalate (PET), polyolefin resin, modified polyolefin resin, acrylic resin, modified acrylic resin, and epoxy resin. May be. Examples of the polyolefin resin include polyethylene (PE) and polypropylene (PP), and the modified polyolefin resin includes modified polyethylene (modified PE) and modified polypropylene (modified PP), which are as described above. At this time, among the resins listed above, nylon resin, polyethylene terephthalate (PET), polyolefin (PE, PP, etc.) are advantageous for insulation, heat resistance, cold resistance, and / or chemical resistance, etc. The modified polyolefin (modified PE, modified PP, etc.), acrylic resin, modified acrylic resin, epoxy resin, etc. are usefully used for improving the chemical resistance, particularly the interlayer adhesion between the gas barrier layer 10 and the sealant layer 20. it can.

  On the other hand, the cell pouch according to the embodiment of the present invention has a multilayer structure as described above, and each layer is not particularly limited, but may be manufactured by co-extrusion. Specifically, the sealant layer 20 may be formed by coextrusion on the gas barrier layer 10. At this time, the sealant layer 20 has an adhesive resin (modified PE) as mentioned above in addition to the sealing resin and the thermally expandable microcapsule 25 so as to be excellent in interlayer adhesion with the gas barrier layer 10. , Modified PP, acrylic resin, modified acrylic resin, epoxy resin, phenol resin, and the like) may be formed by coextrusion. Further, the resin layer 30 and the intermediate layer 40 may be coextruded on the gas barrier layer 10.

  One or more selected from the sealant layer 20, the resin layer 30, and the intermediate layer 40 may further contain an additive in addition to the base resin constituting them. Examples of the additive include one or more selected from an antifogging agent, a slip agent, and an antiblocking agent. An additive in particular is not restrict | limited, In addition to the additive mentioned above, you may be selected from what is normally used in this industry, and another functional component. Such an additive is, for example, 0.01 to 20 parts by weight, more specifically 0.05 to 10 parts by weight with respect to 100 parts by weight of the base resin constituting each of the layers 20, 30 and 40. It may be.

  The anti-fogging agent prevents moisture in the air from condensing on the surface of each of the layers 20, 30, and 40, and may be selected from, for example, surfactants. Specific examples of the antifogging agent include sorbitan fatty acid esters such as sorbitan monooleate, sorbitan monolaurate, sorbitan monobehenate, and sorbitan monostearate; glycerin fatty acid esters such as glyceryl monooleate and glyceryl monostearate; lauryl Examples include aliphatic amines such as diethanolamine; fatty acid amides such as oleic acid amide. Such an antifogging agent is not particularly limited, but is 0.01 to 10 parts by weight with respect to 100 parts by weight of the base resin constituting each layer 20, 30, 40. It may be contained in 1 to 5 parts by weight.

  The slip agent can give slip property (or releasability) at the time of extrusion, and this is one or more selected from, for example, silicon, siloxane, silane, wax system and oleic amide. May be used. The slip agent can be used without any particular limitation, as long as it can give lubricity to the surface of each layer 20, 30, 40 and reduce the number of friction systems in addition to the above-mentioned ones. Although it is not a thing, 0.05-15 weight part with respect to 100 weight part of base resin which comprises each layer 20, 30, 40 may be contained, More specifically, 0.1-10 weight part may be contained.

  The anti-blocking agent is capable of preventing adhesion between serpouch films at the time of winding after extrusion, and this includes inorganic particles such as silica, diatomaceous earth, kaolin, and talc. One or more selected from the above may be used. The anti-blocking agent may be contained in the sealant layer 20 and the resin layer 30 as much as possible, and is not particularly limited. It may be contained in an amount of 05 to 15 parts by weight, more specifically 0.1 to 10 parts by weight.

  Further, in the thickness of each of the layers 10, 20, 30, 40, the gas barrier layer 10 may have a thickness of 0.1 μm to 300 μm, for example, and the sealant layer 20 may have a thickness of 0, for example. It may have a thickness of 1 μm to 500 μm. The sealant layer 20 preferably has a thickness of 3.0 μm or more, specifically 3.0 μm to 500 μm, more preferably 3.0 μm to 300 μm, for good thermal adhesive strength (sealing property). You can do it. Further, the resin layer 30 and the intermediate layer 40 are not particularly limited, but may have a thickness of, for example, 0.1 μm to 300 μm, preferably 0.5 μm to 200 μm.

  On the other hand, the method for manufacturing a cell pouch according to an embodiment of the present invention includes a step of forming a sealant layer 20 on the gas barrier layer 10, and the step of forming the sealant layer 20 extrudes a sealant composition onto the gas barrier layer 10. The method of forming is performed. At this time, the sealant composition includes the sealing resin and the thermally expandable microcapsule 25 as described above. Preferably, the sealant composition may include 1 to 40 parts by weight of the thermally expandable microcapsule 25 with respect to 100 parts by weight of the sealing resin.

  Further, the sealant composition includes the adhesive resin as described above, that is, modified polyethylene (modified PE), modified polypropylene (modified PP), acrylic resin (such as acrylate), modified acrylic resin (such as modified acrylate), and epoxy resin. And one or more adhesive resins selected from the group consisting of phenolic resins and the like. At this time, the sealant composition may include, for example, 0.1 to 40 parts by weight of the above-described adhesive resin with respect to 100 parts by weight of the sealing resin.

The sealant composition is coextruded on the gas barrier layer 10 and may be coextruded at a temperature of 350 ° C. or lower, for example. As a specific example, it may be coextruded at a temperature of 150 to 350 ° C., more specifically 200 to 300 ° C.
Hereinafter, embodiments of the present invention will be described in more detail by way of examples.

A cell pouch was produced by applying a sealant layer consisting of 100 parts by weight of a sealant resin (propylene resin) and 10 parts by weight of microcapsules on the gas barrier layer (thin aluminum). The size of the microcapsule is 20 to 30 μm, the thermal expansion material of the core of the microcapsule is hydrocarbon, and the material of the shell is acrylonitrile copolymer. The shell has a thickness of 2-5 μm.
Attached FIG. 7 is an electron micrograph of the microcapsule 25 used in the embodiment of the present invention before and after expansion (170 ° C.). Also, FIG. 8 attached herewith shows the expansion ratio (times) according to the temperature of the cell pouch manufactured according to the embodiment of the present invention. That is, FIG. 8 is a graph showing the expansion ratio (times) of the microcapsules at each temperature. Further, FIG. 8 shows a cross-sectional photograph and a surface photograph at each temperature together as an enlarged photograph of the ser pouch manufactured according to the embodiment of the present invention. As shown in the graph of FIG. 8, it can be seen that the expansion ratio increases as the temperature increases, and after the maximum expansion, the shell shrinks due to the fracture of the shell. In particular, as can be seen from the cross-sectional photograph of FIG. 8, it can be seen that micropores are formed around the microcapsules due to the expansion of the microcapsules.

The cell pouch according to the embodiment of the present invention described above is a secondary cell such as a battery, for example, a lithium ion battery as a chargeable / dischargeable secondary battery, a nickel-hydrogen battery, and an electric double layer capacitor (EDLC). Used to incorporate batteries.
In addition, as described above, the cell pouch according to the embodiment of the present invention absorbs and removes heat and pressure generated from the inside to suppress the risk of explosion. Specifically, when heat or pressure higher than necessary is generated from the cell, the thermally expandable microcapsules 25 included in the sealant layer 20 are expanded by heat to form fine pores. Specifically, fine pores are formed at a sealing portion where the sealant layers 20 are thermally bonded, that is, at an adhesive interface between the sealant layers 20. At this time, the fine pores are distributed around the thermally expanded microcapsules 25, that is, between the microcapsules 25 as shown in FIG. Then, heat, pressure, gas, and the like that cause explosion are absorbed into the inside of the fine pores, and in particular, escaped from the fine pores to be removed. As a result, the risk of explosion due to heat or pressure is reduced.
In addition, when the sealant layer 20 further includes an adhesive resin as described above, that is, modified PE, modified PP, acrylic resin, modified acrylic resin, and the like, the gas barrier layer as well as the thermal adhesive strength (sealing property) are included. The interlayer adhesion with 10 is improved.

DESCRIPTION OF SYMBOLS 10 Gas barrier layer 20 Sealant layer 30 Resin layer 31 1st resin layer 32 2nd resin layer 40 Intermediate layer

Claims (16)

Including a gas barrier layer and a sealant layer,
The sealant layer includes a sealing resin and a thermally expandable microcapsule that expands by heat to form pores.   The cell pouch according to claim 1, wherein the thermally expandable microcapsule has a size of 0.1 to 200 μm.   The cell pouch according to claim 1, wherein the sealant layer includes 1 to 40 parts by weight of thermally expandable microcapsules with respect to 100 parts by weight of the sealing resin.   The cell pouch according to claim 1, wherein the sealing resin contains polypropylene.   The sealant layer further includes one or more resins selected from the group consisting of modified polyethylene, modified polypropylene, acrylic resin and modified acrylic resin, epoxy resin, and phenol resin. The ser pouch according to any one of the above.   The cell pouch according to claim 1, wherein the cell pouch includes a sealant layer, a gas barrier layer formed on the sealant layer, and a resin layer formed on the gas barrier layer.   The cell pouch according to claim 6, wherein the resin layer includes one or more resins selected from nylon resin, polyethylene terephthalate, and polyolefin.   The cell pouch according to claim 6, wherein the resin layer includes a first resin layer formed on the gas barrier layer and a second resin layer formed on the first resin layer.   The cell pouch according to claim 8, wherein the first resin layer includes a nylon resin, and the second resin layer includes one or more resins selected from polyethylene terephthalate and polyolefin.   The cell pouch according to claim 1, wherein the cell pouch further includes an intermediate layer formed between the gas barrier layer and the sealant layer.   The cell pouch according to claim 6, further comprising an intermediate layer formed between the gas barrier layer and the resin layer.   The pouch according to claim 10 or 11, wherein the intermediate layer includes one or more resins selected from a polyolefin resin, a modified polyolefin resin, an acrylic resin, a modified acrylic resin, and an epoxy resin.   2. The cell pouch according to claim 1, wherein the thermally expandable microcapsule has a particle size of 2 to 5 times at 140 to 180 ° C. based on a particle size at normal temperature. Forming a sealant layer on the gas barrier layer;
In the step of forming the sealant layer, the sealant composition is extruded onto the gas barrier layer,
The sealant composition includes a sealing resin and a thermally expandable microcapsule that expands by heat to form pores.   15. The sealant composition further includes one or more resins selected from the group consisting of modified polyethylene, modified polypropylene, acrylic resin, modified acrylic resin, epoxy resin, and phenolic resin. A method for producing a ser pouch according to claim 1.   The method for producing a cell pouch according to claim 14 or 15, wherein the sealant composition contains 1 to 40 parts by weight of thermally expandable microcapsules with respect to 100 parts by weight of the sealing resin.